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The viscosity, shear strength, and peel strength of [natural rubber (Standard Malaysian Rubber (SMR) L grade)]‐based pressure‐sensitive adhesives were studied by using hybrid tackifiers, i.e., mixtures of coumarone–indene resin and petro resin. Toluene and poly(ethylene terephthalate) were used as the solvent and substrate, respectively. Viscosity of the adhesives was determined with a HAAKE rotary viscometer, whereas shear and peel strength were measured by a Lloyd adhesion tester. Results showed that the viscosity and shear strength decreased with increasing petro resin concentration, an observation which is attributed to the plasticizing effect of the resin. Peel strength, however, showed a maximum value at 60 phr (parts by weight per hundred parts of resin) petro resin concentration, thus indicating maximum wettability at this petro resin content. Peel strength increased with coating thickness for all the peel tests studied. In all cases, a 90° peel test consistently exhibited the highest peel value. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers

The demand for natural fiber hybrid composites for various applications has increased, which is leading to more research being conducted on natural fiber hybrid composites due to their promising mechanical properties. However, the incompatibility of natural fiber with polymer matrix limits the performance of the natural fiber hybrid composite. In this research work, the mechanical properties and fiber-to-matrix interfacial adhesion were investigated. The efficiency of methyl methacrylate (MMA)-esterification treatments on composites’ final product performance was determined. The composite was prepared using the hand lay-up method with varying kenaf bast fiber (KBF) contents of 10, 15, 20, 25, 30, 35 (weight%) and hybridized with glass fiber (GF) at 5 and 10 (weight%). Unsaturated polyester (UPE) resin and methyl ethyl ketone peroxide (MEKP) were used as binders and catalysts, respectively. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to examine the effects of MMA-esterification treatment on tensile strength and morphology (tensile fracture and characterization of MMA-esterification treatment) of the composite fabricated. The tensile strength of MMA-treated reinforced UPE and hybrid composites are higher than that of untreated composites. As for MMA treatment, 90 min of treatment showed the highest weight percent gain (WPG) and tensile strength of KBF-reinforced UPE composites. It can be concluded that the esterification of MMA on the KBF can lead to better mechanical properties and adhesion between the KFB and the UPE matrix. This research provides a clear reference for developing hybrid natural fibers, thus contributing to the current field of knowledge related to GF composites, specifically in transportation diligences due to their properties of being lightweight, superior, and involving low production cost.

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