Structures And Properties Of NBR Based TPV And Waste NBR Powder Based TPE

Thermoplastic vulcanizates (TPVs) based on acrylonitrile-butadiene-styrene terpolymer (ABS)/nitrile-butadiene rubber (NBR) blends and high density polyethylene (HDPE)/NBR blends were prepared by dynamic vulcanization. The mechanical properties, morphology, Mullins effect and its reversibility, Payne effect, compression set and its reversibility of the TPVs were investigated systematically. The influences of blending ratio, compatibilizer, plasticizer and reinforcing agent on the properties of the TPVs were also researched. Water-swellable rubber (WSR) were prepared based on ABS/chlorinated polyethylene rubber (CM)/NBR and HDPE/chlorinated polyethylene resin (CPE)/NBR TPVs; the effects of water-absorbent material content on the water swellable behavior, the repeated water swellable behavior, water retention ability, weight loss and microstructure morphology of the WSRs were studied. Thermoplastic elastomers (TPEs) based on ABS/waste NBR powder (WNBRP) and HDPE/WNBRP composites were prepared via melt-compounding. The interfacial compatibility, mechanical properties, morphology and Mullins effect of the TPE were researched. The results were shown as below:(1) ABS/NBR TPV was prepared by dynamic vulcanization, styrene-butadiene-styrene block copolymer (SBS), CPE and CM were respectively filled in the ABS matrix as compatibilizers; the influences of the compatibilizers on the mechanical properties, morphology, Mullins effect and Payne effect of the TPVs were investigated systematically. With the existence of compatibilizers in the matrix of TPV, the elongation at break, tensile strength and tearing strength of the prepared TPVs were improved remarkably. The FE-SEM results showed that the fracture surfaces of the compatibilized TPV were relatively smoother and the interfacial interaction were strong; the vulcanized NBR particles were dispersed evenly in the etched TPVs and the NBR particle size was decreased with the incorporation of compatibilizer. Mullins effect results showed that an obvious softening phenomenon could be observed in the stress-stretch curves of TPVs during the uniaxial loading-unloading cycles; the maximum stress, internal friction and tanS under the fixed stretch were decreased obviously after the first loading-unloading while only decreased slightly in the later loading-unloading cycles; the residual deformation and degree of stress softening effect of the TPV were increased with increasing cycle, while decreased with increasing stretch; the compatibilized TPV had relatively lower maximum stress and internal friction. DMA studies showed that the glass to rubber transition temperatures (Tgs) of ABS and NBR phases were slightly shifted toward each other with the incorporation of CM compatibilizer, indicating the improvement of the compatibility; Payne effect could be found in the strain scanning mode of DMA research.(2) The plasticization research of ABS/NBR TPV showed that the loading of DOP in the matrix of TPV reduced the tensile set at break and shore A hardness; however, the tensile strength and elongation at break were improved obviously; moreover, the fracture surface was smoother with the DOP loading. Mullins effect results showed that the TPV incorporated with DOP had relatively lower maximum stress, residual deformation, internal friction and degree of stress softening effect than that of the ABS/NBR TPV, indicating the improvement of elasticity. DMA studies showed that the Tgs of the NBR and ABS were slightly shifted toward the lower values, while the Tgs were shifted towards each other with the incorporation of DOP plasticizer, indicating the significant improvement of the compatibility.(3) The reinforcement research of ABS/NBR TPV showed that the tensile strength and tearing strength of the TPV could be improved significantly with the incorporation of CB in the NBR phase, while the elongation at break and tensile set at break were decreased. The vulcanized NBR particles were dispersed evenly in the etched TPV, while the particle size was reduced with the CB incorporation.(4) The reversibility of Mullins effect investigation indicated that both improving heat-treatment temperature and increasing heat-treatment time could improve the reversible degree of the TPV. The plastic deformation and its recover degree of the matrix were important factors which influenced the Mullins behavior, the heat-treatment promoted the recovery of the plastic deformation of the resin phase, namely the reversibility of Mullins effect. When the heat-treatment time was 30 min, the best heat-treatment temperature for the reversibility ability of Mullins effect under tension and compression mode were 120℃ and 110℃, respectively.(5) The investigation of reversible recovery of compression set showed that increasing the NBR content in TPV and increasing heat-treatment temperature would lead to the fast recovery of compression set; moreover, the TPV had fully reversible deformation ability when the heat-treatment temperature was close to the Tg of ABS. The reversible recovery mechanism was discussed based on the characteristics of TPV microstructure and the reversible recovery curves of compression set. The generalized Maxwell model was used to describe the process of compression set recovery successfully and the influences of blending ratio and heat-treatment temperature on the relaxation time in each stage of the recovery course were discussed.(6) High density polyethylene (HDPE)/NBR blends were prepared by dynamic vulcanization; with increasing HDPE content, the tensile strength, tensile modulus, tearing strength and shore A hardness of HDPE/NBR blends were increased remarkably. The interfacial interaction of the dynamically vulcanized HDPE/NBR blends was enhanced by the incorporation of CPE compatibilizer. Experimental results indicated that CPE had an excellent compatibilization effect on the HDPE/NBR blends. Compared with that of the HDPE/NBR blend, the elongation at break, tensile strength and tearing strength of HDPE/CPE/NBR blends incorporated with 6 phr CPE were improved by 601.6%,167.6% and 165.8%, respectively. Morphology studies showed that the fracture surface of HDPE/CPE/NBR TPV was relatively smoother and less notable drawn fibrils can be found than that of HDPE/NBR blend; moreover, the dispersion of NBR particles was more evenly and the average size of the NBR particles decreased with the presence of CPE compatibilizer. DMA studies showed that the Tg of NBR phase was slightly shifted toward higher temperature with the CPE incorporation, leading to the increasing interface compatibility; and Payne effect could be found in the strain scanning study. Mullins effect results showed that the compatibilized HDPE/NBR blend had relatively lower maximum compressive stress, residual deformation, internal friction, tanδ and degree of stress softening effect than that of HDPE/NBR blend, indicating the improved interfacial interaction and the enhanced mechanical properties.(7) WSRs based on the ABS/CM/NBR and HDPE/CPE/NBR TPVs respectively had been prepared, where crosslinked poly(sodium acrylate) (CPNaAA) was used as super water-absorbent resin. The results showed that all the stress-strain curves of the WSRs showed the representative elastomeric character of being soft and tough. Increasing the CPNaAA dosages, the mechanical properties of WSRs were decreased while the water-swelling ratio and rate were increased significantly, especially when the CPNaAA was 40 phr above. With 70 phr CPNaAA incorporation, the ABS/CM/NBR/CPNaAA WSR achieved the equilibrium swelling at 95 hr immersion with 369.8% water-swelling ratio, while the HDPE/CPE/NBR/CPNaAA WSR achieved the equilibrium swelling at 55 hr immersion with 956.7% water-swelling ratio. The secondary and third water-swelling behaviors of WSRs showed significantly rapid equilibrium swelling and remarkable decreasing of weight loss. Morphological study showed that the CPNaAA particles were dispersed randomly in the TPVs and the interfacial interaction between the CPNaAA and TPV was weak. The FE-SEM graphs revealed that some significant expansion gaps were found in the surface of the dried water-swelled sample, which contributed to the high equilibrium swelling rates during the second and third water-swelling process.(8) TPEs based on ABS/WNBRP and HDPE/WNBRP composites were prepared by melt-compounding, and the composites were compatibilized by CPE. Experimental results indicated that CPE had an excellent compatibilization effect on the composites. The elongation at break, tensile strength and tearing strength of the composites were increased significantly with the incorporation of CPE, while influenced the hardness slightly. Morphology studies showed that the interfaces interaction of the composites compatibilized by CPE was stronger than those of uncompatibilized composites, and the fracture surfaces were smoother. A softening phenomenon could be observed in the stress-strain curves of ABS/CPE/WNBRP and HDPE/CPE/WNBRP TPEs during the uniaxial loading-unloading cycles; and the maximum stress, internal friction and tanδ under the fixed strain was decreased obviously after the first loading-unloading while only decreased slightly at the later loading-unloading cycles. The maximum stress, residual deformation, internal friction and tanδ of ABS/CPE/WNBRP and HDPE/CPE/WNBRP TPEs were decreased significantly with the incorporation of CPE.