Recycling of plastic bottles - the second life of polyethylene terephthalate (PET)

Processing of plastic bottles is one of the directions of using recyclable materials for the resumption of the resource base of polymer materials. During recycling the problem of waste recycling is solved, and materials are obtained that can be sent back to production, even taking into account some limitations (technological, hygienic, legislative, sanitary) associated with the reuse of polymers.

Due to the fact that polyethylene terephthalate (PET) has sufficiently stable mechanical properties, the processing of plastic bottles from it is the most practiced and established way of using polymeric secondary raw materials. There are two main types of processing - mechanical and chemical. As a rule, in most cases, PET bottles are processed mechanically, since chemical demands for increased raw material requirements and the use of expensive catalysts are necessary. The mechanical method does not require waste plasticization. PET bottles are first sorted from other types of packaging made of polymer (polyethylene, PVC) and foreign objects (plugs, debris). Depending on the requirements for the final product, the bottles can be sorted by color and even by type of polymer.

The initial processing of plastic bottles occurs on a knife crusher, where as a result of technological redistribution, PET particles of 0.5-10 mm are formed. The resulting polymer crumb is washed with a solution of caustic soda or water, after which it is dried by a certain technology at a humidity of 0.02-0.05% and a temperature of 130 ° C. The drying process is of great importance, non-compliance with the required humidity parameters leads to an irreversible deterioration in the quality of secondary raw materials.

After drying, agglomeration of the material takes place, as a result of which the crumb technology obtained in the previous stages is sintered into small lumps. At this stage, the processing of plastic bottles may be completed, since the agglomerate can already be used as raw material. In order to average the physical characteristics of the recyclables, it produces its granulation. As a result, the treated PET particles become more dense, and the resulting material is easier to use in the future and to obtain the necessary materials on standard equipment. The main directions of using raw materials from PET waste are the production of films, fibers and bottles. As a rule, taking into account the mechanical and rheological (fluidity of material) properties of recyclable materials from PET, it is used for the production of containers for various chemical products. As packaging for food products, recycled PET is not used. Fiber from secondary polyethylene terephthalate is most often processed into woven bases for making carpets and clothes or textiles. Secondary raw materials are also used for the production of geotextiles, synthon, noise insulation materials, absorbing and filtering elements, electrical products, fittings (by casting), automotive parts.