Combining Fiber Enzymatic Pretreatments and Coupling Agents to Improve Physical and Mechanical Properties of Hemp Hurd/Wood/Polypropylene Composite.

Xiaoping Li,Mingwei Yang,Mingli Qiang,Jeffrey J Morrell,Neng Zhang

doi:10.3390/ma14216384

Xiaoping Li, Mingwei Yang + Show 3 more

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https://doi.org/10.3390/ma14216384

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Abstract

Natural fiber/plastic composites combine the low density and excellent mechanical properties of the natural fiber with the flexibility and moisture resistance of the plastic to create materials tailored to specific applications in theory. Wood/plastic composites (WPC) are the most common products, but many other fibers are being explored for this purpose. Among the more common is hemp hurd. Natural fibers are hydrophilic materials and plastics are hydrophobic, therefore one problem with all of these products is the limited ability of the fiber to interact with the plastic to create a true composite. Thus, compatibilizers are often added to enhance interactions, but fiber pretreatments may also help improve compatibility. The effects of pectinase or cellulase pretreatment of wood/hemp fiber mixtures in combination with coupling agents were evaluated in polypropylene panels. Pretreatments with pectinase or cellulase were associated with reduced thickness swell (TS24h) as well as increased modulus of rupture and modulus of elasticity. Incorporation of 5.0% silane or 2.5% silane/2.5% titanate as a coupling agent further improved pectinase-treated panel properties, but was associated with diminished properties in cellulase treated fibers. Combinations of enzymatic pretreatment and coupling agents enhanced fiber/plastic interactions and improved flexural properties, but the effects varied with the enzyme or coupling agent employed. The results illustrate the potential for enhancing fiber/plastic interactions to produce improved composites.

Highlights

Interest in natural fiber/plastic composites has increased as manufacturers search for products that can perform in exterior applications, such as decking, or provide exceptional strength properties [1,2,3,4,5,6,7]
Wood/plastic composites have received the most attention because they combine the low density and high tensile strength of wood with the moisture resistance of plastics, but a number of other cellulosic fibers have been explored for this purpose, including rice hull husks and hemp, in locations where wood is less abundant [8,9,10,11]
The objective of this study was to explore the potential for combining enzymatic pretreatments and coupling agents to improve the properties of wood/hemp hurd/polypropylene composite panels and create low-density, high strength wood/plastic composites

Summary

Introduction

Interest in natural fiber/plastic composites has increased as manufacturers search for products that can perform in exterior applications, such as decking, or provide exceptional strength properties [1,2,3,4,5,6,7]. The one negative aspect of all these materials is the lack of substantial interactions between the hygroscopic fiber and hydrophobic plastic [12]. While compatibilizers such as silanes, titanate, and maleic anhydride can be added to enhance interactions, they add cost and still do not fully integrate the two materials. Identifying pretreatments for making fibers more compatible with the plastic might help improve properties [13,14,15,16]. 4.0/).

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