Section (A)
Removal of oils, greases, protective coatings, lapping pastes, buffing compounds and some particulate contaminants. This is the most common area and has traditionally been the area that Trichloroethylene has been used in. With changes in legislation and re classification you have a number of options the most commercially viable being those of alternative chlorinated solvents or n- Propyl Bromide formulated technology.
Chlorinated solvents
Perchloroethylene 121ºC or in the case of Methylene Chloride 38º- 42ºC if formulated rather than just raw material.
Main concerns are as follows -
- Both types are classified as R40 type hazard risks which restricts the use without registration to a 1 tonne limit per year under the SED (Solvents Emissions Directive)
-Chlorinated solvents are not recommended for use on Titanium parts when used in vapour degreasers.
Perchloroethylene can cause distortion in thin gauge metal parts and polymers due to its high boiling point. Process times are longer and energy costs are higher. There is also a risk to operators due to the temperature of parts if they are removed from the machine without sufficient dwell times for cooling.
Methylene Chloride (sometimes called Dichloromethane) with its lower boiling point offers a rapid process time but in a lot of cases may require more than one application especially on thin gauge parts. Also on very small components a refrigeration effect can be created which sometimes draws moisture from the air leaving a reactive surface on parts. Evaporation with the lower boiling point and sg can mean loss of solvent is very high in the summer months in particular without modern equipment to contain it.
n-Propyl Bromide (sometimes called 1 bromopropane)
This is a mid range boiling point solvent of between 67ºC - 69ºC, the odd one may even go as high as 71ºC. There are a range of formulated materials of this type but some are less effective due to the source of the raw materials and the lack of scientific research related to the human bio assay evaluations and test data. These materials have recently been classified as R60 and as such can be used without registration, under the SED (Solvents Emissions Directive), as long as the consumption is below 1 ton per annum. Unlike chlorinated materials this type of chemistry is safe for use on Titanium in vapour degreasing machines. This reclassification is currently under dispute.
Main concerns are as follows -
Whilst no one with all the information disputes that this is not a carcinogenic material, as anticipated, it has been reclassified, due to what industry disputes as false or at the very least mis-information. Currently one of the largest manufacturers has at least one case pending within the European courts. This disputed information is currently being used as a justification for re-classification by the ATP. If the manufacturer wins, the reclassification will be over turned and reduced and n-Propyl Bromide will be offered as one of, if not the safest alternative to Trichloroethylene. Whilst the cost is higher than that of chlorinated solvents the in-use cost can usually be justified.
Section (B)
This area covers applications where the removal of fluxes, conformal coatings from electronic components is required. Due to the mixtures of substrates involved, in for example, printed circuit boards, one single solvent may not be enough for all applications. With changes to legislation regarding lead free fluxes this could prove to be even more valid. The types of solvents mentioned within section (A) above could remove some fluxes and certainly many of the conformal coatings. Unfortunately many of the substrates would also be destroyed. Therefore some of the newer technology solvents tend to be used more readily. These can include:
HFE's, Hydro Fluoro Ethers, HFC's Hydro Fluoro Carbons, HCFC's Hydro Chloro Fluoro Carbons to name but a few, are at this time they are all classified as R20 risk phrase categories, a 2 tonne allowance is allocated under the SED.
Selecting a suitable chemistry is dependant on a number of factors and in most cases a simple test will determine the best option for your application.
Main concerns are as follows:
The single most important factor is the cost. With the need for the products to be used by immersion, initial fill volumes can be expensive. In use cost can be less, for example in the case of HFE's where the HFE part can be recovered and re-used. However leaks or spillages or misuse can be costly. Some concerns have been raised regarding the lack of health and safety data from independent sources, especially when additives are put in which can change the chemical structure of the product - although the industry manufacturers may dispute this. Flammability is also of some concern for some formulations. The range of fluxes used is very extensive and finding the panacea for all types including conformal coatings may be difficult but not necessarily impossible.
Section (C)
This area covers the removal of adhesives, inks, resins from polymers or metals. In this case sections (A) and (B) may fit the bill but equally other types like n pyrodolomine may also be used as could, if acceptable under local HSE regulations , things like acetone, toluene, Xylene and MEK (Methyl Ethyl Ketene) amongst others.
Cured or uncured materials often require different methods of removal and indeed even different chemistries even when used on the same coating.
This area is one that needs specialist investigation to establish the safest and most cost effective methods. If this is your area of concern then please go to the contact us section.
Section (D)
This area will use a wide array of solvent based technologies similar to those shown above. However sometimes as in the case of paint removal, blends of solvents and aqueous technologies, can be used with great effect. These are specialist areas that require detailed examination so we would urge you go to the contact us section.
In any event if you would like more information related to your particular application area please go to the contact us section and we can arrange for a specialist consultation or survey and advise you of your options.
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