Outgassed products

Another important application area for PSAs in the electronic industry focuses on the manufacturing, transport and assembly of electronic components into larger devices, such as computer disk drives. Due to the sensitivity of these components, contamination with adhesive residue, its outgassing products, or residue transferred from any liners used, needs to be avoided. Cleanliness of the whole tape construction becomes very critical, because residuals like metal ions, surfactants, halogens, silicones, and the like can cause product failures of the electronic component or product. Due to their inherent tackiness, acrylic PSAs are very attractive for this type of application. Other PSAs can be used as well, but particular attention has to be given to the choice of tackifier or other additives needed in the PSA formulation. The choice of release liner also becomes very critical because of the concern about silicone transfer to the adhesive, which may eventually contaminate the electronic part. 

Jansen and co-workers [86] have evaluated temperature-controlled outgassing processes of plastics and rubbers using both off-line and on-line TD-GC-FTIR-MS. Decomposition of polyesterurethanes by means of TG-Tenax off-line sampling followed by TD-GC-FTIR-MS revealed C02, H20, tetrahydrofurane, cyclopentanone, dicarbonic acid, aliphatic diols and esters [86]. The same authors have also described the detection of polychlorinated biphenyls (PCB) in 2,4-dichlorobenzoylperoxide cured silicone rubbers after outgassing products of a rubber silicone part obtained after desorption for 10 minutes at 200 °C in the thermal desorption cold-trap and subsequent analysis by means of TD-GC-MS. Using a mass range of 290-294 Da the MS can be used as a selective detector for these substances. 

Table VI. Composition of Printed Wiring Board Offgassing/Outgassing Products After...

Outgassing from poly (7-butyl aery late) during exposure at 157 nm has been studied, and among the outgassed products isobutene, isobutene, acetone, isobutanal, and isobutanol were detected [77],... 

Gas sampling valves are usually mounted in the column oven, in a separately heated adjacent oven, or external to the column oven and connected to the column by a short length of capillary tubing. For the most accurate work it is generally recommended that the injection valve is thermostatted in its own oven. Since the valve materials are in contact with the sample they must be chemically and physically inert, free from outgassing products, gas tight at all temperatures, and operate without lubricants. 

None of the silicone polymers studied produced a maximum amount of condensables during the 225 hour test. The outgassing products were being evolved and condensed at the same rate at the end of the test period as were observed during the early stages of the test. Linear curves usually indicate a slow continual... 

Silicones Polymers. The outgassing products from silicone polymers initially condense on the glazing as liquid alkyl linear and/or cyclic polysiloxanes. These liquid condensates have been observed to form on solar collectors after several days of testing in the Arizona desert. The liquid polysiloxanes do not appreciably affect the relative light transmittance. However, as the thin film is exposed to the harsh environmental conditions encountered during three months of desert testing, it is slowly converted into a white colloidal silica powder through the follov/ing type of overall reaction ( ). 

Butyl Polymers. The outgassing products from the butyl polymers also initially condense out as liquids and are slowly converted into tan colored solid varnish-like deposits. These resinous deposits are formed through a thermal oxidative degradation process as follows ... 

Carbon felts can be used as an insulation material, made from scrap material which is relatively cheap, where further carbonization continues in use. Under these conditions, the possibility of shrinkage and outgassing products has to be accommodated. Superior, but expensive, carbon and graphite felts can be made by carbonizing long small diameter organic filaments, which are very stable and have low shrinkage. 

The most prevalent outgassing product in vacuum machinery systems is water absorbed by chamber materials. It can be reduced by desiccating the chamber and removing absorbent materials. Outgassed in the form of water can be condensed by oil of rotary pumps and reduce their net speed. High vacuum systems are relatively more clean and free of organic materials to minimize outgassing. 

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