Synthesis And Properties Of Fluorinated Acrylate Grafted Polypropylene

In this thesis,fluorinated acrylate was grafted onto polypropylene(PP)with porous structure by suspension grafting in aqueous phase.The graft polymerization and the properties of the grafted products were studied.The dielectric properties of PP/polyvinylidene fluoride(PVDF)blends were investigated.The main research work is as follows:(1)2,2,3,4,4,4-hexafluorobutyl methacrylate(HFBMA)was used as graft monomer and benzoyl peroxide as initiator.The effects of the amount of monomer and initiator on graft yield(GP)and graft efficiency(GE)were studied.With the increase of monomer content,GP increased gradually,and the maximum grafting rate reached 21.5%,while GE decreased from 76.0%to 47.5%.With the increase of grafting rate,the melt index of PP-g-PHFBMA decreased gradually;with the increase of initiator content,GP and GE decreased.Scanning Electron Microscope and Energy Dispersive Spectrometer analysis showed that the grafting reaction occurred uniformly on the surface and inside of PP porous particles.The PHFBMA phase dispersed in PP matrix after melt processing,and the particle size of the dispersed phase ranged from 0.79 to 1.65 um.With the increase of GP,the water contact angle increases from 94° to 104° of pure PP,and the dielectric constant increases gradually.When GP is 21.5%,the dielectric constant increases by 6%,and the dielectric loss is basically unchanged in the low frequency region.The notched impact strength of PP-g-PHFBMA is twice as that of pure PP when the GP is 6.3%.(2)The crystallization behavior of PP-g-PHFBMA was studied by differential scanning calorimetry and X-ray wide angle diffraction.It was found that the crystallinity of PP-g-PHFBMA first increased and then decreased with the increase of grafting rate.However,the crystallinity of PP-g-PHFBMA was higher than that of pure pp.under the same cooling rate,the crystallization temperature increased with the increase of grafting rate.The non-isothermal crystallization kinetics of PP-g-PHFBMA was further studied.It was found that the crystallization rate of PP-g-PHFBMA was higher than that of pure PP by Jeziorny and Mo models fitting,and the crystallization activation energy of PP-g-PHFBMA was lower than that of pure PP by Kissinger formula.There was no significant difference between PP-g-PHFBMA and pure PP by polarizing microscope observation,which was mainly a spherulite.The results showed that PHFBMA grafted chains had heterogeneous nucleation effect on PP,the number of nucleation sites and spherulites increased,and the spherulites size decreased.(3)PP-g-PHFBMA with different blending ratio was melt blended with PVDF to prepare high dielectric composites.With the increase of the percentage of PVDF,the dielectric constant gradually increased and the dielectric loss also increased.The results show that the dielectric properties of PP-g-PHFBMA/PVDF=80/20 blend are better,the dielectric constant of PP-g-PHFBMA/PVDF=80/20 blend is 27.8%higher than that of pure PP,and the increase of dielectric loss is small in low frequency region.