Polylactide melting temperatures

The optically pure polylactides L-PLA (or PLLA) and D-PLA (or PDLA) are semicrystalline polymers with glass transition and melting temperatures of about 60 °C and 180 °C, respectively. In contrast, DL-PLA (or PDLLA) is an amorphous polymer that consists of racemic lactate units and is crystalline only when the D and L unit sequence is completely alternating such a polymer is termed poly (meso-lactide) [44]. The blending of PLAs can result in new materials that present with unexpected synergisms, such as those observed in the equimolar blends between the optically pure polylactides, PLLA and PDLA. 

It is an aliphatic polyester derived from renewable resources, such as com starch, tapioca roots, chips or starch, or sugarcane. Polylactic acid or polylactide (PLA) can withstand temperatures up to 110 °C [69]. PLA is soluble in chlorinated solvents, hot benzene, tetrahydrofuran, and dioxane [70]. It can be processed like other thermoplastics into fiber (for example, using conventional melt spinning processes) and film. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist ... 

CaCOj-polylactide nanocomposites can also be prepared via melt compounding technique using twin screw extruder [64]. The temperature of the mixing zone varied from 150°C at entry to 190° at exit at a mixing speed of 150 rpm. These samples were then injection molded to the desired shape. 

L-PL is a ciy stalline, biodegradable polymer having a melting point (T ,) of approximately 175°C and a glass transition temperature (Tg) of approximately 65° C (Schindler et al., 1977). Fisher, et al. (1973) has reported a calculated value for the heat of fusion of 100% crystalline PL as 93.7 J/gram, while the heat of fusion for commercial products has been reported as low as 30 J/gram (PURAC 1996). The empirical formula of the polylactides is (C3H402)r,. 

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