Let Down Ratio

process

The ratio of masterbatch concentrate to total polymer weight in a plastic formulation, typically expressed as a percentage or weight ratio for achieving desired additive levels.

In Simple Terms

Let down ratio tells you how much concentrated masterbatch to mix with virgin resin to get the right amount of additives like colorants or UV stabilizers. It's like a recipe ratio - if you have 20% color masterbatch, you need 5 parts masterbatch to 95 parts base resin.

Why It Matters

Proper let down ratios ensure consistent product quality, color matching, and additive performance while controlling costs. Incorrect ratios can lead to poor dispersion, color variations, inadequate UV protection, or processing issues that affect final part properties.

Technical Details

Let down ratios are calculated based on the active ingredient concentration in the masterbatch and target loading in the final product. For example, a 50% carbon black masterbatch used at 4% let down provides 2% carbon black in the final compound. Factors like carrier resin compatibility, processing temperature, and mixing efficiency affect optimal ratios.

Real-World Examples

Color masterbatch for injection molding

A 25% pigment masterbatch used at 4% let down ratio provides 1% pigment loading for consistent part coloration in HDPE containers

UV stabilizer masterbatch for outdoor applications

A 15% UV stabilizer masterbatch used at 6.7% let down delivers 1% active UV protection in polypropylene outdoor furniture components

Carbon black masterbatch for conductive applications

A 40% conductive carbon black masterbatch at 12.5% let down provides 5% carbon black loading for antistatic LDPE film applications