成核剂对PHBV等温结晶行为的影响

用DSC方法测定了氮化硼及滑石粉成核剂对(β-羟基丁酸酯-与-β-羟基戊酸酯) 共聚物(简称PHBV)等温结晶行为的影响. 结果表明,Avrami方程指数n、成核机理、晶体生长方式基本上不受成核剂的影响.少量的成核剂可使结晶成核自由能降低,结晶速率加大,其中氮化硼的效果最为显著.     

纤维素芳族酯热致液晶对PET结晶成核作用的研究

用自制的热致液晶性纤维素芳族酯(CAE)作聚对苯二甲酸乙二醇酯(PET)的成核剂,研究了PET/CAE体系(CAE含量≤1%)在110～200℃温度范围内的等温结晶动力学特性.结果表明,CAE能显著加快PET结晶速率(Z),Z随结晶温度和CAE含量变化均有极大值Z_max(T_C)和Z_max(W_CAE),Z_max(T_C)对应的温度T_max随CAE含量增加而降低,CAE促进PET结晶的作用机理与普通成核剂不同.     

成核剂含量对β晶相聚丙烯结晶与熔融行为的影响

用DSC研究了β成核剂含量对β聚丙烯在等温与非等温结晶条件下的结晶与熔融行为的影响,发现当成核剂含量为0.005％时,结晶焓△H_c、β晶的熔融焓△H_(mβ)及熔点T_(mβ)均为最大,而α晶的相对含量最小.广角X-衍射数据表明,成核剂含量高的试样的(301)衍射峰的相对强度下降,反映分子链排列的纵向有序性降低.根据聚丙烯分子在β成核剂上附生结晶的成核机理解释了上述结果.     

轻质碳酸钙／聚丙烯共混物中聚丙烯β－晶的成核结晶研究

用Ｘ射线衍射和差示扫描量热法研究了轻质碳酸钙／聚丙烯共混物（Ｌ－ＣａＣＯ３／ＰＰ）中ＰＰβ－晶的成核结晶现象，发现ＰＰβ－晶的成核结晶与ＰＰ的来源和Ｌ－ＣａＣＯ３在共混物中的含量有关，铝酸酯偶联剂对共混体系的ＰＰβ－晶的成核结晶有显著的增强作用．分析认为共混物中ＰＰβ－晶的成核结晶现象是ＰＰ中存在的某些杂质（主要是催化剂残余物）与Ｌ－ＣａＣＯ３组成的复合成核剂作用的结果，而铝酸酯是这种复合成核剂的一种促进剂．     

成核剂和促进剂对聚对苯二甲酸乙二酯结晶的影响

研究了一种成核剂和结晶促进剂及其混合物对聚对苯二甲酸乙二酯（ＰＥＴ）结晶过程和熔融行为的影响．结果表明,成核剂的引入降低了ＰＥＴ的结晶成核界面自由能,起到促进ＰＥＴ结晶成核的作用,从而加快了ＰＥＴ的结晶速度．而结晶促进剂对ＰＥＴ的结晶速度影响很小,不能促进ＰＥＴ的成核结晶,但能使ＰＥＴ结晶更完善,使ＰＥＴ的结晶度提高．当两者并用时,ＰＥＴ由熔体降温的结晶行为主要由成核剂控制,而成核促进剂的作用不明显．     

聚β-羟基丁酸酯顺丁烯二酸酐接枝共聚物的等温结晶动力学和熔融行为

采用DSC方法对聚 β 羟基丁酸酯顺丁烯二酸酐接枝共聚物 (PHB g MA)的等温结晶动力学和熔融行为进行了研究 .结果表明 ,顺丁烯二酸酐的引入使得聚 β 羟基丁酸酯的结晶能力下降 ,但是并没有改变它的结晶成核机理和生长方式 .随着接枝率的增加 ,结晶活化能增加 .等温结晶后的PHB g MA表现出双熔融行为 ,这是在升温过程中发生熔融重结晶的结果     

轻质碳酸钙／聚丙烯共混物中聚丙烯β—晶的成核结晶研究

用Ｘ射线衍射和差示扫描量热法研究了轻质碳酸钙／聚丙烯共混物（Ｌ－ＣａＣＯ３／ＰＰ）中ＰＰβ－晶的成核结晶现象，发现ＰＰβ－晶的成核结晶与ＰＰ的来源和Ｌ－ＣａＣＯ３在共混物中的含量有关，铝酸酯偶联剂对共混体系的ＰＰβ－晶的成核结晶有显著的增强作用。分析认为共混物中ＰＰβ－晶的成核结晶现象是ＰＰ中存在的某些杂质（主要是催化剂残余物）与Ｌ－ＣａＣＯ３组成的复合成核剂作用的结果，而铝酸酯是这种复合成核剂的     

稀土β-成核剂对1-丁烯本体聚合和产物聚(1-丁烯)结晶性能的影响

采用Ziegler-Natta催化剂催化1-丁烯本体聚合,稀土β-成核剂经原位聚合的方法加入到体系,并考察成核剂加入量对产物聚(1-丁烯)的分子量和结晶性能的影响.通过凝胶渗透色谱(GPC)、示差扫描量热仪(DSC)、偏光显微镜(POM)和广角X射线衍射仪(WAXD)对聚合物进行表征分析.实验结果表明,随着稀土β-成核剂加入量的增大,催化剂活性有所下降,聚合物等规度略有提高,而聚合的分子量显著提高,分子量分布变窄;聚合时成核剂的加入提高了聚(1-丁烯)的结晶性能,随着成核剂加入量的增多聚合物晶粒变小且尺寸趋向均一化,聚合物结晶度也得到了提高,当成核剂加入量为30 mg时,聚合物结晶度和熔融焓出现突变现象.此外,稀土β-成核剂的加入会改变熔融前聚(1-丁烯)中晶型Ⅰ’和Ⅲ所占比例从而影响聚合物的熔点,成核剂的存在也改变了晶型II向晶型I的转变速率,缩短了晶型转变周期.     

β晶型成核剂对聚丙烯力学及结晶性能的影响

研究了N,N′-二环己胺基对苯二酰胺作为β成核剂对聚丙烯(PP)力学性能及结晶性能的影响。结果表明,成核剂具有使聚丙烯增韧的优异性能,当添加质量分数为0.3%时,其抗冲击强度由原来的36.06 J/m2提高到65.79 J/m2。DSC研究表明,添加β成核剂可以诱导PP中β晶生成。考察了冷却速率对结晶温度的影响,当冷却速率为10℃/m in时,结晶温度从118.38℃提高到124.53℃,表明该成核剂的加入使结晶向高温方向偏移,结晶速度加快。     

聚对苯二甲酸1,3-丙二酯的自晶种成核等温结晶动力学

研究了自晶种成核对聚对苯二甲酸1,3-丙二酯(PTT)结晶行为的影响.示差扫描量热结果表明,经过自晶种成核处理后,PTT的结晶温度明显增加.应用Avrami方程分析了PTT等温结晶动力学,Avrami指数n的平均值为3.34,表明初级结晶为三维球晶生长.自晶种成核导致结晶活化能和链折叠功减小,促进PTT的结晶.     

β-羟基丁酸与β-羟基戊酸共聚物 (PHBV)/蒙脱土纳米复合材料的等温结晶动力学

用差热量热分析（DSC）方法研究了β－羟基丁酸与β－羟基戊酸共聚物（PHBV）／蒙脱土纳米复合材料的等温结晶行为。结果表明，PHBV的Avrami方程指数n、成核机理、结晶生长方式基本不受蒙脱土的影响，加入少量的蒙脱土可明显降低PHBV结晶成核自由能，使其结晶速率增大。     

茂金属间规立构聚丙烯结晶动力学研究

用ＤＳＣ和密度法对茂金属间规立构聚丙烯（ｓＰＰ）样品进行了等温和非等温结晶动力学研究．测得平衡熔点Ｔ０ｍ为１５８℃,平衡熔融热焓ΔＨ０ｍ为３７ｋＪ／ｍｏｌ,侧表面自由能σ＝５２ｅｒｇ／ｃｍ２,折叠链表面自由能σｅ＝６９ｅｒｇ／ｃｍ２,链堆砌功ｑ＝３３７５ｋＪ／ｍｏｌ．对非等温结晶过程研究表明,由熔体结晶的ｓＰＰ具有非均相成核,三维球状生长机理．成核与生长活化能ΔＥ＝７３１ＫＪ／ｍｏｌ     

GMA/苯乙烯多组分单体接枝聚丙烯结晶行为研究

使用差示扫描量热计 (DSC)研究了甲基丙烯酸缩水甘油酯 苯乙烯 (GMA St)多单体熔融接枝聚丙烯[PP g (GMA co St) ]的等温和非等温结晶行为 ,用偏光显微镜观察了结晶的形态 ,并利用Avrami方程对其结晶动力学进行了分析 .研究发现接枝聚丙烯的结晶模式与PP相似 ,属于异相成核控制的球晶三维生长 ;但接枝聚丙烯的结晶温度 (Tc)显著提高 ,幅度高达 16～ 19℃ ,总结晶速率与纯PP相比明显加快 .接枝聚丙烯上GMA co St支链的存在 ,降低了成核界面自由能 ,促进了聚丙烯结晶的异相成核 .在接枝率不太高的情况下 ,随着接枝率的提高 ,接枝聚丙烯的结晶温度升高 ,总结晶速率加快 .在高接枝率范围内 ,随着接枝率的提高 ,接枝PP的Tc 不再升高 ,且由于接枝链的增长严重阻碍了球晶生长 ,导致接枝PP的总结晶速率反而随接枝率的升高而下降     

Effect of wood flour as nucleating agent on the isothermal crystallization of poly(lactic acid)

The effect of wood flour (WF) as an efficient nucleating agent on the isothermal melt crystallization and isothermal cold crystallization behavior of poly(lactic acid) (PLA) was investigated by differential scanning calorimeter and polarized optical microscopy. It was found that the incorporation of 4 wt% WF promoted the crystallization of PLA about 4.2%. Polarized optical microscopy results showed the Maltese cross of the samples. The presence of the 4 wt% WF may increase the nucleation density, leading to the increase of the spherulites; however, the size of the spherulites decreased, and the structure became incomplete. The Avrami model was applied to analyze the isothermal crystallization kinetics. It is concluded that the addition of WF modified the crystallization process of PLA (the value of Avrami exponent changed). Various parameters, such as the crystallization half time and crystallization rate constant, reflect that 4 wt% WF significantly improves the crystallization process. The observations in this article indicate that WF is an efficient nucleating agent of PLA. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of different nucleating agents on crystallization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerates)

In this study, thymine and melamine were introduced as nucleating agents for poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerates) (PHBVs) and poly(3‐hydroxybutyrate) (PHB), and their effects were compared with that of boron nitride (BN). Because the overall crystallization rate of PHBVs decreases significantly with the increase in the 3‐hydroxyvalerate comonomer content, the study focused on the crystallization of PHBVs. Isothermal crystallization kinetics of the neat PHBVs and the nucleated PHBVs were studied by differential scanning calorimetry (DSC). The Avrami equation was derived and the parameters were assessed for the nucleation and crystal growth mechanism. The nucleation and crystal growth were examined using polarized optical microscopy. All nucleating agents had similar particle sizes and showed good dispersion in the polymer matrix, as revealed by scanning electron microscopy. The results indicated that BN and thymine significantly increased the overall crystallization rate for all PHBVs studied and demonstrated very similar nucleating effects. Melamine reacted with PHBVs and accelerated the thermal degradation, and hence was less effective in nucleating PHBVs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1564–1577, 2007     

聚醚醚酮及其碳纤维复合材料——恒温结晶动力学的研究

本文研究了聚醚醚酮(PEEK)和以PEEK树脂为基体的碳纤维复合材料(APC-2)在恒温条件下的结晶行为。采用差示扫描量热仪(DSC)测定从熔体和橡胶体结晶过程中热焓的变化。利用Avrami方程分析了PEEK和APC-2试样的恒温结晶动力学。PEEK从熔体和橡胶体结晶的活化能分别为532.1和531.7KJ/mol,Avrami指数的平均值分别为5.0和3.9;而APC-2则分别为444.2和432.5KJ/mol,3.5和2.3。这些实验结果表明,APC-2试样中碳纤维表面对PEEK树脂基体具有显著的成核作用,能降低其结晶活化能,因而导致PEEK树脂基体结晶速率加快和促进其结晶更加完整。     

Isothermal and nonisothermal cold crystallization kinetics of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/functionalized eggshell powder composites

Functionalized eggshell powder (NES) with nucleating surface of calcium phenylphosphonic acid (PPCa) for poly(l-lactide) (PLLA) was compounded with PLLA via melt blending to improve the cold crystallization process of PLLA. The cold crystallization behavior of the PLLA/NES composites was studied by differential scanning calorimetry. The isothermal cold crystallization rates have been enhanced obviously in the PLLA/NES composites than in the neat PLLA, indicative of the excellent nucleating effects of NES on PLLA. For the nonisothermal cold crystallization, the overall crystallization rate of PLLA increased with both increasing NES loadings and heating rate. It was found that the Avrami equation and the combined Ozawa–Avrami model could describe the experiment data successfully.     

PET/LCP反应性共混物的非等温结晶动力学

采用DSC方法研究了聚对苯二甲酸乙二酯 (PET)和热致性液晶共聚酯 6 0PHB PET (LCP)体系在少量扩链剂双 (2 唑啉 ) (BOZ)存在下形成的反应性共混物的非等温结晶动力学 .结果表明反应性共混物的Avrami指数均在 3 0～ 4 5之间 ,BOZ的加入使反应共混物中PET组分的结晶速率降低 ;表明BOZ对酯交换的促进作用 ,使所生成的共聚酯中PET嵌段的数均序列长度变短 ,而使结晶在某种程度上较为困难 ,但对体系的成核和结晶生长机理无明显影响 .结果还表明 ,随冷却速率的增大结晶峰向低温方向移动     

Crystallization behavior of polypropylene with or without sodium benzoate as a nucleating agent

The crystallization kinetics of polypropylene (PP) with or without sodium benzoate as a nucleating agent were investigated by means of DSC and polarized optical microscopy in isothermal and nonisothermal modes. A modified Avrami equation was applied to the kinetic analysis of isothermal crystallization. The addition of the nucleating agent up to its saturation concentration increased the crystallization temperature by 15 °C and shortened both the isothermal and nonisothermal crystallization half‐times. It was concluded that the sodium benzoate acted as a good nucleating agent for α‐form PP. By adding the nuclefier to PP, adequately controlled spherulites increased the mechanical properties including especially the Izod impact strength and shortened cycle time of PP. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1001–1016, 2001     

Carbon nanoparticles as effective nucleating agents for polypropylene

The effect of four nucleating agents on the crystallization of isotactic polypropylene (iPP) was studied by differential scanning calorimetry (DSC) under isothermal and non-isothermal conditions. The nucleating agents are: carbon nanofibers (CNF), carbon nanotubes (CNT), lithium benzoate and dimethyl-benzylidene sorbitol. Avrami?s model is used to analyze the isothermal crystallization kinetics of iPP. Based on the increase in crystallization temperature (T _c) and the decrease in half-life time (τ_½) for crystallization, the most efficient nucleating agents are the CNF and CNT, at concentrations as low as 0.001 mass%. Sorbitol and lithium benzoate show to be less efficient, while the sorbitol needs to be present at concentrations above 0.05 mass% to even act as nucleating agent.