Characteristics of aramid fibre/fibrids and their properties for sheet making

Fibres and fibrids (or pulps) produced from aromatic polyamide (PMIA, m-aramid) can be made into insulation sheet materials by a wet forming process. The aramid fibres offer mechanical strength for the sheet, while aramid pulps often act as binder. Morphological and bonding properties of PMIA fibres and fibrids are very important for the mechanical and dielectrical properties of the aramid sheet. The microstructural features of aramid fibres and pulps were characterized by using light microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aramid fibres were not hollow and nearly circular in shape. The aramid pulp exhibited a ribbon-like shape in light microscopy (LM) and SEM, while grain like in AFM, which indicated that the fibrids were highly fibrilized by the manufacturing process. The fibre length, curl and kink index were investigated with fibre quality analyzer (FQA). Fibre screening analysis was performed for the aramid pulp. The effect of the furnish proportions on sheet properties and structure were analyzed. An optimal furnish ratio of 1.5:1 was obtained.