Research On The Properties Of Polyethylene Wax Produced By Thermal Cracking In Single-screw Extruder Reactor

As an important raw material,polyethylene wax has a very wide range of applications in the chemical industry,and its market demand has also increased in recent years.In this paper,extrusion pyrolysis method was used to prepare polyethylene wax,and the effects of process conditions,raw material characteristics,catalyst on the viscosity average molecular weight,melting point and molecular weight distribution of polyethylene wax were investigated.In addition,the properties of the polyethylene wax are adjusted and optimized by raw material blending cracking,product compounding,product separation and purification.The main research work of this paper is as follows:(1)The single-factor variable method was used to investigate the variation of the viscosity-average molecular weight and melting point of the polyethylene wax with the screw speed and pyrolysis temperature on the single-screw extrusion pyrolysis platform.The adjustment of the viscosity-average molecular weight and melting point of the polyethylene wax is achieved within a limited range.An industrial extrusion cracking device was designed and developed on the basis of experiments,and the feasibility of the performance control method of polyethylene wax was verified.The effects of nitrogen protection and cooling forming methods on the properties of polyethylene wax products were compared and analyzed.(2)The performance difference of HDPE,LLDPE and LDPE cracked polyethylene wax was compared and analyzed under the same process conditions.The effect of the properties of the raw materials on the pyrolysis process and the properties of the polyethylene wax was investigated.The preparation of different grades of polyethylene wax was achieved by changing the process conditions.In addition,the variation of the properties of polyethylene wax with the ratio of raw materials was investigated by the compounding of oligomers and polyethylene wax products and the cracking of different polyethylene blends.Multi-layer controllable adjustment of polyethylene wax performance was achieved.(3)The polyethylene wax is prepared by extrusion cracking using a combination of catalytic cracking and thermal cracking.The difference in performance between catalytic cracking and thermal cracking products was investigated.The HDPE and LDPE catalytic cracking products were compared to analyze the influence of the raw material characteristics on the catalytic cracking reaction.The non-polar solvent heating extraction method is used to separate and purify the over-catalyzed cracked polyethylene wax to optimize the molecular weight distribution of the polyethylene wax product.