Control of Moisture and Volatile Organic Compounds by Sorbent-Loaded Composites
Abstract
The integrity, performance and service time of certain automotive subsystems is adversely affected by moisture ingress into contained environments. Corrosion of air conditioning (AC) system components caused by moisture initially present in the refrigerant and moisture permeated through the seals during the AC unit service life is one example. Another one is water vapor condensation in optical components used for night and rear vision systems as well as optical proximity sensors, often causing their malfunction in changing environmental temperature and humidity conditions. Desiccating multiforms® attached to a condenser coil have long been used in automotive AC units to absorb the residual moisture and the moisture permeating from outside. The new direction in AC moisture control is the use of sorbent-loaded polymer composites in AC structural parts that eliminate the need for individual desiccating multiforms®, their assembly operation as well as the associated noise from the assembly. Desiccating composite enclosures and seal materials are simultaneously targeted for improving performance of optical components. Volatile organic compound (VOC) emissions from fuel tanks and lines into atmosphere can also be reduced by using VOC absorbing composite materials as reactive barriers to permeation in fuel tank and supply line design.
The performance of sorbent-loaded composites is evaluated from the standpoint of two distinct design targets: removal the target vapor from the contained environment and reducing the rate of ingress from the external environment. The concepts of the layer reactivity, the adsorptive capacity, and the sorption rate are applied to the homogeneously reactive media and the sorbent-loaded polymer composites. The corresponding differences in performance and design requirements are discussed.
