Preparation of high-relative molecular mass PPTA precipitated fiber by chain extension reaction
Using terephthalamide(TPC)and p-phenylenediamine(PPDA)as monomers,carboxyl terminated and amino ter-minated poly(p-phenylenediamine)(PPTA)solutions were prepared by copolymerization reaction.The two solutions were mixed evenly in equimolar ratio to produce PPTA precipitated fibers with both carboxyl and amino terminated groups by direct precipita-tion method.And high-relative molecular mass PPTA precipitated fibers were prepared by high-temperature heat treatment and chain extension reaction.The copolymerization,precipitation and chain extension reaction conditions were studied.The results showed that the optimal monomer molar ratio for copolymerization reaction was 0.985,and the inherent viscosity(η)of carboxyl terminated and amino terminated PPTA solutions were 2.78 dL/g and 2.54 dL/g,respectively,and the η of the solution did not change significantly and reached 2.73 dL/g after mixing the two solutions;the stirring speed of the precipitation disperser was controlled at 2 000 r/min during the precipitation process,resulting in good fiber forming properties,and the PPTA precipitated fibers exhibited a membranous structure with a high aspect ratio;and the η of PPTA precipitated fibers increased from 2.73 dL/g to 4.21 dL/g,the relative molecular mass was significantly increased,and the thermal stability was also improved after the chain extension reaction at 300℃for 60 min.
aramid paperpoly-p-phenylene terephthamideprecipitated fiberchain extension reactionrelative molecular mass
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