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 共查询到19条相似文献,搜索用时 125 毫秒
1.
固相缩聚共聚酯的熔融行为和结晶速率研究   总被引:1,自引:0,他引:1  
通过固相缩聚合成了两种不同结构的高分子量共聚酯,研究了样品的熔融行为和结晶速率。研究发现,共聚酯的熔融峰随着固相聚合温度和时间的变化而与纯PET有明显的差别,共聚酯泊结晶速率与慢于纯PET的结晶速率。  相似文献   

2.
阻燃性液晶共聚酯/PET共混物的热氧化降解动力学研究   总被引:1,自引:0,他引:1  
本文利用实验室合成的一种阻燃性的液晶共聚酯与PET共混,采用热重分析法对共混物进行了热氧化降解动力学研究,发现该液晶共聚酯的加入对PET的降解影响不大。  相似文献   

3.
熔融—固相缩聚法中固相聚合对聚乳酸合成的影响   总被引:11,自引:0,他引:11  
以L-乳酸单体为原料,熔融-固相缩聚法合成了聚乳酸,重点研究了固相聚合的工艺条件。结果表明,绝对压力60Pa,氯化亚锡为催化剂,分段控温,可使聚乳酸的粘均分子量提高到固相聚合反应前的5.3倍。通过对固相聚合产物的结晶度和熔点的分析,探讨地固相聚合的机理。  相似文献   

4.
固相聚合PET的结晶性能研究——(Ⅰ)等温结晶动力学   总被引:2,自引:0,他引:2  
本文采用DSC方法研究了几种不同缩聚催化体系固相聚合PET的等温结晶动力学。结果表明,固相聚合PET的结晶速率常数(k)和t_(max)对等温结晶温度(T_c)和分子量的依赖关系与熔融缩聚PET相同。采用适合国情的新型复合型缩聚催化体系合成的两种固相聚合PET在分子量、结晶速率诸方面均能符合瓶用树脂的要求。结果也表明,几种固相聚合PET主期结晶阶段Avrami指数n值均在2—3之间。并且,在许多情况下,n值不是常数,说明存在二次结晶现象,t_n与t_(max)之间存在线性关系,在某些情况下,没有观察到二次结晶现象。  相似文献   

5.
含介晶基因的半刚性共聚酯的合成及其性能研究   总被引:2,自引:1,他引:1  
通过介晶单体4,4’联苯分别与对苯二甲酰氯及4,4’(对苯二甲酰氧基)二苯甲酰氯进行高温溶液缩聚反应合成了两种含介晶基团的半刚性共聚酯BHHBP/TPC与BHHBP/TOBC。利用DSC、TG-DTA、偏光显微镜和X射线衍射等手段对介晶体BHHBP与共酯的相变行为以及共聚酯的热分解动力学及结晶性能进行了研究。结果表明,两共聚酯均为结晶性聚合物,其中BHHBP/TOBC具有向列相液晶相存在;共聚酯B  相似文献   

6.
由TGA测定了通过先酯化、再缩聚方法合成的PET-PTT共聚酯(以PET,PTT作对照)在一定升温速率下氮气及空气气氛中的热失重行为。采用Friedman和Chang方法研究了样品的降解动力学。研究表明,在氮气和空气气氛中PET-PTT共聚酯的热稳定性都介于PET和PTT之间,且随着PET链段单元含量的增加,共聚酯的热稳定性提高。气氛对聚合物降解行为的影响很大,在空气中PET-PTT共聚酯的起始分解温度下降了近50℃,且在空气气氛中存在两个降解阶段,空气中的氧在降解的第一阶段起了催化剂的作用。  相似文献   

7.
用溶液缩聚法合成了含柔性间隔基的嵌段热致液共聚酯。由于在TCE/Py溶液中共聚酯溶解度较小及溶液中副反应显著,合成的嵌段共聚酯特性粘度都小于0.30dL/g,DTA和偏光显微镜对嵌段共聚酯的液晶性和相转变研究结果表明,所有嵌段共聚酯都为向列相热致液共聚酯。  相似文献   

8.
间苯二甲酸共聚酯的结晶特性   总被引:2,自引:0,他引:2  
研究了聚对苯二甲酸乙二醇酯(PET)分子链中引入间苯二甲酸(IPA)的无规共聚酯(IPET)的非等温结晶动力学和等温结晶时球晶的生长和形态。结果表明,共聚酯的结晶温度随IPA含量的增加而升高,玻璃化转变温度、熔点随IPA含量的增加而降低;IPA的引入使IPET的结晶速率及球晶生长速率明显降低,但对球晶的形态及生长机理并无明显的影响。  相似文献   

9.
锌-铬合金电沉积工艺参数对镀层中铬含量的影响   总被引:1,自引:0,他引:1  
1前言锌离子和三价铬离子的电化学动力学特性差异很大,Cr3+在水溶液中和水形成很稳定的内轨型配体,反应速度常数仅为1.8×10-6,而Zn2+的反应速度常数高达3×107,这使Cr3+沉积的过电位很负,很难和锌离子一起共沉积。国内研究工作[1]仅在氯...  相似文献   

10.
熔融-固相缩聚法中固相聚合对聚乳酸合成的影响   总被引:2,自引:0,他引:2  
以L 乳酸单体为原料 ,熔融 -固相缩聚法合成了聚乳酸 ,重点研究了固相聚合的工艺条件。结果表明 ,绝对压力 60Pa ,氯化亚锡为催化剂 ,分段控温 ,可使聚乳酸的粘均分子量提高到固相聚合反应前的 5 3倍。通过对固相聚合产物的结晶度和熔点的分析 ,探讨了固相聚合的机理。  相似文献   

11.
MAA存在下VAc/BA核壳乳液聚合动力学研究   总被引:1,自引:0,他引:1  
研究了功能性单体MAA的加入方式,乳化剂量和单体的加料速率等因素对MAA存在下VAc/BA核壳乳液聚合动力学的影响,同时探讨了动力学对胶粒形态变化和羧基分布的影响,研究表明,功能性单体MAA的加入方式不同会影响到壳层聚合阶段的溶胀、因而,使形成壳层的机理不同,乳化剂量和加料速率分别通过影响胶粒数和总体反应速率系数而对胶粒溶胀和壳层聚合反应产生影响。由于胶粒内聚合物浓度高、粘度大、因而胶粒形态变化受动力学影响甚大,羧基分布主要是由动力学确定的。  相似文献   

12.
Transmission electron microscopy (TEM) has been used to characterize non-periodic layer crystallites in thermotropic random copolyesters composed of 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. The crystallites are most clearly observed when imaged in the equatorial reflection, indicating that they are associated with intermolecular ordering. The crystallites appear to be platelets with their thin axis parallel to the molecular chain axis. Crystallite growth is highly dependent on thermal history and occurs to a significant extent during the early stages of annealing above the glass-transition temperature in the solid state. Long-term annealing of the copolymers results in an increase in the number of crystallites, as well as sharpening the diffraction pattern. The extent of lateral development of the ordered regions also depends on the degree of polymerization (DP), being greater for a copolymer of lower DP.  相似文献   

13.
Cd-Ni filtercakes are produced continuously at the third purification step in the electrolytic production of zinc in the National Iranian Lead and Zinc Company (NILZ) in northwestern Iran. In this research, the dissolution kinetics of cadmium from Cd-Ni residues produced in NILZ plant has been investigated. Hence, the effects of temperature, sulfuric acid concentration, particle size and stirring speed on the kinetics of cadmium dissolution in sulfuric acid were studied. The dissolution kinetics at 25-55 degrees C and t相似文献   

14.
Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100–50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm?1 can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm?1 due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm?1 due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.  相似文献   

15.
The interracial phenomena of the Sn-Pb solder droplet on and needle-like AuSn4 are formed at the interface after Au/Ni/Cu pad are investigated. A continuous AuSn2 the liquid state reaction (soldering). The interracial reaction between the solder and Au layer continues during solid state aging with AuSn4 breaking off from the interface and felling into the solder. The kinetics of Au layer dissolution and diffusion into the solder during soldering and aging is analyzed to elucidate intermetallic formation mechanism at the solder/Au pad interface. The concentration of Au near the solder/pad interface is identified to increase and reach the solubility limit during the period of liquid state reaction. During solid state reaction, the thickening of Au-Sn compound is mainly controlled by element diffusion.  相似文献   

16.
聚对苯二甲酸丁二酯的固相缩聚研究   总被引:4,自引:0,他引:4  
本文在不同的固相缩聚反应温度和时间的条件下研究了PBT固相缩聚反应动力学,测定了反应条件下的表观活化能,认为扩散和化学反应是PBT分子量增长的两个主要控制因素。在低温下反应主要由化学控制,而在高温下反应主要由扩散控制,此时的增长曲线偏离二级反应方程。同时,本文对所获得的固相缩聚的PBT样品的分子量分布、熔融行为、结晶度和晶粒尺寸进行了研究,得到了一些有规律的结论。  相似文献   

17.
研究了对苯二甲酸乙二醇酯-己内酯共聚酯(TCL)溶液和本体的荧光光谱。结果表明,此共聚酯的荧光光谱与聚对苯二甲酸乙二醇酯(PET)的荧光光谱有所差别。TCL在稀溶液中能形成分子内缔合物。在TCL本体同时出现较强的单分子荧光和缔合物荧光,ET含量较低的TCL在室温下还能观察到较强的磷光谱带。  相似文献   

18.
间苯二甲酸对嵌段共聚酯结构和性能的影响   总被引:1,自引:0,他引:1  
本文通过X光衍射,DSC,SAXS等方法,考察了间苯二甲酸的含量对聚对苯二甲酸乙二醇-聚己二酸乙二醇多嵌段共聚酯结构和性能的影响,发现合成时间苯二甲酸的加入,使共聚酯的Wa,x,Tm,Lnkl均下降,同时,力学性能也下降,但间苯二甲酸含量为10%的共聚酯的力学性能最佳。  相似文献   

19.
用熔融缩聚法合成了一系列聚(丁二酸丁二醇酯癸二酸丁二醇酯)的无规共聚物(PBSu-co-PBSe)。通过核磁共振(1H-NMR),差示扫描量热(DSC),热重分析(TGA),X射线衍射(XRD)和酶降解测试等方法表征了材料的结构与性能。XRD测试结果表明,共聚酯的晶体结构随着癸二酸含量的增加发生了改变,并产生了共结晶行为;DSC分析得出,随着PBSe组分在共聚酯中含量的增大,产物的熔点(Tm)由84.8℃降低至46.7℃,然后升高至55.9℃,玻璃化温度(Tg)单调降低至-58.7℃;TGA分析表明,癸二酸的引入提高了聚酯的热稳定性;酶降解测试得出产物具有良好的生物降解性,当PBSe占共聚酯含量的40%时,产物具有最快的降解速率。  相似文献   

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