Processing effects on poly(ethylene terephthalate) from bottle scraps

Abstract

Processing of virgin and recycled polytethylene terephthalate) (PET) in a twin screw extruder evidences the degradative effect caused by thermal decomposition of polytvinyl chloride) (PVC) and other impurities, e.g. adhesives, at the processing temperature. Lower melt viscosity and molecular weight, along with higher carboxylic end group concentration, were observed for recycled PET, the extent depending on PET purity. In an attempt to investigate the correlation between the kinetics of degradation phenomena and the level of thermomechanical stress, a novel dynamic method of evaluating thermal stability in processing conditions was developed. Such a method allows the achievement of long equivalent residence times while using lab-scale extruders. As a result of these experiments, PVC-rich recycled PET was shown to reach very low melt viscosity after less than 10 min in processing conditions, while virgin PET retained high viscosity even after 30 min. 5 10 15 20 25 90 Residence time (min) Rg. 4. Effmt of CLE on intrinsic viscosity. 50(1oO, 5 . . . . 0 5 10 i s Po 25 90 35 Residence time (min) Rg. 5. E f f ' t o f CIE on weight-average molecular weight

Characterization of poly(ethylene terephtalate) after multiple processing cycles

“…250°C), and is also used in reinforced plastics 1–4. Recently, recycling of plastic wastes, particularly postconsumed PET, has received considerable attention from the media, and the chemical and mechanical recycling of PET has been extensively studied 5–8. It is known that PET undergoes hydrolysis when heated in the presence of moisture above its glass transition temperature ( T g ) and near the melting temperature ( T m ) resulting in formation of oligomers with unsatured olefinic and carboxylic end groups 9, 10.…”

Consecutive steps of PET recycling by injection: evaluation of the procedure and of the mechanical properties

“…Other papers discuss the execution of consecutive recycling steps and the subsequent evaluation of their effects on the structure and properties of the materials, as reported by La Mantia and Vinci 13 and by Giannotta et al, 14 using PET from postconsumer soft-drink bottles. This type of study usually involves extruders as processing machines, and normally keep constant washing, drying, and processing parameters.…”

Poly (ethylene terephthalate) recycling for high value added textiles

“…Contamination of postconsumer PET is the major factor that contributes to the deterioration of its physical and chemical properties during reprocessing (Giannotta et al 1994). In general, contamination cannot be admitted for fiber or bottle applications because of fiber breakage and aesthetic problems.…”