Preparation and properties of thermal insulation felts for firefighting protective clothing

In this paper, preoxidized fibers, flame-retardant acrylic fibers and polyphenylene sulfide (PPS) fibers were chosen to prepare thermal insulation felts by the spunlaced process. The preparation of thermal insulation felts by single-component fibers, bicomponent fibers and multi-component fibers was studied. The breaking strength of the single fibers, flame retardancy, thermal conductivity, air permeability, thermal stability, shrinkage rate after washing, and the breaking strength of the thermal insulation felts were characterized. The results show that, for the single-component felts, preoxidized fiber felt had a longitudinal char length of only 35 mm, which was less than that of flame-retardant acrylic fiber felts and PPS felts. However, its longitudinal breaking strength was only 39.8 N. The bicomponent thermal insulation felt, blended with flame-retardant acrylic fibers and preoxidized fibers, had a higher breaking strength than the single-component felt, but it had char lengths greater than 100 mm after the vertical burning test. When the ratio of the multi-component insulation felts (preoxidized fibers, PPS fibers and flame-retardant acrylic fibers) was 35:60:5, the felt’s longitudinal char length measured 23 mm, which was less than that of the aramid felt 72 mm. This felt’s thermal conductivity was 0.0515 W/mK. It had an air permeability of 1995 mm/s, and the longitudinal dimensional shrinkage rate following the thermal stability test was only 1.1%. Multi-component thermal insulation felts are very important for the development of high-performance firefighting protective clothing.