Preparation Of Polar SBS Grafted Polymers And Its Application In Nylon Modification

SBS-g-MAH and SBS-g-GMA were prepared by melt grafting method to toughen PA66.The results of orthogonal experiments were listed as follows.As for SBS-g-MAH,types of SBS,content of MAH,type of initiator,content of flow modifier and melt grafting time were the key factors of content of gel.The loading amount of MAH,content of initiator and melt grafting time were the key factors of grafting degree.The loading amount of antioxidant and content of initiator were the key factors influencing grafting efficiency.When it came to SBS-g-GMA,the type of initiator was the key factor of content of gel while the type of SBS was the key factor which influenced grafting degree and grafting efficiency.The effects of monomer content on the properties of SBS/MAH,SBS/GMA grafts were investigated by twin screw melt processing based on the preliminary experimental formula.MAH 0.75phr,DTBP 0.05phr,SBS 100phr,the grafting gel content was 2.49%,the grafting rate was 0.62%,the grafting efficiency was 92.05%,and the comprehensive performance was the best.GMA 5 phr,DTBP 0.05 phr,SBS 100 phr,the grafting gel content was 0.86%,the grafting ratio was 1.97%,the grafting efficiency was 46.34%,and the comprehensive performance was the best.The melting index,tensile strength,bending strength and modulus of PA66 decreased to some degree after blended with grafts and the grafting degree had no significant influence on mentioned properties.SBS/GMA did not toughen PA66 because the polarity and reactivity of GMA were relatively weak leading to a poor dispersion in the PA66 matrix.Besides,impurities such as homo-polymer of GMA,additives may weaken PA66 for SBS/GMA did not get purified when blended with PA66.The impact strength of PA66 modified by SBS/MAH was enhanced from 4.922 kJ/m2 to 6.720kJ/m2 for the strong polarity of MAH and SBS-g-PA66 formed by the reaction between amine of PA66 and carboxyl derived from hydrolysis of MAH.Among four selected toughening agent SB S-g-MAH,POE-g-MAH showed best toughening effect When the addition amount was 30phr,the impact strength of PA66 was improved about 2.5 times.Compared with SBS-g-MAH,POE-g-MAH had less effect on tensile strength,bending strength and bending modulus,Therefore,POE-g-MAH was the best toughening agent in the test range.Adopting portable pH meter instead of indicators optimized the chemical titration.Not only errors caused by operator but also the system error induced by indicator were decreased and the accuracy and repeatability were enhanced.