High molecular weight linear polyesters and copolymers of glycols and terephthalic or isophthalic acid have been available for a number of years. These are described inter alia in Whinfield, et al, U.S. Pat. No. 3,047,539. These patents disclose that the polyesters are particularly advantageous as film and fiber-formers.
Poly(1,4-butylene terephthalate), because of its very rapid crystallization from melt, is uniquely useful as a component in injection moldable compositions. Work pieces molded from such polyester resins, in comparison with other thermoplastics, offer a high degree of surface hardness and abrasion resistance, high gloss and low surface friction.
One useful family of such compositions comprises those which are reinforced, e.g., with from about 5% to about 55% filamentous glass, based on the weight of glass and polyester components, and optionally rendered flame retardant by the incorporation of a flame-retarding amount of a flame retarding compound.
The versatility of injection moldable compositions containing poly(1,4-butylene terephthalate) resin has been demonstrated, however, it is always desirable to increase the versatility of these compositions by the addition of additives and the like to modify the physical properties thereof. For example, U.S. Pat. No. 4,104,242, Kochanowski, et al., disclose the addition of a hydrazine compound to poly(1,4-butylene terephthalate) resin for modifying resistance to high voltage breakdown. Other properties, including impact strength, flexural strength, flexural modulus, tensile strength, melt viscosity, arc track rate, etc., may also be the object of such improvement efforts.
It is an object of the present invention to improve the physical properties of articles molded from glass fiber reinforced poly(1,4-butylene terephthalate) resin molding compositions.
It is another object of the present invention to improve the physical properties of articles molded from fiber reinforced, flame retarded poly(1,4-butylene terephthalate) resin molding compositions.