Interfacial Adhesion and Mechanical Properties of Wood-Polymer Hybrid Composites Prepared by Injection Molding.

Alexander Stadlmann,Maximilian Pramreiter,Andreas Mautner,Alexander Bismarck,Ulrich Müller

doi:10.3390/polym13172849

Alexander Stadlmann, Maximilian Pramreiter + Show 3 more

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https://doi.org/10.3390/polym13172849

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Abstract

Birch (Betula pendula Roth.) and beech (Fagus sylvatica L.) solid wood and plywood were overmolded with polyamide 6 (PA 6) and polypropylene (PP) to investigate their mechanical properties and interfacial adhesion. In the case of PA 6, maximum tensile shear strengths values of more than 8 to 9 MPa were obtained for birch and beech, respectively. The values are comparable to bond strengths of commercial joints bonded with formaldehyde-containing amino-plastics. Perpendicular to the wood elements, bond strength values of 3 MPa was achieved for PA 6. The penetration of the polymers into the wood structure results in a non-densified interphase and subsequent plastic deformation of the wood structure beyond the interphase. These compressed areas influenced the interfacial adhesion and mechanical interlocking. SEM and XPS analysis revealed different interpenetration behavior of the polymers into the wood structure, with chemical interaction confirmed only for wood and PA 6 but not PP.

Highlights

The mobility sector of the European Union is responsible for 26% of its total CO2 emissions
Higher strength and stiffness of wood-polyamide 6 (PA 6) composites can be explained by PA 6 penetrating the wood structure on a macro- and microscopic level, which corresponds to previous findings [16]
Chemical interaction of PA 6 with wood takes place due to the polar nature of the material, resulting in better interfacial adhesion as compared to PP and improved mechanical properties of wood-PA 6 composites produced by injection molding

Summary

Introduction

The mobility sector of the European Union is responsible for 26% of its total CO2 emissions. Around one fourth of these emissions are driven by the weight of the vehicle [1], increasing the importance of lightweight materials for automotive parts like wood [2]. Manufacturing technologies such as milling, cutting, gluing, molding, etc. In order to introduce wood and wood-based materials in these new areas of application such as the automotive industry, it is necessary to consider new production technologies during the design of wood-based hybrid components. Due to its sustainable nature and comparably low density, in recent years there has been an increasing demand for the utilization of wood and renewable materials in the mobility sector [5–9]. Besides utilizing sustainable and renewable products, formaldehyde-free bonding and joining of wood get more and more importance. The total amount of adhesive in plywood production can reach levels up to 20% for continuous bond lines that require high loading [10,11]

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