Three kinds of surface treatment, that is, the alkalization (5% w/v NaOH aqueous solution), the deposition of diglycidyl ether of bisphenol A (DGEBA) from toluene solution (1% w/v DGEBA), and the alkalization combined with the deposition of DGEBA (5% w/v NaOH/1% w/v DGEBA) were applied to modify interfacial bonding and to enhance mechanical properties of pineapple leaf fiber (PALF) reinforced epoxy composites. The fiber strength and strain were measured by single fiber test and the fiber strength variation was assessed using Weibull modulus. Furthermore, a fragmentation test was used to quantify the interfacial adhesion of PALFepoxy composite. It was verified that the interfacial shear strength of modified PALFs was substantially higher than that of untreated PALF by almost 2-2.7 times because of the greater interaction between the PALFs and epoxy resin matrix. The strongest interfacial adhesion was obtained from the fibers that had been received the alkalization combined with DGEBA deposition. Moreover, the flexural and impact properties of unidirectional PALF-epoxy composites were greatly enhanced when reinforced with the modified PALFs due to an improvement in interfacial adhesion, particularly in the synergetic use of 5% NaOH and 5% NaOH/1% DGEBA.
View the article online for updates and enhancements. Abstract. The aim of this work was to study the properties of films based on PLA/PBAT blend prepared by the reactive compounding. PLA/PBAT blends were prepared at the weight ratio of 80:20 together with peroxide as a reactive agent in a twin screw extruder with temperature profile of 160/170/180/210/220/190/175/150ºC from feed to die zone. All blended samples, neat PLA, and neat PBAT were characterized for morphology, mechanical and rheological properties. SEM micrographs showed finely dispersed phases of PBAT in PLA in all cases. The particle sizes of PBAT were around 1 µm. The results indicated that the drawability and toughness properties of PLA were greatly improved when blended with 20%wt PBAT. The interface adhesion, and mechanical properties of PLA/PBAT blends were also improved when adding a very small quantity of peroxide. PLA/PBAT blends were then used to produce films. The film characteristics and mechanical properties were examined. Tensile strength of films was significantly improved in the machine direction in PLA/PBAT/peroxide blends whereas the good optical transparent property were remained the same compared with neat PLA.
Natural-rubber-based hybrid composites were prepared by the mixture of short cellulose fibers and silica of different relative contents with a 20-phr filler loading with a laboratory two-roll mill. The processability and tensile properties of the hybrid composites were analyzed. The tensile modulus improved, but the tensile strength and elongation at break decreased with increasing cellulose fiber content. The scorch safety improved with the addition of 5-phr cellulose fiber in the composites. The Mooney viscosity significantly decreased with increasing cellulose fiber content. To modify the surface properties of the cellulose fiber and silica fillers, a silane coupling agent [bis(triethoxysilylpropyl)tetrasulfide, or Si69] was used. The effects of Si69 treatment on the processing and tensile properties of the hybrid composites were assessed. We found that the silane treatment of both fillers had significant benefits on the processability but little benefit on the rubber reinforcement. The strength of the treated hybrid composite was comparable to that of silica-reinforced natural rubber. Furthermore, to investigate the filler surface modification and to determine the mixing effects, infrared spectroscopic and various microscopic techniques, respectively, were used. From these results, we concluded that the fillers were better dispersed in the composites, and the compatibility of the fillers and natural rubber increased with silane treatment. In conclusion, the hybridized use of short cellulose fibers from a renewable resource and silica with Si69 presented in this article offers practical benefits for the production of rubber-based composites having greater processability and more environmental compatibility than conventional silica-filler-reinforced rubber.
Thermoplastic vulcanizate (TPV) nanocomposites based on 60/40 (%wt) natural rubber (NR)/polypropylene (PP) blends were prepared by melt blending in an internal mixer. Sodium montmorillonite (Na-MMT) was first added in natural rubber latex to obtain natural rubber/clay masterbatch, which was subsequently dynamically crosslinked while mixing with molten PP. The effect of Na-MMT content were examined concerning elastomeric properties of NR/PP blends dynamically vulcanized using phenolic resin as a curing agent. Morphology characterization observed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and 3D microfocus X-ray computerized tomography showed that the dynamic vulcanization with nanoclay addition changed the blend morphology from a co-continuous-like structure to droplet-like phase one, and the clay remained within NR phase in intercalated and aggregated forms. Furthermore, the presence of clay induced the decrease in crosslinking of NR, but promoted the mixing between NR and PP during dynamic vulcanization. This suggested that nanoclay worked as a kind of morphology modifier during dynamic vulcanization. The addition of clay marginally enhanced the 100 % modulus and tensile strength, but led to the decrease of the elongation at break. The optimal level of tensile strength improvement was obtained with loading of 5 phr clay. The permanent set of the NR/PP/Clay TPV nanocomposites was well maintained at the acceptable level as elastomer. The resistances to oil and heat were improved with incorporation of clay, proportional to clay loading. The experimental results indicated that the nanoclay had a positive effect on improving the 60/40 NR/PP blend morphology, which provided a little benefit to strength of the TPVs. However, the addition of nanoclay offered an improvement in oil and thermal resistances due to a combined effect of the clay dispersion and improved morphology of NR and PP blends.
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