What are the challenges in achieving airtight seals on WPC outdoor trash can lids?

Achieving airtight seals on Wood-Plastic Composite (WPC) outdoor trash can lids presents several significant challenges. The primary issue stems from WPC's inherent material properties - it expands and contracts with temperature fluctuations, creating gaps that compromise seal integrity. Unlike solid plastics, WPC's composite nature makes it difficult to create perfectly uniform edges that mate seamlessly with the container base. Weather conditions exacerbate these problems, as rain can cause swelling while sun exposure leads to material shrinkage. The manufacturing process itself poses obstacles, as injection molding WPC can result in slight warping or uneven surfaces that prevent consistent contact points. Furthermore, the need for practical usability requires lid hinges and handles, which create additional potential leak points that are challenging to seal effectively. These combined factors make perfect airtightness difficult to achieve while maintaining the material's structural benefits and cost-effectiveness for outdoor applications.