Medical Grade Polypropylene Blending Modification For The Purpose Of Meeting Two Sterilization Methods

The safety of medical materials is related to the health of the patients.The traditional materials polycarbonate(PC)are mostly synthesized from bisphenol A by different means.However,in the process of producing PC,bisphenol A may be remained,which brings great potential safety hazard to the patients.As a versatile plastic with good comprehensive properties,Polypropylene(PP)is the preferred material to replace PC in the medical field.In this paper,the crystallization properties and rheological properties of three kinds of PP(5090T,5090R and K1P38)provided by enterprises are analyzed,above three kinds of PP materials are sterilized by irradiation(22kGy)and moist heat.The changes of the molecular chain structure,crystallization energy,mechanical properties and thermal properties of the three PP materials after two kinds of sterilization methods are studied.According to the performance characteristics of the three kinds of PP materials after sterilization treatment,two kinds of PP materials were selected for blending modification,and the performance changes of the PP materials were studied after the blending modification.And the blend PP was sterilized to explore the performance changes after sterilization.The results showed that:The molecular chain of copolymerized polypropylene 5090T and 5090R is tangled seriously,which contain two kinds of crystal form,namely?and?,low crystallinity,low tensile strength,bending strength and heat resistance,but the impact strength is high.The molecular chain of homopolymer polypropylene(K1P38)is arranged regularly,which has only one form of crystal,high crystallinity,high tensile strength,bending strength and heat resistance,but the flexural modulus and impact strength are small.The molecular chain of three kinds of PP materials is broken after irradiation sterilization,no polar groups were generated,the crystallinity increased,tensile strength,flexural strength,flexural modulus and heat resistance increased,but the impact strength decreased.Moist heat sterilization is equivalent to annealing treatment,which makes the chains in amorphous and amorphous regions tend to be regular,and the crystallinity increases.However,there are still a lot of amorphous regions in 5090T and 5090R after the moist heat sterilization,which results in a relatively small increase in the percentage of crystallinity and a small increase in mechanical properties and heat resistance.The toughness of the amorphous region in the high elastic state can increase the impact strength.After moist heat sterilization,the crystallinity of K1P38increased,the tensile strength,flexural strength and heat resistance increased,but the impact strength decreased compared with that before sterilization.The UV absorbance value of5090T after irradiation sterilization is greater than the medical safety standard.It will be harmful to the human body.The UV absorbance value of 5090R and K1P38 before and after sterilization are all within the medical safety standard.The crystallinity of 5090R and K1P38 blend PP decreases with the increase of 5090R content.The blend ratio are 7:3 and 9:1,Due to the high content of Ethylene copolymerized monomers,?-modification can be generated,leading to the exitence of?-and?-modifications in B-7:3 and B-9:1.The tensile strength,flexural strength and flexural modulus of blend PP all decrease with the increase of 5090R content,while the impact strength increases with 5090R content increasing.The presence of ethylene copolymers on B-7:3 and B-9:1 molecules leads to a large proportion of the amorphous region,which is in a high elastic state at normal temperature.The absorption energy can be toughened and the impact strength increases greatly.Irradiation sterilization and moist heat sterilization did not change the crystal form of blend PP.Irradiation sterilization can promote crystallization,cause the crystallinity increases,the tensile strength,flexural strength,flexural modulus and heat resistance are enhanced,impact strength decreased.After irradiation sterilization,the mechanical properties of blend PP mixed with 7:3 and 9:1 meet the medical standard polypropylene copolymer materials.Moist heat sterilization is equal to annealing process.Moist heat sterilization is equivalent to annealing treatment,resulting in a larger crystallinity of the blend PP,a large increase in tensile strength and bending strength,good heat resistance,but a decrease in impact strength.The impact strength of blending ratio of 5:5,7:3 and 9:1 is 3 KJ/m~2 to the medical standard of copolymerization of polypropylene after moist heat sterilization.After two sterilization processes,the UV absorbency of PP blend was lower than that of medical standard,with no safety hazard to human body.According to the standard of medical PP material and the performance characteristics of three kinds of PP material itself,the blending PP material with the blending ratio of 7:3 is finally determined by the mechanical properties of the two kinds of sterilization before and after sterilization and the UV absorbance value after sterilization all reach the standard of copolymerization polypropylene,which is the best blending ratio of the comprehensive performance.