Study On Post-Crosslinking-Hydrolyzing Copolyacrylonitrile Fiber And Its Water Absorption Property

Acrylonitrile (AN) potential crosslinking agent (NHMA)and methylmethacrylate (MMA) as monomer, dimethyl sulfoxide (DMSO) as solution and azo-bis-isobutyronitrile (AIBN) as initiator, the spinning dope was obtained by solution polymerization technique. It was then spun using wet spinning method and a kind of copolyacrylonitrile fiber with selfcrosslinking ability(CPAN) were made. Being post-crosslinked, fibers with crosslinking structure(CPAN-C) were got. Under proper hydrolyzing conditions, a new kind of copolyacrylonitrile fiber with high water absorbency and high water retention(CPAN-H) was prepared. Composite nonwovens with CPAN-H fibers were prepared by thermal bonding and needle punching respectively.When AIBN was controlled to be 0.5wt% of monomer , the monomer amount was controlled to be about 20wt% and the polymerization was under 60-70℃ for 8-10h, the spinning dope with good spinability was obtained. Using 40wt% DMSO solution as coagulation bath, CPAN fibers with good properties were got under room temperature. After heat-treated in boiling water bath, the inner stress in CPAN fibers was relaxed and the fibers showed good size stability during post-crosslinking and also showed high moisture absorption with the standard moisture regain to 8wt%.The principles of NHMA crosslinking were studied. The fibers with 10wt% NHMA got perfect crosslinking structure with little property destroyed when the post-crosslinking temperature and crosslinking time were controlled to be 170℃ and 10min respectively. When the amount of NHMA reached 10wt%, CPAN-H fiber arrived at its highest water absorbency at about 50g/g. And the more the amount of NHMA reached, the higher the water retention of CPAN-H fibers would have.The effects of hydrolyzing conditions such as NaOH concentration and hydrolyzing time on water absorbency of CPAN-H fibers were studied. And 20wt%NaOH solution, 10wt% NHMA and hydrolyzing for 3min was the optimizing condition to prepare CPAN-H fibers. The CPAN-H fibers obtained under this condition had high water absorbency of 25g/g and high water retention of 22.15wt%.The composite needle punched nonwovens obtained using these CPAN-H fibers had the water retention more than 90wt% in this reseach.The influences of the amount of NHMA, post-crosslinking conditions and hydrolyzing processes on the chemical structure of the fiber, the surface structure of the fiber, assembling state of the moleculars in the fiber and the mechanic properties of the fiber were also discussed using FTIR, SEM, TGA, DSC and DMA.