Nonisothermal crystallization kinetics of poly(vinyl alcohol)/nano-zinc oxide composite
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The poly(vinyl alcoh0l)/nano-zinc oxide composite was prepared by melting extrusion to investigateits crystal property.The non-isothermal crystallization kinetics of PVA film and Poly(vinyl alcoh0l)/nano-zincoxide composite were studied through Jeziorny and Liu methods based on DSC analysis.Results show that thenon-isothermal crystallization behavior of PVA film and the composite depends on cooling rate significantly.With the increase of cooling rate,the crystallization rate constant and the imperfection degree of crystallizationare increased. At the same cooling rate,the composite exhibits larger Avrami exponent and crystallization rateconstant compared with PVA film. In order to achieve the identical crystallization degree,the composite needsa lower cooling rate than PVA film.This indicates that nano-zinc oxide can increase the crystallization rate ofPVA and act as the nucleating agent of PVA.Keywords:
Vinyl alcohol
Isothermal process
Avrami equation
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Poly (phenylene sulfide) (PPS)/nano-ZnO composites were prepared by DAKA miniature blending instrument. Isothermal crystallization behavior of PPS composites at 245°C, 250°C, 255°C and 260°C were investigated by means of DSC. The crystallization time of PPS composites is shorter than which of neat PPS at the same crystallization temperature. The Avrami equation was used to analyze DSC data. Results showed that neat PPS is homogeneous nucleation at lower crystallization temperature, which is heterogeneous nucleation at higher crystallization temperature contrarily. PPS/nano-ZnO composites are heterogeneous nucleation at various crystallization temperature, nano-ZnO particles play a role of nucleating agent.
Isothermal process
Avrami equation
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Vinyl trimethoxysilane(A-171) was grafted to chain of polyethylene(HDPE) via melt grafting reaction.The tetraethoxysilane which acted as precursor was mixed in grafted HDPE,HDPE/SiO2 hybrid materials were prepared by sol-gel process.The influence of nano-SiO2 on the crystallization behavior of HDPE was studied with differential scanning calorimetry(DSC).Results show that nano-SiO2?has an nucleating role on the crystallization,resulting in higher crystallization temperature,and lower the size distribution of crystallite,the faster of the cooling rate,the wider of crystallization peak,the lower crystallization temperature that Tp moved to.The research of non-isothermal crystallization kinetics shows that at the scope of cooling rate 5 ℃/min～20 ℃/min,hybrid materials are heterogeneous nucleation and growth in one dimension.
High-density polyethylene
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Polyvinyl Alcohol
Isothermal process
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Vinyl alcohol
Isothermal process
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Polypropylene
Isothermal process
Avrami equation
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Abstract Non‐isothermal crystallization of aluminum nanopowder‐filled poly(3,3‐bis‐azidomethyl oxetane) (PBAMO) from melt at various constant cooling rates from 1 to 10 °C min −1 was studied. Ozawa's approach was used to analyze non‐isothermal crystallization kinetics. It was found that Ozawa's approach was effective at medium constant cooling rate. The crystallization activation energy derived from Kissinger's equation was 80.8 kJ mol −1 . The experimental results showed that the aluminum nanopowder acted as a nucleating agent to raise the peak crystallization temperature and to accelerate the crystallization rate at higher constant cooling rates. Uniform crystals which showed one melting peak could be obtained at a constant cooling rate of 1 °C min −1 .
Oxetane
Isothermal process
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Nanorod
Avrami equation
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Polarized light microscopy
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Non-isothermal crystallization kinetics of flame sprayed polyamide 1010/nano-ZrO_2 composite coating
The non-isothermal crystallization kinetics of pure polyamide 1010(PA1010) coating and PA1010/nano-ZrO2 composite coating prepared by flame spraying,was investigated by differential scanning calorimetry(DSC) at various cooling rates.The Avrami analysis modified by Jeziorny and a new Mo method could describe the non-isothermal crystallization processes of PA1010 and PA1010/nano-ZrO2 composite coating very well.The values of Zc and n increased with increasing cooling rate.The value of kinetic parameter F(T) increased,and the values of a had no significant change with increasing degree of crystallinity for PA1010 and PA1010/nano-ZrO2 composite coating,respectively.The difference in the value of exponent n between PA1010 and PA1010/nano-ZrO2 composite coating suggested that the nano-ZrO2 act as nucleation agents of PA1010.The values of half-time of crystallization and crystallization rate coefficient(CRC) showed that the crystallization rate of PA1010/nano-ZrO2 composite coating was faster than that of PA1010 at a given cooling rate.
Isothermal process
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