PLA, a biodegradable plastic made from renewable resources, contains ester bonds in its molecular structure, making it susceptible to performance degradation due to environmental factors. Therefore, proper storage is crucial for ensuring its quality stability and performance. The main risks to PLA during storage include hygroscopic hydrolysis, thermal degradation, and oxidative aging. Standardized measures need to be established for environmental control, packaging protection, stacking management, and shelf-life monitoring.
First, the temperature and humidity of the storage environment should be strictly controlled. PLA is sensitive to moisture; even at room temperature, slow hydrolysis will occur under humid conditions, leading to a decrease in molecular weight, weakened mechanical properties, and embrittlement or surface defects in the product. The ideal storage temperature should be maintained between 15℃ and 25℃, with a relative humidity not exceeding 40%. During hot and humid seasons, ventilation should be increased or dehumidification equipment used to prevent environmental moisture from penetrating the material. Opened but unused PLA resin should be sealed as soon as possible and returned to a dry environment to avoid secondary moisture absorption.
Secondly, prolonged exposure to heat and light should be avoided. Although the thermal degradation initiation temperature of PLA is higher than the conventional processing temperature, continuous exposure to environments above 60°C or direct sunlight may cause molecular chain breakage and oxidation, leading to discoloration, odor release, and performance degradation. Therefore, storage locations should be cool, dark spaces, away from heat sources and direct sunlight; ideally, shaded or semi-enclosed storage facilities should be used.
Regarding packaging and stacking, PLA resin is typically sealed in moisture-proof inner film bags or aluminum foil composite bags, with an outer layer of moisture-proof paper or plastic drums to prevent moisture penetration during transportation and storage. When stacking, pallets or shelves should be kept dry and clean, avoiding direct contact with the ground. Stacking height should be moderate to prevent deformation of the bottom layer due to pressure or obstruction of airflow. Different batches and grades of PLA should be stored separately and clearly labeled for traceability and first-in, first-out (FIFO) management.
A regular inspection and quality testing system should be established during storage. Sampling and testing of moisture content, melt index, and mechanical properties can help detect potential signs of deterioration in a timely manner. For PLA stored for extended periods (over six months), pre-drying is recommended before use to remove any trace amounts of moisture that may have been absorbed, ensuring processing stability.
Furthermore, careful management of PLA's shelf life is crucial. While PLA can be stored for one to two years without significant degradation under suitable conditions, its molecular weight distribution may change over time, affecting the consistency and reliability of finished products. Therefore, the production date and recommended usage period should be clearly marked on packaging or in the warehousing system, prioritizing the use of earlier batches.
In summary, the key to successful PLA storage lies in moisture protection, temperature control, light avoidance, and isolation from contamination. Combined with proper packaging, stacking, and shelf-life management, this effectively maintains the integrity of its molecular structure and the stability of its processing properties, allowing it to fully realize its mechanical strength, transparency, and biodegradability advantages in subsequent product manufacturing.