Experimental Investigations on the Induced Anisotropy of Mechanical Properties in Polycarbonate Films

The prime aim of this paper is to investigate, with the help of experiments, the induced anisotropy of mechanical properties in polycarbonate films. It is known that a molecular orientation in polymer materials occurs through cold-forming. In this study, cold forming is performed at room temperature on a tensile testing machine. The polycarbonate films are examined in two phases. In the first phase, the specimen is loaded, while the prestrain is varied, and in the second, it is loaded, while the material direction is varied. The main findings are that the prestrain has virtually no influence on the anisotropy and that the material direction does exert a major influence. Furthermore, this paper summarizes comparisons of anisotropic characteristic data, maximum stresses, elasticity moduli and failure strain. 1. Introduction It is known that the mechanical properties of amorphous polymers are changed by an orientation of the molecular chains. This directional dependence of a material's properties is known as the anisotropy [1]. The effect of orientation concerning the impact strength and the brittle-ductile transition in polycarbonate structure has been studied in [2]. The structure and anisotropy of isotropic and uniaxial drawn samples of polycarbonate studied by WAXS [3] and the elastic and optical properties [4] are also well known. Anisotropy in the hot-formed polycarbonate was investigated already in 1962 by Hofmeier, who studied the tensile strength of amorphous polycarbonate films, produced from bisphenol A-based polycarbonate, and established that the tensile strength can indeed be increased through deformation [5]. During hot forming, the chains are aligned parallel to the direction of the applied force, as a result of which anisotropies are produced in terms of tensile strength, elasticity moduli, and failure strain. In [6], Schultze-Gebhardt examined oriented polycarbonate filaments of bisphenol A polycarbonate. Here, too, a deformation-induced anisotropy was produced through heterogeneous deformation. In the present work, the aim is to analyze the initial anisotropy with regard to the mechanical properties and the deformation-induced anisotropy through cold-forming. The polycarbonate plastic used in the anisotropy tests within this paper is amorphous with an irregular arrangement of the molecular chains (Figure 1(b)). When amorphous thermoplastics cool down, the disorder of the molecular chains remains. In contrast, when the chains of semicrystalline thermoplastics cool down, they arrange themselves in a regular pattern, resulting in