Film life

P. Eaton and G. Sutton. The effect of flow on inhibitor film life. In Proceedings Volume. 49th Annu NACE Int Corrosion Conf (Corrosion 94) (Baltimore, MD, 2/27-3/4), 1994. 

Oxidative Stability of Carboxylated Polyesters. The polyesters which were extended with dianhydrides are those in Table I which were soluble in the lacquer solvents. Of these, theoretical considerations indicate that T50I(NPG) should be the most oxidatively and thermally stable because it is the only one with a completely aromatic acid component (terephthalic and isophthalic), and the glycol component has the stable neopentyl structure. When K-l polycarbonate films containing 5% of this polyester extended with PMDA were heated in a forced-air oven at 200°C, the film life (time to brittleness when creased) was not lowered appreciably (compared with a control containing no carboxylated polyester). The incorporation of 5% of the similar carboxylated T50H(NPG)... 

It is interesting to note here that the beneficial effect of phosphating on film life is quite small if the substrate has an optimum surface finish of 0.5//m, and this supports the suggestion that the benefit of phosphating is at least partly in providing a suitable surface texture. 

Figure 7.13 Variation of Bonded Molybdenum Disulphide Film Life with Sliding Speed Ref. 183)...

One factor which may be partly responsible for longer film life in inert gas or vacuum is an improvement in the formation of a transfer film on the sliding counterface as described by Fayeulle et al . Formation of an effective transfer film on the counterface can have a significant effect in reducing wear of the primary film. 

An alternative explanation is suggested by some later work of Fleischauer and Bauer °°. They found that the best performance of transfer films of molybdenum disulphide was obtained when molybdic oxide was present in the lowest layers of the film adjacent to the steel surface. Oxidation to molybdic oxide is increased in the presence of moisture, so that reduction of moisture content due to frictional heating may reduce the amount of molybdic oxide present, and thus have a direct adverse effect on transfer film life as well as reducing the rate of film formation. Fleischauer and Bauer also found indications that transfer film life was improved if a slight excess of sulphur was present at the interface between the film and the substrate. The presence of molybdic oxide or excess sulphur are undesirable in the bulk of the lubricant and especially on the sliding surface and they suggested that for optimum... 

Figure 10.8 Variation of Sputtered Molybdenum Disulphide Film Life with Gold Content (Ref.307)...

A number of different metals have been used in powder form as additives to bonded molybdenum disulphide films. They include gold, silver, nickel and tantalum, and it has been suggested that they improve film life by helping to facilitate readhesion of lubricant debris to the substrate. Many other components have been added to bonded films as corrosion inhibitors, anti-oxidants, dispersion stabilisers and biocides, and many different solvents have been used. There is therefore an almost infinite variety of possible formulations, and several hundred have been produced commercially. 

Adhesive seal for 96-well plate (MicroAmp Optical adhesive film Life Technologies). 

Figure 1 shows a set of IR spectra demonstrating various stages of PSiPI film life. IR spectrum A is the uncured, untempered film. Note the methacrylate double bond at 1640 cm l. IR spectrum B shows the same film after UV irradiation the absence of the carbon carbon double bond is apparent. IR spectrum C shows the PSiPI film after thermal tempering at 300°C which converts it to SiPI imide. For comparison, a pure sample of imidized SiPI is shown in IR spectrum D. Also, when a sample of PSiPI was ring closed at 300°C, the Tg of the resultant polymer was 190°C which is the Tg of unmodified fully imidized polyimlde slloxane. 

Two UV stabilizers gave the results in Table 6. These materials produced a 2-4X increase in the useful life of the film. The positive effect of these materials on film life also supports a photooxidative mechanism for film failure upon weathering. 

Both the in vivo and in vitro studies were completed using intrinsic viscosity measurements in benzene and also gel permeation chromatography to determine film life. The general conclusions reached were that poly e-caprolactone homopolymer would last around one year, while a copolymer of PLA and PCL had much shorter degradation times. For our purposes, however, both had too long a lifespan. Accordingly, additional studies are needed to develop films with the desired shorter degradation times. 

A recirculating dynamic test method can be used when it is desired to simulate fleld flow or operational conditions. Some of the parameters that should be controlled are the velocity of the corrosive medium, the oihwater ratio (in case of oil-field inhibitors), temperature, and dissolved gas and/or air concentration. Variables that can be imposed are the type of corrosive medium, the concentration of inhibitor, the effect of precorrosion of the test specimen, and the type of inhibitor treatment. This type of flow test provides a more severe test of inhibitor film life than the static bottle test. It furnishes a useful technique for the study of variables affecting inhibitor performance. Correlation between laboratory tests and field use of inhibitors is better using this technique than it is using data from the static test. 

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