Abstract: Using diethyl terephthalate and diethanol amine as raw materials, the polyhydroxy amide compound N,N,N',N'-tetrakis(2-hydroxyethyl) terephthalamide (THPP) obtained through organic synthesis as nucleating agent for polylactic acid (PLA), THPP and PLA were melt-extruded and pelletized in a twin-screw extruder to obtain modified PLA (PLA/THPP). Differential scanning calorimeter (DSC), X-ray diffractometer (XRD), polarizing microscope (POM), Vicat softening point tester and universal material testing machine were used to study the effect of adding different contents of THPP on the crystallization and mechanical properties of PLA. The results show that the addition of 0.7% THPP increases the crystallinity of PLA from 20.34% to 44.50%, 0.1% THPP increases the elongation at break of PLA by 3.1%, and 0.7% THPP increases its Vicat softening point after annealing from 123.0 ℃ to 161.3 ℃. In addition, the hot-stage polarized light microscope observes that the number of grains in the PLA sample added with THPP increases significantly and the grains are smaller within the same time of isothermal crystallization, and THPP exists in a homogeneous phase in PLA. However, too high content of THPP will increase the short-chain PLA, and the crystallinity will be poor.
Keywords: polylactic acid (PLA); nucleating agent; crystallization; polyhydroxy compound; mechanical properties
合肥工业大学学报自科版