Issue 78

N. Nayak et alii, Fracture and Structural Integrity, 78 (2026) 378-392; DOI: 10.3221/IGF-ESIS.78.22

Alkali treatment was carried out under ambient laboratory conditions, and no external heating was applied during the 72 h soaking period. FTIR, XRD and chemical-composition analyses were not included in the present work; therefore, the treatment effect was assessed through mechanical-property changes and SEM-based fracture observations.

Sisal Fiber Preparation

Alkali Treatment

Drying/Storage

Raw Materials

Compression Moulding

Melt Blending with Propylene

Mechanical Testing

Specimen Cutting

Dielectric Testing

Response Surface Methodology Optimization

SEM Analysis

Figure 1: Experimental methodology adopted in the present investigation

Sisal fibre received Powder, 10 mm and 20 mm fibre forms selected for treatment ↓ Alkali treatment Fibres soaked in 10% NaOH solution for 72 h under ambient laboratory conditions ↓ Washing and neutralization Repeated rinsing with distilled water to remove residual alkali from fibre surfaces ↓ Drying Sun drying for one week to reduce residual moisture before fabrication ↓ Storage before fabrication Treated and untreated fibres stored separately in sealed packs with silica gel crystals Figure 2: Fibre surface treatment procedure adopted for sisal fibre modification

Composite fabrication Sisal fibre reinforced polypropylene composites were fabricated by melt blending followed by compression moulding. The required quantities of polypropylene and sisal fibre for each composition were calculated for a 150 × 150 × 3 mm plate, with approximately 20% additional material prepared to avoid shortage during processing. Compression-moulding grade polypropylene was used because it is lightweight, thermally stable, recyclable, chemically resistant and suitable for semi-structural and electrical-insulation applications. After melting the Brabender Plastograph, the prepreg was transferred immediately to the preheated compression mould to minimize temperature loss and avoid premature cooling before moulding. The constituents were blended using a Brabender Plastograph EC Plus machine equipped with a 3.8 kW motor and twin screws capable of developing 200 Nm torque. During blending, the screws were operated at 25 rpm and the chamber temperature was maintained at 150°C to melt the polypropylene and promote uniform fibre dispersion. The resulting prepreg was transferred to a preheated compression mould with a 150 × 150 mm cross-section. Compression moulding

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