Study On Recycled Poly (Ethylene Terephthalate) Chips Blend With Polycarbonate Modified Engineering Plastics

With the wide use of PET bottles, the comprehensive using problems of recycled PETbottles (hereafter referred to as R-PET) must need to be solved. However, R-PET easilyoccurs hydrolysis and thermal degradation under high temperature and ultraviolet, whichresult in the rupture of molecular chain. Thereby, the problems of low viscosity, bad flowstability, slow crystallization rate, demoulding difficulty, and poor toughness limit the secondrecycling of R-PET. Polycarbonate as a high dosage engineering plastic possess theadvantages of good resistance to impact, high strength, strongly heat-resistance, good flowstability Good dimensional stability and so on. Another advantage is that both the R-PET andPC own the same terminal hydroxyl and carboxyl group. The similar structure helped us havemore targeted choices to chose the compatilizer and more likely to achieve reactivecompatibilizing. so as to achieve to improve the stability of the melt flow, enhance the impacttoughness of R-PET.In a word, the ultimate purpose of the study is to make a R-PET/PCblends that can substitute the expensive engineering plastic PBT(polybutylece terephthalate)or PC to produce auto parts and other industrial parts and achieve the aim of high-valuerecycling processing of recycled bottles. In this paper, the main research contents and resultsare as follows:1.We studied the effect of two plastic additives which both contained epoxy grouprespectively named chain extender epoxy resin (EP) and an elastomer PTW(ethylene-butylacrylate-glycidylmethacrylate) on recycled poly(ethylene terephthalate)(R-PET) from bottle flakes/polycarbonate(PC) blends when they added independently andmeanwhile. The results of the study are as follows:(1)When adding PTW alone into the R-PET/PC blends, with the increase of PTWcontent, the impact strength of the blend greatly increased.When PTW content reached at10%, comprehensive mechanics performance of the R-PET/PC/PTW blend was the best, the impactstrength is11.74kJ/m2, the tensile strength was47MPa.When adding EP alone into theR-PET/PC blends, The impact strength of blend material first increases then decreases, theimpact strength maximum around5.5kJ/m2which was less than that of R-PET/PC/PTW. Butthe tensile strength and bending strength is10MPa larger than the blends of adding PTWalone. When PTW combinated with EP adding into the R-PET/PC blend, both of the impactstrength and tensile strength of blend were bigger than they used alone, especially in thecontent of PTW was10%, and EP content was0.9%, the impact strength of blend materialswas13.47kJ/m2.As a result, we could conclude that PTW and EP acted synergistic effect inthe R-PET/PC/EP/PTW blends,and the EP played role of chain extender,and the PTW have ancompatibilization and toughening effect on the blends.(2)Through the SEM morphological structure of impact-fractured surfaces analysis weconcluded that:When adding EP into the R-PET/PC blends, two phase presented obviousphase separation characteristics, which explained the blend compatibility was poor. On thecontrary, the addition of PTW into the R-PET/PC blends endowed better compatibility to theR-PET/PC/PTW materials. When PTW content was10%, impact-fractured surfaces of phaseinterface was fuzzy and rough, the dispersed phase particle size become smaller and uniformdistribution. These proved that PTW have an compatibilization and toughening effect on theblends.When adding PTW and EP all together to the blend, the thickness of transition layer ofthe impact-fractured surfaces become larger with the increase of EP,and the phase boundarybecome much fuzzier,especially when PTW contents was10%and EP contents was0.9%. Itindicated that the combined action of PTW and EP had a good compatibilizing effect onR-PET/PC blends.(3)Through Infrared spectrum analysis、 the viscosity testing and the torque rheometeranalysis we found that: both of the PTW, EP in the process of molten blending had reactivewith the terminal hydroxyls and carboxyl group of R-PET and PC,which brought about theimprovement of the molecular weight and the R-PET viscosity. When the PTW workedtogether with EP，with the increasing of EP content and the PTW content fixed at10%, Whenthe EP content reached at0.9%, the intrinsic viscosity had increased to0.8456L/g, this valuehad been fully meet the requirements of engineering plastics applications required viscosity. (4)By DSC analysis shows that after adding EP or PTW, the compatibility of blendingmaterials increased significantly, especially in the combination of EP and PTW, the glasstransition temperature of the blending materials draw close to one another which suggestedthat the compatibility of blending materials was the best under the action of PTW workingtogether with EP.2.From the ester exchange reaction of PET and PC may occur in the process of meltblending of into consideration, we studied the effect of the ester exchange reaction on theproperty of the blend by means of adding a new kind of transesterification catalyst namedMonobutyltin Oxide(MBTO) into the R-PET/PC blends; Meanwhile,we researched the effectof the combination of elastomer PTW and transesterification catalyst on the property of theblend, and carried on the comparative analysis of the result of the experiment，draws thefollowing conclusion:(1) When the addition of transesterification catalysts MBTO content was0.06%, themechanical properties of materials achieve the best.On the whole, the R-PET/PC/MBTOblends taked on the characteristics of the hard and brittle, so could not reach the purpose ofpractical application. When PTW and MBTO working together, they would have acompetition effect on the blend. Ester exchange catalysis of MBTO plays main role while thePTW only played not the compatibilizer but the elastomer role in the R-PET/PC/MBTO/PTWblends when PTW content was less. However with the PTW content increasing, the reactionof epoxy group in the PTW with R-PET and PC occupied the dominant position, at themoment the MBTO only played a rigid particles or powder filler role in the blend. As a result,the molecules of free volume become larger, interfacial bond become smaller. This reasonleaded to the impact strength and tensile strength of R-PET/PC/MBTO/PTW blend was notbetter than those of R-PET/PC/PTW blend.(2)Through the SEM morphological structure of impact-fractured surfaces analysis weconcluded that: the impact-fractured surfaces of R-PET/PC only modified by MBTO wassmooth and less concave-convex,which surface presented the properties of brittle materials.With the PTW content increasing when transesterification catalysts MBTO combined withelastomer PTW, the impact-fractured surfaces of R-PET/PC/MBTO/PTW blend changed fromthe obvious difference between two photographs of layered structure gradually into twoamalgamation of stereo shape cloud structure. The impact-fractured surfaces presented the character of strong toughness materials.However, comparing the impact-fractured surfaces ofR-PET/PC/PTW blends with R-PET/PC/MBTO/PTW, the surface of R-PET/PC/MBTO/PTWblend existed many wispy holes which represented the diffuse of catalyst in the blend.As aresult, the impact strength of R-PET/PC/MBTO/PTW blend was less than the strength ofR-PET/PC/PTW blend.(3)Through Infrared spectrum analysis、torque rheological analysis, melt index test andviscosity test analysis we found that: MBTO indeed played a ester exchange catalytic effectbetween the R-PET and PC,which proved generation of the estergroup connected the benzenering.When the PTW and MBTO worked together,MBTO and PTW inhibit the effect of eachother;when PTW content less than5%, its viscosity and torque balance all smaller thanR-PET/PC/MBTO0.06%;when PTW content greater than5%, along with the increasing PTWcontent, viscosityand balance torque of the blend increasing and the maximum viscosityreached at0.6235dL/g while the PTW content reaches10%.But this maximum viscosity valuewas less than viscosity of R-PET/PC/PTW10%(0.6328dL/g).(5) By DSC differential scanning calorimetric analysis showed that: PET glass transitiontemperature of PET and PC in the secondary heating curves got close to each other, whichindicated that both of PTW and MBTO improved the compatibility of the blend.However, thethinning of crystal and the decline of crystallization ability of the crystals in the blends.