成核剂对PET非等温结晶动力学的影响

利用差示扫描量热仪(DSC)研究了滑石粉、苯甲酸钠和离子聚合物Surlyn对聚对苯二甲酸乙二醇酯(PET)非等温结晶行为的影响,并用Ozawa模型计算了非等温结晶动力学参数。结果表明:三种成核剂均是PET的良成核剂,其中苯甲酸钠的成核效果最为显著。与纯PET相比,三种成核剂的加入均使PET的结晶峰温度Tmc向高温偏移,过冷度(Tm-Tmc)明显降低,结晶速率常数K明显增大。纯PET和PET/成核剂共混体系的Ozawa指数n值介于1-4之间,均不为整数,且PET/成核剂共混体系的Ozawa指数n值小于纯PET的n值。     

成核剂对PET/PEN共混体系非等温结晶的影响

采用差示扫描量热法(DSC)研究了三种成核剂苯甲酸钠(SB)、1,3∶2,4-二亚苄基-D-山梨醇(DBS)、碳酸钙(CaCO3)对聚对苯二甲酸乙二醇酯(PET)/聚2,6-萘二甲酸乙二醇酯(PEN)共混体系的非等温结晶动力学的影响。结果表明,在PET/PEN/成核剂共混体系的非等温熔融结晶过程中,随着冷却速率的升高,结晶起始温度、终止温度、结晶峰温度都向低温方向移动,成核剂的加入使得不同速率下PET/PEN的结晶温度明显提高,结晶更为容易,SB、CaCO3、DBS均起到了较好的成核作用。由于次级结晶的存在,采用Ozawa法不能很好地描述PET/PEN/成核剂共混体系的非等温熔融结晶过程;莫志深法能较好地描述体系的非等温熔融结晶过程。     

纳米SiO_2粒子对PET结晶过程的影响

研究了纳米SiO2粒子对PET结晶过程的影响。通过差热分析(DSC),分别研究了改性纳米SiO2对PET的等温结晶和非等温结晶的影响。计算了在不同温度下,不同改性纳米SiO2含量PET的等温结晶动力学方程。结果表明:随着纳米SiO2的加入,可以显著提高PET的结晶性能,Avrami指数n变小,体系发生异相成核。当纳米SiO2的添加量在2％时,体系的结晶能力最好,在所测的5个等温结晶温度中,所有样品在170℃附近的结晶速度最快。     

PP/PET/POE-g-MAH共混合金的等温结晶动力学特性

应用差示扫描量热法(DSC),研究了加入不同份数增容剂POE-g-MAH的PP/PET共混合金及纯PP的等温结晶行为,采用Avrami方程处理等温结晶过程,计算结晶动力学参数。结果表明,随着结晶温度的升高各体系的结晶速率下降,结晶速率常数K、n降低,半结晶时间t1/2延长。同一温度下PET有明显的异相成核作用,提高了基体的结晶速率;POE-g-MAH的加入降低了基体的结晶速率,并且随着增容剂含量的增加,基体的结晶速率逐渐下降。纯PP的等温结晶过程具有异相成核与均相成核的机理,共混合金的等温结晶过程属于异相成核机理。     

高结晶性PET玻纤增强材料的研究

研究了聚对苯二甲酸乙二醇酯(PET)增强体系中,原料黏度、成核剂以及结晶促进剂对材料结晶性能的影响,并通过力学性能、热性能及DSC分析不同体系中PET的结晶性能。结果表明,特性黏数0.66 dL/g的PET原料结晶最佳,不同种类成核剂中高分子成核剂Aclyn 285是最佳成核剂,添加结晶促进剂PEG400后显著提高PET的晶体生长速度,所获PET材料结晶完善,DSC图中冷结晶峰消失。     

原位聚合法制备PET/纳米氮化钛改性材料及其性能

通过原位聚合法制备纳米氮化钛改性PET材料.利用差式扫描量热仪(DSC)研究纳米氮化钛改性PET材料结晶行为和在不同降温速率下的非等温结晶动力学,用Jeziorny方程对非等温结晶过程进行分析;同时利用热重分析仪(TGA)和万能试验机等研究改性材料的热性能和力学性能.结果表明:纳米氮化钛粒子的加入,起到了异相成核作用,改变了PET的成核机理,提高了PET的结晶度和结晶速率;改善了PET材料的热稳定性和力学性能.     

稀土β成核剂对PPR非等温结晶动力学影响

对添加稀土β成核剂的无规共聚聚丙烯(PPR)非等温结晶动力学进行了研究,采用修正Avrami方程的Jeziorny法和莫志深法对差示扫描量热法(DSC)所得的数据进行处理。结果表明,纯PPR的非等温结晶行为适合Jeziorny法和莫志深法,同时莫志深法可以很好地描述β成核剂改性PPR(βPPR)的非等温结晶行为,但Jeziomy法不能。添加0.05％(质量分数)的β成核剂就可以起到成核作用,提高PPR的结晶度,并使得PPR的结晶温度升高;但是在相同的冷却速率下,纯PPR达到一半结晶度所需的时间(t_(1/2))和结晶峰半峰宽(△W)比βPPR的值要小;同时达到相同的结晶度βPPR所需的冷却速率要大于纯PPR的,这说明β成核剂的加入降低了PPR的结晶速率。     

改性多壁碳纳米管/PET纳米复合材料的非等温结晶行为

采用原位复合方法制备出纯PET、MWNTs-COOH/PET和MWNTs-OH/PET纳米复合材料.通过红外测试发现PET以共价键形式接枝到碳纳米管上;用扫描电镜(SEM)观察了改性碳纳米管在PET基体中的分散性;通过差示扫描量热法(DSC)研究3种纳米复合材料的非等温结晶行为,使用Jeziomy法和莫志深法分析3种样品的非等温结晶动力学.结果表明:COOH/OH官能化MWNTs可以较好地分散在PET基体中并且能够作为一种有效的成核剂,改变PET的成核机理;同时可以使PET在较高的温度下结晶,提高了PET的结晶速率并且MWNTs-COOH/PET复合材料起始结晶时间更早,而MWNTs-OH/PET复合材料结晶速率更快.     

聚甲醛等温结晶动力学研究

采用差示扫描量热法(DSC)研究了纯聚甲醛和加入成核剂氮化硼(BN)的聚甲醛等温结晶动力学,采用Avrami方程和L H方程得到了在不同结晶温度下的K、t1/2、n和σe值,探讨了成核剂BN对聚甲醛的结晶成核作用。实验证明,加入氮化硼后,聚甲醛的结晶峰温度和起始结晶温度提高,结晶过程为异相三维生长过程,结晶速率明显加快,半结晶时间和表面自由能下降,说明BN是一种较好的成核剂。     

三种有机成核剂成核聚丙烯的非等温结晶动力学研究

采用DSC研究了聚丙烯（PP）和三种有机成核剂成核的PP在不同的降温速率下的非等温结晶动力学。用Avrami对DSC的测试结果进行了分析。结果表明,三种有机透明成核剂能显著提高PP的结晶温度和结晶速率。可以用修正Avrami方程的Jeziorny法来处理三种有机成核剂成核PP的非结晶等温结晶行为,处理结果表明：三种有机成核透明成核剂成核PP的半结晶时间减少,结晶动力学常数(Zc)增加,结晶速率增加;松香型成核剂能最快提高PP的结晶速率;同一降温速率下,三种有机成核透明剂成核PP的n值较纯PP减少,结晶成核方式发生了改变。     

PET/nano-MgO复合材料的性能研究

通过熔融共混法制备了聚对苯二甲酸乙二醇酯（PET）/纳米氧化镁（nano-MgO）复合材料,对该复合材料的力学性能进行了测试,并用扫描电子显微镜对nano-MgO在复合材料中的分散情况进行了观测。通过差示扫描量热法研究了复合材料的结晶性能,通过热重分析研究了复合材料的热稳定性,通过紫外可见光谱研究了复合材料的紫外屏蔽性能。结果表明,nano-MgO含量为1 %时复合材料的缺口冲击强度比纯PET高15 %,nano-MgO含量为2 %时复合材料的拉伸强度比纯PET高8 %;nano MgO在复合材料中分散均匀;nano-MgO含量为2 %时复合材料的结晶半峰宽为7.7 ℃,比纯PET低15 %;nano-MgO含量为2 %时复合材料的熔点为252.4 ℃,比纯PET高4.1 ℃;nano MgO含量为3 %时复合材料屏蔽紫外线的截止波长为300 nm,比纯PET高11 %。     

PBT /纳米SiO2非等温结晶动力学研究

熔融制备了PBT/纳米SiO₂复合材料,用DSC分别研究了SiO₂在低含量(0.3%质量分数)和高含量(3%)时的非等温结晶行为;并分析了PBT/纳米SiO₂复合材料的结晶动力学。结果表明,纳米SiO₂对PBT有异相成核作用,加入纳米SiO₂后,显著提高了PBT结晶温度,加快了其结晶速率。结晶动力学表明,莫志深法很好的吻合了PBT/纳米SiO₂复合材料体系,而Ozawa方法并不太适合。通过结晶活化能的计算,表明在低含量(0.3%)时有更好的结晶能力。     

Preparation and properties of poly(ethylene terephthalate)/inorganic whiskers composites

To improve the crystallization and mechanical properties of poly(ethylene terephthalate) (PET), in this work, PET/SiO₂‐MgO‐CaO whiskers composites were prepared via in situ polymerization. The morphology, crystallization, and mechanical properties of the prepared composites were investigated. It was found that inorganic whiskers could be easily dispersed in PET matrix, as demonstrated by SEM and PLM. DSC and PLM observation indicated a strong nucleation capability of inorganic whiskers for PET. Mechanical analysis results showed that the glass transition temperature, tensile strength, and modulus of the composites were greatly improved. A possible chemical bonding between PET chains and the surface of whiskers was observed by FTIR, TGA, and sedimentation experiment. It could be the main reason for the good dispersion and improved properties of the prepared composites. This work is important for the application of PET due to the low cost but high reinforcing efficiency of this inorganic whisker. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

成核剂对PET/PEN共混物性能影响及其机理研究

利用差示扫描量热法、X射线衍射和转矩流变测试等手段,研究了成核剂碳酸氢钠、苯甲酸钠和乙烯-甲基丙烯酸离子键聚合物(Surlyn)对聚对苯二甲酸乙二醇酯/聚萘二甲酸乙二醇酯（PET/PEN）共混物结晶性能和力学性能的影响。结果表明,3种成核剂均能显著提高共混物的成核作用,其中,Surlyn和苯甲酸钠能明显提高共混物结晶性能,结晶峰温度提高约20 ℃,结晶速度提升近1倍;3种成核剂中,只有Surlyn在提高结晶性能的同时,还能提高共混物的力学性能;Surlyn是PET/PEN共混物理想的成核剂。     

β‐Nucleation of pimelic acid supported on metal oxides in isotactic polypropylene

To investigate the nucleation of metal pimelate for isotactic polypropylene (iPP) crystallization, iPP filled with a series of metal oxides with and without metal pimelate on their surface was prepared. There was a chemical reaction between pimelic acid (PA) and metal oxides MgO, CaO, BaO or ZnO, but not TiO₂. The corresponding metal pimelate formed by the chemical reaction between PA and MgO, CaO, BaO or ZnO had a different influence on the crystallization behavior and melting characteristics of iPP. Addition of metal oxides increased the crystallization temperature of iPP and mainly formed α‐phase due to the heterogeneous α‐nucleation of metal oxides. The α‐nucleation of CaO could be easily changed into β‐nucleation using CaO‐supported PA, and 90.1% β‐phase was obtained. The β‐nucleation of BaO could be markedly enhanced by barium pimelate formed using supported PA. However, no β‐phase was observed for iPP filled with MgO‐ or ZnO‐supported PA. The various metal oxides with supported PA had a different influence on the crystallization behavior and melting characteristics of iPP due to the different structure of metal pimelate formed by chemical reaction between PA and the metal oxides. Copyright © 2012 Society of Chemical Industry     

PET/PP共混体系的熔融及非等温结晶行为

用熔融共混法制备了聚对苯二甲酸乙二醇酯(PET)/聚丙烯(PP)复合材料。对复合体系的形态结构、熔融及非等温结晶行为进行了研究。结果表明:两相界面或PP相对PET结晶无明显的异相成核效应;当PP为连续相时,已结晶的极性PET粒子对PP的异相成核作用较为明显;而当PP为分散相时,固态的PET在一定程度上阻碍了PP分子链的运动,促使PP结晶均相成核趋势增加。与纯PET或PP相比,共混体系中两组分结晶的完善程度都有所下降。     

聚对苯二甲酸丙二醇酯的结晶性能研究

采用热台偏光显微镜和DSC差示扫描量热仪对PET、PTT和PBT的结晶性能进行了研究。实验得到的结果是:PBT具有极强的结晶能力。在相同的△T下,PTT的结晶诱导期和球晶出现的时间比PET短,球晶的生长速率也比PET快;同时,在相同的△T下,PTT的总结晶速率大于PET。PET和PTT在较高的温度下等温结晶时倾向于异相成核,而随着等温结晶温度的降低,开始倾向于均相成核。     

ISOTHERMAL CRYSTALLIZATION AND SUBSEQUENT MELTING BEHAVIOR OF POLY(ETHYLENE TEREPHTHALATE)/SILICA NANOCOMPOSITES

The crystallization process of nanocomposites was investigated by differential scanning calorimetry (DSC) and analyzed by the Avrami method. It was found that the crystallization of pure poly(ethylene terephthalate) (PET) is fitted for thermal nucleation and three-dimensional spherical growth in the whole process, while the crystallization of PET/silica nanocomposites exhibits two stages: the first stage corresponds to athermal nucleation and three-dimensional spherical growth, and the second one corresponds to recrystallization caused by the earlier spherulite impingement. The crystallization rate increases markedly and the activation energies decrease greatly with adding silica nanoparticles. The subsequent melting behavior of the crystallized samples shows that the melting point (T_m) of nanocomposites is higher than that of pure PET, which might result from two reasons: (1) some hindrance to the PET chains caused by the nanoparticles at the beginning of the melting process; and (2) more perfect crystals being formed due to the higher crystallization temperature and lower activation energy of PET/silica nanocomposites.     

Crystallization of oriented isotactic polypropylene (iPP) in the presence of in situ poly(ethylene terephthalate) (PET) microfibrils

The present article reports the nonisothermal crystallization process and morphological evolution of oriented iPP melt with and without in situ poly(ethylene terephthalate) (PET) microfibrils. The bars of neat iPP and PET/iPP microfibrillar blend were fabricated by shear controlled orientation injection molding (SCORIM), which exhibit the oriented crystalline structure (shish-kebab), especially in the skin layer. The skin layer was annealed at just above its melting temperature (175 °C) for a relatively short duration (5 min) to preserve a certain level of oriented iPP molecules. It was found that the existence of ordered clusters (i.e. oriented iPP molecular aggregates) leads to the primary nucleation at higher onset crystallization temperature, and formation of the fibril-like crystalline morphology. However, the overall crystallization rate decreases as a result that the relatively high crystallization temperature restrains the secondary nucleation. With the existence of PET microfibrils, the heterogeneous nucleation distinctly occurs in the unoriented iPP melt and results in the increase of crystallization peak temperature and overall crystallization rate, for the first time, we observed that the onset crystallization temperature has been enhanced further with addition of PET microfibrils in the oriented iPP melt, indicating the synergistic effect of row nucleation and heterogeneous nucleation under quiescent condition.