Effects of Heat-Treated Wood Particles on the Physico-Mechanical Properties and Extended Creep Behavior of Wood/Recycled-HDPE Composites Using the Time-Temperature Superposition Principle.

Teng-Chun Yang,Jyh-Horng Wu,Ke-Chang Hung,Yi-Chi Chien,Tung-Lin Wu

doi:10.3390/ma10040365

Teng-Chun Yang, Jyh-Horng Wu + Show 3 more

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https://doi.org/10.3390/ma10040365

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Journal: Materials	Publication Date: Mar 30, 2017
Citations: 14	License type: CC BY 4.0

Affiliation: National Chung Hsing University

Abstract

This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time–temperature superposition principle (TTSP), and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance (ICR) of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature.

Highlights

Wood-plastic composites (WPCs), in which lignocellulosic fillers act as a reinforcement, present many advantages, such as low cost, high specific strength and modulus, renewability, and biodegradability, compared with reinforced composites containing inorganic fillers [1]
There were no significant differences in the vertical density profiles among all of the WPCs
According to the increased rate of the compliance (b value), the WPC200 showed a reduced b value (0.12) compared with WPCNT. These results demonstrate that the creep resistance of the WPC was improved by the addition of heat-treated wood particles

Summary

Introduction

Wood-plastic composites (WPCs), in which lignocellulosic fillers act as a reinforcement, present many advantages, such as low cost, high specific strength and modulus, renewability, and biodegradability, compared with reinforced composites containing inorganic fillers (mineral fillers, glass fiber, etc.) [1]. The use of lignocellulosic fillers in polymer composites have several drawbacks as compared with inorganic fillers, including: (1) higher hygroscopicity, leading to dimensional changes due to their hydrophilic nature; (2) incompatibility between the hydrophilic lignocellulosic fillers and hydrophobic polymers; (3) non-uniform dispersion; and (4) lower thermal stability. Among these obstacles that limit the applications of WPCs in engineering materials, hygroscopicity, and incompatibility between the hydrophilic lignocellulosics and hydrophobic thermoplastics have been identified as major drawbacks. One of the physical modifications, heat treatment, Materials 2017, 10, 365; doi:10.3390/ma10040365 www.mdpi.com/journal/materials

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