共聚单体对水相合成聚丙烯腈及其湿纺纤维结构与性能的影响

Effects of Comonomers on the Structure and Properties of Aqueous-synthesized Polyacrylonitrile and the Wet-spun Fibers

水相自由基聚合具有快速、高效的特点,是开发大规模、低成本的聚丙烯腈(PAN)基碳纤维原丝生产技术的首选工艺。本文采用该工艺制备了丙烯腈-衣康酸(P(AN-IA))和丙烯腈-醋酸乙烯酯(P(AN-VAc))两种共聚物,再经溶解和湿法纺丝将其制成纤维。采用傅里叶变换红外光谱仪(FT-IR)、场发射扫描电子显微镜(SEM)、旋转流变仪、旋转粘度计、X-射线衍射仪(XRD)和差式扫描量热/热重同步分析仪(DSG/TG)对比研究了两种共聚单体对水相合成PAN聚合物及其湿纺纤维结构与性能的影响。结果表明,与醋酸乙烯酯(VAc)相比,衣康酸(IA)降低了PAN聚合物的颗粒团聚程度和溶液粘度,显著提高了PAN纤维的截面圆整度和结构致密性,大幅降低了热稳定化反应起始温度、提高了热稳定性。这主要归因于IA的两个羧基基团。其改善了PAN聚合物的亲水性,使凝固过程更加缓和;减弱了氰基间的作用力,提高PAN分子链的运动性;能够诱导氰基在低温下发生环化反应。

Aqueous free-radical polymerization is a fast and highly efficient technique and the first choice for the development of large scale and low cost polyacrylonitrile （PAN） based carbon fiber precursor. Acrylonitrile-itaconic acid copolymer （P（AN-IA）） and acrylonitrile-vinyl acetate copolymer （P（AN-VAc）） were prepared using this technique, and then dissolved and spun into fibers by a wet spinning technique. Effects of the two comonomers on the structure and properties of the PAN polymers and fibers were studied by using Fourier transform infrared spectrometer （FT-IR）, field emission scanning electron microscope （SEM）, rotational rheometer, rotational viscometer, X-ray diffraction （XRD） and differential scanning calorimeter/synchronous thermogravimetric analyzer （DSG/TG）. The results show that compared with VAc, IA has reduced the degree of aggregation of PAN particles and the solution viscosity of PAN solutions, and has significantly improved the roundness and compactness of PAN fibers, and has greatly reduced the starting temperature of the stabilization reactions and improved the thermal stability. This is mainly attributed to the two carboxyl groups of IA, which has improved the hydrophilicity and moveability of PAN polymers, and can induce the cyclization reaction of nitrile groups under a lower temperature.