Effects of bifunctional chain extender on the crystallinity and the thermal stability of PET were studied in this work. Results of Infrared substractive spectrum indicated that one oxazoline ring of 2,2’-bis(2-oxazol...Effects of bifunctional chain extender on the crystallinity and the thermal stability of PET were studied in this work. Results of Infrared substractive spectrum indicated that one oxazoline ring of 2,2’-bis(2-oxazoline) (BOZ) reacted with one carboxyl in PET to generate a blocked PET chain with an oxazoline ring, which then reacted with one carboxyl in second PET to form an extended chain. The intrinsic viscosity (IV) of extended PET would increase from 0.61 of initial PET to 0.80 when the addition of BOZ was 0.52 wt%. Furthermore, when BOZ was used with hydroxyl-addition-type chain extender 2,2’-(1,4-phenyl)bis(4H-3,1-benzoxazin-4-one) (BNZ) or chain end modifier phthalic anhydride (PA), IV of chain extended PET would be 0.83 and 0.97 respectively. DSC results showed that chain extending would result in a decrease in crystallinity of PET. Comparing with initial PET, the intrinsic viscosity loss of the chain extended products would be smaller after multi-melting processing.展开更多
To improve the understanding on the failure behavior and its anchoring effect of weak-broken rock slope,the rock of grade IV according to China is taken as reference prototype,and a series of model tests were carried ...To improve the understanding on the failure behavior and its anchoring effect of weak-broken rock slope,the rock of grade IV according to China is taken as reference prototype,and a series of model tests were carried out in laboratory.These tests can be divided into two categories,that is,with bolt reinforcement and without bolt reinforcement.In which,the stability of slope reinforced with different bolt diameter,different anchor length and different space are studied.The test results show that the collapse of slope is the combination of tension failure at the top and the compression-shearing failure at the bottom of the slope,and its failure process presents progressive characteristics.The contributions of bolt reinforcement are mainly reflected by the aspects of shear resistance,crack resistance and anti-extension.The reinforcement of blot not only can improve the vertical bearing capacity before failure,but also can reduce the vertical settlement and allow greater lateral rock wall deformation;what is more,the stress concentration degree in rock mass can be dispersed,which do help to improve the stability of slope rock mass.展开更多
文摘Effects of bifunctional chain extender on the crystallinity and the thermal stability of PET were studied in this work. Results of Infrared substractive spectrum indicated that one oxazoline ring of 2,2’-bis(2-oxazoline) (BOZ) reacted with one carboxyl in PET to generate a blocked PET chain with an oxazoline ring, which then reacted with one carboxyl in second PET to form an extended chain. The intrinsic viscosity (IV) of extended PET would increase from 0.61 of initial PET to 0.80 when the addition of BOZ was 0.52 wt%. Furthermore, when BOZ was used with hydroxyl-addition-type chain extender 2,2’-(1,4-phenyl)bis(4H-3,1-benzoxazin-4-one) (BNZ) or chain end modifier phthalic anhydride (PA), IV of chain extended PET would be 0.83 and 0.97 respectively. DSC results showed that chain extending would result in a decrease in crystallinity of PET. Comparing with initial PET, the intrinsic viscosity loss of the chain extended products would be smaller after multi-melting processing.
基金supported by the National Natural Science Foundation of China(Grant No.40672184)the Open Foundation of the Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education of China.
文摘To improve the understanding on the failure behavior and its anchoring effect of weak-broken rock slope,the rock of grade IV according to China is taken as reference prototype,and a series of model tests were carried out in laboratory.These tests can be divided into two categories,that is,with bolt reinforcement and without bolt reinforcement.In which,the stability of slope reinforced with different bolt diameter,different anchor length and different space are studied.The test results show that the collapse of slope is the combination of tension failure at the top and the compression-shearing failure at the bottom of the slope,and its failure process presents progressive characteristics.The contributions of bolt reinforcement are mainly reflected by the aspects of shear resistance,crack resistance and anti-extension.The reinforcement of blot not only can improve the vertical bearing capacity before failure,but also can reduce the vertical settlement and allow greater lateral rock wall deformation;what is more,the stress concentration degree in rock mass can be dispersed,which do help to improve the stability of slope rock mass.
