Infrared imaging of stress-crazing in rubber modified polystyrene

The plastic yield and fracture of rubber-modified polystyrene specimens under tensile load have been investigated at room temperature. The experimental procedure consisted of rapidly alternating measurements of transmitted and emitted infrared (IR) radiation from samples under tensile stress. The load-displacement data were simultaneously recorded. Both single-edge-notched and dog bone-shaped test coupons were studied. In each tensile test run, we observed a significant decrease of material transparency in the IR which occurred near the low yield point. A further increase in material deformation was accompanied by a substantial temperature increase. After material failure, the surface morphology of the test specimens in the vicinity of the crack was examined using atomic force microscopy (AFM). Our results are explained in the context of existing models of material crazing.     

Relationships among blending conditions,size of dispersed phase,and oil resistance in natural rubber and nitrile rubber blends

The rheological properties, morphology, and oil resistance in natural rubber and nitrile‐butadiene rubber (NR/NBR) blends are investigated as functions of the blending conditions. It is found that the Mooney viscosity of the blends depends more strongly on the blending time than the rotor speed. The size of the NR dispersed phase is approximately independent of the rotor speed, but it decreases with increasing blending time up to 25 min. With a further increase in the blending time the NR dispersed phase size decreases. The results for the relative tensile strength, which is an indicator of oil resistance, are in agreement with those of the blend morphology, indicating that the oil resistance in a 20/80 NR/NBR blend strongly depends on the phase morphology of the blend. The smaller the size of NR dispersed phase, the higher the blend resistance to oil. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1232–1237, 2001     

复合橡胶改性聚苯乙烯的结构与性能

研究了复合橡胶对高抗冲聚苯乙烯(HIPS)结构与性能的影响,并用透射电子显微镜对HIPS进行了表征。结果表明:低顺聚丁二烯橡胶(简称低顺橡胶)能增加HIPS橡胶相体积分数,使橡胶粒子形态分布更均匀;高顺聚丁二烯橡胶(简称高顺橡胶)有利于提高产品的韧性;低顺橡胶对HIPS弯曲强度和拉伸强度的增加贡献更大;采用高顺橡胶与低顺橡胶复合,能够协调HIPS的韧性、弯曲强度和拉伸强度。     

稀土掺杂炭黑填充型粉末天然橡胶(Ⅰ)制备与粒径分布

利用稀土(Ln)可与有机高分子化合物发生作用的性质,用稀土盐和炭黑以液相化学沉积法制备了稀土化合物掺杂炭黑(HAF-Ln),以增加发黑粒子的表面活性,并将其与天然胶乳(NRL)共混,采用凝聚共沉法制备稀土掺杂炭黑填充型粉末天然橡胶[P(NR/HAF-Ln)].透射电镜(TEM)、傅立叶转换红外光谱(FTIR)、等离子发射光谱(ICP)分析表明.稀土可全部沉积到炭黑粒子表面;稀土可有效减少炭黑粒子的团聚,促进炭黑在水中的稳定分散.稀土的加入可提高NR胶乳与乳化炭黑构成的粉末体系的成粉率.     

室温硫化聚苯乙烯接枝改性硅橡胶的性能研究

采用差示扫描量热分析(DSC)、动态热机械分析(DMTA)和热空气老化的方法,对室温硫化聚苯乙烯接枝改性硅橡胶(PS-PDMS)和硅橡胶(PDMS)的力学性能及耐高低温性能进行了对比研究。结果表明,接枝聚苯乙烯改性硅橡胶的力学性能显著提高,未补强硫化胶的拉伸强度达2.3MPa,白炭黑补强硫化胶的拉伸强度可达4.8MPa;PS-PDMS的结晶熔融峰和阻尼峰值低于PDMS,分别为5℃和8℃,耐低温性能优于PDMS,而耐高温性能远低于PDMS。     

基于超声衰减谱和相速度的颗粒粒径测量

超声波在颗粒两相体系中传播,包含了大量颗粒粒径信息,结合理论模型,通过提取超声波有效衰减谱和相速度谱分析了颗粒的粒径分布。实验中,对体积分数为10%的3种不同粒径分布的聚苯乙烯-水悬浊液,通过双样法和插入取代法（单样法）分别获得宽带超声波衰减谱与相速度谱,以ECAH模型为理论基础,并分别用Twomey、ORT和Davidon-Fletcher-Powell优化算法,反演出悬浊液颗粒粒径分布。测量结果与显微镜图像法结果进行对比,中位径误差小于15%,表明了利用超声波衰减谱法（UASA）和相速度谱法（UPVSA）测量悬浊液颗粒粒径分布的可行性与可靠性。     

The effect of rubber particle size on the mechanical properties of high-impact polystyrene

Resins having different rubber particle sizes were prepared by polymerizing impact polystyrene using different agitation rates but keeping all other parameters constant. Also, samples were made varying the amount and type of rubber and type of agitation. The impact and tensile properties of the prepared resins are studied in relation to existing theories of rubber particle reinforcement. The particle size dependence of energy absorption in impact (high intensity) and tensile (low intensity) testing appear to be opposite in nature. Energy absorption increases with increasing particle size in the high-intensity mode and decreases in low-intensity testing. Different mechanisms are, therefore, postulated to be operative in each of these two test methods.     

Quantitative prediction of particle size of dispersed phase in elastomer-plastic blends

In investigating the relationship between the particle size of the dispersed phase in a polymer blend and the physical properties of the resulting product, the effects of conditions of blending, viscosity difference, and volume fraction, etc., are usually observed and studied. This approach is uncertain since blending is a complex process. From a theoretical background similar to that of N. Tokita's, but using a different mathematical and experimental treatment, a complex factor composed of shear rate, apparent viscosity of the system, and volume fraction of the dispersed phase is proposed. This factor is found to provide a linear relation with the mean radius of dispersed particles as expressed by where R is the mean particle radius in the dispersed phase; S is shear rate of mixing;, V is apparent viscosity of the system; F is volume fraction of the dispersed phase; B is an experimental constant relating to breaking energy of the dispersed phase and interfacial tension; and A is also a constant relating to interfacial tension and the probability that a collision will result in a coalescence.     

基于图像分析方法的颗粒粒度测量

为了满足颗粒粒度测量的要求,研究开发了基于颗粒图像的颗粒体粒度测量系统。系统由硬件和软件两部分组成。硬件系统主要由图像采集和显示设备构成,可完成颗粒图像采集、存储和显示功能。软件系统由自主开发的基于Matlab环境的颗粒图像处理与分析程序组成,可完成颗粒图像的处理、颗粒粒度分析及分析结果显示等功能。颗粒测量结果表明,该系统完全可以满足颗粒粒度测量的要求,并具有测量精度高、效率高等特点。     

聚丙烯/聚苯乙烯共混熔纺中分散相的形态演变

采用共混熔融纺丝法制备聚丙烯(PP)/聚苯乙烯(PS)共混纤维,在纺程上不同位置收集纤维,研究了纺程上分散相PS的形态演变以及共混组成和拉伸比对形态变化的影响。结果表明:纺程上分散相由挤出丝中的球形变为卷绕丝中的椭球形;随着分散相含量的增加,挤出丝中分散相数目增多,分散相之间发生聚并,直径增加,纺丝过程中在拉伸应力作用下,分散相发生形变;随着拉伸比的增加,卷绕丝中分散相长径比增加,分布变宽。     

Toughness and morphology of radiation‐crosslinked natural rubber modified polystyrene

γ‐Radiation vulcanized natural rubber (RVNR)/phase transfer/suspension polymerization technique was used to prepare high‐impact polystyrene (HIPS) in bead form. The high notched Izod impact resistance of HIPS based on RVNR was observed and compared with that of unmodified PS. The impact resistance of HIPS based on RVNR was further enhanced by addition of 10% of polystyrene‐block‐polyisoprene‐block‐polystyrene copolymer. A mesh structure of all crosslinked rubber particles containing polystyrene and long crazes in HIPS were observed under electron microscopy. Copyright © 2003 Society of Chemical Industry     

Highly grafted polystyrene‐modified natural rubber as toughener for polystyrene

A polystyrene‐modified natural rubber (SNR) with 80% degree of grafting was evaluated against natural rubber (NR) in their blends with polystyrene (PS). The rubber loading of the PS‐SNR and PS‐NR blends was varied from 5 to 20% by volume. At 10–15% rubber loading, the PS‐SNR blends were found to be approximately 8–10% higher in tensile strength and 7–13% higher in Young's modulus than the PS‐NR blends. Over the range of rubber loading investigated, it was also observed that the PS‐SNR blends were 5–42 and 14–36% higher in flexural strength and flexural modulus, respectively. The most pronounced difference between the two blend systems is in their impact strength, where the former is about 55–230% higher than the latter. Relative to the pure PS, the PS‐NR and PS‐SNR blends are approximately 50–250 and 140‐1050% higher, respectively, in impact strength. Morphological observations, which are consistent with the relative tensile, flexural, and impact properties of the two systems, indicate that SNR is more compatible with PS than NR and more homogeneously dispersed in the PS matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1660–1665, 2004     

Development of dispersed phase size and its dependence on processing parameters

Through measurement of phase dimension via laser scattering, phase morphology development in immiscible blends of polyamide 12/poly(ethylene glycol) (PEG) with an extremely high viscosity ratio was investigated. The blends were prepared by melt blending in a batch mixer. The objective was to examine the influence of mixing time, rotor speed, as well as blending temperature on the size distribution of the minor phase. It is of interest that the breakup process of the dispersed PA 12 phase was observed for the blend systems even for extremely high viscosity ratios of ≤ 10²–10³. Mixing time had a significant effect on the development of dispersed phase size distribution. It was found that the bulk of particle size reduction took place very early in the mixing process, and very small droplets with a diameter of 0.1–10 μm were produced. The number of small particles then decreased, resulting in a larger average particle size. With further prolonged mixing, the particle size levels off. The particle size and its distribution were also found to be sensitive to the rotor speed. The average particle size decreased with increased rotor speed. The effect of blending temperature on size and size distribution, which has seldom been studied, was also examined in this work. When the blending temperature altered from 190°C to 220°C, the size and its distribution of the dispersed phase varied considerably, and the change of viscosity ratio was found to be the key factor affecting the dispersed phase size. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3201–3211, 2006     

大型喷雾粒径分布的图像法测量

雾化技术在能源、化工等领域应用广泛,研究雾化机理和优化雾化喷嘴性能的前提是对其雾化液滴尺寸及粒度分布进行准确有效的测量和表征。目前常用的雾化液滴粒度测量技术,如基于光散射或衍射原理的激光粒度仪和相位多普勒分析仪等,能够较准确地测量粒径分布比较窄、最大粒度在2000 μm以下的喷雾,但对含特大颗粒且粒径分布很宽的喷雾,往往难以得到可靠结果甚至不可能进行测量。本文提出了用图像法测量这类大流量喷雾,构建了图像法测量系统,编写了图像处理程序,经标定实验后,采用该系统对某喷嘴喷雾液滴粒径分布及规律进行了测量研究。研究结果表明图像法可用于大型喷雾液滴粒度及分布的测量。     

废胶粉改性沥青的储存过程及胶粉粒径的影响

为研究存储过程中废轮胎胶粉改性沥青(CRMA)的性能下降问题,对期间CRMA流变学性能及胶粉(CR)的变化进行了考察。动态剪切流变(DSR)结果表明,CR网络结构的破坏使得CRMA的复数模量减小,相位角增大。CRMA中的残余CR的热重及扫描电镜的分析结果揭示了CR网络结构的降解是由表及里的持续过程。不同粒径CR改性的CRMA的存储实验表明,小CR粒径的CRMA制备完成的即时性能最好,而CR粒径较大的CRMA存储前后的性能变化最小。     

Characterization of rubber particle size distribution of high-impact polystyrene using an image analysis method

Accurate characterization of high-impact polystyrene (HIPS) rubber particle size distribution has been achieved using an automatic image analysis system. The new method involves preparation of a microscope slide consisting of a dilute suspension of HIPS particles in a polymer matrix. Images of silhouetted rubber particles of true diameter are obtained using an image processor and particle size calculations can be made with a minimum of editing of the binary image. The new method provides measurement of true rubber particle diameters because the particles in the prepared slide are not swollen by any solvent.     

Characterization of the phase structure of an amine cured rubber modified epoxy

The phase structure of an amine cured, rubber-modified epoxy was characterized. The sharpness of the interface between the matrix and the dispersed phase, the volume fraction of the dispersed phase, the distribution of particle sizes, and the concentration of epoxy in the dispersed phase were determined. Scanning transmission electron microscopy coupled with energy dispersive X-ray analysis revealed that the interface width is less than 500 Å. Variation in the fraction of mobile hydrogens with temperature determined by nuclear magnetic resonance indicated that a small fraction of segments participated in mixing at the interface. Differential scanning calorimetry and nuclear magnetic resonance showed that the volume fraction of the dispersed phase equalled that predicted by assuming all of the rubber plus the epoxy monomer units bonded directly to the rubber precipitates. The distribution of particles greater than 0.1 μm in diameter was measured, and the average diameter of these particles was found to be 0.8 μm. This distribution accounted for approximately 50% of the dispersed phase. The epoxy concentration in the dispersed phase was determined using ¹³C nuclear magnetic resonance spectroscopy. This concentration was found to be less than that predicted if all the epoxy monomer units attached to the rubber molecules were present in the dispersed phase.     

Characterization of rubber particle size distribution of high-impact polystyrene using low-angle laser light scattering

A new application of low-angle laser light scattering has led to a new instrument capable of characterizing the rubber particle size distribution of high-impact polystyrene (HIPS) containing particles as small as 0.1 μ. Rubber particle size distributions of several HIPS resins have been characterized, and the particle size ranking of resins using light scattering parallels the ranking of resins using photomicroscopy. Several solvents have been employed to suspend the HIPS rubber particles for the scattering determination. Swelling of the rubber phase has been found to be relatively insensitive to variations in rubber phase crosslinking when methyl ethyl ketone is used to suspend the rubber particles. Particle swelling in methyl ethyl ketone does not detract from the usefulness of the light scattering method for HIPS rubber particle size characterization.     

Effect of the dispersed phase fraction on particle size in blends with high viscosity ratio

It has been reported that for polymer blends with high viscosity ratio (>1), the size of the dispersed particles decreases with increasing volume fraction of the dispersed phase. In order to explain this effect, an equation was derived for the affine deformation of an imaginary plane of the dispersed phase in stratified two‐phase steady, simple, shear flow. The model predicts that for viscosity ratio >1, the deformation rate increases with volume fraction of the dispersed phase, and the shear stress also increases, leading to an increase of the breakup time. Therefore, the total deformation of the dispersed phase, before breakup, increases with increase of volume fraction, resulting in a decrease of the size of the dispersed phase particles. Accordingly, one can expect that in industrial mixers, the particle size of the blends should decrease as the volume fraction increases, if coalescence is suppressed. Experiments were carried out in a Haake batch mixer, using polyethylene/polyamide‐6 blends compatibilized by adding maleic anhydride grafted polyethylene. Particle size decreased up to 20 wt% polyamide‐6, at 100, 150, and 200 RPM, and increased between 20 and 30 wt%. The decrease of the particle size is mainly due to increased deformation of the dispersed phase. The increase of the particle size above 20 wt% is due to coalescence at high fractions.