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R-PET flakes used in this study were provided byLong-cheng Company, China. Considering the difficultiesarising from the high temperatures involved and thelimited hydrolysis and thermal stability and the impurityconcentration of R-PET melt under process conditions,particular care was taken to ensure reproducibility of theexperimental data and minimization of errors. Thus, theas-received R-PET flakes were predried at 1208C in aDHG Series Heating and Drying Oven for 12 h to keepthe moisture content under 0.1 wt%. The intrinsic viscosityof R-PET flakes was determined to be of 0.59 dL/g,measured in a 1/1(wt) mixture of phenol and tetrachloroethaneat 258C. The epoxide modifier (Trade No.ADR4370S) used in this study was purchased from BASFand was predried in a vacuum oven at 508C for 12 h.ProcessingMelt modification of R-PET was carried out in an intensivebatch mixer with RM-200B torque rheology (RM-200B, China). In a typical experiment, the as-received RPETflakes were predried overnight to ensure moisturecontent less than 0.1 wt%. Approximately 60 g dried RPETflakes and a predetermined stoichiometric amount ofepoxide modifier were added in the intensive mixer witha preset chamber temperature. Reactive mixing continuedfor 7 min to ensure the reaction completed. As shown inFig. 1, a multifunctional epoxide chain extender(ADR4370S) was employed to rebuild the molecularstructure of post-PET by bridging their functionally terminatedchains. The temperature and torque were monitoredduring the process. The effects of the concentration ofADR4370S on the overall rate of modification wereinvestigated by setting the chamber temperature at 2658Cand by varying the amount of additive from 0.5% to 2.0%with a constant mixing rate of 40 rpm. The insoluble contentof the modified materials (including unprocessed andprocessed R-PET flakes in the absence of ADR4370S)
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