The disintegration rate of polylactic acid (PLA) when reinforced with natural fibers compared to neat PLA under thermophilic conditions is a complex topic influenced by various factors, including the nature of the reinforcement, environmental conditions, and the inherent properties of PLA.

Disintegration of Neat PLA

Neat PLA is known to degrade rapidly under thermophilic conditions. Studies indicate that PLA can achieve approximately 90% weight loss within 90 days at temperatures around 60 °C due to hydrolytic degradation and microbial activity[1][3]. The degradation process begins with fragmentation, leading to significant changes in surface morphology, such as the formation of pores and cracks[1]. The hydrolytic degradation is enhanced by temperature and moisture levels, with higher temperatures accelerating the breakdown of polymer chains[1][2].

Impact of Natural Fiber Reinforcement

When natural fibers are incorporated into PLA, several outcomes can affect the disintegration rate as follows:

1. Hydrophilicity: Natural fibers can increase the hydrophilicity of the composite material, potentially enhancing water absorption and facilitating hydrolytic degradation[4]. This could lead to a faster disintegration rate compared to neat PLA under certain conditions.

2. Microbial Activity: The presence of natural fibers may provide additional surfaces for microbial colonization, which could enhance biodegradation processes. However, if the fibers are not biodegradable themselves, they might slow down the overall disintegration rate by forming a barrier that protects the PLA matrix[4].

3. Physical Properties: The mechanical properties of the composite can influence its degradation behavior. For instance, if the natural fibers significantly alter the crystallinity or thermal stability of PLA, this could either hinder or promote disintegration under thermophilic conditions[2][4].

4. Competing Degradation Mechanisms: The introduction of fibers may lead to competition between fiber degradation and PLA degradation. If fibers degrade slower than PLA, they could potentially slow down the overall disintegration process in a thermophilic environment[2].

Conclusion

In conclusion, while neat PLA disintegrates rapidly under thermophilic conditions due to its inherent properties, reinforcing it with natural fibers may lead to a lower disintegration rate depending on factors such as fiber composition, moisture content, and microbial activity. Further empirical studies are necessary to quantify these effects accurately and determine optimal formulations for specific applications.

Citations:

[1] https://www.thaiscience.info/journals/Article/ENRJ/10985451.pdf

[2] https://www.mdpi.com/2073-4360/13/18/3171

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769157/

[4] https://www.mdpi.com/2311-5629/7/2/42

[5] https://www.sciencedirect.com/science/article/pii/S2667010021000469

[6] https://www.sciencedirect.com/science/article/abs/pii/S0956053X22005177

[7] https://www.tandfonline.com/doi/full/10.1080/10889868.2024.2335908

[8] https://www.researchgate.net/publication/310589306_Degradation_of_Polylactic_acid_under_Simulated_Landfill_Conditions