PLA Nonwoven Fabric

PLA natural degradation generally undergoes two stages: initial hydrolysis decomposition followed by microbial degradation. When PLA material is immersed in aqueous media, water absorption of the material occurs first. Aqueous media infiltrates the polymer matrix, causing relaxation of polymer molecular chains, initial hydrolysis of ester bonds, molecular weight reduction, gradually degrading into oligomers. Subsequently, microorganisms enter the tissue, decomposing it into CO2 and water. Macroscopically, the overall structure of the material is disrupted, volume decreases, gradually becoming fragments.

Favorable conditions for compost degradation include:

1. Environmental humidity reaching 90%;
2. Environmental temperature exceeding 60 degrees Celsius;
3. The degradation time under compost conditions is usually 45 to 60 days.

Hydrolysis conditions: Both acid and alkali can catalyze PLA hydrolysis. The degradation rate is higher under alkaline conditions compared to acidic conditions. Carboxylic acid products generated during hydrolysis interact with alkali, promoting the hydrolysis reaction in the forward direction. PLA can undergo self-hydrolysis in deionized water, producing acidic compounds containing carboxyl groups, thereby accelerating hydrolysis. The degradation rate at 80% relative humidity is over 3 times faster than at 20% relative humidity. The higher the environmental humidity, the higher the temperature, the faster the hydrolysis process, and the shorter the degradation time.

The figure above shows the degradation data of electrospun polylactic acid (PLA) fibers by my colleague, depicting both rapid biodegradation and degradation after 30 days of soil burial.

The degradation images of PLLA meltblown fabric in compost at a constant temperature of 58°C show signs of fiber breakage and surface erosion after 7 days. Similarly, PDLA and 1D3L samples exhibit similar behavior after day 11. By day 14, the extent of erosion becomes severe, with dense deposition of compost material appearing on the surface of all fiber pads. (PLLA and PDLA refer to left-handed and right-handed PLA, respectively).