Agro-waste Capsicum Annum stem: An alternative raw material for lightweight composites

The global need for sustainable and eco-friendly materials had created a demand in industries for raw material supply. In this context, an attempt was made to extract Capsicum Annum stem fibers (CASF) from the agro-waste of Capsicum Annum stem (CAS) as an alternative resource of raw material. The extracted CASF was subjected to NaOH, and oxalic acid treatments, to study the effect of chemical treatments on the physical, chemical, thermal and mechanical properties. These physico-chemical properties were analyzed through pycnometer experimentation, chemical analysis, XRD, FTIR, and morphological analysis. The thermal properties were analyzed through thermogravimetric analysis and the obtained thermogravimetric data were subjected to thermodynamic and kinetic analysis to evaluate the entropy/enthalpy changes, Gibb's free energy, kinetic activation energy, and half-life period at each degradation stage. The results revealed that the chemical treatments improved the fiber's physico-chemical and thermo-mechanical properties. The oxalic acid treatment improved the cellulose weight % up to 29.16%, and the NaOH treatment decreased the CASF diameter up to 16.9%. The thermal stability of oxalic acid-treated CASF (OT-CASF) was 358.62 degrees C, and it exhibited the highest activation energy of 49.01 x 10(3) Jmol(-1) at the final degradation phase (P-4) which was 10.99% higher than raw CASF. The half-life period of the OT-CASF was increased from 3.808 min(-1) to 5.251 min(-1) at the cellulose degradation phase (P-3) revealing better thermal stability when compared to the raw and NaOH-treated CASF. The scanning microscopic images and the surface plots revealed an enhancement in the surface roughness and wettability for the OT-CASF. From the results, it was identified that Capsicum Annum Stem fiber (CASF) is a potential and sustainable new resource of raw material. The oxalic acid treatment enhanced the physical, chemical, thermal and mechanical properties of the CASF when compared to the NaOH treatment. The characterization results confirmed that the CASF is a suitable material for reinforcing polymer matrices and can be used in automotive applications as interior panels, and dashboards.