聚乳酸的溶液结晶行为

采用DSC和XRD方法研究从不同浓度对二甲苯溶液中结晶的聚乳酸的结晶行为。结果表明,从稀溶液中得到的聚乳酸具有高的结晶度,高的非等温结晶温度和快的结晶速度。     

聚合物球晶生长过程模拟

结晶性聚合物在熔融态冷却过程中,往往伴随着球晶的生成,球晶的密度和尺寸分布直接影响到制品的热力学、光学及力学性能。文中研究了聚合物冷却过程中球晶的形态学演变;模拟了球晶在生长过程中的形态演化过程;考察了成核诱导时间、成核密度、生长速率和碰撞对球晶形态变化的影响;比较了等温和非等温条件下聚合物的结晶过程。研究结果表明,在等温结晶过程中随着温度的降低,晶粒越来越细化,结晶程度越来越大,球晶碰撞边界为直线;非等温结晶过程中由于温度一直在降低,不断出现新的球晶,晶体大小不一,碰撞后边界为曲线。     

细菌纤维素/聚乳酸互穿网络复合材料的结晶与熔融

为了研究细菌纤维素(BC)网络结构对聚乳酸(PLA)结晶与熔融过程的影响,以PLA为基体,BC为增强体,通过PLA-三氯甲烷溶液与BC-无水乙醇分散液的共混扩散制备了具有互穿网络结构的BC/PLA生物复合材料。采用SEM、偏光显微镜(POM)、DSC和莫志深(MO)模型研究了复合材料的微观形态、球晶形貌、非等温结晶动力学和熔融行为。结果表明:采用溶液共混扩散法可得到以BC为骨架、PLA缠绕其表面的互穿网络结构的复合材料。随降温速率增加,BC/PLA复合材料的结晶温度、熔融温度和相对结晶度均下降。BC可作为异相成核剂,适量添加可同时提高BC/PLA复合材料的结晶速率和相对结晶度,细化球晶尺寸。MO模型可较好地描述BC/PLA复合材料的非等温结晶动力学行为。     

Non-isothermal Crystallization Kinetics of Polyamide 6/Diamine-modified MWNTs Nanocomposite

The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube (PA6/D-MWNT) nanocomposite was investigated by differential scanning calorimetry (DSC). The modified Avrami equation, the Ozawa equation and the combined Avrami/Ozawa equation were employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. It was found that the combined Avrami/Ozawa equation could successfully describe the non-isothermal crystallization process. The results showed that D-MWNTs not only acted as effective heterogeneous nucleating agents for PA6 and noticeably increased the crystallization temperature of PA6, but also influenced the mechanism of nucleation and crystal growth of PA6 and then reduced the overall crystallization rate of the neat PA6 matrix. The crystallization activation energy for the nanocomposite sample was greater than that of the neat PA6, which indicated that the addition of D-MWNTs hindered the mobility of PA6 chain segments.     

PTFE/SGM复合材料非等温结晶动力学

通过冷压烧结工艺制备了聚四氟乙烯/实心玻璃微珠(PTFE/SGM)复合材料。采用差示扫描量热法(DSC)研究了PTFE/SGM复合材料的非等温结晶行为,并利用Jeziorny模型对所得DSC数据进行处理。结果表明:Jeziorny模型处理PTFE/SGM复合材料的非等温结晶动力学过程是合理可行的;随着冷却速率的增加,结晶峰向低温方向移动,结晶温度范围增大,结晶度下降;SGM有一定的成核作用,提高了PTFE的结晶峰温和结晶速率,降低了结晶活化能,使PTFE更易结晶。     

成核剂对PET结晶行为的影响

采用差示扫描量热仪(DSC)研究了PET及添加成核剂后PET的非等温结晶过程,选用7种成核剂和4种复合成核剂进行了实验对比研究.结果表明添加任何一种成核剂后PET体系的结晶峰温移向高温,半结晶时间缩短,结晶速率常数增大,结晶度提高.其中有机类成核剂对PET结晶改善效果较无机类显著,但结晶效果最好的是成核机理为化学成核的高分子类成核剂和复合成核剂.本文还采用了热台偏光显微镜(POM)对PET晶体形貌进行了研究,发现添加有机成核剂后晶体细微而且密集.     

Gelation behaviour of UHMWPE/camphene

The sol–gel transition behaviour of ultra-high molecular weight polyethylene (UHMWPE) in decalin, paraffin oil and camphene has been investigated. UHMWPE solutions exhibit a thermo-reversible gelation, recognized in gels, which is due to crystallization. Viscosity results indicated that polymer molecules disentangled more easily when camphene was used as a solvent. This characteristic implies that camphene is a more desirable solvent for solution processing of UHMWPE. A higher recrystallization temperature, Tc, also occurred at a higher gelation temperature, Tgel. The gel melting temperature, Tm,gel, was also measured and its dependency on polymer concentration was investigated using the Eldridge–Ferry equation. The reciprocal of the absolute gel melting temperature was found to have a linear relationship with the logarithm of polymer concentration     

木粉/低熔点尼龙6复合材料的非等温结晶动力学

利用LiCl改性尼龙6 (PA6),并将其与木粉熔融共混制备了木粉/低熔点PA6复合材料,通过DSC法研究了木粉/低熔点PA6复合材料的非等温结晶动力学行为。结果表明,LiCl降低了PA6的熔点、结晶温度、结晶度和结晶速率,提高了PA6的结晶活化能。木粉是良好的成核剂,能够加快PA6的结晶速率,但却降低了其结晶度。通过Mo法分析木粉/低熔点PA6复合材料的非等温结晶动力学,结果表明,与纯PA6和木粉/PA6复合材料相比,低熔点PA6的F(T)值(表征聚合物结晶快慢参数)最大,LiCl提高了PA6在单位结晶时间内达到一定结晶度时所需的冷却速率,而木粉则与之相反。      

PET/PE原位微纤化共混物的非等温结晶

通过挤出、热拉伸及淬冷制备了聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)原位微纤化共混物。采用差示扫描量热仪(DSC)研究了PET/PE原位微纤化共混物的非等这结晶特性,为了比较,同时考察了纯PE和PET/PE通常共混物的结晶特性。结果表明,PET微纤对PE有良好结晶异相成核作用,可提高结晶温度、缩短结晶时间、增大结晶速率,但使PE的结晶度和熔点降低;增加降温速率,结晶峰变宽且向低温方向移动。     

用差示扫描量热法研究Mg65Cu25Gd10块体非晶合金的晶化动力学

通过铜模吸铸法得到Mg65Cu25Gd10块体非晶舍金，用差示扫描量热仪（DSC）研究其晶化动力学和玻璃转变行为，玻璃转变温度Tg，晶化起始温度Tx，晶化峰值温度Tp都与加热速率有关，通过Kissinger方程可以得到表面激活能，发现晶化初始激活能Ex小于峰值激活能Ep，表明形核过程比生长过程容易，讨论了此非晶舍金的玻璃形成能力，根据JMA方程非等温模型研究了晶化动力学，Avrami参数表明在不同温度下的晶化机制是不同的．     

液/液膜吸收过程中伴生渗透蒸馏的抑制

着重探讨了抑制液／液膜吸收过程中伴生渗透蒸馏的方法及其影响因素、实验结果表明，采用加热浓溶液、冷却稀溶液的方法，可以有效抑制住液／液膜吸收过程中伴生的渗透蒸馏作用．实验发现，实际所需的浓溶液和稀溶液间的最小抑制温差要高于理论值1．2～2．8倍．膜材料性能、温差极化以及温度对渗透通量的影响是造成这种偏差的主要原因．     

等规聚丙烯/豆油溶液体系的结晶过程研究

采用DSC法对等规聚丙烯(iPP)／豆油溶液的非等温结晶过程进行了研究．研究了聚丙烯浓度和降温速率对结晶温度的影响,结晶温度随降温速率升高而下降,随iPP含量增加略有上升,用自制热台在自然降温条件下对聚丙烯／豆油溶液的浊点进行了测定,结合DSC法的测定结果,绘制了聚丙烯／豆油体系的非平衡相图．另外研究了成核剂对结晶温度的影响,研究发现加入成核剂后iPP／豆油体系的结晶温度提高了15℃以上．     

Crystallization of partially miscible linear low-density polyethylene/poly(ethylene-co-vinylacetate) blends

Miscibility and crystallization of linear low-density polyethylene (LLDPE)/poly(ethylene-co-vinylacetate) (EVA) blends were investigated by optical microscopy (OM) and differential scanning calorimetry (DSC). It was found that there existed liquid–liquid phase separation (LLPS) below 220 °C over the whole composition. However, the depression in the crystallization temperature, melting temperature and equilibrium melting temperature of LLDPE all indicated that this polymer pair was partially miscible. The crystallization and melting behavior of LLDPE were determined by the dilute effect of non-crystalline EVA and the probable co-crystallization of parts of EVA chains with LLDPE chains. The crystallization and melting behavior of EVA was determined by the competence between a nucleation effect of LLDPE crystals and partial miscibility between this polymer pair, which was different from that of LLDPE.     

Influence of textile preforming binder on the thermal and rheological properties of the catalyzed cyclic butylene terephthalate oligomers

The influence of an epoxy resin textile preforming binder on the thermal and rheological properties of the catalyzed Cyclic Butylene Terephthalate (CBT) oligomers was studied for the manufacturing of textile reinforced pCBT composites with bindered textile preforms. Thermal and rheological investigations were conducted with Differential Scanning Calorimetry (DSC) and plate-plate rheometry, respectively. Significant influences on both non-isothermal und isothermal crystallization of in situ polymerized Cyclic Butylene Terephthalate (pCBT) were observed due to the presence of preforming binder. The crystallization temperature and the crystallinity of pCBT polymer during cooling are both found to decrease with increasing filling fraction of preforming binder. The isothermal polymerization and crystallization process was confirmed to be influenced in the aspect of the starting time of crystallization, the crystallization rate and the crystal structures due to the addition of preforming binder. Furthermore, the processing time was found to be prolonged by adding the preforming binder.     

FENE珠-簧链聚合物分子模型流变性质Brown动力学模拟

通过布朗(Brown)动力学方法模拟了有限伸展非线性弹性(FENE)珠-簧链分子模型在稳态简单剪切流场和突始剪切流场中的运动,得到分子链的位形变化轨迹,同时对聚合物分子力场进行计算分析,模拟流变性质,研究温度、弹簧参数和剪切速率等对该模型定常与非定常流变性质的影响。结果表明,随温度升高,聚合物黏度下降,随剪切速率的升高伴随有假塑性剪切变稀现象发生,并且弹簧拉伸常数不同,聚合物黏度稳态值也不同。     

聚合物/蒙脱土纳米复合材料的制备与结晶性能

本文综述了制备聚合物 /蒙脱土纳米复合材料的插层方法 ,并对有代表性的结晶性聚合物 /蒙脱土纳米复合材料的结晶性能进行了讨论。蒙脱土的加入对聚合物的结晶有两种作用 ,一方面是对聚合物有异相成核的作用 ,可以提高聚合物的结晶温度和结晶速率 ,降低结晶活化能 ;另一方面是对聚合物结晶生长有阻碍作用 ,导致结晶速率下降 ,结晶活化能提高     

SiO_2-MWNTs/聚乳酸复合材料的冷结晶动力学及球晶形态

为研究多壁碳纳米管(MWNTs)对聚乳酸(PLA)冷结晶动力学和球晶形态的影响,分别以PLA和表面包覆纳米SiO2并接枝硅烷偶联剂的纳米SiO2改性MWNTs(SiO2-MWNTs)为基体和改性剂,经溶液共混法制备了SiO2-MWNTs/PLA复合材料。采用DSC、偏光显微镜、Jeziorny模型和Johnson-Mehl-Avrami模型研究了复合材料的非等温冷结晶动力学和球晶形态。结果表明:SiO2-MWNTs可作为异相成核剂,能有效降低SiO2-MWNTs/PLA复合材料的冷结晶温度,提高晶核生成速率和晶体生长活化能。SiO2-MWNTs/PLA复合材料的冷结晶过程主要由成核作用控制,加入SiO2-MWNTs可同时提高复合材料的结晶速率和结晶度。冷结晶时,PLA球晶尺寸小于熔体冷却结晶时的,且SiO2-MWNTs含量对冷结晶球晶尺寸的影响远小于其对熔体冷却结晶球晶尺寸的。所得结论对优化PLA的结晶结构和性能、制备高性能PLA复合材料具有指导意义。     

纳米碳酸钙改性聚丙烯共聚物的非等温结晶动力学

用DSC手段考察了反应釜内原位共聚制备的含有成核剂及纳米碳酸钙的聚丙烯(PP)共聚物的非等温结晶行为。结果表明，成核剂使PP共聚物的结晶温度升高，结晶度降低，结晶速率略有提高。而纳米碳酸钙则大幅提高了PP共聚物的结晶温度和结晶速率，结晶度也增加了约10％。并采用Ozawa法和Caze法描述了非等温结晶动力学。     

火焰喷涂ETFE涂层的非等温结晶行为

采用火焰喷涂技术制备了乙烯-四氟乙烯共聚物(ETFE)涂层。利用红外光谱仪、接触角测定仪、差示扫描量热仪(DSC)等对涂层的结构、表面性能及非等温结晶、熔融行为进行了分析。结果表明,ETFE粉末在火焰喷涂过程中没有发生氧化降解反应,适宜采用火焰喷涂法制备涂层;涂层的结晶动力学分析表明,用Jeziorny法和Mo法处理其非等温结晶过程比较理想。     

Crystallization behavior of poly(hydroxybytyrate-<Emphasis Type="Italic">co</Emphasis>-valerate) in model and bulk PHBV/kenaf fiber composites

The kinetics of non-isothermal crystallization and melting behavior of poly(hydrohybutyrate-co-valerate) (PHBV) in model, bulk and compatibilized (PHBV)/kenaf fiber composites were investigated using differential scanning calorimetry (DSC). Analysis of the non-isothermal crystallization data was carried out based on the Avrami and Mo’s models. Activation energies of the crystallization process were determined by the Kissinger approach, and were in the range between 41 and 48 kJ/mol for all investigated samples. It was shown that the kenaf fibers, as well as their content, do not affect significantly the crystallization kinetics of PHBV matrix. The results indicate that crystallization behavior of polymer resin in bulk composites is not affected by the melt processing, thus suggesting absence of degradation processes.