Aqueous Poly(N-Vinylformamide-co-Vinylamine) as a Suitable Adhesion Promoter for Wood Veneer/Biopolyethylene Composite Materials

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.