A Study On Preparation And Properties Of Carbon Nanotubes Modified By Functionalized PPTA

Since their discovery,carbon nanotubes(CNTs)have attracted great attention in the past decades for their applications in various fields of materials science.In particular,they are considered to be ideal candidates as mechanical reinforcement for polymers due to their desirable mechanical properties such as high strength,high modulus and rigidity,very low density,and ultra-high aspect ratio.CNTs are expected to play an important role in the future of advanced polymer composites.Many previous studies have indicated that as reinforcement fillers for composites,CNTs should be surface modified in order to reduce the formation of aggregates,which lead to the decrease of the polymer-nanotube interfacial stress transfer.Up to now,there are reports of many routes to achieve surface modification of CNTs,Among different polymers used to modify CNTs,poly(p-phenyleneterephthalamide)(PPTA),also known as Kevlar,has generated great interest because it is a well-known high-performance polymeric material having many excellent properties such as high tenacity,high modulus,and light weight.PPTA has found applications in many fiber-reinforced composites used in aviation,aerospace,military,automobile,ballistic fabrics,mechanical,petrochemical and other fields.The combination of two ultra-strong materials,i.e.PPTA and CNTs,is expected to generate a synergistic effect for reinforcing various polymer materials.This article will epichlorohydrin grafted to the surface of PPTA,got some columns epoxidation degree of PPTA-ECH-x.Thermogravimetric analysis showed that the epoxidation of aramid fiber thermal stability is reduced,and with the increasing of the degree of epoxidation,stability is worse and worse;Infrared spectrum analysis showed that the 1544 cm-1 N-H key bending vibration peak peak weakened with the increasing of the epoxidation level gradually,even when the maximum epoxidation degree,peak almost disappear;By transmission electron microscopy(SEM)show that with flower oxidation degree increasing,into the root of nanofibers into nanometer fiber ball.Next,we use physical methods and chemical methods respectively with PPTA-ECH-x to modify carbon nanotubes(MWNTs)and amino carbon nanotubes(MWNTs-NH2)group,the functionalization of aramid fiber series of physical modification of carbon nanotubes material namely PPTA-ECH-MWNTs-x and functionalization of aramidchemical modified amino series of carbon nanotubes material namely PPTA-ECH-MWNTs-NH2-x.By thermogravimetric analysis showed that the thermal stability of the modified carbon nanotubes is stable,and had been calculated by weightlessness than coated on the surface of the carbon nanotubes,the content of PPTA-ECH as epoxidation degree increasing,the content of PPTA-ECH also in unceasing increase,this may be led to increased levels of ECH PPTA-ECH content increases.Transmission electron microscopy(SEM)analysis showed that the modification of carbon nanotubes wall becomes coarse and wall thickening,PPTA-ECH of success coated to the surface of carbon nanotubes.XPS analysis success proves PPTA-ECH took the form of chemical bonding grafted onto the surface of the amine carbon nanotubes by PPTA-ECH-MWNTs-NH2-x material.In this paper,MWNTs were covalently and non-covalently coated by N-epoxypropyl PPTA(PPTA-ECH)to prepare PPTA-ECH-MWNTs-NH2-x and PPTA-ECH-MWNTs-x,which were used as additives to reinforce PVC composite films.It was found that the yield strength,Young ’ s modulus,and toughness of PPTA-ECH-MWNTs-NH2-x/PVC composite films increased by113.64~227.84%,73.81~201.56%,and 229.77~589.96%,respectively,in comparison to pure PVC,while those of PPTA-ECH-MWNTs-x/PVC composite films increased by 158.01~215.08%,45.79~153.13%,and 311.21~540.81%,respectively.The maximum yield strength,maximum Young ’ s modulus,and maximum toughness of both PPTA-ECH-MWNTs-NH2-x/PVC and PPTA-ECH-MWNTs-x/PVC showed significant improvement as compared to PPTA-MWNTs/PVC composite film and PPTA-MWNTs-NH2/PVC.This indicates that N-epoxypropyl PPTA covalently and non-covalently coated MWNTs are promising additives for reinforcing PVC.And chemical modification to a slightly higher than the effect of physical modification.