取代芳基磷酸金属盐类成核剂对聚乳酸结晶的影响

通过示差扫描量热仪（DSC）和偏光显微镜（POM）考察了取代芳基磷酸金属盐类成核剂对聚乳酸结晶行为的影响。结果表明：取代芳基磷酸一价盐和三价盐可以较好的改善聚乳酸的结晶，其中取代芳基磷酸锂盐的效果最好，使结晶温度提高了4℃。取代芳基磷酸二价盐对于聚乳酸结晶的改善并不明显。对取代芳基磷酸金属盐类成核剂浓度效应的研究发现：1％为其在聚乳酸中的饱和添加浓度。针对滑石粉和取代芳基磷酸锂盐进行了复配研究，发现复配后的成核剂可以更好的促进聚乳酸的结晶。     

取代芳基钛酸钠在等规聚丙烯中的成核作用研究

采用差示扫描量热仪（DsC）、广角X射线衍射（WAXD）以及偏光显微镜（POM）研究了新型成核剂取代芳基钛酸钠（TBP—Na）对聚丙烯晶体类型以及球晶尺寸的影响，并测试了所改性聚丙烯的力学性能。结果表明TBP-Na可以作为聚丙烯的。晶型成核剂使用，并且其通过细化聚丙烯球晶起到了改善聚丙烯宏观力学性能的作用，当其在聚丙烯中的添加量为0．2％（质量）时，可以使聚丙烯的拉伸强度和弯曲模量分别提高8．4％和23．2％。     

等规聚丙烯的结晶成核剂

本文介绍了等规聚丙烯α型、β型结晶和成核剂及应用,成核剂与制品透明性、成型收缩、光泽、耐热性能的关系。指出等规聚丙烯的结晶行为对其加工和制品质量及性能关系重大,通过结晶成核剂进行结晶行为改性,可开发高透明、高光泽、耐热、低收缩和后变形小等新品种聚丙烯塑料。     

浅析成核剂在聚丙烯中的作用

添加成核剂是一种有效的聚丙烯改性方法。聚丙烯成核剂可使聚丙烯结晶度增加、结晶细微化,提高其机械性能等。本文通过介绍聚丙烯成核剂的种类,特性,浅析了成核剂在聚丙烯中作用及其发展。     

聚丙烯成核剂研究进展

介绍了聚丙烯成核剂的种类及其对聚丙烯结晶性能的影响；对国内外聚丙烯成核剂的研究进展和应用前景进行丁综述。     

三种有机成核剂成核聚丙烯的非等温结晶动力学研究

采用DSC研究了聚丙烯（PP）和三种有机成核剂成核的PP在不同的降温速率下的非等温结晶动力学。用Avrami对DSC的测试结果进行了分析。结果表明,三种有机透明成核剂能显著提高PP的结晶温度和结晶速率。可以用修正Avrami方程的Jeziorny法来处理三种有机成核剂成核PP的非结晶等温结晶行为,处理结果表明：三种有机成核透明成核剂成核PP的半结晶时间减少,结晶动力学常数(Zc)增加,结晶速率增加;松香型成核剂能最快提高PP的结晶速率;同一降温速率下,三种有机成核透明剂成核PP的n值较纯PP减少,结晶成核方式发生了改变。     

成核剂改性聚丙烯技术

分析了添加成核剂的改性效果,介绍成核剂的种类,分析了添加成核剂后聚丙烯性能的改变,还简单介绍了目前研究热点β成核剂。     

成核剂对等规聚丙烯透明度及结晶形态的影响

研究了二(对甲氧基苯亚甲基)山梨糖醇和二苯亚甲基山梨糖醇两种成核剂的结晶形态,以及前者对等规聚丙烯结晶形态的影响.结果表明,后者消光环是由于晶片间相互搭接的边界而形成;二者都能形成类似等规聚丙烯的负球晶;少量前者的加入使等规聚丙烯中形成比纯等规聚丙烯“辐条”状球晶小得多的粒状结晶,从而显著提高了等规聚丙烯制品的透明度.     

β晶成核剂己二酸锌对等规聚丙烯成核效应的影响

合成了一种高效高选择性的等规聚丙烯(PP)β晶成核剂己二酸锌(Adi-Zn),研究了其用量对等规PP成核效应的影响。力学性能测试结果表明,随Adi-Zn用量增加,PP的冲击强度先升高后趋于稳定,当Adi-Zn用量为PP质量的0.6%时,成核PP的冲击强度达到最大,是未加Adi-Zn时的1.8倍,而拉伸强度和弯曲弹性模量略有降低。采用广角X射线衍射分析了Adi-Zn对PPβ晶型含量的影响,结果表明,Adi-Zn用量为PP质量的0.2%~0.8%时,β晶型含量保持在95%左右,说明Adi-Zn具有较高的成核效率和选择性。利用差示扫描量热仪和偏光显微镜考察了Adi-Zn对PP结晶温度和晶体形态的影响,结果表明,当Adi-Zn用量达到PP质量的0.6%时,成核PP的结晶温度提高了3.1℃。同时随着Adi-Zn的用量增加,Adi-Zn诱导生成了更多的高亮β晶型,并且明显细化了球晶尺寸。     

不同成核剂成核聚丙烯的结晶行为与力学性能

制备了６种成核剂成核聚丙烯（ＰＰ）母料研究了成核母料和成核母料／ＰＰ的结晶,熔融行为,力学性能和透明性等物理性能,不同成核在成核母材料和成核母料／ＰＰ中对ＰＰ的结晶与熔融行为以及性能有不同的作用,观察到成核型Ａ成核ＰＰ具有较高的结晶温度与综合性能,而成核剂Ｂ成核ＰＰ的透明性较好。     

Isothermal and nonisothermal crystallization kinetics of isotactic polypropylene nucleated with substituted aromatic heterocyclic phosphate salts

The crystallization kinetics of isotactic polypropylene (iPP) and nucleated iPP with substituted aromatic heterocyclic phosphate salts were investigated by means of a differential scanning calorimeter under isothermal and nonisothermal conditions. During isothermal crystallization, Avrami equation was used to describe the crystallization kinetics. Moreover, kinetics parameters such as the Avrami exponent n, crystallization rate constant Z_t, and crystallization half‐time t_1/2 were compared. The results showed that a remarkable decrease in t_1/2 as well as a significant increase in overall crystallization rate was observed in the presence of monovalent salts of substituted aromatic heterocyclic phosphate, while bivalent and trivalent salts have little effect on crystallization rate of iPP. The addition of monovalent metal salts could decrease the interfacial free energy per unit area perpendicular to PP chains σ_e value of iPP so that the nucleation rate of iPP was increased. During nonisothermal crystallization, Caze method was used to analyze the crystallization kinetics. It also showed that monovalent metal salts had better nucleation effects than bivalent and trivalent metal salts. From the obtained Avrami exponents of iPP and nucleated iPP it could be concluded that the addition of different nucleating agents changed the crystal growth pattern of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3307–3316, 2006     

Effects of substituted aromatic heterocyclic phosphate salts on properties,crystallization, and melting behaviors of isotactic polypropylene

Nucleation effects of 2,2′‐methylene‐bis (4,6‐di‐tert‐butylphenyl) phosphate metal salts as a nucleating agent for isotactic polypropylene (iPP) were investigated with differential scanning calorimeter and polarized optical microscope, and their effects on mechanical, optical, and heat resistance properties of iPP were also studied. The results showed that monovalent metal salts of substituted aromatic heterocyclic phosphate such as sodium salt, lithium salt, and potassium salt had a good performance. With 0.2 wt % of sodium salt, lithium salt, or potassium salt incorporated into iPP, the crystallization peak temperature of iPP could be increased by 13.5, 13.6, and 15.0°C, respectively; the mass fraction of crystallinity of iPP could be increased by about 5%; and crystallization rate was enhanced increasingly. Meanwhile the tensile strength and flexural modulus of iPP could be increased by about 10 and 30%, respectively, and the clarity and heat distortion temperature of iPP could also be improved significantly. But bivalent and trivalent metal salts of substituted aromatic heterocyclic phosphate had little effect on properties of iPP. Meanwhile the morphology study showed that the addition of monovalent sodium salt could decrease the spherulite size of iPP significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4868–4874, 2006     

Effect of nucleating agent addition on crystallization of isotactic polypropylene

The isothermal and nonisothermal crystallization kinetics of nonnucleated and nucleated isotactic polypropylene (iPP) were investigated by DSC and a polarized light microscope with a hot stage. Dibenzylidene sorbitol (DBS) was used as a nucleating agent. It was found that the crystallization rate increased with the addition of DBS. The influence of DBS on fold surface energy, σ_e, was examined by the Hoffman and Lauritzen nucleation theory. It showed that σ_e decreased with the addition of DBS, suggesting that DBS is an effective nucleating agent for iPP. Ozawa's theory was used to study the nonisothermal crystallization. It was found that the crystallization temperature for the nucleated iPP was higher than that for nonnucleated iPP. The addition of DBS reduced the Ozawa exponent, suggesting a change in spherulite morphology. The cooling crystallization function has a negative exponent on the crystallization temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2089–2095, 1998     

A novel highly efficient β‐nucleating agent for isotactic polypropylene

A novel highly efficient β‐nucleating agent for isotactic polypropylene (iPP), hexahydrophthalic barium (HHPA‐Ba), was found and its effects on the mechanical properties, the β‐phase content, and crystallization behavior of iPP were investigated, respectively. The results show that the β‐phase content of nucleated iPP (k_β value) can reach 80.2% with 0.4 wt % HHPA‐Ba. The impact strength and crystallization peak temperature of nucleated iPP are greatly increased. Compared with pure iPP, the impact strength of nucleated iPP can increase 2.4 times. Meanwhile, the spherulite size of nucleated iPP is dramatically decreased than that of pure iPP. The Caze method was used to investigate the nonisothermal crystallization kinetics of nucleated iPP and the crystallization active energy was achieved by Kissinger method. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

β‐Nucleation of pimelic acid supported on metal oxides in isotactic polypropylene

To investigate the nucleation of metal pimelate for isotactic polypropylene (iPP) crystallization, iPP filled with a series of metal oxides with and without metal pimelate on their surface was prepared. There was a chemical reaction between pimelic acid (PA) and metal oxides MgO, CaO, BaO or ZnO, but not TiO₂. The corresponding metal pimelate formed by the chemical reaction between PA and MgO, CaO, BaO or ZnO had a different influence on the crystallization behavior and melting characteristics of iPP. Addition of metal oxides increased the crystallization temperature of iPP and mainly formed α‐phase due to the heterogeneous α‐nucleation of metal oxides. The α‐nucleation of CaO could be easily changed into β‐nucleation using CaO‐supported PA, and 90.1% β‐phase was obtained. The β‐nucleation of BaO could be markedly enhanced by barium pimelate formed using supported PA. However, no β‐phase was observed for iPP filled with MgO‐ or ZnO‐supported PA. The various metal oxides with supported PA had a different influence on the crystallization behavior and melting characteristics of iPP due to the different structure of metal pimelate formed by chemical reaction between PA and the metal oxides. Copyright © 2012 Society of Chemical Industry     

Effect of an organic dicarboxylic acid salt on fractionated crystallization of polypropylene droplets

The effect of a particulate nucleating agent on fractionated crystallization of polypropylene (PP) was studied. A novel method utilizing breakup of PP nanolayers was used to obtain a dispersion of PP droplets in a polystyrene (PS) matrix. An assembly with hundreds of PP nanolayers alternating with thicker PS layers was fabricated by layer‐multiplying coextusion. The concentration of an organic dicarboxylic acid salt (HPN) nucleating agent in the coextruded PP nanolayers was varied up to 2 wt %. When the assembly was heated into the melt, interfacial driven breakup of the thin PP layers produced a dispersion of PP particles in a PS matrix. Analysis of optical microscope images and atomic force microscope images indicated that layer breakup produced a bimodal particle size distribution of submicron particles and large, micron‐sized particles. Almost entirely submicron particles were obtained from breakup of 12 nm PP layers. The fraction of PP as submicron particles dropped dramatically as the PP nanolayer thickness increased to 40 nm. Only large, micron‐sized particles were obtained from 200 nm PP nanolayers. The crystallization behavior of the particle dispersions was characterized by thermal analysis and wide angle X‐ray diffraction. Only part of the PP was nucleated by HPN. It was found that HPN was not effective in nucleating the population of submicron particles. The particulate HPN was too large to be accommodated in the submicron PP particles. On the other hand, the amount of nucleated crystallization qualitatively paralleled the fraction of PP in the form of large, micron‐sized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A novel β‐nucleating agent for isotactic polypropylene

The nucleating ability of p‐cyclohexylamide carboxybenzene (β‐NA) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry, X‐ray diffraction, polarized optical microscopy and scanning electron microscopy. β‐NA is identified to have dual nucleating ability for α‐iPP and β‐iPP under appropriate kinetic conditions. The formation of β‐iPP is dependent on the content of β‐NA. The content of β‐phase can reach as high as 96.96% with the addition of only 0.05 wt% β‐NA. Under non‐isothermal crystallization the content of β‐iPP increases with increasing cooling rate. The maximum β‐crystal content is obtained at a cooling rate of 40 °C min^–1. The supermolecular structure of the β‐iPP is identified as a leaf‐like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β‐NA. Under isothermal crystallization β‐crystals can be formed in the temperature range 80–140 °C. The content of β‐crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry     

Effect of β-nucleating agents on crystallization and melting behavior of isotactic polypropylene

Two kinds of β-nucleating agents, named a rare earth complex (WBG) and a N,N′-dicyclohexylterephthalamide (TMB5), were introduced into isotactic polypropylene (iPP), and their effect on crystallization and melting behavior of iPP was comparatively investigated. Wide angle X-ray diffraction measurements revealed that both the two additives were highly effective in inducing β modification. At their respective optimum concentrations of 0.08 wt % for WBG and 0.06 wt % for TMB5, the relative amount of β-form calculated by Turner-Jones equation both exceeds 92%. However, the isothermal crystallization kinetics investigated by differential scanning calorimetry demonstrated that WBG had more pronounced effect than TMB5 in accelerating the overall crystallization rate. The Lauritzen–Hoffman theory analysis also revealed that WBG was more effective not only in increasing the nucleus number but also in accelerating the growth rate of crystallization. After completing isothermal crystallization process, the subsequent melting behavior examination suggested that the addition of WBG expanded the upper limit temperature of forming β modification, and therefore was more effective in delaying the β-α transformation than TMB5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyolefins containing 1,3‐disubstituted cyclopentane units as nucleating agents for isotactic polypropylene

Polyolefins containing 1,3‐disubstituted cyclopentane units in the main chain have been synthesized by 1,3‐polymerization of cyclopentene (PCP), cyclization polymerization of 1,5‐hexadiene (PHD), and ring‐opening metathesis polymerization of norbornene following hydrogenation of the unsaturated main chain (H‐PNB) with various transition metal catalysts. These polyolefins were applied to nucleating agents for isotactic polypropylene, and relationship between the structure of the polyolefins and nucleating effect was studied by DSC, polarized optical microscope, and WAXD. All the polyolefins had an effect of nucleation for isotactic polypropylene (PP). Of the polymeric nucleating agents, H‐PNB showed the most effective nucleation. Addition of PCP, which was obtained with a nickel catalyst with diimine ligand, to PP induced β‐modification. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2953–2958, 2006     

Combined effect of organic phosphate sodium and nanoclay on the mechanical properties and crystallization behavior of isotactic polypropylene

Combined effect of α‐nucleating agent (NA) sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl) phosphate (NA11) and nanoclay (NC) on the mechanical properties and crystallization behavior of isotactic polypropylene (iPP) was investigated by mechanical testing, wide‐angle X‐ray scattering (WAXD), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and scanning electron microscopy (SEM). The mechanical testing results indicated that the separate addition of NA11 and NC only increased the stiffness of iPP while the combined addition of NA11, NC, and maleic anhydride grafted polypropylene (PP‐g‐MA) simultaneously improved stiffness and toughness of iPP. Compared to pure iPP, the tensile strength, the flexural modulus, and impact strength of iPP composites increased 9.7, 38.6, and 42.9%, respectively. The result indicated good synergistic effects of NC, NA11, and PP‐g‐MA in improving iPP mechanical properties. WAXD patterns revealed NA11, and NC only induced the α‐crystals of iPP. SEM micrograph showed that the PP‐g‐MA could effectively improve the dispersing of NC in iPP. Finally, the nonisothermal crystallization kinetics of neat iPP and PP nanocomposites was described by Caze method. The result indicated that the addition of NA overcame the shortcoming of low crystallization rate of NC nanocomposites and maintained the excellent mechanical properties, which is another highlight of the combined addition of NAs and nanoclay. Meanwhile, the result showed that nuclei formation and spherulite growth of iPP were affected by the presence of NA and nanoclay. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011