Dissertation > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polycondensation resin and plastic > Polyester resins and plastic materials > Unsaturated polyester

Study on the Engineering Plasticization of Recycled PET in Beverage Bottles

Author ZhangShaoFeng
Tutor LiYingChun
School University of North
Course Materials Science
Keywords R-PET LDPE-g-MAH ABS SMA compatibility mechanical properties rheological property
CLC TQ323.41
Type Master's thesis
Year 2012
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Polyethylene terephthalate (PET) are used mainly for fiber production. In non-fiberfield, PET is applied to manufacture the thin film and packaging container of beverage, food,especially the production of beverage bottles has been developed on a large scale very muchin recent years. As the increasing production of beverage bottles, which are mostly made upof PET, recycling of wasted PET has become a problem pressing for solution. By studyingthe new recycling technology and preparing the modified recycled PET(R-PET) engineeringplastic with high performance and low cost, this research contributes not only to the resourcescomprehensive utilization, but also to achieving a new economic growth point by thetechnology itself. The main research contents and results are as follows:1.R-PET was blended with LDPE、LDPE-g-MAH, as well as nucleation catalyst SiO2and chain extender epoxy resin. Influence of the content of LDPE、LDPE-g-MAH on theblend’s mechanical, rheological and crystallization properties were studied respectively.Results are as follows:(1)When the addition of LDPE、LDPE-g-MAH was 30% and 15%, the blend’s optimummechanical properties was achieved: impact strength reached 4.06KJ/m2, which was fourtimes than that of R-PET, 0.86 KJ/m2. Tensile strength was 32.50MPa. Flexural strength was38.21MPa, and flexural modulus was 1624.00MPa.(2)It was indicated by SEM analysis that when the content of LDPE-g-MAH was low,the two phases spreaded unevenly in R-PET/LDPE, which meant poor compatibility andshowed layered structure. As the increasing addition of LDPE-g-MAH, blend’s toughnesswas enhanced remarkably because of the reaction between LDPE-g-MAH and the terminalgroup of R-PET, by whose product the interfacial force was increased. When the content ofLDPE-g-MAH was 15%, LDPE-g-MAH, as the dispersed phase, dispersed uniformly in the R-PET matrix. Meanwhile, the best blend’s mechanical properties were achieved.(3)DMA analysis showed that with the addition of LDPE-g-MAH , blend’s storagemodulus (E′) and glass transition temperature (Tg) were improved greater than those of PET;Moreover, the internal friction (tanδ) of blend was also changed.(4)DSC results showed that the crystallization ability of R-PET was improved by thecompatibilizer LDPE-g-MAH and LDPE, the condensate depression was lowered and thecrystallization degree was increased. The crystallizing behavior of R-PET was improved.(5)The Non-Newtonian index of R-PET/LDPE/LDPE-g-MAH blends were all less than1, which meant that the blends were pseudoplastic fluid and exhibited shear-thinningphenomenon. Under the same shearing stress, the flow activation energy of the blends firstincreased and then decreased with the increasing content of LDPE-g-MAH. When theaddition of LDPE-g-MAH was 15%, the flow activation energy was the biggest. Under thesame shearing rate, the apparent viscosity increased with the addition of LDPE, while thecontent of LDPE was over 30%, the apparent viscosity fell off significantly. The value ofblends’flow activation energy were not high, which meant that the blends were not sensitiveto the temperature.2.R-PET/ABS/SMA blends were prepared with styrene grafted with styrene-maleicanhydride copolymer (SMA) as compatilizer. Besides the impact strength, tensile strengthand compatibility, the relationship between the mechanical properties and microstructure wasstudied with the combination of SEM photographs of R-PET/ABS’s dispersedness andfracture surface. Results were as follows:(1)Compared with the pure R-PET, blend’s mechanical properties were improved to agreat extent. When the content of ABS was 40%, and SMA addition was 5%, the impactstrength reached a maximum value, 3.13 KJ/m2, 3.63 times higher than that of pure R-PET.Tensile strength was 51.53MPa. Flexural strength was 70.32MPa, and flexural modulus was2600.73MPa.(2)R-PET/ABS blends were continuous two-phase structure. ABS dispersed moreuniformly with the addition of SMA, and dispersed size decreased. The interface adhesive force between the two phases of R-PET/ABS blends was improved and two-phase structurewas thinned. When the content of SMA was 5%, the optimum compatibility was achieved.(3)DMAtests showed that the glass transition temperature (Tg) of R-PET andABS gotclose to each other with the addition of SMA, which meant that the compatibility wasimproved; When the content of SMA was 5%, blend’s storage modulus reached a maximumvalue and the interaction of R-PET, ABS and SMA arrived in a perfect condition.(4)It was indicated by the DSC analysis that the R-PET’s temperature of cold crystalpeak descended with the application of SMA. Crystallization degree of R-PET decreased withthe increasing content of SMA.(5)R-PET/ABS/SMA blends were all pseudoplastic fluid and exhibited shear-thinningphenomenon. As the shearing stress increased, the shearing rate increased. TheNon-Newtonian indexes of R-PET/ABS/SMA blends were all less than 1. Apparent viscositywas more sensitive to the shearing rate. Under the same shearing rate, apparent viscosityincreased with the increasing content of SMA, while the addition of SMA was over 5%,apparent viscosity dropped in a large scale. As the addition of SMA increased, blends’flowactivation energy first increased and then decreased. The blends were not sensitive to thetemperature.

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