How Moisture Content Affects Polymer Processing

Water absorption in polymers directly impacts both product quality and production efficiency — when exposed to ambient humidity, hygroscopic resins including PA, PC, and PET — can absorb water molecules deep within their structure. The water isn’t superficial — it becomes embedded in the polymer backbone, leading to serious complications during melting and extrusion.

To achieve proper mixing, polymer pellets are subjected to elevated temperatures for fusion with fillers, stabilizers, and colorants}. When water remains trapped in the resin — it turns into pressurized vapor due to thermal expansion. The vaporization induces internal porosity and micro-bubbles, manifesting as surface blemishes, poor shine, or inconsistent texture. These imperfections compromise aesthetics, and erode key physical properties, lowering fracture toughness and durability.

Water exposure leads to irreversible chemical reactions in certain polymers. Hydrolytic cleavage breaks polymer bonds in ester and amide groups, a degradation pathway that fragments long-chain molecules. The molecular weight distribution shifts downward, and critically affects processability and extrusion stability. Lower molecular weight means the polymer becomes more brittle, making it prone to cracking and premature failure, especially detrimental in automotive, medical, or aerospace components.

Proper pre-drying is an essential step in quality control. Most hygroscopic resins must be dried at temperatures between 80°C and 120°C, for durations of 2 to 8 hours depending on material type and humidity levels. Advanced lines employ closed-loop desiccant dryers or thermal dehumidifiers, achieving the industry-standard threshold for engineering plastics.

Moisture regain can occur rapidly if storage is inadequate. Therefore, strict handling and storage protocols are essential. Operators must utilize airtight storage, dry-air purged feed systems, or vacuum-sealed bins. Humidity levels in the processing zone require constant surveillance, Material must be fed into the extruder within 30–60 minutes of drying.

In essence, تولید کننده گرانول بازیافتی moisture content is not a peripheral concern in polymer compounding. Ignoring this factor results in inconsistent batches, rejected parts, and production delays. It can also trigger customer complaints, warranty claims, and brand damage. By implementing rigorous drying, sealed handling, and environmental monitoring, manufacturers can ensure consistent, high-quality output.