【作者】 白春燕；

【导师】 王玉忠； 丁颂东；

【作者基本信息】 四川大学 ， 高分子化学与物理， 2007， 硕士

【摘要】 聚对二氧环己酮(PPDO)是一种线型脂肪族聚酯,具有良好的生物相容性、生物降解性和优异的力学性能,除了可用于制造手术缝合线、骨板和组织修复材料等医用材料外,还有望用于制造薄膜、发泡,板材,粘合剂、涂饰剂、无纺布及一次性卫生用品等材料。但其热稳定性较差,在140℃时就开始发生热降解,与其熔点(110℃)非常接近,使得加工温度范围较窄。且在加工过程中由于热降解,分子量及熔体粘度均会显著降低,不利于成型加工;另外, PPDO极易水解,即使在空气中也会迅速降解,这对其作为环境友好材料使用是极为不利的,因为,作为材料使用,至少必须保证其在加工、运输、贮存及使用过程中是稳定的。因此,提高PPDO的热稳定性和水解稳定性,是其能否得到广泛应用的关键问题。本文针对PPDO的热降解机理,通过封端、扩链、扩链和封端相结合的方法提高其热稳定性,同时研究改性后聚合物的水解稳定性。对PPDO用自制的单异氰酸酯进行封端。用2,4-甲苯二异氰酸酯(TDI)与等摩尔正己醇反应制备单异氰酸酯,用盐酸-二正丁胺滴定法、IR和1HNMR谱进行了分析和表征,证明所得产物为单异氰酸酯。以特性粘数为0.25dL/g的PPDO与单异氰酸酯封端剂反应,并对封端后的PPDO进行了IR和1HNMR表征,证明反应后的产物为封端产物;以特性粘数为1.20dL/g的PPDO均聚物与单异氰酸酯进行封端反应,用等温和非等温TG方法,研究了PPDO和封端PPDO在空气氛中的热降解行为,分别采用Kissinger方法和Friedman方法,计算了在空气氛中的热降解活化能,PPDO分别为91和81kJ/mol,封端PPDO分别为160和149kJ/mol。采用DSC和WAXD分析方法对PPDO和封端PPDO的结晶性能与形态进行了研究。由DSC测得PPDO和封端PPDO的结晶度分别为48%和19%,说明封端使PPDO的结晶度显著下降。对PPDO用1,6-六亚甲基二异氰酸酯(HDI)进行扩链。通常PPDO是在有机金属化合物存在下,PDO单体在80℃下开环聚合3-4天制备而成,特性粘数为1dL/g左右。本文以SnOct2为催化剂, PDO单体在125℃下聚合反应3h后加入1,6-六亚甲基二异氰酸酯(HDI)进行扩链,得到高分子量扩链产物PPDO-HDI。整个聚合过程时间不超过5h,特性粘数接近2dL/g,用该种方法制备PPDO时间短,在熔点以上进行反应,易于放大,合成的PPDO特性粘数高。采用非等温TG方法研究了PPDO和PPDO-HDI的热性能,PPDO与PPDO-HDI的起始热分解温度分别为223℃和240℃,PPDO-HDI的热稳定性有所提高。由DSC测得PPDO和PPDO-HDI的结晶度分别为60%和33%,扩链后结晶度显著下降。力学性能研究表明PPDO和PPDO-HDI拉伸强度和断裂伸长率都相近,PPDO分别为36MPa和401%,PPDO-HDI分别为36MPa和464%。对扩链后的PPDO再进行封端。对PPDO-HDI分别选用自制的单异氰酸酯、二环己基碳化二亚胺(DCC)和聚碳化二亚胺(PCD)为封端剂进行封端。采用非等温TG方法研究了PPDO和扩链后再封端PPDO的热稳定性,扩链后再封端的PPDO的热稳定性均得到不同程度的提高,扩链后再用PCD封端(PPDO-HDI-PCD)提高最明显,起始热分解温度由PPDO的223℃增大到264℃。采用DSC测得PPDO, PPDO-HDI-PCD的结晶度分别为60%和38%, PPDO-HDI-PCD的结晶度明显下降。力学性能研究表明PPDO-HDI-PCD的拉伸强度与PPDO相近,断裂伸长率增大,PPDO分别为36MPa和401%,PPDO-HDI-PCD分别为38MPa和612%。PPDO,封端PPDO,PPDO-HDI的降解实验表明,在空气中的稳定性顺序为PPDO﹤封端PPDO,PPDO﹤PPDO-HDI。体外降解实验表明,PPDO和封端PPDO ,PPDO和PPDO-HDI在pH=7.4的磷酸盐缓冲溶液中的降解速率相近。对PPDO-HDI-PCD用拉伸性能随时间的变化考察了其在空气中的稳定性,拉伸实验表明,PPDO-HDI-PCD的稳定性大于PPDO-HDI。更多还原

【Abstract】 Poly(p-dioxanone) is a linear aliphatic polyester which has good biocompatibility, biodegradability and mechanical properties. It has been used in medical field, such as monofilament sutures, bone and tissue fixation devices. Furthermore, PPDO also has a great potentiality for general uses such as films, molded products, laminates, foams, non-woven materials, adhesives and coatings. However, it has a poor thermal stability, the thermal degradation of PPDO is detectable above 140℃which is near to its melting point(110℃), so the temperature range of processing is very narrow. Due to the poor thermal stability, the molecular weight and melt viscosity of PPDO significantly decrease during processing which is a disadvantage for processing. In addition, we find that it could quickly degradation even in air. Therefore, how to enhance the thermal stability and hydrolytic stability of PPDO are very important to the processing and extensive applications of PPDO.According to the thermal degradation mechanism of PPDO, this investigation focused on enhancing thermal stability of PPDO in the melt by end capping and chain extending, studing the hydro-degradation of the end-capped PPDO and chain-extended PPDO at the same time.PPDO was end-capped by mono-isocyanate. The end-capped reagent of mono-isocyanate was prepared through the reaction of toluene-2,4-diisocyanate with equimolar n-hexyl alcohol, and was analysized and characterized by titration, IR and 1HNMR. The end-capped PPDO with low inherent viscosity of 0.25 dL/g was characterized by IR and 1HNMR. The reaction of mono-isocyanate with PPDO ([η]=1.20 dL/g) have been studied. The thermal degradation behavior of end-capped PPDO in air has been investigated by TG. Kissinger method and Friedman method have been used to determine the activation energies. The calculated activation energies were 91, 81 kJ mol-1 for PPDO, and 160, 149kJ mol-1 for end-capped PPDO, respectively. Differential scanning calorimetry (DSC) and wide angle X-ray diffractometry (WAXD) have been utilized to investigate the crystallization and morphology of PPDO and end-capped PPDO. The degrees of crystallinity of PPDO and end capped PPDO by DSC were 48% and 19%, respectively. The melting point of PPDO changed little through end capping. However, the glass transition temperature of end capped PPDO increased to some extent.PPDO was chain extended by hexamethylene diisocyanate(HDI). Usually, PPDO was synthesized through the ring-opening polymerization of p-dioxanone, the reaction time was 3-4 days, the inherent viscosity was around 1dL/g. In this paper, PPDO was prepared though ring-opening polymerization of PDO using SnOct2 as a catalyst at 125℃for 3 hours, followed by an increase in molecular weight through reaction with HDI (the product is PPDO-HDI). This was an easy and simple method for production of high molecular weight PPDO in large scale. The thermal degradation behavior of PPDO-HDI in air has been investigated by TG. The initial decomposition temperature of PPDO and PPDO-HDI were 223℃and 240℃, respectively. The degrees of crystallinity of PPDO and PPDO-HDI by DSC were 60% and 33%, respectively. The mechanical properties of PPDO and PPDO-HDI were studied by tensile testing machine. The results showed that the mechanical properties of PPDO and PPDO-HDI were almost at the same level.PPDO-HDI was end-capped by mono-isocyanate, N,N’-Dicyclohexylcarbodiimid -e(DCC), poly(carbodiimide)(PCD) , respectively. The thermal degradation behavior of PPDO and end-capped PPDO in air has been investigated by TG. The results showed that the thermal stability of end-capped PPDO were higher than that of pure PPDO. Differential scanning calorimetry (DSC) has been utilized to investigate the crystallization of PPDO and PPDO-HDI-PCD (PPDO-HDI end capped by PCD). The degrees of crystallinity of PPDO and PPDO-HDI-PCD by DSC were 60% and 38%, respectively. The mechanical properties of PPDO and PPDO-HDI-PCD were studied by tensile testing machine. The results showed that the tensile strength of PPDO-HDI-PCD was the same as PPDO, but the elongation was enhanced.The degradation tests of PPDO, end-capped PPDO and PPDO-HDI in air at ambient temperature have been performed. The results showed that the stability orders of various PPDO were as followed: PPDO < end-capped PPDO, PPDO < PPDO-HDI. The in-vitro degradation tests of PPDO, end-capped PPDO and PPDO-HDI were carried out in a buffer solution based on hydrogenated sodium phosphate and di-hydrogenated sodium phosphate with an initial pH of 7.4 at 37℃. The results showed that the hydro-stability of end-capped PPDO, PPDO-HDI weren’t enhanced. We investigated the change of mechanical properties to study the stability of PPDO-HDI-PCD in air. The results indicated that the tensile strength and elongation at break of PPDO-HDI-PCD changed slower than that of PPDO.更多还原