the moisture vapor transmission rate as used herein is defined as the mass of moisture vapor that diffuses into a material of a given thickness per unit area per unit time . the preferred standards of measuring the moisture vapor transmission rate include astm f1249 - 90 entitled “ standard test method for water vapor transmission rate through plastic film and sheeting using a modulated infrared sensor ,” and astm f372 - 94 entitled “ standard test method for water vapor transmission rate of flexible barrier materials using an infrared detection technique ,” among others . suitable polybutadiene rubbers for blending with the base rubber may include buna ® cb22 , buna ® cb23 and buna ® cb24 , buna ® 1203g1 , 1220 , 1221 , and buna ® cbnd - 40 , commercially available from lanxess corporation ; bste br - 1220 available from bst elastomers co . ltd ; ubepol ® 360l and ubepol ® 150l and ubepol - br rubbers , commercially available from ube industries , ltd . of tokyo , japan ; budene 1207 , 1208 and 1280 , commercially available from goodyear of akron , ohio ; se br - 1220 , commercially available from dow chemical company ; europrene ® neocis ® br 40 and br 60 , commercially available from polimeri europa ; and br 01 , br 730 , br 735 , br 11 , and br 51 , commercially available from japan synthetic rubber co ., ltd ; and karbochem ® neodene 40 , 45 , and 60 , commercially available from karbochem . the base rubber may further include polyisoprene rubber , natural rubber , ethylene - propylene rubber , ethylene - propylene diene rubber , styrene - butadiene rubber , and combinations of two or more thereof another preferred base rubber is polybutadiene optionally mixed with one or more elastomers such as polyisoprene rubber , natural rubber , ethylene propylene rubber , ethylene propylene diene rubber , styrene - butadiene rubber , polystyrene elastomers , polyethylene elastomers , polyurethane elastomers , polyurea elastomers , acrylate rubbers , polyoctenamers , metallocene - catalyzed elastomers , and plastomers . as discussed further below , highly neutralized acid copolymers ( hnps ), as known in the art , also can be used to form the core layer as part of the blend . such compositions will provide increased flexural modulus and toughness thereby improving the golf ball &# 39 ; s performance including its impact durability . the base rubber typically is mixed with at least one reactive cross - linking co - agent to enhance the hardness of the rubber composition . suitable co - agents include , but are not limited to , unsaturated carboxylic acids and unsaturated vinyl compounds . a preferred unsaturated vinyl compound is trimethylolpropane trimethacrylate . the rubber composition is cured using a conventional curing process . suitable curing processes include , for example , peroxide curing , sulfur curing , high - energy radiation , and combinations thereof . in one embodiment , the base rubber is peroxide cured . organic peroxides suitable as free - radical initiators include , for example , dicumyl peroxide ; n - butyl - 4 , 4 - di ( t - butylperoxy ) valerate ; 1 , 1 - di ( t - butylperoxy ) 3 , 3 , 5 - trimethylcyclohexane ; 2 , 5 - dimethyl - 2 , 5 - di ( t - butylperoxy ) hexane ; di - t - butyl peroxide ; di - t - amyl peroxide ; t - butyl peroxide ; t - butyl cumyl peroxide ; 2 , 5 - dimethyl - 2 , 5 - di ( t - butylperoxy ) hexyne - 3 ; di ( 2 - t - butyl - peroxyisopropyl ) benzene ; dilauroyl peroxide ; dibenzoyl peroxide ; t - butyl hydroperoxide ; and combinations thereof . cross - linking agents are used to cross - link at least a portion of the polymer chains in the composition . suitable cross - linking agents include , for example , metal salts of unsaturated carboxylic acids having from 3 to 8 carbon atoms ; unsaturated vinyl compounds and polyfunctional monomers ( for example , trimethylolpropane trimethacrylate ); phenylene bismaleimide ; and combinations thereof . in a particular embodiment , the cross - linking agent is selected from zinc salts of acrylates , diacrylates , methacrylates , and dimethacrylates . in another particular embodiment , the cross - linking agent is zinc diacrylate (“ zda ”). commercially available zinc diacrylates include those selected from cray valley resource innovations inc . other elastomers known in the art may also be added , such as other polybutadiene rubbers , natural rubber , styrene butadiene rubber , and / or isoprene rubber in order to further modify the properties of the core . when a mixture of elastomers is used , the amounts of other constituents in the core composition are typically based on 100 parts by weight of the total elastomer mixture . thermoplastic elastomers ( tpe ) may also be used to modify the properties of the core layers , or the uncured core layer stock by blending with the base thermoset rubber . these tpes include natural or synthetic balata , or high trans - polyisoprene , high trans - polybutadiene , or any styrenic block copolymer , such as styrene ethylene butadiene styrene , styrene - isoprene - styrene , etc ., a metallocene or other single - site catalyzed polyolefin such as ethylene - octene , or ethylene - butene , or thermoplastic polyurethanes ( tpu ), including copolymers , e . g . with silicone . other suitable tpes for blending with the thermoset rubbers of the present invention include pebax ®, which is believed to comprise polyether amide copolymers , hytrel ®, which is believed to comprise polyether ester copolymers , thermoplastic urethane , and kraton ®, which is believed to comprise styrenic block copolymers elastomers . any of the tpes or tpus above may also contain functionality suitable for grafting , including maleic acid or maleic anhydride . any of the thermoplastic vulcanized rubbers ( tpv ) such as santoprene ® or vibram ® or etpv ® can be used along with a present invention . in one embodiment , the tpv has a thermoplastic as a continuous phase and a cross - linked rubber particulate as a dispersed ( or discontinuous ) phase . in another embodiment , the tpv has a cross - linked phase as a continuous phase and a thermoplastic as a dispersed ( or discontinuous ) phase to provide reduced loss in elasticity in order to improve the resiliency of the golf ball . the rubber compositions also may contain “ soft and fast ” agents such as a halogenated organosulfur , organic disulfide , or inorganic disulfide compounds . particularly suitable halogenated organosulfur compounds include , but are not limited to , halogenated thiophenols . preferred organic sulfur compounds include , but not limited to , pentachlorothiophenol (“ pctp ”) and a salt of pctp . a preferred salt of pctp is znpctp . a suitable pctp is sold by the struktol company ( stow , ohio ) under the tradename , a95 . znpctp is commercially available from echinachem ( san francisco , calif .). these compounds also may function as cis - to - trans catalysts to convert some cis bonds in the polybutadiene to trans bonds . antioxidants also may be added to the rubber compositions to prevent the breakdown of the elastomers . other ingredients such as accelerators ( for example , tetra methylthiuram ), processing aids , dyes and pigments , wetting agents , surfactants , plasticizers , as well as other additives known in the art may be added to the rubber composition . the core may be formed by mixing and forming the rubber composition using conventional techniques . these cores can be used to make finished golf balls by surrounding the core with outer core layer ( s ), intermediate layer ( s ), and / or cover materials as discussed further below . in another embodiment , the cores can be formed using highly neutralized polymer ( hnp ) compositions as disclosed in u . s . pat . nos . 6 , 756 , 436 , 7 , 030 , 192 , 7 , 402 , 629 , and 7 , 517 , 289 . the cores from the highly neutralized polymer compositions can be further cross - linked using any free - radical initiation sources including radiation sources such as gamma or electron beam as well as chemical sources such as peroxides and the like . golf balls made in accordance with this invention can be of any size , although the usga requires that golf balls used in competition have a diameter of at least 1 . 68 inches and a weight of no greater than 1 . 62 ounces . for play outside of usga competition , the golf balls can have smaller diameters and be heavier . in some instances , a traditional thermoplastic or thermosetting composition may be used to make one layer and the vapor barrier layer may be used to make a different layer of the golf ball depending upon the desired ball construction playing performance properties . if a conventional thermoplastic or thermosetting composition is used in one layer ( and the vapor barrier layer used in a different layer ), then a wide variety of thermoplastic or thermosetting materials can be employed . these materials include for example , olefin - based copolymer ionomer resins ( for example , surlyn ® ionomer resins and dupont ® hpf 1000 and hpf 2000 , commercially available from e . i . du pont de nemours and company ; iotek ® ionomers , commercially available from exxonmobil chemical company ; amplify ® io ionomers of ethylene acrylic acid copolymers , commercially available from the dow chemical company ; and clarix ® ionomer resins , commercially available from a . schulman inc . ); polyurethanes ; polyureas ; copolymers and hybrids of polyurethane and polyurea ; polyethylene , including , for example , low density polyethylene , linear low density polyethylene , and high density polyethylene ; polypropylene ; rubber - toughened olefin polymers ; acid copolymers , for example , poly ( meth ) acrylic acid , which do not become part of an ionomeric copolymer ; plastomers ; flexomers ; styrene / butadiene / styrene block copolymers ; styrene / ethylene - butylene / styrene block copolymers ; dynamically vulcanized elastomers ; copolymers of ethylene and vinyl acetates ; copolymers of ethylene and methyl acrylates ; polyvinyl chloride resins ; polyamides , poly ( amide - ester ) elastomers , and graft copolymers of ionomer and polyamide including , for example , pebax ® thermoplastic polyether block amides , commercially available from arkema inc ; cross - linked trans - polyisoprene and blends thereof ; polyester - based thermoplastic elastomers , such as hytrel ®, commercially available from e . i . du pont de nemours and company ; polyurethane - based thermoplastic elastomers , such as elastollan ®, commercially available from basf ; synthetic or natural vulcanized rubber ; and combinations thereof . while the inventive golf ball may be formed from a variety of differing and conventional materials for the intermediate layer ( s ), inner cover layer ( s ) and / or outer cover layer ( s ), preferred cover materials include , but are not limited to : ( 1 ) polyurethanes , such as those prepared from polyols and diisocyanates or polyisocyanates and / or their prepolymers ; ( 3 ) polyurethane - urea hybrids , blends or copolymers comprising urethane and urea segments . suitable polyurethane compositions comprise a reaction product of at least one polyisocyanate and at least one curing agent . the curing agent can include , for example , one or more polyamines , one or more polyols , or a combination thereof . the polyisocyanate can be combined with one or more polyols to form a prepolymer , which is then combined with the at least one curing agent . thus , the polyols described herein are suitable for use in one or both components of the polyurethane material , i . e ., as part of a prepolymer and in the curing agent . suitable polyurethanes are described in u . s . patent application publication no . 2005 / 0176523 , which is incorporated by reference in its entirety . any polyisocyanate available to one of ordinary skill in the art is suitable for use according to the invention . exemplary polyisocyanates include , but are not limited to , 4 , 4 ′- diphenylmethane diisocyanate ( mdi ); polymeric mdi ; carbodiimide - modified liquid mdi ; 4 , 4 ′- dicyclohexylmethane diisocyanate ( h 12 mdi ); p - phenylene diisocyanate ( ppdi ); m - phenylene diisocyanate ( mpdi ); toluene diisocyanate ( tdi ); 3 , 3 ′- dimethyl - 4 , 4 ′- biphenylene diisocyanate ; isophoronediisocyanate ; 1 , 6 - hexamethylene diisocyanate ( hdi ); naphthalene diisocyanate ; xylene diisocyanate ; p - tetramethylxylene diisocyanate ; m - tetramethylxylene diisocyanate ; ethylene diisocyanate ; propylene - 1 , 2 - diisocyanate ; tetramethylene - 1 , 4 - diisocyanate ; cyclohexyl diisocyanate ; dodecane - 1 , 12 - diisocyanate ; cyclobutane - 1 , 3 - diisocyanate ; cyclohexane - 1 , 3 - diisocyanate ; cyclohexane - 1 , 4 - diisocyanate ; 1 - isocyanato - 3 , 3 , 5 - trimethyl - 5 - isocyanatomethylcyclohexane ; methyl cyclohexylene diisocyanate ; triisocyanate of hdi ; triisocyanate of 2 , 4 , 4 - trimethyl - 1 , 6 - hexane diisocyanate ; tetracene diisocyanate ; napthalene diisocyanate ; anthracene diisocyanate ; isocyanurate of toluene diisocyanate ; uretdione of hexamethylene diisocyanate ; and mixtures thereof . polyisocyanates are known to those of ordinary skill in the art as having more than one isocyanate group , e . g ., di - isocyanate , tri - isocyanate , and tetra - isocyanate . preferably , the polyisocyanate includes mdi , ppdi , tdi , or a mixture thereof , and more preferably , the polyisocyanate includes mdi . it should be understood that , as used herein , the term mdi includes 4 , 4 ′- diphenylmethane diisocyanate , polymeric mdi , carbodiimide - modified liquid mdi , and mixtures thereof . additionally , the prepolymers synthesized from these diisocyanates may be “ low free monomer ,” understood by one of ordinary skill in the art to have lower levels of “ free ” isocyanate monomers , typically less than about 0 . 1 % free isocyanate . examples of “ low free monomer ” prepolymers include , but are not limited to low free monomer mdi prepolymers , low free monomer tdi prepolymers , and low free monomer ppdi prepolymers . any polyol available to one of ordinary skill in the art is suitable for use according to the invention . exemplary polyols include , but are not limited to , polyether polyols , hydroxy - terminated polybutadiene ( including partially / fully hydrogenated derivatives ), polyester polyols , polycaprolactone polyols , and polycarbonate polyols . in one preferred embodiment , the polyol includes polyether polyol . examples include , but are not limited to , polytetramethylene ether glycol ( ptmeg ), polyethylene propylene glycol , polyoxypropylene glycol , and mixtures thereof . the hydrocarbon chain can have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups . preferably , the polyol of the present invention includes ptmeg . in another embodiment , polyester polyols are included in the polyurethane material . suitable polyester polyols include , but are not limited to , polyethylene adipate glycol ; polybutylene adipate glycol ; polyethylene propylene adipate glycol ; o - phthalate - 1 , 6 - hexanediol ; poly ( hexamethylene adipate ) glycol ; and mixtures thereof . the hydrocarbon chain can have saturated or unsaturated bonds , or substituted or unsubstituted aromatic and cyclic groups . in another embodiment , polycaprolactone polyols are included in the materials of the invention . suitable polycaprolactone polyols include , but are not limited to , 1 , 6 - hexanediol - initiated polycaprolactone , diethylene glycol initiated polycaprolactone , trimethylol propane initiated polycaprolactone , neopentyl glycol initiated polycaprolactone , 1 , 4 - butanediol - initiated polycaprolactone , and mixtures thereof . the hydrocarbon chain can have saturated or unsaturated bonds , or substituted or unsubstituted aromatic and cyclic groups . in yet another embodiment , polycarbonate polyols are included in the polyurethane material of the invention . suitable polycarbonates include , but are not limited to , polyphthalate carbonate and poly ( hexamethylene carbonate ) glycol . the hydrocarbon chain can have saturated or unsaturated bonds , or substituted or unsubstituted aromatic and cyclic groups . in one embodiment , the molecular weight of the polyol is from about 200 to about 4000 . polyamine curatives are also suitable for use in the polyurethane composition of the invention and have been found to improve cut , shear , and impact resistance of the resultant balls . preferred polyamine curatives include , but are not limited to , 3 , 5 - dimethylthio - 2 , 4 - toluenediamine and isomers thereof ; 3 , 5 - diethyltoluene - 2 , 4 - diamine and isomers thereof , such as 3 , 5 - diethyltoluene - 2 , 6 - diamine ; 4 , 4 ′- bis -( sec - butylamino )- diphenylmethane ; 1 , 4 - bis -( sec - butylamino )- benzene , 4 , 4 ′- methylene - bis -( 2 - chloroaniline ); 4 , 4 ′- methylene - bis -( 3 - chloro - 2 , 6 - diethylaniline ); polytetramethyleneoxide - di - p - aminobenzoate ; n , n ′- dialkyldiamino diphenyl methane ; p , p ′- methylene dianiline ; m - phenylenediamine ; 4 , 4 ′- methylene - bis -( 2 - chloroaniline ); 4 , 4 ′- methylene - bis -( 2 , 6 - diethylaniline ); 4 , 4 ′- methylene - bis -( 2 , 3 - dichloroaniline ); 4 , 4 ′- diamino - 3 , 3 ′- diethyl - 5 , 5 ′- dimethyl diphenylmethane ; 2 , 2 ′, 3 , 3 ′- tetrachloro diamino diphenylmethane ; trimethylene glycol di - p - aminobenzoate ; and mixtures thereof . preferably , the curing agent of the present invention includes 3 , 5 - dimethylthio - 2 , 4 - toluenediamine and isomers thereof , such as ethacure ® 300 , commercially available from albermarle corporation of baton rouge , la . suitable polyamine curatives , which include both primary and secondary amines , preferably have molecular weights ranging from about 64 to about 2000 . at least one of a diol , triol , tetraol , or hydroxy - terminated curatives may be added to the aforementioned polyurethane composition . suitable diol , triol , and tetraol groups include ethylene glycol ; diethylene glycol ; polyethylene glycol ; propylene glycol ; polypropylene glycol ; lower molecular weight polytetramethylene ether glycol ; 1 , 3 - bis ( 2 - hydroxyethoxy ) benzene ; 1 , 3 - bis -[ 2 -( 2 - hydroxyethoxy ) ethoxy ] benzene ; 1 , 3 - bis -{ 2 -[ 2 -( 2 - hydroxyethoxy ) ethoxy ] ethoxy } benzene ; 1 , 4 - butanediol ; 1 , 5 - pentanediol ; 1 , 6 - hexanediol ; resorcinol - di -( β - hydroxyethyl ) ether ; hydroquinone - di -( β - hydroxyethyl ) ether ; and mixtures thereof . preferred hydroxy - terminated curatives include 1 , 3 - bis ( 2 - hydroxyethoxy ) benzene ; 1 , 3 - bis -[ 2 -( 2 - hydroxyethoxy ) ethoxy ] benzene ; 1 , 3 - bis -{ 2 -[ 2 -( 2 - hydroxyethoxy ) ethoxy ] ethoxy } benzene ; 1 , 4 - butanediol , and mixtures thereof . preferably , the hydroxy - terminated curatives have molecular weights ranging from about 48 to 2000 . it should be understood that molecular weight , as used herein , is the absolute weight average molecular weight and would be understood as such by one of ordinary skill in the art . both the hydroxy - terminated and amine curatives can include one or more saturated , unsaturated , aromatic , and cyclic groups . additionally , the hydroxy - terminated and amine curatives can include one or more halogen groups . the polyurethane composition can be formed with a blend or mixture of curing agents . if desired , however , the polyurethane composition may be formed with a single curing agent . in a preferred embodiment of the present invention , saturated polyurethanes are used to form one or more of the cover layers , preferably the outer cover layer , and may be selected from among both castable thermoset and thermoplastic polyurethanes . thermosetting polyurethanes or polyureas are suitable for the outer cover layers of the golf balls of the invention . additionally , polyurethane can be replaced with or blended with a polyurea material . polyureas are distinctly different from polyurethane compositions , giving better shear resistance . the polyurea - based compositions are preferably saturated in nature . the polyether amine may be blended with additional polyols to formulate copolymers that are reacted with excess isocyanate to form the polyurea prepolymer . in one embodiment , less than about 30 percent polyol by weight of the copolymer is blended with the saturated polyether amine . in another embodiment , less than about 20 percent polyol by weight of the copolymer , preferably less than about 15 percent by weight of the copolymer , is blended with the polyether amine the polyols listed above with respect to the polyurethane prepolymer , e . g ., polyether polyols , polycaprolactone polyols , polyester polyols , polycarbonate polyols , hydrocarbon polyols , other polyols , and mixtures thereof , are also suitable for blending with the polyether amine . the molecular weight of these polymers may be from about 200 to about 4000 , but also may be from about 1000 to about 3000 , and more preferably are from about 1500 to about 2500 . the polyurea composition can be formed by crosslinking a polyurea prepolymer with a single curing agent or a blend of curing agents . the curing agent of the invention is preferably an amine - terminated curing agent , more preferably a secondary diamine curing agent so that the composition contains only urea linkages . in one embodiment , the amine - terminated curing agent may have a molecular weight of about 64 or greater . in another embodiment , the molecular weight of the amine - curing agent is about 2000 or less . as discussed above , certain amine - terminated curing agents may be modified with a compatible amine - terminated freezing point depressing agent or mixture of compatible freezing point depressing agents suitable amine - terminated curing agents include , but are not limited to , ethylene diamine ; hexamethylene diamine ; 1 - methyl - 2 , 6 - cyclohexyl diamine ; tetrahydroxypropylene ethylene diamine ; 2 , 2 , 4 - and 2 , 4 , 4 - trimethyl - 1 , 6 - hexanediamine ; 4 , 4 ′- bis -( sec - butylamino )- dicyclohexylmethane ; 1 , 4 - bis -( sec - butylamino )- cyclohexane ; 1 , 2 - bis -( sec - butylamino )- cyclohexane ; derivatives of 4 , 4 ′- bis -( sec - butylamino )- dicyclohexylmethane ; 4 , 4 ′- dicyclohexylmethane diamine ; 1 , 4 - cyclohexane - bis -( methylamine ); 1 , 3 - cyclohexane - bis -( methylamine ); diethylene glycol di -( aminopropyl ) ether ; 2 - methylpentamethylene - diamine ; diaminocyclohexane ; diethylene triamine ; triethylene tetramine ; tetraethylene pentamine ; propylene diamine ; 1 , 3 - diaminopropane ; dimethylamino propylamine ; diethylamino propylamine ; dipropylene triamine ; imido - bis - propylamine ; monoethanolamine , diethanolamine ; 3 , 5 - diethyltoluene - 2 , 4 - diamine ; triethanolamine ; monoisopropanolamine , diisopropanolamine ; isophoronediamine ; 4 , 4 ′- methylenebis -( 2 - chloroaniline ); 3 , 5 - dimethylthio - 2 , 4 - toluenediamine ; 3 , 5 - dimethylthio - 2 , 6 - toluenediamine ; 3 , 5 - diethylthio - 2 , 4 - toluenediamine ; 3 , 5 - diethylthio - 2 , 6 - toluenediamine ; 4 , 4 ′- bis -( sec - butylamino )- diphenylmethane and derivatives thereof ; 1 , 4 - bis -( sec - butylamino )- benzene ; 1 , 2 - bis -( sec - butylamino )- benzene ; n , n ′- dialkylamino - diphenylmethane ; n , n , n ′, n ′- tetrakis ( 2 - hydroxypropyl ) ethylene diamine ; trimethyleneglycol - di - p - aminobenzoate ; polytetramethyleneoxide - di - p - aminobenzoate ; 4 , 4 ′- methylenebis -( 3 - chloro - 2 , 6 - diethyleneaniline ); 4 , 4 ′- methylenebis -( 2 , 6 - diethylaniline ); meta - phenylenediamine ; paraphenylenediamine ; and mixtures thereof . in one embodiment , the amine - terminated curing agent is 4 , 4 ′- bis -( sec - butylamino )- dicyclohexylmethane . suitable saturated amine - terminated curing agents include , but are not limited to , ethylene diamine ; hexamethylene diamine ; 1 - methyl - 2 , 6 - cyclohexyl diamine ; tetrahydroxypropylene ethylene diamine ; 2 , 2 , 4 - and 2 , 4 , 4 - trimethyl - 1 , 6 - hexanediamine ; 4 , 4 ′- bis -( sec - butylamino )- dicyclohexylmethane ; 1 , 4 - bis -( sec - butylamino )- cyclohexane ; 1 , 2 - bis -( sec - butylamino )- cyclohexane ; derivatives of 4 , 4 ′- bis -( sec - butylamino )- dicyclohexylmethane ; ; 4 , 4 ′- dicyclohexylmethane diamine ; 4 , 4 ′- methylenebis -( 2 , 6 - diethylaminocyclohexane ; 1 , 4 - cyclohexane - bis -( methylamine ); 1 , 3 - cyclohexane - bis -( methylamine ); diethylene glycol di -( aminopropyl ) ether ; 2 - methylpentamethylene - diamine ; diaminocyclohexane ; diethylene triamine ; triethylene tetramine ; tetraethylene pentamine ; propylene diamine ; 1 , 3 - diaminopropane ; dimethylamino propylamine ; diethylamino propylamine ; imido - bis - propylamine ; monoethanolamine , diethanolamine ; triethanolamine ; monoisopropanolamine , diisopropanolamine ; isophoronediamine ; triisopropanolamine ; and mixtures thereof . in addition , any of the polyether amines listed above may be used as curing agents to react with the polyurea prepolymers . alternatively , other suitable polymers include partially or fully neutralized ionomer , metallocene , or other single - site catalyzed polymer , polyester , polyamide , non - ionomeric thermoplastic elastomer , copolyether - esters , copolyether - amides , polycarbonate , polybutadiene , polyisoprene , polystryrene block copolymers ( such as styrene - butadiene - styrene ), styrene - ethylene - propylene - styrene , styrene - ethylene - butylene - styrene , and the like , and blends thereof . cover layers of the inventive golf ball may also be formed from ionomeric polymers , preferably highly - neutralized ionomers ( hnp ). in a preferred embodiment , at least one intermediate layer of the golf ball is formed from an hnp material or a blend of hnp materials . the acid moieties of the hnp &# 39 ; s , typically ethylene - based ionomers , are preferably neutralized greater than about 70 %, more preferably greater than about 90 %, and most preferably at least about 100 %. the hnp &# 39 ; s can be also be blended with a second polymer component , which , if containing an acid group , may be neutralized in a conventional manner , by organic fatty acids , or both . the second polymer component , which may be partially or fully neutralized , preferably comprises ionomeric copolymers and terpolymers , ionomer precursors , thermoplastics , polyamides , polycarbonates , polyesters , polyurethanes , polyureas , thermoplastic elastomers , polybutadiene rubber , balata , metallocene - catalyzed polymers ( grafted and non - grafted ), single - site polymers , high - crystalline acid polymers , cationic ionomers , and the like . hnp polymers typically have a material hardness of between about 20 and about 80 shore d , and a flexural modulus of between about 3 , 000 psi and about 200 , 000 psi . in one embodiment of the present invention the hnp &# 39 ; s are ionomers and / or their acid precursors that are preferably neutralized , either fully or partially , with organic acid copolymers or the salts thereof the acid copolymers are preferably a - olefin , such as ethylene , c 3 - 8 μ , β - ethylenically unsaturated carboxylic acid , such as acrylic and methacrylic acid , copolymers . they may optionally contain a softening monomer , such as alkyl acrylate and alkyl methacrylate , wherein the alkyl groups have from 1 to 8 carbon atoms . the acid copolymers can be described as e / x / y copolymers where e is ethylene , x is an α , β - ethylenically unsaturated carboxylic acid , and y is a softening comonomer . in a preferred embodiment , x is acrylic or methacrylic acid and y is a c 1 - 8 alkyl acrylate or methacrylate ester . x is preferably present in an amount from about 1 to about 35 weight percent of the polymer , more preferably from about 5 to about 30 weight percent of the polymer , and most preferably from about 10 to about 20 weight percent of the polymer . y is preferably present in an amount from about 0 to about 50 weight percent of the polymer , more preferably from about 5 to about 25 weight percent of the polymer , and most preferably from about 10 to about 20 weight percent of the polymer . specific acid - containing ethylene copolymers include , but are not limited to , ethylene / acrylic acid / n - butyl acrylate , ethylene / methacrylic acid / n - butyl acrylate , ethylene / methacrylic acid / iso - butyl acrylate , ethylene / acrylic acid / iso - butyl acrylate , ethylene / methacrylic acid / n - butyl methacrylate , ethylene / acrylic acid / methyl methacrylate , ethylene / acrylic acid / methyl acrylate , ethylene / methacrylic acid / methyl acrylate , ethylene / methacrylic acid / methyl methacrylate , and ethylene / acrylic acid / n - butyl methacrylate . preferred acid - containing ethylene copolymers include , ethylene / methacrylic acid / n - butyl acrylate , ethylene / acrylic acid / n - butyl acrylate , ethylene / methacrylic acid / methyl acrylate , ethylene / acrylic acid / ethyl acrylate , ethylene / methacrylic acid / ethyl acrylate , and ethylene / acrylic acid / methyl acrylate copolymers . the most preferred acid - containing ethylene copolymers are , ethylene /( meth ) acrylic acid / n - butyl , acrylate , ethylene /( meth ) acrylic acid / ethyl acrylate , and ethylene /( meth ) acrylic acid / methyl acrylate copolymers . ionomers are typically neutralized with a metal cation , such as li , na , mg , k , ca , or zn . it has been found that by adding sufficient organic acid or salt of organic acid , along with a suitable base , to the acid copolymer or ionomer , the ionomer can be neutralized , without losing processability , to a level much greater than for a metal cation . preferably , the acid moieties are neutralized greater than about 80 %, preferably from 90 - 100 %, most preferably 100 % without losing processability . this is accomplished by melt - blending an ethylene α , β - ethylenically unsaturated carboxylic acid copolymer , for example , with an organic acid or a salt of organic acid , and adding a sufficient amount of a cation source to increase the level of neutralization of all the acid moieties ( including those in the acid copolymer and in the organic acid ) to greater than 90 %, ( preferably greater than 100 %). the organic acids of the present invention are aliphatic , mono - or multi - functional ( saturated , unsaturated , or multi - unsaturated ) organic acids . salts of these organic acids may also be employed . the salts of organic acids of the present invention include the salts of barium , lithium , sodium , zinc , bismuth , chromium , cobalt , copper , potassium , strontium , titanium , tungsten , magnesium , cesium , iron , nickel , silver , aluminum , tin , or calcium , salts of fatty acids , particularly stearic , behenic , erucic , oleic , linoelic or dimerized derivatives thereof it is preferred that the organic acids and salts of the present invention be relatively non - migratory ( they do not bloom to the surface of the polymer under ambient temperatures ) and non - volatile ( they do not volatilize at temperatures required for melt - blending ). the ionomers of the invention may also be more conventional ionomers , i . e ., partially - neutralized with metal cations . the acid moiety in the acid copolymer is neutralized about 1 to about 90 %, preferably at least about 20 to about 75 %, and more preferably at least about 40 to about 70 %, to form an ionomer , by a cation such as lithium , sodium , potassium , magnesium , calcium , barium , lead , tin , zinc , aluminum , or a mixture thereof . the moisture vapor barrier layer ( s ) of the inventive golf ball may also contain additives , ingredients , and other materials in amounts that do not detract from the properties of the final composition . these additive materials include , but are not limited to , activators such as calcium or magnesium oxide ; fatty acids such as stearic acid and salts thereof ; fillers and reinforcing agents such as organic or inorganic particles , for example , clays , talc , calcium , magnesium carbonate , silica , aluminum silicates , zeolites , powdered metals , and organic or inorganic fibers , plasticizers such as dialkyl esters of dicarboxylic acids ; surfactants ; softeners ; tackifiers ; waxes ; ultraviolet ( uv ) light absorbers and stabilizers ; antioxidants ; optical brighteners ; whitening agents such as titanium dioxide and zinc oxide ; dyes and pigments ; processing aids ; release agents ; and wetting agents . these compositions provide improved melt processability , and a balance of ball performance . blowing / foaming agents may also be particularly compatible with the moisture vapor barrier layer incorporated golf ball of the invention , including , for example those disclosed in u . s . pat . no . 7 , 708 , 654 . typical physical foaming / blowing agents include volatile liquids such as freons ( cfcs ), other halogenated hydrocarbons , water , aliphatic hydrocarbons , gases , and solid blowing agents , i . e ., compounds that liberate gas as a result of desorption of gas . preferably , the blowing agent includes an adsorbent . typical adsorbents include , for example , activated carbon , calcium carbonate , diatomaceous earth , and silicates saturated with carbon dioxide . chemical foaming / blowing agents are more preferred , particularly when the core includes thermoplastics such as ionomers , highly neutralized polymers , and polyolefins . chemical blowing agents may be inorganic , such as ammonium carbonate and carbonates of alkalai metals , or may be organic , such as azo and diazo compounds , such as nitrogen - based azo compounds . suitable azo compounds include , but are not limited to , 2 , 2 ′- azobis ( 2 - cyanobutane ), 2 , 2 ′- azobis ( methylbutyronitrile ), azodicarbonamide , p , p ′- oxybis ( benzene sulfonyl hydrazide ), p - toluene sulfonyl semicarbazide , p - toluene sulfonyl hydrazide . other blowing agents include any of the celogens , sold by crompton chemical corporation , and nitroso compounds , sulfonylhydrazides , azides of organic acids and their analogs , triazines , tri - and tetrazole derivatives , sulfonyl semicarbazides , urea derivatives , guanidine derivatives , and esters such as alkoxyboroxines . other possible blowing agents include agents that liberate gasses as a result of chemical interaction between components such as mixtures of acids and metals , mixtures of organic acids and inorganic carbonates , mixtures of nitriles and ammonium salts , and the hydrolytic decomposition of urea . alternatively , low specific gravity can be achieved by incorporating low density fillers or agents such as hollow fillers or microspheres in the polymeric matrix , where the cured composition has the preferred specific gravity . moreover , the polymeric matrix can be foamed to decrease its specific gravity , microballoons , or other low density fillers as described in u . s . pat . no . 6 , 692 , 380 (“&# 39 ; 380 patent ”). the &# 39 ; 380 patent is incorporated by reference in its entirety . the moisture barrier composition in the golf ball of this invention may be blended with non - ionomeric and olefin - based ionomeric polymers to form the composition that will be used to make the golf ball layer . examples of non - ionomeric polymers include vinyl resins , polyolefins including those produced using a single - site catalyst or a metallocene catalyst , polyurethanes , polyureas , polyamides , polyphenylenes , polycarbonates , polyesters , polyacrylates , engineering thermoplastics , and the like . also , in one embodiment of the invention , processability of the golf ball of the invention may even be enhanced by incorporating in the core a metallocene - catalyzed polybutadiene . olefin - based ionomers , such as ethylene - based copolymers , normally include an unsaturated carboxylic acid , such as methacrylic acid , acrylic acid , or maleic acid . other possible carboxylic acid groups include , for example , crotonic , maleic , fumaric , and itaconic acid . “ low acid ” and “ high acid ” olefin - based ionomers , as well as blends of such ionomers , may be used . in general , low acid ionomers are considered to be those containing 16 wt . % or less of carboxylic acid , whereas high acid ionomers are considered to be those containing greater than 16 wt . % of carboxylic acid . the acidic group in the olefin - based ionic copolymer is partially or totally neutralized with metal ions such as zinc , sodium , lithium , magnesium , potassium , calcium , manganese , nickel , chromium , copper , or a combination thereof . for example , ionomeric resins having carboxylic acid groups that are neutralized from about 10 percent to about 100 percent may be used . in one embodiment , the acid groups are partially neutralized . that is , the neutralization level is from 10 to 80 %, more preferably 20 to 70 %, and most preferably 30 to 50 %. in another embodiment , the acid groups are highly or fully neutralized . or , the neutralization level may be from about 80 to 100 %, more preferably 90 to 100 %, and most preferably 95 to 100 %. the blend may contain about 5 to about 30 % by weight of the moisture barrier composition and about 95 to about 70 % by weight of a partially , highly , or fully - neutralized olefin - based ionomeric copolymer . the above - mentioned blends may contain one or more suitable compatibilizers such as glycidyl acrylate or glycidyl methacrylate or maleic anhydride containing - polymers . the core may contain sections having the same hardness or different hardness levels . that is , there can be uniform hardness throughout the different sections of the core or there can be hardness gradients across the layers . for example , in single cores , there may be a hard - to - soft gradient ( a “ positive ” gradient ) from the surface of the core to the geometric center of the core . in other instances , there may be a soft - to - hard gradient ( a “ negative ” gradient ) or zero hardness gradient from the core &# 39 ; s surface to the core &# 39 ; s center . for dual core golf balls , the inner core layer may have a surface hardness that is less than the geometric center hardness to define a first “ negative ” gradient . as discussed above , an outer core layer may be formed around the inner core layer , and the outer core layer may have an outer surface hardness less than its inner surface hardness to define a second “ negative ” gradient . in other versions , the hardness gradients from surface to center may be hard - to - soft (“ positive ”), or soft - to - hard (“ negative ”), or a combination of both gradients . in still other versions the hardness gradients from surface to center may be “ zero ” ( that is , the hardness values are substantially the same .) methods for making cores having positive , negative , and zero hardness gradients are known in the art as described in , for example , u . s . pat . nos . 7 , 537 , 530 ; 7 , 537 , 529 ; 7 , 427 , 242 ; and 7 , 410 , 429 , the disclosures of which are hereby incorporated by reference . a golf ball according to the invention may therefore incorporate the moisture vapor barrier composition in a core to achieve various hardness gradients therein . for example , the moisture vapor barrier composition may be incorporated in a single - core constituting a solid core having a “ positive ” hardness gradient ( that is , the outer surface of the core is harder than its geometric center .) in a second embodiment , the moisture vapor barrier composition may be incorporated in a a dual - core comprising an inner core and a surrounding outer core layer . the inner core has a “ positive ” hardness gradient and the outer core layer has a “ negative ” hardness gradient ( that is , the outer surface of the outer core layer is softer than the inner surface of the outer core layer .) other embodiments of golf balls having various combinations of positive , negative , and zero hardness gradients may be made in accordance with this invention . for example , the inner core may have a positive hardness gradient and the outer core layer also may have a positive hardness gradient . in another example , the inner core may have a positive hardness gradient and the outer core layer may have a “ zero ” hardness gradient . ( that is , the hardness values of the outer surface of the outer core layer and the inner surface of the outer core layer are substantially the same .) particularly , the term , “ zero hardness gradient ” as used herein , means a surface to center shore c hardness gradient of less than 8 , preferably less than 5 and most preferably less than 3 and may have a value of zero or negative 1 to negative 25 . the term , “ negative hardness gradient ” as used herein , means a surface to center shore c hardness gradient of less than zero . the terms , zero hardness gradient and negative hardness gradient , may be used herein interchangeably to refer to hardness gradients of negative 1 to negative 25 . the term , “ positive hardness gradient ” as used herein , means a surface to center shore c hardness gradient of 8 or greater , preferably 10 or greater , and most preferably 20 or greater . by the term , “ steep positive hardness gradient ” as used herein , it is meant surface to center shore c hardness gradient of 20 or greater , more preferably 25 or greater , and most preferably 30 or greater . for example , the moisture vapor barrier composition containing core may have a step positive hardness gradient of 35 , 40 , or 45 shore c or greater . methods for measuring the hardness of the inner core and surrounding layers and determining the hardness gradients are discussed in further detail below . the center hardness of a core is obtained according to the following procedure . the core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core , such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed . the core is secured in the holder by friction , such that it will not move during the cutting and grinding steps , but the friction is not so excessive that distortion of the natural shape of the core would result . the core is secured such that the parting line of the core is roughly parallel to the top of the holder . the diameter of the core is measured 90 degrees to this orientation prior to securing . a measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations . a rough cut is made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool , making sure that the core does not move in the holder during this step . the remainder of the core , still in the holder , is secured to the base plate of a surface grinding machine . the exposed ‘ rough ’ surface is ground to a smooth , flat surface , revealing the geometric center of the core , which can be verified by measuring the height from the bottom of the holder to the exposed surface of the core , making sure that exactly half of the original height of the core , as measured above , has been removed to within 0 . 004 inches . leaving the core in the holder , the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark according to astm d - 2240 . additional hardness measurements at any distance from the center of the core can then be made by drawing a line radially outward from the center mark , and measuring the hardness at any given distance along the line , typically in 2 mm increments from the center . the hardness at a particular distance from the center should be measured along at least two , preferably four , radial arms located 180 ° apart , or 90 ° apart , respectively , and then averaged . all hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation , such that the test surface is constantly parallel to the bottom of the holder , and thus also parallel to the properly aligned foot of the durometer . the outer surface hardness of a golf ball layer is measured on the actual outer surface of the layer and is obtained from the average of a number of measurements taken from opposing hemispheres , taking care to avoid making measurements on the parting line of the core or on surface defects , such as holes or protrusions . hardness measurements are made pursuant to astm d - 2240 “ indentation hardness of rubber and plastic by means of a durometer .” because of the curved surface , care must be taken to ensure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained . a calibrated , digital durometer , capable of reading to 0 . 1 hardness units is used for the hardness measurements . the digital durometer must be attached to , and its foot made parallel to , the base of an automatic stand . the weight on the durometer and attack rate conform to astm d - 2240 . in certain embodiments , a point or plurality of points measured along the “ positive ” or “ negative ” gradients may be above or below a line fit through the gradient and its outermost and innermost hardness values . in an alternative preferred embodiment , the hardest point along a particular steep “ positive ” or “ negative ” gradient may be higher than the value at the innermost portion of the inner core ( the geometric center ) or outer core layer ( the inner surface )— as long as the outermost point ( i . e ., the outer surface of the inner core ) is greater than ( for “ positive ”) or lower than ( for “ negative ”) the innermost point ( i . e ., the geometric center of the inner core or the inner surface of the outer core layer ), such that the “ positive ” and “ negative ” gradients remain intact . as discussed above , the direction of the hardness gradient of a golf ball layer is defined by the difference in hardness measurements taken at the outer and inner surfaces of a particular layer . the center hardness of an inner core and hardness of the outer surface of an inner core in a single - core ball or outer core layer are readily determined according to the test procedures provided above . the outer surface of the inner core layer ( or other optional intermediate core layers ) in a dual - core ball are also readily determined according to the procedures given herein for measuring the outer surface hardness of a golf ball layer , if the measurement is made prior to surrounding the layer with an additional core layer . once an additional core layer surrounds a layer of interest , the hardness of the inner and outer surfaces of any inner or intermediate layers can be difficult to determine . therefore , for purposes of the present invention , when the hardness of the inner or outer surface of a core layer is needed after the inner layer has been surrounded with another core layer , the test procedure described above for measuring a point located 1 mm from an interface is used . also , it should be understood that there is a fundamental difference between “ material hardness ” and “ hardness as measured directly on a golf ball .” for purposes of the present invention , material hardness is measured according to astm d2240 and generally involves measuring the hardness of a flat “ slab ” or “ button ” formed of the material . surface hardness as measured directly on a golf ball ( or other spherical surface ) typically results in a different hardness value . the difference in “ surface hardness ” and “ material hardness ” values is due to several factors including , but not limited to , ball construction ( that is , core type , number of cores and / or cover layers , and the like ); ball ( or sphere ) diameter ; and the material composition of adjacent layers . it also should be understood that the two measurement techniques are not linearly related and , therefore , one hardness value cannot easily be correlated to the other . shore c hardness was measured according to the test methods d - 2240 . several different methods can be used to measure compression , including atti compression , riehle compression , load / deflection measurements at a variety of fixed loads and offsets , and effective modulus . see , e . g ., compression by any other name , science and golf iv , proceedings of the world scientific congress of golf ( eric thain ed ., routledge , 2002 ) (“ j . dalton ”) the term compression , as used herein , refers to atti or pga compression and is measured using an atti compression test device . a piston compresses a ball against a spring and the piston remains fixed while deflection of the spring is measured at 1 . 25 mm ( 0 . 05 inches ). where a core has a very low stiffness , the compression measurement will be zero at 1 . 25 mm in order to measure the compression of a core using an atti compression tester , the core must be shimmed to a diameter of 1 . 680 inches because these testers are designed to measure objects having that diameter . atti compression units can be converted to riehle ( cores ), riehle ( balls ), 100 kg deflection , 130 - 10 kg deflection or effective modulus using the formulas set forth in j . dalton . the approximate relationship that exists between atti or pga compression and riehle compression can be expressed as : ( atti or pga compression )=( 160 - riehle compression ). thus , a riehle compression of 100 would be the same as an atti compression of 60 . cor , as used herein , is determined by firing a golf ball or golf ball subassembly ( e . g ., a golf ball core ) from an air cannon at two given velocities and calculating the cor at a velocity of 125 ft / s . ball velocity is calculated as a ball approaches ballistic light screens which are located between the air cannon and a steel plate at a fixed distance . as the ball travels toward the steel plate , each light screen is activated , and the time at each light screen is measured . this provides an incoming transit time period inversely proportional to the ball &# 39 ; s incoming velocity . the ball impacts the steel plate and rebounds through the light screens , which again measure the time period required to transit between the light screens . this provides an outgoing transit time period inversely proportional to the ball &# 39 ; s outgoing velocity . cor is then calculated as the ratio of the outgoing transit time period to the incoming transit time period , cor = v out / v in = t in / t out . preferably , a golf ball according to the present invention has a cor of at least about 0 . 78 , more preferably , at least about 0 . 80 . the spin rate of a golf ball also remains an important golf ball characteristic . high spin rate allows skilled players more flexibility in stopping the ball on the green if they are able to control a high spin ball . on the other hand , recreational players often prefer a low spin ball since they do not have the ability to intentionally control the ball , and lower spin balls tend to drift less off the green . golf ball spin is dependent on variables including , for example , distribution of the density or specific gravity within a golf ball . for example , when the center has a higher density or specific gravity than the outer layers , a lower moment of inertia results which increases spin rate . alternatively , when the density or specific gravity is concentrated in the outer regions of the golf ball , a higher moment of inertia results with a lower spin rate . the moment of inertia for a golf ball of the invention may be from about 0 . 410 oz - in 2 to about 0 . 470 oz - in t . the moment of inertia for a one piece ball that is 1 . 62 ounces and 1 . 68 inches in diameter may be approximately 0 . 4572 oz - in 2 , which is the baseline moment of inertia value . accordingly , by varying the materials and the hardness of the regions of each core layer , different moments of inertia may be achieved for the golf ball of the present invention . in one embodiment , the resulting golf ball has a moment of inertia of from about to 0 . 440 to about 0 . 455 oz - in 2 . in another embodiment , the golf balls of the present invention have a moment of inertia of from about 0 . 456 oz - in 2 to about 0 . 470 oz - in 2 . in yet another embodiment , the golf ball has a moment of inertia of from about 0 . 450 oz - in t to about 0 . 460 oz - in t . unless otherwise expressly specified , all of the numerical ranges , amounts , values and percentages such as those for amounts of materials , and others in the specification may be read as if prefaced by the word “ about ” even though the term “ about ” may not expressly appear with the value , amount or range . accordingly , unless indicated to the contrary , the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention . at the very least , and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims , each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques . notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations , the numerical values set forth in the specific examples are reported as precisely as possible . any numerical value , however , inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements . furthermore , when numerical ranges of varying scope are set forth herein , it is contemplated that any combination of these values inclusive of the recited values may be used . while it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the preferred embodiments of the present invention , it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art . examples of such modifications include reasonable variations of the numerical values and / or materials and / or components discussed above . hence , the numerical values stated above and claimed below specifically include those values and the values that are approximate to those stated and claimed values . therefore , it will be understood that the appended claims are intended to cover all such modifications and embodiments , which would come within the spirit and scope of the present invention . the invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed , since these embodiments are intended as illustrations of several aspects of the invention . any equivalent embodiments are intended to be within the scope of this invention . indeed , various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description . for example , the compositions of the present invention may be used in a variety of equipment . such modifications are also intended to fall within the scope of the appended claims . while any of the embodiments herein may have any known dimple number and pattern , a preferred number of dimples is 252 to 456 , and more preferably is 328 to 392 . the dimples may comprise any width , depth , and edge angle disclosed in the prior art and the patterns may comprises multitudes of dimples having different widths , depths and edge angles . the parting line configuration of said pattern may be either a straight line or a staggered wave parting line ( swpl ). in one embodiment , the golf bal has 328 , 330 , 332 , or 392 dimples , comprises 5 to 7 dimples sizes , and the parting line is a swpl . in any of these embodiments the single - layer core may be replaced with a two or more layer core wherein at least one core layer has a negative hardness gradient . other than in the operating examples , or unless otherwise expressly specified , all of the numerical ranges , amounts , values and percentages such as those for amounts of materials and others in the specification may be read as if prefaced by the word “ about ” even though the term “ about ” may not expressly appear with the value , amount or range . accordingly , unless indicated to the contrary , the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention . at the very least , and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims , each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques .
the invention is directed to a golf ball comprising a core , a cover and optionally an intermediate layer disposed between the core and the cover , wherein at least one of the core , the intermediate layer and the cover comprises a moisture vapor barrier layer formed from a moisture vapor barrier composition comprising at least one diene rubber and at least one fluorinated silane treated filler . the filler is hydrophobically modified by fluorinated silane , a hydrophobizing material capable of rendering the surfaces of the silica particles suitably hydrophobic . this moisture vapor barrier composition , which may be incorporated in the golf ball prior to molding , protects the encased inner golf ball components from moisture penetration which damages the golf ball and deteriorates desired golf ball characteristics . such a golf ball preserves and even enhances optimum golf ball properties and desired golf ball characteristics such as high spin , resilience and durability which may be negatively influenced or impacted by unintended changes in golf ball component compression , cor and hardness due to moisture invasion . the golf ball may comprise an untreated region and a treated outer surface , the treated outer surface having a moisture vapor transmission rate x and the untreated region having a moisture vapor transmission rate y , the treated outer surface being treated with and comprising a moisture vapor barrier composition formed from at least one diene rubber and at least one fluorinated silane treated filler such that x & lt ; y .