加入不同种类成核剂抗冲击共聚PP的非等温结晶动力学

采用差示扫描量热仪研究了加入羧酸盐类成核剂和有机磷酸盐类成核剂的抗冲击共聚聚丙烯2500H的熔融、结晶和非等温结晶行为。结果表明:加入质量分数为0.02%的成核剂后,2500H的结晶度和所有结晶特征温度均提高,其中,结晶度提高0.3%~3.0%,结晶温度提高4.4~11.0℃,结晶起始温度提高4.4~12.2℃,结晶终止温度提高6.3~11.6℃。与加入有机磷酸盐类成核剂的2500H相比,加入羧酸盐类成核剂的2500H具有更低的结晶过冷度,成核能力相对较高;但加入有机磷酸盐类成核剂的2500H表现出更快的结晶速率,而加入羧酸盐类成核剂的2500H虽然在高温条件下能促使2500H较快形成晶核,但并不利于结晶速率的提高。     

成核剂对聚丙烯结晶行为的研究

采用红外光谱、X射线衍射、差示扫描量热仪和偏光显微镜等方法考察了磷酸盐类成核剂(NA)、羧酸盐类成核剂(MD)、松香型成核剂(WA)和山梨醇类成核剂(NX)对均聚聚丙烯的结晶温度、结晶速率等结晶行为的影响。结果表明,由于成核剂的结构不同,其对聚丙烯的结晶速率、结晶温度、结晶度等结晶动力学的影响较大,其中NX成核剂改性聚丙烯的半结晶时间最短,为0.8938min,结晶温度最高达到129.8℃。     

耐热聚丙烯的制备

考察了磷酸盐类成核剂、羧酸盐类成核剂、松香型成核剂和山梨醇类成核剂对聚丙烯结晶行为的影响,选取磷酸盐类成核剂制备了耐热聚丙烯。采用傅里叶变换红外光谱仪、X射线衍射仪、差示扫描量热仪、偏光显微镜等表征了耐热聚丙烯的结构并研究了其耐热性能。结果表明:山梨醇类成核剂和磷酸盐类成核剂对聚丙烯的结晶温度、结晶速率和结晶尺寸影响较大;当磷酸盐类成核剂加入量为600μg/g时,所制耐热聚丙烯的负荷变形温度较高,为119.8℃。     

聚甲醛成核剂研究进展

综述了硅藻土、硅胶、蒙脱土、滑石粉和氮化硼等无机成核剂,聚酰胺、羧酸盐等有机成核剂对聚甲醛(POM)结晶性能和力学性能的影响。由弹性体和滑石粉组成的复合成核剂不仅可使POM的球晶尺寸减小至2.1μm,更重要的是使POM的成型收缩率从3.3%降至2.0%。开发POM成核剂一是要根据POM的结构特征,通过分子设计,合成适合POM专用的系列成核剂;二是通过对现有成核剂的物理或化学复合,开发复合成核剂,发挥不同组分的协同效应。     

POM结晶改性技术研究进展

综述了近年来国内外聚甲醛(POM)结晶改性方面的研究与应用进展，阐述了结晶改性的多种方法及其原理，详细介绍了无机成核剂、有机成核剂、金属类成核剂和复合成核剂对POM的结晶动力学参数、结晶度、结晶速率、球晶尺寸等结晶性能和缺口冲击强度、拉伸强度等力学性能的影响，简述了结晶抑制剂、调整加工工艺在结晶改性方面的研究现状。最后对POM结晶改性的研究方向提出了一些建议。     

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。     

聚丙烯成核剂及其对聚丙烯性能的影响

介绍了聚丙烯（PP）的结晶过程，PP分子的晶体结构对其性能的影响以及成核剂的分类，如二苄又山梨醇衍生物、有机磷酸盐、烷基羧酸盐、松香。综述了成核剂对PP的等温结晶行为、熔融特性、力学性能、耐老化性能、光学性能及加工性能的影响的最近研究成果。     

成核剂对煤基共聚聚丙烯性能影响研究

研究了羧酸类、羧酸盐类、有机磷酸盐类等有机成核剂以及无机成核剂对煤基共聚聚丙烯2500 H流动性能、熔融结晶性能和力学性能的影响。结果表明,添加成核剂能够提高样品的结晶温度、结晶度、拉伸屈服强度和弯曲模量。其中4#成核剂的效果最好,添加量为质量分数0. 05%时,结晶温度提高6. 9℃,结晶度提高18. 6%,拉伸屈服强度、弯曲模量和冲击强度分别提高了12. 3%、14. 4%和5. 2%。     

脱氢枞酸盐透明改性聚丙烯研究

以脱氢枞酸钾和脱氢枞酸钾成核剂对透明聚丙烯（PP）进行改性，研究了脱氢枞酸盐对PP光学性能、力学性能及结晶特性的影响，并与山梨酸类成核剂改性PP的性能进行了比较。实验结果表明，加入脱氢枞酸钾或脱氢枞酸钠后，聚丙烯的雾度大幅度降低，光泽度提高，但透光率变化不大；弯曲模量大幅度提高，而拉伸强度和缺口冲击强度略有下降；球晶尺寸大幅度减小；结晶温度提高，结晶度略有上升。脱氢枞酸盐改性聚丙烯与山梨醇类成核剂改性聚丙烯的性能相当，但脱氢枞酸盐克服了山梨醇类成核剂的缺点，可以作为山梨醇类成核剂的理想替代品。     

新型β成核剂NA对聚丙烯等温结晶行为的影响

合成了一种新型酰胺类β成核剂NA,该成核剂能明显提高聚丙烯的结晶速率,促进聚丙烯结晶。利用广角X射线衍射仪(WXRD)、差示扫描量热仪(DSC)和偏光显微镜(POM)研究了成核剂NA对聚丙烯结晶性能和结晶形态的影响。结果表明,当成核剂质量分数为0.5%时,β晶的相对含量为46.3%。Avrami方程研究表明,聚丙烯复合材料呈现明显的异相成核特征。     

Crystallization morphology and crystallization kinetics of poly(lactic acid): effect of <Emphasis Type="Italic">N</Emphasis>-Aminophthalimide as nucleating agent

The effect of N-Aminophthalimide compound (NA-S) as nucleating agent on crystallization behavior and morphology of poly(lactic acid) was studied. With polarized optical microscope (POM), the unique phenomena of nucleation and epitaxial crystallization of PLA/NA-S system were observed. Dynamic morphology of crystallization was also studied by POM to investigate the relationship between growth behavior of PLA and nucleating agent. Isothermal and non-isothermal crystallization behavior of PLA were studied by differential scan calorimeter (DSC). When nucleating agent was added, a new peak appeared in wide angle X-ray diffraction (WAXD) compared with pure PLA, indicating the nucleating effect of NA-S on crystallization of PLA. All the results indicate that the nucleating agent of NA-S shows obvious nucleating effect on isothermal crystallization above 120 °C and in non-isothermal crystallization after it is added in PLA, that is, the induction crystallization time is reduced, the crystallization rate and nucleation density of PLA are increased.     

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。     

苯基磷酸锌对聚乳酸结晶行为影响的研究

采用DSC,POM研究了成核剂苯基磷酸锌（PPZn）对聚乳酸结晶行为的影响。结果表明：PPZn可以作为聚乳酸的高效成核剂,PPZn的加入显著提高了聚乳酸的结晶速率和结晶度。当PPZn的质量分数为5％0时TCs（起始结晶温度）降低了约24℃,TCe（终止结晶温度）降低了约29℃。PPZn的加入使聚乳酸的半结晶时间大大缩短。当PPZn的质量分数为2％时,结晶速率常数增大约5个数量级。     

成核剂对LLDPE晶体形态及结晶行为的影响

借助原子力显微镜、偏光显微镜和差示扫描量热仪,研究了山梨糖醇类成核剂对线型低密度聚乙烯(LLDPE)晶体形态及结晶行为的影响。结果表明:随着成核剂用量的增加,LLDPE的晶体形态呈均一化,球晶尺寸逐渐减小;成核剂的加入导致了LLDPE结晶温度和结晶度的提高。     

Crystallization characteristics of polyoxymethylene with attapulgite as nucleating agent

The nucleation of polyoxymethylene (POM) crystallization using attapulgite was studied using differential scanning calorimetry, polarized light microscopy, wideangle X‐ray diffration and mechanical testing. Two isothermal crystallization kinetic equations were employed to describe the crystallization of virgin POM and POM containing attapulgite as a nucleating agent. The addition of attapulgite decreased the spherulitic size of POM, and interfacial free energies per unit area perpendicular to the molecular chain direction ρ_e, accelerated the crystallization growth rate and enhanced the impact toughness of POM, but no change occurred for the hexagonal system of POM. The addition of attapulgite up to its saturation concentration in POM increased the number of effective nuclei by three orders of magnitude. A high concentration of attapulgite caused agglomeration of the agent and lowered the number of effective nuclei.     

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     

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.     

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。     

Effect of boron nitride as a nucleating agent on the crystallization of bacterial poly(3‐hydroxybutyrate)

Different concentrations of boron nitride (BN) (0.2–0.8 wt %) are added to poly (3‐hydroxybutyrate) (PHB) as a nucleating agent. Polarized Optical Microscopy (POM) coupled to Differential Scanning Calorimetry (DSC) allow to monitor the isothermal and nonisothermal crystallization of neat and nucleated PHBs. It is found that the addition of BN to PHB modifies the mechanisms of crystallization without changing the crystallinity degree. DSC can replace POM whenever POM does not allow to estimate the spherulites growth rate. The Hoffman‐Lauritzen theory is used to explain the role of BN. The nucleating agent allows polymer crystallization at lower supercooling degrees. The regime II of crystallization is observed for nucleated PHBs. A modification of the coupling effect between the amorphous and the crystalline phases is evidenced. It is shown that a concentration of 0.2 wt % BN is sufficient to decrease the glass transition temperature and modify the crystallization mechanisms of PHB. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effects of crystallization condition on the microstructure and thermal stability of istactic polypropylene nucleated by β‐form nucleating agent

This article deals with the crystallization behaviors of original (prepared in a torque rheometer), DSC crystallization and mold crystallization (quenching and slow nonisothermal crystallization) of isotactic polypropylene (iPP) mixed with β‐form nucleating agent. The microstructure and thermal stability of these samples were investigated. The wide angle X‐ray diffraction (WAXD) results indicate that fast cooling is favorable for β‐form iPP formation. With slower cooling rate and higher concentration of nucleating agent, the lamellar thickness and stability of crystal0s were enhanced. Polarized optical microscopy (POM) and scanning electron microscopy (SEM) both showed that rapid crystallized samples gave rise to tiny spherulites, whereas under slow crystallization condition, nucleated samples could be fully developed in the form of dendritic or transcrystalline structures, depending on the nucleating agent concentration. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011