INFLUENCE OF ASPEN WOOD DENSITY AND STEM POSITION ON SELECTED PROPERTIES OF WOOD POLYMER COMPOSITES

The quality of aspen wood polystyrene composites is decisively influen ced by the stem position and the height of the tree trunk from which t he wood was selected. Wood density is only of secondary importance. To produce wood polymer composites, aspen wood taken from sapwood areas is particularly suitable. Aspen wood taken from the heartwood zone is not suitable for producing composites due to lack of styrene saturatio n. This fact is caused by the presence of thyloses in vessels of these areas. The number of annual rings comprising heartwood zone in the sp ecimen ranged from 12 rings at breast height diameter to 5 rings at a stem height of 15 m. In the alburnous aspen wood polystyrene composite narrow cell lumina are completely filled. However, large diameter tra cheids are covered only by a thick polystyrene layer. The presence of polystyrene was also observed within cell walls. During composite prod uction using higher density sapwood layers a higher temperature peak o ccurs during the polymerization process. Dimensional stability of the aspen polystyrene composite depends mainly on the place in the trunk c rossection from which the sample was taken. The highest dimensional st ability was shown by a composite of sapwood layers containing the grea test amount of polystyrene. Bending strength of the aspen wood polysty rene composite depends not only on the polystyrene content in the wood but also on the original strength of the wood itself. Composite produ ced from wood of higher density are characterized by higher bending st rength. Hardness of the aspen wood polystyrene composite is, in princi ple, dependent on the polystyrene contents. An increase in polystyrene content improves composite hardness compressive in particular perpend icular to grain.