High surface area carbon black (BP-2000) as a reinforcing agent for poly[(−)-lactide]

The brittle nature and low-heat distortion resistance of a promising biorenewable thermoplastics, poly((−)-lactide) (PLA), motivate the investigation of strengthening additives that can address these deficiencies. In our work, a high surface area carbon black (BP-2000) as well as biobased carbon blacks (hydrochars) were examined as reinforcement agents for PLA. When 1–5 wt % BP-2000 was added to PLA, the crystallization of PLA was accelerated, resulting in higher crystallinity, tensile strength, and heat resistance. A thermal creep experiment revealed that the composites exhibited no significant deformation after 30 min with 2 N of uniaxial tensile force at 80 °C (above the T_g), whereas neat PLA (with similar thermal history) elongated to 79% after 5 min under the same conditions. PLA–hydrochar composites demonstrated similar brittle behavior to neat PLA. Despite the promising nucleating ability of hydrochars, they displayed low interfacial adhesion with PLA because of their low surface area, resulting in poor energy transfer on stretching.