Moisture induced plasticization

Wollny M., and Peleg M. (1994). A model of moisture-induced plasticization of crunchy snacks based on Fermi s distribution function. J. Sci. FoodAgri., 64,467-473. 

The nature of the interaction between water and the polymers is important because absorbed water can adversely affect thermal, electrical and mechanical properties of the polymer. Moisture absorption increases the dielectric constant, (5.6) and dielectric loss, (7) and has been related to device reliability problems. (8) Water-induced plasticization causes hygroscopic expansion, lowering of Tg, and degradation of mechanical properties. (9)... 

The structural properties of a synthetic polymer can often be modified by the service conditions to which it becomes exposed, an example being interaction with atmospheric moisture. Water induced plasticization is a common occurrence, yet depending upon the chemistry and morphology of the polymer encountered, the nature of the interaction process may take widely different routes. Some degree of specificity must be assumed in discussions relating the state of sorbed water in different polymeric systems. 

One acceleration model that is applied is the modified Eyring model, which was developed for moisture-induced corrosion in plastic packages ... 

JEDEC JESD 22-A112 Test Method A112, Moisture-Induced Stress Sensitivity for Plastic Surface Mount Devices... 

Moisture induced failures have been the most persistent, and thus the most intensively studied, of all the reliability hazards of plastic encap-... 

A 1000 h 85°C/85% RH lifetest has become the standard industry method of assessing the moisture resistance of plastic encapsulated components. Although the test conditions were initially chosen somewhat arbitrarily, they can be justified by using empirical equations derived from studies which have shown that the rate of moisture induced degradation is a function of both relative humidity and temperature. All but one of these equations are derived by fitting curves to... 

Composite decking materials are manufactured under heat and pressure to encase the cellulosic fiber in the plastic, resulting in a product with high resistance to weathering, moisture, insect infestation, and decay. In reality, the encasement is never complete, which leaves room for water absorption, thermal- and UV-induced oxidation with oxygen from the air, and microbial contamination. 

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