1. Physical and Chemical Processes (Initiation Stage)

• Light (UV radiation): Breaks polymer chains, generating free radicals → the material becomes brittle.

  
  

• Temperature: Elevated temperatures accelerate molecular motion and chain scission, while low temperatures slow degradation.

  
  

• Moisture (Water): Penetrates the material and attacks ester bonds, triggering hydrolysis reactions that fragment the film into smaller pieces.

These processes act as a “pretreatment,” converting intact macromolecules into fragments that are more accessible for further breakdown.

2. Microbial Action (Core Stage)

• Soil microorganisms such as bacteria and fungi secrete enzymes (e.g., esterases) that degrade oligomers formed during the initial stage.

  
  

• For polyester-based materials (PBAT, PLA, PBS, etc.), microorganisms metabolize the hydrolysis products into carbon dioxide (or methane), water, and inorganic salts.

  
  

• For starch- or cellulose-based films, microorganisms can directly utilize them as a nutrient source.

  
  

 This step achieves complete degradation, avoiding the generation of persistent microplastics that result from conventional polyethylene films.

3. Synergistic Process and Controllability

• The overall degradation process = physical cracking → chemical chain scission → microbial biodegradation, operating in sequence and in synergy.

  
  

• Environmental conditions significantly affect the rate:

• High temperature and humidity → accelerated degradation

• Arid or saline–alkali soils → slower degradation

Degradation rate can be tailored through material design:




Formulation adjustment (e.g., PBAT/PLA blends to balance degradation rate)




Additives (UV stabilizers to delay photodegradation)

Film thickness design (to regulate water penetration)

For example, specialized potato mulch films remain intact during the tuber bulking stage but naturally degrade around harvest time, achieving “on-demand degradation.”

 Conclusion

The degradation of biodegradable mulch films is not a single reaction but rather the synergistic result of physical, chemical, and biological processes. Its essence lies in the benign interaction between material structure and the natural environment, ultimately returning to the natural cycle without leaving pollution.
This mechanism is the fundamental reason why biodegradable mulch films can replace traditional polyethylene films and effectively address “white pollution.”