Tham khảo tài liệu 'recycling of plastic materials part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 26 PET Co-injection Molding Furthermore the PET flakes are exposed to a melting temperature in the injection barrel which would degrade most organic substances in the middle layer. In a new multilayer PET bottle this middle layer is shielded by layers made of virgin PET. The contents of the bottle food are therefore separated by a layer of virgin PET from the middle layer. In the case of inorganic toxic substances which might have migrated into the PET surfaces in the ppb-range and furthermore survived the processing temperatures these extremely small fractions will be diluted with the melt cake in the injection barrel and hot runner system. CONCLUSIONS Pressure from environmentalists and legislations require creative solutions for re-using of packages. Discarded plastic packages can be reprocessed into articles similar to the originals. Co-injection technology allowing for the injection of a layer of melt of reground PET flakes into the center of the preform wall offers a technology of using low cost post-consumer regrind PET bottle resin. The layer of the melt of reground PET flakes is completely insulated in the middle of the bottle and therefore has no contact with the filled-in product such as food nor with an outside environment. Contamination of filled-in products is therefore excluded. Cost savings by this method are about 20 . . La Mantia and D. Curto 27 Recycling of Post-consumer Greenhouse Polyethylene Films Blends with Polyamide 6 F. P. La Mantia and D. Curto Dipartimento di Ingegneria Chimica dei Processi e dei Materiali Universitá di Palermo Viale delle Scienze 90128 Palermo Italy INTRODUCTION Problems connected with recycling of polymeric materials arise mainly from the heterogeneous nature of plastics waste and from degradation of polymers occuring either during their processing or their lifetime. As for the first point important only when mixtures of plastics have to be recycled it is well established that a strong incompatibility is typical for
