Study On The Compatibility of PLA TPU Composites and Their Flame Retardancy

Polylactic acid (PLA) is a biodegradable polymer material with high tensile strength, but its products have poor toughness, easy fracture and poor crystallization performance. Polyurethane elastomer (TPU) has the characteristics of high toughness and low temperature resistance, and its lack of toughness can be compensated by blending with PLA. However, due to the difference in polarity, a compatibilizer needs to be added to effectively improve the toughness of PLA.
In this paper, PP-g-MAH is used as a compatibilizer to study the effect on the compatibility of PLA /TPU (80%/20%) blends.

Figure 1 shows the SEM photographs of cross-sections of composites with different contents of PP-g-MAH. From Fig. 1 (a) and (c), it can be seen that with the addition of 1% PP-g-MAH, PLA and TPU lack the force and form an obvious aggregation distribution of large size, which increases the magnification, and many gaps and cavities can be seen between the two components; Fig. 2 (b) shows that with the addition of 3% PP-g-MAH, the fracture surface of the composite becomes rough and wrinkles appear, which shows a typical The fracture surface of the composite became rough and wrinkled after the addition of 3% PP-g-MAH, which showed the typical toughness fracture, indicating that the compatibility was improved.

Figure 2 shows the DSC curves of the composites. The cold crystallization peak and melt peak of PLA correspond to the cold crystallization peak and melt peak near 120°C and 165°C, respectively. The shape and area of the peaks varied with the compatibilizer content. 3% PP-g-MAH content resulted in sharp peaks, which was due to the strong interaction between PLA and TPU under the action of compatibilizer. It indicates that the best compatibility between PLA and TPU in the presence of 3% PP-g-MAH, and the crystallinity of PLA is improved.

With the addition of 15% melamine in the presence of 3% PP-g-MAH, the composite material can reach the flame retardant requirement at 830°C with certain flame-retardant effect.