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1.
Jiann‐Wen Huang Ya‐Lan Wen Chiun‐Chia Kang Mou‐Yung Yeh Shaw‐Bing Wen 《应用聚合物科学杂志》2008,109(5):3070-3079
Poly(ethylene‐octene) (POE), maleic anhydride grafted poly(ethylene‐octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE, PBT/mPOE, and PBT/mPOE/POE blends by a twin‐screw extruder. Observation by scanning electron microscopy revealed improved compatibility between PBT and POE in the presence of maleic anhydride groups. The melting behavior and isothermal crystallization kinetics of the blends were studied by wide‐angle X‐ray diffraction and differential scanning calorimeter; the kinetics data was delineated by kinetic models. The addition of POE or mPOE did not affect the melting behavior of PBT in samples quenched in water after blending in an extrude. Subsequent DSC scans of isothermally crystallized PBT and PBT blends exhibited two melting endotherms (TmI and TmII). TmI was the fusion of the crystals grown by normal primary crystallization and TmII was the melting peak of the most perfect crystals after reorganization. The dispersed second phase hindered the crystallization; on the other hand, the well dispersed phases with smaller size enhanced crystallization because of higher nucleation density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
2.
PET/PP共混合金结晶动力学研究 总被引：8，自引：0，他引：8
用GJY-3光学解偏振仪测定了PET、PP与PET/PP合金的结晶速度,并且在不同的结晶温度下比较了它们结晶速度的快慢。最后通过Avrami方程对PET/PP(3:1)合金进行了结晶动力学的研究。结果表明,其Avrmi指数为3。 相似文献
3.
Jiann‐Wen Huang Ya‐Lan Wen Chiun‐Chia Kang Mou‐Yung Yeh Shaw‐Bing Wen 《应用聚合物科学杂志》2008,107(1):583-592
Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (TmI and TmII). TmI was attributed to the melting of the crystals grown by normal primary crystallization, and TmII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well‐ dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen–Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
4.
The crystallization of isotactic polypropylene (iPP) in its blends with ethylene–propylene–diene terpolymer (EPDM), reinforced with different fibers, is described in this work. In particular, the effects of both the fibers and the EPDM on the crystallization kinetics and morphology of iPP are analyzed. The study was performed using differential scanning calorimetry (DSC) in dynamic and isothermal conditions and optical microscopy. It was found that all the fibers act as effective nucleant agents on iPP crystallization independently of the blend composition. The results obtained highlight the accelerating effect of the fibers and of the EPDM on the PP crystallization up to a certain EPDM percentage. The halftime of crystallization, τ1/2, and the overall crystallization rate, Kn, increase in the presence of all the fibers analyzed, showed the aramidic ones the most effective. The isothermal crystallization kinetics of ternary composites based on PP–EPDM blend matrices reinforced with different types of fibers can be modeled using the Avrami equation. On the other hand, the kinetic curves obtained under nonisothermal conditions provide a further confirmation of the nucleating action of the fibers on the PP crystallization. Optical polarizing microscopy was also used to investigate the effect of EPDM on the spherulite growth and the transcrystallinity phenomenon on the surface of the fibers. The results of such analysis showed that the transcrystallinity phenomenon is hindered at high rubber percentages. As in the case of the rate of crystallization, the highest proportion of transcrystallinity was observed in the presence of the aramidic fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1063–1074, 2001 相似文献
5.
将多聚磷酸铵(APP)、季戊四醇(PER)、三聚氰胺(MEL)及有机化蒙脱土(OMMT)于160℃下预混,制备了新型膨胀型阻燃剂(IFR).以PP为基材,IFR为阻燃剂,聚苯乙烯-丁二烯-苯乙烯(SBS)为增韧剂,马来酸酐接枝聚丙烯(PP-g-MAH)为增容剂,通过熔融挤出制备了新型阻燃PP(FRPP).通过XRD、P... 相似文献
6.
采用差示扫描量热仪(DSC)研究了石墨烯(RGO)/聚丙烯(PP)复合材料的等温结晶行为。结果表明:对于纯PP和RGO/PP复合材料,结晶温度(Tc)的提高将导致结晶速率(G1/2)变慢、绝对结晶度(Xc)提高;PP和RGO/PP复合材料的等温结晶在相当大的范围内符合Avrami方程;同纯PP相比,RGO/PP复合材料的G1/2相对增加,而结晶活化能相对减小,这意味着RGO对PP起到了外加成核剂的作用,促进了PP的结晶。 相似文献
7.
The melting behavior, nonisothermal crystallization behavior, and morphology of pure polypropylene (PP) and its blends were investigated by differential scanning calorimetry and polarized optical microscopy. The nonisothermal crystallization kinetics was analyzed using the Avrami equation modified by Jeziorny and the equation combining the Avrami and Ozawa method. The surface fold free energy and the effective activation energy for both PP and its blends were obtained by Hoffman‐Lauritzen theory and Vyazovkin's approach, respectively. The results showed that the presence of nylon 11 hindered the mobility of PP chains but accelerated the overall crystallization rate. The POM observation confirmed that the addition of nylon 11 decreased the spherulites size of PP matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
8.
9.
Yijing Nie Liangliang Qu Guangsu Huang Xiaoan Wang Gengsheng Weng Jinrong Wu 《应用聚合物科学杂志》2014,131(11)
Vulcanization gives birth to the nonuniformity of rubber network, the identification of which is the basis of improvement of performance of rubber products. We established a visco‐hyperelastic constitutive equation to reveal the quantitative distribution of the inhomogeneous network phases according to a three‐phase model. The cross‐linked network was assumed to be composed of the cross‐linking cluster, the low network chain density domain and the fluid‐like mass. The incorporation of clay with high specific surface area induced the effective uniformity of network structure by decreasing the content of the cross‐linking cluster and increasing that of the low network chain density domain. These structural variations were responsible for excellent mechanical properties and strong strain‐induced crystallization ability probed by the in situ synchrotron wide‐angle X‐ray diffraction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40324. 相似文献
10.
Weibing Xu Guodong Liang Wei Wang Shupei Tang Pingsheng He Wei‐Ping Pan 《应用聚合物科学杂志》2003,88(14):3093-3099
The nonisothermal crystallization kinetics of poly(propylene) (PP), PP–organic‐montmorillonite (Org‐MMT) composite, and PP–PP‐grafted maleic anhydride (PP‐g‐MAH)–Org‐MMT nanocomposites were investigated by differential scanning calorimetry (DSC) at various cooling rates. Avrami analysis modified by Jeziorny and a method developed by Mo well‐described the nonisothermal crystallization process of these samples. The difference in the exponent n between PP and composite (either PP–Org‐MMT or PP–PP‐g‐MAH–Org‐MMT) indicated that nonisothermal kinetic crystallization corresponded to tridimensional 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 composites, but the crystallization rate of composites was faster than that of PP at a given cooling rate. The method developed by Ozawa can also be applied to describe the nonisothermal crystallization process of PP, but did not describe that of composites. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The results showed that the activation energy of PP–Org‐MMT was much greater than that of PP, but the activation energy of PP–PP‐g‐MAH–Org‐MMT was close to that of pure PP. Overall, the results indicate that the addition of Org‐MMT and PP‐g‐MAH may accelerate the overall nonisothermal crystallization process of PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3093–3099, 2003 相似文献
11.
Eighty/twenty polypropylene (PP)/styrene–ethylene–butylene–styrene (SEBS) and 80/20 PP/maleated styrene–ethylene–butylene–styrene (SEBS‐g‐MA) blends reinforced with 30 wt % short glass fibers (SGFs) were prepared by extrusion and subsequent injection molding. The influence of the maleic anhydride (MA) functional group grafted to SEBS on the properties of SGF/SEBS/PP hybrid composites was studied. Tensile and impact tests showed that the SEBS‐g‐MA copolymer improved the yield strength and impact toughness of the hybrid composites. Extensive plastic deformation occurred at the matrix interface layer next to the fibers of the SGF/SEBS‐g‐MA/PP composites during impact testing. This was attributed to the MA functional group, which enhanced the adhesion between SEBS and SGF. Differential scanning calorimetry measurements indicated that SEBS promoted the crystallization of PP spherulites by acting as active nucleation sites. However, the MA functional group grafted to SEBS retarded the crystallization of PP. Finally, polarized optical microscopy observations confirmed the absence of transcrystallinity at the glass‐fiber surfaces of both SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrid composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1303–1311, 2002 相似文献
12.
Jiho Seo Xiaoshi Zhang Richard P. Schaake Alicyn M. Rhoades Ralph H. Colby 《Polymer Engineering and Science》2021,61(10):2416-2426
13.
Polypropylene/clay nanocomposites (PPCNs) were prepared via an in situ polymerization method with a Ziegler–Natta/clay compound catalyst in which the MgCl2/TiCl4 catalyst was embedded in the clay galleries. The wide‐angle X‐ray diffraction and transmission electron microscopy results showed that the clay particles were highly exfoliated in the polypropylene (PP) matrix. The nonisothermal crystallization kinetics of these PPCNs were investigated by differential scanning calorimetry at various cooling rates. The nucleation activity were calculated by Dobreva's method to demonstrate that the highly dispersed silicate layers acted as effective nucleating agents. The Avrami, Jeziorny, Ozawa, and Mo methods were used to describe the nonisothermal crystallization behavior of the PP and PPCNs. Various parameters of nonisothermal crystallization, such as the crystallization half‐time, crystallization rate constant, and the kinetic parameter F(t), reflected that the highly exfoliated silicate layers significantly accelerated the crystallization process because of its outstanding nucleation effect. The activation energy values of the PP and PPCNs determined by the Kissinger method increased with the addition of the nanosilicate layers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
14.
采用差示扫描量热仪（DSC）对含有不同含量超高分子量聚乙烯（UHMWPE）的聚丙烯进行测试和表征,采用Ozawa方法、莫志深方法和Kissinger方法分析了该体系的非等温结晶动力学。利用自行研制的超临界流体挤出发泡实验装置,对含有UHMWPE的PP进行了超临界二氧化碳挤出发泡实验研究。结果表明：超高分子量聚乙烯的加入降低了PP的结晶活化能,含有UHMWPE的PP在较高的温度下开始结晶,且由于超高分子量聚乙烯大分子链的存在,与聚丙烯分子链发生缠结,阻碍聚丙烯分子链排入晶格,降低了结晶速率,结晶温区拓宽,有利于聚丙烯挤出发泡成型;加入UHMWPE后,PP的发泡效果明显改善,泡孔平均直径减小,泡孔尺寸分布更加均匀,PE-UHMW的含量为5份时,表观密度达到0.038g/cm-3。 相似文献
15.
Joseph A. Sarver Jenna L. Sumey Michael L. Williams John P. Bishop David M. Dean Erdogan Kiran 《应用聚合物科学杂志》2018,135(7)
Poly(ethylene‐co‐vinyl acetate) (EVA‐25) and poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) (EVACO‐2410) and their blends with EVACO:EVA ratios of 80:20, 60:40, 40:60, and 20:80 were foamed using CO2. These foams are of interest for applications ranging from footwear to medical devices. Foaming experiments were carried out using 1 mm thick melt‐extruded films in CO2 at a range of pressures (100, 200, and 300 bar) and temperatures (30, 40, 50, and 60 °C). Foamability of the polymers was explored both under isothermal and gradient temperature conditions. Foams of EVACO‐2410 displayed high initial expansions followed by postfoaming relaxation and shrinkage while foams generated from EVA‐25 showed more dimensional stability. Blending EVACO‐2410 with EVA‐25 was explored as an approach to reduce postfoaming relaxation and shrinkage. The surfaces of the foamed samples displayed blistering that was linked to CO2 bubble entrapment and coalescence at the surface. Scanning electron micrographs of the foams generated from blends displayed distinct morphologies reflecting whether the sections were representing the machine‐ or cross‐machine direction of extruded films. In going from EVACO‐2410 to EVA‐25, the cell densities ranged from about 106 to 1010 cells/cm3. Foams with low bulk densities of about 0.11 g/cm3 could be generated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45841. 相似文献
16.
High-performance casting polyurethane elastomers (CPUe) were successfully synthesized by the reaction of polyurethane prepolymer (PUP) blocked by methyl ethyl ketone oxime (MEKO) with diamine chain extenders. The effects of blocking agent were systematically studied on the structures, thermal stabilities, mechanical properties, and processability of polyurethane. The addition of MEKO significantly improved the tensile strength and toughness. The maximum tensile strength was 35.6 MPa, and the maximum elongation at break was 1065%. The high strength and toughness were attributed to the fact that under mild reaction conditions, the reaction tended to extend the molecular chains, which indicated that the formation of long chains was conducive to the extension and self-reinforcement of chain segments. Crystallization and strong hydrogen bonds between molecules also led to low loss factor. This deblocking polymerization strategy solves the gel problem in the polymerization process, and provides a new idea for the preparation of CPU. 相似文献
17.
采用差示扫描量热（DSC）仪测试硅橡胶在温度变化过程中的热行为,并对硅橡胶的非等温结晶动力学和等温结晶动力学进行研究。结果表明：硅橡胶在升温过程中存在冷结晶现象;在降温过程中,结晶峰温度随着降温速率的增大向低温方向移动;等温结晶温度越低,结晶速率越快;Mo法和Avrami法分别适用于硅橡胶的非等温结晶动力学和等温结晶动力学分析。 相似文献
18.
玻璃析晶难易的一种新判据 总被引：21，自引：8，他引：21
提出了用析晶动力学参数k=vexp(-E/RT)作为判别玻璃析品难易的新方法。指出这一方法较目前沿用的用析晶活化能E作判据的方法更能准确地反映玻璃析晶的难易程度。经过严格推导,得出修正Johnson-Mehl-Avrami公式ln(T_p~2/α)=ln(E/R)+E/RT_(p-lnv)。从此式可以方便、准确地获取析晶活化能E和频率因子v,从而得出k=voxp(-E/RT)。对高钛钡系统玻璃及氟化物玻璃的研究证实了k参数较R参数更能反映玻璃析晶的难易。 相似文献
19.
Nonisothermal crystallization, melting behavior, and morphology of polypropylene (PP)/Easy processing polyethylene (EPPE) blends were studied by differential scanning alorimetry (DSC) and scanning electron microscope (SEM). The results showed that PP and EPPE are miscible, and there is no obvious phase separation in microphotographs of the blends. The modified Avrami analysis, Ozawa equation, and also Mo Z.S. method were used to analyze the nonisothermal crystallization kinetics of the blends. Values of Avrami exponent indicated the crystallization nucleation of the blends is homogeneous, the growth of spherulites is tridimensional, and crystallization mechanism of PP is not affected much by EPPE. The crystallization activation energy was estimated by Kissinger method. The result obtained from modified Avrami analysis, Mo Z.S. method, and Kissinger methods were well agreed. The addition of minor EPPE phase favored to decrease the overall crystallization rate of PP, showing some dilution effect of EPPE on PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
20.
The isothermal and nonisothermal crystallization behavior of Nylon 12 was investigated using differential scanning calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of Nylon 12, the Avrami exponent (n) determined and its relevance to crystal growth discussed and an activation energy for the process evaluated using an Arrhenius type expression. The Lauritzen and Hoffman analysis was used to examine the spherulitic growth process of the primary crystallization stage of Nylon 12. The surface‐free energy and work of chain folding were calculated using a procedure reported by Hoffmann and the work of chain folding per molecular fold (σ) and chain stiffness of Nylon 12 (q) was calculated and compared to values reported for Nylons 6,6 and 11. The Jeziorny modification of the Avrami analysis, Cazé and Chuah average Avrami parameter methods and Ozawa equation were used in an attempt to model the nonisothermal crystallization kinetics of Nylon 12. A combined Avrami and Ozawa treatment, described by Liu, was used to more accurately model the nonisothermal crystallization kinetics of Nylon 12. The activation energy for nonisothermal crystallization processes was determined using the Kissinger method for Nylon 12 and compared with values reported previously for Nylon 6,6 and Nylon 11. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献