Preparation And Characterization Of PA6-PA66-PEG Tercopolymer And Its Composites

Nylon elastomers,known as polyamide(PA),are formed by copolymerization of polyether and polyamido.The hard segments are usually composed of PA6,PA11 and PA12.It has the characteristics of low temperature resistance,wear-resistant,high strength,high-resilience and high elongation.It is widely used in many fields such as auto parts,medical equipment,sports and daily necessities.In this study,PA6-PA66-PEG copolymer was prepared by introducing PA66 chain segments in the hard segments.And then PA6-PA66-PEG nanocomposites containing CNTs and OMMT were respectively prepared,by in situ copolymerization.Specific findings are as follows:(1)Melting copolymerization of caprolactam,PA66 salt and polyglycol(PEG)was carried out in stainless steel reaction kettle.The infrared spectroscopy showed that the characteristic absorption peaks of ester group and PEG hydroxyl group appeared in the spectra of the reaction products,indicating that PEG was fully involved in copolycondensation reaction.DSC tests showed that the melting point,crystallization temperature and crystallinity of PA6-PA66-PEG copolymer decreased with the increase of PA66 content.TGA tests showed that the thermal stability was best when PA66 content was10-15 wt%.The tensile strength and breaking elongation of PA6-PA66-PEG triplets increased with PA66 content,and decreased with PEG content.The tensile strength of the copolymer was 18.8 MPa and the elongation was 54.1 %,with the best mechanical properties.When the soft-hardness ratio of PA6-PA66-PEG copolymer was 30/70,its tensile strength and breaking elongation were 28.6 MPa and 450.2 % respectively,which were the best in all of the composites.(2)Using carboxylated carbon nanotubes(CNTs-COOH)as modifier,PA6-PA66-PEG/CNTs-COOH nanocomposites containing 0.3 wt%,0.5 wt%,1 wt% of CNTs and 30 wt% of PEG were prepared by in situ melt copolymerization.XRD results showed that the crystal shape of the composites did not change,and the crystallization temperature increased with the increase of CNTs-COOH content.(3)Using organic montmorillonite(OMMT)as modifier,the PA6-PA66-PEG/OMMT nanocomposites with 0 wt%,0.3 wt%,0.5 wt% and 1 wt% of OMMT were prepared by in situ melt copolymerization respectively.DSC and mechanical tests showed that the crystal temperature,melting point and tensile strength of nanocomposites were higher than those of ternary composite materials with the increase of OMMT content.The results of TGA showed that PA6-PA66-PEG/OMMT nanocomposites containing 0.1 wt% of OMMT had the most residue after thermal decomposition,and its thermal stability was better than that of ternary copolymer and other composites.