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.

Non-isothermal Crystallization and Thermal Transformation Behaviors of Plasma Sprayed Fe_(48)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2)Amorphous Coating

The non-isothermal crystallization dynamic behavior and mechanism of plasma sprayed Fe_(48)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2)coating were thoroughly studied.The phase transition and crystallization kinetics of the coating were elaborately investigated by differential scanning calorimetry(DSC),X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The findings reveal that the characteristic temperatures of the coating shift to an elevated temperature at a higher heating rate and the crystallization processes are thermally activated.The 3-rd step of crystallization processes is more susceptible to the continuously increased heating rate while the onset crystallization reaction is less sensitive to the continuously enhanced heating rate.Fe_(23)(C,B)_6 phase is inclined to precipitate than other crystal phases due to the substantial pre-generation ofα-Fe.The onset nucleation and growth ofα-Fe crystals is tough due to a higher onset apparent activation energy.Meanwhile,the transformation from Fe_(23)(C,B)_(6)to FeB is harder in comparison with the precipitation of other crystals.The most parts of the three crystallization processes are dominated by three-dimensional diffusion model due to the fact that most values of local Avrami exponent are higher than 2.5.

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 OF POLY(L-LACTIDE)(PLLA) UNDER QUIESCENT AND STEADY SHEAR CONDITIONS

The non-isothermal crystallization of poly（L-lactide） （PLLA） under quiescent and steady shear flow conditions was in situ investigated by using polarizing optical microscopy （POM） with a hot shear stage and wide-angle X-ray diffraction （WAXD）. The shear rate and the cooling rate both play a significant role in the final crystalline morphology and crystallinity. Under quiescent conditions, the morphology assumes different sized spherulites, and its crystallinity dramatically reduces with increasing the cooling rate. On the other hand, the shear flow increases the onset crystallization temperature, and enhances the final crystallinity. When the shear rate is above 5 s^-1, cylindrite-like crystals are observed, furthermore, their content depends on the cooling rate.

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.

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.

Effect of Fe_2O_3 on non-isothermal crystallization of CaO-MgO-Al_2O_3-SiO_2 glass

The crystallization behavior and kinetics of CaO-MgO-Al2O3 SiO2（CMAS） glass with the Fe2O3 content ranging from zero to 5%were investigated by differential scanning calorimetry（DSC）.The structure and phase analyses were made by Fourier transform infrared spectroscopy（FT-IR） and X-ray diffraction（XRD）.The experiment results show that the endothermic peak temperature about 760℃ is associated with transition and the exothermic peak temperature about 1000℃ is associated with crystallization.The crystallization peak temperature decreases with increasing the Fe203 content.The crystallization mechanism is changed from two-dimensional crystallization to one-dimensional growth,and the intensity of diopside peaks becomes stronger gradually.There is a saltation for the crystallization temperature with the addition of 0.5%Fe2O3 due to the decomposition of Fe2O3.Si-O-Si,O-Si-O and T-O-T（T=Si,Fe,Al） linkages are observed in Fe2O3-CaO-MgO-Al2O3-SiO2 glass.

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.

STUDY OF ACOUSTIC EMISSION DURING NON-ISOTHERMAL CRYSTALLIZATION OF POLYPROPYLENE

In this paper we have presented the results of acoustic emission (AE) during non-isothemal crystallization of polypropylene (PP) melt with mean cooling rate 4℃/min, and discussed the effects of molecular weight (MW) on AE activity. It is shown that the amount of AE ring-down counts during whole crystallization of PP depends on the MW strongly.The copious AE bursts have been observed at the late stage of PPcrystallization. AE bursts are caused by cracking, crazing and cavitation between spherulites and inside spherulites.

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.

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.

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 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.

Study on Morphology and Non-isothermal Crystallization Behavior of Poly(phenylene sulfide)/Poly(ethylene-co-cyclo-hexane 1,4-dimethanol terephthalate) Blend

A binary alloy consisting of poly（phenylene-sulfide） （PPS）/poly（ethylene terephthalate-co-l,4- cyclohexanedimethanol） （PETG） was prepared by the melt blending technology using a twin-screw extruder. The morphology and crystallization behavior of the alloy material were investigated by means of SEM, POM and DSC. The SEM study of the alloy samples revealed that PPS and PETG comprised an incompatible system and the interface structure of two phases could be observed distinctly when the composition of the binary alloy was being changed. The POM results had revealed that incorporation of PETG into PPS could lead to formation of larger spherulite crystals in the course of PPS crystallization, but small and grainy spherulite crystals appeared with further increase in the PETG concentration. The DSC analyses revealed that addition of PETG to the alloy composition could shift the PPS crystallization temperature towards the high-temperature region.

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 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.

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.

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 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.