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     

Melting behavior,nonisothermal crystallization kinetics,and morphology of PP/nylon 11/EPDM‐g‐MAH blends

The melting behavior, nonisothermal crystallization behavior, and morphology of pure polypropylene (PP) and its blends were investigated by differential scanning calorimetry and polarized optical microscopy. The nonisothermal crystallization kinetics was analyzed using the Avrami equation modified by Jeziorny and the equation combining the Avrami and Ozawa method. The surface fold free energy and the effective activation energy for both PP and its blends were obtained by Hoffman‐Lauritzen theory and Vyazovkin's approach, respectively. The results showed that the presence of nylon 11 hindered the mobility of PP chains but accelerated the overall crystallization rate. The POM observation confirmed that the addition of nylon 11 decreased the spherulites size of PP matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

PTT非等温结晶动力学研究

采用差示扫描量热仪对PTT进行非等温结晶研究。利用不同动力学模型对其结晶过程进行处理, 并将PTT与PET及PBT的非等温结晶过程进行对比。结果表明:Jeziorny方程和Ozawa方程都可以很好的 描述PTT,PET,PBT的非等温结晶过程;采用结合Avrami方程和Ozawa方程的处理方法,得到了3种聚酯的 结晶速率的大小关系:PBT>PTT>PET。通过计算Ziabicki结晶能力参数,得到3种聚酯的结晶能力的顺序 为:PBT>PTT>PET。     

Isothermal and nonisothermal crystallization kinetics of nylon-11

Analysis of the isothermal, and nonisothermal crystallization kinetics of Nylon-11 is carried out using differential scanning calorimetry. The Avrami equation and that modified by Jeziorny can describe the primary stage of isothermal and nonisothermal crystallization of Nylon-11. In the isothermal crystallization process, the mechanism of spherulitic nucleation and growth are discussed; the lateral and folding surface free energies determined from the Lauritzen–Hoffman equation are ς = 10.68 erg/cm² and ς_e = 110.62 erg/cm²; and the work of chain folding q = 7.61 Kcal/mol. In the nonisothermal crystallization process, Ozawa analysis failed to describe the crystallization behavior of Nylon-11. Combining the Avrami and Ozawa equations, we obtain a new and convenient method to analyze the nonisothermal crystallization kinetics of Nylon-11; in the meantime, the activation energies are determined to be −394.56 and 328.37 KJ/mol in isothermal and nonisothermal crystallization process from the Arrhonius form and the Kissinger method. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2371–2380, 1998     

Morphology,nonisothermal crystallization behavior,and kinetics of poly(phenylene sulfide)/polycarbonate blend

The morphology and nonisothermal crystallization behavior of blends made of poly(phenylene sulfide) (PPS), with a amorphous polycarbonate (PC) were studied. The blend is found to be partially miscible by the dynamic mechanical thermal analysis (DMTA) and melt rheological measurements. The nonisothermal crystallization behavior of blend was studied by differential scanning calorimetry (DSC). The results show clearly that the crystallization temperatures of PPS component in the blend decrease with increasing of PC contents. The crystallization kinetics was then analyzed by Avrami, Jeziorny, and Ozawa methods. It can be concluded that the addition of PC decreases the PPS overall crystallization rate because of the higher viscosity of PC and/or partial miscibility of blend, despite of small heterogeneous nucleation effect by the PC phase and/or phase interface. The results of the activation energy obtained by Kissinger method further confirm that the amorphous PC in the partial miscible PPS/PC blend may act as a crystallization inhibitor of PPS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Quiescent crystallization kinetics and morphology of i‐PP resins for injection molding. II. Nonisothermal crystallization as a function of molecular weight

The quiescent nonisothermal crystallization kinetics of polypropylene resins was studied as a function of their molecular weight, M_w. Differential scanning calorimetry and polarized light optical microscopy were used to follow this kinetics. It was observed that a modified Hoffman and Lauritzen equation could describe with accuracy their nonisothermal behavior. Also it was found that the polypropylene nonisothermal growth rates, G_n, were similar to their corresponding isothermal rates, G, and also decreased with the increase in M_w. The use of a prior isothermal nucleation procedure allowed to obtain data at higher temperatures and to compare these data at higher cooling rates than the ones found in the literature. The morphology of all the samples revealed a fine and radial spherulitic texture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1733–1740, 1999     

Synthesis and nonisothermal crystallization kinetics of thermoplastic polyamide-6 elastomers

Three kinds of thermoplastic polyamide-6 elastomers (TPAEs) with varying polytetramethyleneglycol (PTMG) contents of 10, 20, and 30 wt % were prepared via a one-pot polymerization synthetic route and named as TPAE1, TPAE2, and TPAE3, respectively. First, their structures were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, scanning electron microscope, and X-ray diffraction. The obtained results confirmed that targeted TPAEs were successfully synthesized and the unit cell of crystallization in TPAEs with α form was confirmed. Subsequently, the thermal properties of prepared TPAEs were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements, respectively. DSC curves showed that melting points of synthesized TPAEs were in the range of 209.2–215.9 °C. Moreover, TGA results showed TPAEs possess good thermal stability and cannot be decomposed under 300 °C. Additionally, the modified Avrami's equation, Ozawa's theory, and Mo's method were employed to investigate the nonisothermal crystallization kinetics of prepared TPAEs. It is found that the Mo's method exhibited great advantages in treating the nonisothermal crystallization kinetics of prepared TPAEs. Meanwhile, the crystallization kinetics and halftime are influenced by the contents of PTMG and follows a nonlinear fashion in agreement with the trend inactivation energies calculated by the Kissinger method. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47388.     

Melting behavior and nonisothermal crystallization kinetics of polyamide 6/polyamide 66 molecular composites via in situ polymerization

The melting behavior and nonisothermal crystallization kinetics of pure polyamide 6 (PA 6) and its molecular composites with polyamide 66 (PA 66) were investigated with differential scanning calorimetry. The PA 6/PA 66 composites had one melting peak, whereas the coextruded PA 6/PA 66 blends had two melting peaks. With the addition of PA 66 to PA 6 via in situ anionic polymerization, the melting temperature, crystallization temperature, and crystallinity of PA 6 in the composites decreased. The half‐time of nonisothermal crystallization increased for a PA 6/PA 66 molecular composite containing 12 wt % PA 66, in comparison with that of pure PA 6. The commonly used Ozawa equation was used to fit the nonisothermal crystallization of pure PA 6 and its composites. The Ozawa exponent values in the primary stage were equal to 1.28–3.03 and 1.28–2.97 for PA 6 and its composite with 12 wt % PA 66, respectively, and this revealed that the mechanism of primary crystallization of PA 6 and PA 6/PA 66 was mainly heterogeneous nucleation and growth. All the results indicated that the incorporation of PA 66 into PA 6 at the molecular level retarded the crystallization of PA 6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2172–2177, 2005     

PET/TiO2复合材料非等温结晶行为的研究

采用表面接枝和聚合改性的方法,分别以γ-缩水甘油醚氧丙基三甲基硅烷(GPS)和甲基丙烯酸甲酯(MMA)对纳米二氧化钛(TiO_2)进行表面修饰,通过熔融共混制得聚对苯二甲酸乙二醇酯(PET)/GPS- TiO_2和PET/聚甲基丙烯酸甲酯(PMMA)-TiO_2纳米复合材料,用差示扫描量热法研究了其复合材料的非等温结晶行为,利用不同动力学模型对其结晶过程进行处理。结果表明：未处理的纳米TiO_2提高了PET的熔融温度和结晶温度;而经表面接枝的GPS-TiO_2和PMMA-TiO_2对PET的熔融温度和结晶温度的影响并不显著;不同表面特性的纳米TiO_2降低了PET的结晶度,但经表面接枝后的纳米TiO_2其影响程度减弱;用Jezi- omy法和莫志深法处理PET/TiO_2纳米复合材料的非等温结晶过程比较理想,PET,PET/PMMA-TiO_2,PET/ TiO_2,PET/GPS-TiO_2复合材料的结晶速率依次减小。     

Effects of UV‐irradiation on the nonisothermal crystallization kinetics of polypropylene

The influences of UV‐induced photodegradation on the nonisothermal crystallization kinetics of polypropylene (PP) were investigated by differential scanning calorimetry. The Avrami analysis modified by Jeziorny, Ozawa method, and a method modified by Liu were employed to describe the nonisothermal crystallization process of unexposed and photodegraded PP samples. Kinetics studies reveal that the rates of nucleation and growth may be affected differently by photodegradation. A short‐term UV‐irradiation may accelerate the overall nonisothermal crystallization process of PP, but a long‐term UV‐irradiation should impede it. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Novel observations on kinetics of nonisothermal crystallization in fly ash filled isotactic‐polypropylene composites

A study on nonisothermal crystallization kinetics in fly ash (FA) filled isotactic‐polypropylene (PP) composites has revealed some interesting phenomena. Composites made by injection moulding of PP with 0, 20, 45, and 60 wt % of FA were nonisothermally studied using differential scanning calorimetry at cooling rates 10°C, 15°C, and 20°C per min from a melt temperature of 200°C cooled to ?30 °C. Whilst neat PP showed a mono modal α crystalline phase‐ only structure, presence of FA led to bimodal thermographs revealing partial transcrystallisation of α into β, to maximum 14%. The onset and peak crystallization temperatures of all samples decreased by ～ 3°C with each 5°C/min increase in cooling rate. Parameters such as crystal growth rate, dimensions, and activation energy were determined using a series of established models. The Avrami graphs showed that contrary to the published data, there are two sets of straight lines (a) with a lower slope at low cooling rate and (b) with a distinctly higher slope for high cooling rate. Activation energy of the materials reached a maximum at 45% FA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on the phase structure,mechanical, rheological properties,and nonisothermal crystallization kinetics of the PEN/SCF composites

Short carbon fiber reinforced poly(ethylene 2,6‐naphthalate) composites (PEN/SCF) were prepared by twin‐screw extruder. The structure, mechanical, rheological properties, and nonisothermal crystallization kinetics of the composites were investigated by scanning electron microscope, universal tester, and differential scanning calorimetry. The results suggest that there is better interaction between SCF and PEN matrix, which leads to an increase in the tensile strength, Young's modulus, and impact strength of the composites with proper contents of SCF. Rheological behavior of the PEN/SCF composites melt is complicated, combining a dilate fluid at lower shear rate and a pseudoplastic fluid at higher shear rate. Moreover, the flow activation energy of the composites suggests that the melt with more SCF has higher sensitivity to the processing temperature. In conclusion, the composite with 5–10 wt % content of SCF has better properties. The Avrami equation modified by Jeziorny and Ozawa theory was used, respectively, to fit the primary stage of nonisothermal crystallization of various composites. The Avrami exponents n are evaluated to be 2.6–3.1 for the neat PEN and 3.4–4.8 for PEN/SCF composites, and the SCF served as nucleation agent accelerates the crystallization rate of the composites, and more the content of SCF faster the crystallization rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Isothermal and nonisothermal melt‐crystallization kinetics of syndiotactic polystyrene

Analyses of the isothermal and nonisothermal melt kinetics for syndiotactic polystyrene have been performed with differential scanning calorimetry, and several kinetic analyses have been used to describe the crystallization process. The regime II→III transition, at a crystallization temperature of 239°, is found. The values of the nucleation parameter K_g for regimes II and III are estimated. The lateral‐surface free energy, σ = 3.24 erg cm^?2, the fold‐surface free energy, σ_e = 52.3 ± 4.2 erg cm^?2, and the average work of chain folding, q = 4.49 ± 0.38 kcal/mol, are determined with the (040) plane assumed to be the growth plane. The observed crystallization characteristics of syndiotactic polystyrene are compared with those of isotactic polystyrene. The activation energies of isothermal and nonisothermal melt crystallization are determined to be ΔE = ?830.7 kJ/mol and ΔE = ?315.9 kJ/mol, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2528–2538, 2002     

Synthesis and nonisothermal crystallization kinetics of biodegradable poly(ethylene terephthalate-co-ethylene succinate)s

In the current work, a series of biodegradable poly(ethylene terephthalate-co-ethylene succinate)s (P[ET-co-ES]s) were prepared via a traditional melting polycondensation method. First of all, the structures of prepared copolymers were characterized by nuclear magnetic resonance and Fourier transform infrared measurements. Meanwhile, the thermal properties of prepared samples were analyzed by differential scanning calorimetry and thermogravimetric analysis measurements, respectively. Subsequently, the mechanical properties of the P(ET-co-ES)s were evaluated, the tensile strength of P(ET-co-ES)s decreased with increasing of PES content in copolymer, however, corresponding P(ET-co-ES)s exhibited better elongation at break. Next, the biodegradability of P(ET-co-ES)s was evaluated using lipase as degrading enzyme. The results presented that the biodegradability of P(ET-co-ES)s improved with PES content, the corresponding results were supported by scanning electron microscopy test. Finally, the Mo's modified Avrami equation was employed to analyze the nonisothermal crystallization kinetics of prepared copolymers. The results showed the addition of the PES component improved the crystallization properties of the prepared P(ET-co-ES)s. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48422.     

Melting behaviors,isothermal crystallization kinetics,and morphology of poly(trimethylene terephthalate)/stainless steel fiber composites

The melting behavior and crystallization kinetics of poly(trimethylene terephthalate) (PTT)/stainless steel fiber (SSF) composites were investigated with differential scanning calorimetry. The morphology was studied with scanning electron microscopy and polarized optical microscopy. Differential scanning calorimetry analysis revealed that the crystallization temperature increased by 27°C with the addition of 1 vol % SSF to the matrix. The Avrami exponents, analyzed in isothermal crystallization kinetics, were determined to be 2–3 for both neat PTT and PTT/SSF composites. SSF, as a nucleating agent in the composites, greatly increased the crystallization rate. The activation energies of the composites were obviously lower than that of pure PTT, and this indicated much easier crystallization of the composites. All these samples exhibited banded spherulites, and the spherulite size gradually decreased with the SSF loading increasing. Subsequent melting behaviors revealed that all of these samples, especially of the composites, exhibited triple melting peaks at all crystallization temperatures studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of processing on morphology in short aramid fiber reinforced elastomer compounds

The rubber industry is nowadays facing the general increase of raw materials as the customers are confronted with rising prices for energy. Therefore there is a need for higher durability of elastomer applications. Short fiber reinforced elastomers can contribute to the improvement of dynamic and wear properties. To determine structure–property relationships in short fiber reinforced elastomer compounds it is of crucial interest to know the contributions of fiber aspect ratio, volume content, orientation and fiber–elastomer interaction. Therefore the influence of different processing conditions and fiber contents on the resulting morphology and macroscopic properties was investigated in this article by the help of fluorescence and confocal laser microscopy using a transparent ethylene‐propylene‐diene rubber (EPDM) matrix. It was found that the processing induced fiber breakage was the key factor in determining the composite morphology and subsequent physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1682–1690, 2013     

Effects of filler type on the nonisothermal crystallization kinetics of poly(butylene terephthalate) (PBT) composites

In this study, melt‐crystallization behaviors of poly(butylene terephthalate) (PBT) composites including different types of inorganic fillers were investigated. Composite samples having 5 wt % of fillers were prepared by melt processing in a twin screw extruder using commercial grades of calcite (CA), halloysite (HL), and organo‐montmorillonite (OM) as filler. Depending on the filler type and geometry, crystallization kinetics of the samples was studied by differential scanning calorimetry (DSC) methods. Effect of filler type on the nonisothermal melt‐crystallization kinetics of the PBT was analyzed with various kinetic models, namely, the Ozawa, Avrami modified by Jeziorny and Liu‐Mo. Crystallization activation energies of the samples were also determined by the Kissinger, Takhor, and Augis–Bennett models. From the kinetics study, it was found that the melt‐crystallization rates of the samples including CA and HL‐nanotube were higher than PBT at a given cooling rate. On the other hand, it was also found that organo‐montmorillonite reduced the melt‐crystallization rate of PBT. It can be concluded that organic ammonium groups in the OM decelerate the crystallization rate of PBT chains possibly due to affecting the chain diffusion through growing crystal face and folding. This study shows that introducing organically modified alumina‐silicate layers into the PBT‐based composites could significantly reduce the production rate of the injection molded parts during the processing operations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isothermal and nonisothermal crystallization of HDPE composites containing multilayer carton scraps as filler

The influence of multilayer carton scraps (MC) on crystallization kinetics of high-density polyethylene (HDPE) is detailed in this contribution. HDPE/MC composites were prepared by melt mixing, and a maleated linear low density polyethylene (MAPE) was added as compatibilizer. The crystallization kinetics of HDPE/MC/MAPE was analyzed as function of composition both in isothermal and nonisothermal conditions. The multilayer carton scraps appear to promote the onset of crystallization of HDPE, acting as efficient nucleating agent. The presence of MAPE as compatibilizer slightly reduces the nucleating efficiency of MC: the compatibilizer induces a delay in the onset of crystallization, caused by the need to exclude the bulky pendant groups of maleated linear low-density polyethylene from the crystals, as HDPE and MAPE chains cocrystallize. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PEN非等温冷结晶动力学的研究

采用差示扫描量热(DSC)法对聚萘二甲酸乙二醇酯(PEN)的非等温冷结晶动力学进行研究;通过改变升温速率,讨论了PEN冷结晶起始温度与峰顶温度之间存在差值的原因;对比了两种不同的冷结晶起始点的确定方法对冷结晶动力学常数的影响。结果表明:以DSC曲线偏离基线作为PEN冷结晶的起始点,得到的表观Avrami指数很大;用基线延长线与DSC曲线的切线的交点作为冷结晶的起始点和结束点,得到的表观Avrami指数为2.55,且不随升温速率的变化而变化,与等温熔融热结晶方法得到的结果接近,具有相似的结晶生长方式。