Preparation And Properties Of Elastomer Toughened Semi-aromatic PA 12T Composites

Semi-aromatic nylon 12T is a new breed of high temperature resistant nylon developed by Zhengzhou University.The existence of aromatic structure enables it to possess higher hardness and modulus,remarkable heat resistance and lower hygroscopicity compared with ordinary aliphatic nylon.However,the aromatic structure restricts the movement of the polymer chain and reduces the notch impact performance of the material.Therefore,it must be toughened to meet the requirements of application in pipe industry,and the blending modification of nylon and elastomer is the most simple and effective method at present.Considering cost and toughening effect,firstly,the POE-g-MAH was selected to toughen the PA12T.The influence of the time on the impact strength of the blend notch was studied,and the influence of POE-g-MAH content on the mechanical properties,thermal properties,water absorption and aging resistance of the blends were analyzed.The results show that the notch impact strength of the blends increases initially and then decreases with the increase of POE-g-MAH content,and the notch impact strength of the blends reaches the maximum value of 84.3 kJ/m~2(not thrust)at15%addition of POE-g-MAH which is 23.4 times that of pure PA12T.As the POE-g-MAH content increases to 35%,the tensile strength,flexural strength,thermal deformation temperature and hardness of the blends reduce to 49.8 MPa,24.4 MPa,113℃and 60 D with the retention rates at 61.5%,39.7%,92.6%and 77.9%,respectively.The melting point and crystallization temperature of the blends shift in the direction of high temperature,which indicates that the addition of elastomers promotes the crystallization of PA12T in the blends.The SEM study on the impact section of the blends shows that with the increase of POE-g-MAH elastomer content from 5%to 25%,the average particle size of the dispersed phase POE-g-MAH gradually reduces from 0.79μm to 0.3μm,and the blends have a brittle and ductile transition,which leads to an increase in the toughness of the blends.However,with continuing increase of the elastomer content to 35%,the size of the elastomer particle will cause the shear band to swallow the elastomer particles,which hinders the toughening effect of elastomer particles and leads to the up-and-down in the notch impact strength of the blends.The toughening effect of POE-g-MAH and EPDM-g-MAH in toughening PA12T was compared,and the results are shown as follows:The notch impact strength of the blends reached the maximum 65.2 kJ/m~2(not thrust)when the EPDM-g-MAH content was 25%,and with the increase of EPDM-g-MAH content,the tensile strength,flexural strength,thermal deformation temperature and hardness of the blends are gradually reduced.SEM observation of the impact section of the blends shows that with the increase of the EPDM-g-MAH elastomer content,the average particle size of the dispersed phase EPDM-g-MAH gradually reduces from0.74μm to 0.24μm,which leads to the decrease of the notch impact strength of the blend.The toughening effect is the best with the elastic body size at around 0.3μm when the ratio of the elastic is at 25%.The addition of SEBS-g-MAH elastomer without unsaturated double bond is studied since EPDM-g-MAH/PA12T contains unsaturated double bonds,which results in rapid decline of performance after thermal oxygen degradation.The results show that the notch impact strength of the blends increases at first and then decreases with the increase of SEBS-g-MAH content.The notch impact strength reaches the maximum at 80.7 kJ/m~2(not thrust)when the SEBS-g-MAH content is at 15%.The results show that POE-g-MAH has the best toughening effect on PA12T with and the lowest price,SEBS-g-MAH the second with the highest price,and EPDM-g-MAH the worst,which is not resistant to heat and oxygen aging.