Poly(propylene)–poly(propylene)‐grafted maleic anhydride–organic montmorillonite (PP–PP‐g‐MAH–Org‐MMT) nanocomposites. II. Nonisothermal crystallization kinetics

The nonisothermal crystallization kinetics of poly(propylene) (PP), PP–organic‐montmorillonite (Org‐MMT) composite, and PP–PP‐grafted maleic anhydride (PP‐g‐MAH)–Org‐MMT nanocomposites were investigated by differential scanning calorimetry (DSC) at various cooling rates. Avrami analysis modified by Jeziorny and a method developed by Mo well‐described the nonisothermal crystallization process of these samples. The difference in the exponent n between PP and composite (either PP–Org‐MMT or PP–PP‐g‐MAH–Org‐MMT) indicated that nonisothermal kinetic crystallization corresponded to tridimensional growth with heterogeneous nucleation. The values of half‐time, Z_c; and F(T) showed that the crystallization rate increased with the increasing of cooling rates for PP and composites, but the crystallization rate of composites was faster than that of PP at a given cooling rate. The method developed by Ozawa can also be applied to describe the nonisothermal crystallization process of PP, but did not describe that of composites. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The results showed that the activation energy of PP–Org‐MMT was much greater than that of PP, but the activation energy of PP–PP‐g‐MAH–Org‐MMT was close to that of pure PP. Overall, the results indicate that the addition of Org‐MMT and PP‐g‐MAH may accelerate the overall nonisothermal crystallization process of PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3093–3099, 2003     

Morphology,Crystallization and Dynamical Mechanical Behavior of iPP/Nano-CaCO3 Composites

This article describes our study of crystallization behavior of nano-CaCO₃-filled polypropylene under nonisothermal from the melt by differential scanning calorimetry (DSC). Morphology observation indicated with increasing CaCO₃ content the aggregates increased. Nano-CaCO₃ acted as nucleating site during nonisothermal crystallization in all iPP/nano-CaCO₃ composites. For nonisothermal crystallization kinetic studies, the result indicated that the Jeziorny and Ozawa approach cannot adequately describe the nonisothermal crystallization kinetic of iPP composite. In addition, Mo equation was employed to describe the nonisothermal crystallization kinetic process with satisfied results. Dynamic mechanical analysis indicated with increasing CaCO₃ content the glass transition decreased slightly.     

Effective method for dispersing SiO2 nanoparticles into polyethylene

The nonisothermal crystallization behavior and kinetics of polytetrafluoroethylene (PTFE) and PTFE/solid glass microsphere (SGM) composites were investigated with differential scanning calorimetry at various cooling rates (?'s). Three methods, namely, the Jeziorny, Ozawa and Mo methods, were used to describe the nonisothermal crystallization process. The results show that the peak temperature, crystallinity (X_c), and crystallization half‐time were strongly dependent on the content of SGMs and ?. The SGMs in the PTFE/SGM composites exhibited a higher nucleation activity. The nonisothermal crystallization kinetics of PTFE and the PTFE/SGM composites was analyzed successfully with the Jeziorny and Mo methods; however, the Ozawa equation was invalid for the nonisothermal crystallization process. The crystallization activation energy determined with the Kissinger equation was remarkably lower when a small amount of SGMs (5%) was added and then gradually increased and finally became slightly lower than that of pure PTFE as the content of SGMs increased up to 25% in the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nonisothermal crystallization kinetics of kenaf fiber/polypropylene composites

Nonisothermal crystallization behavior of model ecocomposites based on polypropylene (PP), maleic anhydride modified polypropylene (PP_m), and kenaf fibers were extensively studied. Melting and crystallization behavior of the composites with 20 wt/wt% kenaf fibers were analyzed by differential scanning calorimetry (DSC) in dynamic regime (with heating rate of 10 K/min, and cooling rates of 5, 10, 15, 20, and 40 K/min). It was shown that the kenaf fiber surface acts as a nucleating agent during nonisothermal crystallization of both PP matrices, shifting the onset and peak crystallization temperatures toward higher values. Crystallization behavior was analyzed by Avrami, Jeziorny, Ozawa, Mo, and Kissinger methods. The results confirmed the applicability of the used models, with exception of the Ozawa approach that was rather inapplicable for these composites. POLYM. ENG. SCI., 47:745–749, 2007. © 2007 Society of Plastics Engineers.     

聚酰胺612的非等温结晶动力学研究

采用差示扫描量热仪研究了聚酞胺612在不同降温速率下的非等温结晶行为,并用Jeziorny法、Ozawa法和莫志深法对DSC测试数据进行了处理。结果表明,随降温速率的增加,其结晶峰从高温向低温方向移动,峰形变宽,结晶时间缩短,结晶加快。聚酚胺612的非等温结晶动力学能较好地符合莫志深法和Jeziomy法。采用Kissinger方程计算出聚酞胺612的非等温结晶活化能为293.0U/mol。     

铸型PA 6/TiO2纳米复合材料的非等温结晶行为

采用差示扫描量热法(DSC)研究了铸型聚酰胺(PA)6/TiO2纳米复合材料在不同冷却速率下的非等温结晶行为,并用Jeziomy法、Ozawa法和Mo法对DSC测定结果进行了处理。结果表明：纳米TiO2对铸型PA6起到异相成核的作用,提高了铸型PA6的结晶速率和结晶峰温,缩短了半结晶时间。3种方法对比后发现：Ozawa法不适用于铸型PA6及其纳米复合材料非等温结晶动力学的处理,Jeziomy法基本适合,而Mo法最适合。采用Kissinger法计算出铸型PA6及其TiO2纳米复合材料的结晶活化能,发现纳米粒子提高了铸型PA6的结晶活化能．说明纳米TiO2阻碍了铸型PA6的分子链在结晶时的运动。     

Non-isothermal crystallization kinetics of polypropylene/MAP-POSS nanocomposites

Non-isothermal crystallization kinetics of polypropylene (PP)/methylacryloypropy polyhedral oligomeric silsesquioxanes (MAP-POSS) nanocomposites (PP/MAP-POSS) were investigated by DSC at various cooling rates. Jeziorny and Mo method were used to study the non-isothermal crystallization kinetics. The results show that the Jeziorny and Mo method are all successful in describing the non-isothermal crystallization kinetics of PP/MAP-POSS nanocomposites. The MAP-POSS can act a role of heterogeneous nucleation and increase the crystallization rate constant Z _c and decrease crystallization half time t _1/2, and the spherulite crystal size decreases, the inter-spherulitic action or crosslinking structure each other appear at the appropriate content. The DSC peak temperature T _p increase about 5 °C, t _1/2 reduce 0.21 min at 6 % content of MAP-POSS and heating rate of 10 °C/min. The MAP-POSS can also increase the mechanical property of PP/MAP-POSS nanocomposites, the tensile strength and impact strength increase from 12.97 to 19.93 MPa and from 33.2 to 52.6 kJ/m², respectively, at 4 % content of MAP-POSS. But the spherulitic crystal becomes larger and boundaries become clearer again; the macrophase separation will occur and mechanical properties decrease when more and more MAP-POSS was added. The nanocomposite has the best mechanical property at 4 % content of MAP-POSS.     

Effect of Nanoparticle Surface Treatment on Nonisothermal Crystallization Behavior of Polypropylene/Calcium Carbonate Nanocomposites

Polypropylene (PP)/CaCO₃ nanocomposites were prepared by melt-blending method using a Haake-90 mixer. The CaCO₃ nanoparticles were surface modified with a coupling agent before compounding. A fine dispersion of the modified nanoparticles in the nanocomposites was observed by transmission electron microscopy (TEM). Effects of surface treatment of CaCO₃ nanoparticles on the nonisothermal crystallization behavior and kinetics of PP/CaCO₃ nanocomposites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo methods were used to describe the nonisothermal crystallization process. It was shown that the crystallization temperature of the nanocomposites increased due to the heterogeneous nucleation of the surface-treated nanoparticles. It was found that the nanoparticles modified with a proper content range of coupling agent could facilitate the nonisothermal crystallization of the nanocomposites under certain conditions (the cooling rate and the relative degree of crystallinity). This may be a potential application for the crystallization controlling of composites in manufacturing. In addition, the activation energy of crystallization for the nanocomposites and the nucleation activity of the nanoparticle were estimated by using Kissinger and Dobreva's methods, respectively. It could be concluded that the surface-treated nanoparticles had a strong nucleating activity, which caused the decrease of the activation energy of the nanocomposites.     

Nonisothermal Crystallization Kinetics of Polypropylene/Polyethersulfone Blend

The nonisothermal crystallization kinetics of PP and PP/PES (80/20 wt%) blend was investigated by using differential scanning calorimetry (DSC). It was observed that the crystallization peak temperature (T_p) and the half time (t _1/2) of crystallization of PP/PES blend are slightly but consistently lower than those of PP at various cooling rates. The nonisothermal crystallization data were analyzed by using Avrami equation, Ozawa and Mo method. The validity of the different kinetics models to the nonisothermal crystallization process of two samples is discussed. The Mo method can successfully explain the overall nonisothermal crystallization process of PP and PP/PES blend. The activation energy (ΔE) for nonisothermal crystallization of PP and PP/PES blend is determined by using the Kissinger method. The result shows that the ΔE value of PP is slightly higher than that of PP/PES blend.     

Non-isothermal crystallization kinetics of poly(ethylene terephthalate)/mica composites

The non-isothermal crystallization kinetics of pure poly(ethylene terephthalate) (PET), PET/mica and PET/TiO₂-coated mica composites were investigated by differential scanning calorimetry with different theoretical models, including the modified Avrami method, Ozawa method and Mo method. The activation energies of non-isothermal crystallization were calculated by Kissinger method and Flynn–Wall–Ozawa method. The results show that the modified Avrami equation and Ozawa theory fail to describe the non-isothermal crystallization behavior of all composites, while the Mo model fits the experiment data fair well. It is also found that the mica and TiO₂-coated mica could act as heterogeneous nucleating agent and accelerate the crystallization rates of PET, and the effect of TiO₂-coated mica is stronger than that of mica. The result is further reinforced by calculating the effective activation energy of the non-isothermal crystallization process for all composites using the Kissinger method and the Flynn–Wall–Ozawa method.     

PP/PP-g-NH2/纳米SiO2复合材料的非等温结晶

采用示差扫描量热法（DSC）研究了聚丙烯/氨基化聚丙烯/纳米二氧化硅（PP/PP-g-NH₂/SiO₂）复合材料的非等温结晶行为。利用Caze法对结晶动力学进行了分析,Avrami指数n表明纳米SiO₂和PP-g-NH₂的加入改变了PP的结晶成核和生长机理;运用Dobreva法研究了纳米粒子的成核活性,结果表明纳米SiO₂成核活性差,增容剂PP-g-NH₂明显增强其成核活性;采用Friedman法分析了复合材料的结晶有效能垒,研究表明加入纳米SiO₂使PP的结晶有效能垒降低,添加PP-g-NH₂则进一步降低复合体系的结晶有效能垒;当纳米粒子含量为3%时,添加5% PP-g-NH₂能有效提高纳米粒子成核活性,降低复合材料结晶有效能垒。     

Crystal morphology and nonisothermal crystallization kinetics of short carbon fiber/poly(trimethylene terephthalate) composites

The crystal morphology and nonisothermal crystallization kinetics of short carbon fiber/poly(trimethylene terephthalate) (SCF/PTT) composites were investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The optical micrographs suggest that the more content of SCF in composites, the smaller size of the spherulites is. Moreover, the addition of SCF can lead to forming banded spherulites in composites. The Avrami equation modified by Jeziorny, Ozawa theory and the method developed by Mo were used, respectively, to fit the primary stage of nonisothermal crystallization of various composites. The results suggest that the SCF served as nucleation agent, accelerates the crystallization rate of the composites, and the more content of SCF, the faster crystallization rate is. Effective activation energy calculated by the differential iso‐conversional method developed by Friedman also concludes that the composite with more SCF component has higher crystallization ability than that with less SCF content. The kinetic parameters U* and K_g are determined, respectively, by the Hoffman–Lauritzen theory. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

HGB的表面改性对PP／HGB复合材料力学性能和结晶性能的影响

采用KH550硅烷偶联剂和硝酸钕分别对空心玻璃微珠进行表面改性;熔融共混挤出法制备PP／HGB复合材料;研究复合材料的力学性能,并采用差示扫描量热法研究PP／HGB复合材料的非等温结晶过程。利用Jeziorny方程对PP和PP／HGB复合材料进行非等温结晶动力学的研究。结果表明：未经表面改性的HGB与PP的界面结合力差,复合材料的综合力学性能较差。HGB经过KH550和硝酸钕表面改性后,提高了与PP的界面黏结力,复合材料的力学性能得以提高,并且经过KH550和硝酸钕表面改性的HGB可以小幅提高复合材料的结晶度,但降低PP的结晶速率。     

Effects of nanosilica filler surface modification and compatibilization on the mechanical,thermal and microstructure of PP/EPR blends

Polypropylene/ethylene-propylene rubber/nanosilica (PP/EPR/nano-SiO₂) composites were prepared by a melt blending masterbatch process using a Brabender mixer. In order to improve the interfacial adhesion and achieve diverse desired properties of the composites, nanosilica surface silylation by means of two silane coupling agents: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (AEAPTMS) and 3-methacryloxypropyltrimethoxysilane (MPTMS) was explored. The composites were also compatibilized using three compatibilizers: methyl methacrylate grafted PP (MMA-g-PP), glycidylmethacrylate grafted PP (GMA-g-PP) and maleic anhydride grafted PP (MAH-g-PP). The properties of the blends and the composites were examined using tensile and Izod impact tests, differential scanning calorimetry (DSC), thermogravimetric analysis (ATG) and scanning electron microscopy (SEM). According to the mechanical property evaluations, the incorporation of nano-SiO₂ particles into PP/EPR blend improved the tensile strength and Young’s modulus of the composites. The elongation and Izod impact strength were adversely affected. A significant improvement in the mechanical properties was obtained for the composites with AEAPTMS-SiO₂ and MAH-g-PP. The DSC results indicated that the incorporation of the modified silica and MAH-g-PP increased the crystallinity of the composites. However, no significant variation in the crystallinity was observed as a result of the addition of MMA-g-PP and GMA-g-PP. The TGA results revealed that the composites exhibit a higher thermal stability than that of the neat matrix. SEM micrographs of the fractured surfaces revealed a two-phase morphology with EPR nodules being dispersed in the PP matrix. SEM also indicated that the incorporation of MAH-g-PP into PP/EPR composites contributes to a better dispersion of the EPR phase and nano-SiO₂ particles in the polymer matrix.     

Nonisothermal crystallization of PP/nano‐SiO2 composites

The kinetics of nonisothermal crystallization of polypropylene (PP) containing nanoparticles of silicon dioxide (SiO₂) were investigated by differential scanning calorimetry (DSC) at various cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that the Ozawa equation and Mo's treatment could describe the nonisothermal crystallization of the composites very well. The nano‐SiO₂ particles have a remarkable heterogeneous nucleation effect in the PP matrix. The rate of crystallization of PP/nano‐SiO₂ is higher than that of pure PP. By using a method proposed by Kissinger, activation energies have been evaluated to be 262.1, 226.5, 249.5, and 250.1 kJ/mol for nonisothermal crystallization of pure PP and PP/nano‐SiO₂ composites with various SiO₂ loadings of 1, 3, and 5%, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1013–1019, 2004     

Non-isothermal crystallization kinetics of poly (lactic acid)/modified carbon black composite

A novel method was employed to modify the surface of carbon black (CB) by an organic small molecule in a Haake Rheomix mixer. Jeziorny equation, the Ozawa model and Mo equation were employed to describe the non-isothermal crystallization process of poly (lactic acid) (PLA), PLA/CB and PLA/modified carbon black (MCB) composites. It is found that the Ozawa model fail to describe the non-isothermal crystallization process for PLA and its composites, while Jeziorny equation and Mo’s theory provide a good fitting. The comparison of crystallization kinetics between PLA/MCB and PLA through Lauritzen–Hoffman model indicates that there appears a transition from regimes II to III in PLA and PLA/MCB. The fold surface free energy σ _e of PLA/MCB composite is higher than that of neat PLA, implying that the existence of nucleating agent is unfavorable for the regular folding of the molecule chain.     

POM /TPU共混物非等温结晶动力学研究

采用差示扫描量热法(DSC}研究了不同冷却速率下聚甲醛( POM)以及POM/热塑性聚氨酷弹性体(TPU)共混物的非等温结晶过程,分别采用Jeziorny法、Ozawa法和Mo法进行处理。结果表明:随着冷却速率的增大,POM及其共混物的结晶峰都变宽,结晶峰值温度(Tc)都降低;在相同冷却速率下,POM /TPU共混物的Tc。较纯POM有所提高;Jeziorny法和Mo法处理非等温结晶过程比较理想,而由于次级结晶的存在Ozawa法并不适用;Jeziorny法和Mo法处理所得的数据表明,TPU的加人能够提高POM的结晶速率,减小半结晶时间(t1/2),并且导致POM的结晶成核和生长发生了改变。     

Nonisothermal crystallization behavior of highly exfoliated polypropylene/clay nanocomposites prepared by in situ polymerization

Polypropylene/clay nanocomposites (PPCNs) were prepared via an in situ polymerization method with a Ziegler–Natta/clay compound catalyst in which the MgCl₂/TiCl₄ catalyst was embedded in the clay galleries. The wide‐angle X‐ray diffraction and transmission electron microscopy results showed that the clay particles were highly exfoliated in the polypropylene (PP) matrix. The nonisothermal crystallization kinetics of these PPCNs were investigated by differential scanning calorimetry at various cooling rates. The nucleation activity were calculated by Dobreva's method to demonstrate that the highly dispersed silicate layers acted as effective nucleating agents. The Avrami, Jeziorny, Ozawa, and Mo methods were used to describe the nonisothermal crystallization behavior of the PP and PPCNs. Various parameters of nonisothermal crystallization, such as the crystallization half‐time, crystallization rate constant, and the kinetic parameter F(t), reflected that the highly exfoliated silicate layers significantly accelerated the crystallization process because of its outstanding nucleation effect. The activation energy values of the PP and PPCNs determined by the Kissinger method increased with the addition of the nanosilicate layers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PET/滑石粉复合材料结晶性能、热性能和力学性能研究

采用差示扫描量热仪、热重分析仪等研究了滑石粉作为成核剂对聚对苯二甲酸乙二醇酯（PET）结晶性能、热性能以及力学性能的影响。结果表明,滑石粉的添加量为0.5 %（质量分数,下同）时,可有效改善PET的结晶性能,结晶温度（Tc）比经历相同热历程的PET空白试样提高11.36 ℃,且结晶完善程度随降温速率的减小而提高;非等温结晶动力学研究发现,Jeziorny法和莫志深法更符合复合材料的非等温结晶过程,而二次结晶的存在使Ozawa法并不适用;由于滑石粉与基体树脂相容性好并可均匀分散,从而很好地保持了原树脂的热性能,且所得复合材料的力学性能均有所提高,其中拉伸性能提高12 %。