Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends

The role of organically modified layered silicate as a compatibilizer for immiscible polystyrene (PS) with polypropylene (PP) or polypropylene grafted with maleic anhydride (PP-g-MA) blends was investigated. Scanning electron micrographs (SEM) revealed efficient mixing of the polymers in the presence of organically modified layered silicate. X-ray diffraction (XRD) patterns and transmission electron microscopic (TEM) observations showed that silicate layers were either intercalated or exfoliated, depending on their interactions with the polymer pair, and were located at the interface between the two polymers. The compatibilizing action of the organically modified layered silicate resulted in a decrease in interfacial tension and particle size and in a remarkable increase in mechanical properties of the modified immiscible blends.     

Nanocomposites of poly(vinylidene fluoride) with organically modified silicate

We report a study of the impact of cold crystallization on the structure of nanocomposites comprising poly(vinylidene fluoride) (PVDF) and Lucentite STN™ organically modified silicate (OMS). Nanocomposites were prepared from solution over a very wide composition range, from 0.01 to 20% OMS by weight. Thermal preparation involved cold crystallization at 145 °C of quenched, compression-molded plaques. Static and real-time wide and small angle X-ray scattering (WAXS, SAXS), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) were used to investigate the crystalline phase of PVDF. For OMS content greater than 0.50 wt%, WAXS studies show that that the silicate gallery spacing increases modestly in the nanocomposites compared to neat OMS film, indicating a level of polymer intercalation.Using Gaussian peak fitting of WAXS profiles, we determine that the composition range can be divided into three parts. First, for OMS greater than 0.5 wt%, alpha phase fraction, ?_alpha, is insignificant (?_alpha∼0-0.01). Second, at the intermediate range, for OMS between 0.5 wt% down to 0.025 wt%, beta phase dominates and the beta fraction, ?_beta, is related to alpha by ?_beta>?_alpha. Third, below 0.025 wt% OMS, alpha dominates and ?_alpha>?_beta. The ability of small amounts of OMS (≥0.025 wt%) to cause beta crystal domination is remarkable. Overall, crystallinity index (from the ratio of WAXS crystal peak area to total area) ranges from about 0.36 to 0.51 after cold crystallization. Real-time WAXS studies during heating of initially cold crystallized nanocomposites show that there is no inter-conversion between the alpha and beta phase PVDF crystals, where these crystals coexist at room temperature. While all samples showed a strong SAXS Bragg peak, indicating existence of two-phase lamellar stacks, the sample containing predominantly beta phase had poorly correlated lamellar stacks, compared to samples containing predominantly alpha phase.     

层状硅酸盐 /聚合物纳米复合材料的研究现状与前景

基于1996年以后的40余篇文献和作者的研究成果，综述了层状硅酸盐／聚合物纳米复合材料在制备技术、新品种、新性能、相关理论及应用等方面的最新研究进展，并总结出了以下观点：（1）粘土的有机化是制备纳米复合材料的第一关键要素，单体、预聚体、聚合物熔体与有机土的相容性是制备纳米复合材料的必要条件，外界剪切力可提供帮助；（2）剥离型结构最能体现层状硅酸盐／聚合物纳米复合材料的性能优势，是层状硅酸盐／聚合物纳米复合材料的制备方向；（3）聚合物熔体插层法为简单，是重要的发展方向，要形成剥离型结构，需要同时考虑热力学和动力学因素，基体或相容剂与层间环境的相容性要适中；（4）聚合物乳液共混共凝法有利于传统的制备方法，适合于具有乳液形成的聚合物；（5）在聚合物中原位生成硅酸盐片层的方法具有新意；（6）层状硅酸盐／聚合物纳米复合材料的主要特点是高刚性、高强度、高耐热性、高阻隔性、较好的阻燃性、质轻，目前，该的制备研究正向所有的聚合物品种扩展。汽车部件、包装材料将是层状硅酸盐／聚合物纳米复合材料先应用的两大领域；（7）层状硅酸盐／聚合物纳米复合材料的理论研究进展延慢。界面区状态以及结构－性能间的关系是理论研究的两个主题。     

The role of preconditioning on morphology development in layered silicate thermoset nanocomposites

The impact of preconditioning constituent materials on the morphology development of organically modified montmorillonite–epoxy nanocomposites is examined to determine the sensitivity of exfoliation to material conditions. In situ synchrotron small‐angle X‐ray scattering studies were performed to relate the initiation and levels of exfoliated morphologies with various silicate preconditioning processes. Significantly, exfoliation could be achieved in systems initially considered intercalated by preconditioning through epoxy–silicate mixture aging. The resulting morphologies lead to slightly improved toughness. Implications for nanocomposite morphology development models include the necessity of further investigation of the complexities of both local and global morphologies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 89–100, 2004     

改性层状结晶硅酸钠对钙镁离子交换的动力学研究

改性层状结晶硅酸钠（Al-SKS-6）是一种通过层状结晶硅酸钠（SKS-6）改性的性能优良的洗衣粉助剂。对其进行合成并表征,考察了pH、温度和时间对钙镁交换能力的影响及动力学研究。当pH在10左右时,钙离子和镁离子交换能力达到最大,分别为352 mg/g和405 mg/g,可满足洗衣粉的实际要求。Al-SKS-6对钙镁离子的交换是一个快速交换过程,在5 min时,钙镁离子交换能力可达到30 min时的90%,10 min基本可以达到交换平衡,交换过程符合二级动力学方程,且随着温度的升高,Al-SKS-6对钙镁离子交换能力增大。     

片层硅酸盐纳米复合聚氨酯橡胶的结构及性能

将聚四氢呋喃二醇和富羟基活性蒙脱土(HMMT)进行预混插层处理,然后与甲苯二异氰酸酯(TDI)进行反应,得到层状硅酸盐复合预聚体。随后预聚体与扩链剂(DMTDA)反应制备出聚氨酯橡胶/片层硅酸盐纳米复合材料。采用材料拉伸机、X射线衍射(XRD)、透射电镜 (TEM)、差示扫描量热仪 (DSC)和热失重分析仪 (TGA) 等检测设备对聚醚型聚氨酯脲的结构与性能进行分析。结果表明：当PMMT的质量百分含量在2％时,片层硅酸盐粒子在聚氨酯基体内分散较均匀,形成了以剥离型为主、插层型为辅的复合型结构,聚醚型聚氨酯脲复合材料的拉伸强度比纯PUU提高了21%,断裂伸长率提高了12%,PUU复合材料的玻璃化转变温度(Tg)提高了5.8℃,第一失重区分解温度和最高分解温度高出纯聚氨酯17.33 ℃和13.94 ℃。无机纳米片层硅酸盐粒子的存在,聚氨酯橡胶的强度、韧性和热稳定性均得到改善。     

Determination of the glass transition temperature of polymer/layered silicate nanocomposites from positron annihilation lifetime measurements

The glass transitions of acrylonitrile-butadiene rubber (NBR)/organoclay nanocomposites with various silicate contents were investigated using positron annihilation lifetime spectroscopy (PALS). The nanocomposites were prepared through melt intercalation of NBR with various concentrations of organoclay (OC30B) modified with the organic modifier, methyl tallow bis(2-hydroxyethyl) quaternary ammonium (MT2EtOH), i.e., Cloisite^® 30B. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the NBR/OC30B nanocomposites showed that the NBR chains were intercalated between the silicate layers, thereby increasing the gallery heights of the organosilicates. The glass transition temperature of NBR was determined using differential scanning calorimetry (DSC). However, it seemed to be very difficult to clearly resolve the very small differences in T_gs caused from various loading of nanosized silicate in NBR/OC30B nanocomposites. Hence, we performed positron annihilation lifetime spectroscopy (PALS) on NBR/OC30B nanocomposites containing various amounts of OC30B (1-10 wt%). Significant changes in the temperature dependencies of free volume parameters (i.e., lifetimes and intensities) were observed at the transition temperature, T_g,PALS, and the T_g,PALS values were found to increase with increasing organoclay content in the samples. These observations are consistent with PALS having a higher sensitivity in the detection of very small changes in free volume properties. The present findings thus highlight the usefulness of PALS for studying phase transition phenomena in polymeric materials with nanoscale structural variations.     

天然层状硅酸盐黏土合成分子筛研究进展

综述了用天然层状硅酸盐黏土合成分子筛的研究进展,分别对高岭土和膨润土的提纯、活化及用高岭土、膨润土合成分子筛进行了评述,并指出了用天然层状硅酸盐黏土合成分子筛时存在的问题和不足。     

Theory of competition between breakup and coalescence of droplets in flowing polymer blends

The Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.     

Influence of temperature-induced coalescence effects on co-continuous morphology in poly(ε-caprolactone)/polystyrene blends

This paper demonstrates that temperature-induced coalescence effects during melt mixing have a major influence on the concentration range of dual-phase continuity and an order of magnitude effect on the co-continuous microstructure phase size. A detailed study on the effect of temperature of blending on the morphology of immiscible poly(ε-caprolactone)/polystyrene blends is presented. Polycaprolactone (PCL) and polystyrene (PS) are blended in a batch mixer at 50 and 5 min for various temperatures. The continuity of the phases is obtained by selective extraction of each phase and the microstructure is analyzed using image analysis on SEM micrographs and mercury intrusion porosimetry. It is observed that the blending temperature has only a small effect on the morphology up to a PS or PCL composition of about 20 or 30%. However, beyond that composition the effect is dramatic. The microstructure of the 50/50 blend demonstrates a phase size (d_v) of 8.5 μm at 230 °C and 1.1 μm at 155 °C. Furthermore, the concentration range of co-continuity is broadened from 50-65%PS at 230 °C to 30-70%PS at 155 °C. The results at lower concentrations indicate that the temperature has little effect on the overall deformation/disintegration process, which appears to be due to compensating effects. For example, for PS in PCL, shear stress increases significantly at lower temperatures, but is counterbalanced by an increase in the viscosity ratio, elasticity of the phases and an increase in interfacial tension. Beyond a volume fraction of 0.30, the effect of temperature on coalescence plays a dominant role on the final morphology. It is shown in this paper that the observed morphology effects are controlled by the merging stage of coalescence. The data indicate the significant potential of mixing temperature as a tool for the morphology control of co-continuous polymer blends.     

改性层状硅酸钠LST-1性能及前配工艺研究

通过研究新型层状硅酸钠LST-1稳定性与配料工艺条件的关系，利用微波干燥模拟快速、高温喷粉过程，层硅保留率大于80％，与大生产喷粉结果基本一致。结果表明：LST-1在高温、快速干燥过程中性质稳定，适用于洗衣粉高塔喷粉前配料工艺。     

层状硅酸钠的制备及插层性能的研究进展

从晶体结构、制备工艺、插层改性和应用的角度,对层状硅酸钠的研究进行较全面阐述。介绍了层状硅酸钠存在的多种晶相及结构特点;指出了喷雾干燥结晶法或水热合成工艺在制备结晶层状硅酸钠中存在的技术问题;从反应类型的角度详细介绍了层状硅酸钠的插层改性技术和赋予改性层状硅酸钠丰富的功能性;分析了层状硅酸钠的不同晶相或改性技术在实际应用中的研究思路和存在问题,为层状硅酸钠的深度研究与开发指出方向。     

High performance nanocomposites of polyurethane elastomer and organically modified layered silicate

High performance nanocomposites comprising a polyurethane elastomer (PUE) and an organically modified layered silicate are prepared. These nanocomposites are based on poly(propylene glycol), 4,4′‐methylene bis(cyclohexyl isocyanate), 1,4‐butandiol, and organoclay. The tensile strength and strain at break for these novel PUE nanocomposites increases more than 150%, but the hardness remains unchanged. The fatigue properties are significantly improved. With 3 wt % organoclay, the fatigue properties are improved the most, which is important for the PU industry. The effects of the isocyanate index on the mechanical properties of the PUE nanocomposites are investigated. It is found that an isoyanate index of 1.10 results in the best improvement in stress and elongation at break. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3239–3243, 2003     

相容剂改性PE/PP共混物在滴灌带中的应用

介绍了相容剂改性PE/PP共混物在生产滴灌带中的应用情况,探讨了相容剂改性PE/PP共混体系的相容性机理,通过大量的实验找到了最佳配比方案。结果表明:以相容剂改性PE/PP共混物生产的滴灌带与普通滴灌带配方对比界面黏结性强,不分层剥离。改善和提高了PE/PP的相容性和产品力学性能。     

Mercapto‐modified copolymers in polymer blends. II. The compatibilization of NBR/EVA blends

Ethylene‐vinyl acetate (EVA) copolymer functionalized with mercapto groups (EVALSH) has been used as compatibilizing agent in nitrile rubber/EVA blends. The tensile strength and elongation at break of the system were measured as a function of the EVALSH content and blend composition. The compatibilization affects the mechanical properties of these blends. The highest improvement of the tensile strength has been achieved in the composition range corresponding to the co‐continuous phase morphology. The co‐continuity of these blends has been studied by both dissolution studies and scanning electron microscopy. The addition of EVALSH as an interfacial modifier did not change the region of co‐continuity but influences the percolation threshold for both dispersed nitrile rubber phase and dispersed EVA phase. From optical microscopy and differential scanning calorimetry analysis, it is possible to assume that the functionalized EVALSH copolymer affects the crystallization of the EVA phase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 193–202, 2001     

Transient and steady-state deformations and breakup of dispersed-phase droplets of immiscible polymer blends in steady shear flow

Transient and steady-state deformations and breakup of viscoelastic polystyrene droplets dispersed in viscoelastic high-density polyethylene matrices were observed in a simple steady shear flow between two transparent parallel disks. By separately varying the elasticities of the individual blend components, the matrix shear viscosity, and the viscosity ratio, their effects on the transient deformation, steady-state droplet size, and the breakup sequence were determined. After the startup of a steady shear flow, the viscoelastic droplet initially exhibits oscillations of its length in the flow direction, but eventually stretches preferentially in the vorticity direction. We find that at fixed capillary number, the oscillation amplitude decreases with increasing droplet elasticity, while the oscillation period depends primarily on, and increases with, the viscosity ratio. At steady-state, the droplet length along the vorticity direction increases with increasing capillary number, viscosity ratio, and droplet elasticity. Remarkably, at a viscosity ratio of unity, the droplets remain in a nearly undeformed state as the capillary number is varied between 2 and 8, apparently because under these conditions a tendency for the droplets to widen in the vorticity direction counteracts their tendency to stretch in the flow direction. When a critical capillary number, Ca_c, is exceeded, the droplet finally stretches in the vorticity direction and forms a string which becomes thinner and finally breaks up, provided that the droplet elasticity is sufficiently high. For a fixed matrix shear stress and droplet elasticity, the steady-state deformation along the vorticity direction and the critical capillary number for breakup both increase with increasing viscosity ratio.     

贮存稳定的LDPE/SBS共混物改性沥青的动态力学性能

利用应变控制流变仪对LDPE／SBS共混物改性沥青的动态力学性能进行了研究，考察了反应剂及其用量，LDPE／SBS共混物用量等对改性沥青高温性能的影响。结果表明，LDPE／SBS共混物的加入提高了原始沥青的高温模量，同时降低了其损耗角正切值，并且随着共混物用量的增加。沥青的高温性能也随之提高，温度敏感性也显著减弱。反应剂的加入使得沥青高温性能得到了更进一步的改善。改善程度随反应剂用量的增加而更加明显。     

Possible mechanism of interaction among the components in MAPP modified layered silicate PP nanocomposites

Model reactions were carried out with components frequently used for the preparation of intercalated or exfoliated polypropylene (PP) nanocomposites. The results prove that maleinated polypropylene (MAPP) can react chemically with the surfactant applied for the organophilization of the filler, if this latter contains active hydrogen groups. The reaction of hexadecylamine (HDA) and MAPP was detected by MALDI-TOF spectroscopy, DSC measurements and FTIR spectroscopy. Anhydride groups are consumed and mainly amide groups form in the reaction. The formation of cyclic imides could not be proved by the techniques used. MAPP reacts also with the surfactant adsorbed on the surface of the silicate in ionic form. On the other hand, N-cetylpyridinium chloride (CPCl) not containing active hydrogen atoms does not react with maleinated PP. Intercalated or exfoliated composites could be prepared from the silicate organophilized with HDA, while microcomposites formed from the filler treated with CPCl. Chemical reactions remove the surfactant from the surface of MMT and hydrogenated silicate sites are left behind. The high energy surface interacts either with the anhydride or the amide groups by dipole-dipole interactions. Even the unmodified polypropylene chains may be attached much stronger to the surface by London dispersion forces than to the silicate covered with aliphatic chains. Although the effect of competitive adsorption (MAPP, HDA) and mutual solubility of the components (PP, MAPP, surfactant, reaction products) cannot be neglected, chemical reactions play a crucial role in structure formation in PP nanocomposites containing a functionalized polymer. Direct interaction of the silicate surface and the functionalized polymer as well as the formation of hydrogen bridges seem to play a lesser role, but the relative influence of processes may change with the type of surfactant, functionalized polymer, surface coverage and processing conditions.     

Recent developments in the formation, characterization, and simulation of micron and nano-scale droplets of amorphous polymer blends and semi-crystalline polymers

Polymer micro- and nano-particles are fundamental to a number of modern technological applications, including polymer blends or alloys, biomaterials for drug delivery systems, electro-optic and luminescent devices, coatings, polymer powder impregnation of inorganic fibers in composites, and are also critical in polymer-supported heterogeneous catalysis. In this article, we review some of our recent progress in experimental and simulation methods for generating, characterizing, and modeling polymer micro- and nano-particles in a number of polymer and polymer blend systems. By using instrumentation developed for probing single fluorescent molecules in micron-sized liquid droplets, we have shown that polymer particles of nearly arbitrary size and composition can be made with a size dispersion that is ultimately limited by the chain length and number distribution within the droplets. Depending on the time scale for solvent evaporation—a tunable parameter in our experiments—phase separation of otherwise immiscible polymers can be avoided by confinement effects, producing homogeneous polymer blend micro- or nano-particles. These particles have tunable properties that can be controlled simply by adjusting the size of the particle, or the relative mass fractions of the polymer components in solution. Physical, optical, and mechanical properties of a variety of micro and nano-particles, differing in size and composition, have been examined using extensive classical molecular dynamics calculations in conjunction with experiments to gain deeper insights into fundamental nature of their structure, dynamics, and properties.     

Thermal and crystallization properties of PBT/ABAS blends

Blends of poly(butylene terephthalate) (PBT) with poly(acrylonitrile‐butyl acrylate‐styrene) (ABAS) were characterized by differential scanning calorimetry, infrared, thermogravimetric analysis, and wide‐angle X‐ray diffraction (WAXD) studies. Addition of ABAS polymer to PBT improved the thermal stability of PBT. Infrared studies showed that ABAS polymer chemically interacts with PBT. The crystallization behavior of PBT was modified in the presence of ABAS polymer. The ABAS polymer showed inappreciable effect on melting behavior of PBT but decreased its crystallization. WAXD studies showed some modification in PBT peaks and a peak with increasing intensity corresponding to the β‐crystalline form of PBT. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009