Chemical Process
Self-accelerating chemical decomposition of polymer backbones driven by the reaction products of the breakdown itself determines the lifetime of bio-based packaging materials. In biodegradable films such as polylactic acid, autocatalytic cleavage occurs when ester bonds undergo hydrolysis, releasing carboxylic acid end groups that lower the local pH. This acidic environment then increases the rate of further ester bond hydrolysis.
The process converts long, insoluble polymer chains into short, water-soluble oligomers. In co-extruded barrier layers, this degradation path must be suppressed during processing to avoid loss of gas barrier properties.
Degradation Rate
Mechanical integrity of packaging films decreases rapidly once the self-sustaining reaction is initiated. As the concentration of acidic degradation products increases within the bulk material, the rate of cleavage climbs exponentially. This causes a sudden loss of tensile strength and barrier properties, often before any visible signs of surface erosion appear.
Rapid structural failure represents the typical outcome of this internal accumulation of catalysts.
Environmental Boundary
Susceptibility to this self-catalyzing reaction is highly dependent on ambient humidity and storage temperature. Below twenty degrees Celsius, the reaction is slow enough to ensure a stable shelf life for dry packaged goods. The reaction speeds up under humid composting conditions.
Once moisture levels exceed fifty percent, the process becomes irreversible.
