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     

Nonisothermal crystallization behavior and crystals morphology of poly(trimethylene terephthalate)/nano‐calcium carbonate composites

Nonisothermal crystallization behavior and crystal morphology of poly(trimethylene terephthalate) (PTT) composites filled with modified nano‐calcium carbonate (CaCO₃) had been investigated by using differential scanning calorimetry and polarized optical microscopy. The modified Avrami equation and Ozawa theory were used to investigate the nonisothermal crystallization, respectively. The particles of nano‐CaCO₃, acting as a nucleation agent in composites, accelerated the crystallization rate by decreasing the half‐time of crystallization or increasing the parameters of Z_c and K(T). Moreover, the nano‐composite with 2 wt% nano‐CaCO₃ exhibited the highest crystallization rate. The Avrami and the Ozawa exponents, n and m of the nano‐composites, were higher than those of neat PTT, suggesting more complicated interaction between molecular chains and the nanoparticles that cause the changes of the nucleation mode and the crystal growth dimension. The effective activation energy calculated from the Friedman formula was reduced as nano‐CaCO₃ content increased, suggesting that the nano‐CaCO₃ made the molecular chains of PTT easier to crystallize during the nonisothermal crystallization process. The optical micrographs showed that much smaller or less perfect crystals were formed in composites because of the presence of the nano‐CaCO₃ particles. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

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     

Thermal oxidative degradation kinetics of PP and PP/mg (OH)2 flame‐retardant composites

The thermal stability and thermal oxidative degradation kinetics of polypropylene (PP) and flame‐retardant PP composites filled with untreated and treated magnesium hydroxide (MH) in air were studied by thermogravimetric analysis (TGA). The effect of the heating rate in dynamic measurements (5°C–30°C/min) on kinetic parameters such as activation energy was also investigated. The Kissinger and Flynn–Wall–Ozawa methods were used to determine the apparent activation energy for the degradation of neat PP and flame‐retardant PP composites. The results of TGA showed that the addition of untreated or treated MH improved the thermal oxidative stability of PP in air. The kinetic results showed that the apparent activation energy for degradation of flame‐retardant PP composites was much higher than that of neat PP, suggesting that the flame retardant used in this work had a great effect on the mechanisms of pyrolysis and combustion of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1978–1984, 2007     

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     

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     

Fabrication and properties of nano‐ZnO/glass‐fiber‐reinforced polypropylene composites

Polypropylene (PP) is widely used in many fields, such as automobiles, medical devices, office equipment, pipe, and architecture. However, its high brittle transformation temperature, low mechanical strength, dyeing properties, antistatic properties, and poor impact resistance, considerably limit its further applications. Nano‐ZnO treated by KH550 coupling agent and glass fibers (GFs) were introduced in order to improve the mechanical performance and flowability of PP in this research. The crystallization behavior and microstructure of nano‐ZnO/GFs/PP hybrid composites were analyzed by differential scanning calorimetry, transmission electron microscopy, and scanning electron microscopy. The effect of crystallization behavior on the mechanical properties of the nanocomposites was investigated and analyzed. The results indicated that nano‐ZnO surface‐coupled by KH550 could be uniformly dispersed in the PP matrix. The incorporation of nano‐ZnO and GFs resulted in increases of the crystallization temperature and crystallization rate of PP and a decrease of the crystallization degree. The introduction of nano‐ZnO and GFs also enhanced the tensile strength and impact toughness of the hybrid composites and improved their fluidity. Composites containing 2% of nano‐ZnO and 40% of GFs possessed the optimum mechanical properties. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

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     

Nonisothermal crystallization behavior of biodegradable poly(butylene terephthalate‐co‐butylene adipate‐co‐ethylene terephthalate‐co‐ethylene adipate) copolyester

A series of biodegradable aliphatic‐aromatic copolyester, poly(butylene terephthalate‐co‐butylene adipate‐co‐ethylene terephthalate‐co‐ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4‐butanediol (BG) and ethylene glycol (EG) by direct esterification and polycondensation. The nonisothermal crystallization behavior of PBATE copolyesters was studied by the means of differential scanning calorimeter, and the nonisothermal crystallization kinetics were analyzed via the Avrami equation modified by Jeziorny, Ozawa analysis and Z.S. Mo method, respectively. The results show that the crystallization peak temperature of PBATE copolyesters shifted to lower temperature at higher cooling rate. The modified Avrami equation could describe the primary stage of nonisothermal crystallization of PBATE copolyesters. The value of the crystallization half‐time (t_1/2) and the crystallization parameter (Z_c) indicates that the crystallization rate of PBATE copolyesters with more PTA content was higher than that with less PTA at a given cooling rate. Ozawa analysis was not suitable to study the nonisothermal crystallization process of PBATE copolyesters, but Z.S. Mo method was successful in treatingthis process. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Thermal properties and non‐isothermal crystallization behavior of biodegradable poly(p‐dioxanone)/poly(vinyl alcohol) blends

Blends of two biodegradable semicrystalline polymers, poly(p‐dioxanone) (PPDO) and poly(vinyl alcohol) (PVA) were prepared with different compositions. The thermal stability, phase morphology and thermal behavior of the blends were studied by using thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). From the TGA data, it can be seen that the addition of PVA improves the thermal stability of PPDO. DSC analysis showed that the glass transition temperature (T_g) and the melting temperature (T_m) of PPDO in the blends were nearly constant and equal to the values for neat PPDO, thus suggesting that PPDO and PVA are immiscible. It was found from the SEM images that the blends were phase‐separated, which was consistent with the DSC results. Additionally, non‐isothermal crystallization under controlled cooling rates was explored, and the Ozawa theory was employed to describe the non‐isothermal crystallization kinetics. Copyright © 2006 Society of Chemical Industry     

Investigation on preparation and property of nano‐CaCO3/PP masterbatch modified by reactive monomers

Nano‐CaCO₃/polypropylene (PP) masterbatch containing above 80 wt % nano‐CaCO₃ was prepared by nano‐CaCO₃ coated PP modified by reactive monomers. The chemical interaction, crystallization and melting behavior, thermal stability, morphology, and surface contact angle of masterbatch were investigated with IR, DSC, TEM, TGA, ESCA, and surface contact angle. The results indicated that nano‐CaCO₃ was coated by PP graft copolymers in the masterbatch modified by reactive monomers. The graft ratio and crystallization and melting behavior of PP in the masterbatch depended on the type and content of reactive monomer. The crystallization temperatures of masterbatch modified by reactive monomer is methyl methacrylate > butyl acrylate > methyl acrylate ≈ mixture of acrylic acid and styrene > unmodified ≈ maleic anhydride ≈ acrylic acid > styrene. Modification by reactive monomer increased the thermal stability and surface contact angle of masterbatch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3907–3914, 2006     

Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano‐CaCO3

The isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) composites filled with nano‐CaCO₃ were investigated at designated temperatures with differential scanning calorimetry. The Avrami equation was used to fit the isothermal crystallization. The Avrami exponents were determined to be 2–3 for the neat PTT and PTT/CaCO₃ composites. The particles of nano‐CaCO₃, acting as nucleating agents in the composites, accelerated the crystallization rate, with the half‐time of crystallization decreasing or the growth rate constant (involving both nucleation and growth rate parameters) increasing. The crystallization activation energy calculated from the Arrhenius formula was reduced as the nano‐CaCO₃ content increased from 0 to 2%, and this suggested that nano‐CaCO₃ made the molecular chains of PTT easier to crystallize during the isothermal crystallization process. Subsequent melting scans of the isothermally crystallized composites exhibited triple or double melting endotherms: the greater the content was of nano‐CaCO₃, the lower the temperature was of the melting peak. The degree of crystallization deduced from the melt enthalpy of composites with the proper concentration of nano‐CaCO₃ was higher than that of pure PTT, but it was lower when the nano‐CaCO₃ concentration was more than 2%. The transmission electron microscopy pictures suggested that the dispersion state of nano‐CaCO₃ particles in the polymer matrix was even when its concentration was no more than 2%, whereas some agglomeration occurred when its concentration was 4%. Polarized microscopy pictures showed that much smaller or less perfect crystals formed in the composites because of the interaction between the molecular chains and nano‐CaCO₃ particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Nonisothermal crystallization kinetics of polypropylene‐layered double hydroxide composites: Correlation with morphology

In this work the effect of nanofiller on nonisothermal crystallization behavior of composites based on polypropylene (PP) was investigated by differential scanning calorimetry. The materials were prepared by melt mixing. Both an alkyl sulfonate salt modified layered double hydroxide (LDH) and an unmodified LDH were used as nanofillers and both PP and PP/polypropylene grafted with maleic anhydride (PP‐g‐MA) blend were used as matrices. The morphology of composites was investigated by X‐ray diffraction and transmission electron microscopy. No exfoliation was noticed in all prepared composites, but the hybrid materials showed an intercalated structure. The thermal properties and crystallization behavior were studied by conventional differential scanning calorimetry. In particular, the kinetic crystallization parameters were obtained using the modified Avrami equation for a nonisothermal process, whereas the activation energy of the global crystallization process was estimated using the Kissinger equation. The Avrami parameters suggest a significant effect on the crystallization of PP for the composites containing both the organically modified LDH and PP‐g‐MA. The results indicate a complex crystallization process of PP and evidence that the crystallization process can not be only explained by intercalation phenomenon, but the constrain effect ofpolymer chains on the filler surface and/or betweenthe filler clusters should play a significant role. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synergistic effects of nano‐Mn0.4Zn0.6Fe2O4 on intumescent flame‐retarded polypropylene

The melamine salt of 5,5‐dimethyl‐1,3,2‐dioxaphos‐phorinane‐2‐oxide‐2‐hydroxide (IFR100) was used as an intumescent flame retardant in flame‐retarded polypropylene (PP). As a synergistic agent, nano‐Mn_0.4Zn_0.6Fe₂O₄ was incorporated into the PP/IFR100 composite at different proportions. The synergistic effects of nano‐Mn_0.4Zn_0.6Fe₂O₄ were studied by the limiting oxygen index (LOI) test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The synergistic effect of the nano‐Mn_0.4Zn_0.6Fe₂O₄ additive with IFR100 was clearly observed by LOI. The TGA results showed that nano‐Mn_0.4Zn_0.6Fe₂O₄ improved the thermal stability of the PP/IFR100 system above 400°C. On the basis of the FTIR and XRD results, it was evident that nano‐Mn_0.4Zn_0.6Fe₂O₄ efficiently promoted the formation of a charred layer containing phosphocarbonaceous structures. The SEM micrographs indicated that nano‐Mn_0.4Zn_0.6Fe₂O₄ strengthened the structure of the char layer remaining after combustion. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Crystallization behavior and mechanical properties of polypropylene copolymer by in situ copolymerization with a nucleating agent and/or nano‐calcium carbonate

The crystallization behavior of polypropylene (PP) copolymer obtained by in situ reactor copolymerization with or without a nucleating agent and/or nano‐CaCO₃ particles was investigated both by thermal analysis and by polarized light microscopy. The Avrami model is successfully used to describe the crystallization kinetics of the studied copolymer. The results of the investigation show that a dramatic decrease of the half‐time of crystallization t_1/2, as well as a significant increase of the overall crystallization rate, are observed in the presence of the nucleating agent. These effects are further promoted in the presence of the nano‐CaCO₃ particles. The incorporation of the nucleating agent and nano‐CaCO₃ particles into PP copolymer remarkably improved the mechanical properties and heat distortion temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 431–438, 2004     

Thermal properties and crystallization behavior of bamboo fiber/high‐density polyethylene composites: Nano‐TiO2 effects

In this study, bamboo fiber/high‐density polyethylene (HDPE) composites were prepared, and the effects of nano‐TiO₂ on their thermal properties and crystallization behavior were investigated via thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that the addition of nano‐TiO₂ improved the thermal stability and had a dual function in the crystallization behavior of the composites. On one hand, it functioned as a nucleating agent. The addition of 2 wt % nano‐TiO₂ promoted the crystallization, which caused the increase of the crystallization rate and crystallinity degree, as well as the micronization of the crystalline grain. On the other hand, intermolecular hydrogen bonds and covalent bonds were formed between nano‐TiO₂ and the polymer matrix, which hindered the crystallization of the composites. When the content of nano‐TiO₂ was continually increased, the inhibitory effect of the crystallization was gradually enhanced, which resulted in a decrease in the crystallization rate and crystallinity degree of the composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39846.     

Plasticized and unplasticized PLA/organoclay nanocomposites: Short‐ and long‐term thermal properties,morphology, and nonisothermal crystallization behavior

The short‐ and long‐term thermal properties, organoclay dispersion state, and the nonisothermal crystallization kinetics of organoclay based nanocomposites of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) plasticized PLA were investigated. Differential scanning calorimetry analyses showed that plasticization of PLA/PEG blend was diminished due to physical aging by the time. The change in thermal properties such as glass transition temperature, cold crystallization temperature, and melting temperature was monitored. It was revealed from X‐ray diffraction analyses that in long term, the exfoliated and/or intercalated organoclay structure of nanocomposites observed in short term (just after processing) was differentiated to a tactoidal form (i.e., nonseparated clays). The nonisothermal crystallization behavior and kinetics were examined by using Avrami, Ozawa, and combined Avrami–Ozawa models. Moreover, the nucleating effect of clays was investigated in terms of Gutzow and Dobrewa approaches. It was found out that clays did not act as nucleating agents in plasticized PLA nanocomposites, which was also in good agreement with activation energy values obtained from Kissinger and Takhor models. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystallization and melting behavior of nano‐CaCO3/polypropylene composites modified by acrylic acid

Nano‐CaCO₃/polypropylene (PP) composites modified with polypropylene grafted with acrylic acid (PP‐g‐AA) or acrylic acid with and without dicumyl peroxide (DCP) were prepared by a twin‐screw extruder. The crystallization and melting behavior of PP in the composites were investigated by DSC. The experimental results showed that the crystallization temperature of PP in the composites increased with increasing nano‐CaCO₃ content. Addition of PP‐g‐AA further increased the crystallization temperatures of PP in the composites. It is suggested that PP‐g‐AA could improve the nucleation effect of nano‐CaCO₃. However, the improvement in the nucleation effect of nano‐CaCO₃ would be saturated when the PP‐g‐AA content of 5 phf (parts per hundred based on weight of filler) was used. The increase in the crystallization temperature of PP was observed by adding AA into the composites and the crystallization temperature of the composites increased with increasing AA content. It is suggested that the AA reacted with nano‐CaCO₃ and the formation of Ca(AA)₂ promoted the nucleation of PP. In the presence of DCP, the increment of the AA content had no significant influence on the crystallization temperature of PP in the composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2443–2453, 2004     

Morphology and properties of PP/EPDM binary blends and PP/EPDM/nano‐CaCO3 ternary blends

In this article, the morphology, crystallization, and rheological behaviors of polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) binary blend and PP/EPDM/calcium carbonate nanoparticles (nano‐CaCO₃) ternary blend were investigated. Two processing methods, i.e., direct extrusion and two‐step extrusion, were employed to prepare the PP/EPDM/CaCO₃ blend. The influence of EPDM and nano‐CaCO₃ respectively on phase morphology and properties of PP/EPDM blend and PP/EPDM/CaCO₃ blend were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and dynamic rheometer. The crystallinity and crystallization temperature of PP/EPDM blend were improved in comparison to pure PP due to addition of EPDM, but kept invariable with the increased EPDM loading. As the EPDM content was increased, the mobility of PP molecular chains was weakened. Compared with direct extruded blend, less and finer nano‐CaCO₃ was dispersed in matrix of two‐step extruded blend. Accordingly, the increased nano‐CaCO₃ in matrix gave rise to a weaker increment in crystallinity and crystallization temperature of two‐step extruded blend, and a later platform of tanδ curve. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011