The Radiation Effect Of Polypropylene And Its Application In Radiation Sterilization Of Medical Disposable Protective Clothing

Polypropylene(PP)is a semi crystalline thermoplastic polymer,which has the characteristics of light weight,heat resistance,excellent machining performance,chemical stability,corrosion resistance,non-toxicity and recyclability.It is one of the five general plastics,widely used in chemical industry,automobile industry,medical products and packaging materials.However,PP also has poor aging resistance,weather resistance and radiation stability.Most of radiation sterilization processes are exposed to air,and most of the polymer based medical devices will be degraded in different degrees in the air,which will damage the performance and safety of the products.Studying the radiation effect of PP in oxygen environment and evaluating the effect of radiation degradation and aging on the properties of PP can provide a theoretical reference for the parameter setting of the radiation sterilization process of medical devices with PP as the base material.In this paper,the effects of different absorbed doses of γ-rays on the structure and properties of PP were studied.At the same time,the disposable medical protective clothing with PP as the base material was selected as the research object to evaluate the effect of radiation sterilization dose on its structure and performance.The specific research contents and results are as follows:PP was irradiated by gamma ray at different absorption doses in air at room temperature.The color,chemical functional groups,crystallization properties,thermal stability,changes of free radicals and melt flow rate of PP before and after irradiation were characterized by solid-state ultraviolet absorption spectrum,FT-IR,DSC,TGA,ESR and MFR.It was found that the color of PP was yellow after gamma irradiation and deepened with the increase of absorbed dose,because of the formation of conjugated double bonds and other chromogenic groups.The yield of chromogenic group was less than 5%;The melting temperature and crystallinity of PP decreased with the increase of absorbed dose;The thermal stability decreased slightly with the increase of absorbed dose.After irradiation,the concentration of free radicals in PP depended on the absorbed dose of gamma irradiation,and alkyl free radicals and peroxy free radicals were produced;Gamma irradiation increased the melt fluidity of PP,which was attributed to the decrease of molecular weight due to PP scission.(2)Three kinds of disposable medical protective clothing A,B and C are made of PET/ PU,PP / PE and PE respectively.After 60 Co source gamma ray irradiation,the surface morphology of the three kinds of disposable medical protective clothing has no obvious change,and the surfaces of the three kinds of disposable medical protective clothing remains hydrophobic.Under the sterilization dose(≤ 50 k Gy),γ-ray radiation has little effect on the tensile strengths of protective clothing A,while the tensile breaking strength and elongation at break of protective clothings B and C decrease with absorbed dose,especially the tensile properties of protective clothing B lost a lot after irradiation.The results showed that the tensile breaking strength and elongation at break of PET /PU protective clothing decreased by 11.9% and stabilized at about 30% after a slight decrease;the tensile breaking strength of PP / PE protective clothing decreased to 40%The breaking strength and elongation at break of PE protective clothing hardly changed with the storage time.PET / PU and PE medical disposable protective clothing can be stored for 12 months after radiation sterilization.The amount of free radical produced by PET / PU protective clothing radiation is small,and no obvious free radical signal can be detected.The free radical concentration of PP / PE and PE protective clothing was positively correlated with the increase of absorbed dose.The free radical concentration decreased rapidly with the storage time and tended to be stable after one month.Therefore,after gamma radiation sterilization,the performance of PET / PU protective clothing is stable,while that of PE protective clothing is relatively stable.The tensile performance of PP protective clothing is greatly affected by the absorbed dose and aging in storage time.The gamma irradiation sterilization dose should not exceed 20 k Gy,otherwise,the performance can not meet the requirements of national standard.