Flame Retardant Polyolefins Using Fibers From Leather Waste: Adjusting Extrusion Variables to Balance the Property Profile

ABSTRACT The extrusion processing variables represent a key to the optimal use of additives and thus the development of flame‐retardant polymer composites. Adjusting the property profile, for example, finding a balance between flame retardancy and mechanical properties is the main challenge. In this work, the effect of blending temperature and rotational speed on physico‐mechanical properties and fire behavior of polyolefin composites was investigated. High‐density polyethylene or polypropylene was used as polymer matrices; the polymers were compounded by the extrusion process using industrial‐waste leather fibers as flame retardant adjuvant and commercial flame‐retardant additives. A detailed rheological analysis highlighted different viscoelastic behavior, that is, a predominant elastic or viscous one. The effect of the extrusion processing variables was also investigated on the morphology, mechanical properties, thermal decomposition, fire behavior under forced flaming combustion and flammability. Important improvements were revealed with respect to using only high loading of flame retardants. For high‐density polyethylene‐based composites, impact resistance and elongation at break increased 8 and 7.5 times, respectively. The total heat evolved (87 MJ/m 2 ), effective heat of combustion (31.6 MJ/kg), flame retardancy (UL 94 rating) results were comparable with the reference sample. Meanwhile for polypropylene composites, the impact resistance increased 2.2 times and the flame retardancy was improved from no rating in the UL 94 vertical test to V‐0 rating. Tailored processing was highlighted as an autonomous and powerful approach to achieve balanced and demanding properties.