Modification of Poly(lactic acid) by the Plasticization for Application in the Packaging Industry

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Sustainable Packaging

Background:

• Plastic products are ubiquitous, leading to environmental concerns like microplastic pollution.
• Poly(lactic acid) (PLA) is a biodegradable polymer with potential for packaging but requires modification due to its rigidity.
• Developing green technologies and circular economy solutions is crucial for mitigating environmental impact.

Purpose of the Study:

• To investigate the modification of poly(lactic acid) (PLA) using various plasticizers for enhanced deformability in packaging applications.
• To evaluate the performance of different high- and low-molecular weight plasticizers on PLA's mechanical and thermal properties.
• To identify effective plasticizers for PLA that are suitable for food contact materials and offer improved properties over existing solutions.

Main Methods:

• Modification of PLA with various plasticizing substances, including ethoxylated lauryl alcohol, block copolymers, ethoxylated stearic acid, di-2-ethylhexyl adipate (ADO), di-2-ethylhexyl sebacate (SDO), and triethyl citrate.
• Characterization of modified PLA samples using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and mechanical testing (Young's modulus, elongation at break).
• Determination of melt flow rate (MFR) and molar mass distribution, alongside infrared (IR) spectroscopy analysis.

Main Results:

• All plasticizers lowered the glass transition temperature (Tg) of PLA.
• Di-2-ethylhexyl adipate (ADO) and di-2-ethylhexyl sebacate (SDO) demonstrated the most significant improvements, with ADO increasing elongation at break by ~21% and SDO by ~35%.
• ADO and SDO reduced Young's modulus by ~26% without causing polymer degradation, and IR spectra suggested interaction between plasticizers and PLA's ester carbonyl group.

Conclusions:

• Di-2-ethylhexyl adipate (ADO) and di-2-ethylhexyl sebacate (SDO) are effective plasticizers for poly(lactic acid), significantly enhancing its deformability.
• These plasticizers show great potential for use in PLA-based food packaging films, offering superior properties compared to triethyl citrate.
• The identified modifications contribute to developing more sustainable and adaptable bioplastics for the packaging industry.