Study On Structure And Properties And In-situ Fiber Formation Of Reactive Polymer/MCOA6 In-situ Composites

In-situ polymerization technology to prepare MCPA6 composite is a method to effectively modify MCPA6.Adding a small amount of second-component reactive polymer have a great impact on the structure and properties for MCPA6 in-situ composite system.In this paper,two kinds of MCPA6 in-situ composite sheets with different structure and content of reactive polymer were prepared by anionic polymerization of caprolactam and the structural changes and properties of MCPA6 in-situ composite were further studied without destroying the original structure inside the sample that were prepared through cutting the sheets.At the same time,the phenomenon of "in-situ fiber formation" in MCPA6 in-situ composites was discussed.Firstly,flexible TPEU was introduced into the in situ polymerization of caprolactam to prepare TPEU/MCPA6 in-situ composite system with different TPEU content.The molecular chain structure,molecular weight,compatibility,and structural changes in the crystalline and amorphous regions of the composite system were determined by modern analytical techniques such as FTIR,DSC,DMA,SAXS and SEM et al.The results showed that TPEU-co-MCPA6 copolymer was produced in this system,and its molecular weight decreased with the increase of TPEU content.The compatibility of TPEU and MCPA6 was significantly improved due to homogeneous at the macroscopic level,and only one glass transition temperature can be observed in DMA,but the phase separation with microscopic lever still exist in the system.TPEU has an inhibitory effect on the crystallization of the matrixbecause of crystallization temperature and the degree of crystallization improvement decrease with the increase of the TPEU content,but the addition of 0.25% and 1% TPEU increases the crystallinity of the matrix by 6.9% and 3.9%.At the same time,TPEU promoted the mobility of the molecular chain of the composite system,and the density of the amorphous region gradually decreased,indicating that the free volume of the system increased.The toughness of the material was significantly improved,and the elongation at break of the 10% TPEU/MCPA6 composite system increased by 147%.Subsequently,we first used PAR as macromolecular activator to introduce rigid PAR into MCPA6,and prepared PAR/MCPA6 in-situ composite system with different content of PAR.The effect of catalyst content change on the composite was studied and the polymerization mechanism was discussed.The results showed that the reaction of PAR-co-MCPA6 copolymerization and cross-linked side reaction occurred in the polymerization process,the molecular weight decreased w ith the increase of PAR content.The crystallization rate can be promoted with 1%PAR,but continued increase of PAR hinders the crystallization of the matrix,and the degree of crystallization is gradually reduced.10%PAR system produced a crosslinked network structure.Microphase separation has been proved exist in amorphous phase of the composite system,which the density decreases first and then increases.The introduction of the rigid PAR molecular chain reduces the mobility of the molecular chain,and the rigidity and modulus of the material are improved.The elastic modulus is increased by 29% at 2.5% PAR content,and the tensile strength and modulus are increased by 20% and 33% respectively with adding the microactivator TDI.Based on the microfiber formed on the above two MCPA6 in-situ composite systems,combined with the study of its structural changes and many analysises of previous studies.The mechanism of microfibers that commonly found in MCPA6 in-situ composites was inferred.As a result,it is considered that the molecular weight reduction of the MCPA6 in-situ composite system,the fluffiness of the amorphous struct ure,and the formation of microphase separation have a significant effect on the formation of microfibers.