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This study aimed to investigate the suitability of the interlaminar shear (ILS) testing method for veneer-based composites. The ILS testing method is an established method for composite materials as a qualitative evaluation of the adhesion within the composite. The applicability of this method to veneer based composites enables a simple qualitative statement on the adhesion of the individual layers. The ILS method complements existing wood-based material tests that focus on bonding, using significantly smaller material dimensions.

Wood veneer/biopolyethylene (bio-PE) biocomposite materials were produced by using poly(N-vinylformamide-co-vinylamine) (PVFA-co-PVAm) copolymers as a phase-mediating reagent. In a preliminary step, PVFA-co-PVAm was adsorbed onto the wood veneer component from aqueous solution. In its adsorbed form, it served as an adhesion promoter and improved the compatibility between both the highly polar wood veneer and weakly polar bio-PE surface. Structural parameters and their effect on the adsorption process, such as the degree of hydrolysis (DH) of poly(N-vinylformamide) (PVFA) (30, 50, and > 90%), the molecular weight of PVFA-co-PVAm (Mw 10,000, 45,000, or 340,000 g/mol), and the pH value (4, 7, and 11) influenced the resulting wetting behavior of the PVFA-co-PVAm-modified wood veneer surface. Thus, the hydrophobizing effect of the PVFA-co-PVAm was clearly detectable because the contact angle with water was considerably increased up to 116° by adsorption of PVFA-co-PVAm 9095 at pH 11. The adsorbed amount of PVFA-co-PVAm was determined by energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). The PVFA-co-PVAm-coated wood veneers were consolidated with bio-PE in a hot press process. The modified composite materials showed remarkably improved Young’s moduli (552 MPa) and tensile strengths (4.5 MPa) compared to former composite materials produced without PVFA-co-PVAm modification.

Short-rotation coppices have potential to be the future source of raw materials for many applications in the wood and paper industries. It is important to establish methods and products to handle their waste biomass. In this paper, the properties of bast fibers extracted from the bark of willow trees (Salix spp.) were evaluated for potential future use in the production of natural fiber-polymer composites. The anatomy of the fibers was investigated through optical and electron microscopy. The thermogravimetric analysis of these fibers showed that the major mass loss occurs at 257 °C. The density of the fibers was measured with a gas pycnometer (1.19 ± 0.2 g/cm3). The chemical analysis showed that willow bark fibers have a composition similar to willow wood. As an indicator of mechanical properties, single willow bast fibers were characterized by tensile tests. The results revealed values for tensile strength (307.6 ± 130.1 MPa) and Young’s modulus (16.9 ± 8.4 GPa) that are comparable to some commonly used natural fibers. The overall results showed that willow bast fibers have the required mechanical properties as well as thermal stability for application in reinforcement of polymers.

Bamboo is a very interesting bio resource for building materials because of its combination of strength properties and low density. However, its susceptibility to fungi and insects is problematic. Thermal modification is used in Vietnam to improve the durability and dimensional stability of bamboo. Changes in the chemical composition during this modification are the reason for such physical changes as color, equilibrium moisture content, and strength. This paper will describe the changes in the chemical composition depending on the modification conditions. Furthermore correlations between chemical composition and physical properties, which are presented in Part I, are shown.