Mechanical and thermal properties of polyisocyanurate rigid foams reinforced with agricultural waste

Abstract

Alternatives to polymer reinforcement, adding value to agro-industrial byproducts, are emerging to develop sustainable materials and cost-effective industrial applications. The present study was undertaken to assess the effect of adding 10% w/w of three different agricultural residues on the physical and processing properties of polyisocyanurate (PIR) rigid foams: rice husk (RH), banana rachis (RB), and African palm kernel shells (APKS). The reaction kinetics revealed that adding lignocellulosic reinforcement to the PIR system accelerated the reactions' initiation. However, after foaming, an opposite trend is observed. The PIR-fiber interaction is analyzed through Scanning Electron Microscopy, Fourier-Transform Infrared Spectroscopy, X-Ray diffraction, and thermogravimetric technique. The composites, prepared at a laboratory scale, were also tested for dimensional changes, compressive mechanical/physical properties, and thermal conductivity. The compression strength obtained for RH, BR, and APKS were 0.23 MPa, 0.12 MPa, and 0.16 MPa, respectively. In contrast, neat PIR exhibited a compression strength of 0.19 MPa, indicating that adding 10% w/w of agro-fillers affects the PIR compressive properties differently. Additionally, PIR reported an apparent density of 38 kg·m−3. While RB and APKS samples showed slightly lower density values, RH presented a 13% growth in this property. Although RH increased the thermal conductivity (lower thermal resistance), the values obtained still correspond to insulating materials. BR and APKS do not show significant variability in thermal conductivity/resistance. Providing tailored properties from different agro-waste opens a new family of PIR foam composites for structural or insulted applications.

Keywords

• PIR-Composite
• Natural fiber
• Fiber-reinforced composite
• Agricultural waste