Mo Equation Research Articles

Crystallization Behavior of Copolyesters Containing Sulfonates.

The polar sulfonate groups in cationic dyeable polyester (CDP) lead to complex crystallization behavior, affecting CDP production's stability. In this study, cationic dyeable polyesters (CDP) with different sulfonate group contents were prepared via one-step feeding of sodium isophthalic acid-5-sulfonate (SIPA), terephthalic acid (PTA), and ethylene glycol (EG). The non-isothermal crystallization behavior of these copolyesters was analyzed by differential scanning calorimetry (DSC). Results show that the crystallization temperature of the sample shifts to lower values with the increase in SIPA content. The relaxation behavior of the molecular chain is enhanced due to the ionic aggregation effect of sulfonate groups in CDP. Therefore, at low cooling rates (2.5 °C/min and 5 °C/min), some molecular chain segments in CDP are still too late to orderly stack into the lattice, forming metastable crystals, and melting double peaks appear on the melting curve after crystallization. When the cooling rate increases (10-20 °C/min), the limited region of sulfonate aggregation in CDP increases, resulting in more random chain segments, and a cold crystallization peak appears on the melting curve after crystallization. The non-isothermal crystallization behavior of all samples was fitted and analyzed by the Jeziorny equation, Ozawa equation, and Mo equation. The results indicate that the nucleation density and nucleation growth rate of CDP decrease with the increase in SIPA content. Meanwhile, analysis of the Kissinger equation reveals that the activation energy of non-isothermal crystallization decreases gradually with the increase in SIPA content, and the addition of SIPA makes CDP crystallization more difficult.

Accelerated nonisothermal crystallization and improved material properties of biobased poly(butylene 2,5-furandicarboxylate)/talc composites

Biobased poly(butylene 2,5-furandicarboxylate) (PBF) reflects the much poorer crystallizability than its petroleum-based counterpart poly(butylene terephthalate). By introducing talc platelets into PBF matrix to fabricate composites, the effects of low loadings’ layered filler upon nonisothermal melt crystallization and material properties of PBF/talc composites are investigated for the first time. Obviously accelerated crystallization of the composites relative to pure PBF is first evidenced by the simultaneous increase of crystallization temperature and decline of crystallization half-time, and further supported by both the crystallization rate coefficient and crystallization rate parameter. Nonisothermal crystallization kinetics are analyzed by both the Jeziorny model and Mo equations, and the intensifying effect of talc upon PBF's crystallization is attributed to the coupling of enlarging nucleation activity and lowering crystallization activation energy. Meanwhile, the incorporation of layered talc doesn't modify the crystal structure of PBF. Moreover, both the thermal and mechanical properties of PBF/talc composites are reinforced slightly.

Mechanical Properties and Non-Isothermal Crystallization Kinetics of Polylactic Acid Modified by Polyacrylic Elastomers and Cellulose Nanocrystals.

In this paper, a polyacrylic elastomer latex with butyl acrylate (BA) as the core and methyl methacrylate (MMA) copolymerized with glycidyl methacrylate (GMA) as the shell, named poly(BA-MMA-GMA) (PBMG), was synthesized by seeded emulsion polymerization. Cellulose nanocrystal (CNC) was dispersed in the polyacrylic latex to prepare PBMG/CNC dispersions with different CNC contents. The dried product was mixed with polylactic acid (PLA) to fabricate PLA/PBMG/CNC blends. The addition of PBMG and PBMG/CNC improved the mechanical properties of the PLA matrix. Differential scanning calorimetry (DSC) was used to investigate the non-isothermal crystallization kinetics. The Avrami equation modified by the Jeziorny, Ozawa and Mo equations was used to analyze the non-isothermal crystallization kinetics of PLA and its blends. Analysis of the crystallization halftime of non-isothermal conditions indicated that the overall rate of crystallization increased significantly at 1 wt% content of CNC. This seemed to result from the increase of nucleation density and the acceleration of segment movement in the presence of the CNC component. This phenomenon was verified by polarizing microscope observation.

Non-isothermal crystallization kinetics of ethylene-tetrafluoroethylene copolymer using integral Avrami equation

Abstract The non-isothermal crystallization kinetics of ethylene-tetrafluoroethylene copolymer (ETFE, Fluon®C-88AXP) was studied by using differential scanning calorimetry (DSC). The Jeziorny, Ozawa, Mo, and Kissinger equations have been used to describe the crystallization data. The Ozawa and Kissinger plots show downward curves instead of the linear relationship as predicted. Good linear relationship was obtained using the Jeziorny and Mo equations but no vital model parameters concerned with the crystallization kinetics could be acquired. The integral Avrami equation combining with Hoffman equation has been used to describe the crystallization data through nonlinear regression method and kinetic parameters have been acquired. The fitting quality improves when the thermal lag effect was taken into consideration. Meanwhile, the linearity of the Ozawa and Kissinger analysis is improved greatly and the Ozawa exponent and crystallization activity energy of the copolymer have been obtained.

Non-Isothermal Crystallization Kinetics of Polyvinylidene Fluoride (PVDF)/Microcrystalline Graphite (MCG) Composites

The Avrami equation modified by Jeziorny, the Ozawa model and the Mo equation combining the Avrami and Ozawa theories were employed to describe the non-isothermal crystallization kinetics of poly(vinylidene fluoride) (PVDF), and PVDF/microcrystalline graphite (MCG) composites. It was found that the Ozawa model failed to describe the non-isothermal crystallization process for PVDF and its composites, while Mo’s theory provided good fitting for neat PVDF but did not describe the non-isothermal crystallization well for the PVDF/MCG composites. The addition of MCG promoted the crystallization rate of PVDF, which indicates that MCG acted as a nucleating agent. The absolute values of the effective activation energy of the PVDF/MCG composites calculated by the Kissinger equation, were higher than that of neat PVDF, confirming that MCG acted as a nucleating agent and promoted the crystallization rate of PVDF.

Thermo-mechanical efficiency of fibre-reinforced structural lightweight aggregate concrete

The construction industry must consider not only the mechanical performances of structural materials but also their thermal performances for energy-efficient buildings. There exist conflicting thermal and mechanical properties between normal weight concrete (NWC) and lightweight aggregate concrete (LWAC). NWC with high mechanical strength exhibits poor thermal efficiency but LWAC possesses low mechanical strengths but high thermal efficiency. The inclusion of fibres in the mixture of LWAC could provide a solution to its weaknesses in mechanical properties however its thermal performance was not well fully understood. To produce an energy-efficient building material, this study was conducted to determine thermo-mechanical performances of steel (ST) and polypropylene (PP) fibre-reinforced LWACs that meet the structural code requirements with good thermal properties. Lightweight expanded clay aggregate was used to make a structural LWAC and polypropylene and steel fibres were used as the reinforcement. Test results revealed that structural LWAC reinforced ST fibre with 1.0% dosage has the best mechanical and thermo-mechanical efficiency whilst PP fibre with 0.3% dosage has the best thermal performance.The ST fibre has a positive influence on the compressive and tensile strength than PP fibre. In terms of overall thermal performance and cost, LWAC containing 0.3% PP fibre was the most desirable. The PP fibre has a more positive influence on thermal properties than ST fibre. The equations had been proposed with a good correlation of R2 > 0.7979 to predict the thermal properties against density for ST and PP fibres. The new merit Mo equation provides a novel way to measure the thermo-mechanical efficiency of the building materials for the construction industry. ST fibre is better than PP fibre in enhancing the mechanical efficiency but PP fibre is more efficient than ST in enhancing the thermal efficiency of fibre-reinforced LWAC.

Non-isothermal crystallization kinetics of graphene/PA10T composites

Crystallization kinetics is the key factor in controlling the polymer crystallization process and affecting crystallinity and crystalline morphology, which determine the polymer's main properties. In this work, the non-isothermal crystallization kinetics of graphene/PA10T composites are investigated by the Jeziorny method and Mo method, and the crystallization activation energy is calculated by the Kissinger method. It is found that the addition of an appropriate amount of graphene to PA10T can significantly promote the crystallization of PA10T and accelerate its crystallization rate. The Jeziorny equation does not have a linear relationship across the whole crystallization range, while the Mo equation does a good linear fitting. In addition, the crystallization activation energy decreases when the graphene content is below 1 wt.%. TGA results indicate that the addition of graphene improves the thermal stability of PA10T.

Non-isothermal Crystallization Kinetics Behavior of Pure Low-density Polyethylene and Low-density Polyethylene/Styrene-butadiene Rubber Thermoplastic Vulcanizates

Low-density polyethylene (LDPE)/styrene-butadiene rubber (SBR) thermoplastic vulcanizates (TPV) were prepared by dynamic vulcanization, and the non-isothermal crystallization kinetics of the LDPE/SBR TPV and pure LDPE were investigated by differential scanning calorimetry (DSC), and the crystallization processes of LDPE/SBR TPV and pure LDPE were depicted by the Avrami, Ozawa and Mo equation models. The findings indicated that the crystallization behavior of both LDPE/SBR TPV and pure LDPE can be described by the Mo model and Avrami model modified by the Jeziorny correction, while the Ozawa model was not applicable to describe the behavior. Kinetic data analysis showed that LDPE/SBR TPV had higher crystallization onset temperature (T0), peak crystallization temperature (Tp), and more stable crystallinity compared to pure LDPE at the same cooling rate.

Non-isothermal crystallization kinetics of wood powder/low melting point polyamide 6 composites

The polyamide 6 (PA6) modified by LiCl was compounded with wood powder in the molten state to prepare wood powder/low melting point PA6 composites. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites was investigated via DSC. The results show that LiCl reduces the melting point, crystallization temperature, crystallinity and crystallization rate of PA6, while increases the crystallization activation energy. As a nucleating agent, the wood powder increases the crystallization rate of PA6, but decreases the crystallinity. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites were analyzed by Mo equation. The results show that F(T) value (the parameters of crystallization rate) of the low melting point PA6 is higher than that of pure PA6 and the wood powder/PA6 composites. LiCl increases the cooling rate required for PA6 to reach a relative crystallinity in unit time. On the contrary, wood powder reduces the cooling rate.

Non-isothermal crystallization kinetics of polypropylene/polytetrafluoroethylene fibrillated composites

Non-isothermal crystallization kinetics of polypropylene (PP)/polytetrafluoroethylene (PTFE) fibrillated composites is presented. In-situ fibrillated PP/PTFE-composites containing 1 and 3 wt% PTFE were prepared by melt compounding using a twin-screw extruder. The morphology and non-isothermal crystallization behavior of the composites were examined using scanning electron microscopy and differential scanning calorimetry, respectively. The Mo equation was used to analyze the kinetics of non-isothermal crystallization behavior. The PTFE created a three-dimensional (3-D) network. A low PTFE content promoted crystallization through fast nucleation, whereas a high PTFE content decreased the crystallization kinetics through hindering the crystal growth. These findings are all based on the Mo equation analysis. The activation energy and nucleation activity were also evaluated, and the way in which the PTFE nanofibers affected the crystallization was discussed in detail. Polarized optical microscopy images revealed that the size of PP spherulites decreased with the increase of PTFE content. Finally, the effect of PTFE on the crystalline phase of PP was investigated by wide angle X-ray diffraction.

Nonisothermal crystallization behaviors of ethylene–acrylic acid copolymer and ethylene–acrylic acid copolymer/chloroprene rubber thermoplastic vulcanizate

Nonisothermal crystallization kinetics of ethylene–acrylic acid copolymer (EAA) and thermoplastic vulcanizate (TPV) based on EAA/chloroprene rubber (CR) were extensively studied using differential scanning calorimetry. Several methods, including the Avrami, Ozawa, and Mo equations, were carried out to analyze the process of nonisothermal crystallization kinetics of EAA and EAA/CR TPV. The results showed that the Avrami analysis modified by Jeziorny and a method developed by Mo could describe the nonisothermal crystallizations of pure EAA and the EAA/CR TPV very well. However, the Ozawa analysis did not give an adequate description. The crystallization processes of pure EAA and the EAA/CR TPV were accelerated by increasing the cooling rates. Moreover, the initial crystallization temperature and the crystallization termination temperature of EAA/CR TPV were higher than those of pure EAA at the same cooling rate, thus showing the nucleating function of CR in the beginning. While the crystallization half time of EAA/CR TPV was apparently longer than that of pure EAA, meaning that the more CR could cause the steric effect and retard the crystallization process of the TPV during the late stages of crystallizing. Although the CR phase of EAA/CR TPV could provide more nucleation sites, the presence of more CR phase must impose a much more significant confinement effect on the crystal growth of EAA. It was believed that this confinement effect overweighed the nucleation effect, thereby slowing down the overall crystallization rate.

Structure-properties correlations in poly(ε-caprolactone)/poly(styrene-co-acrylonitrile)/nanosilica mixtures: Interrelationship among phase behavior, morphology and non-isothermal crystallization kinetics

In this work, the effects of amorphous poly(styrene-co-acrylonitrile) (SAN) chains and hydrophilic and hydrophobic nanosilica at different loadings on the non-isothermal crystallization kinetics of PCL phase have been evaluated using different theoretical models including Avrami, modified Avrami, Ozawa and Mo equations. Using microscopic observations, the interrelations among the changes in the kinetics parameters and the morphology and phase behavior of PCL/SAN and PCL/SAN/nanosilica mixtures have been thoroughly investigated. Microscopic observations on the nanocomposites showed differences in the nanofiller dispersion and distribution state as well as preferential migration and localization state. These differences lead to contradictory trends in the effects of hydrophilic and hydrophobic nanosilica on the crystallization kinetics of pure PCL and PCL/SAN blends. The nanoparticle migration during non-isothermal DSC tests in PCL/SAN blends, the formation of nanoparticle agglomerates at higher loadings, the restrictions imposed on the molecular movements in the crystallization growth stage and slower phase separation and dissolution of PCL/SAN/silica mixtures result in the cooling rate dependence of the kinetics parameters.

Nonisothermal crystallization behavior of polylactide/polyethylene glycol/graphene oxide nanosheets composite films

AbstractThe nonisothermal crystallization (NIC) behavior of solution‐cast polylactide (PLA)/polyethylene glycol (PEG)/graphene oxide (GO) nanosheets composite (PLA/PEG/GO) films was examined at the selected cooling rate. The crystallization temperature (Tc) of the PLA/PEG matrix improved with increasing the reinforcement of GO (0.5%‐2% w/w) at a constant cooling rate. Various conventional crystallization models, namely, Jeziorny, Ozawa, and Mo were employed to elucidate the NIC kinetics of the PLA/PEG/GO composite films. Results showed that the Mo equation was the best model to describe the NIC of the nanocomposite films. The activation energy (E) of crystallization was estimated by Friedman's method, and the values varied from 18 to 186 kJ·mol−1, however, the values were not systematic with the loading concentration of GO.

Molecular dynamics and cold crystallization process in a liquid-crystalline substance with para-, ferro- and antiferro-electric phases as studied by dielectric spectroscopy and scanning calorimetry

In this article, molecular dynamics and the cold crystallization kinetics of 4-(6-heptafluorobutanoiloxyhexyloxy)biphenyl-4′-carboxylan(S)-4-(1-methyloheptyloxycarbonyl) phenyl (abbreviated as 3F6Bi and/or 4H6) are presented. Rich polymorphism of the liquid-crystalline (SmA*, SmC*, SmC*A and SmI*A) phases and partially disordered crystal CrI and glassy GCrI were observed upon cooling. Both, molecular and collective relaxation processes were observed in the para-, ferro- and antiferro-electric liquid-crystalline phases over the frequency range of 3 × 10−2 to 3 × 106 Hz. An additional bias field in the dielectric experiments was used to identify individual processes. The high heating rates (5–10 K/min) phase sequence is the same as in case of the cooling experiment. On slow heating (0.5–2 K/min), cold crystallization of SmI*A to the more stable crystal CrII phase was observed in the dielectric and calorimetric experiments. The crystallization kinetics was analyzed using the Mo equation, which is a combination of the Avrami and Ozawa models. The activation energy of crystallization was calculated to be 138 and 99 kJ/mol using the Kissinger and Augis-Bennett models, respectively.

Effect of substituting Na2O for SiO2 on the non-isothermal crystallization behavior of CaO-BaO-Al2O3 based mold fluxes for casting high Al steels

The non-isothermal crystallization behaviors of CaO-BaO-Al2O3-based mold fluxes in which SiO2 had been replaced by Na2O were investigated, using an infrared furnace combined with digital microscopy as well as X-ray diffraction. The initial crystallization temperatures, crystalline phases generated at different cooling rates, crystallization rates, Ozawa indices NO (as determined using Mo's equation) and effective crystallization activation energies (as determined using the Friedman equation) were evaluated. The initial crystallization temperature increased along with the Na2O content in the flux. In addition, the precipitation of CaF2 crystals was inhibited while the growth of CaAl2O4 crystals was enhanced at Na2O concentrations over 4 wt%. Increasing the cooling rate inhibited the precipitation of MgAl6O10, and of CaSiO3, MgAl2SiO6 and NaAlSi3O8, respectively, in fluxes containing 0, 4 and 8 wt% Na2O (NS1, NS2 and NS3 samples). The peak instantaneous and average crystallization rates in these specimens were increased as the Na2O level was raised, as a direct result of changes in their NO values. The NS1 flux consistently had the lowest NO value, while the NS2 had the largest value in the primary stage of crystallization but the central value in the secondary stage, and the NO values of the NS3 flux exhibited the opposite trend. The effective crystallization activation energies decreased with increasing Na2O levels, and this was evidently an important factor affecting the initial crystallization temperature.

The non-isothermal crystallization behavior of polyamide 6 and polyamide 6/HDPE/MAH/L-101 composites

Abstract Study of the crystallization kinetics is particularly necessary for the analysis and design of processing operations, especially the non-isothermal crystallization behavior, which is due to the fact that most practical processing techniques are carried out under non-isothermal conditions. The non-isothermal crystallization behaviors of polyamide 6 (PA6) and PA6/high-density polyethylene/maleic anhydride/2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (PA6/HDPE/MAH/L-101) composites were investigated by differential scanning calorimetry (DSC). The crystallization kinetics under non-isothermal condition was analyzed by the Jeziorny and Mo equations, and the activation energy was determined by the Kissinger and Takhor methods. The crystal structure and morphology were analyzed by wide-angle X-ray diffraction (WXRD) and polarized optical microscopy (POM). The results indicate that PA6/HDPE/MAH/L-101 has higher crystallization temperature and crystallization rate, which is explained as due to its heterogeneous nuclei.

Morphological structure, impact toughness, thermal property and kinetic analysis on the cold crystallization of poly (lactic acid) bio-composites toughened by precipitated barium sulfate

The bio-composites of poly (lactic acid) (PLA) involving a varied mass fraction of precipitated barium sulfate (BaSO4) were prepared via melt-compounding and subsequent injection molding. The morphologies, impact toughness and thermal properties of the composites were investigated carefully, and the toughening mechanism was emphasized by a combination of BaSO4 content and the crystallization ability. Results showed that an adequate amount of BaSO4 could disperse homogeneously in PLA matrix with well-bonded interfaces. The impact toughness was increased significantly by 52.7% due to added inorganic particles as well as the increased actual crystallinity of the composites. The added BaSO4 let the cold crystallization occur earlier (shifting to low temperature) while suppressing the cold crystallinity of PLA phase. Such inhibition effects derived from the increased inorganic filler were then further explored and confirmed by the kinetic analysis on the cold crystallization under non-isothermal conditions. Indeed, the added BaSO4 increased the crystallization half-time and crystallization parameter of F(T) based on Mo equation. Moreover, the activation energy on cold crystallization was strengthened along with the increasing BaSO4. It seemed that there is little change in the reaction order of PLA/BaSO4 bio-composites, following the unique reaction thermal decomposition, whereas the activation energies were decreased steadily based on Carrasco method.

Crystallization and mechanical properties of basalt fiber-reinforced polypropylene composites with different elastomers

In this study, composites based on polypropylene (PP), basalt fiber (BF), polypropylene-graft-maleic anhydride (MAPP) and different elastomers were manufactured by extrusion compounding and injection molding. The main focus of this study was to comparatively investigate the effect of three kinds of elastomers (ethylene–propylene–diene monomer (EPDM), polyethylene–octene (POE) and ethylene–vinyl–acetate (EVA)) on non-isothermal crystallization and mechanical properties of the composites with various BF contents. The tensile test results showed that BF had a reinforcing effect on PP resin, and the addition of MAPP further improved the tensile properties by the enhancement of PP/BF interfacial bonding. Among the elastomers, EPDM was more effective in improving the tensile strength and tensile modulus, while POE significantly toughened the impact strength. Micrographs of scanning electron microscope on the impact fracture surfaces indicated a good dispersion by the addition of POE and EPDM, while some agglomerations were observed in the presence of EVA. The non-isothermal crystallization kinetics were investigated based on Avrami and Mo equations at six different cooling rates by using differential scanning calorimetry. Micrographic images of polarized optical microscopy showed that the spherulite size of PP reduced in the presence of EPDM and EVA.

Crystallization kinetics study of dynamically vulcanized PA6/NBR/HNTs nanocomposites by nonisothermal differential scanning calorimetry

ABSTRACTInvestigation of crystallization behavior and kinetics of thermoplastic elastomer nanocomposites was the subject of limited works because of complexities associated with semiexperimental modeling of such phenomenon in a system containing components having completely different behavior in the molten state. Nonisothermal crystallization kinetics of dynamically vulcanized PA6/NBR/HNTs thermoplastic elastomer nanocomposites was mathematically modeled applying well‐known Avrami, Ozawa, and Mo theoretical models to the differential scanning calorimetry data gathered at various cooling rates. It was found that HNTs contribute as nucleating agents to the crystallization kinetics and cause acceleration of crystallization. Activation energy of the crystallization was calculated by correlating the crystallization peak temperature with the cooling rate using Kissinger model. It was found that Mo equation could properly describe nonisothermal crystallization kinetics of the PA6/NBR/HNTs thermoplastic elastomer nanocomposites. This was recognized from the obtained parameters of Mo equation in terms of HNTs loading level, which suggested a higher rate for dynamic crystallization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46488.

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.