Crystallization of poly(butylene terephthalate)/poly(ethylene octene) blends: Nonisothermal crystallization

Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (T_mI and T_mII). T_mI was attributed to the melting of the crystals grown by normal primary crystallization, and T_mII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well‐ dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen–Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Isothermal crystallization of poly(ethylene‐co‐glycidyl methacrylate)/clay nanocomposites

Poly(ethylene‐co‐glycidyl methacrylate) (PEGMA)/clay nanocomposites with clay concentrations of 1, 3, or 5 wt % were prepared via y melt blending in a twin‐screw extruder. Wide‐angle X‐ray diffraction showed that the clay layers were intercalated by PEGMA. Differential scanning calorimetry was used to analyze the isothermal crystallization, and the equilibrium melting temperature was determined with the Hoffman–Weeks method. The Avrami, Tobin, Malkin, and Urbanovici–Segal models were applied to describe the kinetics of crystallization from the melt state under isothermal conditions. The crystallization kinetics showed that the addition of clay facilitated the crystallization of PEGMA, with the clay functioning as a heterophase nucleating agent; at higher concentrations, however, the physical hindrance of the clay layers to the motion of PEGMA chains retarded the crystallization process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1051–1064, 2005     

Nonisothermal crystallization kinetics of nucleated poly(ethylene terephthalate)

Studies of the nonisothermal crystallization kinetics of poly(ethylene terephthalate) nucleated with anhydrous sodium acetate were carried out. The chemical nucleating effect was investigated and confirmed with Fourier transform infrared and intrinsic viscosity measurements. The Avrami, Ozawa, and Liu models were used to describe the crystallization process. The rates of crystallization, which initially increased, decreased at higher loadings of the additive. The activation energy, calculated with Kissinger's method, was lower for nucleated samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/multiwalled carbon nanotubes nanocomposites prepared by in situ polymerization

Poly(butylene terephthalate)/multiwalled carbon nanotubes (PBT/MWNT) nanocomposites were prepared by in situ ring‐opening polymerization of cyclic butylene terephthalate oligomers (CBT). The nonisothermal crystallization behavior of the neat PBT and the PBT/MWNT nanocomposites was analyzed quantitatively. The results reveal that the combined Avrami/Ozawa equation exhibits great advantages in describing the nonisothermal crystallization of PBT and its nanocomposites. The presence of MWNTs has the nucleation effect promoting crystallization rate for the nanocomposites, and the maximum one is observed in the nanocomposite having 0.75 wt % MWNT content. On the other hand, the addition of MWNTs has the impeding effect reducing the chain mobility and retarding crystallization, which is confirmed by the crystallization activation energies. However, the nucleation effect of MWNTs plays the dominant role in the crystallization of PBT/MWNT nanocomposites, in other words, the incorporation of MWNTs is increasing the crystallization rate of the nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40849.     

Preparation,crystallization, and properties of biodegradable poly(butylene adipate‐co‐terephthalate)/organomodified montmorillonite nanocomposites

Intercalated and exfoliated nanocomposites of biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) and Cloisite 30B (C30B) were fabricated by a solution‐casting method to study the effects of the clay loading on the crystallization behavior, thermal stability, and dynamic mechanical properties of PBAT in PBAT/C30B nanocomposites. X‐ray diffraction and transmission electron microscopy results indicated the formation of exfoliated nanocomposites at low clay loadings (<5 wt %) and a mixture of exfoliated and intercalated nanocomposites with a clay content of 8 wt % throughout the PBAT matrix. Nonisothermal melt crystallization studies indicated that C30B enhanced the crystallization of PBAT, apparently because of a heterogeneous nucleation effect. Moreover, an attempt was made to quantitatively study the influence of the presence of C30B and its contents on the nucleation activity of PBAT in the PBAT/C30B nanocomposites. The thermal stability of PBAT decreased slightly in the nanocomposites. However, the storage modulus of PBAT apparently increased with the C30B loading increasing in the PBAT/C30B nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isothermal crystallization kinetics of anhydrous sodium acetate nucleated poly(ethylene terephthalate)

Studies on the isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) nucleated with anhydrous sodium acetate were carried out. The nucleated agent had succeeded in promoting greater rates of crystallization in PET. A study of the melting behavior of the samples revealed that the nucleating agents promoted formation of thinner lamellae. The equilibrium melting temperature (T) of samples was determined using linear and nonlinear Hoffman Weeks procedure. The nonlinear Hoffman Week's procedure was found to be inapplicable in the current study. The Lauritzen‐Hoffman secondary nucleation theory was applied to determine the nucleation parameter (K_g), fold surface energy (σ_e), and work of chain folding (q). σ_e and q decreased on addition of nucleating agent. The approximate and exact form of the Lauritzen Z‐test was used to determine the operating regime. The operating regime was found to be primarily regime II for the range of temperatures studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nonisothermal crystallization of polyamide 66/poly(phenylene sulfide) blends

The crystalline morphologies of isothermally and nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with polyamide 66 (PA66) were investigated by polarized optical microscopy with a hot stage. The spherulite superstructure of PPS was greatly affected by crystallizable PA66; a Maltese cross was not clear, and the impingement between spherulites disappeared. This could be ascribed to the formation of small crystals of PA66, which filled in the PPS lamellae. The nonisothermal crystallization behavior was also measured by differential scanning calorimetry. The presence of PA66 changed the nonisothermal crystallization process of PPS. The maximum crystallization temperature of the PPS phase in the blend was higher that that of neat PPS, and this indicated that PA66 acted as a nucleus for PPS. Also, the compatibilizer poly(ethylene‐stat‐methacrylate) (EMA) was added to modify the interfacial interplay of the PA66/PPS blend system. The addition of EMA greatly influenced the nonisothermal crystallization process of the PPS phase in the blend system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nonisothermal crystallization kinetics of linear metallocene polyethylenes

The effect of weight‐average molecular weight (M_w) on the nonisothermal crystallization kinetics of linear metallocene polyethylene (m‐PE) was studied with modulated differential scanning calorimetry. Six linear m‐PEs of molecular weights in the range 122–934 kg/mol were prepared by gas‐phase polymerization. The cooling rate (R) was varied in the range 2–20°C/min, and it significantly affected the crystallization behavior. M_w had a weak influence on both the peak crystallization temperature and the crystallization onset temperature. All m‐PEs showed primary and secondary crystallizations. At both low and high R's, the crystallinity showed a significant drop (～ 30%) when M_w was increased from 122 to 934 kg/mol. At low R's (< 10°C/min), the rate parameters in the modified Avrami method [primary rate constant (k_R)] and Mo method [F(T)] of analyses agreed in suggesting that an increased M_w slowed the rate of crystallization. The M_w dependency of k_R followed the Arrhenius type (k_R = k_Roe²⁸¹/M_w, where k_Ro is a rate‐dependent constant). However, at higher R's, k_R approached a constant value. The order parameters obtained by the different methods of analysis (n and α) were independent of M_w, which suggests that the crystal type remained the same. Hoffman–Lauritzen theory was used for data analysis, and activation energy per segment showed a significant decrease, from 225.0 to 11.8 kJ/mol, when M_w was increased from 152 to 934 kg/mol. Finally, all methods of analysis suggested a significant effect of M_w on slowing the overall crystallization process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Nonisothermal crystallization behavior of poly (butylene terephthalate)–poly (ethylene terephthalate‐co‐isophthalate‐co‐sebacate) segmented copolyesters

In this paper, two different analytical methods were applied to investigate nonisothermal crystallization behavior of copolyesters prepared by melting transesterification processing from bulk polyesters involving poly (butylene terephthalate) (PBT) and ternary amorphous random copolyester poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) (PETIS). The results show that the half‐time of crystallization of copolyesters depended on the reaction time and decreased with the content of ternary polyesters in the amorphous segment. The modified Avrami model describes the nonisothermal crystallization kinetics very well. The values of the Avrami exponent range from 2.2503 to 3.7632, and the crystallization kinetics constant ranges from 0.0690 to 0.9358, presenting a mechanism of three‐dimensional spherulitic growth with heterogeneous nucleation. Ozawa analysis, however, failed to describe the nonisothermal crystallization behavior of copolyesters, especially at higher cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1232–1238, 2003     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/poly(ethylene terephthalate)/glass fiber composites

The influences of the glass fiber (GF) content and the cooling rate for nonisothermal crystallization process of poly(butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blends were investigated. The nonisothermal crystallization kinetics of samples were detected by differential scanning calorimetry (DSC) at cooling rates of 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, respectively. The Jeziony and Mozhishen methods were used to analyze the DSC data. The crystalline morphology of samples was observed with polarized light microscope. Results showed that the Jeziony and Mozhishen methods were available for the analysis of the nonisothermal crystallization process. The peaks of crystallization temperature (T_p) move to low temperature with the cooling rate increasing, crystallization half‐time (t_1/2) decrease accordingly. The crystallization rate of PBT/PET blends increase with the lower GF contents while it is baffled by higher GF contents. POLYM. COMPOS. 36:510–516, 2015. © 2014 Society of Plastics Engineers     

Nonisothermal crystallization behaviors of poly(3‐hexylthiophene)/reduced graphene oxide nanocomposites

Poly(3‐hexylthiophene) (P3HT)/reduced graphene oxide (rGO) nanocomposites were prepared through in situ reduction of graphene oxide in the presence of P3HT. The nonisothermal crystallization behaviors of P3HT and P3HT/rGO nanocomposites were investigated by differential scanning calorimetry. The Avrami, Ozawa, and Mo models were used to analyze the nonisothermal kinetics. The addition of rGO remarkably increased the crystallization peak temperature and crystallinity of P3HT, but the crystallization half‐time revealed little variation. The crystallization activation energies were calculated by the Kissinger equation. The results suggested that rGO plays a twofold role in the nonisothermal crystallization of P3HT, that is, rGO promotes the crystallization of P3HT as nucleating agent, and meanwhile, it also restricts the motion of P3HT chains. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nonisothermal crystallization kinetics of poly(vinylidene fluoride) in a poly(vinylidene fluoride)/dibutyl phthalate/di(2‐ethylhexyl)phthalate system via thermally induced phase separation

The nonisothermal crystallization kinetics of poly(vinylidene fluoride) (PVDF) in PVDF/dibutyl phthalate (DBP)/di(2‐ethylhexyl)phthalate (DEHP) blends via thermally induced phase separation were investigated through differential scanning calorimetry measurements. The Ozawa approach failed to describe the crystallization behavior of PVDF in PVDF/DBP/DEHP blends, whereas the modified Avrami equation successfully described the nonisothermal crystallization process of PVDF. Two stages of crystallization were observed in this analysis, including primary crystallization and secondary crystallization. The influence of the cooling rate and DBP ratio in the diluent mixture on the crystallization mechanism and crystal structure was determined by this method. The Mo approach well explained the kinetics of primary crystallization. An analysis of these two methods indicated that the increase in the DBP ratio in the diluent mixture caused a decrease in the crystallization rate at the primary crystallization stage. The activation energy was determined according to the Kissinger method and also decreased with the DBP ratio in the diluent mixture increasing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization kinetics and melting behavior of nylon 10,10 in nylon 10,10–montmorillonite nanocomposites

The crystallization kinetics and melting behavior of nylon 10,10 in neat nylon 10,10 and in nylon 10,10–montmorillonite (MMT) nanocomposites were systematically investigated by differential scanning calorimetry. The crystallization kinetics results show that the addition of MMT facilitated the crystallization of nylon 10,10 as a heterophase nucleating agent; however, when the content of MMT was high, the physical hindrance of MMT layers to the motion of nylon 10,10 chains retarded the crystallization of nylon 10,10, which was also confirmed by polarized optical microscopy. However, both nylon 10,10 and nylon 10,10–MMT nanocomposites exhibited multiple melting behavior under isothermal and nonisothermal crystallization conditions. The temperature of the lower melting peak (peak I) was independent of MMT content and almost remained constant; however, the temperature of the highest melting peak (peak II) decreased with increasing MMT content due to the physical hindrance of MMT layers to the motion of nylon 10,10 chains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2181–2188, 2003     

Nonisothermal melt crystallization kinetics of poly(ethylene terephthalate)/Barite nanocomposites

Poly(ethylene terephthalate) (PET)/Barite nanocomposites were prepared by direct melt compounding. The nonisothermal melt crystallization kinetics of pure PET and PET/Barite nanocomposites, containing unmodified Barite and surface‐modified Barite (SABarite), was investigated by differential scanning calorimetry (DSC) under different cooling rates. With the addition of barite nanoparticles, the crystallization peak became wider and shifted to higher temperature and the crystallization rate increased. Several analysis methods were used to describe the nonisothermal crystallization behavior of pure PET and its nanocomposites. The Jeziorny modification of the Avrami analysis was only valid for describing the early stage of crystallization but was not able to describe the later stage of PET crystallization. Also, the Ozawa method failed to describe the nonisothermal crystallization behavior of PET. A combined Avrami and Ozawa equation, developed by Liu, was used to more accurately model the nonisothermal crystallization kinetics of PET. The crystallization activation energies calculated by Kissinger, Takhor, and Augis‐Bennett models were comparable. The results reveal that the different interfacial interactions between matrix and nanoparticles are responsible for the disparate effect on the crystallization ability of PET. POLYM. COMPOS., 31:1504–1514, 2010. © 2009 Society of Plastics Engineers     

Nonisothermal crystallization kinetics of biodegradable poly(butylene succinate)/poly(vinyl phenol) blend

Nonisothermal melt crystallization kinetics of biodegradable PBSU/PVPh blend was investigated with differential scanning calorimetry (DSC) from the viewpoint of practical application. PBSU/PVPh blends were cooled from the melt at various cooling rates ranging from 2.5 to 40°C/min. The crystallization peak temperature decreased with increasing the cooling rate for both neat and blended PBSU. Furthermore, the crystallization peak temperature of PBSU in the blend was lower than that of neat PBSU at a given cooling rate. Two methods, namely the Avrami equation and the Tobin method, were used to describe the nonisothermal crystallization of PBSU/PVPh blend. It was found that the Avrami equation was more suitable to predict the nonisothermal crystallization of PBSU/PVPh blend than the Tobin method. The effects of cooling rate and blend composition on the crystallization behavior of PBSU were studied in detail. It was found that the crystallization rate decreased with decreasing the cooling rate for both neat and blended PBSU. However, the crystallization of PBSU blended with PVPh was retarded compared with that of neat PBSU at the same cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 972–978, 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     

Nonisothermal crystallization behavior and mechanical properties of poly(butylene succinate)/silica nanocomposites

Silica nanoparticles and poly(butylene succinate) (PBS) nanocomposites were prepared by a melt‐blending process. The influence of silica nanoparticles on the nonisothermal crystallization behavior, crystal structure, and mechanical properties of the PBS/silica nanocomposites was investigated. The crystallization peak temperature of the PBS/silica nanocomposites was higher than that of neat PBS at various cooling rates. The half‐time of crystallization decreased with increasing silica loading; this indicated the nucleating role of silica nanoparticles. The nonisothermal crystallization data were analyzed by the Ozawa, Avrami, and Mo methods. The validity of kinetics models on the nonisothermal crystallization process of the PBS/silica nanocomposites is discussed. The approach developed by Mo successfully described the nonisothermal crystallization process of the PBS and its nanocomposites. A study of the nucleation activity revealed that the silica nanoparticles had a good nucleation effect on PBS. The crystallization activation energy calculated by Kissinger's method increased with increasing silica content. The modulus and yield strength were enhanced with the addition of silica nanoparticles into the PBS matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on crystallization behaviors and crystal morphology of polyamide 66/clay nanocomposites

X‐ray diffraction methods, DSC thermal analysis, and polarized light microscopy (PLM) were used to investigate the structural changes of nylon 66/clay nanocomposites. PA 66/clay nanocomposites were prepared by the method of melt intercalation. The results indicate that the addition of the intercalated organo‐montmorillonite (OMMT) can induce generation of the β‐form crystal of PA 66 and substantially affect the arrangement of molecules in the α‐form crystal, although the crystallinity scarcely changes. Also, the DSC results indicate that the addition of OMMT in the PA 66 matrix leads to increases of crystallization temperatures and the full width at half maximum (FWHM) of the exothermic peaks. Moreover, the viscosity factor is the main influence on FWHM of the exothermic peaks of PA 66/clay nanocomposites. The results of nonisothermal crystallization kinetics show that OMMT has the effect of heterogeneous nucleation and leads to the decrease of the size of the spherocrystal. The heterogeneous nucleation effects of OMMTs influence the mechanism of crystallization and the growth mode of PA 66 crystals. PLM photographs verify that the size of spherocrystal is decreased and visually confirm the theory of crystallization kinetics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 756–763, 2005