Although a number of investigations have been devoted to the analysis of silica or carbon black filled elastomer networks,little work has been done on the reinforcement of CaCO_3 filled elastomer network.In this work,...Although a number of investigations have been devoted to the analysis of silica or carbon black filled elastomer networks,little work has been done on the reinforcement of CaCO_3 filled elastomer network.In this work,the reinforcement of polydimethylsiloxane(PDMS)network by using CaCO_3 nano-particles was investigated.We have found a simultaneous increase of tensile strength,modulus and elongation with the increase in nano-CaCO_3 content,which suggests that nano- CaCO_3 particles can indeed be used as a reinforcing agent,just like silica or carbon black.Interestingly,the tensile strength, modulus and elongation were seen to leave off for the first time when the content of nano-CaCO_3 particles reaches to 80%. PDMS also showed an enhanced elastic modulus and storage modulus with the increase in nano-CaCO_3 content,particularly for samples with high nano-CaCO_3 content.SEM was used to investigate the dispersion of the filler in PDMS matrix.A better dispersion was found for samples with high nano-CaCO_3 content.A great increase of viscosity was found for samples with higher filler content,which is considered to be the reason for the good dispersion thus the reinforcement,because high viscosity will be helpful for breaking the agglomerates of fillers into small size particles under effect of shear.Our work provides a new way for the reinforcement of elastomer by using an adequate amount of nano-CaCO_3 particles instead of a small quantity of silica,which is not only economically cheap but also very effective.展开更多
Metallocene-catalyzed short chain branched polyethylene (SCBPE) was blended with LDPE, HDPE, PS, EPDM and iPP in the weight proportions of 80 and 20. The crystallization and mechanical properties of these blends were ...Metallocene-catalyzed short chain branched polyethylene (SCBPE) was blended with LDPE, HDPE, PS, EPDM and iPP in the weight proportions of 80 and 20. The crystallization and mechanical properties of these blends were studied by PLM, DSC and DMA. It has been observed in PLM that SCBPE/LDPE, SCBPE/HDPE and SCBPE/EPDM can form band spherulites whose band width and size are both smaller than that of the pure SCBPE. Tiny crystallites are observed in the completely immiscible SCBPE/PS blend. The crystallites in SCBPE/iPP are very small and only irregular spherulites are seen. The crystallization kinetics and mechanical properties of SCBPE are greatly affected by the second polyolefin, but in a different way, depending on the phase behavior and the modulus of the second components. SCBPE may be phase miscible in the melt with HDPE, LDPE and EPDM and co-crystallize together with HDPE or LDPE during cooling. A big change of crystal morphology and crystallization kinetics is seen in SCBPE/iPP blend compared with pure SCBPE and the lowest tandelta is also seen for this system. DMA results show that the tensile modulus of the blends has nothing to do with phase behavior, but only depends on the modulus of the second component.展开更多
A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxida...A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.展开更多
基金This work was supported by the National Natural Science Foundation of China(Nos.20490220,20394006)the Special Funds for Major State Basic Research Projects of China(No.2003CB615600)also partly supported by Ministry of Education as a key project(No.104154)
文摘Although a number of investigations have been devoted to the analysis of silica or carbon black filled elastomer networks,little work has been done on the reinforcement of CaCO_3 filled elastomer network.In this work,the reinforcement of polydimethylsiloxane(PDMS)network by using CaCO_3 nano-particles was investigated.We have found a simultaneous increase of tensile strength,modulus and elongation with the increase in nano-CaCO_3 content,which suggests that nano- CaCO_3 particles can indeed be used as a reinforcing agent,just like silica or carbon black.Interestingly,the tensile strength, modulus and elongation were seen to leave off for the first time when the content of nano-CaCO_3 particles reaches to 80%. PDMS also showed an enhanced elastic modulus and storage modulus with the increase in nano-CaCO_3 content,particularly for samples with high nano-CaCO_3 content.SEM was used to investigate the dispersion of the filler in PDMS matrix.A better dispersion was found for samples with high nano-CaCO_3 content.A great increase of viscosity was found for samples with higher filler content,which is considered to be the reason for the good dispersion thus the reinforcement,because high viscosity will be helpful for breaking the agglomerates of fillers into small size particles under effect of shear.Our work provides a new way for the reinforcement of elastomer by using an adequate amount of nano-CaCO_3 particles instead of a small quantity of silica,which is not only economically cheap but also very effective.
基金This work was supported by the China National Distinguished Young Investigator Fund (No. 29925413) and the NationalNatural Science Foundation of China (No.20274028).
文摘Metallocene-catalyzed short chain branched polyethylene (SCBPE) was blended with LDPE, HDPE, PS, EPDM and iPP in the weight proportions of 80 and 20. The crystallization and mechanical properties of these blends were studied by PLM, DSC and DMA. It has been observed in PLM that SCBPE/LDPE, SCBPE/HDPE and SCBPE/EPDM can form band spherulites whose band width and size are both smaller than that of the pure SCBPE. Tiny crystallites are observed in the completely immiscible SCBPE/PS blend. The crystallites in SCBPE/iPP are very small and only irregular spherulites are seen. The crystallization kinetics and mechanical properties of SCBPE are greatly affected by the second polyolefin, but in a different way, depending on the phase behavior and the modulus of the second components. SCBPE may be phase miscible in the melt with HDPE, LDPE and EPDM and co-crystallize together with HDPE or LDPE during cooling. A big change of crystal morphology and crystallization kinetics is seen in SCBPE/iPP blend compared with pure SCBPE and the lowest tandelta is also seen for this system. DMA results show that the tensile modulus of the blends has nothing to do with phase behavior, but only depends on the modulus of the second component.
文摘A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.
