高含量碳纤维对尼龙6非等温结晶与熔融行为的影响

利用差示扫描量热仪（DSC）研究了高含量碳纤维（CF）对尼龙6（PA6）非等温结晶与熔融行为的影响。结晶行为研究结果表明，高含量CF的引入对PA6的结晶起到异相成核作用，提高了PA6的总结晶速率。熔融行为研究结果表明在低的降温速率下。CF诱导基体尼龙6形成亚稳态的γ^＊结晶，其熔融峰为一个明显的不对称单峰；高降温速率下为熔融双峰，低温峰为亚稳态的γ^＊结晶的熔融。而高温峰为亚稳态的结晶在升温过程中发生再结晶和再组合形成更稳定的γ结晶的熔融。     

聚酯型聚氨酯/MC尼龙6原位复合材料非等温结晶和熔融行为研究

本文通过己内酰胺阴离子开环聚合法制备了聚酯型聚氨酯(PES-TPU)/MC尼龙6原位复合材料。利用差示扫描量热法研究了PES-TPU/MC尼龙6原位复合材料的非等温结晶行为和熔融行为。结果表明,在聚酯型聚氨酯/MC尼龙6原位复合材料中,聚酯型聚氨酯对基体MC尼龙6的结晶有一定的抑制作用,降低了其结晶速率和结晶温度;复合材料非等温结晶的熔融行为呈现二重熔融峰,其高温熔融峰温随降温速率的提高变化不大,而低温熔融峰温则随降温速率的提高向低温方向移动且峰强度逐渐增强。     

尼龙6/高岭土复合材料的非等温结晶行为研究

用差示扫描量热法研究了尼龙6/高岭土复合材料的熔融结晶行为,并用Jeziorny法、Ozawa法、Mo法对复合材料的非等温结晶动力学进行研究。结果表明,3种高岭土的加入均使复合体系的熔融峰变窄,熔点增加;结晶峰温和结晶起始温度提高,结晶速率增大;高岭土填料起到异相成核作用;Jeziorny法、Mo法均适合分析尼龙6及复合体系的非等温结晶动力学过程,而Ozawa法不适合。     

MCPA6/纳米TiO2原位复合材料的熔融行为

采用差示扫描量热法(DSC)研究了铸型尼龙6(MCPA6)及其纳米TiO2原位复合材料的等温结晶与非等温结晶晶体的熔融行为。结果表明：MCPA6／纳米TiO2原位复合材料等温结晶晶体的熔融行为呈现三重熔融峰，非等温结晶晶体的熔融行为呈现二重熔融峰；其高温熔融峰温随等温结晶温度或降温速率的变化基本不变，而低温熔融峰温则随等温结晶温度的升高或降温速率的减小而提高；纳米TiO2的加入对MCPA6有一定的成核作用，使其熔点提高。     

聚L-乳酸的热性能研究

为了了解聚L-乳酸(PLLA)自身结构特点,更好地控制其成型加工过程,研究了PLLA的非等温结晶行为、熔融行为和热失重过程。结果表明:降温速率对PLLA的非等温结晶过程具有显著影响,在1℃/min的降温速率下,PLLA的结晶起始温度为121℃,结晶焓为3.363 J/g;PLLA的熔融双峰遵循熔融-再结晶的机理;PLLA热分解温度在300℃左右,且随升温速率的增加而增大。     

PET/分子筛复合材料的非等温结晶性能

采用原位聚合法制备了PET／分子筛复合材料并研究了其非等温结晶性能。结果表明：分子筛的加入有明显的异相成核效应，加快了结晶速度，增加了结晶度，减小了晶粒粒径分布；PET及PET／分子筛体系的热结晶峰温随着降温速率的增加而移向低温，半结晶时间、结晶度随降温速率的增加而减小，晶粒粒径分布则增大；分子筛的加入降低了降温速率对PET半结晶时间的影响；随着分子筛用量的增加，半结晶时间t1／2、结晶热焓ΔH、结晶峰半峰宽ΔW都能达到一个较佳值。     

原位复合阻燃尼龙6的非等温动力学研究

采用差示扫描量热法研究了原位聚合反应制备阻燃尼龙6的非等温结晶行为,用Jeziorny法和莫志深法对其动力学过程进行了分析。结果表明:由于阻燃剂起到异相成核作用,使晶核的生长变快,提高了阻燃尼龙6的结晶温度和成核速率。随降温速率的增加,其结晶峰从高温向低温方向移动,峰形变宽,结晶时间缩短。同时阻燃剂在尼龙6分子链中存在相互作用力,阻碍了尼龙6分子链在结晶过程中的运动,导致结晶活化能提高,晶体生长速度下降,结晶度降低。     

热氧处理条件对聚丙烯粉料DSC曲线形态的影响

发现热氧处理条件对聚丙烯粉料DSC曲线的形态变化有很大影响。随着热氧处理时间的延长,聚丙烯粉料的第一次升温熔融曲线和第二次升温熔融曲线的熔融峰温都会逐渐下降(左移)。第一次升温熔融曲线的熔融峰宽逐渐变窄,峰高逐渐变高;而第二次升温熔融曲线却熔融峰宽逐渐变宽,峰高逐渐变低。在热氧处理时间为0.5~5 h之间时,第一次升温熔融曲线会出现一个很宽的平台状小熔融峰,当热氧处理时间为12 h和14 h时,第二次升温熔融曲线的孪生双峰最明显。随着热氧处理时间的延长,聚丙烯粉料结晶峰温呈现向较低温(向左)方向移动的趋势。     

LLDPE/H-HIPS的非等温结晶动力学研究

采用差示扫描量热法研究了不同降温速率下线性低密度聚乙烯(LLDPE)和LLDPE/H-HIPS(氢化高抗冲聚苯乙烯)共混物的非等温结晶行为,并用Jeziorny法进行处理分析。结果表明:降温速率的增大会使得以上两种样品的结晶峰均向温度较低的方向移动,LLDPE/H-HIPS共混物的结晶峰向低温方向移动的同时结晶峰逐渐变宽,结晶焓减小;在相同降温速率下,LLDPE/H-HIPS共混物的峰值结晶温度较纯LLDPE有所降低;LLDPE/H-HIPS的Avrami指数n的起始值增大且范围变窄;由Kissinger法估算的LLDPE和LLDPE/H-HIPS的结晶活化能分别为309.45,326.63kJ/mol。     

HDPE/空心玻璃微珠复合材料非等温结晶研究

采用熔融共混挤出的方法,制备了高密度聚乙烯/空心玻璃微珠(HDPE/HGB)复合材料,用差示扫描量热法研究了HDPE和HDPE/HGB的非等温结晶过程,通过Jeziorny法研究了非等温结晶动力学.结果表明,随降温速率的增大,HDPE和HDPE/HGB试样的结晶峰温和结晶度降低,结晶速率增大;HGB的加入使结晶度增大,但对HDPE的结晶速率影响较小.     

Crystallization, hydrolytic degradation, and mechanical properties of poly (trimethylene terephthalate)/poly(lactic acid) blends

Crystallization, melting, hydrolytic degradation, and mechanical properties of poly(trimentylene terephthalate)/poly(lactic acid) (PTT/PLA) blends have been investigated. The blends show a single and composition-dependent glass-transition temperature (T _g) over the entire composition range, implying that these blends are fully miscible in the amorphous state. The observed T _g is found to increase with increasing PLA content and fitted well with the Gordon–Taylor equation, with the fitting parameter k being 0.91. The cold-crystallization peak temperature increases, while the melt-crystallization peak decreases with increasing the PLA content. Both the pure PTT and PTT/PLA blends cannot accomplish the crystallization during the cooling procedure and the recrystallization occurs again on the second heating. Therefore, on the thermogram recorded, there is exothermal peak followed by endothermal peak with a shoulder. However, to pure PLA, no crystallization takes place during cooling from the melt, therefore, no melting endothermic peak is found on the second heating curve. WAXD analysis indicates PLA and PTT components do not co-crystallize and the crystalline phase of the blends is that of their enriched pure component. With increasing PLA content, the hydrolytic degradation of the blend films increases, while both the tensile strength and the elongation at break of the blend films decrease. That is to say, the hydrolytic degradation of the PTT/PLA blends increases with the introduction of PLA at the cost of the decrease of the flexibility of PTT.     

Structure and crystallization behavior of Nylon 66/multi-walled carbon nanotube nanocomposites at low carbon nanotube contents

Multi-walled carbon nanotubes (MWNTs) were modified with poly(hexamethylene adipamide) (also known as Nylon 66) via a controlled polymer solution crystallization method. A “nanohybrid shish kebab” (NHSK) structure was found wherein the MWNT resembled the shish while Nylon 66 lamellar crystals formed the kebabs. These Nylon 66-functionalized MWNTs were used as precursors to prepare polymer/MWNT nanocomposites. Excellent dispersion was revealed by optical and electron microscopies. Nitric acid etching of the nanocomposites showed that MWNT formed a robust network in Nylon 66. Non-isothermal DSC results showed multiple melting peaks, which can be attributed to lamellar thickness changes upon heating. The crystallite sizes L₁₀₀ and L₀₁₀ of Nylon 66, determined by WAXD, decreased with increasing MWNT contents. Isothermal DSC results showed that crystallization kinetics increased first and then decreased with increasing MWNT contents in Nylon 66. This study showed that the effect of MWNTs on Nylon 66 crystallization is twofold: MWNTs provide heterogeneous nucleation sites for Nylon 66 crystallization while the tube network structure hinders large crystal growth.     

反式-1,4-聚异戊二烯的结晶性

采用差示扫描量热仪、傅里叶变换红外光谱、偏光显微镜和X射线衍射仪等研究了反式-1,4-聚异戊二烯(TPI)的结晶性。结果表明,在TPI的差示扫描量热分析中,随着升温速率提高,第1次升温曲线上的β晶型熔融温度移向高温;而第2次升温曲线上的α晶型结晶熔融峰逐渐消失,且与第1次升温时相比β晶型的熔融温度偏高;而随着降温速率的提高,TPI的结晶峰向低温方向位移。用不同方法制备的TPI薄膜可以得到球晶、碎晶和捆束状晶体。与浇铸薄膜相比,热压薄膜傅里叶变换红外光谱曲线上的843 cm-1和980 cm-1两侧各出现了2个肩峰,而890 cm-1处的结晶峰消失。拉伸后在TPI的X射线衍射谱线上,0.47 nm和0.39 nm晶面间距的所属峰形比拉伸前要尖锐得多,而0.33 nm晶面间距所属峰则弱化。     

含杂质二氧化碳实际气体干气密封性能研究

基于EOS-CG模型和GERG-2008模型计算含杂质二氧化碳混合气体的密度,基于CO₂-Pedersen模型计算混合气体的黏度。利用模型计算数据拟合获得含杂质二氧化碳混合气体密度、黏度与压力的关系式,用以描述混合气体的实际行为以及黏度随压力变化的规律。采用有限差分法求解稳态雷诺方程,得到了纯二氧化碳和含杂质二氧化碳干气密封开启力、泄漏率以及气膜刚度,并分析了杂质对二氧化碳干气密封性能(开启力、泄漏率、气膜刚度)的影响。考虑的变量有端面平均线速度、气膜厚度、进口温度以及进口压力等。结果表明：当进口压力为15.26 MPa,进口温度为363.15 K,线速度为74.030 m/s,气膜厚度为3.05 μm时,含杂质二氧化碳干气密封开启力和泄漏率都小于纯二氧化碳干气密封开启力和泄漏率,且杂质含量越多,差别越明显;杂质对二氧化碳干气密封开启力、泄漏率、气膜刚度的影响随端面平均线速度的增大而增大;对泄漏率、气膜刚度的影响随气膜厚度的增加而减小;对开启力、泄漏率、气膜刚度的影响随进口温度的增大而减小;对开启力的影响随进口压力的增大先减小,再增大,最后减小,对泄漏率的影响随进口压力的增大先增大后减小,对气膜刚度的影响随进口压力的增大先减小后增大。     

Turbidity investigation of the sol–gel transition in carrageenan gels under physiologic conditions

A spectrophotometer was used to measure the turbidity of a carrageenan gel as a function of temperature. The optical transmission of the gels was found to decrease as the gels undergo the sol–gel phase transition. The differential of transmission (I) with respect to temperature (T), dI/dT, exhibits peaks for both the cooling and the heating runs with the peak positions corresponding to temperatures of gelation and melting, respectively. The full-width at half-height of the dI/dT peak obtained from the heating curve is about 2.5 times broader than that from the cooling curve. This indicates that the melting of gels may involve multiple relaxation mechanisms. The area of the hysteresis loop covered by the cooling and the heating curves increases with a decrease in the scanning rate. The thermal cycling has little impact on the sol–gel transition in the gels. The experiments show that turbidity is a powerful tool for studying the sol–gel transition in carrageenan gels. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:29–35, 1998     

Preparation and properties of environmental friendly nonhalogen flame retardant melamine cyanurate/nylon 66 composites

Melamine cyanurate (MCA) was utilized as an environmental friendly additive to prepare the nonhalogen flame retardant MCA/Nylon 66 composites by melt blending technique. Because of the strong hydrogen bond interactions and fine interfacial compatibility between MCA and Nylon 66, the resultant even dispersion of MCA filler in polymer matrix leads to the better toughness and strength of MCA/Nylon 66 composites than those of neat Nylon 66. Both Nylon 66 and MCA/Nylon 66 composites exhibit similar α‐crystalline structure, but the presence of MCA influences the distribution of α1 and α2 crystalline phases in Nylon 66 by inducing its hydrogen‐bonded sheet separation. Moreover, the blending of MCA and Nylon 66 increases the crystallization temperature and exothermicity but decreases the thermal stability of Nylon 66 and accelerates the degradation of MCA. The MCA/Nylon 66 composites show better flame retardancy at intermediate MCA contents of 10 and 15 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PA6/PET共混体系的动态力学性能

应用粘弹谱仪研究了ＰＡ６／ＰＥＴ共混体系的动态力学性能,结果表明：ＰＡ６和ＰＥＴ的β损耗峰温相近,其共混物只观察到一个损耗峰,但峰宽随ＰＥＴ组分增加而增宽;相应于束缚非晶区分子链段运动的α损耗峰（αⅠ）只有一个,其峰温依加和律线性变化,说明在束缚非晶区内相溶：相应于自由非晶区分子链段运动的α损耗峰有两个（αⅡ和αⅢ）,随ＰＥＴ组分增加,αⅡ损耗峰温升高而αⅢ的降低,因此ＰＡ６和ＰＥＴ在自由非晶区是部分相溶的     

Melting behavior of polypropylene fibers studied by differential scanning calorimetry

Polypropylene fibers produced in a compact-spinning process were studied by differential scanning calorimetry (DSC). With unrestrained fibers, the onset of melting increases with decreasing draw ratio, increasing M_w/M_n, decreasing extrusion temperature, increasing annealing ratio, and increasing draw-down ratio. These trends are discussed in terms of restraints and reorganization. The onset of melting is shifted to lower temperatures as the heating rate increases for all combinations of material and processing parameters, indicating suppressed reorganization. At low draw ratios, the height and width of the endotherm are affected by the spinline stress, and a secondary peak or shoulder is observed on the high temperature side of the main peak. The magnitude of the secondary peak increases with decreasing M_w/M_n, increasing draw ratio, decreasing draw-down ratio, and decreasing heating rate, but its position mainly depends on the heating rate. This indicates that the secondary peak may be due to the melting of structures that have been reorganized during the heating scan. As the draw ratio increases, the melting regime broadens, especially towards lower temperatures, and several maxima emerge on the DSC curve. Reorganization and shrinkage during heating may explain these observations. © 1995 John Wiley & Sons, Inc.     

背压对聚丙烯塑化过程的影响

用有限元法研究了背压对聚丙烯塑化过程的影响。研究结果表明,随着背压的增加,螺杆流道内压差增加,计量段熔体的流速减小,剪切应力、剪切速率和粘性热增加,粘度变化不明显;计量段内沿螺杆轴向熔体的最大压差、最大剪切应力、最大剪切速率和最大粘性热增加,流速和粘度均匀,止逆环后各物理量出现峰值。