Air‐laid and foam‐laid nonwoven composites: The effect of carrier medium on mechanical properties

Abstract

Thermoplastic nonwoven composites were produced with the air‐laying and foam‐forming processes from cellulosic and plastic fibers. The two raw material combinations were (1) PP/PE (fiber length 3 mm), PP/PE (12 mm), fluff pulp fibers (2 mm) and (2) PP/PE (3 mm), fluff pulp fibers, viscose (10 mm). After forming, the fibrous sheets (400 gsm) were bonded with heat pressing (145°C). The effect of the carrier medium, air or aqueous foam, on the tensile and impact properties and sheet structure was explored. The air‐laids differed from the foam‐laids by sheet anisotropy, density, and the lack of an additional bonding regime between wood fibers due to the dry forming process. The PP/PE bonding fibers gave the air‐laids a good capacity to elongate compared to the foam‐laids. The advantage was lost when nonbonding viscose was added. The impact strength was dependent on the PP/PE dosage and the sheet density, rather than the moisture‐induced bonding between wood fibers. The changing long/short fiber ratios caused gradual shifts in sheet properties, usually a reduction in a mechanical property as the share of short fiber increased in the mix. Economic analysis revealed that increasing fluff content can reduce raw material costs, providing a possibility for cost optimization in total production costs.