The influence of regranulate admixture on the properties of wood-polymer composite

Matrice dřevoplastového kompozitu je tvořena termoplasty s nízkým bodem měknutí, nejčastěji polyolefiny nebo polyvinylchloridem. Tyto termoplasty s širokým průmyslovým využitím umožňují jednostupňovou recyklaci, která by měla zachovat požadované vlastnosti primárního polymeru. Využití recyklované drtě nebo regranulátu pro výrobu dřevoplastového kompozitu závisí tedy na splnění parametrů (druhotné) suroviny v souvislosti s účelem a technologií výroby produktu.The WPC matrix is made of thermoplastics characterized by low softening point. The main types of WPC matrixes are polyolefins and polyvinylchloride. These thermoplastics, which provide a broad range of industrial utilization, allow a single-stage recycling that should maintain the virgin polymer properties. Therefore, the use of plastic regranulates in the form of a WPC matrix depends mainly on whether they meet the parameters required by the use purpose and production technology

Behaviour of Wood Joints Glued by One Component Polyurethane Adhesive Modified by Cotton Flakes and Basalt Fibers

The main objective of this paper is to describe the influence of cotton flakes and basalt fibers on the resulting tensile properties of one-component polyurethane and the tensile shear strength of glued lap joints of beech wood. Fillers are an integral part of the modification of adhesives, especially because they influence rheological and mechanical properties. A one- component polyurethane adhesive for waterproof joints was used for bonding. The amount of filler was optimized by determining the tensile properties of adhesive as a material. The basalt fibers improved the tensile properties of one-component polyurethane. The average tensile strength value for basalt fibers in the amount of 5% was found to be 30% higher than for basalt fibers in the amount of 1%. The resulting properties of glued joints were determined by tensile shear strength according to standard ČSN EN 302-1. It was found that the shear strength of the bonded beech joints was higher for modified one-component polyurethane by cotton flakes than those modified by basalt fibers of 7 mm length. Significant effect was shown for cohesive failure of lap joint especially for modification by cotton flakes when the value increased by 10% to reference wood joint

Properties of Plywood Panels Composed of Thermally Densified and Non-Densified Alder and Birch Veneers

Ukrainian companies mainly use birch in the manufacture of plywood, but species, such as black alder, are not yet widely used in the manufacture of plywood due to their poorer properties. It is well known that thermal compression is often used to improve the properties of solid wood. Good lay-up schemes of veneer can maximize the advantages and minimize the disadvantages of these wood species, and generally improve the utility value of the plywood. This research aimed to develop plywood panels with two wood species and two types of veneer treatments in order to evaluate the influences of different lay-up schemes on the properties of the plywood. Five-layer plywood panels were formed with 16 different lay-up schemes using birch (Betula verrucosa Ehrh.) (B) and black alder (Alnus glutinosa L.) (A) veneers, which were non-densified (N) and thermally densified (D). The different lay-up schemes were used to identify opportunities to improve the mechanical and physical properties of the plywood by replacing the birch veneer in the plywood structure with an alternative alder veneer. The veneer sheets were thermally densified in a laboratory hot press at a temperature of 180 °C and pressure of 2 MPa for 3 min. The conducted study showed that the bending strength, modulus of elasticity and shear strength of mixed-species plywood (BD–AN–AN–AN–BD) increased by up to 31.5%, 34.4% and 16.8%, respectively, in comparison to those properties of alder plywood from non-densified veneer (AN–AN–AN–AN–AN), by positioning alder non-densified veneers in the core layers and birch densified veneers in the outer layers. Moreover, the surface roughness of plywood panels with outer layers of birch veneer was lower than that of panels with outer layers of alder veneer. It was shown that non-treated alder veneer, despite exhibiting somewhat lower strength properties than birch veneer, could be successfully used with proper lay-up schemes in the veneer-based products industry