Hemp‐fiber‐reinforced unsaturated polyester composites: Optimization of processing and improvement of interfacial adhesion

Abstract

ABSTRACT:The processing variables for making hempfiber-reinforced unsaturated polyester (UPE) composites were optimized through orthogonal experiments. It was found that the usage of initiator, methyl ethyl ketone peroxide, had the most significant effect on the tensile strength of the composites. The treatment of hemp fibers with a combination of 1,6-diisocyanatohexane (DIH) and 2-hydroxyethyl acrylate (HEA) significantly increased tensile strength, flexural modulus of rupture, and flexural modulus of elasticity, and water resistance of the resulting hemp-UPE composites. FTIR spectra revealed that DIH and HEA were covalently bonded to hemp fibers. Scanning electron microscopy graphs of the fractured hemp-UPE composites demonstrated that treatment of hemp fibers with a combination of DIH and HEA greatly improved the interfacial adhesion between hemp fibers and UPE. The mechanism of improving the interfacial adhesion is proposed.

Effect of fiber modification with 3-isopropenyl-dimethylbenzyl isocyanate (TMI) on the mechanical properties and water absorption of hemp-unsaturated polyester (UPE) composites

“…Isocyanates and blocked isocyanates have been widely investigated for pre-treatments and enhancement of the adhesion between fibers and polymeric matrices (Gironès et al 2007(Gironès et al , 2008Kuang et al 2010). Treatments of hemp fibers with a combination of 1,6-diisocyanatohexane and 2-hydroxylethyl acrylate, or only with isocyanatoethyl methacrylate, significantly improved the interfacial adhesion and reduced the water-uptake of the resulting hemp-UPE composites (Qiu et al 2011;Chen et al 2013).…”

Mechanical Properties and Water Absorption of Hemp Fibers–Reinforced Unsaturated Polyester Composites: Effect of Fiber Surface Treatment with a Heterofunctional Monomer

“…In previous studies, the treatment of hemp fibers with a combination of 1,6-diisocyanatohexane and 2-hydroxylethyl acrylate, or independently with N-methylol acrylamide and using sulfuric acid as the catalyst significantly improved the interfacial adhesion between hemp fibers and UP resins, and reduced the water-uptake of the resulting hemp-UP composites (Qiu et al 2011. In this study, a novel isocyanate coupling agent, isocyanatoethyl methacrylate (IEM), was investigated for the treatment of hemp fibers.…”

“…The advantages of natural plant fibers over inorganic fibers as reinforcers are high specific strength and modulus, economical viability, and good biodegradability. Several studies (Akil et al 2009;He et al 2012;Marais et al 2005;Qiu et al 2011;Ren et al 2012) have been done on the replacement of inorganic fibers with bast fibers such as jute, flax, hemp, ramie, or kenaf for reinforcing polymer materials.…”

Effect of fiber modification with a novel compatibilizer on the mechanical properties and water absorption of hemp‐fiber‐reinforced unsaturated polyester composites

“…The treatment of hemp fibers with a combination of 1,6‐diisocyanatohexane (DIH) and 2‐hydroxylethyl acrylate (HEA) significantly improved the interfacial adhesion between hemp fibers and UPE and reduced the water‐uptake of the resulting hemp–UPE composites. However, organic solvent ethyl acetate was used for dissolution of DIH and HEA [25]. Despite extensive research, the hemp fiber‐reinforced UPE composites are still inferior to glass‐fiber‐reinforced UPE composites in terms of strengths and water resistances [4–9, 25].…”

“…However, organic solvent ethyl acetate was used for dissolution of DIH and HEA [25]. Despite extensive research, the hemp fiber‐reinforced UPE composites are still inferior to glass‐fiber‐reinforced UPE composites in terms of strengths and water resistances [4–9, 25]. Therefore, additional studies on chemical treatment of hemp fibers are needed for further improvement of strength and water resistance of hemp–UPE composites.…”