Pre-radiation Grafting of AHB onto Polypropylene Powder and Its UV Stability
Grafting UV-absorbing functional groups onto the main chains of polymers to permanently fix them selves in the polymer products and prevent the migration,volatilization,and extraction losses,is one of the research hotspots of macromolecular UV-absorbers.In this paper,4-acroxy-2-hydroxybenzophenone(AHB)was grafted onto polypropylene(PP)powder using the pre-irradiation grafting method.The AHB mass percent effects on the grafting rate were studied.Electron spin resonance(ESR)was used to study the free radical decay of irradiated PP powder.The results show that the suitable storage time of pre-irradiated PP powder is less than 96 h.Fourier transform infrared spectroscopy(FTIR),thermal gravimetric analyzer(TGA),differential scanning calorimeter(DSC),and scanning electron microscope(SEM)were used to characterize the PP powder before and after grafting.The FTIR test results show that AHB is successfully grafted onto PP chains.The TGA test results indicate that with the increase of PP grafting rate,the initial thermal decomposition temperature(Tonset),and the maximum thermal decomposition rate temperatures in the first and second decomposition stages(T1max and T2max)increase.The DSC test results indicate that with the increase of grafting rate,the crystallization temperature(Tc)of the sample changes little,while the enthalpy change of melting(ΔHm)and crystallinity(Xc)first increase and then decrease.SEM results show that as the grafting rate increases,the grooves and gaps on the surfaces of PP-g-AHB gradually decrease,and the surfaces become smooth and flat.PP-g-AHB was added into PP,obtaining the PP-g-AHB/PP composite material.The resulting composites and pure PP sheets were subjected to the UV stability studies.The results show that when the UV irradiation time reaches 384 h,compared with the unirradiated PP,the tensile strength and elongation at break of PP respectively decrease by 85.6%and60.9%.However,compared with the unirradiated PP-g-AHB/PP composite material,the tensile strength and elongation at break of PP-g-AHB/PP composite material respectively decrease by 46.1%and 35.1%.The PP-g-AHB/PP composite material has a great UV stability.
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