Experimental Study On Grading Utilization Standard And Recycling Technology Of Recycled PET

In recent years,China has become the largest consumption country and production country of plastics in the world.Plastic is a kind of widely used material as important as steel and wood now.Since waste plastic is one of the important raw materials,the recycling of waste plastic is not only conductive to energy-saving and emission reduction but also promote the construction and development of circular economy industry.Polyethylene terephthalate(PET)is widely used in industries of packaging,Electronic appliances,medical and health,construction,automobile and other fields due to its excellent physical and mechanical properties,good creep resistance,fatigue resistance,abrasion resistance and dimensional stability.There is a large amount of production and consumption of PET in China.According to statistics,the production of recycled PET(r-PET)is about 7.9 million tons in 2016,and r-PET has been an important part of recycled plastics.Waste PET bottles account for up to 65%of total recycled PET and there are many problems in the recycling process of the large amount of recovery.First,currently r-PET recycling is often degraded due to a lack of r-PET grading standard.Second,it is necessary to seek more application ways for r-PET due to the excess capacity of recycled polyester fiber industry,especially engineering applications.Third,pollutions from the recycling process of r-PET must be controlled as it is more serious.According to the above problems,we took the r-PET bottle flakes as the research object,analyzed their basic performance index,and discussed the r-PET grading utilization standard in this paper.We also studied the feasibility of preparing composite material,the mixture of r-PET matrix with waste resin powder filler.Last we analyzed the pollution problems prevalent in the r-PET recycling process and put forward the countermeasures of pollution control.In this paper,we measured and evaluated the indicators of r-PET chosen according to the different application,combined with the existing grading standard of recycled polyester bottle flakes in textile industry and put forward r-PET grading utilization index system including the standard indicators and their magnitude for non-engineering application and engineering application.In the non-engineering application standards,we considered the impacts of density,intrinsic viscosity,ash crystallization temperature and melting point on the processes of PET spinning,blowing film and other processes,and made the appropriate range quantified.For the engineering utilization of r-PET,we chose the impact strength,tensile strength,flexural strength and flexural modulus as indicators,and quantified the toughness,rigidity and strength of r-PET to guide the practical industrial application.In order to widen the application range of r-PET,in this paper we discussed the feasibility of the preparation of composite materials of r-PET with waste resin powder,and found that when the waste resin powder is filled in r-PET matrix,the impact strength and elongation at break of composite material are reduced while bending strength and tensile strength increase slightly.The interface compatibility of the dispersed phase and the matrix is poor,and the changes of the composite properties are more obvious as the proportion of waste resin powder is lager.The silane coupling agent A-x can improve the compatibility of r-PET and waste resin powder,but its positive effect on impact strength and elongation at break is limited.Functionalized POE improves the impact strength and elongation at break of r-PET/waste resin powder/A-x composite and the improving effect is stronger with greater addition proportion,with the maximum increase of impact strength and elongation at break being 37.8%and 161.58%respectively.To prevent and control the pollution from r-PET recycling industry,on one hand,we should take the source control,process control and the end treatment into account,employ the prevention and treatment techniques for waste water,exhaust gas and solid waste produced all over the recycling process of r-PET.On the other hand,we have to implement relevant environmental policies to strengthen the standardization development of PET recycling industry.