Investigation of the effect of relative humidity on polymers by depth sensing indentation

Abstract

___________________________________________________________________________ AbstractStereolithography (SL)resins absorb varying amounts of moisture dependent on the relative humidities, which can significantly affect the mechanical properties. In thiswork, the influence of relative humidity (RH) on the mechanical behaviour of an SL resin is investigated using depth sensing indentation (DSI). The samples were conditioned by two methods. In the first method, samples werepre-conditioned at 33.5%, 53.8%, 75.3%and 84.5% RHusingsaturated salt solutions. These preconditioned samples were tested at 33.5% RH, using a humidity control unit (HCU)to control RH in the DSI system. In the second method, samples were conditioned and tested at 33.5%, 53.8%, 75.3%, 84.5% RH by regulating humidity in the DSI system using the HCU. Temperature was kept constant at 22.5°C for the conditioning and DSI testing.It was seen that hardness and modulus decreased with increasing RH and conditioning time but recovered significantlywhen tested after drying.This study demonstrates that RH needs to be taken into account when DSI testing of polymers.

Nanoindentation for probing the mechanical behavior of molecular crystals–a review of the technique and how to use it

“…Such changes in the water content of the sample can exert a significant influence on its measured mechanical properties. [17][18][19] Hence, it is important to keep track of the relative hydration levels in the specimen as well as the humidity in the nanoindenter chamber, and make sure that the tests are performed without an inordinate delay between synthesis of the crystals and their testing.…”

Effect of accelerated weathering on the creep behaviour of additively manufactured Polyethylene Terephthalate Glycol (PETG)

“…The applied load is 1.4kg Fig. 13 The creep compliance of UV exposed samples where ageing is excluded during testing. The applied load is 2.8kg…”

“…Limited studies have been conducted on the interaction of these two fields of research: creep of additively manufactured materials; and the effect of weathering on the creep response. Türk et al [12] assessed the temperature influ ence o n creep o f a ddit iv ely manufactured samples whereas Altaf [13] investigated the effects of humidity on the creep response of thermosetting Accu ra 6 0 printed using the stereolithography method.…”