Design,Preparation,and Properties Of Long Carbon-chain Polyamide Elastomer

Long carbon-chain polyamide（LCPA）and long carbon-chain polyamide elastomer（LCPAE）have wide development prospects because of their excellent low-temperature resistance,physical-mechanical properties,outstanding wear resistance,chemical resistance,and good molding performance.However,due to the late start of domestic research,high technical barriers,and foreign patent monopoly,the global market for the above two high-end polyamide materials is basically monopolized by foreign companies,which makes China mainly relies heavily on imports and needs major breakthrough urgently.Based on this,this subject first developed an LCPA preparation method with independent intellectual property rights,and prepared LCPA1210 material with excellent performance.On this basis,innovative breakthroughs have been made to prepare LCPAE materials,whose performance is close to that of foreign products of the same type.This technology can not only break the foreign monopoly,but also strongly support the development of domestic related fields and the demand for high-end polyamide materials,which displays important significance and practical value.（1）Firstly,LCPA1210 was prepared by"one-step"method,which eliminated the traditional salt-forming step and improved the production efficiency.A series of structure and property characterizations were carried out on the obtained products.FTIR,¹H NMR and GPC results showed that LCPA1210 was successfully synthesized and had an ideal number-average molecular weight（25450 g/mol）,which verified the feasibility of"one-step"method in preparing LCPA and offered an experimental basis for the subsequent preparation of carboxyl-terminated LCPA1210 prepolymer（LCPA1210d C）;DSC,TGA and DMA results showed that LCPA1210 had good heat resistance and thermal stability,as well as excellent low-temperature resistance;mechanical properties and water absorption tests showed that LCPA1210 possessed excellent mechanical properties,low water absorption of 0.2887%,and good dimensional stability.（2）Secondly,LCPA1210d C with ideal chemical structure and molecular weight was prepared by the above"one-step"method and used for the subsequent synthesis of LCPAE.Then,due to the complicated situation of the"two-step"polymerization process in synthesizing LCPAE,the pre-polymerization time,the vacuum pumping time,molding method,reactive equipment,and additive system in polymerization craft were optimized through a large number of experimental investigations and product analysis in two stages（preliminary exploration stage and amplification exploration stage）during the laboratory.And consequently,a better LCPAE polymerization craft that could be used for further amplification was obtained.（3）Finally,based on this polymerization craft,two kinds of LCPAE with different contents of soft and hard segments were prepared,and then a series of structure and property analyses were carried out on the obtained LCPAE.FTIR,¹H NMR and GPC results demonstrated the successful synthesis of two LCPAE with desirable number-average molecular weights（both exceeded 21,000 g/mol）.Thermal tests showed that both LCPAE owned excellent thermal stability(T_5%exceeded 340℃and T_50%exceeded 400℃),and T_maxincreased with the increase of hard-segment content.In addition,the prepared LCPAE-2 displayed excellent mechanical properties at room temperature（tensile strength and elongation at break reached 15.5 MPa and 780%,respectively）.More importantly,compared with normal temperature,the low-temperature tensile test showed that the tensile strength and elongation at break of LCPAE-2 only decreased 9.7%and 11.5%at-55°C,respectively,showing an extremely excellent low-temperature resistance.This is expected to further expand the application of LCPAE in the low-temperature field,which has extensive development potential.