Adhesion characteristics of aramid fibre-fibrids in a sheet hot calendering process

Aramid sheets can be manufactured entirely of synthetic poly (m-phenylene isophthalamide), which is made into two forms, aramid short fibres (floc) and fibrids. The two gradients are mixed and formed into aramid sheets by a wet papermaking process. The mechanical properties of sheets depend on fibrids fineness, fibre length, fibre arrangement, and the state of combination between aramid fibre and fibrids. Structural differences resulting from differences in sheet manufacturing also contribute to sheet properties. The present paper reports on the response of mechanical properties and the microstructure of an aramid sheet to the hot calendering process. Sheet density, tensile, and elongation were improved considerately by factors of 4, 5 and 7 times, respectively in the hot calendering process. Scanning electron microscopy (SEM) observation shows that the surface of the sheet becomes much smoother due to the melting of some of the fibrids in the sheet, which also contributes to a stronger adhesion between the fibres and fibrids. Fibres were deformed more than 20% by calendaring and the surfaces of fibres pulled out from the sheets were clean. Hydrogen bonding was confirmed to be mainly responsible for the adhesion, using Fourier transform infrared spectroscopy (FTIR).