界面张力对高分子共混物梯度相形态形成的影响研究

研究了界面张力对ＰＰ／ＥＶＡ共混体系梯度相形态形成的影响。首先将ＥＶＡｃ进行皂化反应得到一系列－ＯＨ基含量不同即极性不同的ＥＶＡ，然后将这些ＥＶＡ分别与ＰＰ共混从而得到一系列相界面张力不同的共混物。说明通过对共混物相界面张力的调整，可以达到随意控制梯度相形态形成速度的目的。     

温度梯度引起的聚合物共混物梯度相形态的研究

研究了两相不相容聚合物共混物在静态退火时,由温度梯度引起的分散相尺寸的空间分布梯度相形态,讨论了分散相体积分数和两相之间界面张力对梯度形态形成的影响.应用接触凝聚模型计算了在温度梯度作用下,分散相粒子的粗化过程.计算结果表明,界面张力越大,或者分散相体积分数越大,形成的梯度相形态越明显;并且在温度梯度存在下,分散相粒子粗化的速度加快.     

高分子共混物梯度相结构形成过程中的界面效应

通过在高分子共混物内部引入不同的第三相界面,系统地研究了退火热处理条件下该界面对于共混物梯度相形态形成的影响.对具有一定初始粒径的共混物体系或初始近似为均相的共混体系,在第三相界面的诱导下,均能形成梯度相形态.探讨了诱导界面间距与体系相结构的关系.结果表明,当两个诱导界面间距小于所生成梯度层厚度的两倍时,梯度结构趋于交叠.继续减小诱导界面间距,则梯度结构趋于消失,诱导界面间共混物中分散相粒子快速长大,界面的诱导作用遍布整个样片,证实了我们所提出的“高分子共混物中二维条件下界面诱导加速分散相粒子粗化凝聚”的结论.     

高分子共混物梯度的相结构形成过程中的界面效应

通过在高分子共混物内部引入不同的第三相界面,系统地研究了退火热处理条件下界面对于共混物梯度相形态形成的影响,对具有一定初始粒径的共混物体系或初始近似为均相的共混体系,在第三相界面的诱导下,均能形成梯度相形态。探讨了诱导界面间距与体系相结构的关系。结果表明,当两个诱导界面间距小于所生成梯度层厚度的两倍时,梯度结构趋于交叠。继续减小透导界面间距,则梯度结构趋于消失,诱导界面间共混物中分散相粒子快速长大,界面的诱导作用遍布整个样片,证实了我们所提出的“高分子共混物中二维条件下界面诱导加速分散相粒子粗化凝聚”的结论。     

相界面张力对两相聚合物熔体中分散相粒子粗化速度的影响研究

多相高分子共混物熔体中微区的发展机理,决定着体系的最终相结构．所以研究共混物熔体或溶液中的微区聚结机理已越来越显得重要和必要．作者先前的研究工作表明［１～６］,通过简单共混得到的均匀共混体系（如ＰＰ／ＥＶＡｃ）,在一定的退火热处理条件下,会自组织形成梯度相结构,即分散相粒子尺寸及其浓度从样品中心到表面逐渐增大．作者认为,这一结构的形成主要与基板对共混体系粗化过程的影响作用有关．初步认为是由于体系分散相聚结过程中,共混组分对基板的选择性浸润析出而导致了这种特殊的结构,亦可称为基板诱导相结构的形成．…     

基板界面对ＰＳ／ＰＭＭＡ共涨物薄膜相逆转组成比的影响

近年来高分子共混体系中的界面,表面效应逐渐引起了越来越多研究者的兴越,人们发现,当共混物薄膜厚度减至一定程度时,聚合物共混物薄膜中的相形态,相容性和相分离动力学与本体中有较大的不同^[1~3].基板界面作用对共混薄膜体的热力学,动力学行为产生很大的影响,我们以往的研究^[4,5]也发现,ＰＰ／ＥＶＡc(70/3０）共混体系退火过程中,基板界面（如玻璃）作用可大大加速分散相（ＥＶＡc)粒子的粗化凝聚过程,本研究用聚甲基丙烯酸甲酯和聚苯乙烯共混物押氢呋喃深液在不同在板介质（如玻璃基板,ＰＰ基板）上成膜,用相产左显微镜观测了膜的相形态变化并确定共混和的的相逆转区域,用界面张力和共混物薄膜上下表面的ＡＴＲ－ＦＴＩＲ实验结果探讨了成膜过程中的基板界面效应对相逆转区域的影响。     

POM／EVA共混物的研究

用力学测试、扫描电镜（ＳＥＭ）、热分析（ＤＳＣ）等手段研究了聚甲醛（ＰＯＭ）与乙烯－醋酸乙烯酯共聚物（ＥＶＡ）共混物（ＰＯＭ／ＥＶＡ）的力学性能及其微同形态；用聚甲醛与马来酸二丁酯（ＤＢＭ）的接枝物（ＰＯＭ－ｇ－ＤＢＭ）作相溶剂，能改变共的两相间的粘结力，从而提出了共混物的力学性能，ＳＥＭ观察表明接枝物的加入改变了ＰＯＭ／ＥＶＡ共混物的断裂方式，微观形态及结晶性能，对其热性能影响不大；通过改变ＰＯ     

界面粘结对聚氯乙烯/丁腈橡胶共混物脆韧转变的影响

应用丙烯腈（ＡＮ）含量不同的丁腈橡胶（ＮＢＲ）与聚氯乙烯（ＰＶＣ）共混，研究了界面粘结对ＰＶＣ／ＮＢＲ共混物脆韧转变的影响．结果表明：当基体层度Ｔ相等时，过强的界面粘结，使ＰＶＣ／ＮＢＲ共混物的冲击强度降低，并且其产生脆韧转变的临界基体层厚度Ｔｃ减小．界面粘结对于聚合物共混物的增韧行为具有直接的影响．损伤区分析给出：随着界面粘结强度增大，空洞化过程受阻，减弱能量的耗散，并且不利于诱导剪切屈服损伤的产生，因而不利于增韧；但是界面粘强度过小，意味着共混物的相容性太差，致使分散相粒径过大，也不利于增韧．所以对增韧来讲，共混物的界面粘结强度存在一个最佳范围．     

界面张力在基板诱导共混物分散相粒子粗化生长加速现象中的作用

通过相差显微镜和计算机图像处理来研究两相聚合物体系的粗化过程 .将具有不同聚比的乙烯 聚醋酸乙烯酯 (EVAc)共聚物与聚丙烯 (PP)共混 ,制备不同相界面张力的系列共混物薄膜 .观察了在玻璃基板的作用下 ,不同界面张力体系的分散相粒子粗化行为 ,发现界面张力在约 0 4 8·1 0 - 5N cm以上的体系中分散相粒子的粗化有明显的加速现象 ,粒子体积生长与时间关系的指数大于 1 0 ;而两相界面张力较低的情况下 ,选择具有不同表面极性的基板对同一体系试验 ,我们均未发现有粗化加速现象产生 ,且采用不同基板之间的试验结果差异很小 ,亦即当高分子共混物的相界面张力大于一定值时 ,仅与基板存在有关 ,粒子的粗化行为被加速     

PEO／EVA共混物的结构研究

ＰＥＯ以分散相形式存在于ＰＥＯ／ＥＶＡ共混物中，且具有部分相容性。Ｘ－射线衍射谱表明ＥＶＡ含有较强的ＰＥ衍射峰；ＰＥＯ／ＥＶＡ共混物既表现出ＰＥ的衍射峰也含有ＰＥＯ的晶面反射。随着ＰＥＯ的Ｍｎ的增加，ＰＥＯ／ＥＶＡ的Ｗｃ、ｘ增大且于时获得最大值：ＰＥ０／ＥＶＡ的Ｗｃ、ｘ值比纯ＰＥＯ的Ｗｃ、ｘ明显降低。     

COALESCENCE INDUCED GRADIENT MORPHOLOGY NEAR A WALL IN PHASE SEPARATED POLYMER BLENDS DURING QUIESCENT ANNEALING

A fast coalescence mechanism is proposed to account for the wall effect on the formation of gradient morphologyin phase separated polymer blends during quiescent annealing. The existence of solid wall with high polarity is believed tochange the potential field around the dispersed pedicles near the wall. This additional potential interaction between the solidwall and the dispersed particles causes faster coalescence of the dispersed particles near the wall than in the bulk. Thegradient phase morphology thus formed can be predicted by combining the wall-particle interaction and the touch-coalescence mechanism. The effect of interfacial tension on the gradient morphology is also discussed.     

The relative role of coalescence and interfacial tension in controlling dispersed phase size reduction during the compatibilization of polyethylene terephthalate/polypropylene blends

The breaking thread and the sessile drop methods have been used to evaluate the interfacial tension between a polypropylene (PP) and a polyethylene-terephthalate (PET). An excellent correlation was found between the two. The breaking thread technique was then used to evaluate the interfacial tension of these blends at various levels of a styrene-ethylene butylene-styrene grafted with maleic anhydride (SEBS-g-MA) compatibilizer. In order to evaluate the relative roles of coalescence and interfacial tension in controlling dispersed phase size reduction during compatibilization, the morphology of PP/PET 1/99 and 10/90 blends compatibilized by a SEBS-g-MA were studied and compared. The samples were prepared in a Brabender mixer. For the 10/90 blend, the addition of the compatibilizer leads to a typical emulsification curve, and a decrease in dispersed phase size of 3.4 times is observed. For the 1/99 blend, a 1.7 times reduction in particle size is observed. In the latter case, this decrease can only be attributed to the decrease of the interfacial tension. It is evident from these results that the drop in particle size for the 10/90 PP/PET blend after compatibilization is almost equally due to diminished coalescence and interfacial tension reduction. These results were corroborated with the interfacial tension data in the presence of the copolymer. A direct relationship between the drop in dispersed phase size for the 1/99 PP/PET blend and the interfacial tension reduction was found for this predominantly shear mixing device. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2271–2280, 1997     

Morphology of PC/SAN blends: effect of reactive compatibilization,SAN concentration,processing, and viscosity ratio

This article examines the effects of dispersed phase concentration, processing apparatus, viscosity ratio, and interfacial compatibilization using an SAN–amine compatibilizer on the morphology of blends of bisphenol A–polycarbonate (PC) with styrene–acrylonitrile (SAN) copolymers. For uncompatibilized blends, the dispersed phase particle size increased significantly with SAN concentration, and was found to exhibit a minimum at a viscosity ratio of approximately 0.35 for a fixed concentration of 30% SAN in the blend. Although the morphology of uncompatibilized PC/SAN blends mixed in a Brabender mixer, single‐ and twin‐screw extruders were quite similar, the twin‐screw extruder produced significantly finer morphologies in blends containing SAN–amine. The average particle size for blends compatibilized with the SAN–amine polymer was approximately half that of uncompatibilized blends and was relatively independent of viscosity ratio and dispersed phase composition. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 71–82, 1999     

Design of Blends with an Extremely Low Viscosity Ratio between the Dispersed and Continuous Phases. Dependence of the Dispersed Phase Size on the Processing Parameters

Summary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components.     

Morphology and properties of isotactic polypropylene/poly(ethylene terephthalate) in situ microfibrillar reinforced blends: Influence of viscosity ratio

In situ microfibrillar reinforced blends based on blends of isotactic polypropylene (iPP) and poly(ethylene terephthalate) (PET) were successfully prepared by a “slit extrusion-hot stretching-quenching” process. Four types of iPP with different apparent viscosity were utilized to investigate the effect of viscosity ratio on the morphology and mechanical properties of PET/iPP microfibrillar blend. The morphological observation shows that the viscosity ratio is closely associated to the size of dispersed phase droplets in the original blends, and accordingly greatly affects the microfibrillation of PET. Lower viscosity ratio is favorable to formation of smaller and more uniform dispersed phase particles, thus leading to finer microfibrils with narrower diameter distribution. Addition of a compatibilizer, poly propylene-grafted-glycidyl methacrylate (PP-g-GMA), can increase the viscosity ratio and decrease the interfacial tension between PET and iPP, which tends to decrease the size of PET phase in the unstretched blends. After stretched, the aspect ratio of PET microfibrils in the compatibilized blends is considerably reduced compared to the uncompatibilized ones. The lower viscosity ratio brought out higher mechanical properties of the microfibrillar blends. Compared to the uncompatibilized microfibrillar blends, the tensile, flexural strength and impact toughness of the compatibilized ones are all improved.     

Influence of size reduction of crosslinked rubber particles on phase interface in dynamically vulcanized poly (vinylidene fluoride)/silicone rubber blends

In this paper, the influence of rubber particle size on the phase interface in dynamically vulcanized poly(vinylidene fluoride)/silicone rubber (PVDF/SR) blends without any modifier is discussed through the studies of specific surface of crosslinked SR particles, crystallization behavior and crystal morphology of the PVDF phase, interfacial crystallization, melt rheological behavior and mechanical properties of blends. A series of decreased average particle size was successfully obtained by control of rotor rate. It was found that properly high rotor rate helped to achieve a reduced particle size and a narrowing size distribution. The reduced SR particle size enlarged the PVDF/SR interface which has a positive effect on the interfacial crystallization and the melt rheological behavior. At high SR content, the negative effect of the poor interface interactions played the dominate role on determining the mechanical properties. However, the blend exhibited a unique stiffness-toughness balance at the PVDF/SR = 90/10. We hope that the present study could help to lay a scientific foundation for further design of a useful PVDF/SR blend with promoted properties to partly replace the high-cost synthetic fluorosilicone materials.