Plasticization of poly(L-lactide) with poly(propylene glycol)

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials

Background:

• Poly(L-lactide) (PLA) is a biodegradable polymer with limitations in flexibility and processability.
• Traditional plasticizers like Poly(ethylene glycol) (PEG) are known for PLA, but new alternatives are sought.
• Poly(propylene glycol) (PPG) offers potential as a miscible, non-crystallizing plasticizer for PLA.

Purpose of the Study:

• To investigate the efficacy of Poly(propylene glycol) (PPG) as a novel plasticizer for Poly(L-lactide) (PLA).
• To compare the plasticizing effects of PPG with different molecular weights against Poly(ethylene glycol) (PEG).
• To evaluate the impact of PPG on the thermal and tensile properties of PLA.

Main Methods:

• Preparation of PLA blends with varying weight percentages (5-12.5 wt%) of PPG (Mw 425 and 1000 g/mol) and PEG (Mw 600 g/mol).
• Analysis of thermal properties, including glass transition temperature (Tg).
• Tensile testing to assess mechanical properties such as yield stress and elongation at break.

Main Results:

• PPG significantly lowered the glass transition temperature of PLA.
• Both PPGs increased PLA's crystallizability, though less effectively than PEG.
• Plasticizers enhanced PLA's plastic deformation, reducing yield stress and increasing elongation at break, with effects more pronounced at higher PPG content and lower molecular weight.
• Phase separation was observed only in PLA with 12.5 wt% of higher molecular weight PPG.
• Deformed samples showed crazing at low plasticizer content and crystallization at higher content.

Conclusions:

• Poly(propylene glycol) is a viable plasticizer for Poly(L-lactide), improving its mechanical properties.
• The molecular weight of PPG influences its effectiveness as a plasticizer for PLA.
• PPG offers a promising alternative for modifying PLA properties for various applications.