Weight gain method

During the past few years four methods have been developed for the study of the kinetics of oxide film formation, all being semicontinuous in nature. The polarimetric method has been adapted by Lustman and Mehl (14) for the measurement of the oxidation of copper. A spectro-photometric method has been applied by Waber, Sturdy, Wise, and Tipton (15) to the study of the oxidation of tantalum while a differential pressure method has been developed by Campbell and Thomas (16) for a study of the oxidation of a series of metals and alloys at elevated temperatures. We have chosen to use a sensitive weight gain method (17,18) in which a quartz microbalance is placed directly in the vacuum system. 

In order to elucidate the effect of water absorption on the charge storage behavior of commercial Ultem 1000 films (50 pm thickness Lipp-Terler), samples with various water contents were prepared. The water content was determined by a weight gain method using a Mettler Toledo MX5 micro-balance with a resolution of 1 pg. The water content of as-received films was determined by Karl-Fischer analysis to 0.74 wt%, compared to an equilibrium water absorbance of PEI at 1.39 wt% [27, 74], As a preconditioning step, the specimens were dried under vacuum at 125 °C for 24 h to ensure a water content of less than 0.02%. By additional immersion treatments, the water content of these PEI films was increased to films with 0.45 wt% and 0.66 wt%. 

The other method is the ASTM cup method (34). In this method a desiccant is placed in a waterproof dish. The dish is covered with the experimental film and placed in an environmental chamber. The temperature and humidity ate set for the conditions of interest, typically 37.8 °C and 90% th. At regular intervals, the dish is removed and weighed. After a few days enough data have been gathered to describe a steady-state rate of weight gain, and the WVTR can be calculated. Typical experiments take about a week to complete. 

Extent of polymer swelling is often gauged by gravimetric method - one monitors the weight-gain of a poly-... 

The percent reaction was typically determined by elemental analysis however, in the case of cross-linked polymers, the percent reaction was also evaluated by titrating the amount of chloride liberated and by measuring the weight gain of the polymer resin. All three methods gave comparable results (within 2-3%). 

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