Isothermal and Non-Isothermal Crystallization Kinetics of PVDF and PVDF/PMMA Blends

Background: poly(vinylidene fluoride) PVDF and PVDF/PMMA blends have been investigated with a focus on the crystal structure, immiscibility and mechanical properties. However, few reports were found on the crystallization behaviors of PVDF and PVDF/PMMA blends, especially on crystallization kinetics. The article is to report the research on isothermal and nonisothermal crystallization kinetics for PVDF and PVDF/PMMA blends using differential scanning calorimetry (DSC). Results: Besides crystallization temperature and isothermal crystallization activation energy, the Avrami equation exponent of PVDF in blends decreased compared with pure PVDF. The nonisothermal crystallization kinetics of PVDF and PVDF/PMMA (70:30) blends were investigated by Ozawa equation, Jeziorny method and crystallization rate constant (CRC) in detail. The nonisothermal crystallization energy of pure PVDF and its blends were determined by the Kissinger and Vyazovkin’s method. Conclusion: The nucleation and growth mechanism of PVDF in blends changed compared with pure PVDF. The Ozawa equation is not applicable in nonisothermal crystallization kinetics of PVDF and PVDF/PMMA blends. The decreasing of crystallization ability of PVDF in blends were found and confirmed by CRC and the decline of crystallization rate constant in Jeziorny method. Such is opposite to the results of Kissinger’s and Vyazovkin’s method, chances are that these two methods were not used to calculate the nonisothermal crystallization activation energy where the nucleation process was influenced.

Nonisothermal crystallization kinetics, morphology, and tensile properties of polyphenylene sulfide/functionalized graphite nanoplatelets composites

Polyphenylene sulfide (PPS)/graphite nanoplates (GNPs) nanocomposites were manufactured by simple melt compounding. The GNPs were first functionalized using synthesized benzimidazolium salt to improve the compatibility with PPS matrix. The functionalized GNPs showed an exfoliated dispersion in PPS matrix, which also could significantly improve the tensile properties of composites. Differential scanning calorimetry was used to investigate the nonisothermal crystallization kinetics of PPS/functionalized GNPs composites. The results showed that the PPS/functionalized GNPs composites always had a higher crystallization peak temperature ( Tc) than pure PPS resin at different cooling rates due to the addition of GNPs. The GNPs could also play the role of heterogeneous nucleating agents to accelerate the crystallization; however, at high content, they could also limit the mobility of PPS macromolecular chains and hinder the crystallization. The Mo equation could be used to analyze the nonisothermal crystallization kinetics, whereas the Ozawa equation was not suitable for the nonisothermal crystallization process. Consistent with a previous analysis, the results also showed that the addition of GNPs could also decrease the crystallization activation energy ( Ec) of PPS resin at low content while increasing the Ec at high content.

Preparation and Non-Isothermal Kinetics Analysis of N-[(4-Bromo-3,5-Difluorine)Phenyl]acrylamide

N-[(4-bromo-3,5-difluorine) phenyacrylamide was synthesized first time by the interaction of 4-Bromo-3,5-difluoroaniline with acryloyl chloride in presence of triethylamine. The compound behavior was investigated using TG and DSC techniques under non-isothermal linear regime. The non-isothermal kinetic data were analyzed with the Achar equation, Coats-Redfern equation,Kissinger equation, Flynn-Wall-Ozawa equation and Starink equation. The mechanism function and kinetic parameters of the thermal decomposition were obtained. The chemical reaction mechanism (F3) controlled the decomposition process. The apparent activation energy and the pre-exponential factor wereE=240.01 KJmol-1andA=2.341023s-1respectively.

Study on Non-Isothermal Crystallization Kinetics of PBT with High Melt Flow Index

The non-isothermal crystallization process of PBT with high melt flow index has been investigated by DSC, and the nonisothermal crystallization process of PBT with high melt flow index was studied by Ozawa equation and Jeziorny equation respectively. It was found that Ozawa equation, rather than Jeziorny equation, could appropriately be applied to study the non-isothermal crystallization process of PBT with high melt flow index. The Avrami index, obtained by Ozawa equation, varied between 1.06-1.80 with the change in temperature.

The morphology and non-isothermal crystallization kinetics of PET/BaSO4 hybrid fibre

The addition of BaSO4 whose mass fraction was less than 0.052%, could improve the mechanical property and thermal stability of the fibre apparently. It was found that, the smoothness of the hybrid fibre was changed by BaSO4 appreciably, though allowable in actual production; The BaSO4 did not obviously affect the crystallization index ( a ) and the relative degree of crystallization. With the content of BaSO4 increasing, the crystallization rate firstly became smaller slightly and then restored to the original level at the primary crystallization stage, but the crystallization rate revealed a small fluctuation at the secondary crystallization stage. In addition, the Ozawa equation was fit for pure PET well, and the Mo equation was fit for pure and hybrid PET.

Synthesis of Three Novel Aromatic Biazomethine Liquid- Crystalline Epoxy Resins and Curing Reaction with Aromatic Diamine

Three class of novel liquid crystalline epoxy resins containing azomething groups: N,N’-Bis[4-(2,3-epoxypropoxy)benzylidene]-4,4-diamino-diphenyl ether (p-BEPBDDE), N,N’-Bis[4-(2,3-epoxypropoxy)benzylidene]-4,4-diamino-diphenyl methane (p-BEPBDDM) and N,N’-Bis[(4-(2,3-epoxypropoxy)-benzyliden)-1,4- phenylene diamine] (p-BEPBPD) were synthesized and characterized. The results show that p-BEBDDE and p-BEBDDM belong to smectic texture and melting point is 239.5 and 178 oC, respectively. The p-BEPBD is nematic texture between its melting temperature (Tm) of 192 oC and clearing temperature (Ti) of 238 oC. The curing reaction can be described by Ozawa equation, and the alcohol-hydroxyl group can accelerate the curing reaction and decrease Ea in DSC experiment.

Non-isothermal crystallization kinetics of Poly(phenylene sulfide)/hyperbrtanched Poly(phenylene sulfide) blends

The non-isothermal crystallization behaviour of poly(phenylene sulfide) (PPS) in blends with hyperbranched poly(phenylene sulfide) (HPPS) was studied by means of differential scanning calorimetry (DSC). It was observed that the PPS crystallization temperature was found to decrease upon addition of the HPPS. It suggested that the crystallizability was reduced. The Ozawa equation was valid not only for neat PPS, but also for the blends. A notable reduction in Avrami exponents for the PPS/HPPS blend systems suggested that the nucleated process leads to rodshaped growth with thermal nucleation. The cooling crystallization function, which represents the rate of non-isothermal crystallization, was found to decrease with increase in HPPS content. The Ea value increases with the increase in HPPS content. Our results indicated that crystallization of the PPS was hampered by content of hyperbranched poly(phenylene sulfide).

The Kinetic Analysis of Thermal Decomposition of PMMA/MMT Nanocomposites

The thermal decomposition kinetics and thermal stability of poly (methyl methacrylate) (PMMA) and PMMA/ montmorillonite (MMT) nanocomposites containing 4 wt% MMT were researched by thermogravimetry (TG). The results show that, because of the barrier behavior of exfoliated MMT layer, the temperature of thermal decomposition of PMMA/ MMT nanocomposites is improved by about 10 °C, and thermal stability is improved by about double. The apparent activation energy of decomposition, calculated by Ozawa equation, of nanocomposites is higher than that of PMMA before 27 % mass loss.