Surface Modification of Wood Flour via ARGET ATRP and Its Application as Filler in Thermoplastics.

Martin Kaßel,Philipp Vana,Julia Gerke,Adrian Ley

doi:10.3390/polym10040354

Martin Kaßel, Philipp Vana + Show 2 more

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https://doi.org/10.3390/polym10040354

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Journal: Polymers	Publication Date: Mar 22, 2018
Citations: 7	License type: CC BY 4.0

Affiliation: University of Göttingen

Abstract

Wood flour is particularly suitable as a filler in thermoplastics because it is environmentally friendly, readily available, and offers a high strength-to-density ratio. To overcome the insufficient interfacial adhesion between hydrophilic wood and a hydrophobic matrix, a thermoplastic polymer was grafted from wood flour via surface-initiated activators regenerated by electron transfer-atom transfer radical polymerization (SI-ARGET ATRP). Wood particles were modified with an ATRP initiator and subsequently grafted with methyl acrylate for different polymerization times in the absence of a sacrificial initiator. The successful grafting of poly(methyl acrylate) (PMA) was demonstrated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and water contact angle (WCA) measurements. To confirm the control over the polymerization, a cleavable ATRP initiator was immobilized on the particles, allowing the detachment of the grafted polymer under mild conditions. The grafted particles were incorporated into a PMA matrix using solvent casting and their influence on the mechanical properties (Young’s modulus, yield strength, and toughness) of the composite was investigated. Tensile testing showed that the mechanical properties improved with increasing polymerization time and increasing ratio of incorporated grafted particles.

Highlights

Composites are made by combining two or more components to give a new material with enhanced properties
The hydrophilic nature of wood, which originates from the high amount of surface hydroxyl groups, leads to poor compatibility in a hydrophobic thermoplastic matrix and, to low tensile strength and durability [2,7]
Acetone (ACS reagent, VWR Chemicals, Radnor, PA, USA); anisole (99%, Acros Organics, Geel, Belgium); ascorbic acid (AsAc, reagent grade, Sigma Aldrich, Saint Louis, MO, USA); azobisisobutyronitrile (AIBN, ≥98%, Fluka, Buchs, Switzerland), which was recrystallized from methanol; 2-bromoisobutyryl bromide (BIBB, 98%, Sigma Aldrich); Copper(II) bromide (CuBr2, 99%, Sigma Aldrich); 2-cyano-2-propyl dodecyl trithiocarbonate (98%, Sigma Aldrich); dichloromethane (DCM, HPLC Grade, Fluka); 4-dimethylaminopyridine (DMAP, 99%, Sigma Aldrich); dithiothreitol (DTT, Cleland’s reagent, ≥99%, Sigma Aldrich); 2-hydroxyethyl disulfide

Summary

Introduction

Composites are made by combining two or more components to give a new material with enhanced properties. The idea of composites was not invented by mankind; nature already provided high-performance composites in the form of wood. Wood is a suitable filler for composites because it is cheap, renewable, very abundant on earth, and offers a high strength-to-density ratio. Over the last decades there has been a rapid growth in interest in wood-reinforced thermoplastics due to their outstanding properties such as high durability, light weight, and low maintenance [4]. The hydrophilic nature of wood, which originates from the high amount of surface hydroxyl groups, leads to poor compatibility in a hydrophobic thermoplastic matrix and, to low tensile strength and durability [2,7].

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