What are the effects of polymer molecular weight distribution on the processability of WPC trash cans?

The molecular weight distribution (MWD) of the polymer matrix is a critical factor determining the processability and final properties of Wood-Plastic Composite (WPC) trash cans. A broad MWD typically enhances processability. The presence of higher molecular weight chains increases melt strength, which is crucial for maintaining the shape of the extruded profile during production, preventing sagging or deformation. Conversely, the lower molecular weight fractions act as internal lubricants, reducing melt viscosity and facilitating easier flow through extrusion dies. This combination allows for smoother processing at lower temperatures and pressures, improving manufacturing efficiency. However, an excessively broad MWD can lead to inconsistencies. Very low molecular weight polymers may migrate to the surface, causing blooming or affecting the composite's ability to hold pigments, leading to uneven color. A very high molecular weight fraction might require higher processing temperatures, potentially risking thermal degradation of the wood flour filler. Therefore, a carefully controlled, moderately broad MWD is often optimal for WPC trash cans, balancing easy processability with good mechanical strength, dimensional stability, and a high-quality surface finish.