Bio Based Grades Priced against the Composting Route They Need
Matching resin melt stability and wall thickness to regional waste facility residence times prevents unexpected landed part cost escalation.
Moisture Limit
Meaning
Technical specification identifies the maximum allowable threshold of water content within a resin batch that is considered safe for thermal processing. Different polymer types exhibit vastly different tolerances for humidity based on their chemical structure and sensitivity to hydrolysis. Staying below the moisture limit prevents irreversible molecular damage and ensures the final parts maintain their intended mechanical properties.
Threshold Variance
Polypropylene and polyethylene have very low affinity for water and can often be processed well above the limits set for engineering plastics. In contrast, polycarbonates and polyesters have a moisture limit as low as two hundred parts per million to avoid catastrophic failures. This difference forces moulders to use distinct drying equipment for technical materials versus commodity resins.
Economic Consequence
Exceeding the stated limit results in part rejection due to visual splay or failed structural tests. The cost of running dryers increases significantly as the target moisture limit tightens toward more stringent levels. Efficient manufacturers check these values at the hopper rather than trusting ambient delivery conditions.
Part Integrity
When materials stay under their specific moisture limit, the resin retains its datasheet viscosity and strength profiles. Parts molded from dry material resist stress cracking and show predictable shrinkage rates in the tool. This adherence allows designers to rely on the minimum properties stated by the supplier.