Non-isothermal Crystallization Kinetics Of Polypropylene Research Articles

Role of the nucleating agent masterbatch carrier resin in the nonisothermal crystallization kinetics of polypropylene

Role of the nucleating agent masterbatch carrier resin in the nonisothermal crystallization kinetics of polypropylene

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.

Experimental and theoretical investigation on the non-isothermal crystallization kinetics of polypropylene reinforced with multiwalled carbon nanotubes

Polypropylene (PP) nanocomposites were prepared by incorporating multiwalled carbon nanotubes (MWCNTs) at different contents from 1 to 4 wt%. The crystallization studies were performed using differential scanning calorimetry (DSC) at varying cooling rates viz. 5, 10, 15 and 20 °C/min. The Avrami model could describe the intermediate stages of crystallization quite well whereas the Ozawa model failed to explain the kinetics particularly in the region of peak crystallization temperatures. Mo model could very well describe the nucleation, crystal growth and the crystal impingement which was verified from the linearity obtained by the model equation and from the Mo parameters.

The effect of poly(4‐methyl‐1‐pentene) on the nonisothermal crystallization kinetics of polypropylene

The effect of poly(4‐methyl‐1‐pentene) on the nonisothermal crystallization kinetics of polypropylene

Non-isothermal crystallization kinetics of polypropylene/short glass fibre/multiwalled carbon nanotube composites.

The non-isothermal crystallization kinetics of polypropylene (PP) reinforced with multiwalled carbon nanotubes (MWCNTs) and short glass fibres (GF) was studied by differential scanning calorimetry (DSC). The glass fibre concentration was maintained at 20 wt% and the MWCNT content ranged from 1 to 5 wt% in the PP matrix. The crystallization studies performed by DSC showed an increase in crystallization rate and a decrease in half time of crystallization of PP in the presence of micro and nano fillers. The Avrami, Ozawa, and Mo models were applied to analyze the non-isothermal crystallization behavior of PP multiscale composites. The Avrami model could very well describe the crystallization behavior of PP to 70% of the completion of crystallization. Beyond that level, it deviated significantly for all composites. On the other hand, the kinetics of crystallization could be well described by the Mo model. The strongest nucleating effect and the lowest activation energy were obtained for the composite with 2 wt% MWCNT and 20 wt% glass fibre. The X-ray diffraction analysis showed a significant reduction in the average crystal size in accordance with the amount of MWCNTs added.

Crystallization Kinetics of PP/Talc/Coir Hybrid Composites

Polypropylene (PP), a versatile polymer finds application in many sectors. However, it has low impact strength.To overcome this draw back elastomer is added, which results in improved impact property at the expense of decreased tensile strength. To improve this fillers are added. However some fillers also improve impact strength. In this work only fillers have been used to get balance of properties in PP. Knowledge of crystallization of PP is important for processing of PP. In this work the effect of hybrid fillers on PP has been studied on the isothermal and non-isothermal crystallization kinetics of PP. The fillers used are coir and talc.

A critical approach to the Kissinger analysis for studying non-isothermal crystallization of polymers

This work presents a new empirical method to analyse the non-isothermal crystallization kinetics of polypropylene. The Kissinger analysis, widely used in the literature to calculate an activation energy of the crystallization mechanism, was critically examined regarding its applicability to the crystallization process of semicrystalline polymers. The analogy between the systems modelled by Kissinger and polymer crystallization applies only in very restrictive cases, and the activation energy, as commonly used, is an ill-defined quantity. Nevertheless, it was shown that the Kissinger analysis yields a phenomenological parameter, here called REact, related to the crystallization kinetics at moderately high cooling rates (up to ~50 °C s−1). This parameter, created with data obtained on more than 20 poly(propylene) compounds based on four different base polymers of different chain structure and composition, correctly estimates the crystallization performance of different systems at higher cooling rates, demonstrated by a good correlation between REact and the morphology formed in cable extrusion and cast film extrusion processes.

Effect of sepiolite on nonisothermal crystallization kinetics of polypropylene

The purpose of this paper is to study the nonisothermal crystallization kinetics of polypropylene (PP)/Sepiolite nanocomposites in the absence/presence of compatibilizer [maleic anhydride-grafted polypropylene (PP-g-MA)] using differential scanning calorimetry. Crystallization exotherms were recorded at four different cooling rates, i.e., 5, 10, 15, and 20 °C/min. Crystallization parameters were analyzed using Ozawa, Avrami, Jeziorny, and Liu’s models. Nucleation ability of Sepiolite was evaluated by employing Dobreva and Gutzowa models. The activation energy of nonisothermal crystallization kinetics process was estimated using three isokinetic models (Augis–Bennet, Kissinger, and Takhore). DSC cooling scans of PP and PP/Sepiolite nanocomposites showed that the crystallization onset temperature, T0, and peak exotherm temperature, Tp, increased in the presence of Sepiolite. However, Tp decreased with the increasing amount of PP-g-MA in PP/Sepiolite nanocomposites. The values of F(T), KA and half-time to crystallization (t1/2) showed that the rate of crystallization of PP was faster in the presence of Sepiolite at a given cooling rate. The t1/2 values also decreased slightly for compatibilized PP/Sepiolite nanocomposites. The values of exponent ‘n’ determined using Avrami analysis indicated that nonisothermal kinetic crystallization corresponded to three-dimensional growth with heterogeneous nucleation in all the samples. Sepiolite shows its better nucleating effect in the presence of PP-g-MA as investigated by Dobreva and Gutzowa method. The increase in ΔE values of PP/Sepiolite nanocomposites is proportional to the Sepiolite content which is in the range of 33–38 % in case of PPS-5 and 44–47 % in case of PPS-10 as compared to PP calculated using three different models while decreasing on adding compatibilizer. Incorporation of Sepiolite in the presence of compatibilizer, PP-g-MA, in the optimized ratio results in accelerating the overall nonisothermal crystallization process of PP/Sepiolite nanocomposites.

Nonisothermal crystallization kinetics of polypropylene composites reinforced with down feather fiber

Nonisothermal crystallization kinetics of pure polypropylene and polypropylene/down feather fiber composites were investigated using a differential scanning calorimeter at five different cooling rates. The experimental data on crystallinity versus temperature were analyzed by Avrami, Ozawa, and Liu models, respectively. The results indicated that the presence of down feather fiber served as nucleating agent and increased the onset and peak temperatures of crystallization of polypropylene/down feather fiber composites. Interestingly, polypropylene/down feather fiber composites showed a slower primary crystallization and a faster secondary crystallization than pure PP, meaning that down feather fiber retired the crystallizaiton process of PP matrix. The nucleation activity and activation energies were also calculated and agreed well with these results. Wide‐Angle X‐ray diffraction patterns indicated that down feather fiber induced the formation of β‐monoclinic crystals in polypropylene matrix. These phenomena were definitely different from the nonisothermal crystallization kinetics of polypropylene composite based on inorganic particles and organic cellulose fibers. POLYM. COMPOS., 37:3103–3112, 2016. © 2015 Society of Plastics Engineers

Non-isothermal crystallization kinetics of polypropylene and hyperbranched polyester blends

Polypropylene (PP) with different contents of the second generation hyperbranched polyester (HBP) is prepared by melt blending method. The non-isothermal crystallization kinetics of PP and PP/HBP blends is investigated under differential scanning calorimetry (DSC). The Mo equation is used to analyze the DSC data. The results show that the Mo theory is suitable for crystallization kinetics of the blends. Fast cooling rate is not good for crystallizing and nucleating. The values of half crystallization time (t1/2), crystallization enthalpy (ΔHc) and temperature range (ΔT) of PP/HBP blends decrease when HBP is added. The required cooling rate of PP is higher than that of PP/HBP blends in order to reach the same relative crystallinity. Crystallization rate increases with the addition of HBP. The crystallization rate reaches a maximum when the content of HBP is 5%. In addition, the activation energies of PP and PP/HBP blends are calculated by Kissinger equation, revealing that the content of HBP has a little effect on the crystallization activation energy.

Nonisothermal crystallization kinetics of AB2 hyperbranched polymer‐filled polypropylene

In this article, nonisothermal crystallization kinetics of polypropylene (PP) and AB2 hyperbranched polymer (HBP)‐filled PP have been investigated by differential scanning calorimetry. The Avrami analysis modified by Mandelkern and a method combined with Avrami and Ozawa equations were employed to describe successfully the nonisothermal crystallization kinetics of samples. The conclusion showed that HBP can prompt crystallization effectively. Furthermore, in blends of different HBP contents, the value of t1/2 became smaller with increasing HBP content; however, the crystallization rate of the blend decreased slightly when content of HBP is 5%. An increase in the Avrami exponent showed that addition of HBP influenced the mechanism of nucleation and the growth of PP crystallites. The possible explanation could be attributed to the fractal structure of HBP. The polarized micrographs showed that HBP acts as a heterogeneous nucleation agent, and the nucleation efficiency has increased remarkably in HBP/PP blends. POLYM. ENG. SCI., 53:2535–2540, 2013. © 2013 Society of Plastics Engineers

Non-isothermal crystallization kinetics of polypropylene/MAP-POSS nanocomposites

Non-isothermal crystallization kinetics of polypropylene (PP)/methylacryloypropy polyhedral oligomeric silsesquioxanes (MAP-POSS) nanocomposites (PP/MAP-POSS) were investigated by DSC at various cooling rates. Jeziorny and Mo method were used to study the non-isothermal crystallization kinetics. The results show that the Jeziorny and Mo method are all successful in describing the non-isothermal crystallization kinetics of PP/MAP-POSS nanocomposites. The MAP-POSS can act a role of heterogeneous nucleation and increase the crystallization rate constant Z c and decrease crystallization half time t 1/2, and the spherulite crystal size decreases, the inter-spherulitic action or crosslinking structure each other appear at the appropriate content. The DSC peak temperature T p increase about 5 °C, t 1/2 reduce 0.21 min at 6 % content of MAP-POSS and heating rate of 10 °C/min. The MAP-POSS can also increase the mechanical property of PP/MAP-POSS nanocomposites, the tensile strength and impact strength increase from 12.97 to 19.93 MPa and from 33.2 to 52.6 kJ/m2, respectively, at 4 % content of MAP-POSS. But the spherulitic crystal becomes larger and boundaries become clearer again; the macrophase separation will occur and mechanical properties decrease when more and more MAP-POSS was added. The nanocomposite has the best mechanical property at 4 % content of MAP-POSS.

Nonisothermal crystallization kinetics of polypropylene/polypropylene‐g‐polystyrene/polystyrene blends

AbstractThe nonisothermal crystallization kinetics of polypropylene (PP), PP/polystyrene (PS), and PP/PP‐g‐PS/PS blends were investigated with differential scanning calorimetry at different cooling rates. The Jeziorny modified Avrami equation, Ozawa method, and Mo method were used to describe the crystallization kinetics for all of the samples. The kinetics parameters, including the half‐time of crystallization, the peak crystallization temperature, the Avrami exponent, the kinetic crystallization rate constant, the crystallization activation energy, and the F(T) and a parameters were determined. All of the results clearly indicate that the PP‐g‐PS copolymer accelerated the crystallization rate of the PP component in the PP/PP‐g‐PS/PS blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Influence of m-isopropenyl-α,α-dimethylbenzyl isocyanate and styrene on non-isothermal crystallization behavior of polypropylene

Non-isothermal crystallization kinetics of polypropylene (PP), m-isopropenyl-α,α-dimethyl-benzyl isocyanate grafted PP (PP-g-m-TMI), and styrene(St), as comonomer, together with m-TMI grafted PP (PP-g-(St-m-TMI)) was investigated by using differential scanning calorimetry (DSC) under different cooling rates. The crystallization rates of all samples increased with increasing cooling rate. The relation of the half time of crystallization (t1/2) of the three samples, t1/2(PP-g-(St-m-TMI)) < t1/2(PP-g-m-TMI) < t1/2(PP), implying the introduction of St could effectively improve the degree of grafting of m-TMI, resulting in crystallization temperature increased, and the crystallization rate was the fastest. Three methods, namely, the Avrami, the Ozawa, and the Mo, were used to describe the crystallization process of the three samples under non-isothermal conditions. The Avrami and Ozawa neglected the secondary crystallization that follows primary crystallization. The Mo method can successfully describe the overall non-isothermal crystallization process of all the samples. It has been found that the F(T)(PP-g-(St-m-TMI)) < F(T)(PP-g-m-TMI) < F(T)(PP), also meaning that the crystallization rate of PP-g-(St-m-TMI) and PP-g-m-TMI were faster than that of PP. The activation energy (ΔE) for non-isothermal crystallization of all samples was determined by using the Kissinger method. The result showed that the lower value of ΔE for crystallization obtained for PP-g-m-TMI and PP-g-(St-m-TMI) confirmed the nucleating effect of St and m-TMI on crystallization of PP.

Non-isothermal melt crystallization kinetics of anhydrite-filled polypropylene composites

The non-isothermal crystallization kinetics of polypropylene (PP), PP/anhydrite composites were investigated by differential scanning calorimetry (DSC) with various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the non-isothermal crystallization process of these samples. The difference in the exponent n between PP and PP/anhydrite composites indicated that non-isothermal kinetic crystallization corresponded to tri-dimensional growth with heterogeneous nucleation. The values of half-time, Zc and F(T) showed that the crystallization rate increased with the increasing of cooling rates for PP and PP/anhydrite composites, but the crystallization rate of PP/anhydrite composites was faster than that of PP at a given cooling rate. The method developed by Ozawa did not describe the non-isothermal crystallization process of PP very well. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The result showed that the activation energy of PP/anhydrite was greatly larger than that of PP.

Study of the Nonisothermal Crystallization Kinetics and Melting Behaviors of Polypropylene Reinforced with Single-Walled Carbon Nanotubes Nanocomposite

Nonisothermal crystallization kinetics of polypropylene (PP) nanocomposite reinforced with 0.5 wt. % single-walled carbon nanotubes (SWNT) was characterized by differential scanning calorimetry at five different cooling and heating rates. The Avrami, Ozawa, and Seo-Kim kinetic models were used to describe the nonisothermal crystallization of the polymer and its nanocomposite. The addition of nano-filler, in general, improved the crystallization rate and increased the peak crystallization temperature of the nanocomposite as compared to PP. The results show that the Avrami and Seo-Kim models are suitable under different cooling rate conditions but that the Ozawa model is inappropriate for the nanocomposite. Equilibrium melting temperatures, derived from the linear Hoffman-Weeks equation, were shown to decrease in the nanocomposite. Additional analysis was performed based on the Thomson-Gibbs, Lauritzen-Hoffman, and Dobreva-Gutzowa theories, which were applied to take into account the lamellar thickness, nucleating agent, and nucleating activity of the nanocomposite in the nonisothermal melt crystallization process.

Non-isothermal crystallization, melting behavior and polymorphism of polypropylene in β-nucleated polypropylene/recycled poly(ethylene terephthalate) blends

β-Nucleated polypropylene (PP), non-compatibilized and compatibilized β-nucleated PP/recycled poly(ethylene terephthalate) (r-PET) blends were prepared on a twin-screw extruder. The compatibilizers were maleic anhydride grafted PP (PP-g-MA), glycidyl methacrylate grafted PP (PP-g-GMA), maleic anhydride grafted polyethylene-octene (POE-g-MA) and polyethylene-vinyl acetate (EVA-g-MA) elastomers. Effects of r-PET content, compatibilizer type and content, pre-melting temperature and time on the non-isothermal crystallization and melting behavior, and polymorphism of PP in the blends were investigated by differential scanning calorimeter (DSC). DSC results show that the crystallization temperature of PP crystallized predominantly in β-modification was higher than that of neat PP. In the non-compatibilized blend, PP matrix crystallized mainly in α-modification even if r-PET content was only 10 wt%. However, PP-g-MA compatibilization made PP matrix crystallize mainly in β-modification, but PP-g-GMA, POE-g-MA and EVA-g-MA did not improve the β-modification content distinctly. The α-crystal melting peak temperature of PP decreased with increasing pre-melting temperature, but r-PET content, compatibilizer type and content as well as pre-melting time had no obvious effect on the melting temperature of PP. The increase in PP-g-MA content, pre-melting temperature and time was benefit for the formation of β-modification. It is suggested that the β-nucleating agent is encapsulated or dissolved in polar r-PET in β-nucleated PP/r-PET blend, addition of PP-g-MA to the non-compatibilized blend resulted in transferring β-nucleating agent from r-PET phase into PP phase, the increase in PP-g-MA content, melting temperature and time was benefit for transferring β-nucleating agent from r-PET phase into PP phase. The non-isothermal crystallization kinetics of PP in the blends were evaluated by Mo’s method.

Nonisothermal Crystallization Modeling and Simulation for Polypropylene/Nano CaSO4 Composites with Variations in Nanosizes and Wt.% of Loading

Avrami and Ozawa's combined analysis was employed to study the nonisothermal crystallization kinetics of Polypropylene (PP): CaSO4 (of 12 and 22 nm) composites using a Differential Scanning Calorimeter (DSC). The parameters, such as Avrami's exponent (n) and growth rate constant (Zt), that characterized the system of different nanosize composites and virgin PP, were determined. The relative degree of crystallinity as a function of temperature for PP/nano CaSO4 composites at the same cooling rate and the Sigmoidal shape of curves indicate a strong interaction between PP molecules and the nanolayer, which leads to greater nucleation with a reduction in nanosizes. The theoretical combination of kinetic equations was found to be suitable to describe the physical phenomena of real system. The values of parameters n, Zt and predicted time t for crystallization at a single cooling rate were obtained from the mathematical model.

Properties and Crystallization of Maleated Polypropylene/Graphite Flake Nanocomposites

Polypropylene (PP)/graphite (G) hybrid nanocomposites have been prepared by melt mixing using maleated PP (PP-g-MA) and graphite oxide (GO) as compatibilizing agents. Melt mixing was achieved using a Gelimat, a high-speed thermo-kinetic mixer. The PP-g-MA and GO used as compatibilizers helped the dispersion of the graphite on a nano-scale and improved flexural properties but more significantly the impact strength of the material. TEM micrographs showed a partial exfoliation of the graphite in the PP/PP-g-MA/GO/G hybrid nanocomposites. SEM micrographs of etched nanocomposite samples showed a fine grain micron-sized structure, while pure PP was characterized by larger 3-dimensional spherulites. Non-isothermal crystallization kinetics of PP and PP/PP-g-MA/GO/G nanocomposites were investigated by differential scanning calorimetry (DSC). The crystallinity and crystallization temperature of the nanocomposites were higher than for neat PP. Using the Kissinger model, the activation energy of crystallization of the nanocomposites was determined to be lower than PP. Models by Ozawa and Liu et al. were used to analyze and describe the non-isothermal crystallization kinetics. Overall, results indicate that the type of nucleation, growth and geometry of PP crystals markedly change in the presence of nano-sized graphite particles.

Nonisothermal Crystallization Modeling and Simulation of Polypropylene/Nano Ca3(PO4)2 Composites with Variation in Wt.% of Loading and Reduction in Nanosize

Nonisothermal crystallization kinetics of polypropylene (PP)/Ca3(PO4)2 composites was studied using differential scanning calorimetry (DSC) for various nanosizes by employing Avrami and Ozawa's combined analysis. Parameters such as Avrami's exponent (n) and composite growth rate constant (Zt) were determined, which characterize the system of different nanosize composites and virgin PP. The relative degree of crystallinity as a function of temperature for PP-nano Ca3(PO4)2 composites at the same cooling rate and sigmoidal shape of curves indicates that there is a strong interaction between PP molecule and nanolayer, which leads to greater nucleation with reduction in nanosizes. A theoretical combination of kinetic equations is found to be suitable to describe the physical phenomena of a real system. The values of parameters n, Zt, and predicted time t for crystallization at a single cooling rate were obtained from the mathematical model.