Nonisothermal crystallization behavior of melt‐intercalated polyethylene‐clay nanocomposites

The influence of nanoclay particles on the nonisothermal crystallization behavior of intercalated polyethylene (PE) prepared by melt‐compounding was investigated. It is observed that the crystallization peak temperature (T_p) of PE/clay nanocomposites is slightly but consistently higher than the neat PE at various cooling rates. The half‐time (t_0.5) for crystallization decreased with increase in clay content, implying the nucleating role of nanoclay particles. The nonisothermal crystallization data are analyzed using the approach of Avrami (Polymer 1971, 12, 150), Ozawa (Polym Eng Sci 1997, 37, 443), and Mo and coworkers (J Res Natl Bur Stand 1956, 57, 217), and the validity of the different kinetic models to the nonisothermal crystallization process of PE/clay nanocomposites is discussed. The approach developed by Mo and coworkers successfully explains the nonisothermal crystallization behavior of PE and PE/clay nanocomposites. The activation energy for nonisothermal crystallization of neat PE and PE/clay nanocomposites is determined using the Kissinger (J Res Natl Bur Stand 1956, 57, 217) method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3809–3818, 2006     

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     

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 melt‐crystallization kinetics of hydroxyapatite‐filled poly(3‐hydroxybutyrate) composites

The knowledge of biomedical implants ranging from drug delivery devices to tissue engineering and based on bioresorbable polymer composites is increasing, but the study of the crystallization kinetics of these kinds of composites is seldom a concern. The focus of our experimental research was the nonisothermal‐crystallization behavior of poly(3‐hydroxybutyrate) (PHB)/hydroxyapatite (HA) composites, which was monitored by means of differential scanning calorimetry at different cooling rates. Various macrokinetic models were applied to describe the process of nonisothermal crystallization. The results showed that the modified Avrami model and Mo's approach could describe the nonisothermal crystallization of the composites very well, but the Ozawa analysis alone was thought to be rather inapplicable. The values of the half‐time and kinetic crystallizability showed that the crystallization rate increased with increasing cooling rates for both PHB and the composites. The HA particles served as additional nucleation sites, and low levels of HA resulted in dramatic increases in the crystallization rate with respect to pure PHB; however, high HA contents (> 20 wt %) clearly retarded the growth process. The activation energy for nonisothermal crystallization was evaluated with the Kissinger method and was found to vary with the incorporation of HA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5388–5395, 2006     

Nonisothermal crystallization behavior of a luminescent conjugated polymer,poly(9,9‐dihexylfluorene‐alt‐2,5‐didodecyloxybenzene)

The nonisothermal crystallization kinetics of poly(9,9‐dihexylfluorene‐alt‐2,5‐didodecyloxybenzene) (PF6OC12) from the melt were investigated using differential scanning calorimetry under different cooling rates. Several analysis methods were used to describe the nonisothermal crystallization behavior of PF6OC12. It was found that the modified Avrami method by Jeziorny was only valid for describing the early stage of crystallization but was not able to describe the later stage of PF6OC12 crystallization. Also, the Ozawa method failed to describe the nonisothermal crystallization behavior of PF6OC12. However, the method developed by combining the Avrami and Ozawa equations could successfully describe the nonisothermal crystallization kinetics of PF6OC12. According to the Kissinger method, the activation energy was determined to be 114.9 kJ mol^?1 for the nonisothermal melt crystallization of PF6OC12. Copyright © 2006 Society of Chemical Industry     

Nonisothermal crystallization behavior of glass‐bead‐filled polypropylene

The effects of the glass‐bead content and size on the nonisothermal crystallization behavior of polypropylene (PP)/glass‐bead blends were studied with differential scanning calorimetry. The degree of crystallinity decreased with the addition of glass bead, and the crystallization temperature of the blends was marginally higher than that of pure PP at various cooling rates. Furthermore, the half‐time for crystallization decreased with an increase in the glass‐bead content or particle size, implying the nucleating role of the glass beads. The nonisothermal crystallization data were analyzed with the methods of Avrami, Ozawa, and Mo. The validity of various kinetic models for the nonisothermal crystallization process of PP/glass‐bead blends was examined. The approach developed by Mo successfully described the nonisothermal crystallization behavior of PP and PP/glass‐bead blends. Finally, the activation energy for the nonisothermal crystallization of pure PP and PP/glass‐bead blends based on the Kissinger method was evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2026–2033, 2006     

PE/PE‐g‐MAH/Org‐MMT nanocomposites. II. Nonisothermal crystallization kinetics

The nonisothermal crystallization kinetics of high‐density polyethylene (HDPE) and polyethylene (PE)/PE‐grafted maleic anhydride (PE‐g‐MAH)/organic‐montmorillonite (Org‐MMT) nanocomposite were investigated by differential scanning calorimetry (DSC) at various cooling rates. Avrami analysis modified by Jeziorny, Ozawa analysis, and a method developed by Liu well described the nonisothermal crystallization process of these samples. The difference in the exponent n, m, and a between HDPE and the nanocomposite indicated that nucleation mechanism and dimension of spherulite growth of the nanocomposite were different from that of HDPE to some extent. The values of half‐time (t_1/2), K(T), and F(T) showed that the crystallization rate increased with the increase of cooling rates for HDPE and composite, but the crystallization rate of composite was faster than that of HDPE at a given cooling rate. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. It was 223.7 kJ/mol for composite, which was much smaller than that for HDPE (304.6 kJ/mol). Overall, the results indicated that the addition of Org‐MMT and PE‐g‐MAH could accelerate the overall nonisothermal crystallization process of PE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3054–3059, 2004     

Polylactide/nano‐ and micro‐scale silica composite films. II. Melting behavior and cold crystallization

Nonisothermal crystallization of polylactide (PLA)/silica composites prepared by (i) directly blending the PLA with nanoscale colloidal silica sol and by (ii) a sol–gel process are studied by differential scanning calorimeter (DSC) at various heating rates. Samples quenched from the molten state exhibited two melting endotherms (T_ml and T_mh) due to melt‐recrystallization during the DSC scans. Lower heating rate and the presence of silica particles generate a lower peak intensity ratio of T_ml /T_mh. The nonisothermal crystallization kinetics is analyzed by modified Avrami model, Ozawa model, and Liu‐Mo models. The modified Avrami and Liu‐Mo models successfully described the nonisothermal cold crystallization processes, but Ozawa is inapplicable. The nucleation constant (K_g) is calculated by modified Lauritzen‐Hoffman equation and the activation energy by Augis‐Bennett, Kissinger, and Takhor models. These calculated parameters indicate consistently that the nanoscale silica particles seem to form more heterogeneous nucleation to increase crystallization, but microscale one form hindrance to retard crystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

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     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006     

Nonisothermal melt‐crystallization behavior of calcium phosphate/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) nanocomposite microspheres

Microspheres consisting of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) polymer matrix and calcium phosphate (Ca‐P) nanoparticles were made using the solid‐in‐oil‐in‐water (S/O/W) emulsion solvent evaporation technique. Amorphous Ca‐P nanoparticles with the calcium to phosphate ratio of 1.5 were relatively well distributed in microspheres. The nonisothermal crystallization behavior of Ca‐P/PHBV nanocomposite with different Ca‐P contents (0–20%) was studied through differential scanning calorimetry using different cooling rates. During nonisothermal crystallization, the presence of Ca‐P nanoparticles resulted in an increase in crystallization rate and the nucleation activity of the nanocomposite also increased with increasing Ca‐P content. Various models were applied to investigate nonisothermal crystallization kinetics. All approaches, except for the Ozawa model, could successfully describe the nonisothermal crystallization behavior of PHBV and Ca‐P/PHBV nanocomposite. The effective activation energy for nonisothermal crystallization was calculated using the differential isoconversional method proposed by Friedman. The morphology of PHBV spherulites in nanocomposite was also studied using polarized optical microscopy. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

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     

Isothermal and nonisothermal crystallization kinetics of syndiotactic polystyrene/clay nanocomposites

Differential scanning calorimeter (DSC) and X‐ray diffraction methods were used to investigate the isothermal and nonisothermal crystallization behavior and crystalline structure of syndiotactic polystyrene (sPS)/clay nanocomposites. The sPS/clay nanocomposites were prepared by mixing the sPS polymer solution with the organically modified montmorillonite. DSC isothermal results revealed that introducing 5 wt% of clay into the sPS structure causes strongly heterogeneous nucleation, inducing a change of the crystal growth process from mixed three‐dimensional and two‐dimensional crystal growth to two‐dimensional spherulitic growth. The activation energy of sPS drastically decreases with the presence of 0.5 wt% clay and then increases with increasing clay content. The result indicates that the addition of clay into sPS induces the heterogeneous nucleation (a lower ΔE) at lower clay content and then reduces the transportation ability of polymer chains during crystallization processes at higher clay content (a higher ΔE). We studied the non‐isothermal melt‐crystallization kinetics and melting behavior of sPS/clay nanocomposites at various cooling rates. The correlation among crystallization kinetics, melting behavior and crystalline structure of sPS/clay nanocomposites is discussed. Polym. Eng. Sci. 44:2288–2297, 2004. © 2004 Society of Plastics Engineers.     

Morphology,structure, and kinetic analysis of nonisothermal cold‐ and melt‐crystallization of syndiotactic polystyrene

Nonisothermal cold‐ and melt‐crystallization of syndiotactic polystyrene (sPS) were carefully carried out by Perkin–Elmer Diamond differential scanning calorimetry, polarized optical microcopy (POM), and wide angle X‐ray diffraction. The experimental data subjected to the two types of processing were thoroughly analyzed on the basis of Avrami, Tobin, Ziabicki, and combination of Avrami and Ozawa models. Avrami, Tobin, and Ziabicki analyses indicate that nonisothermal cold‐crystallization (A) characterizes smaller Avami and Tobin exponent and larger Ziabicki kinetic crystallizability index G than those obtained from nonisothermal melt‐crystallization (B) possibly due to the existence of partially ordered structures in the quenched samples. Kissinger and the differential isoconversional method (DICM) of Friedman's were utilized to obtain effective energy barrier of A, in good agreement with that obtained by using Arrhenius equation to analyze the isothermal cold‐crystallization, indicating that Kissinger and Friedman equations can be applied to obtain activation energy from A of sPS. X‐ray diffraction analysis indicates that cold‐crystallization mainly produces α‐type crystal but for melt‐crystallization the contents of α‐type and β‐type crystals depend on the cooling rates. The POM also indicates the difference of end morphology of the sample between A and B. At the same time, the DICM of Friedman's was applied to analyze experimental data of B, which were divided into two groups with 20 K/min as the threshold, and it was found that the formation of β‐type crystal possesses larger absolute value of effective activation barrier than the formation of α‐type crystal. © 2006Wiley Periodicals, Inc. J Appl Polym Sci 103: 1311–1324, 2007     

Nonisothermal crystallization kinetics and morphology of self‐seeded syndiotactic 1,2‐polybutadiene

Subsequent melting behavior after isothermal crystallization at different temperatures from the isotropic melt and nonisothermal crystallization kinetics and morphology of partially melting sPB were carried out by differential scanning calorimetry (DSC), polarized light microscopy (POM), respectively. Triple melting‐endothermic peaks were observed for the polymer first isothermally crystallized at temperatures ranging from 141 to 149°C, respectively, and then followed by cooling at 10°C/min to 70°C. Comparing with the nonisothermal crystallization from the isotropic melt, the nonisothermal crystallization for the partially melting sPB characterized the increased onset crystallization temperature, and the sizes of spherulites became smaller and more uniform. The Tobin, Avrami, Ozawa, and the combination of Avrami and Ozawa equations were applied to describe the kinetics of the nonisothermal process. Both of the Tobin and the Avrami crystallization rate parameters (K_T and K_A, respectively) were found to increase with increase in the cooling rate. The parameter F(T) for the combination of Avrami and Ozawa equations increases with increasing relative crystallinity. The Ziabicki's kinetic crytallizability index G_Z for the partially melting sPB was found to be 3.14. The effective energy barrier Δ? describing the nonisothermal crystallization of partially melting sPB was evaluated by the differential isoconversional method of Friedman and was found to increase with an increase in the relative crystallinity. At the same time, Hoffman‐Lauritzen parameters (U and K_g) are evaluated and analyzed from the nonisothermal crystallization data by the combination of isoconversional approach and Hoffman‐Lauritzen theory. The K_g value obtained from DSC technique was found to be in good agreement with that obtained from POM technique. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1479–1491, 2006     

Nonisothermal and isothermal crystallization kinetics of nylon‐12

The isothermal and nonisothermal crystallization behavior of Nylon 12 was investigated using differential scanning calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of Nylon 12, the Avrami exponent (n) determined and its relevance to crystal growth discussed and an activation energy for the process evaluated using an Arrhenius type expression. The Lauritzen and Hoffman analysis was used to examine the spherulitic growth process of the primary crystallization stage of Nylon 12. The surface‐free energy and work of chain folding were calculated using a procedure reported by Hoffmann and the work of chain folding per molecular fold (σ) and chain stiffness of Nylon 12 (q) was calculated and compared to values reported for Nylons 6,6 and 11. The Jeziorny modification of the Avrami analysis, Cazé and Chuah average Avrami parameter methods and Ozawa equation were used in an attempt to model the nonisothermal crystallization kinetics of Nylon 12. A combined Avrami and Ozawa treatment, described by Liu, was used to more accurately model the nonisothermal crystallization kinetics of Nylon 12. The activation energy for nonisothermal crystallization processes was determined using the Kissinger method for Nylon 12 and compared with values reported previously for Nylon 6,6 and Nylon 11. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization kinetics of novel poly(aryl ether ketone) copolymers containing 2,7‐naphthalene moieties

To increase the glass transition temperature (T_g) of poly(aryl ether ketone), and to decrease the melting temperature (T_m) and temperature of processing, a series of novel poly(aryl ether ketone)s with different contents of 2,7‐naphthalene moieties (PANEK) was synthesized. We focused on the influence of the naphthalene contents to the copolymer's crystallization. The crystallization kinetics of the copolymers was studied isothermally and nonisothermally by differential scanning calorimetry. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the crystallization. The study results of the crystallization of PANEK at cooling/heating rates ranging from 5 to 60°C/min under nonisothermal conditions are also reported. Both the Avrami equation and the modified Avrami–Ozawa equation were used to describe the nonisothermal crystallization kinetics of PANEK. The results show that the increase in the crystallization temperature and the content of 2,7‐naphthalene moieties will make the crystallization rate decrease, while the nucleation mechanism and the crystal growth of PANEK are not influenced by the increasing of the content of 2,7‐naphthalene moieties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2527–2536, 2006     

Nonisothermal crystallization kinetics of high‐density polyethylene/barium sulfate nanocomposites

The high‐density polyethylene (HDPE)/barium sulfate (BaSO₄) nanocomposites had been successfully prepared by melt‐blending. Nonisothermal melt‐crystallization kinetics of neat HDPE and HDPE/BaSO₄ nanocomposites was investigated with differential scanning calorimetry under different cooling rates. The nonisothermal crystallization behavior was analyzed by Ozawa, Avrami, and combined Ozawa–Avrami methods. It was found that the Ozawa method failed to describe the nonisothermal crystallization behavior of neat HDPE and HDPE/BaSO₄ nanocomposites. The modified Avrami method by Jeziorny was only valid for describing the middle stage of crystallization but was not able to describe the later stage of neat HDPE and HDPE/BaSO₄ nanocomposites crystallization. The value of Avrami exponent n for neat HDPE ranged from 3.3 to 5.7 and for HDPE/BaSO₄ nanocomposites ranged from 1.8 to 2.5. It is postulated that the values of n close to 3 are caused by spherulitic crystal growth with heterogeneous nucleation, whereas simultaneous occurrence of spherulitic and lamellar crystal growth with heterogeneous nucleation account for lower values of n. The combined Ozawa–Avrami method by Mo and coworkers (Polym. Eng. Sci., 37(3) , 568 (1997)) was able to satisfactorily describe the crystallization behavior of neat HDPE and HDPE/BaSO₄ nanocomposites. In addition, the activation energy of nonisothermal crystallization was determined using the Kissinger (J. Res. Natl. Bur. Stand., 57(4) , 217 (1956)) method, showing that the crystallization activation energy of HDPE/BaSO₄ nanocomposites was lower than that of neat HDPE. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers