Study Of RPET Chain Extending And Blending With PP And PC Respectively

China is a big power of PET bottle consumption,with lots of waste PET bottles appearing every year.On account of most of waste PET bottles are recycled from roadside in domestic,and the recycling facility of most recycling factories in domestic are behind foreign developed countries,which resulted in the low quality of recycled PET bottles.Combined with the degradation of PET bottles during secondary extrusion processing;In addition,recycled PET bottles exist a lot of problems,such as poor flow stability,slow crystallization rate and poor product impact.All these limit the reprocessing development of recycled PET bottles.Based on this background,in this study,recycled PET bottle flakes(rPET)were studied by using rPET as the main material,co-rotating twin screw extruder as the main instrument,then it carried on the detailed analysis about the rPET chain extension,rPET/PP blend,rPET/PC blend.The main research contents and research results are as follows:rPET chain extension: The chain extension of PET were conducted with adding chain extender,such as methylene diphenyl diisocyanate(MDI),pyromellitic dianhydride(PMDA)and MDI/PMDA,and its intrinsic viscosity was studied,its crystallization behavior was discussed by using differential scanning calorimetry(DSC).The results show that the intrinsic viscosity of rPET could reach a maximum value of0.87dL/g using PMDA as chain extender,And the intrinsic viscosity of 0.68dL/g for MDI chain extender.However,using various composite chain extenders with the weight ratio of PMDA to MDI,the intrinsic viscosity of rPET changed between 0.62-0.68dL/g.It is found that the crystallization temperature of rPET decrease as the addition of PMDA or MDI,While the crystalline enthalpy of rPET rise in differential scanning calorimetry(DSC).The crystallization rates remain constant in these improved rPET,including PMDA,MDI and PMDA/MDI composite chain extenders.rPET/PP blend: At first,the influence of antioxidant 1010 and chain extender PMDA on the mechanical properties of rPET/PP blend was investigated,after determining the best addition amount,then joined with compatilizer PP-g-MAH adding to the different proportion of rPET/PP blend.Finally,the mechanical properties of the blend system were tested,furtherfrom the morphological structure of impact-fractured surfaces of blending system and DSC curves,the relationship between its compatibility and performance was analysed.The results show that antioxidant 1010 could improve the mechanical properties of rPET/PP blend,and adding amount of 0.2 is the best.PMDA could improve the tensile strength and flexural strength,and adding amount of 0.1 is the best;But the impact strength decreases with the development of PMDA.As the rPET/PP blend of different ratio that antioxidant 1010,PMDA and PP-g-MAH worked together,with the addition of PP-g-MAH,the mechanical properties of the blend system were improved to varying degrees.Observing the SEM morphological structure of impact-fractured surfaces of blending system,when without adding compatilizer,two phase presented obvious phase separation characteristics,presenting obvious island structure;on the contrary,the addition of PP-g-MAH endowed better compatibility to the rPET/PP blend system.Analysisi by DSC indicated that melting temperature of rPET/PP blend mofired by antioxidant 1010,PMDA and PP-g-MAH decreased,while the crystallization temperature increased,campared unmodified rPET/PP blend,mainly due to the addition of antioxidant 1010 improved the compatibility of the rPET/PP blend,and promoted the dispersed phase dispersed.rPET/PC blend: Select PP-g-MAH as the compatilizer of rPET/PC blend,forming ternary blending system rPET/PC/PP-g-MAH.First testing the mechanical properties of rPET/PC/PP-g-MAH blend with adding different amount of PMDA,then the appropriate adding quantity of PMDA was confirmed.In the way of changing the PP-g-MAH addition amount and the ratio of rPET/PC blend,we made a series blending system,and the mechanical properties and DSC of blend systems were tested,the morphological structure of impact-fractured surfaces of blending system was observed.The results show that compatilizer PP-g-MAH could improve the mechanical properties of ternary blending system.As rPET/PC=30/70 or 70/30,PP-g-MAH of 20 parts could rearch the optimal mechanical properties of blend system,while rPET/PC=50/50,30 parts or more PP-g-MAH was needed to show excellent mechanical properties of blending system.Observing the SEM morphological structure of impact-fractured surfaces of blending system,the surfaces in rPET/PC blend are more balance than rPET/PP blend,but the interface still could be observed.After joining PMDA and PP-g-MA,the surfaces of rPET/PP system turned mroe balance,and it's hard to observe the interface.This suggests that PMDA and PP-g-MA could improve the compatibility of the rPET/PC blend.Analysisi by DSC indicated that the crystallization performance of rPET declined after joining PMDA and PP-g-MA.Thisis primarily the anhydride groups in chain extender PMDA works with rPET/PC in the coupled crosslinking reaction,which resulted in hampering the crystallization of rPET.Tg of rPET improved,which indicated that PMDA and PP-g-MA could improve the compatibility of the rPET/PC blend from the aspects of molecular chain movement.