Rain-Soaked Plastic Pellets: Will Their Performance Be Affected?

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What Happens When Plastic Pellets Get Wet?

After several consecutive days of rain, warehouses are still busy shipping and receiving goods, making moisture protection one of the biggest challenges for manufacturers and processors. Plastic raw materials stored outdoors can easily become soaked by rain if proper precautions are not taken. In mild cases, this may affect the material’s appearance; in more serious cases, it can lead to bubbles, silver streaks, and a high rate of defective products.

Today, we'll take an in-depth look at what really happens when plastic pellets get wet. By the end of this article, you'll know which materials can simply be air-dried, which must be thoroughly dried before processing, and which may be beyond recovery altogether.

Wet Plastic Pellets

Moisture Impact on Different Plastics

When plastic pellets are exposed to rain or moisture, their performance and processability may be affected. Whether they can still be used depends largely on the type of plastic and the extent of moisture absorption.

Some plastics such as PE and PP do not absorb water and can often be used after surface drying. However, engineering plastics like PA, ABS, PC, PET, and PBT absorb moisture internally and require proper drying before processing.

Non-Hygroscopic Plastics: PE, PP, PS, PVC — only surface moisture, easy to dry.
Hygroscopic Plastics: PA, ABS, PC, PET, PBT — absorb moisture internally and require desiccant drying.

Moisture can cause:

Silver streaks
Bubbles
Whitening
Flow marks
Splay marks

Recommended Drying Methods

Hot-Air Drying: Suitable for PP and PE materials (60–80°C for 2–4 hours).

Desiccant Drying: Required for PA, PC, ABS, PET, and PBT materials. A dew point of ≤ -20°C is recommended.

Moisture Exposure Guide

Plastic	Type	Drying Method	Potential Impact
PP / PE	Non-Hygroscopic	Hot Air Drying	Minimal, mainly affects appearance
ABS	Hygroscopic	Desiccant Drying	Silver streaks and bubbles
PC	Hygroscopic	Desiccant Drying	Reduced strength and optical quality
PA / PET / PBT	Highly Hygroscopic	Strict Desiccant Drying	Hydrolysis and irreversible degradation

Important Note

After drying, materials must be protected from ambient humidity and processed as soon as possible to prevent reabsorption of moisture.

Drying conditions should always follow the material supplier's datasheet recommendations. Engineering plastics such as PA, PET, and PBT require strict moisture control to ensure stable processing performance and final product quality.