Crystallization behavior and isothermal crystallization kinetics of polylactide/polystyrene-b-polybutadiene-b-polystyrene blends compatibilized with poly(styrene-ran-methyl acrylate)

The morphology, non-isothermal and isothermal crystallization behavior, and spherulite growth of polylactide (PLA)/polystyrene-b-polybutadiene-b-polystyrene (SBS) blends were investigated in the presence of a poly(styrene-ran-methyl acrylate) (S–MA) compatibilizer synthesized using surfactant-free emulsion copolymerization. Scanning electron microscopy revealed that the SBS dispersed-phase became more uniform and refined as the amount of S–MA compatibilizer was increased from 0 to 3 wt%. Calorimetric characterization of the non-isothermal and isothermal crystallization behavior analyzed using Avrami theory shows that the SBS in PLA shows plasticization and dilution effects simultaneously. When the PLA matrix chains do not move easily and/or its effective crystallization time window is narrow, the plasticization effect of the SBS is more significant. However, when the PLA matrix chains move more easily and/or its crsytallization window is wide, the dilution effects effect of the SBS is more notable. After the addition of S–MA, the plasticization and dilution effects were enhanced.     

Crystallization and melting properties of poly(butylene succinate) composites with titanium dioxide nanotubes or hydroxyapatite nanorods

Poly (butylene succinate) (PBS) nanocomposites with titanium dioxide nanotubes (TNTs) or hydroxyapatite nanorods (HAP) were prepared, and the effect of the nano‐inorganics on the nonisothermal crystallization and melting properties of PBS were studied in detail by differential scanning calorimeter. The nonisothermal crystallization kinetics of PBS and its nanocomposites were analyzed by the Avrami, Ozawa, and Mo methods. It is found that the presence of TNTs increases the crystallization temperature and rate of PBS composites, but decreases the crystallization activation energy and crystallinity. By comparison, the crystallization rate of the PBS composite is decreased with the addition of HAP. The melting, recrystallization, and remelting mechanism results in the formation of two melting endothermic peaks during the melting process of neat PBS and its nanocomposites. The model proposed by Mo could successfully describe the nonisothermal crystallization process of PBS and its nanocomposites. At a given crystallinity, the F(t) values decrease in the order of PBS/HAP, PBS, and PBS/TNTs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40335.     

Crystallization kinetics of poly(ethylene terephthalate) with thermotropic liquid crystalline polymer blends

The isothermal and dynamic crystallization behaviors of polyethylene terephthalate (PET) blended with three types of liquid crystal polymers, i.e., PHB60–PET40, HBA73–HNA27, [(PHB60–PET40)–(HBA73–HNA27) 50 : 50], have been studied using differential scanning calorimetry (DSC). The kinetics were calculated using the slope of the crystallization versus time plot, the time for 50% reduced crystallinity, the time to attain maximum rate of crystallization, and the Avrami equation. All the liquid crystalline polymer reinforcements with 10 wt % added accelerated the rate of crystallization of PET; however, the order of the acceleration effect among the liquid crystalline polymers could not be defined from the isothermal crystallization kinetics. The order of the effect for liquid crystalline polymer on the crystallization of PET is as follows: (PHB60–PET40)–(HBA73–HNA27) (50 : 50); HBA73–HNA27; PHB60–PET40: This order forms the dynamic scan of the DSC measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1383–1392, 1998     

Non‐isothermal crystallization kinetics of cork‐polymer composites for injection molding

The non‐isothermal crystallization behavior of cork–polymer composites (CPC) based on polypropylene (PP) matrix was studied. Using differential scanning calorimetry (DSC), the crystallization behavior of CPC with 15 wt % cork powder at different cooling rates (5, 10, 15, and 20 °C/min) was studied. The effect of a coupling agent based on maleic anhydride was also analyzed. A composite (PPg) containing polypropylene grafted maleic anhydride (PPgMA) and PP was prepared for comparison purposes. Crystallization kinetic behavior was studied by Avrami, Ozawa, Liu, and Kissinger methods. The Ozawa method fails to describe the behavior of these composites. Results show that cork powder surface acts as a nucleating agent during non‐isothermal crystallization, while the addition of PPgMA decreases the crystallization rate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44124.     

PA1212的结晶动力学研究

采用DSC方法研究了PA1212的非等温和等温结晶动力学。Avrami方程可以适用PA1212的等温结晶过程,其Avrami指数为2．51～2．87,等温结晶活化能为-131．9 kJ/mol;在非等温结晶过程中,结晶速率随降温速率的增大而提高,综合利用Avrami方程和Ozawa方程得到Avrami指数与Ozawa指数的比值为1．31～1．49,非等温结晶活化能为-87．96 kJ/mol。结果表明,与其他聚酰胺相比,PA1212较容易结晶。     

Crystallization properties of polycaprolactone composites filled with nanometer calcium carbonate

Polycaprolactone (PCL) composites filled with nanometer calcium carbonate (nano‐CaCO₃) were prepared by means of a twin‐screw extruder in this study. The nano‐CaCO₃ surface treated with stearate. The crystalline properties of the PCL/nano‐CaCO₃ composites were measured with a differential scanning calorimeter to identify the influence of the nanometer filler content on the crystalline properties. The results show that the crystallization onset temperature, crystallization temperature, and crystallization end temperature of the composites were obviously higher than those of the unfilled PCL resin, and the crystallization degree (χ_c) of the composites increased with increasing particle weight fraction (?_f) when ?_f was more than 1%. When ?_f was 1%, χ_c of the composite was less than that of the unfilled PCL resin. Moreover, the dispersion of the inclusions in the matrix was observed by means of scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

Isothermal crystallization kinetics of high‐flow nylon 6 by differential scanning calorimetry

The isothermal crystallization kinetics have been investigated with differential scanning calorimetry for high‐flow nylon 6, which was prepared with the mother salt of polyamidoamine dendrimers and p‐phthalic acid, an end‐capping agent, and ε‐caprolactam by in situ polymerization. The Avrami equation has been adopted to study the crystallization kinetics. In comparison with pure nylon 6, the high‐flow nylon 6 has a lower crystallization rate, which varies with the generation and content of polyamidoamine units in the nylon 6 matrix. The traditional analysis indicates that the values of the Avrami parameters calculated from the half‐time of crystallization might be more in agreement with the actual crystallization mechanism than the parameters determined from the Avrami plots. The Avrami exponents of the high‐flow nylon 6 range from 2.1 to 2.4, and this means that the crystallization of the high‐flow nylon 6 is a two‐dimensional growth process. The activation energies of the high‐flow nylon 6, which were determined by the Arrhenius method, range from ?293 to ?382 kJ/mol. The activation energies decrease with the increase in the generation of polyamidoamine units but increase with the increase in the content of polyamidoamine units in the nylon 6 matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crystallization behavior and isothermal crystallization kinetics of PLLA blended with ionic liquid, 1‐butyl‐3‐methylimidazolium dibutylphosphate

The crystallization behavior and isothermal crystallization kinetics of neat poly(l ‐lactic acid) (PLLA) and PLLA blended with ionic liquid (IL), 1‐butyl‐3‐methylimidazolium dibutylphosphate, were researched by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X‐ray diffraction (WXRD). Similar to the non‐isothermal crystallization behavior of neat PLLA, when PLLA melt was cooled from 200 to 20°C at a cooling rate of 10°C min^?1, no crystallization peak was detected yet with the incorporation of IL. However, the glass transition temperature and cold crystallization temperature of PLLA gradually decreased with the increase of IL content. It can be attributed to the significant plasticizing effect of IL, which improved the chain mobility and cold crystallization ability of PLLA. Isothermal crystallization kinetics was also analyzed by DSC and described by Avrami equation. For neat PLLA and IL/PLLA blends, the Avrami exponent n was almost in the range of 2.5–3.0. It is found that t_1/2 reduced largely, and the crystallization rate constant k increased exponentially with the incorporation of IL. These results show that the IL could accelerate the overall crystallization rate of PLLA due to its plasticizing effect. In addition, the dependences of crystallization rate on crystallization temperature and IL content were discussed in detail according to the results obtained by DSC and POM measurements. It was verified by WXRD that the addition of IL could not change the crystal structure of PLLA matrix. All samples isothermally crystallized at 100°C formed the α‐form crystal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41308.     

Isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide)

The isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide) (PA‐10T) was studied by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization process. The commonly used Avrami equation and the one modified by Jeziorny were used, respectively, to describe the primary stage of isothermal and nonisothermal crystallization. The Avrami exponent n was evaluated to be in the range of 2.36–2.67 for isothermal crystallization, and of 3.05–5.34 for nonisothermal crystallization. The Ozawa analysis failed to describe the nonisothermal crystallization behavior, whereas the Mo–Liu equation, a combination equation of Avrami and Ozawa formulas, successfully described the nonisothermal crystallization kinetics. In addition, the value of crystallization rate coefficient under nonisothermal crystallization conditions was calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 819–826, 2004     

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     

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     

Curing kinetics and curing process of phenolic impregnated carbon ablator

Phenolic impregnated carbon ablator (PICA), which is composed of the phenolic resin (PR) and carbon fiber, is of particular interest to researchers in the aerospace field. In this work, PICA was prepared by the double‐stage isothermal heating curing. Then, the curing kinetics of boron‐modified phenolic resin (BPR) was investigated by non‐isothermal differential scanning calorimetry method in order to optimize the curing temperature of BPR. Further, the effect of the heating rate during curing process on the compressive strength of PICA was discussed in detail. The experimental data show that the curing of BPR needs more energy so that the curing temperature of BPR under different condition is higher than that of virgin PR. Notably, with the increasing heating rate during the curing process, the micro‐cracks increase and the compressive strength of PICA decreases. Once the heating rate exceeds a critical value, the micro‐cracks no longer increase and the heating rate has insignificant effect on the compressive strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45434.     

Curing studies of bisphenol a based bismaleimide and cloisite 15a nanoclay blends using differential scanning calorimetry and model‐free kinetics

Blends of 2,2‐bis[4‐(4‐maleimidophenoxy phenyl)]propane [bismaleimide (BMIX)] with different proportions (1, 2, 3, 4, 5, 7, and 9%) of the nanoclay Cloisite 15a were prepared with ultrasonication. Fourier transform infrared studies reveal the existence of interactions between the clay particles and the imide rings in BMIX. The difference in the melting characteristics and the decrease in the curing window caused by the incorporation of the clay particles in BMIX, as evidenced by detailed differential scanning calorimetry investigations, confirmed the existence of interactions between the nanoclay particles and BMIX molecules. The Flynn–Wall–Ozawa, Vyazovkin, and Friedman kinetics methods were used to calculate the activation energies (E_a's) for the curing of the BMIX materials. E_a for the polymerization varied, depending not only on the amount of clay loaded in the BMIX but also on the extent of the curing reaction. Because of the loss of interaction between the clay platelets and the imide rings of BMIX, a decrease in E_a at higher reaction extents was noted when there was lower clay loadings (1–4% Cloisite 15a) in BMIX. A reversal in the previous behavior was noted at higher clay loadings (7 and 9% Cloisite 15a) in BMIX and was attributed to the restriction of the molecular mobility due to the presence of increased concentrations of clay platelets and the decreased availability of reaction sites for polymerization. These two opposing factors played were equal at the optimum level of Cloisite 15a loading (5%) in BMIX, which was reflected in the constancy of E_a variation noted with increasing reaction extent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A combined differential scanning calorimetry-dynamic mechanical thermal analysis approach for the estimation of constrained phases in thermoplastic polymer nanocomposites

Poly(butylene terephthalate) (PBT) nanocomposites reinforced with different weight fractions of montmorillonite (MMT), and nanoprecipitated calcium carbonate (NPCC) were prepared by a two-step melt compounding method. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses were employed to explore the effect of nanofiller inclusion on the crystalline structure of PBT nanocomposites. The mobile amorphous fraction (MAF) and the rigid amorphous fraction (RAF) were first measured using the specific heat capacity (C_p ) and melting enthalpy data. However, the contributors to total RAF, including interfacial RAF (RAF_int ) and crystalline RAF (RAF_c ), could not be discerned using only DSC. A novel and simple method was hence developed by employing a combined DSC-dynamic mechanical thermal analysis (DMTA) approach (CDDA) to disentangle the RAF components and determine the fractions of constrained volume constituents. To validate the results, the MAF calculated by CDDA were compared to those of DSC. The values obtained using CDDA were relatively higher, owing to the more significant sensitivity of this approach to polymer chain mobility.     

Isothermal crystallization kinetics of polypropylene by differential scanning calorimetry. I. Experimental conditions

Reliable isothermal crystallization kinetic studies can be achieved by differential scanning calorimetric techniques only under restricted conditions. In the case of isotactic polypropylene, our results indicate that those conditions are met in the range of 3°C below the isothermal crystallization temperature T_c. Experimentally, it is only in this range when the complete crystallization peak can be registered by the DSC and depicted in a thermogram. Just around this temperature interval, the Avrami exponent n = 3 for bulk crystallization, whereas for any other test the isothermal temperature T_it, nonisothermal conditions prevail and the Avrami exponent deviates from the expected value. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 970–978, 2004     

Crystallization and melting behavior of trans‐1,2‐syndiotactic polypentadiene

(E)‐1,3‐pentadiene was polymerized at ?30°C by using the catalyst system CoCl₂(PⁱPrPh₂)²–MAO. A trans‐1,2‐syndiotactic structure was attributed to the semicrystalline polymer obtained on the basis of the characterization carried out by FTIR, NMR, and WAXD techniques. The thermal behavior of the polypentadiene was investigated by thermogravimetry and differential scanning calorimetry. Isothermal melt crystallization kinetics were analyzed according to the Avrami equation. Nonisothermal crystallization kinetics were elaborated by using Ziabicki and Avrami methods modified by Jeziorny. The equilibrium melting temperature was calculated. The thermal behavior of trans‐1,2‐syndiotactic polypentadiene was compared with that of 1,2‐syndiotactic polybutadiene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1970–1976, 2005