pps proceeding - Abstract Preview
pps proceeding
Symposium: S10 - Rheology and Rheometry
Oral Presentation
 
 

Humidity Controlled Rheology for the Study of Polymers

Führer Roman (1)*, Läuger Jörg (2), Arnold Gunther (2)

(1) Anton Paar GmbH, Anton Paar Str. 20, 8054 - Graz - Austria, (2) Anton Paar Germany GmbH, Hellmuth-Hirth-Str. 6, 7 - Ostfildern - Germany

In this work combined rheological techniques with novel parameters were investigated. One of these additional parameters for rheological measurements is humidity control. Rheology combined with temperature and humidity control is a powerful tool to characterize polymers. The influence of relative humidity on mechanical properties of films was investigated using the humidity option of a CTD (convection temperature device). Humidity step tests and humidity ramp tests at constant temperature as well as temperature scans at constant relative humidity were performed to study the influence of temperature and humidity independently. This feature can be extremely useful when measuring poly condensation products such as polyamides that can be influenced from relative humidity on the modulus value and the glass transition temperature due to moisture absorption. Furthermore adhesive sealant formulations especially in regard to curing and hardening behavior were investigated with a new measuring geometry. This Plate Partitioned Ring geometry shows the advantage of a higher surface to volume ratio in comparison to the plate-plate geometry. Because of this and the low sample volume, the entire sample will be much more affected by the ambient humidity conditions. In addition to chemical composition, ambient conditions are key influencers on the curing and hardening behavior of sealants and adhesives. While the influence of temperature on the rheological behavior of adhesives has been extensively investigated, the impact of relative humidity on the mechanical properties of such materials is of increasing interest recently. It could be shown that the water uptake of polymers caused by humid ambient air has major impact its thermo-mechanical and rheological properties. The complex shear modulus of polyamide strongly decreases over time, when the humidity of the surrounding air is increased. Furthermore the glass transition temperature also strongly depends on the humidity of the measuring environment. The rheological behavior and curing rate of adhesives is also strongly affected by relative humidity. It could be shown that the crossover of G´ and G´´ of silicone based adhesives decrease with increasing relative humidity. Hence, the impact of the ambient humidity as well as the temperature on the determined rheological parameters can be used to characterize the curing process of resins and mechanical properties of solid polymers at various ambient conditions. Keywords: Humidity, Rheology, DMTA