Due to the long international ocean shipping cycle, sea surface temperature, and wide geographical span, there will be significant differences in the external environment of containers, which directly affect the internal environment and humidity of the containers, forming 'container fog and rain', and moisture will continuously harm the cargo.
Impact of moisture in cargo
Condensation occurs in both dry and wet containerized cargo, but it is more pronounced in wet cargo than in dry cargo.
Relationship between container and outside air
When the temperature drops, the pressure inside the container also drops, and the outside humid air enters the container (i.e., inhalation); when the temperature rises, the opposite occurs (i.e., exhalation).
Desiccant absorbing moisture from the air
Desiccant Can effectively control condensation and prevent moisture from penetrating goods. As shown in the series of charts above, we must place an appropriate amount of desiccant according to the container specifications, the characteristics of the transported goods, the transit time, and the span of locations. While absorbing moisture inside the container, it must also be able to adequately absorb the continuously entering external moisture (moisture from the sea surface). With variations in transport across different regions, it can fully absorb moisture when the dew point rises, but when sailing to areas with lower external temperatures and declining relative humidity, the desiccant should not re-exude water vapor.
During land transportation, although the overall external humidity is lower than that on the sea, differences in external atmospheric temperature and humidity compared to the initial packaging environment can also cause changes in the entire internal packaging environment.
Generally, there are also certain differences in the placement position and the amount of desiccant used. Typically, different amounts of desiccant are placed in two parts, at the container opening and within the cargo, to achieve comprehensive protection of the cargo's quality.
Of course, choosing appropriate desiccant packaging material is as important as choosing the desiccant itself. Firstly, it must ensure that the desiccant can perform its normal moisture absorption, meaning the material must have good water vapor transmission rate and no back-permeability. In addition, the material itself must be dust-free and pollution-free, and secondly, it must prevent internal desiccant leakage and contamination due to packaging material damage.
Therefore, placing desiccants as an economical and convenient moisture-proof measure has gradually become a common practice and necessary protective measure in the cargo transportation industry.
Hengyuan Polymer, as a professional Desiccant company, our responsibility is to determine the accurate and appropriate desiccant dosage based on different shipping environments and packaging specifications. 。
