通过调节凝固浴温度和含量,制备了4种物理结构不同的聚丙烯腈(PAN)基薄膜和原丝,并采用正置金相显微镜和扫描电子显微镜对其截面形貌和内部结构进行分析,探讨了PAN基原丝物理结构对预氧化过程中氧气扩散行为的影响。结果表明:凝固浴含量较低时(二甲基乙酰胺质量分数50%),表层双扩散剧烈,纤维易形成致密的皮层,会限制氧气向原丝内部渗透,氧气需逐层扩散;凝固浴含量较高时(二甲基乙酰胺质量分数70%),表层双扩散缓慢,纤维皮层消失但会出现裂纹。经后续湿纺拉伸,这些裂纹虽在宏观上趋于闭合,但在分子层面仍可为氧气渗透提供通道,氧气沿纤维径向扩散。凝固浴温度升高时(37～57℃),双扩散比较充分,可改善纤维内外结构均匀性,且所得纤维截面形状趋于圆形,但该物理结构的变化对预氧化过程中氧气扩散行为的影响不明显。
In this study,four types of polyacrylonitrile (PAN)-based films and precursor fibers with distinct physical structures were fabricated by adjusting the temperature and concentration of the coagulation bath.Their cross-sectional morphology and internal structure were characterized using optical microscopy and scanning electron microscopy to investigate the influence of the physical structure of PAN-based precursor fibers on oxygen diffusion behavior pre-oxidation process.The results showed that at lower coagulation bath concentrations (50wt.% DMAC),intense bidirectional diffusion at the fiber surface led to the formation of a dense skin layer,which significantly hindered inward oxygen penetration,forcing oxygen to diffuse layer-by-layer.In contrast,higher bath concentrations (70wt.% DMAC) slowed the bidirectional diffusion at the surface,eliminating the skin layer but resulting in surface cracks.Although subsequent wet-spinning and drawing processes visually closed these cracks,they still provided molecular-level diffusion channels,allowing oxygen to diffuse radially through the fiber.Increasing the bath temperature (from 37℃ to 57℃) facilitated more balanced bidirectional diffusion,improving the uniformity of internal and external structures and yielding fibers with more circular cross-sections.However,this change in physical structure had a negligible effect on oxygen diffusion behavior during pre-oxidation process.
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基金资助
吉林省教育厅科学研究技术项目(JJKH20240318KJ)
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