1、PDF外文：http:/ 2563 字 附：英文翻译 英文原文 Effects of mineral llers on polystyrene melt processing J. Lou, V. Harinath Abstract The recycling of thermoplastics containing mineral llers represents great technological challenges in the waste management in the plastics industry. Several mineral-
2、lled polystyrene samples were prepared and 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 recyclin
3、g of this important class of materials. 2004 Elsevier B.V. All rights reserved. Keywords: Mineral llers； Polymer processing； Melt viscosity 1. Introduction The compounding and inclusion of particulate llers in the polymers is a rather complex process. The processing of these materials is strongly de
4、pendent on the particleparticle and particlepolymer 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
5、 produce cost-effective, strong, and energy efcient 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 managemen
6、t infrastructures such as composting to become 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
7、are not biodegradable,recycling and reprocessing 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
8、processing and recycling of the composite materials 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.
9、The presence of mineral llers increases the melt 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 o
10、f melt viscosity and pressure loss of the mineral-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 vi
11、scosity of a dilute suspension, , can be developed 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 th
12、e virial coefcients at higher order s = /0= 1 + + kH2+ (1) where s is the relative viscosity, the viscosity of the suspension, 0 the viscosity of the dispersion
13、 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 innitesimal particle volume fraction ( 0), the term linear in dominates so that the effect of these llers on t
14、he change in is purely hydrodynamic and is proportional to . As increases, higher order terms become important. The use of the virial expansion is quite limited Fig. 1. Viscosity as a function of shear rate for polystyrene at various ller volume fractions at 190 C. in practice because there is
15、 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 their surface properties with respect to the matrix chemistry 3. When polymerller interaction is strong,
16、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 the matrix of the composite and therefore induce a much larger reinforcing effect. This is the reason
17、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 remain to be debatable, this characteristic can be obtained experimentally if the processing properties ex
18、hibit 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 dilute, 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 viscosity matrix, these forces arise mainly from
