
 Possibilities for compositional tailoring of Norway spruce (Picea abies
 L. Karst.) wood using a hydrophobic oil impregnation process

ZusammenfassungImpregnation with hydrophobic oils offers non-toxic options for preserving Norway spruce (Picea abies L. Karst) wood that could potentially be used to tailor the properties
 of wood products, especially those used in exposed conditions. The objective of this study was to quantify
 the effects of the water-filled porosity and density of Norway spruce wood and treatments (applied to set
 the wood’s water contents at desired test levels) prior to impregnation with the linseed oil derivative
 Linogard by the Linotech process on its oil retention. Retention of oil differed significantly between
 tissue types. Dried specimens always retained less oil than corresponding undried or rewetted specimens.
 Furthermore, water-filled porosity and density had significant effects on oil retention levels within tissue
 types, allowing linear regression equations to be developed that gave good predictions of oil retention
 parameters for different tissues, with R2 values ranging from 0.66 for mature
 heartwood to 0.85 for mature sapwood. Thus there is scope to use hydrophobic oil impregnation processes
 for producing compositionally tailored wood materials with specified properties.

Assessing the need for transformation of response variables
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Mechanical performance of linseed oil impregnated pine as correlated to the take-up level
Abstract The mechanical performance of pine sapwood (pinus sylvestris), impregnated with linseed oil to different take-up levels, is evaluated using several test methods. SEM is used to study morphological changes following the impregnation procedure. The reduction of mechanical properties is attributed to a) localized cell wall damage in the ray region that facilitates longitudinal inter-cell split in L-R plane (macrocrack) initiation and propagation; b) submicroscopical cracking in the S1 sublayer that reduces the resistance to Mode I and Mode II inter-cell splitting at any location where the oil front has passed. Mechanical testing shows the following effect of the impregnation on failure a) the Mode I fracture toughness GIc in L-T and L-R planes, determined in DCB test, is significantly lowered with no significant difference in fracture resistance reduction in between planes; b) 3-point flexural test for specimen geometry leading to cracking in R-L and T-L planes show that the flexural strength as well as flexural modulus are reduced due to impregnation; c) 3-point flexural tests on longitudinal specimens used to determine the impregnation effect on longitudinal modulus EL and shear moduli GLT and GLR, reveal only minor changes. Fracture surfaces in mechanical tests are analyzed using SEM, and differences are explained by described microdamage mechanisms.