The function of lubricants in processing of rigid poly(vinyl chloride)

In this review of lubricants and how they function the lubrication mechanism is broken down into three stages: the heat absorption (onset of gelation), gelation (fusion process), and melt flow (postfusion) stages. The terms “internal” and “external” are used to describe the functionality of the lubricant at each stage. It is pointed out that these terms should not be used to label lubricants themselves, because most lubricants perform differently at each stage of processing. How the chemical and physical properties of various types of lubricants perform in each of the fusion stages is also discussed.     

On the efficiency of internal lubricants for polymers under different sliding conditions

When polymers are used as bearing materials or are processed over tooling under dry sliding conditions, the formation of a transfer layer at the interface controls friction and wear properties. The film formation may be enhanced by the addition of internal lubricants. This article reviews some effects of internal lubricants, such as graphite, polytetrafluoroethylene, and internal silicone oil, on the friction and wear of bulk polymers such as polyimide, polyester, and polyamide. Known lubricating mechanisms are complemented by an interpretation of tribophysical reactions in the sliding interface. Test results are obtained during small and large‐scale laboratory testing under high‐load and high‐temperature conditions and are further related to the effect of contact conditions. The study reveals that some lubricants are not effective under the entire range of sliding temperatures and/or normal loads. For internally lubricated polymers, the efficiency of internal lubricants strongly depends on the contact geometry. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Evaluation of poly(1,4-cyclohexylene dimethylene terephthalate) blends for improved processability

Poly(l,4-cyclohexylene dimethylene terephthalate) (PCT) exhibits superior heat deflection temperature when compared to conventional polyesters such as poly(butylene terephthalate) or poly(ethylene terephthalate). It is subject to degradation, however, at the processing temperatures normally employed to extrude or mold this material. Several approaches were taken to broaden the processing window of this material including: blending PCT with other crystalline and amorphous polymers to allow for lower processing temperatures, addition of conventional stabilizers, addition of crosslinking agents to maintain viscosity during processing and the addition of lubricants to improve processing. Key parameters included physical properties, rate of degradation, extruder torque measurements vs. time, and Differential Scanning Calorimetry (DSC) analysis (melting point and glass transition). All systems tested produced significant reduction of the intrinsic viscosity (molecular weight) for PCT during processing. The most successful approach was the blending of various polymers with PCT to lower extruder processing temperatures. Reductions in processing temperature may have resulted from improved heat transfer due to the presence of a lower melting polymer, reduction in melting point of the blend, or changes in the frictional characteristics of the PCT in the extruder. Transesterification may have played a role in compatibilizing some polyester mixtures. As expected, certain polymers had major'effects on the flow behavior of the blend. Tradeoffs were obtained in physical and thermal properties. A combined approach of polymer blending and the use of lubricants, stabilizers or crosslinking agent may hold the most promise for future development work. Thermal resistance under vapor phase soldering conditions was best for LCP/PCT blends and worst for PBT/PCT blends. Additional evaluations of the blend materials will include solvent resistance, processability, thermal resistance, dimensional stability, heat aging resistance, flammability, and specific end use tests.     

Study on temperature‐resistant properties of polymer–matrix solid film lubricants

The temperature‐resistant properties of some polymer–matrix solid film lubricants were studied. Different chemically modified methods were used in this study to enhance, their temperature‐resistant properties. The friction and wear mechanism of polymer–matrix solid film lubricants rubbing at different temperatures in air were explored with differential scanning calorimetry (DSC), scanning electron microscope (SEM), and X‐ray photoelectron spectroscopy (XPS). The test results showed that the blending modification of polymer and the application of certain of filler were beneficial to enhance heat resistance of polymer–matrix solid film lubricants, and therefore, improved their lubricating properties at different temperatures in air. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2180–2184, 2004     

Review of non-destructive testing methods for defect detection of ceramics

Ceramic material is a commonly used material with high mechanical properties such as high hardness, high wear resistance, corrosion resistance and high temperature resistance. It has been processed into various complex structures and applied to the field of industrial and agricultural production.. Since the process of ceramic products is susceptible to factors such as mixing and sintering, it is easy to cause internal or external defects of ceramic products, and the defects of ceramic products are relatively small and difficult to be recognized by human eyes. If the defects existing in ceramic products cannot be detected in time and effectively, they may have a serious impact on the application of subsequent products. In order to solve this problem, this paper analyzed and discussed the application status and existing problems of existing non-destructive testing methods from the perspective of non-destructive testing of ceramic products, and discussed the key technologies and development trends of non-destructive testing of ceramic products.     

Green lubricants production from Nile tilapia waste and prediction of physical properties through molecular dynamics simulations

Fish farming is a worldwide growing activity and a large amount of residues is produced in this process. The present work describes a cleaner and sustainable way to produce new lubricants from fish waste oil. Oil extracted from the Nile tilapia (Oreochromis niloticus) viscera was utilized as raw material to produce basic oil for lubricants. The products were synthesized by esterification with polyols, trimethylolpropane (TMP) and pentaerythritol (PE), using p-toluenesulfonic acid (p-TSA) as catalyst. The synthesized esters were characterized by infrared (IR) and nuclear magnetic resonance (NMR). Computational methods were used to predict the physical characteristics of the material. In addition, the main physicochemical properties were evaluated, as well as the thermal behavior and toxicity of the products against Artemia salina. The synthesized esters showed high viscosity indexes (VI > 150) and viscosities that fit the degree of application ISO-46 and 150. Molecular dynamics simulations indicated that at room temperature the lubricants Tilapia fatty acid - trimethylolpropane ester (T-TMPE) and Tilapia fatty acid - pentaerythritol ester (T-PEE) are in liquid and gel states, respectively, confirming the experimental data. The products did not present toxicity against A. salina. In this research, we reinforce the potential of using tilapia oil from waste to produce green lubricants as a strategy to reduce damage to the environment, as well as the use of computational methods that collaborate to predict physical properties of lubricants.     

几种润滑剂性能比较及其对ABS熔融加工的影响

对ABS常用的四种润滑剂进行了研究,对其红外光谱、转矩流变性能、熔点和耐热性能进行了对比分析。结果表明:EBS和YY-502A的极性较强,对ABS具有良好的内润滑性能,可用于ABS改性塑料和色母粒的分散和润滑;YY-502A具有双熔点特点,比单一熔点EBS具有更好的颜料分散和预处理功能,克服了低熔点润滑剂在加工初期出现润滑过度的问题;YY-502A的耐热性能优于EBS和YY-5502,是一种稳定性好、综合性能优异的ABS加工改性润滑剂。     

高流动高耐热聚丙烯改性树脂的研究

通过添加α成核剂、过氧化二异丙苯(DCP)改善聚丙烯树脂的高耐热性能和高流动性能,并研究了高流动、高耐热聚丙烯改性树脂的流动性能、耐热性能、拉伸性能和结晶形态。结果表明,随着DCP加入量的增大,聚丙烯树脂的MFR值增加,流动性得到提高;随着α成核剂用量的增加聚丙烯树脂的热变形温度随之提高,当用量为0.3%,聚丙烯树脂的热变形温度由130℃提高到145℃。     

不同润滑剂对PP/POE性能的影响

研究了不同润滑剂对PP／POE（聚丙烯／聚烯烃弹性体）性能的影响。结果表明，硬脂酸类润滑剂对PP／POE的拉伸强度影响不大，硬酯酸盐类润滑剂对PP／POE冲击强度影响不大。硬脂酸类以及非硬脂酸类润滑剂对PP／POE的弯曲模量、热变形温度均有一定的影响。润滑剂一定程度上提高了PP／POE的加工性能，润滑剂在静态以及动态的加工条件下起到的作用是不同的。硬脂酸盐类有利于PP／POE的结晶。     

航空用接插件材料的研究

甲基苯基乙烯基硅橡胶与聚四氟乙烯、玻璃纤维共混所制得的橡塑合金材料,具有优良的耐热性、耐低温性、耐潮湿性和绝缘性,并具有优良的成型加工性能,能成型各种形状复杂的制件,可用于制造在高低温条件下使用的半硬质绝缘制件及Ｈ级、Ｃ级电器绝缘制品,制得的航空用接插件经受了高低温冲击实验,性能符合要求。     

热处理温度对PBO纤维性能的影响

PBO纤维因其具有高强度、高模量、高耐热性以及高化学稳定性等性能而被公认为目前综合性能最好的有机纤维。对自制的初生PBO纤维分别在500℃、550℃、600℃、650℃和700℃进行高温热处理,并对处理后纤维的力学性能、耐热性能、表面形貌以及界面性能进行测试。结果表明,500℃下热处理后PBO纤维拉伸强度最大为4.72GPa,随着热处理温度升高,纤维的力学性能下降;600℃下热处理后PBO纤维的初始分解温度最高为641.3℃;随着热处理温度的提高,PBO纤维的表面粗糙度在增加,同时其界面剪切强度(IFSS)也随着温度的升高而增大。     

碳化硅内直肋管强化传热及分析

对国内新开发研制的ＳｉＣ内直肋管的传热及流阻性能进行了实验测试，拟合出传热Ｎｕ数和摩擦系数ｆ的关联式；并针对高温热能回收，以分析方法对ＳｉＣ内直肋管及其相对于ＳｉＣ空管的强化传热性能和能耗比进行了综合评价分析，为ＳｉＣ内肋管应用设计提供了参考依据。     

多孔陶瓷的制备及应用研究现状

多孔陶瓷在化学稳定性、抗高温氧化及耐热冲击等方面具有优异的性能,在生物材料、催化剂载体、过滤器、热交换器等众多领域的应用越来越广泛。近年来,新型多孔陶瓷的开发和应用已成为无机非金属材料研究的一个热点课题。本文综述了多孔陶瓷的类型、性质、制备工艺以及最新研究进展和应用。     

硬PVC/炭黑复合材料的性能与加工和形态的关系

本文研究了导电炉黑、润滑剂配比、抗冲击性剂以及混炼条件等对硬PVC的加工性、表面电阻和机械性能的影响。结果表明，除了炭黑用量，润滑剂配比、混炼炬温度也是决定复合材料性能的重要因素。为使复合材料具有良好的综合性能，应使制品中PVC呈初级粒子态存在。     

高性能PC／ABS合金的制备及性能研究

为改善PC／ABS合金的耐低温、耐热及成型加工等性能,通过PC、AS及高胶粉的复合,考察了AS含量对合金各项性能的影响,并制备了具有耐低温、高热变形温度、高流动性、综合性能优异的PC／ABS合金。     

Optimization of the vulcanization process of rubber products

Selection of the optimum conditions for the vulcanization of rubber products, particularly of bulky ones, often is quite difficult. Especially in cases of high demand, it is unavoidable to destruct expensive prototypes in order to check important properties of the rubber at various locations throughout the product. Finite element calculations can be used to predict the flow of heat during the vulcanization process. By converting the total heat input at a selected location during a certain time into a so-called “effective vulcanization time” at a fixed reference temperature, it becomes possible to predict the properties of the rubber at that location. An example of such a procedure is given. However, to secure optimum conditions in this way would require repetitive (expensive) calculations. In this article a method is developed in which the vulcanization conditions are derived from the required properties of the rubber compound. The idea behind it is that optimal vulcanization is reached when at each location within the rubber product the effective vulcanization time at a selected reference temperature lies within predefined limits. The choice of the limits can be derived from the dependence of each of the properties chosen on the vulcanization time at the reference temperature.     

基于分布参数的管内传热和热力学

针对流体热物性参数随温度变化大或存在相变传热的管内流动问题,提出了分布参数研究方法,特点在于边界条件、物性参数、传热和阻力计算准则式等参数都实现了局部化,能够得到管内流动更加真实准确的传热和热力学特性,并以焓方程代替温度方程,统一了相变与非相变情况下的计算。以充分发展的空气圆管层流流动为例,与解析解的结果进行了对比,验证了分布参数模型的正确性。着重分析了热物性随温度变化较大的丙三醇以及湿空气中有相变发生时的管内流动的传热特性和熵产特性。本文模型不仅对研究管内流动的基本科学问题很有意义,也是研究换热器分布参数模型的基础。     

An examination of DSC as a method of characterization of PVC lubricants

Differential Scanning Calorimetry (DSC) has been used to characterize various lubricant additives for PVC in order to determine effectiveness. Depending on the processing period, and therefore the temperature profile, each lubricant undergoes a change in the internal vs. external nature of its behavior. In the process described, monitoring of the glass-transition temperature produces evidence for the effectiveness of additives as internal lubricants.     

Analytical modelling of hysteresis heating in rolling contact of rubber covered rollers

Abstract

In a previous paper, an approximate model for the contact between a rubber covered roller and a rigid roller was developed as analytical functional relationships connecting geometric parameters and material properties of the rubber to nip properties such as maximum contact pressure, etc. in a two-dimensional relationship. The results from that development are used in this work, with the objective to provide a means of estimating the temperature rise due to hysteresis heating. In the heat conduction modelling, one-dimensional steady state heat conduction is assumed. The heat source is a power input coming from internal friction developed during the rolling contact. The power input is expressed by the hysteresis in the rubber represented by a loss angle of the material together with the peripheral speed and some parameters taken from the previously developed contact model. The temperature distribution is calculated in accordance with temperature and heat flow boundary conditions.     

螺旋流内热虹吸沸腾装置(Ⅰ)——两相流动及传热机理和性能的研究

利用透明膜加热管对内热虹吸式沸腾装置各种螺旋通道内的两相流流型的变化规律、稳定性及传热性能进行观察研究.同时用钢管绕以电阻丝加热,以便能更准确地测量传热系数.实验所用的内热虹吸管模型共有七种不同的几何尺寸,其中五种为螺旋通道,两种为直流环形通道.实验介质为水、乙醇及聚丙烯酰胺水溶液.实验结果用q～G_t和q～(?)的关系来表示.文章讨论了通道的几何形状和尺寸、介质物性等对流体流动及传热性能的影响.