Low Temperature Plasma-Induced Graft Copolymerization Of Polypropylene/Macromonomer And Their Alloy

In this thesis,the grafting copolymerization of polypropylene and EPDM rubber in the melt state was induced by a CO₂ plasma with a plasma treatment.And then the crystallization behavior,phase structure,and mechanical properties of the iPP/EPDM blends and alloys were investigated.The peroxide radical on the surface of treated polypropylene（PiPP）detected by the DPPH method showed that the concentration of the peroxide radical was up to9.79×10^-8 mol/cm².FTIR-ATR and XPS measurement were used to analyze the surface activity.The results showed that an amount of-OH,C=O and COOH groups were introduced into the treated polypropylene,which could initiate grafting reaction existed on PiPP.The characterization of surface morphology of PiPP by scanning electron microscopy（SEM）revealed that different etching conditions occurred under different processing conditions,and with the increase of the discharge time,the etching degree would increase.The crystallization rate of iPP/EPDM blends and alloys was calculated by differential scanning calorimetry（DSC）and calculated by Avrami equation.The results showed that the crystallization rate of the alloy is less than that of the blend,and the time required for complete crystallization is greater than the blend system.The equilibrium melting points（T_m⁰）of the two systems were calculated by the Hoffman-Weeks equation.It was found that the change of the blend was very small after the addition of EPDM.On the contrary,with the addition of EPDM rubber,the alloy system was increased,which indicated the structural changes of iPP.The morphology of the i PP/EPDM blends and alloys was characterized by cross-section scanning electron microscopy（SEM）.The results showed that the two phases in the alloy were more uniformly dispersed than the blend system.Small-angle X-ray scattering（SAXS）was used to obtain related characteristic parameters to study the change of phase morphology.The change of relevant parameters indicates that after CO₂ plasma treatment,the alloy is more uniformly dispersed and the phase spacing becomes smaller.The results of mechanical testings of the material showed that after CO₂ plasma treatment,the impact strength of the material can be increased to a large extent without lowering the Young’s modulus and yield strength of the material.Especially when the rubber component is up to 10%,the impact strength can be increased to 25%.