4

Polymer Class

This designation distinguishes low density polyethylene from high density alternatives by evaluating molecular branching and density ranges between 0.915 and 0.925 grams per cubic centimetre. Short chain and long chain branches prevent the polymer chains from packing closely, which results in a highly flexible material with high impact strength. Sourcing teams rely on the number 4 to secure material for applications requiring high elongation such as squeeze bottles and squeeze films.

Procuring regrind with this classification requires careful validation to avoid blending with high density grades that reduce crack resistance.

Thermal Parameter

Extrusion and injection moulding machines process this material using lower temperature profiles than those required for linear low density variations. Because the branched structure lowers the melting temperature, less heating energy is required during the melt phase. This characteristic reduces cycle times and preserves polymer stability during prolonged production runs.

Excessive regrind ratios can degrade the material and cause flash defects or visual blemishes on the finished part surface.

Commercial Value

Market dynamics for recycled materials of this specific category remain highly dependent on collection efficiency and sorting accuracy. High volume post consumer scrap streams yield clean reprocessed pellets that compete directly with virgin resins in non food packaging. Maintaining a stable melt flow index across successive batches remains the primary operational challenge when using these recycled pellets.

Consistent testing of incoming lots protects the moulder from sudden viscosity shifts that lead to short shots or part warpage.