临界组成区域的热敏导电材料加工工艺

研究了开炼，密炼及双螺杆挤出３种不同塑炼方式及采用压制，注射，单螺杆挤出３种不同成型方法对临界组成区域的热敏导电材料电性能及力学性能的影响规律，并对开炼，密炼两种工艺的混炼条件，加料方式及加料顺序进行了考察，结果表明，采用密炼工艺，炭黑（ＣＢ）粒子能得到均匀分布，电阻率较低，拉伸强度及断裂伸长率高，适中的剪切速率及温度有利于ＣＢ粒子分散，采用压制成型法所得样品各向同性。     

Gel phenomena in flexible PVC resin

The existence of fisheyes or gels in PVC final products has been a problem which the PVC industry has coped with for many years. The classical gel is a non-porous PVC particle which cannot absorb plasticizer. Other finished product defects which may be classified as gels by a customer are unfused particles of higher molecular weight resin or resin gels and agglomerates caused by improper mixing procedures called compound gels. Although this paper will define and cite examples of resin gels and compound gels, it will deal primarily with classical gel. Over the years, many different gel tests have been used by PVC suppliers and consumers in order to define the gel level of a particular sample of resin. The most common of these tests is the test using a two roll mill to produce a colored mill sheet which is examined and the number of gels reported. This paper will use statistical methods to the factors which can introduce variability into the test results, including mill roll gap, mill speed, milling time, and temperature. In addition, the nature of the distribution of gels in a sample of PVC resin will be discussed. Finally, the paper will delve into new laboratory techniques which may lead to eventual automation of counting and reporting of gel levels in a resin sample.     

A mathematical model of the calendered exiting thickness of micropolar sheet

A theoretical analysis based on the lubrication theory is presented to study the calendering mechanism. The material to be calendered is described by the constitutive relationship of a micropolar fluid. An exact solution and numerical solution of the problem is calculated. The roll‐separating force, power function and exiting sheet thickness are computed numerically using Runge‐Kutta method. The influence of the material parameters on the pressure distribution, pressure gradient and related quantities of engineering interest in calendering process is analyzed through graphs. POLYM. ENG. SCI., 58:327–334, 2018. © 2017 Society of Plastics Engineers     

Understanding the functions of acrylic processing aids in rigid PVC injection molding

Poly(vinyl chloride) (PVC) compound use is growing in specialty injection molding applications such as appliances, business equipment, and electrical enclosures. A key factor in determining the appearance and physical properties of the molded parts is the processability of the PVC compounds, which can be improved through the use of acrylic processing aids. Processing aids promote PVC fusion, modify the melt rheology, and/or provide lubrication. Some processing aid products are designed to serve one of these functions while others provide a combination of functions. Each of these functions and its major benefits in rigid PVC injection molding are described. Some guidelines for selecting appropriate processing aid products for applications are provided.     

基于多指标综合评分法的开炼机炼胶工艺参数多目标优化

本文采用青岛科技大学自行研制的XK-160E型开炼机智能炼胶实验平台对开炼机炼胶工艺进行正交实验,并运用基于模糊映射的质量指标加权综合评分法对混炼胶的门尼粘度、炭黑分散度、300%定伸应力,拉伸强度,撕裂强度进行综合评分。通过极差分析确定辊距、辊速、速比、辊筒温度、混炼时间五个工艺参数对综合评分值的影响大小,并分析得出最优的开炼机炼胶工艺参数组合方案。     

Instability and failure phenomena in polymer processing with application to elastomer mill behavior

The mill behavior of different elastomers is discussed in some detail and contrasted with melt fracture in extrusion. The mill characteristics of elastomers are discussed, with special emphasis on effect of roll speeds and nip and on molecular structure of elastomer. Theories of failure mechanics in polymer processing are contrasted, and a theory of a viscoelastic material that exhibits rupture above a critical recoverable energy is analyzed. Mixing with carbon black is briefly discussed.     

Influence of fillers and oil on mill processability of brominated isobutylene‐co‐paramethylstyrene and its blends with EPDM

Milling behavior of brominated isobutylene‐co‐paramethylstyrene (BIMS), and its blends with ethylene propylene diene rubber (EPDM), with special reference to the effect of addition of different fillers, filler loadings and processing oil, was investigated over a range of temperatures in a drop mill operation. The critical nip gap (CNG, at which a front to back roll transition (F‐B transition) occurs, was also measured. Addition of different fillers reduced the value of the critical nip gap and the mill band formation indices for BIMS as compared to the gum polymer, indicating a decrease in the tendency to go to the back roll. The systems containing reinforcing fillers showed a lower value of the critical nip gap, as compared to systems containing low or non‐reinforcing fillers. For different filled blends of BIMS and EPDM, the CNG decreased on increasing the EPDM content, indicating a decrease in the tendency for a F‐B transition. The CNG decreased on increasing the N330 carbon black‐loading, while it increased with the addition of procesing oil. The results were explained in terms of rubber to metal adhension and viscosity of the polymers.     

1400dtex/2锦纶6加密帘布在9.00-20 16PR载重斜交轮胎中的应用

对1400dtex/2锦纶6加密帘布和1870dtex/2锦纶6帘布在9．00—2016PR载重斜交轮胎中的应用进行了对比试验。结果表明，采用1400dtex/2锦纶6加密帘布，通过调整轮胎外缘尺寸、缓冲层和胎圈等结构及混炼、帘布压延和胎面胶挤出等工艺条件，可使轮胎性能符合要求，并可降低生产成本。     

Knurl roll design for stable rotogravure coating

When a thin film of fluid is coated on a web by any type roll or spreader coater such that the fluid splits while in a divergent channel the resulting fluid surface is not smooth but is made up of ridges, running in the direction of coating. At production speeds (50 m/min and higher) there is a natura frequency of this fluid ribbing effect which is independent of the type of coater and fluid rheology, and depends only on the depth of the wet coat of transferred liquid. A study has been made to determine how this natural ribbing frequency is related to coating stability on a rotogravure coater with ruling mill knurled coating roll. It has been observed that many knurl rolls deposit a metastable fluid pattern on the web when the resulting fluid sur matches the knurl pattern of the roll. Under some coating conditions this resulting surface becomes unstable and the fluid is transferred to a conditio fewer ridges per cm, resulting in a non-uniform coated surface. It was found that to enhance stable transfer from the knurl grooves it is necessary to the knurl roll surface to match the natural fluid ribbing frequency. The farther the knurl line frequency deviates from the natural fluid ribbing frequ the more often the coating surface will become unstable.     

Effects of formulation variables on rheology of rigid PVC

The effects of lubricants, impact modifier, and process aid on the processing and physical properties of a rigid PVC compound have been modeled using a central composite designed experiment. Capillary rheology was used to evaluate the flow properties of the various formulations in the study. By modeling the rheological properties it is possible to optimize simultaneously the flow, extruder conditions, and final part properties.     

Factice from oil ofPutranjiva roxburghii

Preparation and characterization of factice by vulcanization of oil extracted fromPutranjiva roxburghii, a fairly abundant plant of the tropical Indian subcontinent, is presented. This information serves as a processing aid for substituting commercially available factices. Mechanical and thermal studies of this new type of factice, blended with rubber, showed higher thermal stability and improved processing characteristics during extrusion and calendering operations compared to rubber without factice.     

Rheology parameters controlling spray atomization and roll misting behavior of waterborne coatings

Formation of small coating droplets is a phenomenon common to spray and roll application of coatings. Generation of small droplets, referred to as atomization, is the mechanism of controlling the quality and thickness of the applied coating layer in spray technology. In roll coating application, small coating droplets are formed at the nip–exit region under certain conditions. Because of the high-shear rates at roll nips and spray nozzles, it is common to relate high-shear viscosity with atomization and roll misting behavior of coatings. This paper will review the relative importance of shear and extensional flows, and the response of coatings to such flows, in affecting misting and atomization behavior. Experimental efforts to quantify the effect of shear and extensional rheological parameters have clearly established a lack of correlation of high-shear viscosities with both spray atomization and roll misting behavior of coatings. However, extensional viscosity is shown to have a strong correlation. Finally, how rheology modifiers can be selected to circumvent misting problems in roll coating applications and atomization problems in spray applications is discussed.     

J60—71膨胀型氯化橡胶防火涂料生产工艺的探讨

研究了用球磨机工艺代替三辊机工艺生产Ｊ６０－７１膨胀型氯化橡胶防火涂料,改善涂料性能的途径。     

New developments in melt rheology aid formulating rigid vinyl compounds with improved extrusion processing

This paper describes a new approach to the rheological characterization of PVC compounds using a capillary rheometer. Since the control of the thermal degradation rate of rigid PVC is very critical in extrusion, a new quantitative method of measuring the true degradation rate of PVC is proposed for formulating rigid vinyl compounds. The usefulness of this new technique is demonstrated in formulating PVC compounds with the lowest rate of degradation measured on the Kayeness capillary rheometer. This study shows a very good correlation between the capillary rheometer data and the extrusion melt temperature, melt viscosity, and the rate of degradation of PVC. The ideal melt temperature for extrusion is determined from the rheology data of each PVC compound to attain the longest run time. The study also shows how to measure the true melt temperature in extrusion, an important variable, to control the rate of degradation in processing. The results of this study show how the new rheology technique can be used as a practical tool for product development, quality control of the PVC compounds, and the development of optimum extrusion parameters.     

Viskositätsverhalten von PVC beim Kalandrieren

Based on the data of the roll separating forces, gauges of films, and peripheral speeds of the rolls, obtained during the calendering of PVC-compounds and rubber-compounds, the apparent viscosities and shear rates have been calculated. The graph of the apparent viscosity versus the shear rate in a logarithmic scale shows the same shape as graphs of apparent viscosity versus shear rate obtained by measurement with a capillary rheometer. Nevertheless, the graphs obtained by measurements during calendering show an absolute value shifted to a higher level than that obtained by means of a capillary rheometer.     

A model describing the two-dimensional calendering of finite width sheets

A model that describes the two-dimensional flow of power-law fluids during calendering of finite sheets is presented. Unlike the one-dimensional calendering model in which the sidewise flow is neglected, the model presented in this work takes into account both lengthwise and sidewise flow. The lubrication approximations are used to simplify the equations of motion. The model is characterized by a free moving boundary at the sheet side edge. This free moving boundary was determined by assuming a zero velocity component for the sheet in the direction normal to the sheet side edge. This condition allows one to locate the position of the sheet side edge and thus to describe the sheet shape. The partial differential equations describing the model were solved by using the finite element method. Results obtained from the model showed that the sidewise flow, and the pressure field are a function of the system dimensions such as roll radius (R), gap between rolls (H₀), sheet initial width and thickness (W₀ and H_F, respectively) and the rheology of the material. Results were expressed by a dimensionless parameter, named sheet spread and defined as the ratio between the final and initial width of the sheet (W/W₀), which is a function of different geometrical ratios such as R/H₀, W₀/H₀ and H_F/H₀ and the rheology of the material, specifically the flow index n. Results of the model were validated by measuring the width increase of a calendered polymeric material over a range of feed thickness, widths, gaps, roll speeds, on two sheeters of different radius. Fairly good results were obtained when the model results were compared with experimental data.     

热塑性聚氨酯弹性体／氯化聚乙烯共混体系的研究

选用ＣＰＥ和ＣＰＥ／ＰＶＣ为改性剂．用双辊熔融共混的方式对ＴＰＵ的共混改性进行了系统的研究，对ＴＰＵ／ＣＰＥ和ＴＰＵ／ＣＰＥ／ＰＶＣ共混体系的性能进行了测试分析及对比。结果表明：选择适宜的ＴＰＵ种类和ＣＰＥ、ＣＰＥ／ＰＶＣ分别组成二元和三元共混体系，能明显改善ＴＰＵ的加工特性，并且基本保待了ＴＰＵ优良的耐油性和耐寒性。     

An engineering study of the film embossing process

A mathematical model of the dynamics and heat transfer of the film embossing process has been developed. The thermal analysis around the preheat roll is determined from an unsteady, two-dimensional heat conduction equation along with appropriate boundary conditions by neglecting the curvature of the preheat roll and choosing a Lagrangian reference frame. The heat transfer occurring between the preheat roll and the embossing rolls is based on a one-dimensional analysis, including both convective and radiative effects. The deformation occurring in the nip region is analyzed for two different situations. For the case where the surface features are small in comparison with the film thickness, a modified one-dimennsional calendering analysis is given, accounting for the irregular geometry of the embossing roll surface. For the case where the polymer does not make complete contact with the surface of the engraved channel, the local deformation is determined by means of a simple one-dimensional cavity filling model. The required pressure distribution is determined by means of a simple one-dimensional cavity filling model, The required pressure distribution is determined by means of a conventional calendering analysis. The analysis for the case of a Newtonian and power-law model is presented in detail. The model yields qualitatively correct results and is computationally simple.     

Elongational flow mixing for manufacturing of graphite nanoplatelet/polystyrene composites

Manufacturing strategy is of prime importance for the appropriate incorporation of filler into a polymeric matrix, and this in particular refers to nanofillers. Herein, direct‐graphite nanoplatelets are used as filler in polystyrene. The as‐received filler material contained microscopic size agglomerates formed by nanoscopic size graphite nanoplatelets. Refining of the microagglomerates (break‐up) and production of, desirably, single graphene layers (exfoliation) is the ultimate target for controlling production and thus properties of the present materials. Several processing methods including microcompounding, roll‐milling/calendering, Brabender mixing chamber, and solvent processing are used and compared with elongational flow mixing by a newly developed mixer. For the present system, sonication with surfactant assistance solvent processing yields both good micro deagglomeration and production of thin graphene nanostacks/layers. Also the elongational flow mixing efficiently refines the microagglomerates. Solvent processing and microcompounding are more efficient than the other processes in the production of exfoliated thin graphene stacks/layers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rheology and enhancement of extrusion of linear and branched polyethylenes using low amount of organoclay

Interaction between 0.05 wt % organoclay and polyethylenes of different short chain branching (SCB) was studied. Linear rheology (van Gurp‐Palmen plot) was used to study the effect of organoclay on the rheology of polyethylenes. Organoclay had effect only on the van Gurp‐Palmen plot of linear polyethylene. Fourier transform (FT) rheology, extrusion at high‐shear rates in a slit rheometer, transient stress growth analysis, and extensional rheology were conducted to examine the potential of organoclay as a processing aid. Organoclay reduced the transient stress overshoot, normal stress difference, ηo, onset of shear thinning, and extrusion pressure of polyethylene. The reduction was more pronounced in linear polyethylene without branching. Such effects gradually decreased as the branch content increased. The trend was independent of the type of flow (shear or extensional). It was interesting to note that FT rheology was not effective in explaining the impact of organoclay on polyethylene. The work concluded with the proposition that organoclay (as low as 0.05 wt %) was a good processing aid for linear polyethylene and polyethylenes with low content of SCB. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012