Rheological and Thermo-Mechanical Characterisation of Sustainable Polypropylene Composites Reinforced with Micronised Rice Husk

resumo

The growing demand for sustainable materials in construction and sanitation has increased interest in natural fibre-reinforced polymer composites. Rice husk, an abundant agricultural by-product, offers a promising alternative as a reinforcing filler in polypropylene (PP) composites. This study aims to assess the suitability of PP composites reinforced with micronised rice husk particles for application in sanitary components. Two formulations containing 20% and 30% rice husk were developed and characterised. Comprehensive analysis included morphological, thermal, rheological, mechanical, hygroscopic, and tribological testing. Results showed that particles incorporation enhanced thermal stability and crystallinity due to a nucleating effect, with the 30% composite showing higher crystallinity. Thermogravimetric analysis showed that although the T5% decreased from 374.1 degrees C for neat PP to 309.2 degrees C and 296.2 degrees C for the 20% and 30% composites, respectively, the DTG peak temperatures increased by 15.9 degrees C and 17.6 degrees C, indicating a delayed main decomposition stage of PP matrix and enhanced overall thermal stability. Rheological behaviour revealed increased viscosity and pseudoplasticity at higher particle content Mechanical characterisation showed an increase in Young's modulus from 1021 MPa for neat PP to 1065 MPa (+4%) and 1125 MPa (+10%) for PP_Rice_20% and PP_Rice_30%, respectively. In contrast, the nominal strain at break dropped sharply from 238% (PP) to 30% (PP_Rice_20%) and 16% (PP_Rice_30%). Shrinkage decreased from 1.31% (PP) to approximately 1.05% in both composites, indicating improved dimensional stability. However, water absorption rose from 0.015% (PP) to 0.111% (PP_Rice_20%) and 0.144% (PP_Rice_30%), accompanied by an increase in surface roughness (Sa from 0.34 mu m to 0.78 mu m and 1.06 mu m, respectively). The composite with 20% rice husk demonstrated better filler dispersion, reduced water uptake, and smoother surfaces, making it more suitable for injection-moulded components intended for use in humid environments. Overall, the study supports the use of agricultural residues in high-performance biocomposites, contributing to circular economy strategies and the development of more sustainable polymer-based materials for technical applications.

palavras-chave

MECHANICAL-PROPERTIES; THERMAL-PROPERTIES; PARTICLE-SIZE; WOOD; VISCOSITY; DEPENDENCE; ROUGHNESS; BEHAVIOR

categoria

Materials Science

autores

Santos, I; Zhiltsova, T; Oliveira, JM; da Silva, SPM; Oliveira, MSA

Grupos

G4 - Materiais Renováveis e Economia Circular

Projectos

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

agradecimentos

This research was funded by PRR-Plano de Recuperac & atilde;o e Resiliencia, under the Next Generation EU from the European Union, through the Project "Agenda ILLIANCE" (C644919832-00000035|Project n degrees 46), and by national funds through FCT-Fundac & atilde;o para a Ciencia e a Tecnologia, I.P., under the project UID 00481/2025-Centre for Mechanical Technology and Automation, https://doi.org/10.54499/UID/00481/2025. This work was also supported by CICECO-Aveiro Institute of Materials (UIDB/50011/2020, DOI: 10.54499/UIDB/50011/2020; UIDP/50011/2020, DOI: 10.54499/UIDP/50011/2020; LA/P/0006/2020, DOI: 10.54499/LA/P/0006/2020) and by LAQV-REQUIMTE (UIDB/50006/2020; UIDP/50006/2020), financed by national funds through FCT/MCTES (PIDDAC).