The Synthesis Of Narrow Distribution Polyethylene Wax

Polyethylene wax also known as low molecular weight polyethylene. It is an important chemical raw materials. There is a certain impact on the EPS due to its broad molecular weight distribution. However, polyethylene wax of narrow molecular weight distribution is a good nucleating agent which can uniform EPS foam. In this paper, linear and star polyethylene wax of narrow molecular weight distribution is prepared by combining anionic polymerization (LAP) and polymer hydrogenation techniques succesfully.The liquid polybutadiene of different linear low molecular weight is designed and synthesized by anionic polymerization. The solvent is cyclohexane and the initiator is n-butylithium of high concentration. The polymerization kinetic behavior is investigated at different polymerization temperatures and different initiator concentrations fully. The results show that propagation rate of butadiene polymerization is first order with monomer concentration and the rate constant of pseudo-first apparent propagation is obtained under different conditions and the activation energy of apparent propagation (Ea) is112kJ/mol and the frequency factor (A) is3.67×1019L· mol-1· min-1.With the increasing of initiator concentrations or polymerization temperatures, the values of kp will enhance gradually. We also attain the reaction order of initiator concentration is0.4and the kinetic reaction rate constant is0.024at40℃polymerization temperature.Above polymerization conditions, Linear and star-shaped liquid polybutadiene of different molecular weight are designed and synthetized at50℃. Coupling agent is silicon tetrachloride (SiCl4). It is a high1,4structure contents of (LPB SPB). Main catalyst is naphthenic acid nickel and cocatalyst is triisobutylaluminum. The linear and star-shaped liquid polybutadiene are hydrogenated respectively. We get successfully two white solid after removal catalyst. It is so characterized by infrared (FT-IR),’H-NMR, XRD, DSC and intrinsic viscosity [η] that the results show that:hydrogenation degree of low molecular weight liquid polybutadiene can reach to100%at Ni dosage of2mg/g, Al/Ni=6, hydrogen pressure of4Mpa, reaction temperature of60℃and reaction time of3hours. Melting point of linear and star-shaped polyethylene wax is from100-C to110℃, crystallinity and melting point slightly lower with the increase of molecular weight of polyethylene wax. It is so thermal decomposition temperature is at500℃that properity of heat resistance is wel.