外文翻译---矿物填充物在聚苯乙烯熔融过程的作用

1、附：英文翻译英文原文effects of mineral llers on polystyrene melt processingj. lou, v. harinathabstractthe recycling of thermoplastics containing mineral llers represents great technological challenges in the waste management in the plastics industry. several mineral-lled polystyrene samples were prepared and

2、their morphological and melt processing properties were studied with respect to the processing conditions and mineral loadings. the results should provide insights that are needed to solve complex issues encountered in the industry dealing with the recycling of this important class of materials. 200

3、4 elsevier b.v. all rights reserved.keywords: mineral llers; polymer processing; melt viscosity1. introductionthe compounding and inclusion of particulate llers in the polymers is a rather complex process. the processing of these materials is strongly dependent on the particleparticle and particlepo

4、lymer interactions. in recent years considerable research efforts have been made toward more fundamental understanding of the rheological behavior of highly lled polymeric material systems. while mineral llers are widely used in thermoplastics as ways to produce cost-effective, strong, and energy ef

5、cient materials, they are the source of many problems in waste management when these materials enter the waste stream after their intended end uses. the polymers are not readily broken down by the natural elements in the environment or in waste management infrastructures such as composting to become

6、 a part of the biological carbon cycle of our ecosystem. this results in an irreversible buildup of these materials in the environment, causing scarring of landscapes, fouling of beaches, and a serious hazard to marine life. since most of these plastics are not biodegradable,recycling and reprocessi

7、ng often represent the best option for their waste management. because these thermoplastics materials contain not only the polymer resins which are often thermoplastic and reproccessable, but also a signicant amount of mineral llers whose inuence on the processing and recycling of the composite mate

8、rials are not well understood. composites with mineral loading approaching to their maximum packing capacity are encountered in a number of industries. they include building materials such as ooring materials, sealing materials, ceramics and elastomers. the presence of mineral llers increases the me

9、lt processing difculty in terms of viscosity of the composite by orders of magnitude, alters the elastic properties significantly, and often causes the material to exhibit wall slip under common processing conditions 1.the processing difculty in terms of melt viscosity and pressure loss of the miner

10、al-lled plastics is a complex issue. the effects of llers on the processing properties of thermoplastics are far from being conveniently modeled. theoretically, at very low mineral loadings, the material behaves like a dilute particle suspension. the viscosity of a dilute suspension, , can be develo

11、ped in a power series in the volume fraction of the particles 2. the virial-type expansions are commonly used to illustrate the effect of the llers on the melt viscosity of a polymer, truncated at some nite order due to the difculty of calculation of the virial coefcients at higher orders = /0= 1 +

12、+ kh2+ (1)where s is the relative viscosity, the viscosity of the suspension, 0 the viscosity of the dispersion medium. these dimensionless virial coefcients are called the intrinsic viscosity (when volume fraction is used for ) and the huggins interaction coefcient kh, respectively. in the limit of

13、 innitesimal particle volume fraction ( 0), the term linear in dominates so that the effect of these llers on the change in is purely hydrodynamic and is proportional to . as increases, higher order terms become important. the use of the virial expansion is quite limitedfig. 1. viscosity as a functi

14、on of shear rate for polystyrene at various ller volume fractions at 190 c.in practice because there is no established ways to predict the coefcients of higher order terms. small submicron llers are often strongly interacting particles. however, their ability to interact should rather be dened by th

15、eir surface properties with respect to the matrix chemistry 3. when polymerller interaction is strong, an adsorbed polymer layer may be formed on the ller surface. in this case, at the same level of volume fraction as in non-interacting particles, the interactions will induce a much larger stress in

16、 the matrix of the composite and therefore induce a much larger reinforcing effect. this is the reason why there is a great interest in incorporating small-scale mineral particles into polymer composites such as the so-called nanocomposite. although the causes of the maximum volume concentration rem

17、ain to be debatable, this characteristic can be obtained experimentally if the processing properties exhibit discontinuous transition over the volume concentration. various concentration regimes for the properties of polymermineral systems have been dened according to the volume fraction, such as di

18、lute, semi-dilute,concentrated and highly concentrated 4.in dilute suspensions, ller particles are apart from one another at sufcient distances. the llerller interactions can be neglected. in this case, only hydrodynamic forces give rise to the properties. in the case of small particles and low visc

19、osity matrix, these forces arise mainly fromfig. 2. represents ow of polystyrene at 190 and 200 c, respectively with cx300-33 die.fig. 3. bagley plot for the end pressure effects for various dies with different l/d ratios at the same shear rate (587, 1328, and 3000 s1).random brownian motion. proper

20、ties of composite materials depend on the volume concentration, shapes, and the particle-modied stress eld between adjacent particles.2. experimentalthe amorphous polystyrene styron 615 sample was donated by dow chemical (midland, usa). the sample was weighed and transferred into the beaker to which

21、 the solvent tetrahydrofuran (thf) was added and the solution was stirred continuously until the polymer was completely dissolved. a known amount of mineral particles of calcium carbonate whose nominal particle size is 1 m was then added to the polystyrene and the solution was completely mixed until

22、 uniform mix was achieved. finally the solution was transferred to a clean and dry plate glass and made into thin sheets. the composite sheets were kept in the convection oven at 100 c fig. 4. end pressure losses at a shear rate of 587, 1328, and 3000 s1.fig. 5. determination of onset of percolation

23、 of mineral-lled polystyrene.overnight. the sample was then taken out and cut into small pieces and stored. in similar fashion samples with different volume fractions were prepared for 1030 and up to 70%.the mineral-lled samples were subjected to capillary melt extrusion experiment at a temperature

24、190 c with a melt time of 300 s to allow air and moisture trapped in the sample barrel to evolve. the experiment was carried out using dynisco instruments model 7001 lcr capillary rheometer (morgantown, pa, usa). the diameter of the dies used was 1mm and the length to diameter ratios ranged from 1 t

25、o 32. the entering angle of the dies was 180. these experiments were used to determine the processing and recycling behavior of these polymermineral composite materials.3. results and discussionthe mineral llers make the recycling of the composites more difcult by increasing the energy consumption i

26、n the melt processing process. the energy consumption is related to the total pressure drop in the melt ow p, including the end pressure losses pend (sum of the entry pressure drop and the exit pressure drop) and the pressure drop within the extrusion die pdie 5fig. 6. electron microscopic view of s

27、urface sharkskin at shear rate of 1800 s1 and 190 c: (a) 0% minerals, (b) 20% (volume) minerals.fig. 7. the electron microscopic cross-section view of the extrudates: (a) 0% mineral, (b) 20% mineral.p = pend + pdie (2)the relationship, which governs the wall shear stress and the total pressure drop

28、in the die extrusion, can be expressed asw = (p pend)d/4l (3)where w is the shear stress at the wall, d the diameter, l the length of the die, pend the end pressure losses which are determined using the bagley plot method.the shear rate was calculated from the speed of the extrusion plunger: = 4r2bs

29、p/r3c (4)where rb is the radius of the feed barrel, rc the radius of the die, sp the speed of the plunger. the apparent shear viscosity a is dened asa = w/ a (5)fig. 1 shows that the viscosity of the mineral-lled polystyrene increases with the volume fraction of the mineral llers. as expected, the s

30、hear viscosity decreases with an increase in temperature, provided they are chemically stable. this is shown in fig. 2. at prolonged and elevated temperatures, some polymers may increase in molecular weight through gel-forming or cross-linking, resulting in a rise in viscosity. alternatively, it can

31、 break down by way of chain scission causing a larger than expected drop in viscosity with temperature.fig. 3 is the typical bagley plot that is used to calculate the end pressure losses. the end pressure losses are characteristic of the viscoelastic nature of the polymer melt owing through the chan

32、ging cross-sections. the end pressure losses thus obtained show a signicant dependence on the processing condition in terms of shear rate, as shown in fig. 4. the increase in the end pressure losses is more rapid than linearly with the shear rate.percolation modeling of dispersion viscosity at high

33、concentrations was also studied. the typical results are shown in fig. 5. at low concentrations, the viscosity increases linearly with volume fraction as the volume fraction is not high enough to effect llerller interactions. but the slope increases rapidly at higher volume fractions to demonstrate

34、the strong interactions between llers and the slope changes at around 27% volume fraction relatively insensitive to the shear rate. this point at which the slope changes is the onset of the percolation where the llers are interconnected or networked within the polymer matrix.the capillary ow of molt

35、en polymers has received much attention because at high ow rates the melt processing of the polymer are commonly accompanied by instabilities, which is called as sharkskin or melt fracture 68. this is one of the problems in polymer processing that is not completely understood. it is found from our s

36、tudy that the minerals decrease the surface roughness on the processed material. the elastic behavior such as die swell is also reduced with the increase in mineral loading. fig. 6 shows that the shark-skin was less pronounced as the mineral volume fraction increases. fig. 7 shows the cross-section

37、view of the mineral llers in the polystyrene samples. it is evident the llers are well dispersed inside the polymer.4. conclusionthe recycling issues of mineral-lled plastics and composites are complex. as the loading of the mineral particles increases, the processing viscosity, pressure losses, and

38、 thus the processing difculty and energy consumption increase.the minerals however reduce the sharkskin and die swell problems in the processing. the melt processing is sensitive to the llerller interactions and processing viscosity can be used to detect the onset of percolation of the llers inside

39、the polymer. this paper demonstrated that percolation phenomena can be determined using rheological measurements.references1 a.j. walberer, an investigation of the rheology of reactive and nonreactive highly lled polymer systems, ph.d. thesis, university of illinois at urbana-champaign, urbana, il,

40、2000.2 m. gahleitner, melt rheology of polyolens, prog. polym. sci. 26(2001) 895.3 g. havet, experimental investigation and modeling of the rheology of silicapolystyrene mixture, ph.d. thesis, university of southern california, los angeles, ca, 2000.4 q. li, synthesis of polymer particles by emulsie

41、r free emulsion polymerization and rheological behavior of model lled polymers, ph.d.thesis, university of southern california, los angeles, california,1996.5 j.z. liang, material characterization: studies on melt ow properties of low density and linear low density polyethylene blends in capillary e

42、xtrusion, polym. testing 16 (1996) 173.6 y. hong, film blowing of linear-low density polyethylene blended with a novel hyperbranched polymer processing aid, polymer 41 (2000)7705.7 j.d. shore, sharkskin texturing instabilities in the ow of polymer melts, physica a 239 (1997) 350.8 c. venet, stress d

43、istribution around capillary die exit an interpretation of the onset of sharkskin defect, j. non-newtonian fluid mech. 93(2000) 117.中文译文矿物填充物在聚苯乙烯熔融过程的作用摘要：含有矿物填料的热塑性塑料的回收代表了在塑料工业废物管理方面伟大的技术挑战。几种矿物填充聚苯乙烯样品制备及其形态和熔融加工性能进行了研究方面的条件和矿产加工负荷。结果应提供在工业中与本类重要材料的回收处理类似的所需解决复杂问题的见解。关键词：矿物填料；聚合物加工；熔体粘度1、简介聚合物的复

44、合及在其中夹杂颗粒填料是一个相当复杂的过程。这些材料的处理主要依赖于颗粒和颗粒和颗粒与聚合物间的相互作用。近年来大量的研究已对高聚合填充物材料的流变行为有了基本的了解。当矿物填料广泛用于热塑性塑料的方法来生产高效益、坚固、节能的材料时，废物管理的许多问题的根源，是这些材料进入废物流后的最终用途。该聚合物不容易被环境中或废物管理系统中成为生态系统循环一部分堆肥的自然元素所破坏。这导致了这些物质在环境中的不可逆的变化，造成了自然的破坏、海滩的污染，并严重威胁到海洋生物。由于这些塑料大多不能被生物降解、回收和再处理，这使它们成为废物管理的最佳选择。这些热塑性材料不仅包括聚合物热塑性树脂，还包括对矿物

45、填料的加工和复合材料的回收的了解。与矿物最大容量负荷接近的复合材料被用于许多的行业。它们包括建筑材料，如地板材料，密封材料，陶瓷和弹性体。矿物填料的存在增加了复合材料熔解粘度，显著改变了其弹性性能，并且往往造成物质表现出在共同加工条件下的滑移。在矿物填充塑料的熔体粘度和压力减小的条件下其加工是很复杂的。填充物对热塑性材料加工的影响远不只这些。理论上，在非常低的矿产负荷时，物质粒子的行为像悬浮液。稀悬浮粘度，可在粒子的体积分数的幂级数发展。在维里型扩张中通常用来说明聚合物的熔体粘度，以便填料效应会因维里系数计算困难而中断s = /0= 1 + + kh2+ 其中s是相对粘度，是悬浮液粘度，0是分

46、散介质的粘度。这些维里系数的量度分别被称为固有粘度（当体积分数为时使用）和相互作用系数kh.当颗粒体积分数无穷小（0），长期线性主导而使这些填料的改变而与 成正比。由于的增加，高阶计算变得很重要。在实践中维里膨胀的作用十分有限，因为没有既定的方法来预测高阶项的系数。亚微米级填料通常是相互作用力强的粒子。然而，它们之间的作用力应通过其表面化学性质来定义。当聚合物与填料的相互作用强时，聚合物的吸附层可能会在填料表面形成。在这种情况下，当同一体积分数作用与不同粒子时，会使复合材料间相互作用压力增大，作用增强。这就是为什么对高分子复合材料如纳米复合材料中加入小规模的矿物颗粒有极大兴趣。虽然最大体积浓度的产生原因仍然是有争议的，这一特性还是可以通过试验中体积浓度的不连续过渡看出。对不同浓度聚合物矿物性能可按照体积分数来分类，如稀释、半稀释、集中、高度集中。图1：粘度是聚苯乙烯在190时在不同填料下体积分数的剪切速率图2：聚苯乙烯在190和200190时的熔体粘度