Homogenization in mechanical mixing involving polyvinyl chloride. I. Skin removal and breakdown of PVC particulate structure during mixing with miscible polymer

Suspension-polymerized polyvinyl chloride (PVC) is a powder consisting of particles 100 ～ 150 μm in diameter, called grains. The grains have a unique hierarchical structure consisting of a skin and internal tight agglomerates of about 10 μm diameter. The agglomerate consists of primary particles of about 1 μm diameter, which in turn consist of domains of about 0.1 μm. The domain is composed of microdomains of about 10 nm. In this work, mechanical mixing of PVC with a miscible polymer, nitrile rubber containing 30% acrylonitrile (NBR-30), was conducted in an internal mixer and the significant events in the mixing period of 150 sec were examined with scanning and transmission electron microcopes. The process of mixing was very different from that of two amorphous polymers in that the skins of the PVC grains were first peeled off and then the agglomerates were broken down to the subsequent smaller particles, eventually becoming microdomains dispersed in the rubber. The NBR was found to be an effective medium for the breakdown of the particulate structure of PVC. The high storage modulus of NBR-30 and the strong adhesion due to the molecular mixing at the interface of the two polymers effectively transmitted the stress from the machine to the PVC particles. Also, the viscous heating resulting from the high loss modulus of NBR-30 brought about a temperature rise which weakened the interparticulate bonds and melted some microcrystallites of PVC, thereby facilitaing the disintegration of the PVC particles.     

Stress whitening and yielding mechanism of rubber-modified PVC

Structure-property relationships were investigated for blends of grafted rubbery polymers with PVC. Increasing grafting levels as well as higher blending temperatures improved the dispersion of the graft copolymers in PVC, lowered the impact strength, and reduced stress whitening. Presuming a mechanistic connection between impact strength and stress whitening, the causes of whitening due to mechanical deformations were studied by a variety of methods. Electron microscopy of stress-whitened zones revealed a large number of cavities formed by rupture of rubber particles, which correlated with the extent of whitening. Density measurements and quantitative evaluations of the volume increase due to the cavities in the stress-whitened zones were in agreement and proved that crazing did not significantly contribute to either volume dilation or stress-whitening. Light scattering studies indicated the existence of reflecting planes oriented at an angle of 55 to 64° to the direction of the applied stress, depending on the particle size of the modifier in the blends. The orientation of the scattered light could not be attributed to the cavities in the rubber particles because of their smallness (< 0.5 μm). An explanation was finally found by transmission light microscopy at various resolving powers. It was demonstrated that the ruptured rubber particles were accumulated in bands which corresponded to shear bands in the PVC matrix. Thus it was concluded that the rubber particles improved the impact strength of PVC by initiating shear bands and not by generating crazes.     

Electrostatic Charge Measurement and Charge Neutralization of Fine Aerosol Particles during the Generation Process

An aerosol charge analyzer has been constructed to measure the charge distribution of NaCl particles generated in the laboratory. A radioactive electrostatic charge neutralizer utilizing Po‐210 was used to neutralize the electrostatic charge of the particles. The atomization technique was used to generate NaCl particles with diameters of 0.2 to 0.8 μm, while the evaporation and condensation method was adopted to generate particles of 0.01 to 0.2 μm in diameter. The experimental data demonstrates that the absolute average particle charge depends on the particle diameter, and is higher than that calculated by the Boltzmann charge equilibrium for particles within the range of 0.2 to 0.8 μm. The charge increases with decreasing NaCl concentration. When these particles are neutralized using the Po‐210 neutralizer, it is found that the electrostatic charge reaches the Boltzmann charge equilibrium. For 0.01 to 0.2 μm NaCl particles generated using the evaporation and condensation method, test results show that the absolute average particle charge is higher than that calculated by the Boltzmann charge equilibrium for particles larger than 0.03 to 0.05 μm in diameter, while it is lower than that predicted by the Fuchs theory [1], for particles smaller than 0.03 to 0.05 μm. However, after charge neutralization, particles with diameter above 0.05 μm reach the Boltzmann charge equilibrium condition, and the charges for particles with diameters of 0.010 to 0.05 μm, agree well with Fuchs' theory.     

S-shaped current–voltage characteristics of polymer composite films containing graphene and graphene oxide particles

The resistive switching effects in composite films containing polyfunctional polymers, such as derivatives of carbazole (PVK), fluorene (PFD), and polyvinyl chloride (PVC), and also graphene particles (Gr) and graphene oxide (GO), the concentration of which in the polymer matrices varied in the range from 1 to 3 wt % corresponding to the percolation threshold in such systems, have been studied. The analysis of the elemental composition of the investigated composites by means of X-ray photoelectron spectroscopy have shown that the oxidation degree of Gr in GO is about 9 to 10%. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK (PFD; PVC): Gr (GO)/ITO/PET structures, where ITO is indium tin oxide, and PET is poly(ethylene terephthalate), with the switching time, t, in the range from 1 to 30 μs. The observed effects are attributed to the influence of redox reactions taking place on the Gr and GO particles enclosed in the polymer matrix, and the additional influence of thermomechanical properties of the polymer constituent of the matrix.

     

Particle Size Classification of Glass Particles Using Aerodynamic Jet Vectoring

An experimental demonstration of a new, non‐contact particle characterization technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented. AVPS uses secondary blowing and suction control flows–flows that are a fraction of the jet flow rate–to sharply change the direction of a planar, particle‐laden jet. As the jet is vectored, particles present in the flow experience a resultant drag force, dependent upon their size, that balances inertia. Since this balance determines the particle's trajectory, vectoring the flow leads to a separation of particles downstream. This simple, low‐pressure‐drop sorting technique classifies particles with less risk of damage or contamination than currently available sorting devices. Particles from 10–40 μm and 2.5 times the density of water have been sorted to an accuracy of 1.5 μm. Sorting of heavy particles such as these is accomplished at very low speeds, reducing the tendency of damage to the particles. Lighter particles are sorted at higher speeds. Particles from 5–40 μm and 0.6 times the density of water were sorted to an accuracy of 6.6 μm. AVPS is also shown to be capable of concentrating aerosols. Our measurements indicate that an air sample containing water‐like particles can be concentrated by a factor of 10 using AVPS.     

压缩CO2中聚合物玻璃化转变温度的实验研究

 玻璃化转变温度（T_g）是聚合物重要的特性参数，压缩CO₂环境中聚合物的玻璃化转变温度的测定，更是超临界流体技术在聚合物科学领域中成功应用的前提条件。根据蠕变柔量实验原理，自建一套测定高压环境下玻璃化转变温度的实验装置。利用该装置对聚对苯二甲酸乙二醇酯（PET）、聚苯乙烯（PS）、聚氯乙烯（PVC）以及聚甲基丙烯酸甲酯（PMMA）在大气中及压缩CO₂环境中的T_g进行了测定。设定实验的平衡吸附温度为室温，平衡吸附压力范围分别为：PET，0~3.5 MPa；PS，0~11.0 MPa；PVC，0~9.0 MPa；PMMA，0~4.5 MPa。在大气中测定的结果与文献中的结果相吻合，表明所设计的实验方法及实验装置是可靠并有效的，可用于高压环境下聚合物的玻璃化转变温度的测定。从压缩CO₂中的聚合物T_g测定结果可以看出，CO₂对聚合物具有较明显的溶胀、增塑作用，可显著降低聚合物的T_g。     

Diffusion of 1,2,3-Benzotriazole as a Volatile Corrosion Inhibitor through Common Polymer Films Using the Molecular Dynamics Simulation Method

Diffusion of 1,2,3-benzotriazole (BT), as one of the volatile corrosion inhibitors (VCI) for copper and steel, through several polymers was investigated using molecular dynamics simulation (MD). MD were performed by employing the COMPASS force field to estimate the diffusivity of BT through polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and Nylon 6 as potential hosts for anticorrosion film packaging purposes. The diffusion coefficients (D) of BT in these polymers were calculated by constructing an amorphous cell, each containing BT and one of these polymers. After constructing the cell, a molecular dynamics simulation was performed to calculate the mean square displacement of the BT molecule. Simulation results showed that BT can diffuse through PVC easier than the other polymers. Among these hosts the Nylon 6 had the lowest D value, implying that this polymer can maintain BT for a long time. The temperature dependence of diffusion through PE, as the most common VCI film, was studied and the activation energy (Q_d) and pre-exponential diffusion coefficient (D₀) in Arrhenius equation were calculated.     

A Pulsed Field Gradient NMR Technique for the Determination of the Structure of Suspensions of Non-Brownian Particles with Application to Packings of Spheres

The internal structure of systems of particles in a liquid is studied with a novel NMR technique based on the measurement of the squared modulus of the magnetization in presence of a pulsed field gradient. The formalism is analogous to the one used in classical scattering techniques (light, X-rays, neutrons); it allows similar information to be obtained about the structure (in particular, the structure factorS(q)). The main improvement is that the range of particles sizes is 10 μm to 1 mm, as compared with the range of the scattering techniques (<5 μm). The NMR technique was validated by studying packings of spherical particles of mean diameter 240 μm created by sedimentation. The profile of the experimental squared modulus of the magnetization versus the wave vector provides results for the mean size of particles and the compacity. The main feature is that it depends on the pair distribution function, and the present results are in good agreement with a model based on the Percus–Yevick approximation. This technique is then particularly adapted to systems such as non-Brownian suspensions, fluidized beds, porous media, and sediments.     

Morphological effects on mechanical properties of polystyrene-polyvinylchloride blends

The morphological effects on mechanical properties of polystyrene/polyvinylchloride (PS/PVC) polymer blends were investigated through dynamic mechanical analyzer. Study reveals that the peaks of Tan δ curves of pure PVC and pure PS samples fall at temperatures 58.9 ± 0.2°C and 113.1 ± 0.1°C, respectively. Tan δ curves of 30, 50 and 70-wt% of PVC blends show two peaks indicating the immiscibility of PS/PVC blend. It has been observed that peak falling at lower temperature side shifts towards the higher temperature with the increase of PS concentration and the other one which falls at higher temperature side shifts towards lower temperature side with the increase of PVC concentration in PS/PVC blends. The variation in mechanical performance is attributed to the polymer domain interactions resulting from the different morphologies of various blend compositions.     

Jumplike deformation of polymer materials on the micrometer and submicrometer structural levels

Jumplike creep is considered as a reflection of the structural heterogeneity of amorphous polymers on the mesoscopic and nanoscopic levels. The D-450 epoxy resin, poly(vinyl chloride), poly(vinyl butyral), and a composite consisting of the D-450 epoxy resin and diabase microparticles are studied at a temperature of 290 K. The creep rate of the specimens under compression is measured with a laser interferometer in submicrometer-scale deformation increments. Periodic variations of the creep rate with time or under deformation correspond to a jumplike (stepwise) behavior of the creep. It is shown that diabase particles (5–10 μm in size) are responsible for the appearance of micrometer-scale jumps in the creep of the composite and that the deformation jumps on the nanometer level are comparable to the sizes of the globules. The role of the resolution of the method employed in the evaluation of the scale of deformation jumps and structural units is considered.     

Compatibility of PVC-chlorinated PVC mixtures

This study deals with the compatibility of a poly(vinyl chloride) mixed separately with two industrial chlorinated poly(vinyl chlorides), denoted PVC/C1 and PVC/C2 (chlorine contents of 65.2 and 67.5%, respectively). The technique of mixing, examined for different compositions, is the main parameter for the compatibility of the resins. The mixtures were prepared either with a Brabender plastograph, with a milling cylinder at 190°C (the mixture being fluid), or by sintering at a temperature between 180 and 200°C under pressure. We determined the complex components of the elasticity modulus as a function of temperature (from 50 to 170°C at a frequency of 110 Hz) for each mixture, using a Rheovibron viscoelastometer. The study of the structure of the mixtures, based on the variation of the tangent of the loss modulus, allows us to say that the compatibility of polymers depends on the chlorine contents in chlorinated PVC; thus, at 65.2% the chlorinated polymer seems to be compatible with PVC, but at 67.5% the mixture shows the characteristics of a two-phase system. The compatibility is also dependent on processing methods.     

采用紫外光照法在磷酸盐玻璃中合成CdS/Ag复合微粒

掺杂有Ⅱ-Ⅵ族半导体纳米颗粒(如CdS)或者过渡金属(如Ag)的玻璃由于其较大的非线性光学效应而引起人们的极大兴趣,而同时掺杂有半导体/金属的复合微粒则可以进一步增强玻璃的三阶非线性效应,因此成为目前的研究热点。我们利用玻璃沉淀技术及随后的热处理和紫外光还原技术制备了含高浓度(1%)Ag微粒的玻璃,并采用X射线衍射分析了其物相,用高分辨扫描电镜分析了其形貌,以及测试了其吸收和发光性能。从CdS/Ag复合微粒的扫描照片可以发现晶粒均匀分布在玻璃中,尺寸约为1μm。X射线衍射发现经过热处理和紫外光照的样品衍射峰中含有CdS和Ag,而只进行热处理的样品则只含有CdS,未处理的样品则显非晶态。CdS/Ag复合微粒的吸收峰呈现典型的表面等离子共振峰(420nm)以及CdS的峰(600nm),只含有CdS微粒的样品的吸收峰则在480nm附近,未处理的样品在320nm附近有一个吸收峰,这可能是由于样品在快速冷却过程中的微小晶化造成的。只含有CdS微粒的样品有三个明显的发光峰,然而CdS/Ag复合微粒的发过峰则消失。我们提出了共振能量转移机制来解释该现象。讨论了紫外光照还原Ag微粒的机制。可以认为通过紫外光照,CdS表面的电子被激发出来还原Ag+,从而形成银颗粒,伴随着空穴则被表面缺陷所捕获。     

氢气氛区熔硅单晶热处理缺陷形成机理

本文用X射线衍射形貌法、红外吸收光谱法和金相腐蚀坑法,探讨了氢气氛区熔硅单晶热处理缺陷的形成机理。在生长态晶体中存在着三种Si-H键,对应的红外吸收峰波长分别为4.55微米、4.75微米和5.13微米。随着加热过程的进行,Si—H键逐渐分解而消失。5.13微米吸收峰的消失温度是450℃,4.55微米吸收峰的消失温度是600℃,4.75微米吸收峰的消失温度是700℃。晶体中的热处理缺陷是由于氢沉淀造成的,沉淀过程首先是Si—H键分解,然后是氢的扩散和聚集。沉淀过程的激活能是2.4电子伏特(56000卡/克分 关键词：     

A Study on the Morphology and Mechanical Properties of PVC/nano‐SiO2 Composites

Three methods were used to modify nano‐SiO₂ particles with various interfaces and interfacial interactions between the particles and Poly(vinyl chloride) (PVC) matrix. The experimental results show that direct surface treatment of nano‐SiO₂ particles with a silane coupling agent (KH‐550) is not effective for improving the mechanical properties of PVC/SiO₂ composites. Both ultrasonic oscillations and high energy vibromilling improve the interfacial interactions between SiO₂ particles and PVC matrix. With these methods, the aggregation of SiO₂ particles was inhibited and a good dispersion of SiO₂ particles in PVC matrix was obtained, which improved the mechanical properties of the PVC/SiO₂ composite. The mechanical properties of the PVC/SiO₂ composite with high energy vibromilling modified SiO₂ particles were remarkably improved. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic mechanical analysis (DMA), and theoretical calculations demonstrate these improvements.     

高分子网络凝胶法制备ZnO超细粉体及其光学性能

采用高分子网络凝胶法制备球形ZnO超细粉体。通过聚乙烯醇(PVA)亚浓溶液交联网络的空间位阻作用,经过烧结,获得了具有球形形貌的粒径为1~3μm的ZnO粉体颗粒。利用X射线衍射(XRD)、扫描电镜(SEM)分析了不同PVA浓度以及退火温度对产物形貌、结构的影响,发现在PVA溶液浓度为5%,并且经500℃热处理所形成的ZnO球形颗粒最为均匀规整。研究了球形ZnO粉体的光致发光性能,室温下经325nm波长激发,观察到两个中心波长分别位于407,468nm的微弱的荧光发射带,在合适温度下,在385nm处还出现了较强的紫外峰。PL光谱表明,退火温度对ZnO的光致发光影响较大,随着退火温度升高,由于表面缺陷和结晶性能发生变化,407nm处发射峰逐渐减弱消失,而紫外发光先增强后减弱,经500℃热处理样品的紫外发光性能达到最佳。     

PDC材料烧结过程中钴在金刚石层中的扩散熔渗迁移机制

 讨论了PDC材料烧结过程中钴在金刚石层中的固相扩散、钴液熔渗、两次钴高浓度峰的“波浪”式迁移过程中的运动规律及其作用机制,并根据实验观测的数据进行了有关计算。结果表明：在5.8 GPa、1 300 ℃条件下,钴的扩散系数D≈1.6×10^-7 cm²/s,是一般常压及相同温度条件下钴固相扩散系数（3×10^-10 cm²/s）和相同压力条件下钴的液相扩散系数（5×10^-5 cm²/s）的中间值;对于粒度W≥10 μm的金刚石烧结体系,钴液熔渗作用时间非常短暂,略大于0.5 s,而对于W≤1 μm的超细金刚石烧结体系而言,钴熔渗作用时间为28 s,比粒度W≥10 μm的金刚石烧结要长得多;两次钴高浓度峰的迁移速度分别约为50 μm/s和100 μm/s。     

Effect of flexibility of grafted polymer on the morphology and property of nanosilica/PVC composites

In this study, poly(methyl methacrylate)-grafted-nanosilica (PMMA-g-silica) and a copolymer of styrene (St), n-butyl acrylate (BA) and acrylic acid (AA)-grafted-nanosilica (PSBA-g-silica) hybrid nanoparticles were prepared by using a heterophase polymerization technique in an aqueous system. The grafted polymers made up approximately 50 wt.% of the resulted hybrid nanoparticles which showed a spherical and well-dispersed morphology. The silica hybrid nanoparticles were subsequently used as fillers in a poly(vinyl chloride) (PVC) matrix to fabricate PVC nanocomposite. Morphology study of PVC nanocomposites revealed that both PMMA- and PSBA-grafted-silica had an adhesive interface between the silica and PVC. The tensile strength and elongation to break were found to be improved significantly in comparison with that of untreated nanosilica/PVC composites. Finally our results clearly demonstrated that the properties (e.g. chain flexibility, composition) of the grafted polymer in the hybrid nanoparticles could significantly affect the dispersion behavior of hybrid nanoparticles in PVC matrix, dynamic mechanical thermal properties and mechanical properties of the resulted PVC composites.     

用微米级LaNi5为催化剂生长的碳管的ESR谱研究

用微米级LaNi₅合金粉末为催化剂, 以乙炔为原料, 采用化学气相沉积(CVD)法合成了多壁碳纳米管. 在100~290 K温度下测量了41 μm≤d≤150 μm粒径催化剂制备的不同直径分布的碳纳米管的电子自旋共振（ESR）谱,研究了测量温度、微米级催化剂粒径及制备过程的氢气氛对生成的碳纳米管的ESR谱线型、g因子、线宽的影响. 发现碳纳米管的g因子随其直径的增大而增大,分别为2.040 0（催化剂粒径41 μm≤d≤50 μm, 碳纳米管的直径分布为10 nm到20 nm）和2.089 8（催化剂粒径100 μm≤d≤150 μm,碳纳米管的直径分布为70 nm到120 nm）. 发现小管径纳米管的ESR谱图有一个峰, 而大管径纳米管的ESR谱图有两个峰A和B, 且随测量温度的升高, 峰B强度增大.     

Thermomechanical properties of polymer nanolithography using atomic force microscopy

The temperature-dependent mechanical properties of polyethylene terephthalate (PET) polymers are investigated using force-distance curves, adhesion force, and atomic force microscope (AFM) nanolithography combined the heating techniques. The results show that the width of grooves on the polymers at 20-60 °C were in the range of 14-363 nm. The wear depth of the polymers increased with increasing heating temperature. A volume of 251.85-2422.66 μm(3) at a load of 30-50 nN with heating to 30-60 °C was removed, as compared to that of 26.60-70.30 μm(3) obtained at room temperature. The contact forces of PET started increasing at 9 nN, whereas the size of the holes was average at a pressure. The results may be of importance in explaining the heating relationship among adhesion force, volume removal rate, and pressure.     

Preparation and Evaluation of the Morphology,Flammability, and Mechanical Properties of the Acrylonitrile‐Butadiene‐Styrene/Poly (vinyl chloride) Blends

Blends of two grades of acrylonitrile‐butadiene‐styrene (ABS) with three different compounds of poly (vinyl chloride) (PVC) were prepared via melt processing and their morphology, flammability, and physical and mechanical properties were investigated. SEM results showed that the ABS/PVC blend is a compatible system. Also, it can be inferred from fracture surface images that ABS/PVC blends are tough, even at low temperatures. It was found that properties of these blends significantly depend on blend composition and PVC compound type; however, the ABS types have only a small effect on blend properties. On blending of ABS with a soft PVC compound, impact strength, and melt flow index (MFI) increased, but tensile and flexural strength decreased. In contrast, blending of ABS with a rigid PVC compound improved fire retardancy and some mechanical properties and decreased MFI and impact strength.