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1.
Ming-tao Run Zeng-kun Wang Xin Li Hong-chi Zhao 《Frontiers of Materials Science in China》2009,3(4):386-394
The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized
poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester
and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study
the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable
for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in
blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal
dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the
PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength
as PEO-MA content is 3 wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the
blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends. 相似文献
2.
采用冲击试验机、差示扫描量热仪和热台偏光显微镜研究了聚对苯二甲酸丙二醇酯(PTT)/热塑性聚酯弹性体(TPEE)共混合金的抗冲击性能、结晶熔融行为和晶体形态。结果表明,TPEE可以提高共混材料的缺口冲击强度;共混物只有一个玻璃化转变温度,且随着TPEE含量的增加而降低,两组分具有良好的相容性;共混物在玻璃态结晶时,随着TPEE含量增加,冷结晶热焓降低,结晶峰温度降低。共混物熔体的起始结晶温度降低,但在低温时结晶速率加快,TPEE对PTT的结晶化具有促进作用。共混物中PTT形成球晶,但由于TPEE的干扰而使PTT的球晶尺寸减小,晶体形态完善程度下降。 相似文献
3.
聚氧化乙烯(PEO)及其与高氯酸锂复合体系的非等温结晶动力学研究 总被引:1,自引:1,他引:0
用示差扫描量热法(DSC)研究了PEO及其与高氯酸锂复合体系的非等温结晶过程.分别用Jeziorny方法、一种结合Avrami和Ozawa方程的方法对该体系的非等温结晶过程进行了研究,分别得到PEO进行非等温结晶时的动力学参数.结果表明LiClO4晶粒缩短了PEO的结晶时间,使复合体系中PEO的结晶速率要大于纯PEO;但纯PEO结晶时形成的晶体更完善.为使二者达到相同的相对结晶度,纯PEO体系需要更大的冷却速度.LiClO4微粒能有效地将PEO的结晶相转变成非晶相,也就是说LiClO4可有效地抑制PEO的结晶过程. 相似文献
4.
用示差扫描量热法研究了PEO及其与高氯酸锂复合体系的等温结晶过程。用Avrami方程分析了PEO和复合体系中PEO的等温结晶动力学,得到了PEO在不同体系中等温结晶时的动力学参数。PEO的Avrami指数n都趋近2.5,说明PEO晶体以三维方式依热成核生长。动力学参数表明,复合体系中PEO结晶时以异相成核为主。LiClO4对PEO等温结晶过程的影响如下:作为PEO结晶的成核剂而加快其结晶过程;增加了复合体系的粘度,缩短了PEO的结晶半时间,使其结晶总速率增大;降低了复合体系中PEO的绝对结晶度。 相似文献
5.
This article reports the nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET) nanocomposites. The non-isothermal crystallization behaviors of PET and the nanocomposite samples are studied by differential scanning calorimetry (DSC). Various models, namely the Avrami method, the Ozawa method, and the combined Avrami-Ozawa method, are applied to describe the kinetics of the non-isothermal crystallization. The combined Avrami and Ozawa models proposed by Liu and Mo also fit with the experimental data. Different kinetic parameters determined from these models prove that in nanocomposite samples intercalated silicate particles are efficient to start crystallization earlier by nucleation, however, the crystal growth decrease in nanocomposites due to the intercalation of polymer chains in the silicate galleries. Polarized optical microscopy (POM) observations also support the DSC results. The activation energies for crystallization has been estimated on the basis of three models such as Augis-Bennett, Kissinger and Takhor methods follow the trend PET/2C20A < PET/1.3C20A < PET, indicating incorporation of organoclay enhance the crystallization by offering large surface area. 相似文献
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7.
对Avrami结晶动力学理论在非等三条件下的几种应用形式进行了比较。结果表明用Avrami基本方程、速率方程和经典理论均可导出与Ozawa方程同形的方程。将导出的方程用于解析高聚物的等速变温DSC结晶曲线,既可求出表征结晶机理的参数Avrami指数n,又可求出在征结晶速率的参数。对各种方法所得结果进行了比较,发现依据经典理论导出的方程计算结晶速率常数与等温结晶所得结果吻合得最好。 相似文献
8.
PET/PTT共混体系的结晶熔融行为 总被引:5,自引:0,他引:5
对PET/PTT共混体系的DSC热分析结果表明,在共混体系中两组分形成各自的晶体,呈现各自的熔点Tm,但两种聚合物各自的结晶过程是彼此受对方影响的。从形态和热力学两方面对共混体系的熔点下降行为进行了解释,根据N ish i-W ang方程的计算结果,PET/PTT共混体系的相互作用能密度和相互作用参数都为负值,表明PET/PTT共混体系在熔融态是热力学稳定的相容体系,在该体系中,PET和PTT分子间存在着密切的相互作用。 相似文献
9.
Structuring of multi-layered spherulites in aryl polyester of poly(trimethylene terephthalate) (PTT) by stepwise crystallization was attempted. Characterization of feasibility was performed by polarized-light microscopy (POM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). Two- or three-layered spherulites could be developed in PTT by subjecting to stepwise crystallization. Sequence and number of layers in spherulites can be designed by altering the steps of temperatures with proper holding time. Time must be allocated properly in the multiple steps if three different textures are to be structured into one single PTT spherulite by stepwise crystallization. Coexistence of multiple lamellar thicknesses and various degrees of crystal perfection were supported by DSC results. The various crystalline regions of the layered spherulites in PTT develop upon stepwise crystallization exhibit the same unit cell as demonstrated by WAXD crystallographs. 相似文献
10.
聚酯/热致液晶聚合物体系的非等温结晶动力学研究 总被引:7,自引:0,他引:7
热致性液晶共聚酯PET/60PHB组分对PET及PBT在两种共混体系中的非等温结晶行为的影响用DSC方法进行了研究,并用Ozawa方法处理了动力学数据。随共混体系LCP含量的增加,PET的Avrami指数n趋于降低而PBT的n值趋于增加,表明在非等温结晶条件下,对不同组成的共混物体系有着不同的成核和晶体生长的机理。 相似文献
11.
Miscibility and melting properties of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) blends 总被引:1,自引:0,他引:1
Hao Liang Fang Xie Wei Wu Fuquan Guo Biao Chen Jie Xu 《Journal of Materials Science》2008,43(8):2739-2744
The miscibility and melting properties of binary crystalline blends of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate)
(PEN/PTT) have been investigated with differential scanning calorimetry (DSC). The glass transition and cold crystallization
behaviors indicated that in PEN/PTT blends, there are two different amorphous phases and the PEN/PTT blends are immiscible
in the amorphous state. The polymer–polymer interaction parameter,
, calculated from equilibrium melting temperature depression of the PEN component was −1.791 × 10−5 (300 °C), revealing miscibility of PEN/PTT blends in the melt state. 相似文献
12.
Ahmad Nawaz Khan Po-Da Hong Wei-Tsung Chuang Kan-Shan Shih 《Materials Chemistry and Physics》2010,119(1-2):93-99
In this work, the structure of poly(trimethylene terepthalate) (PTT)/monolayer nano-mica (MNM) nanocomposites are investigated by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and scanning electron microscope (SEM). In the PTT nanocomposites, the crystallization induces the segregation of MNM in which three morphologies, including interlamellar, interfibrillar, and interspherulitic segregations, are observed with changing the MNM content. Avrami analysis of isothermal crystallization demonstrates that MNM enhances the bulk crystallization rate in the nanocomposites. Moreover, the non-integral values of Avrami exponent n between 2 and 4 with increasing crystallization temperature indicate the mixed growth and nucleation mechanisms. The analysis of secondary nucleation theory for neat PTT and the PTT nanocomposites exhibit the same regime transition of crystallization behaviour in which the classical transition temperatures of regime I to II and regime II to III take place at 488 K and 468 K, respectively. The growth rate of spherulites of the PTT nanocomposites is twofold larger than that of neat PTT in regime III, implying that MNM plays an effective role as a nucleating agent, since the addition of MNM enormously reduces the activation energy of nucleation, folding surface free energy and average work of chain folding for PTT nucleation. However, experimental results show that the MNM content below 1 wt% is the most effective for nucleation of PTT crystallization. 相似文献
13.
用差示扫描量热法(DSC)研究了聚羟基丁酸酯(PHB)的等温与非等温结晶动力学。采用Avrami方程分析了等温结晶动力学,Avrami指数n≈2,表明PHB以异相成核的二维平面晶体方式生长,等温结晶活化能为82.4 kJ/min。采用Jeziorny法和莫志深法分析了PHB的非等温结晶动力学,Avrami指数n≈3,表明PHB非等温结晶过程以异相成核的三维球晶方式生长。 相似文献
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15.
A novel modified Avrami model considering both primary and secondary crystallization has been presented to extract the kinetic
behavior of these two crystallization stages in nonisothermal crystallization process of polymers. Nonisothermal crystallization
kinetics of poly(trimethylene terephthalate)–poly(ethylene glycol) segmented copolyesters (PTEG) has been investigated by
differential scanning calorimetry. The crystallization rate constants and Avrami exponents at various cooling rates were obtained
from the analyses for neat PTEG and multiwalled carbon nanotube (MWNT) filled PTEG. Secondary crystallization displays a lower-dimensional
crystal growth compared with primary crystallization and the results of kinetics analyses are consistent with morphology study.
The MWNTs introduced into PTEG matrix take the role of effective nucleating agents during composites crystallization and can
expedite the process of crystallization of the matrix by providing more nucleation sites to the crystallizing phase. 相似文献
16.
用Monte Carlo方法模拟了聚氧化乙烯(PEO)在预先成核条件下的等温结晶过程,并用Avrami方程进行了结晶动力学处理.结果显示,Avrami方程能够成功地描述被模拟的PEO等温结晶的初期过程.随着结晶温度的升高,结晶速率和球晶的线生长速率减小,而Avrami指数值基本不变,都接近于3.采用热台偏光显微镜(HSPOM)实验证实了模拟实验模型和结果的正确性. 相似文献
17.
LLDPE/HDPE共混体系的结晶动力学及力学性能研究 总被引:1,自引:0,他引:1
对高密度聚乙烯和线性低密度聚乙烯共混体系的结晶动力学进行了研究,由差示扫描量热仪(DSC)测得的非等温的结晶温升曲线,分析研究共混比率对共结晶动力学参数的影响。实验发现,Avrami指数随着共混物组成的变化而有规律地变化。同时,通过偏光显微镜以及激光小角散射等实验方法,对结晶聚合物的晶体形成形态进行观察,验证了对于全部共混组成结晶结构增长的相似性,另一方面,利用拉伸试验等手段,对共混物的力学性能进 相似文献
18.
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. 相似文献
19.
Yingjin Wang Haixian Ren Wenya Liu Mingtao Run Hairong Zhang 《Journal of Materials Science》2009,44(1):170-178
The kinetics of thermal degradation of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) (PEN/PTT) blends with
different weight ratio were investigated by thermogravimetry analysis from ambient temperature to 800 °C in flowing nitrogen.
The kinetic parameters, including the activation energy E
a, the reaction order n, and the pre-exponential factor ln(Z), of the degradation of the PEN/PTT blends were evaluated by three single heating rate methods and advanced isoconversional
method developed by Vyazovkin. The three single heating rate methods used in this work include Friedman, Freeman–Carroll,
and Chang method. The effects of the heating rate, the calculation methods, and the content of the PEN component on the thermal
stability and degradation kinetic parameters of the PEN/PTT blends were systematically discussed. The PEN/PTT blends which
degraded in two distinct stages were stable under nitrogen, also, the maximum rate of weight loss increased linearly with
increasing of heating rate and decreased with increasing of PEN content. The obtained kinetics data suggested that the introduction
of PEN component increased the activation energy, enhanced the stability of the blend system, and affected the process of
degradation of PEN/PTT blend. 相似文献
20.
The crystallization morphologies, thermal behaviors and mechanical properties of PP/PTT/nanoclay blends nanocomposite fibers were investigated. Polypropylene/poly (trimethylene terephthalate) blends containing montmorillonite (MMT) were prepared using a twin screw extruder followed by fiber spinning process. The melt intercalation of PP and PPT alloys was carried out in the presence of a compatibilizer such as maleic anhydride-g-polyropylene (MAPP). The results show the improved adhesion between the phases and fine morphology of the dispersed phase. It has contributed to significant improvement in the properties and thermal stabilities of the final nanocomposite materials. A general understanding of how the morphology is likely to be related to the final properties of organically modified montmorillonite (OMMT)-incorporated PP/PTT blends is also described. 相似文献