The thermal conductivity of a solid or gas filled polymer is iised i n processing or end use application calculations. Numero u s theoretical and empirical correlations are fomntl in the literature. A careful re\,iew ofthese niotlels indictes that no one correlatioii or technique accuratel? predicts the thermal contluctivit! of all t?-pes of composites. The investigation indicated that for solid filled composites the Lewis and Nielseii eqiiation fittctl the experimental data best for the range offillers tested. However, for a gas filled pol? nier, iioiie ofthe theoretical models proved atleqiiate. The semi-empirical approach of Hartli in g show e (1 co in s i derab le merit ,

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The fi rst edition of this modest work was designed as an introduction and supplement to my larger effort, "Technology of Thermoforming", also published by Hanser. It presented a general overview of this rapidly growing fi eld, without extensive details or equations.Although the basic elements of thermoforming have not changed in the near-decade since the publication of the fi rst edition, the industry is maturing and more details of the inner workings of the process are needed. Thermoforming is not just about machinery, molds, plastics, and making parts. It is also about process monitoring and control, quality assurance, safety and competitiveness with other processes. I've made an effort to broaden the work to include many of these aspects.Two disparate areas for product development have become important recently. Thermoforming has been used in transportation for many years, primarily to produce low-volume parts. Truck and aircraft interiors and bus and train toilet interiors are examples. The development of paint fi lm technology has spurred an interest in thermoformed paint-free exterior panels for domestic vehicles. Another developing area is bio-devices. Biotechnology is arguably the most rapidly growing science worldwide. Of course, there are many thermoforming applications already. A recent development, where 25-micron thick fi lm is thermoformed into 350-micron hemispheres as containers for cell cultures, emphasizes microthermoforming.The intent of the work has not changed. It remains a primer. I've rearranged the chapters to focus on the mechanics of the process fi rst, then to consider the nature of the polymers. I've also added a short chapter on comparing thermoforming -technically and economically -with other technologies such as blow molding, rotational molding, and injection molding.One caveat, though. In the fi rst edition, there were no equations. In this edition, there are equations, but only simple ones, for illustration only.

Rotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This paper is devoted to the theoretical understanding of the process of rotational molding. There are seven sections:Ths Art, wherein we describe the process, discuss previous attempts at understanding the process, and mention processes that are similar in principle to rotational molding.Transient Heating of Mold Surface, wherein we show that the criterion for selection of mold materials is the ratio of the thermal d8usivity to the thermal conductivity, and present the heating curve for a mold in a rotational mold machine.Melting of Plastic Powder in a Rotating System, wherein we discuss in detail those physical powder characteristics that are necessary for good flow within the mold cavity.Flwid Flow During Rotational Molding, wherein we discuss the velocity profiles within the melt film, point out that there is very little bulk polymer flow possible within the mold cavity under normal processing conditions, and consider capillary flow forces and surface wetting.Sinter-Melting, wherein we compare the Kuczynski-Neuville empirical sintering model with the Lontz viscoelastic model, conclude that the latter is correct for the sintering of materials such as ABS, and apply the Frenkel glass densification theory to the prediction of void disappearance in sinter-melt polymers.Degradation, wherein we compare our experimental tensile strengths of polystyrene, obtained at varying oven cycle times and oven set point temperatures, with values obtained from degradation models given in the literature.Laboratory Simulation of Rotational Molding, wherein we propose two series of experiments, the first series being carried out without using rotational molding equipment, and the second using rotational molding equipment with molds having relatively simple geometries. THE ARTAs far as we can tell, the first materials that were R o t a t i o n a l molding or rotational casting is the process by which hollow plastic parts are formed.This process, in principle, is as follows. Very fine plastic powder is loaded into a split hollow metal mold. The mold is then rotated about the equatorial and polar axes while the powder is heated above its melting point. Once the melted plastic covers the inside of the mold surface, the assembly is cooled to room temperature and the part removed. The process is then repeated. * Present address: University Est. de Campinas, Caixa Postal 655, Campinas; S. P., Brazil. O 0 Present address: Energetics Department, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201.cast in this manner were vinyl plastisols, which were introduced into the molds as liquids and heat-cured. An example of an early application is the vinyl beach ball. This process was well known in the late 1940's 243

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