表面接枝处理的n-HA充填PLGA等温结晶行为的研究

应用示差扫描量热计（DSC）研究了用低分子量聚乳酸（PDLLA）接枝与未接枝两种处理的纳米羟基磷灰石（n-HA）对聚乙丙交酯（PLGA）等温结晶行为及熔融行为的影响,采用Avrami方程处理其等温结晶过程,计算结晶动力学参数;同时用配带热台的偏光显微镜（POM）研究了其结晶的晶核形态。结果表明该体系等温结晶行为可以用Avrami方程来描述;加入n-HA的两种复合材料及PLGA其结晶最快的温度都是110℃,且都是随着结晶温度的提高结晶速率变慢,但接枝的n-HA对提高PLGA基体的结晶速率、熔点及结晶活化能都比未接枝处理的要小。偏光显微镜研究得出加入n-HA的两种复合材料及PL-GA其球径形态相似,且都随温度升高而使结晶速度降低,但加入未接枝的n-HA比接枝后的结晶更快。以上结果说明接枝处理后的n-HA提高了两相界面结合,因而n-HA的异相成核能力比未接枝处理的要差。     

木粉聚丙烯复合材料的等温结晶动力学

应用差示扫描量热法(DSC)研究了有无相容剂(m-TMI-PP)的木粉聚丙烯复合体系的等温结晶行为,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增大。在同一结晶温度下,木粉起到成核剂的作用,提高了基体的结晶速率;m-TMI-PP的加入,使基体的结晶速率下降。纯PP的等温结晶过程具有异相成核与均相成核的机理,复合材料的等温结晶过程属于异相成核机理。     

聚羟基丁酸酯的等温与非等温结晶动力学

用差示扫描量热法(DSC)研究了聚羟基丁酸酯(PHB)的等温与非等温结晶动力学。采用Avrami方程分析了等温结晶动力学,Avrami指数n≈2,表明PHB以异相成核的二维平面晶体方式生长,等温结晶活化能为82.4 kJ/min。采用Jeziorny法和莫志深法分析了PHB的非等温结晶动力学,Avrami指数n≈3,表明PHB非等温结晶过程以异相成核的三维球晶方式生长。     

癸二酰二苯甲酰肼对聚L-乳酸/玻璃纤维复合材料结晶性能及力学性能的影响

利用差示扫描量热仪(DSC)研究了癸二酰二苯甲酰肼(BSAD)成核剂对聚L-乳酸(PLLA)/玻璃纤维(GF)复合材料等温及非等温结晶性能的影响。结合偏光显微镜(POM)观察发现,BSAD可在熔融加工中与PLLA基体形成均相,在冷却过程中,该体系发生相分离,BSAD晶体优先从PLLA熔体中析出,诱导PLLA结晶。等温结晶动力学研究发现,随着BSAD含量提高,PLLA的Avrami指数逐渐减小,表明异相成核增强。在110℃形成的成核剂晶体尺寸较小,可在提高PLLA结晶速率的同时细化晶体尺寸,并改善PLLA/GF复合材料的拉伸、弯曲及冲击性能。     

LLDPE/SEBS-g-MAH的非等温结晶动力学

利用差示扫描量热法结合Avrami方程研究了线性低密度聚乙烯(LLDPE)、LLDPE/SEBS及不同接枝率的LLDPE/SEBS-g-MAH的非等温结晶动力学。通过Gupta法、Jeziorny法和莫志深法分别对非等温结晶过程进行处理,结果显示,热塑性弹性体SEBS及其接枝物的加入阻碍了LLDPE分子链的规则排列,影响了链段在结晶扩散迁移规整排列的速度,使得结晶速率变慢,对LLDPE晶体生长起了抑制作用。但在所有结晶速率下,样品的Avrami指数n值均在1.1～1.5之间,说明LLDPE的结晶成核机理和生长方式没有改变。     

脂肪族聚酯结晶特性与分子结构的关系

用差示扫描量热法(DSC)和修正的Avrami方程研究了聚丁二酸乙二醇酯(PES)、聚丁二酸丁二醇酯(PBS)、聚丁二酸己二醇酯(PHS)、聚己二酸己二醇酯(PHA)和聚癸二酸己二醇酯(PHSe)的非等温结晶动力学,得到了脂肪族聚酯的Avrami指数、结晶速率常数、结晶活化能和过冷度等结晶动力学参数.结果表明,脂肪族聚...     

乙烯含量对抗冲共聚PP非等温结晶行为的影响

利用DSC研究了不同结晶速率下四种具有不同乙烯含量的抗冲共聚聚丙烯的非等温结晶动力学,采用Avrami方程和Avrami-Ozawa方程的结合（莫氏法）分析了非等温结晶动力学,结果表明,四种样品的Avrami指数在5～6范围内,说明具有不同乙烯含量的四种样品中的PP的结晶方式并不随冷却速率的变化而变化.F（T）的值随结晶度的增加而增加,a的值也有相似的变化,但变化不大,表明冷却速率越快,在单位时间内的结晶度越大,结晶方式并无多大变化。     

CB含量对微纤化导电复合材料CB/PET/PE非等温结晶的影响

采用差示扫描量热仪(DSC)研究了不同CB含量的原位微纤化复合材料CB/PET/PE在不同的冷却速率(2.5℃/min,5℃/min,10℃/min,20℃/min)的非等温结晶行为,采用扫描电子显微镜(SEM)观察微纤形态。结果表明,随CB含量增加,复合材料结晶起始温度降低,且相对结晶速率减小。SEM观察发现,CB的加入改变了微纤形态,随CB含量增加,CB粒子逐渐占据了微纤表面且纤维形态变差。     

聚对苯二甲酰癸二胺(PA10T)的结晶动力学

用差示扫描量热仪详细研究了聚对苯二甲酰癸二胺(PA10T)的等温与非等温结晶动力学。用Avrami方程描述了PA10T等温结晶动力学,发现PA10T在选定的结晶条件下晶体的生长模式是二维生长,成核方式为均相成核,并求出Avrami指数为2,结晶活化能为302.32 kJ/mol;研究PA10T非等温结晶动力学后,发现随着降温速率的增大,结晶峰值温度向低温移动,结晶度和结晶焓增加,结晶速率显著加快。用Mo方程描述了其非等温结晶动力学,F(T)值随着相对结晶度的增加而增加,α值基本保持在1.6,非等温结晶活化能为338.56 kJ/mol。     

PET/苯乙烯-丙烯酸钠离聚物的结晶及熔融行为

采用差示扫描量热仪(DSC)研究了离聚物苯乙烯-丙烯酸钠对聚对苯二甲酸乙二酯(PET)的结晶行为及熔融行为的影响。结果表明,苯乙烯-丙烯酸钠离聚物能够诱导PET异相成核,从而大幅度提高PET的熔融结晶温度和降低冷结晶温度,实现PET在高温区和低温区结晶速率的同时提高,并使PET在等温熔融结晶过程的Avrami指数n增加。同时,苯乙烯-丙烯酸钠的加入改变了PET的熔融行为,同等结晶温度下PET/苯乙烯-丙烯酸钠离聚物的多重熔融峰中的峰II温度值大于纯PET。     

不同分子量尼龙1010的恒温结晶动力学

用示差扫描量热法研究了３种不同分子量的尼龙１０１０样品的等温结晶行为,在所研究的温度范围内,尼龙１０１０的等温结晶过程符合Ａｖｒａｍｉ方程。Ａｖｒａｍｉ指数约为２,基本上与分量及结晶温度无关。随着分子量的增大,尼龙１０１０结晶速率变慢,其片晶的侧面自由能增大。     

尼龙612的等温结晶动力学

用差示扫描量热(DSC)研究了尼龙612的等温结晶动力学.实验结果表明,在所研究的等温结晶温度范围内(184℃、186℃、188℃、190℃、192℃),尼龙612达到最大结晶速率时的时间、半结晶期和动力学结晶速率常数分别为:O.12min、0.19 min、0.22 min、0.29 min、0.59 min;0.1...     

Crystallization behavior of organo-nanoclay treated and untreated kraft fiber–HDPE composites

Both non-isothermal and isothermal crystallization behaviors of neat HDPE and organo-nanoclay treated and untreated kraft fiber–high density polyethylene (HDPE) or HDPE–maleic anhydride polyethylene (MAPE) composites were analyzed using differential scanning calorimetry (DSC). The isothermal crystallization process was studied by the Avrami model. The crystallization patterns and organo-nanoclay distribution was characterized by X-ray diffraction (XRD). It was found that both organo-nanoclay treated and untreated kraft fibers could act as nucleating agent for the HDPE polymer when the fiber length was comparatively small. All composites crystallized much faster than the neat HDPE, while their crystallinity levels were lower. The organo-nanoclay treatment of kraft fibers made the crystallinity level lower, but the nucleation rate increased in the composites compared to the untreated kraft fiber–HDPE composites. But both the crystallinity level and the nucleation rate of the composites were increased by adding MAPE compatibilizer to the composites. MAPE increased the d-spacing of the organo-nanoclay layers in the composites and resulted in exfoliated clay platelets when the fiber loading was as high as 40 wt%.     

原位聚合尼龙11/石墨烯氧化物纳米复合材料的等温结晶和熔融行为

采用原位聚合法制备了尼龙11/石墨烯氧化物纳米复合材料,并利用差示扫描量热分析仪(DSC)研究了材料的等温结晶动力学和熔融行为。研究结果表明,Avrami方程能够较好地描述尼龙11及其纳米复合材料的等温结晶动力学;尼龙11结晶速率受晶体生长速率控制,而纳米复合材料的结晶速率在不同的结晶温度范围内分别受晶体生长速率或成核速率控制;与纯尼龙11相比较,复合材料具有较低的平衡熔点和表面折叠自由能。     

增韧尼龙6的结晶,热行为和加工性能

对聚烯烃弹性体接枝物(E-g-MA)和尼龙6的共混物的结晶、热行为和加工性能等方面进行了研究。 对不同比例的Ny6/E、Ny6/E-g-MA二元共混物进行了熔融指数的测定,Ny6/E的MI的变化随弹性体含量增加而下降,而相同比例的Ny6/E-g-MA的MI值明显低于前者。 对纯Ny6和相同比例的Ny6/E、Ny6/E-g-MA共混物进行了等温结晶速度的测定。 共混物的DSC、WAXD测定结果表明:E-g-MA的加入不会影响Ny6的热行为、晶胞参数和γ晶型的形成,也不会产生新的晶型。增韧尼龙6比纯尼龙6更有利于加工成型。     

Isothermal crystallization kinetics of glass fiber and mineral-filled polyamide 6 composites

In this study, isothermal crystallization kinetics of polyamide 6 (PA6) composites reinforced with surface-treated glass fiber (GF) and natural, clay-type mineral (MN) were investigated by differential scanning calorimetry method in the presence and absence of a nucleating agent (NA). Microstructural features of the composites and interfacial interactions between filler and polyamide phases were also quantified by rheological measurements. The kinetic parameters for the isothermal melt-crystallization process of the samples were determined with the Avrami and Lauritzen–Hoffman models. The crystallization activation energies were determined by the Arrhenius method. It was found that the both fillers yielded a significant increase in the storage modulus of PA6. Kinetic calculations showed that the MN has a more pronounced acceleration effect on the crystallization rate of PA6 than the GF. Introduction of a small amount of NA significantly favored the isothermal crystallization rate of GF-reinforced PA6 but did not accelerate that of MN-reinforced one. Based on the results, it has been highlighted that PA6 composites reinforced with surface-treated GFs and including a small amount of clay-like mineral as a cheap and easy-accessible minor filler could yield the best performance for the injection-molded PA6 parts because the GF enhances the mechanical properties and the clay-like mineral accelerates the crystallization rate.     

Morphology, crystallization and melting behaviors of isotactic polypropylene/high density polyethylene blend: effect of the addition of short carbon fiber

The effect of vapor grown carbon fiber (VGCF) on the morphology, crystallization and melting behaviors of isotactic polypropylene (iPP)/high density polyethylene (HDPE) blend have been studied by means of Scanning Electron Microscopy (SEM) and Differential Scanning Calorimeter (DSC). It is found that the addition of VGCF results in a dramatic change in the morphology of iPP/HDPE blends. The crystallization peak temperature and melting point of iPP are not altered significantly by the blending. However, the degrees of crystallinity of iPP in the blends are reduced. Compared with the unfilled blends, the crystallization peak temperatures of iPP increase dramatically for the composites. The isothermal crystallization behavior of iPP is further investigated. The analysis of the crystallization half time shows that the crystallization rate of iPP is reduced by the presence of HDPE melt, and is enhanced by carbon fibers. For the unfilled blends in which iPP is the major component, the Avrami exponent closes to 3, independent of the HDPE content. However, for the composites, the Avrami exponent varies with the composition in a rather complex manner. An explanation based on heterogeneous and homogeneous nucleation is supposed. The sharp changes in the crystallization and melting behaviors for the composites containing 30–35wt% HDPE correspond to the sudden change in the morphology of the two phases. It is supported by the observation of SEM and the electrical measurement.     

纳米羟基磷灰石/聚乙丙交酯复合材料等温结晶动力学

采用溶液共混法将不同含量纳米羟基磷灰石(n-HA)充填于聚乙丙交酯(PLGA)制得n-HA/PLGA纳米复合材料,用差示扫描量热法(DSC)研究了该复合材料的等温结晶行为并采用Avrami方程处理等温结晶过程,计算结晶动力学参数.结果表明,该n-HA伊LGA复合材料体系结晶速度快慢的温度大部分符合110℃＞100℃＞1...     

PA6/PA66/PA11共聚物的等温结晶行为

用DSC研究了熔融缩聚法制备的PA6/PA66/PA11共聚物的等温结晶行为。用Avrami方程分析了PA6/PA66/PA11的等温结晶动力学,其Avrami指数n值介于2.34~2.88之间,表明PA6/PA66/PA11是以二维盘状生长和三维球晶生长并存的球状晶体,然后计算了相关的结晶动力学参数。最后用Hoffman-Weeks理论计算出了共聚物的平衡熔点。偏光显微镜分析表明11-氨基十一酸的加入,使得共聚尼龙的球晶粒径进一步细化,数目增多。