Heat Resistant Research Of Biodegradable Polylactic Acid Materials

With people's growing concern about environmental protection, biodegradable materials have attracted considerable attention. Poly(lactic acid) (PLA) materiel has been utilized relatively widely because of its well biocompatible and biodegradable property. However, due to slow crystallization, low degree of crystallization and weakness of heat-resistance, PLA is also restricted range of industrial applications.In this paper, I research to improve the heat resistance of PLA materials and crystalline properties by adding the PLA materials, nucleating agents and to take heat treatment methods. By using isothermal crystallization tester, polarized optical microscopy (POM), X-ray diffraction (XRD), heat deflection temperature detector (HDT), differential scanning calorimeter (DSC), electron tensile tester and scanning electron micrograph (SEM), the samples were analyzed and characterized. Ultimately conclusions can be gotten the following:1. Poly(L-lactic) acid (PLLA) has the fastest crystallization rate by the addition of Poly(D-lactic) acid (PDLA) as nucleating agent at the crystallization temperature 120℃. PDLA and PLLA can combine to form stereocomplex Structure. By annealed, when the PDLA content reached 5% (mass fraction), crystallinity,heat resistance and mechanical properties of PLLA all increased.2. Compared PLLA materials mixed with three nucleating agents: PDLA, Talc and TMC-328, respectively, through annealing, the result indicated that PLLA mixed with PDLA had the highest degree of crystallization and best heat resistance in them, and the second was PLLA mixed with Talc, the last one was PLLA mixed with TMC. but The tensile strength of the descending order was Talc/PLLA system, TMC/PLLA system and PDLA/PLLA system.3. In composite nucleating agents system, the heat resistance and crystallinity of PDLA/Talc nucleating agent system were greater than that of PDLA/TMC composite nucleating agent system. Compared with a single nucleating agent, the heat deflection temperature and crystallinity of PDLA/Talc composite nucleating agent system decrease. Compared with same one, the degree of crystallinity of PDLA/TMC system is less than PDLA/PLLA system, larger than PLLA/TMC system, and heat deflection temperature or less.