ABSTRACT
As a result of the increase in the consumption of plastics, the wastes generated from their production, transportation, and consumption create various environmental problems. The problem of waste plastic management can be solved if economic, political, technological, energetic, material, and environmental dimensions are all considered. Since plastics are generally high calorific value products ranging approximately from 18,000 to 38,000 kcal/kg, utilization for their energy alone or for related chemical production may be an alternative option.1,2 Some polymers such as polystyrene and poly(methyl methacrylate) undergo to produce monomers and other monoaromatics besides other hydrocarbon.3,4 However, polyethylene and polypropylene having 0% and 2% monomer yield should not be used for monomer production processes. These kinds of polymers undergo pyrolysis process to produce valuable hydrocarbons.5 Recycling processes for waste plastics are classified into two categories: mechanical and feedstock recycling. The former covers a range of physical methods aimed at converting the polymeric residue into plastic pellets or directly into secondary plastic materials.6,7
Nowadays, considerable research interest is focused on new polymeric materials obtained by blending two or more polymers.8-10 Mixing of different polymers have revealed a new realm of technically important
materials. Their properties can be altered by varying the composition of the polymer blends. Although a large number of combinations of polymers are possible, there are relatively few that lead to a totally miscible system. A blend of two components is classified11 as miscible, thermodynamically, if the Gibbs free energy of mixing is less than zero and the second derivative of the Gibbs free energy of mixing is zero or positive. The major feature of such process is that the intermediate properties are in some cases better than those exhibited by either of the single components.12-14 In addition, some modifications in terms of processing characteristics, durability, and cost can be achieved via polymer blending.15 In recent years, the blends of acrylonitrile-butadiene rubber (NBR) and poly(vinyl chloride) (PVC) have been widely used in industry.16 Major applications of these blends include conveyor belt covers, cable jackets, hose cover linings, gaskets, footwear, and cellular products.17 It is worth noting that NBR acts as a permanent plasticizer for PVC in applications such as wire and cable insulation in which PVC improves the chemical resistance, thermal ageing, and abrasion resistance of NBR.18,19 PVC is miscible with NBR (23-45% acrylonitrile content) at all composition ranges.20 The aim in blending plastic and rubber is to improve the physical, thermal, and mechanical properties as well as to modify the processing characteristics and cost reduction of the final product. Some blends, however, are incompatible. In a blend of rubber-plastic, such as NBR-PVC, the rubber must be vulcanized in the final form.16 One way to improve the final performance of this blend is by means of interfacial modifier or compatibilizing agents acting from the matrix side.21 In general, these interfacial modifications have generated great interest in materials based on polymers as polymer blend or poly blends, because these agents are able to enhance the interaction level between the material components, such interactions take place through the interphase.16,22 Recycling plastic wastes through blending, by solution casting of NBR and PVC where the extend of replacing virgin PVC by waste PVC is used. Studies were conducted on PVC/NBR blends. Three different compositions are chosen for the present study, that is, 20%, 50%, and 80% both waste PVC and pure PVC with NBR. Solution blending was used as the technique for the preparation of blends of various compositions. Cyclohexanone is used as the solvent to prepare the blends.
