Nonisothermal crystallization kinetics of polypropylene/polypropylene‐g‐polystyrene/polystyrene blends

The nonisothermal crystallization kinetics of polypropylene (PP), PP/polystyrene (PS), and PP/PP‐g‐PS/PS blends were investigated with differential scanning calorimetry at different cooling rates. The Jeziorny modified Avrami equation, Ozawa method, and Mo method were used to describe the crystallization kinetics for all of the samples. The kinetics parameters, including the half‐time of crystallization, the peak crystallization temperature, the Avrami exponent, the kinetic crystallization rate constant, the crystallization activation energy, and the F(T) and a parameters were determined. All of the results clearly indicate that the PP‐g‐PS copolymer accelerated the crystallization rate of the PP component in the PP/PP‐g‐PS/PS blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization behavior of carbon black‐filled polypropylene and polypropylene/epoxy composites

The crystallization behavior of polypropylene (PP)/carbon black (CB) and PP/epoxy/CB composites was studied with differential scanning calorimetry (DSC). The effects of compatibilizer MAH‐g‐PP and dynamic cure on the crystallization behavior are investigated. The nonisothermal crystallization parameters analysis showed that CB particles in the PP/CB composites and the dispersed epoxy particles in the PP/epoxy composites could act as nucleating agents, accelerating the crystallization of the composites. Morphological studies indicated that the incorporation of CB into PP/epoxy resulted in its preferential localization in the epoxy resin phase, changing the spherical epoxy particles into elongated structure, and thus reduced the nucleation effect of epoxy particles. Addition of MAH‐g‐PP significantly decreased the average diameter of epoxy particles in the PP/epoxy and PP/epoxy/CB composites, promoting the crystallization of PP more effectively. The isothermal crystallization kinetics and thermodynamics of the PP/CB and PP/epoxy/CB composites were studied with the Avrami equation and Hoffman theory, respectively. The Avrami exponent and the crystallization rate of the PP/CB composites were higher than those of PP, and the free energy of chain folding for PP crystallization decreased with increasing CB content. Addition of MAH‐g‐PP into the PP/epoxy and PP/epoxy/CB composites increased the crystallization rate of the composites and decreased the chain folding energy significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 104–118, 2006     

Crystallization kinetics of polypropylene composites filled with nano calcium carbonate modified with maleic anhydride

The subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano‐CaCO₃) composites. In this study, 5 wt % nano‐CaCO₃ modified with different contents of MAH was filled into a PP matrix. X‐ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nano‐CaCO₃ modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano‐CaCO₃ filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano‐CaCO₃. We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the β‐form crystal into the α‐form crystal took place in the composite system and the β‐form crystal had a higher nucleation rate and growth process than the α‐form crystal in the PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

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     

Preparation of nano poly(phenylsilsesquioxane) spheres(nano‐PPSQ) and study of the thermal stability and crystallization behavior of PP/nano‐PPSQ composites

The preparation of nano poly(phenylsilsesquioxane) particles (nano‐PPSQ) and the influence of nano‐PPSQ on the thermal stability and crystallization of polypropylene (PP) were studied. The morphology and thermal stability of PP/nano‐PPSQ composites were characterized by scanning electron microscopy (SEM) and the thermogravimetric analysis (TGA). The SEM result showed that the particles were well dispersed in the PP matrix. The TGA results of the PP/nano‐PPSQ composites indicated that the incorporation of nano‐PPSQ can improve the thermal stability of PP. The crystallization behavior and kinetics of PP/nano‐PPSQ composite were studied by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD revealed that the addition of nano‐PPSQ influences the crystallinity and crystal size of PP. The Avrami, Ozawa, and combined Avrami/Ozawa (Mo method) equations were applied to describe the crystallization kinetics and estimate the kinetic parameters of mathematical models under the nonisothermal crystallization of PP and PP/nano‐PPSQ composites. The results show that nano‐PPSQ influences the crystallization temperature and rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The physical and mechanical properties of beta‐nucleated polypropylene/montmorillonite nanocomposites

Polypropylene (PP) and polypropylene/polypropylene‐g‐maleic anhydride/ organomontmorillonite (PP/PP‐g‐MA/OMMT) nanocomposites were modified with 0.05 to 0.3% (w/w) of the aryl amide β‐nucleator to promote the formation of hexagonal crystal modification (β‐phase) during melt crystallization. The nonisothermal crystallization behavior of PP, PP/PP‐g‐MA/OMMT and β‐nucleated PP/PP‐g‐MA/OMMT nanocomposites were studied by means of differential scanning calorimetry. Structure‐property relationships of the PP nanocomposites prepared by melt compounding were mainly focused on the effect and quantity of the aryl amide nucleator. The morphological observations, obtained from scanning electron microscopy, transmission electron microscopy and X‐ray diffraction analyses are presented in conjunction with the thermal, rheological, and mechanical properties of these nanocomposites. Chemical interactions in the nanocomposites were observed by FT‐IR. It was found that the β‐crystal modification affected the thermal and mechanical properties of PP and PP/PP‐g‐MA/OMMT nanocomposites, while the PP/PP‐g‐MA/OMMT nanocomposites of the study gained both a higher impact strength (50%) and flexural modulus (30%) compared to that of the neat PP. β‐nucleation of the PP/PP‐g‐MA/OMMT nanocomposites provided a slight reduction in density and some 207% improvement in the very low tensile elongation at break at 92% beta nucleation. The crystallization peak temperature (T_cp) of the PP/PP‐g‐MA/OMMT nanocomposite was slightly higher (116°C) than the neat PP (113°C), whereas the β‐nucleation increased the crystallization temperature of the PP/PP‐g‐MA/OMMT/aryl amide to 128°C, which is of great advantage in a commercial‐scale mold processing of the nanocomposites with the resulting lower cycle times. The beta nucleation of PP nanocomposites can thus be optimized to obtain a better balance between thermal and mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

PP/PP-g-MAH/废PCB粉复合材料非等温结晶动力学研究

利用差示扫描量热法结合Avrami方程研究了聚丙烯（PP）、聚丙烯/聚丙烯接枝马来酸酐/废印刷电路板非金属粉复合材料（PP/PP-g-MAH/废PCB粉）的非等温结晶动力学行为,根据Avrami方程的Jeziorny法和莫志深法对数据进行处理。结果表明,废PCB粉在PP基体中起到异相成核作用,提高了PP的结晶温度,使其成核速率加快,晶粒分布变窄,结晶速率增大,但当废PCB粉含量过多时,复合材料体系黏度会增大,使PP链段扩散迁移并进行规整有序排列的速度受到影响,导致结晶速率下降。     

Overall crystallization behavior of polypropylene–clay nanocomposites; Effect of clay content and polymer/clay compatibility on the bulk crystallization and spherulitic growth

The effect of clay nanoparticles on the overall crystallization (isothermal crystallization, spherulitic growth, and nonisothermal crystallization) behavior of polypropylene (PP) was studied by means of differential scanning calorimetry and polarized light optical microscopy. In addition, the changes produced by the compatibility between the filler and the matrix were analyzed by using more hydrophobic clays or incorporating PP grafted with maleic anhydride (PP‐g‐MA). Different models were used to predict the relative degree of crystallinity and several parameters were analyzed. A clear nucleating effect of clay nanoparticles was found on the experimental behavior (induction time, half‐crystallization time, and overall crystallization time) and also deducted from the models parameters (Avrami exponent, rate constant, nucleation activity, activation energy). The effect was also related with the matrix/clay compatibility. In addition, the polarized light optical microscopy showed that the number of spherulites increased and their size decreased when clay was incorporated, which is also an indication of the heterogeneous nucleating behavior of such particles. We also noted faster spherulitic growth and increasing K_g (the model parameter). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization,melting behavior,and morphology of polypropylene/linear bimodal polyethylene blends

The nonisothermal crystallization, melting behavior, and morphology of isotactic polypropylene (PP)/linear bimodal polyethylene (LBPE) blends were studied with differential scanning calorimetry, scanning electron microscopy, and polarized optical microscopy. The results showed that PP and LBPE were miscible to a certain extent, and there was no obvious phase separation in the blends. The modified Avrami analysis, Ozawa equation, and Mo method were used to analyze the nonisothermal crystallization kinetics of the blends. The values of the Avrami exponent indicated that the crystallization nucleation of the blends was homogeneous, the growth of spherulites was three‐dimensional, and the crystallization mechanism of PP was not affected much by LBPE. The crystallization activation energy was estimated by the Kissinger method. The results obtained with the modified Avrami analysis, Mo method, and Kissinger method agreed well. The addition of a minor LBPE phase favored an increase in the overall crystallization rate of PP, showing some dilution effect of LBPE on PP. The PP spherulites decreased obviously with increasing content of LBPE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

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     

Effects of interfacial adhesion on properties of polypropylene/Wollastonite composites

Wollastonite reinforced polypropylene (PP/CaSiO₃) composites were prepared by melt extrusion. A silane coupling agent and a maleic anhydride grafted PP (PP‐g‐MA) were used to increase the interfacial adhesion between the filler and the matrix. The increased adhesion observed by scanning electron microscopy (SEM) resulted in improved mechanical properties. A model was applied to describe the relationship between the interfacial adhesion and tensile properties of PP/CaSiO₃ composites. There is stronger interfacial adhesion between silane‐treated CaSiO₃ and polymer matrix containing PP‐g‐MA as a modifier. Results of dynamic mechanical thermal analysis (DMTA) showed that stronger interfacial adhesion led to higher storage modulus. The influence of CaSiO₃ particles on the crystallization of PP was studied by using differential scanning calorimetry (DSC). The introduction of CaSiO₃ particles does not affect the crystallization temperature and crystallinity of PP matrix significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Melting behavior,isothermal and nonisothermal crystallization kinetics of PP/mLLDPE blends

Melting behavior, nonisothermal crystallization and isothermal crystallization kinetics of polypropylene (PP) with metallocene‐catalyzed linear low density polyethylene (mLLDPE) were studied by differential scanning calorimetry (DSC). The results show that PP and mLLDPE were partially miscible. The Avrami analysis was applied to analyze the nonisothermal and isothermal crystallization kinetics of the blends, the Mo Z.S. method was used to take a comparison in nonisothermal kinetics. Values of Avrami exponent indicate the crystallization nucleations of both pure PP and PP in the blends were heterogeneous, the growth of spherulites is tridimensional and the spherulites in the blends were more perfect than that in pure PP. The crystallization activation energy was estimated by Kissinger method and Arrhenius equation and the two methods draw similar results. The mLLDPE increased the crystallization rate of PP in nonisothermal crystallization process and decreased it in isothermal process. The results from nonisothermal crystallization and isothermal crystallization kinetics were not consistent because the two processes were completely different. Addition of minor mLLDPE phase favors to increase the overall crystallinity of PP, showing the mLLDPE entered the PP crystals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization behavior of starch‐filled polypropylene

Starches of different granule sizes, including corn, rice, and amaranth starches, were used to prepare starch‐filled polypropylene (PP) and the effect of starch granule size on crystallization behavior PP was investigated. Differential scanning calorimetry and scanning electron microscopy were used to monitor the energy changes of the crystallization of the melt and to characterize the morphology of PP/starch composites, respectively. Little interaction was observed between starch and PP despite the difference in starch granule size. The crystallization temperature of PP decreased with the addition of starch and this decrease became more apparent with increasing starch granule size. During nonisothermal crystallization, the dependency of the relative degree of crystallinity on time was described by the Avrami equation. The addition of starch decreased the overall crystallization rate of PP, which was attributed to an increase in the activation energy of crystallization under nonisothermal conditions according to the Kissinger equation. An increase in starch granule size of starch would increase the crystallization activation energy of PP and consequently decrease its crystallization rate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 484–492, 2004     

Nonisothermal crystallization,melting behavior,and morphology of polypropylene/metallocene‐catalyzed polyethylene blends

The nonisothermal crystallization, melting behavior, and morphology of blends of polypropylene (PP) and a metallocene‐catalyzed polyethylene (mPE) elastomer were studied with differential scanning calorimetry, scanning electron microscopy, polarized optical microscopy, and X‐ray diffraction. The results showed that PP and mPE were partially miscible and could form some cocrystallization, although the extent was very small. A modified Avrami analysis and the Mo method were used to analyze the nonisothermal crystallization kinetics of the blends. The values of the Avrami exponent indicated that the crystallization nucleation of the blends was homogeneous, the growth of the spherulites was three‐dimensional, and the crystallization mechanism of PP was not affected by mPE. The crystallization activation energy was estimated with the Kissinger method. Interesting results were obtained with the modified Avrami analysis and Mo and Kissinger methods, and the conclusions were in good agreement. The addition of less mPE increased the overall crystallization rate of PP. The relationship between the composition and morphology of the blends was examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1203–1210, 2004     

Melting,nonisothermal crystallization behavior and morphology of polypropylene/random ethylene—propylene copolymer blends

The melting, nonisothermal crystallization behavior and morphology of blends of polypropylene (PP) with random ethylene–propylene copolymer (PP‐R) were studied by differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X‐ray diffraction. The results showed that PP and PP‐R were very miscible and cocrystallizable. Modified Avrami analysis was used to analyze the nonisothermal crystallization kinetics of the blends. The values of the Avrami exponent indicated that the crystallization nucleation of the blends was heterogeneous, the growth of the spherulites was tridimensional, and the crystallization mechanism of PP was not affected by PP‐R. The crystallization activation energy was estimated using the Kissinger method. An interesting result was obtained with the modified Avrami analysis and the Kissinger method, whose conclusions were in good agreement. The addition of a minor PP‐R phase favored an increase in the overall crystallization rate of PP. Maximum enhancing effect wass found to occur with a PP‐R content of 20 wt %. The relationship between the composition and the morphology of the blends is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 670–678, 2006     

Crystallization behavior of polyamide 11/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC) was used to investigate the isothermal and nonisothermal crystallization kinetics of polyamide11 (PA11)/multiwalled carbon nanotube (MWNTs) composites. The Avrami equation was used for describing the isothermal crystallization behavior of neat PA11 and its nanocomposites. For nonisothermal studies, the Avrami model, the Ozawa model, and the method combining the Avrami and Ozawa theories were employed. It was found that the Avrami exponent n decreased with the addition of MWNTs during the isothermal crystallization, indicating that the MWNTs accelerated the crystallization process as nucleating agent. The kinetic analysis of nonisothermal crystallization process showed that the presence of carbon nanotubes hindered the mobility of polymer chain segments and dominated the nonisothermal crystallization process. The MWNTs played two competing roles on the crystallization of PA11 nanocomposites: on the one hand, the MWNTs serve as heterogeneous nucleating agent promoting the crystallization process of PA11; on the other hand, the MWNTs hinder the mobility of the polymer chains thus retarding the crystal growth process of PA11. The activation energies of PA11/MWNTs composites for the isothermal and nonisothermal crystallization are lower than neat PA11. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Nonisothermal crystallization kinetics of AB2 hyperbranched polymer‐filled polypropylene

In this article, nonisothermal crystallization kinetics of polypropylene (PP) and AB₂ hyperbranched polymer (HBP)‐filled PP have been investigated by differential scanning calorimetry. The Avrami analysis modified by Mandelkern and a method combined with Avrami and Ozawa equations were employed to describe successfully the nonisothermal crystallization kinetics of samples. The conclusion showed that HBP can prompt crystallization effectively. Furthermore, in blends of different HBP contents, the value of t_1/2 became smaller with increasing HBP content; however, the crystallization rate of the blend decreased slightly when content of HBP is 5%. An increase in the Avrami exponent showed that addition of HBP influenced the mechanism of nucleation and the growth of PP crystallites. The possible explanation could be attributed to the fractal structure of HBP. The polarized micrographs showed that HBP acts as a heterogeneous nucleation agent, and the nucleation efficiency has increased remarkably in HBP/PP blends. POLYM. ENG. SCI., 53:2535–2540, 2013. © 2013 Society of Plastics Engineers