sulfurous vapors emitted from epdm rubber can damage electronic instruments.
The emission of sulfur can cause a big problem with electronic components that depend on the chemical inertia of silver. When moderately heated, the EPDMrubber compound releases a sulfur-free compound Contains compounds. Carbon sulfur ([CS. sub. 2]) And sulfur carbon ( Also known as carbonyl sulfur, COS). This paper discusses the identification of the problem and the simplified solution of the problem. It assumes but does not confirm a possible source of sulfur vaporB-C rubber sulfide. The problem of sulfur emission silver is usually the preferred metal for electrical contacts in switches and relays. It is usually the preferred material for thinfilm orthick- Film Deposition of conductive materials for electronic filters or tuners. Unfortunately, as noted later in the free energy discussion, silver is prone to react with sulfur compounds. Due to the loss of gloss on this black surface, the overall sulfur film is not conductive and the switch contacts may fail. In extreme cases, Silver may actually be etched, resulting in a change in the resonance frequency of the electronic tuner. Copper is more reactive to sulfur vapor, as are lead and tin in welding. The nature of these materials and their use affect whether the gloss of sulfur is critical to the performance of electronic instruments. Disk drive manufacturers have solved the problem of carbon dioxide emissions from ethylene-propylene rubber, especially where the bearing seal is made of this rubber. The discharge of sulfur has caused serious damage to the bearing materials of lubricating oil and disk drives. A nasa website lists the gas properties of materials that may be considered for use in spaceships and satellites -- The six lists of EPDMrubber artifacts show 3. 4 to 26. 4 The percentage of weight released by rubber within 24 hours is 125 [degrees] C, displayed from 1 to 14. 6% condensable substances in these materials- For these applications, it is far beyond what is allowed. The basic list does not determine the nature of the chemicals that release the gas from the B-C rubber. Chemical reactions and their Free published datag. The Handbook of Chemistry and Physics provides data on the formation free energy of many different chemical compounds. Free Energy of reaction at 20 hours [degrees] C can be calculated directly from these figures, subtracting the formation energy of the reactants from the formation energy of the reaction product. This, of course, requires an equation for the balance of chemical metrology. The free energy of an element is considered to be zero. If the free energy is reduced, the reaction is likely to move in the written direction. This is equivalent to the potential energy conditions of the rocks on the hillside -- It can spontaneously scroll down to a lower level of energy. It can\'t go uphill automatically. The calculation does not necessarily predict whether the reaction will occur, as the rock may be embedded in the soil and may need to kick up for a period of time before rolling down. For example, the reaction of cellulose to oxygen is an adownhill reaction, but fortunately, the paper must reach a higher energy state ( Ignition Temperature) Before they ignite and burn to a low energy state. The probability of these events is shown in Table 1. Two of these reactions are the first to show how sulfur-2 carbon is converted into carbon-oxygen sulfur. The next four shows show that silver and copper may lose luster when in contact with these steam. Zinc carbonate reaction (7) The use of disulfur carbon shows how zinc compounds can be used as a safe \"gas-absorbing agent\" or reactants for the removal of disulfur carbon from the environment. However, this reaction is not as dynamic as the reaction of disulfur carbon to silver, so it needs to be positioned in this way as a shield or shield between the source and silver to be protected. Reaction 8 shows how galvanized steel mesh or brass mesh is used as a molding shield for this protection. The identification and quantification of sulfur compounds Anelectronics manufacturers received complaints about the \"black box\" of the customer\'s sorry role after using it for about five years. He saw visible evidence of black silver discoloration on the sensitive surface of the returned instrument. This prompted the examination of silver with a scanning electron microscope and an energy scattering spectrum, confirming the presence of sulfur on the surface of silver. Figure 1 shows a photo of the silver membrane oscillator, and its connection to the circuit on the PC board, Figure 2 shows damage to the oscillator, electrical disconnection in the lower right corner, and two hydrogen sulfide black spots on the center surface. [ Slightly] Illustrations The manufacturer then learned that sulfur is contained in the ethylene-propylene rubber gasket for sealing electronic packaging. With this thread, some boxes and some washers were taken to the Hauser lab to identify and quantify the steam inside the box. A box containing helium, and then analyzed it by gas chromatography and mass spectrometry (GC/MS) The presence of sulfur-2 carbon and carbon-oxygen sulfur was confirmed. The free volume of the box is about 1. 85 liters and a weight of about 10 lbs. 8grams. The material of the box is glass. The printed circuit board seems to be a common epoxy G-10 laminate. These electronic packages can be exposed to temperatures up to 150 [degrees] F during transportation, repeated during use. Most customer complaints come from the \"sunshine zone\" in the United States \". S. For this reason, an experimental project was carried out using GC/MS: * in a box heated to 65 [s], the production of sulfur-free steam was accelerated with three gases free of ethylene-propylene rubberdegrees] Two hours. * After removing the sealing gasket from the \"old\" box, rinse the residual sulfur vapor with helium to find out if the enzyme and the circuit board absorb the sulfur compound. The box is heated to 65 [degrees] C. Place it for two hours with silicone rubber gasketin. * Decay properties of sulfur steam in the box when heated to 65 [degrees] Rinse with helium. * Similar tests to confirm the treatment effect of removing sulfur vapor. Figure 3 shows the electronic box with the circuit board after the first deflation test, as well as three B-C rubber washers. The number of this box is very large (About 3. 7 micrograms) The harmful vaporizer is removed from the oven, mainly disulfur carbon. [ Slightly] Illustrations The second test showed that two sulfur-free steam remained in the box after removing the ternary rubber gasket. Carbon sulfide is particularly common in electronic components, while carbon sulfide is particularly common in box materials. Figure 4 shows the features of carbon disulfur separation and flushing time in a box with pleats under 65 [2 hours]degrees]C. These are concentrations at room temperature within three days of removal from the oven, and fluorine tiles pushed inside and outside for three days, in order to completely remove harmful steam within about five days. [ Slightly] Illustrations Treatment of removal of sulfur vapor since activated carbon is an effective adsorption agent for these steam in a thermal analytical box for GC/MS, if a pack of activated carbon is placed in a sealed box, it should be effective Such a package was prepared using a 12g chemical grade charcoal adsorption agent and it was found that it effectively adsorbed harmful gases. Contact the commercial supplier of the adsorption package and recommend the use of apacket containing activated carbon and high manganese salts to prove effective in hydrogen sulfide environments. The oxidation reaction of potassium permanganate may be through the following reaction :[CS. sub. 2]+ 4KMn[O. sub. 4][right arrow]4Mn[O. sub. 2]+2[K. sub. 2][SO. sub. 4]+ 2[K. sub. 2][SO. sub. 4]+ C [Delta]G = - 1853 kilojoules/gmolHowever however, the test showed that the sulfur concentration did not decrease during the 16 hours degrees]C. Then, a package consists of the activated carbon of this supplier, there is no additive at home Envelope Tyvek ( Part of the mail envelope). With 15 grams of carbon, the carbon disulfur disaggregation in the old box is now knocked down by 99. 8%. Only 0. 05 nano grams 【CS. sub. 2] Stay in the box. Carbon suppliers expect carbon absorption to be as high as 0. Its weight is 6% [CS. sub. 2]and to0. It weighs 1% of COS. Although the total capacity of charcoal cannot be quantified within its lifetime, this material is considered to be very effective for the adsorption of sulfur compounds with micrograms resolved from the packaging. A pack of zinc carbonate may be as effective as the \"suction agent\" of the sulfur compound in the reaction 7 in Table 1, and the reaction shows 0. 3 grams of sulfur carbon reacted with 1 gram of zinc carbonate. Copper and lead compounds also react with sulfur-2 carbon, but zinc is more favorable for the environment. It is better to avoid this problem than to have to solve it. If B-C rubber is the preferred rubber for electronic packaging, it should be designated as Peroxide curing. Before the product is sent out for beta testing, chemical analysis of sulfur content should be performed on qualified samples of rubber. The list of vulcanization or accelerated chemicals in table 2 is not common in ethylene-propylene-three-way rubber. In their structure, all carbon atoms are attached to two sulfur atoms, which may be the source of carbon dioxide release. Free sulfur is usually used at a concentration of 2 phrcentration in ethylene-propylene glycol rubber. Industry insiders mentioned that at present, sulfur and about 75% of peroxide are used for vulcanization in about 25% of products. A peroxide- The cured rubber should be free of sulfur. Silicone rubber is a more expensive alternative, but for non- Vulcanization rubber. Conclusion The sulphur agent listed above is used in many other elastic bodies, and we have not heard of any carbon-sulfur bond problem except for the ethylene-propylene rubber product. Most rubber has a large amount of active shunding, so it is highly reactive to any sulfur that may exist. B-C rubber is unique as it has only a few cross sites (vinyl radicals) Therefore, the possibility of residual sulfur compounds from the decomposition of vulcanization and accelerator is greater. Ray Hauser started his rubber career in 1950 at the ConnecticutHard rubber company he worked. The first American inventionS. Patented process for bonding Teflon. His current consulting programs include problem solving, patent litigation and product liability litigation.