POM与POM/碳酸钙复合材料非等温结晶动力学研究

采用差示扫描量热仪研究了聚甲醛（POM）和POM /碳酸钙复合材料在不同降温速率下的非等温结晶行为,并用Jeziorny法和莫志深法计算了POM及其复合材料的非等温结晶动力学参数。结果表明：提高降温速率,POM与POM/碳酸钙复合材料的结晶峰均向低温方向移动,且结晶放热峰逐渐变宽;降温速率为5、10、15和20 ℃/min时对应POM/碳酸钙复合材料的结晶峰峰值和结晶放热焓分别为144.6、142.4、141.2、140.2 ℃和177.4、152.2、148.0、137.2 J/g;加入碳酸钙的使POM的结晶温度提高,结晶速率加快,其在体系中起到了异相成核的作用。     

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。     

聚甲醛结晶成核剂研究进展

对国内外聚甲醛(POM)结晶成核剂进行了分类。概述了碳酸钙、滑石粉、硅藻土等无机成核剂,碳纳米管、聚酰胺、均聚甲醛等有机成核剂,氧化镁、超细Fe粉等金属类成核剂及滑石粉/弹性体等复合成核剂对POM结晶性能和力学性能等的影响。对POM成核剂的开发提出了建议。     

成核剂对聚甲醛结构与性能的影响

利用差示扫描量热仪、偏光显微镜和力学性能测试研究了不同成核剂对聚甲醛(POM)结构和性能的影响。结果表明,选用的无机成核剂均能有效地减小POM球晶尺寸,提高POM的结晶峰温度及缺口冲击强度,其中以滑石粉的成核效果最为显著。滑石粉使POM最大结晶温度由141.2℃提高到145.5℃,球晶平均尺寸约为未加成核剂的POM球晶尺寸的1/4,缺口冲击强度从5.12 kJ/m2增加到6.21 kJ/m2。     

改性聚甲醛结晶性能研究

采用差示扫描量热仪和偏光显微镜,对未加成核剂和加入2种不同成核剂A、B的聚甲醛（POM）进行非等温结晶测试、等温结晶动力学研究,得到了在各种条件下的Avrami方程参数(K和n)、半结晶时间(t1/2)及结晶形态。研究表明,POM结晶过程为异相三维生长过程,2种成核剂均能使POM结晶速度加快,缩短了结晶时间,成核剂B效果好于成核剂A。     

纳米碳酸钙增强聚丙烯共聚物

在反应器原位分散共聚中加入成核剂和纳米碳酸钙制备了增强型聚丙烯共聚物。增强型共聚物的冲击强度、弯曲应力和热变形温度大幅提高，拉伸强度也有所增加。同时结晶峰温度显著升高，且半结晶时间明显减少。     

纳米碳酸钙填充尼龙6体系结晶行为的研究

采用偏光显微镜、差示扫描量热仪和广角X射线衍射仪系统地研究了纳米碳酸钙(n-CaCO3)粒子填充聚酰胺6(PA6)体系的结晶行为。结果表明,n-CaCO3粒子的引入不仅使PA6材料变为两相结构,而且使其结晶行为发生了改变;n-CaCO3粒子对PA6等温结晶行为影响较大,球晶尺寸大小及球晶形态发生了很大变化;n-CaCO3粒子不仅具有异相成核剂的作用,而且能引发PA6产生新的晶型,且这种成核作用具有逾渗行为。     

纳米粒子/聚烯烃复合材料的结晶性能研究

报道了无机纳米粒子／聚烯烃复合材料的结晶性能研究。探索了有机成核剂苯甲酸纳、纳米二氧化钛、纳米碳酸钙对聚丙烯(PP)、高密度聚乙烯(HDPE)及其共混物的结晶形态影响，并用差示扫描量热计分析了PP，HDPE和HDPE／PP及其纳米复合材料的结晶性能。结果表明，HDPE／PP共混使HDPE的熔点(Tm)下降，PP的Tm保持不变；成核剂的加入均会使材料的Tm向低温侧移动且结晶度下降；无机纳米粒子对材料晶粒细化作用大大优于有机成核剂，纳米二氧化钛的晶粒细化作用最佳。     

多种成核剂对PBS结晶及力学性能的影响

本文研究了滑石粉、TMB-5、碳酸钙、硫酸钙晶须、高岭土等五种成核剂对聚丁二酸丁二醇酯(PBS)结晶行为及力学性能的影响。偏光显微镜的观察结果显示了成核剂能细化PBS的球晶尺寸,提高球晶排列的规整度;热分析结果表明添加成核剂能提高PBS的结晶温度,加快PBS的结晶速率;结晶性能的改善又直接造成PBS力学性能的提高,其拉伸强度和冲击强度都有明显上升。五种成核剂中以滑石粉的效果最为突出,能使PBS的结晶温度上升11℃,拉伸强度提高了4.4MPa。     

β成核剂对抗冲聚丙烯共聚物的结晶和力学性能研究

分别用α晶型成核剂和β晶型成核剂对抗冲聚丙烯共聚物（iPP）的结晶和力学性能进行研究,并用偏光显微镜（POM）、广角X射线衍射仪（WAXD）和差示扫描量热仪（DSC）对其进行了详细的表征。结果表明,α和β成核剂使iPP的起始结晶温度（ton）提高15.3℃和12.7℃,结晶峰温度（tp）提高17℃和13.7℃,结晶速率加快。两种成核剂都能使球晶细化,使结晶更加均匀化、规整化,从而使结晶度增加。α成核剂（TMA-3）使iPP的拉伸强度、冲击强度和断裂伸长率分别提高到23.43MPa、22.27kJ/m2和788%;β成核剂因主要是改变球晶的形态,形成与α球晶完全不同的β晶型,使iPP的拉伸强度、冲击强度和断裂伸长率的提高比α成核剂显著,分别达到24MPa、32.81kJ/m2和861%。     

成核剂对尼龙结构与性能影响的研究进展

从成核剂的作用机理和尼龙加工条件出发，将尼龙用成核剂分为无机、有机和高分子三类，并分别介绍了其最佳用量、应用情况及对尼龙结构与性能的影响。尼龙用成核剂用量一般要低于5％。成核剂的添加可加快尼龙结晶速率，缩短注塑周期；使球晶颗粒更细微化；改变制品收缩；拉伸强度和弯曲弹性模量增加，耐热性提高，断裂伸长率和冲击强度降低。     

Fabrication of hierarchically crystallographic morphologies in isotactic polypropylene

The hierarchically crystallographic morphologies were fabricated in isotactic polypropylene (iPP) by controlling the stratified distribution of the nucleating agents. The α‐ and β‐nucleating agents were chosen for preparing the different crystalline modifications. The transcrystals and spherulites were found in the stratified distribution samples by polar optical microscopy (POM) and scanning electron microscope (SEM). The transcrystals grew from the surfaces of the nucleating agents filled layers and occupied most space of the pure iPP layers. The crystalline modifications and crystallinity were analyzed by X‐ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The mechanical and thermal degradation properties of these samples with hierarchically crystallographic morphologies were investigated by tensile testing machine and thermogravimetric analysis (TGA) respectively, and showed better than that of the samples with single crystallographic morphology (spherulites). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42703.     

High Efficiency Nucleating Agents of Polyoxymethylene

In this research, the effects of different kinds of nucleating agents on the crystallization and mechanical properties of polyoxymethylene (POM) were studied, including inorganic, organic, and polymer nucleating agents and their compounds. These properties showed that nanoCaCO₃, sorbitol derivative TMB-5, polyamide PA-4, and compound C-1/polyamide (PA)-4 can make spherulites of POM finer and more perfect, and effectively improve its notched impact toughness, in which the compound C-1/PA-4 displayed more remarkable nucleation effect. The study on the nonisothermal crystallization of POM showed that the crystallization temperature and crystallization growth rate of POM increased when C-1/PA-4 was added. The isothermal crystallization kinetics were also analyzed by the Avrami equation. The addition of C-1/PA-4 can increase the values of the Avrami exponent (n) and crystallization rate constant (k), and reduce the half-time of isothermal crystallization, t_1/2, and the time corresponding to the maximum rate of crystallization, t_P, indicating its remarkable nucleating effect on POM.     

PP／PET／EPDM-g-GMA共混物结构与性能研究

通过反应共混制备了PP／PET／EPDM—g-GMA共混物。用扫描电镜和图像处理软件对共混物形貌进行定性和定量分析，用偏光显微镜观察共混物等温结晶形态，最后测量共混物的力学性能。结果表明：在PP／PET共混物中加入EPDM-g—GMA后，两相相容性改善，进一步加入成核剂后分散相尺寸更小、粒径分布更均匀；PP球晶随PET的混入而减小；在PP／PET体系中加入EPDM-g—GMA起到反应增容和橡胶增韧的协同效应，使缺口冲击强度由未加增容剂时的2．0kJ／m^2提高至6．6k．1／m^2，弹性模量较PP提高了38％；PP／PET共混物的拉伸强度随PET含量的增加下降，在相同PET含量的情况下，加入EPDM—g-GMA后，共混物的拉伸强度与未增容体系基本一致。     

成核剂TM-3与苯甲酸钠对聚丙烯力学性能的影响比较

研究和对比了透明成核剂TM-3与普通成核剂苯甲酸钠(SB)对聚丙烯(PP)力学性能的影响,结果发现:TM-3与SB对PP的力学性能的影响有很大不同;随着成核剂含量的提高,PP/TM-3体系拉伸屈服强度基本不变化,而PP/SB体系出现了小小的波动,先下降后上升;PP/TM-3体系缺口冲击强度随成核剂含量增加呈线性增长,而PP/SB体系在苯甲酸钠含量为1%(质量分数)时出现了极大值;PP/TM-3体系弯曲强度随成核剂含量增加先下降而后上升,但PP/SB体系也是在苯甲酸钠含量为1%(质量分数)时出现极大值。另外,还研究了两种体系改性PP的断裂伸长率和成型收缩率。     

Isothermal crystallization behavior of polyoxymethylene with and without nucleating agents

Nucleation effects of two silicate nucleating agents, attapulgite and diatomite, on the crystallization of polyoxymethylene (POM), were studied by means of differential scanning calorimetry and polarized optical microscopy. The crystallization kinetics of POM with and without nucleating agents was analyzed by means of two isothermal crystallization kinetic equations through the crystallization thermograms. Compared with virgin POM, POM with nucleating agents of attapulgite and diatomite decreased the spherulitic size of POM and interfacial free energies per unit area perpendicular σ_e. The crystallization growth rate was accelerated because of nucleating agents as well. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 304–310, 2001     

成核剂对超微细滑石粉／聚丙烯共混物性能的影响

研究了α和β成核剂对滑石粉／聚丙烯共混物力学性能的影响。结果表明：α成核剂可以提高材料的拉伸强度、弯曲强度、弯曲模量和硬度等,冲击强度略有下降,而β成核剂使其韧性明显增强;α和β成核剂的加入皆使复合体系的耐热性显著提高,与β成核剂相比,β成核剂更能提高共混物的热变形温度。     

β成核剂含量对等规聚丙烯性能的影响

研究了一种β成核剂(CHB-5)的含量对等规聚丙烯(iPP)结晶性能和力学性能的影响。用广角X射线衍射(WAXD)研究CHB-5诱导iPP晶型的变化,用差示扫描量热法(DSC)分析CHB-5对iPP熔融行为和结晶行为的影响,用偏光显微镜(POM)观察CHB-5诱导iPP结晶形态的变化。结果表明,CHB-5的加入使iPP的成核能力增强;CHB-5可降低iPP的熔融温度,提高其结晶温度和结晶起始温度,加快结晶速率;CHB-5能降低球晶尺寸;CHB-5的加入可使iPP缺口冲击强度提高。     

Synergistic toughening effects of nucleating agent and ethylene–octene copolymer on polypropylene

The synergistic toughening effect of nucleating agent (NA) and ethylene–octene copolymer (POE) on polypropylene was studied in the present work. Two different nucleating agents, such as α-form nucleating agent 1,3 : 2,4-bis (3,4-dimethylbenzylidene) sorbitol (DMDBS, Millad 3988) and β-form nucleating agent aryl amides compounds (TMB-5), were selected to blend with PP or PP/POE blends, respectively. The results show that PP containing 0.5–0.25 wt % DMDBS or 0.5–0.25 wt % TMB-5 has relatively low impact strength. For PP/POE blends, although the impact strength increases gradually with the increasing of POE content, high content of POE is needed to obtain the available PP toughness. However, once nucleating agent and POE are simultaneously added into PP, PP/POE/NA blends show great improvement of toughness even at low POE content. Furthermore, the synergistic toughening effect of POE/TMB-5 is more apparent than that of POE/DMDBS. SEM results show that whether DMDBS or TMB-5 has no apparent effect on the morphologies of POE in the PP/POE/NA blends. Further investigations using DSC and POM indicate that both DMDBS and TMB-5 induce the apparent enhancement of the crystallization temperature of PP and the sharp decrease of spherulites size of PP in the PP/POE/NA blends. The possible synergistic toughening mechanism is discussed in the work. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008