Non-isothermal Crystallization Kinetics of Polyamide 6/Diaminemodified MWNTs Nanocomposite

The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube （PA6/D-MWNT） nanocomposite was investigated by differential scanning calorimetry （DSC）. The modified Avrami equation, the Ozawa equation and the combined Avrami/Ozawa equation were employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. It was found that the combined Avrami/Ozawa equation could successfully describe the non-isothermal crystallization process. The results showed that D-MWNTs not only acted as effective heterogeneous nucleating agents for PA6 and noticeably increased the crystallization temperature of PA6, but also influenced the mechanism of nucleation and crystal growth of PA6 and then reduced the overall crystallization rate of the neat PA6 matrix. The crystallization activation energy for the nanocomposite sample was greater than that of the neat PA6, which indicated that the addition of D-MWNTs hindered the mobility of PA6 chain segments.

Non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends

The non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. The results show that the crystallization onset temperature(T onset) and crystallization peak temperature(T p) decrease with the increase of the content of reactive microgel, while ΔT(T onset–T p), the crystallization half-time(t1/2) and the crystallization enthalpy(ΔH c) increase. The required cooling rates of blends are higher than that of neat nylon6 in order to achieve the same relative crystallinity in a unit of time. The crystallization activation energies of the reactive microgel/nylon 6 blends are greater than those of the neat nylon 6. When the content of reactive microgel is 30%, the relative crystallinity(X t) reaches the maximum.

Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers:Effect of sebacic acid as a third comonomer

Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry(DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10 T at a given temperature or relative crystallinity degree,which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope(POM) and X-ray diffraction(XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10 T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10 T, the crystallization rate was increased with the addition of the sebacic acid comonomer.

Non-Isothermal Crystallization Kinetics of a Rapidly Solidified as-Cast TiZrHfNiCu High Entropy Bulk Metallic Glass

This paper aims to investigate the thermal behavior and crystallization kinetics of TiZrHfNiCu high entropy bulk metallic glass (HE-BMG) alloy using the standard procedure of Differential Scanning Calorimetric (DSC) annealing technique. The alloy was produced using an arc melting machine with a critical diameter of 1.5 mm. The crystallization kinetics and phase transformation mechanism of TiZrHfNiCu HE-BMG was investigated under the isochronal condition at a single heating run based on the Johnson-Mehl- Avrami (JMA) theory. In isochronal heating, the apparent activation energy for glass transition and crystallization events was analyzed by Kissinger and Ozawa methods. The average activation energy value for crystallization of TiZrHfNiCu amorphous alloys in isochronal modes was 226.41 kJ/mol for the first crystallization and 297.72 kJ/mol for second crystallization stages. The crystallization mechanism of the first step was dominated by two- and three-dimensional growth with increasing nucleation rate, while the crystallization mechanism in the second stage was dominated by two-dimensional crystallization growth with a constant nucleation rate. The diffusion mechanism result proved the theory of sluggish atomic diffusion of HEA at elevated temperature.

Non-isothermal Crystallization Kinetics of Kaolin Modified Polyester

Fiber-class modified kaolin and PET have been blended in the twin-screw and granulated to chips containing 4 wt% of kaolin.Non-isothermal crystallization process of kaolin modified polyester was investigated using a differential scanning calorimetry （DSC）,and the addition of kaolin enhances either the melting temperature （Tm） or the crystallization temperature （Tc）.The morphology of kaolin modified polyester,the melt of which is cooled at different cooling rate,was observed by scanning electron microscope （SEM）.The relationship between Tc and cooling rate F was studied.Semi-crystalline phase t1/2 makes an exponential decline with increasing F,and the higher the cooling rate,the shorter the time of crystallization completion.Non-isothermal crystallization kinetics parameters and the activation energy were calculated,indicating that the higher rate of cooling needs the higher relative crystallinity in the unit crystallization time,the crystallization rate increased while speeding up the temperature reduction,and the activation energy ΔE was calculated to be-204.1566 kJ/mol for the non-isothermal crystallization processes by the Kissinger＇s methods.

Non-Isothermal Crystallization Kinetics of PET Under Solid State Poly condensation

An equation of non-isothermal crystallization kinetics was derived according to a new model and the crystallizations of both the PET samples under solid state polycon-densation and the pre-orientation yarn of high speeding spinning PET were studied with this equation. The results show that there is a good linear relationship between In {-In[1-X(T)]} and lnΦ. The index m in the equation approximately equals to 3 for PET chips and 1. 3 for pre-orientated yarn. At the same temperature, Q(T) decreases with the increase of PET M. W. and the kinetics parameters obtained by Jeziorny' s method indicate that G also decreases with the increase of PET M. W.. Q(T) and Gc show the same varying tendency in the non-isothermal crystallization process.

Non-isothermal Crystallization Kinetics of Modified Poly(ethylene terephthalate) with Ultraviolet Protection

The non-isothermal crystallization kinetics of modified poly(ethylene terephthalate) (PET) with the function of ultraviolet (UV) protection was studied by means of differential scanning calorimetry. The kinetics of the modified polymer under non-isothermal crystallization was analyzed by Ozawa equation. The crystallization behavior of the modified polymer obeyed Ozawa theory. The additives in the polymer whose function was UV-resistant acted as crystal nucleus in the processing of crystallization, which resulted in the increase of Avrami index and the crystallization rate of the cooling system.

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.

Isothermal and Non-Isothermal Crystallization Kinetics of Conductive Polyvinylidene Fluoride/Poly(Ethylene Terephthalate) Based Composites

This work deals with isothermal and non-isothermal crystallization kinetics of electrically conductive polyvinylidene fluoride/poly(ethylene terephthalate) (PVDF/PET) based composites. It completes our previous work in which we related the crystallinity of these conductive PVDF/PET based composites to their through-plane resistivity [1]. Isothermal crystallization was described using the logarithmic form of the Avrami equation and it was observed that the crystallization rate of the PVDF phase inside the composite became slower compared to that of neat PVDF. In non-isothermal crystallization, the Avrami exponent of PVDF phase did not show any noticeable variation;however, that of PET phase, which contains the major part of the conductive carbon black (CB) and graphite (GR) additives, showed an evident decrease compared with neat PET. It was also observed that, at the same cooling rate, the crystallization rate of PVDF and PET phases inside the composite was slower than that of neat PVDF and PET.

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.

Exploring the effect of cooling rate on non-isothermal crystallization of copolymer polypropylene by fast scanning calorimetry

Polypropylene is commonly used as a binder for ceramic injection molding,and rapid cooling is often encountered during processing.However,the crystallization behavior of polypropylene shows a strong dependence on cooling rate due to its semi-crystalline characteristics.Therefore,the influence of cooling rate on the quality of final product cannot be ignored.In this study,the fast differential scanning calorimetry(FSC)test was performed to study the influence of cooling rate on the non-isothermal crystallization behavior and non-isothermal crystallization kinetics of a copolymer polypropylene(PP BC03B).The results show that the crystallization temperatures and crystallinity decrease as the cooling rate increases.In addition,two exothermic peaks occur when cooling rate ranges from 30 to 300 K·s^(-1),indicating the formation of another crystal phase.Avrami,Ozawa and Mo equations were used to explore the non-isothermal crystallization kinetics,and it can be concluded that the Mo method is suitable for this study.

An Efficient Organic Additive to Control the Crystallization Rate of Aliphatic Polyketone: A Non-isothermal Crystallization Kinetics Study

Three types of organic compounds--two carboxylic acids and an anhydride, were used as additives for polyketone （PK）. The effect of the additive structure and their feed ratios on the melting temperature, crystallization temperature, and crystallization rate of PK were studied. We found that the crystallization temperature could be reduced significantly by introducing a small quantity of organic additive, in particular, an anhydride. On addition of 1 phr of anhydride, the crystallization temperature was reduced by 10.7 ℃. Therefore, the non-isothermal crystallization kinetics of aliphatic PKJanhydride blends with various feed ratios was investigated using DSC. The results were analyzed by various theoretical models, such as Avrami, Ozawa and combined Avrami-Ozawa models.

Effect of Al_2O_3 addition on the non-isothermal crystallization kinetics and long-term stability of BCABS sealing glass for IT-SOFCs

Owing to adjustable thermal expansion performance, BaO–CaO–Al_2O_3–B_2O_3–SiO_2(BCABS) glass has a promising commercialization prospect for intermediate temperature-solid oxide fuel cells(IT-SOFCs) sealing. Herein, Al_2O_3 with two different contents was added into the same glass formulation, referred to as A and B glass, respectively. In terms of the non-isothermal crystallization kinetic behavior, the effect of Al_2O_3 as the unique intermediate was innovatively studied on the long-term performance of BCABS sealing glass. After the heat treatment at 1023 K for 100 h, the change of the network structure and the expansion coefficient of the glass were characterized. The results showed that the addition of Al_2O_3 as a network forming body could enhance the structure of glass, and increase the activation energy for glass transition, which could effectively inhibit the crystallization ability of sealing glass. Therefore, the B glass with the higher Al_2O_3 content showed the better long-term sealing ability, which was greatly beneficial for IT-SOFCs sealing.

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION

A kinetic equation of non-isothermal crystamzation was derived by extending Avrami's equation to the non-isothermal situation. More crystallization information can be obtained from this kinetic equation. The curves of non-isothermal and isothermal crystallizations were analysed and compared for poly (ethylene terephthalate) (PET), and the results were discussed.

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF NYLON-1010

The kineties of non-isothermal crystallization of Nylon-1010 has been investigated by using differential scanning calorimetry(DSC), DSC curves were obtained under cooling rate(R): 2. 5, 5, 10, 20, 40K/min. Applying Mandelkern and Ziabicki theories, the values of the Z kinetic parameter and G the kinetic crystalllzab- ility have been determined. Expenents of Avrami obtained in this work decrease with increase of cooling rate and then level off. The experimental results show disagreements with the Ozawa equation.

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m^0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.

Kinetic Study of Non-Isothermal Crystallization in Se_90-xZn₁₀Sb_x(x = 0, 2, 4, 6) Chalcogenide Glasses

Crystallization and glass transition kinetics of Se90-xZn10Sbx (x = 0, 2, 4, 6) chalcogenide glasses prepared by conventional melt-quenching technique were studied under non-isothermal condition using a differential scanning Calorimeter (DSC) measurement at different heating rates 5, 7, 10 and 12°C/min. The glass transition temperatures Tg, the crystallization temperatures Tc and the peak temperatures of crystallization Tp were found to be dependent on the compositions and the heating rates. From the dependence on the heating rates of Tg and Tp, the activation energy for glass transition, Eg, and the activation energy for crystallization, Ec, are calculated and their composition dependence is discussed. The activation energy of glass transition Eg, Avrami index n, dimensionality of growth m and activation energy of crystallization Ec have been determined from different models.

Selective precipitation and non-isothermal crystallization kinetics of britholite from low grade REE-bearing slag

In order to improve the recovery rate of rare earth,the effect of P_(2)O_(5) and cooling rate on the selective precipitation of CaO-SiO_(2)-TiO_(2)-P_(2)O_(5)-Nb_(2)O_(5)-CeO_(2)-CaF_(2) slag system was explored using X-ray powder diffraction,a scanning electron microscope,an electron probe micro-analyzer and a confocal laser scanning microscope.The apatite(Ca_(2.02)Ce_(7.98)Si_(6.00)O_(26.00))is tiny and difficult to be separated from the slag without P_(2)O_(5).When the addition of P_(2)O_(5) is 6 wt%-10 wt%,the cerium and phosphorus are found to be enriched in britholite(Ca_(5-x)Ce_(x)[(SiO_(4))_(x)(PO_(4))_(3-x)]F)phase while x is negatively correlated with P_(2)O_(5) content in the slag.The influence of P_(2)O_(5) and cooling rate on the non-isothermal crystallization kinetics was also investigated.For the cooling rate between 5 and 40℃/min,continuous cooling transformation diagram of britholite was constructed when the P205 content is between 6 wt%-10 wt%.The modified Avrami model was applied to determine the crystallization mode of slag with 10 wt%P_(2)O_(5).It is shown that the crystallization mode is diffusion-controlled with constant nucleation rate and one-dimensional growth.In consideration of quantity and volume of crystals,the reasonable cooling rate is between 10and 30℃/min.

Investigation of Crystallization Kinetics in Glassy Se and Binary Se₉₈M₂(M=Ag, Cd, Zn) Alloys Using DSC Technique in Non-Isothermal Mode

The crystallization kinetics of glassy Se and binary Se98M2 (M=Ag, Cd, Zn) alloys have been studied at different heating rates (5, 10, 15, 20 Kmin-1) using Differential Scanning Calorimetric (DSC) technique. The crystallization temperature (Tc) is determined from exothermic peak obtained in DSC scans of present samples. The variation in peak crystallization temperature (Tc) with the heating rate (β) has been used to investigate the growth kinetics using Kissinger, Augis-Bennet and Matusita-Sakka models. The activation energy of crystallization (Ec) has been found to increase with Ag additive and to decrease with Zn and Cd additive. The value of various kinetic parameters such as rate constant (Kp), Avrami index (n), thermal stability (S) and Hruby number (Hr) have been calculated under non-isothermal mode. The maximum change in different kinetic parameters has been found after the incorporation of Ag additive.

Thiourea crystal growth kinetics,mechanism and process optimization during cooling crystallization

In the cooling crystallization process of thiourea,a significant issue is the excessively wide crystal size distribution(CSD)and the abundance of fine crystals.This investigation delves into the growth kinetics and mechanisms governing thiourea crystals during the cooling crystallization process.The fitting results indicate that the crystal growth rate coefficient,falls within the range of 10^(-7)to 10^(-8)m·s^(-1).Moreover,with decreasing crystallization temperature,the growth process undergoes a transition from diffusion-controlled to surface reaction-controlled,with temperature primarily influencing the surface reaction process and having a limited impact on the diffusion process.Comparing the crystal growth rate,and the diffusion-limited growth rate,at different temperatures,it is observed that the crystal growth process can be broadly divided into two stages.At temperatures above 25℃,1/qd(qd is diffusion control index)approaches 1,indicating the predominance of diffusion control.Conversely,at temperatures below 25℃,1/qd increases rapidly,signifying the dominance of surface reaction control.To address these findings,process optimization was conducted.During the high-temperature phase(35-25℃),agitation was increased to reduce the limitations posed by bulk-phase diffusion in the crystallization process.In the low-temperature phase(25-15℃),agitation was reduced to minimize crystal breakage.The optimized process resulted in a thiourea crystal product with a particle size distribution predominantly ranging from 0.7 to 0.9 mm,accounting for 84%of the total.This study provides valuable insights into resolving the issue of excessive fine crystals in the thiourea crystallization process.