Astlett Rubber Inc.: Customer Help Sheets

Moisture and Rubber
Astlett Customer Help Sheet

Trapped Moisture Most problems with moisture on natural rubber can be corrected. External moisture may become trapped under the polyethylene wrapper and, over time, the rubber becomes bleached and some of it may decompose (become mouldy).

Moisture can be trapped on rubber surfaces under the polyethylene wrappers by condensation or dripping of condensation or rain on the bales/crates, anytime prior to discovery.
The presence of moisture turns rubber white over time (this is called bleaching). Removal of moisture (drying) returns the rubber to its dry condition, with no harm done! Bleaching is reversible and not usually considered harmful. The heat of processing will also drive off excess moisture. If the moisture is not removed, bleached rubber is eventually denatured and then decomposes (mould or rot).
Bleaching is a surface phenomena. Longer exposure and/or greater moisture result in greater penetration. Moisture contamination could and should be detected on receipt at factory. This will make it possible to ameliorate or completely avoid any damage.

Suggested Procedures by Receivers

Simply by cutting windows (4" V shaped cuts) in the polyethylene wrappers in several places on each unit, a receiver can check for the possibility of any moisture, bleaching or mould.
If moisture is discovered, measures should be taken to promote drying by cutting numerous windows. This lets any trapped moisture escape.
If bleach is discovered, more vigorous drying efforts should be undertaken. Typically, removing the outer liner, windowing the affected bales, separating or stripping the bales to expose to airflow and using a fan or heater to speed drying of the rubber is suggested. The rubber usually returns to its original processed colour. The quality is not affected!
If mould is discovered, the affected surface can be removed by trimming. Bleached or mouldy bales or pieces can be used for lesser applications.