Effects of Matrix Modification on the Mechanical Properties of Wood⁻Polypropylene Composites.

Shunmin Yi,Shihua Xu,Haigang Wang,Yiqun Fang,Qingwen Wang

doi:10.3390/polym9120712

Shunmin Yi, Shihua Xu + Show 3 more

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https://doi.org/10.3390/polym9120712

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Abstract

Polypropylene (PP) modified with two reactive monomers, divinyl benzene (DVB) and maleic anhydride (MAH), was used as the matrix to prepare wood–polypropylene composites to improve interfacial compatibility. The effects of the co-modified PP matrices with different DVB concentrations on the mechanical properties of the composites were evaluated. Compared with unmodified composites and the composites containing a coupling agent, the composites modified with MAH only, and that with both MAH and DVB, improved the tensile, flexural, and impact strengths. Interestingly, adding a small amount of DVB (0.4%) resulted in significant increase in impact strength, relative to that of the composites modified with MAH only. Dynamic mechanical analysis and fracture morphology analysis of the modified composites also suggested an improvement in interfacial adhesion owing to the matrix modification.

Highlights

The use of thermoplastic polymers reinforced with wood fibers (WF) has received considerable attention owing to the low energy consumption and environmentally friendly nature of the materials [1,2,3]
The results indicated that much less improvement in mechanical properties by matrix modification with maleic anhydride (MAH) only was observed (Table 3), which could be explained by the following: (i) the lower MAH concentration resulted in a lower MAH grafting level, which failed to provide much more effective fiber–matrix coupling for stress transfer from the modified PP to WF [24]; and (ii) MPPD0 underwent chain scission, which were prone to achieving more effective wetting of WF by MPPD0, thereby promoting the formation of effective coupling between WF and the modified matrix; the inferior strength of MPPD0 itself with respect to virgin PP offset the positive effect from improved interfacial adhesion [24]
PP matrix modified by grafting with both MAH and divinyl benzene (DVB) was compounded with wood fibers

Summary

Introduction

The use of thermoplastic polymers reinforced with wood fibers (WF) has received considerable attention owing to the low energy consumption and environmentally friendly nature of the materials [1,2,3]. The hydrophilic property of WF, similar to all natural fibers, has an inherently low compatibility with hydrophobic polymers, such as polypropylene (PP) and polyethylene (PE) [7]. This incompatibility is unfavorable for interfacial fiber–matrix adhesion and dispersion of the fibers, resulting in inferior mechanical properties of the composites [8]. Adding a coupling agent is known to efficiently improve interfacial adhesion by forming a chemical bridge between the fibers and the matrix [14,15,16]. Aggarwal et al reported that in jute–PP composites at 50% fiber concentration, the addition of 5% m-isopropenyl-α-α-dimethylbenzyl-isocyanate (m-TMI)-grafted-polypropylene as a coupling agent led to an increase in tensile and flexure strengths over virgin polypropylene, up to 87%

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Conclusion