Structural and mechanical behavior of polypropylene/ maleated styrene‐(ethylene‐co‐butylene)‐styrene/sisal fiber composites prepared by injection molding

Abstract

Hybrid composites consisting of isotactic poly(propylene) (PP), sisal fiber (SF), and maleic anhydride grafted styrene‐(ethylene‐co‐butylene)‐styrene copolymer (MA‐SEBS) were prepared by melt compounding, followed by injection molding. The melt‐compounding torque behavior, thermal properties, morphology, crystal structure, and mechanical behavior of the PP/MA‐SEBS/SF composites were systematically investigated. The torque test, thermogravimetric analysis, differential scanning calorimetric, and scanning electron microscopic results all indicated that MA‐SEBS was an effective compatibilizer for the PP/SF composites, and there was a synergism between MA‐SEBS and PP/SF in the thermal stability of the PP/MA‐SEBS/SF composites. Wide‐angle X‐ray diffraction analysis indicated that the α form and β form of the PP crystals coexisted in the PP/MA‐SEBS/SF composites. With the incorporation of MA‐SEBS, the relative amount of β‐form PP crystals decreased significantly. Mechanical tests showed that the tensile strength and impact toughness of the PP/SF composites were generally improved by the incorporation of MA‐SEBS. The instrumented drop‐weight dart‐impact test was also used to examine the impact‐fracture behavior of these composites. The results revealed that the maximum impact force (Fmax), impact‐fracture energy (ET), total impact duration (tr), crack‐initiation time (tinit), and crack‐propagation time (tprop) of the composites all tended to increase with an increasing MA‐SEBS content. From these results, the incorporation of MA‐SEBS into PP/SF composites can retard both the crack initiation and propagation phases of the impact‐fracture process. These prolonged the crack initiation and propagation time and increased the energy consumption during impact fracture, thereby leading to toughening of PP/MA‐SEBS/SF composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1214–1222, 2002

Preparation and mechanical properties of high‐performance short ramie fiber‐reinforced polypropylene composites

“…The enhancement of toughness is due to the suppression of fiber/matrix debonding and fiber pull-out as a result of the compatibilization effect of the MAPP-coupling agent. Xie et al 24 studied the composites of PP/sisal fiber and obtained a similar result. Figure 6 shows the variation of the storage modulus with the temperature detected from DMA test for the PP/RF blends with various RF contents.…”

Thermogravimetric behavior of natural fibers reinforced polymer composites—An overview

“…The first small peak occurred, for the different MA-SEBS contents, at approximately the same temperatures: 363 1C (PP-0); 367 1C (PP-8); and 365 1C (PP-16). The existence of this first peak was an indication to the authors [46] that the thermal stability of neat MA-SEBS is better than that for the composites. The second major peak was observed at slightly higher temperatures, when MA-SEBS is introduced in the composite.…”

“…A more visually reliable method is to consider the first decomposition DTG peak, either single or as a shoulder. The works overviewed have shown that this first DTG peak occurred in a range from 250 1C [50] to 365 1C [46], depending on the fiber and polymer matrix. Apparently, the onset of thermogravimetric degradation in a natural fiber composite is a complex process, which depends not only on the comparative thermal stability of fiber vs. matrix but also on the experiment atmosphere.…”

“…In fact, this second peak occurred at 451 1C (PP-0); 459 1C (PP-8); and 457 1C (PP-16). Xie et al [46] indicated that the incorporation of MA-SEBS improves the thermal stability of the composites, which was attributed to MA-SEBS interactions between PP and sisal fibers. No discussion was presented on degradation mechanisms.…”

“…Xie et al [46] investigated the thermogravimetric behavior of composites consisting of polypropylene (PP) and maleic anhydride grafted styrene-ethylene-co-butylene-styrene copolymer (MA-SEBS) reinforced with 20 wt% of untreated sisal fibers. Hybrid PP/MA-SEBS matrices were compounded with 0 wt% (PP-0); 8 wt% (PP-8); and 16 wt% (PP-16) of MA-SEBS.…”