Design and manufacture of degradable polymers: Biocomposites of micro-lamellar talc and poly(lactic acid)

Over the last decade, biopolymers have seen a sharp increase in their market share as an alternative to conventional oil-based plastic materials. Among them, degradable biopolymers are rarely employed, especially in the field of durable end-goods, because of their often limited chemical, mechanical and thermal behaviours. In contrast, stringent international regulations encourage the employment of low-impact materials in several manufacturing domains, with degradable polymers considered par excellence. In the present work, an innovative route to control the final properties of an extrusion-compounded, high-performance biocomposite composed of polylactic acid (PLA) reinforced with micro-lamellar talc is proposed. For this purpose, talc was first modified via surface reaction with organic (i.e., belonging to the class of polyisocyanates) or hybrid organic-inorganic (i.e., belonging to the class of organosilanes) compatibilizers, respectively. Custom-built formulations were then achieved by the dispersion of the pretreated micro-lamellar talc in commercial-grade PLA. The resulting compounds were analysed by differential scanning calorimetry (DSC) and attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. The experimental findings show that PLAs with different properties can be achieved as a result of chemical and physical interactions among the functional groups on the surface of the pretreated talc and the terminal groups of the PLA chains. These results are extremely promising for the achievement of innovative grades of PLAs suitable for melt processing and to ensure the greatly improved chemical inertness, thermal stability and mechanical strength of the resulting end-goods.