The information provided regarding the shelf life of various plastic products and raw materials is indeed valuable for those in the plastics industry, including processors and suppliers. It highlights the importance of understanding the degradation processes that can occur in plastics over time, particularly when exposed to certain environmental conditions and additives. Here's an expanded version of the information, along with some additional comments and suggestions for readers:
**Polymer Degradation and Shelf Life Considerations**
Mild chemical reactions can occur within polymer chains over time, especially when catalysts or environmental conditions such as sunlight, moisture, and certain compounds from colorants, additives, or processing aids are present. These reactions can lead to changes in the physical and chemical properties of plastics, affecting their performance and longevity.
**Shelf Life of Plastic Products Under Standard Storage Conditions**
The shelf life of plastic products is typically determined under standard storage conditions, which are a temperature range of 22-27°C and a relative humidity (RH) of about 50%. The following shelf lives are provided for various plastic products:
1. **PET Preforms** - These should be used within 6 months from the date of manufacturing to ensure optimal quality. Beyond this period, the preforms may become more susceptible to crystallization and changes in physical properties.
2. **LDPE Shrink Film** - This product has a shelf life of 12 months from the date of manufacturing. After this time, the film may lose its shrinkability and become more brittle.
3. **Cling Film** - Similar to LDPE shrink film, cling film should be used within 12 months of manufacturing to maintain its clinginess and flexibility.
4. **PP Pails** - Polypropylene pails are durable but should still be used within 12 months of manufacturing to prevent potential changes in strength and flexibility.
5. **CSD Closures** - These closures for carbonated soft drink bottles should be used within 6 months from the date of manufacturing to ensure they maintain their sealing properties.
**Impact of External Factors on Plastic Product Quality**
It's important to note that if plastic products are exposed to external factors not accounted for in standard storage conditions, such as dust, sunlight, rain, or excessive moisture, the quality cannot be guaranteed. These factors can accelerate degradation and reduce the effective shelf life of the products.
**Shelf Life of Raw Materials**
The shelf life of raw materials can vary significantly depending on several limiting factors:
- **PET** - Typically has a shelf life of 1 year from the date of manufacturing, after which it may become more difficult to process and may exhibit changes in properties.
- **PP (Polypropylene)** - Can have a shelf life of up to 2 years, due to its inherent stability, but this can be influenced by the presence of additives and processing conditions.
**Comments and Suggestions for Readers**
- Always refer to the manufacturer's data sheets and recommendations for specific storage and shelf life information.
- Implement a first-in, first-out (FIFO) inventory system to ensure that older stock is used before newer stock.
- Consider the potential impact of storage conditions on product quality and adjust them as necessary to extend shelf life.
- Regularly inspect stored materials for signs of degradation, such as discoloration, odors, or changes in texture.
- If you notice any changes in the material properties, consult with the material supplier for guidance on whether the product is still suitable for use.
- For processors, it's crucial to communicate with suppliers about the shelf life of raw materials to manage inventory effectively and avoid quality issues.
By taking these factors into account, plastics processors and raw material suppliers can maintain the integrity of their products and ensure that they meet the quality standards expected by their customers.
