This study presents the development of polylactide (PLA)-based biocomposites reinforced with 5, 10, and 15 wt.% polymethylsilsesquioxane (PMSQ) microparticles. The materials were prepared by melt blending followed by injection molding to evaluate the effect of PMSQ content on the morphological, thermal, mechanical, thermomechanical, rheological, and thermal conductivity properties of polylactic acid (PLA). Scanning electron microscopy (SEM) revealed a relatively uniform dispersion of PMSQ particles, especially at low filler content (up to 5 wt.%). Differential scanning calorimetry (DSC) showed that PMSQ incorporation did not significantly affect the melting temperature of PLA, while the cold crystallization temperature decreased by 14 °C combined with a higher crystallinity level. Thermogravimetric analysis (TGA) showed a slight improvement in thermal stability, with higher residual mass as PMSQ content increased. Mechanical tests showed a 7.4% reduction in Young's modulus and a 20% loss of tensile strength for the biocomposite containing 15 wt.% PMSQ due to limited interfacial stress transfer and particle agglomeration. However, dynamic mechanical analysis showed that low PMSQ concentration (5 wt.%) increased the storage modulus by 15% at 35 °C and slightly increased the glass transition temperature by up to 2 °C. Rheological analyses revealed higher storage modulus, loss modulus, and complex viscosity with increasing PMSQ content. Additionally, the presence of PMSQ enhanced the thermal conductivity of PLA by up to 23% at 75 °C. Overall, PLA/PMSQ biocomposites, especially at low PMSQ content, showed improved thermomechanical stability and thermal conductivity, suggesting their potential use in thermoforming applications.

Polylactic acid (PLA) is a promising bio-based polymer, but its limited thermomechanical stability and low thermal conductivity restrict its use in thermoforming. This study aimed to investigate the influence of polymethylsilsesquioxane (PMSQ) microparticles (5–15 wt.%) on the thermal, mechanical, thermomechanical, rheological, and heat-transfer properties of PLA biocomposites prepared by melt blending and injection molding, with a focus on the thermomechanical properties and thermal conductivity. The results showed that PMSQ acted as an effective nucleating agent, reducing the cold crystallization temperature by up to 14 °C and increasing the crystallinity of PLA, while having little influence on its melting and glass transition temperatures. At 5 wt.% PMSQ, the storage modulus increased by 15% at 35 °C and the thermal conductivity improved by up to 23% at 75 °C, indicating enhanced thermomechanical stability and heat-transfer efficiency. In contrast, tensile strength, yield strength, and impact resistance decreased at higher PMSQ contents (10–15 wt.%), mainly due to particle agglomeration and the formation of defects observed by SEM. Rheological analyses further showed that PMSQ slightly modified the viscoelastic relaxation behavior of PLA. Among the investigated formulations, PLA containing 5 wt.% PMSQ provided the most favorable balance between thermal conductivity, thermomechanical and thermal stability, and mechanical performance. A limitation of the study is that the individual contribution of the coupling agent was not evaluated separately. Overall, the results demonstrate that low PMSQ contents represent an effective strategy for improving the thermal and thermomechanical performance of PLA and highlight the potential of PLA/PMSQ biocomposites for infrared-assisted thermoforming applications.