Zhaobo Wang

Preparation and characterization of polyethylene/TiO2 nanocomposites

The rheological behaviour, dispersion, crystallization behavior, mechanical properties, fracture surface morphology of polyethylene (PE)/TiO2 nanocomposites prepared by melt compounding were investigated using rheometer, energy dispersive X-ray spectrometer (EDX), polarized microscopy, impact tester, universal testing machine and field-emission scanning electron microscopy (FE-SEM). The rheological analysis indicated a fine dispersion of TiO2 during the melt compounding. The large scaled surface dispersion of TiO2 nanoparticles was revealed by the EDX composition distribution maps. The introduction of 2.0 wt% TiO2 in composites improved the mechanical properties significantly compared to neat PE, and resulted in 45% increase in notched impact strength. Moreover, the further analysis and discussion showed the mechanical properties of the composites were controlled by the dispersion conditions of TiO2 and its nucleating effect on PE crystallization.

Dynamically Vulcanized Nitrile Butadiene Rubber/Ethylene-vinyl Acetate Copolymer Blends Compatibilized by Chlorinated Polyethylene

Thermoplastic vulcanizates (TPVs) based on nitrile butadiene rubber (NBR)/ethylene-vinyl acetate copolymer (EVA) blends were prepared by dynamic vulcanization, with the TPVs being compatibilized by chlorinated polyethylene (CPE). The effects of CPE compatibilizer on the mechanical and morphological properties of the TPVs were investigated systematically. Experimental results showed that the dynamically vulcanized NBR/EVA blends compatibilized by CPE had obvious elastomeric behavior and improved mechanical properties, indicating that CPE had a good compatibilization effect on the NBR/EVA TPVs. The fracture surface morphology of the compatibilized NBR/EVA TPV was somewhat rougher than that of uncompatibilized NBR/EVA; the large deformation during the tensile fracture could recover well and less notable, smaller diameter drawn fibrils were observed. Moreover, the interface interaction was strong and there was no obvious microphase separation. NBR particles were dispersed evenly in the etched surfaces of the NBR/EVA/CPE TPV.

Microporous Membranes Based on Electro-Conducting Polymers

Microporous membranes were prepared from polyaniline-diluent systems by exploiting the thermally induced phase separation, using three polymer concentrations, two quenching temperatures, and different extraction conditions. Both binodal and spinodal curves of polyaniline-diluent systems were determined by differential scanning calorimetry. The membrane morphology was determined by scanning electron microscopy and optical microscopy. Phase separation may be carried out by nucleation and growth mechanism under the conditions used in this study. A closed cell structure was obtained for the PANI-concentrated samples. In contrast, an open structure composed of strings of small beads resulted for the PANI-dilute samples. It was also found that the membrane morphology varied with the extraction temperature and extractants. A great effect of coarsening, attributed to the extremely low molecular weight of PANI and mild quenching temperature, gave large pores in the final membrane structure.

Mechanical properties, Payne effect, and Mullins effect of thermoplastic vulcanizates based on high-impact polystyrene and styrene–butadiene rubber compatibilized by styrene–butadiene–styrene block copolymer

Thermoplastic vulcanizates (TPVs) based on high-impact polystyrene (HIPS)/styrene–butadiene rubber (SBR) blends were prepared by dynamic vulcanization technique, and the TPVs were compatibilized by styrene–butadiene–styrene block copolymer (SBS). Experimental results indicate that SBS had a good compatibilization effect on the HIPS/SBR TPVs. A rubber process analyzer reveals that elastic modulus increased with increasing frequency and increasing SBR content in the TPVs led to obvious decrease in elastic modulus. A softening phenomenon could be observed in the stress–stretch curves of HIPS/SBR and HIPS/SBS/SBR TPVs during the uniaxial loading–unloading cycles. Compatibilized HIPS/SBR TPV had the relatively lower stress and internal friction loss.

Thermoplastic elastomers based on high-density polyethylene and waste ground rubber tire composites compatibilized by styrene–butadiene block copolymer:

Thermoplastic elastomers (TPEs) based on high-density polyethylene (HDPE)/waste ground rubber tire (WGRT) powder composites were prepared by melt compounding, and the composites were compatibilized by styrene–butadiene–styrene block copolymer (SBS). The effects of the SBS compatibilizer on mechanical properties, morphological properties and the Mullins effect of the composites were investigated systemically. Experimental results indicated that SBS had a good compatibilization effect on the HDPE/WGRT composites. Compared with HDPE/WGRT composites, the tensile strength and the elongation at break went through maximum values at a compatibilizer resin content of 12 phr. Morphological study showed that the interface interaction of the HDPE/WGRT composites compatibilized by SBS was strong, which contributed to the significantly improved mechanical properties. The Mullins effect results showed that the softening appeared after the first loading of the HDPE/WGRT and HDPE/SBS/WGRT composites, the maximum stress decreased at the later cycles, and the residual deformations in uniaxial loading–unloading cycles of the HDPE/SBS/WGRT sample were lower than those of the HDPE/WGRT sample, indicating that the elasticity of the HDPE/SBS/WGRT TPE was improved.

Zinc Dimethacrylate-Reinforced Thermoplastic Vulcanizates Based on Chlorinated Polyethylene Rubber/Ethylene-Vinyl Acetate Copolymer

A chlorinated polyethylene rubber (CPE)/ethylene-vinyl acetate copolymer (EVA) (weight ratio = 70/30) thermoplastic vulcanizate (TPV) was prepared by dynamic vulcanization, with the TPV being reinforced by various amounts of zinc dimethacrylate (ZDMA). The effects of ZDMA content on the mechanical and morphological properties of the TPVs were investigated. Experimental results indicated that dynamically vulcanized CPE/EVA blends without ZDMA showed an elastomeric behavior when the CPE/EVA weight ratio ranged from 90/10 to 50/50. The mechanical properties of dynamically vulcanized CPE/EVA blends were enhanced remarkably by the incorporation of ZDMA, especially when the ZDMA content was 5 phr. The fracture surface morphology of the reinforced CPE/EVA TPVs was relatively rough and drawn fibers could be found clearly. There were many ZDMA particles dispersed on the etched surface of the reinforced CPE/EVA TPVs with diameters of below about 10 μm. Energy dispersive X-ray spectrometer (EDS) results showed that the ZDMA particles were coated with CPE, the ZDMA particles being surrounded by a large number of small crosslinked CPE particles with diameters of 1 μm.

Dynamically Vulcanized Styrene-Butadiene Rubber/Ethylene-Vinyl Acetate Copolymer/High Impact Polystyrene Blends Compatibilized by Styrene-Butadiene-Styrene Block Copolymer

Compatibilized Cis-1,3-butadiene rubber (BR)/ethylene-vinyl acetate copolymer (EVA)/high-impact polystyrene (HIPS) thermoplastic blend vulcanizates (TPVs) were prepared by dynamic vulcanization, with TPVs being compatibilized by styrene-butadiene-styrene (SBS) block copolymer. The effects of SBS compatibilizer on mechanical, dynamic mechanical, and morphological properties of TPVs were investigated systematically. Experimental results indicated that the dynamically vulcanized BR/HIPS blends did not show an elastomeric behavior when the BR/HIPS blend ratio ranged from 30:70 to 70:30. However, the dynamically vulcanized BR/EVA/HIPS blends compatibilized with SBS showed obvious elastomeric behavior; thus SBS had a good compatibilization effect on BR/EVA/HIPS TPVs. The fractured surface morphology of compatibilized BR/EVA/HIPS TPV was relatively smooth, the interface interaction was strong, and there was no obvious micro-phase separation. BR particles were dispersed evenly in the etched surfaces of BR/EVA/SBS/HIPS TPV. A rubber process analyzer revealed that the storage modulus decreased significantly with increasing strain and the incorporation of compatibilizer SBS in TPVs weakened the Payne effect; the loss modulus showed a pronounced peak and tanδ increased continuously with increasing strain.

Thermoplastic Elastomers Based on High-Impact Polystyrene/Waste Styrene Butadiene Rubber Powder Blends Enhanced by Styrene–Butadiene–Styrene Block Copolymer and Aromatic Oil

Thermoplastic elastomers (TPEs) based on high-impact polystyrene (HIPS)/waste styrene–butadiene rubber powder (WSBRP) blends were prepared by melt-compounding; they were enhanced by incorporation of styrene–butadiene–styrene block copolymer (SBS) and aromatic oil (AO). The effects of SBS and AO dosage on the mechanical properties, Mullins effect and morphological properties of the blends were investigated. Experimental results showed that the incorporation of SBS and AO in the HIPS/WSBRP blends could improve the mechanical properties significantly. Compared with that of HIPS/WSBRP blends, the elongation at break had a maximum value with 9 phr SBS and 15 phr AO loading, being improved by about 220%. The Mullins effect results showed that a softening effect appeared obviously after the first loading–unloading cycle, while the residual deformation and internal friction loss of the HIPS/SBS/AO/WSBRP TPEs were much lower than those of the HIPS/WSBRP blends, indicating the improvement of elasticity.

Water-swellable thermoplastic vulcanizates based on ethylene–vinyl acetate copolymer/chlorinated polyethylene/cross-linked sodium polyacrylate/nitrile butadiene rubber blends:

A novel water-swellable rubber (WSR) has been prepared by dynamically vulcanized ethylene–vinyl acetate copolymer (EVA)/chlorinated polyethylene (CPE)/nitrile butadiene rubber (NBR) blends where the cross-linked poly(sodium acrylate) (CPNaAA) was used as a super water-absorbent resin and dispersed in the NBR rubber. The mechanical properties, water-swelling behavior, weight loss and crystallization behavior of the prepared WSRs were investigated systemically. When the CPNaAA content was 20 phr above, the increase in CPNaAA dosage contributed to the decrease in mechanical properties. However, the WSRs showed strong water-swelling behaviors and the water-swelling ratio of WSRs with 50 phr CPNaAA was 669.3% at 120 h. The WSRs with 60 phr CPNaAA showed high water-swelling rate and achieved the equilibrium swelling at about 566.3% in 23 h. The secondary and third water-swelling behaviors of WSRs showed significantly rapid equilibrium swelling and remarkable decrease in weight loss. X-ray diffraction results revealed the increase in CPNaAA content would result in the reduction of crystalline structure content in EVA. Morphological study of etched surface showed that the CPNaAA particles were dispersed evenly in the WSRs and coated with cross-linked NBR rubber; moreover, field-emission scanning electron microscopic graphs showed the crystalline structure of EVA and clusters of flakes were dispersed on the etched surface of WSRs.

Dynamically Vulcanized Nitrile Butadiene Rubber/Acrylonitrile-Butadiene-Styrene Terpolymer Blends Compatibilized by Styrene-Butadiene-Styrene Block Copolymer

Thermoplastic vulcanizates (TPVs) based on nitrile butadiene rubber (NBR)/ acrylonitrile-butadiene-styrene (ABS) blends were prepared by dynamic vulcanization, and then compatibilized by styrene-butadiene-styrene block copolymer (SBS). The effects of SBS compatibilizer on mechanical properties, Mullins effect, and morphological properties of the TPVs were investigated systematically. Experimental results indicated that SBS had an excellent compatibilization effect on the dynamically vulcanized NBR/ABS TPVs. The tensile strength increased from 9.4 to 15.8 MPa and the elongation at break went through a maximum value when the dosage of SBS was only 1 phr. Mullins effect results showed that the compatibilized NBR/ABS TPV had relatively lower residual deformation and internal friction loss than the NBR/ABS TPV, indicating the improvement of elasticity. Morphology studies showed that the vulcanized NBR particles were dispersed evenly in the TPVs and the dimensions of NBR particles were decreased remarkably with the incorporation of SBS compatibilizer.