Foam processability of polypropylene/sisal fiber composites having near‐critical fiber length for acoustic absorption properties

Abstract The current research aims to develop a sound‐absorbing material from polypropylene (PP) and sisal fibers (SFs). The study explores the foam processability of PP/SF composites with near‐critical fiber length, employing supercritical CO 2 ‐assisted batch foaming technology. Optimized foam processing conditions were determined to be 145°C, 100 bar, and 15 min saturation time. These conditions resulted in foams with the lowest density, maximum volume expansion ratio and an overall microcellular structure. Notably, increasing the fiber concentration significantly enhanced the compressive properties, exhibiting a remarkable 3000% improvement with the addition of 40 wt% SFs. Dynamic mechanical analysis further revealed improved dampening properties of the composites after foaming. Moreover, the incorporation of SFs led to an increase in the noise reduction coefficient, while foaming additionally improved the sound absorption properties. This renders the material highly applicable for soundproofing purposes. Thus, produced PP/SF microcellular foams offer properties that can potentially be used to produce lightweight structural components for acoustic absorption applications.