Interfacial interactions and microstructural evolution in powder-processed PLA/Date kernel biocomposites

Highly biofilled polylactic acid (PLA) composites reinforced with 50 vol% date kernel (DK) powder were successfully consolidated via a powder-based processing route (180°C, 10 MPa). Despite the high filler loading, dense green composites with a low porosity level of 1.1% and relatively uniform particle distribution were achieved. SEM and AFM observations revealed good interfacial continuity and increased surface roughness, with Ra rising from 171 nm for neat PLA to 378.8 nm for the composite. FTIR and Raman spectroscopies provided evidence of physicochemical interfacial interactions between PLA and DK, with spectral changes consistent with possible hydrogen-bonding-type interactions between PLA carbonyl groups and hydroxyl-containing functionalities of DK. XRD and DSC analyses showed that DK altered PLA crystallization by acting as a nucleating agent, increasing crystallinity while forming more imperfect crystals and slightly lowering the melting temperature (from 177.2°C to 174.5°C). While TGA/DTG indicated an earlier thermal degradation onset decreased from 315°C to 286°C, the composite maintained thermal stability above the processing temperature. Overall, the proposed powder-based route enables the fabrication of highly biofilled PLA composites with apparent interfacial continuity and relevant physicochemical features, which provide a preliminary basis for future processing and mechanical validation studies.