The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. T...The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed. That is, crystallization during polymerization occurs below 204 ℃ and the crystallization properties of pCBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP （Tp） from 204 ℃, and the crystallization properties of pCBT are dominated by cooling stage; only polymerization is performed above 212 ℃. Moreover, quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization. On the contrary, the crystal size distributions become wider above 204 ℃ of Tp and lead to obvious double melting peaks during heating scan. These efforts provide a very useful guide for the related investigation and application of CBT.展开更多
Core-shell structured polyacrylic（named CSSP） impact modifiers consisting of a rubbery poly（n-butyl acrylate） core and a rigid poly（methyl methacrylate） shell with a size of about 353 nm were prepared by seed em...Core-shell structured polyacrylic（named CSSP） impact modifiers consisting of a rubbery poly（n-butyl acrylate） core and a rigid poly（methyl methacrylate） shell with a size of about 353 nm were prepared by seed emulsion polymerization. The CSSP modifiers with different core-shell weight ratios（90/10, 85/15, 80/20, 75/25, 70/30, 65/35 and 60/40） were used to modify the toughness of poly（butylene terephthalate）（PBT） by melt blending. It was found that the polymerization had a very high instantaneous conversion（ 95.7%） and overall conversion（99.7%）. The morphology of the core-shell structure was confirmed by means of transmission electron microscopy. Scanning electron microscopy was used to observe the morphology of the fractured surfaces. Differential scanning calorimeter was used to study the crystallization behaviors of PBT/CSSP blends. The dynamic mechanical analyses of PBT/CSSP blends showed two merged transition peaks of PBT matrix, with the presence of CSSP core-shell structured modifier, that were responsible for the improvement of PBT toughness. The results indicated that the notch impact strength of PBT/CSSP blends with a core-shell weight ratio of 75/25 was almost 8.64 times greater than that of pure PBT, and the mechanical properties agreed well with the SEM observation.展开更多
从聚丁二酸丁二醇酯(PBS)的环状低聚物中分离提纯出了PBS的环状二聚物〔cyclic dimer of poly(butylenesuccinate),CDBS〕,采用核磁、质谱对该环状二聚物进行了表征,研究表明,通过分离纯化得到了纯度高的PBS的环状二聚物。以纯化的CDBS...从聚丁二酸丁二醇酯(PBS)的环状低聚物中分离提纯出了PBS的环状二聚物〔cyclic dimer of poly(butylenesuccinate),CDBS〕,采用核磁、质谱对该环状二聚物进行了表征,研究表明,通过分离纯化得到了纯度高的PBS的环状二聚物。以纯化的CDBS为原料、十二醇为初始剂、辛酸锡作催化剂,采用开环聚合的方法合成了PBS,采用核磁、红外光谱对合成的PBS的结构进行了表征,并研究了开环聚合温度、聚合时间以及催化剂用量对PBS的分子量、单体转化率的影响,结果表明,开环反应温度220℃左右,反应3 h,PBS的相对分子质量(简称分子量,下同)可达到63 300,与直接酯化-缩聚法相比,采用开环聚合法能提高PBS的制备效率。展开更多
基金financially supported by the National Natural Science Foundation of China(No.21364004)Gansu Province University Fundamental Research FundsDoctor Research Fund of Lanzhou University of Technology,China
文摘The correlation between ring-opening polymerization （ROP） of cyclic butylene terephthalate （CBT） and crystallization of polymerized CBT （pCBT） strongly affected the final properties of pCBT and its composites. The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed. That is, crystallization during polymerization occurs below 204 ℃ and the crystallization properties of pCBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP （Tp） from 204 ℃, and the crystallization properties of pCBT are dominated by cooling stage; only polymerization is performed above 212 ℃. Moreover, quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization. On the contrary, the crystal size distributions become wider above 204 ℃ of Tp and lead to obvious double melting peaks during heating scan. These efforts provide a very useful guide for the related investigation and application of CBT.
基金financially supported by Program for Changjiang Scholars and Innovative Research Team in University-IRT13060Key Lab for Micro-and Nano-Scale Boron Nitride Materials in Hebei Province
文摘Core-shell structured polyacrylic（named CSSP） impact modifiers consisting of a rubbery poly（n-butyl acrylate） core and a rigid poly（methyl methacrylate） shell with a size of about 353 nm were prepared by seed emulsion polymerization. The CSSP modifiers with different core-shell weight ratios（90/10, 85/15, 80/20, 75/25, 70/30, 65/35 and 60/40） were used to modify the toughness of poly（butylene terephthalate）（PBT） by melt blending. It was found that the polymerization had a very high instantaneous conversion（ 95.7%） and overall conversion（99.7%）. The morphology of the core-shell structure was confirmed by means of transmission electron microscopy. Scanning electron microscopy was used to observe the morphology of the fractured surfaces. Differential scanning calorimeter was used to study the crystallization behaviors of PBT/CSSP blends. The dynamic mechanical analyses of PBT/CSSP blends showed two merged transition peaks of PBT matrix, with the presence of CSSP core-shell structured modifier, that were responsible for the improvement of PBT toughness. The results indicated that the notch impact strength of PBT/CSSP blends with a core-shell weight ratio of 75/25 was almost 8.64 times greater than that of pure PBT, and the mechanical properties agreed well with the SEM observation.
