Isopropyl Alcohol leaves a white haze on plastic, is there anything I can use to clean it off?

Question

Recently I wanted to clean up some lubricant on some keyboard switches. On some forums, an Isopropyl alcohol bath was recommended so I decided to give that a try and went to purchase some 91% Isopropyl from Target(purest I could find near me and I admit, I am a little impatient).

Good news - it worked in getting the lubricant off the switch! Bad news, on some of the switches, it left this white haze.

I'm not sure what it is, though from what I've been reading, it sounds like this is a common issue when using Isopropyl, my best guess is that it's some mix of the lubricant mixing with the alcohol and reacting poorly with the switch housing plastic given that I'm only seeing this haze on the bottom half of the switches which were the only parts of the housing that were lubed, the other parts are clean. Another reason for my guess is that this haze isn't appearing in the same amounts on all the switches if at all, some switch bottoms are basically clear.

It does appear to scrape off but looks like it will require a fairly strong brush which I don't have at the moment and I'm not sure if there's one available for purchase that could be used in this situation.

Is there any plastic-friendly household cleaner available that might be able to help speed up the process?

Answer 1

Even the common alcohol ( ethanol, ethylalcohol) is known to corrupt surface of some plastics, and rubbing alcohol ( isopropanol, isopropylalcohol) is even better in that, as it contains bigger organic chain and is less polar.

These alcohols do not dissolve the plastics in large extent, like acetone often does, but they may corrupt surfaces, especially if they are shiny or polished.

The typical case is compact polystyren or polymethylmethacrylate, that are often clear and shiny, where the white milky haze is very well visible. The opposite case is filled black shiny plastic where the haze and lack of shining is notable.

For similar reason, lukewarm water with detergents is preferred for plastics cleaning.

The only way I see to get rid of the haze is polishing, or applying a selfpolishing coating, if applicable and worthy. Perhaps polishing of wax coating.

Answer 2

I did this by accident just today. Had gotten an almost new black PA sound system from Freecycle and wanted to wipe it down for germs and used alcohol (90% isopropyl) and it left lots of white streaks. I tried to clean it with soapy water, glass plus, detergent, all to no avail. Then tried comet and that may have helped a little and then I saw someone mention toothpaste and the earlier answer here speaking to polishing and I put the two together and recalled that's an approach for car lights. In any case, it worked like a charm. A couple rounds of scrubbing with a white toothpaste/toothbrush (Colgate) with a rinse in-between and then some buffing with a towel and the PA system is back to normal...so toothpaste is a good abraiter I suppose to assist in polishing.

Answer 3

A reason for using isopropanol to clean greasy surfaces is that it has a lower surface tension (21 dyne/cm) than water (72 dyne/cm). The same effect (reduced surface tension) can be achieved by adding 0.1% of surfactant to water.

The difference is that 0.1% of additive in a non-solvent hardly dissolves anything, ever, while 91% of a solvent is almost as good as the pure solvent.

A possible way to use isopropanol, which is a really good cleaner, is to add non-solvent (water) to decrease its solvent power, while hopefully not diminishing its surfactant action (reducing the surface tension of the water). In fact, adding just 20% of isopropanol to water will reduce its surface tension to 30 dyne/cm, which is a big reduction and will help cleaning a lot, but this will probably reduce the solvent power of the mixture by at least 80%. A quick wipe with a cloth wetted with a 20% solution of isopropanol could remove grease, leaving only a little of the solvent mixture, which would quickly lose more isopropanol by evaporation.

Soaking in the mixture would tend to allow isopropanol penetration of plastic; a quick wipe minimizes the exposure. The isopropanol mixture does have an advantage over detergents in that detergents may leave some involatile residue if you use too much (remember 0.1%!), but isopropanol and water are completely volatile.

A very very light rub with a cloth very very lightly saturated with a mineral oil, petroleum jelly or silicone oil could fill in the voids created by partial solution or disruption of the polymer matrix and diminish or eliminate the haze.

Beautiful tables of surface tensions of mixtures of water and methanol, ethanol, and propanols at various temperatures are shown at https://pubs.acs.org/doi/pdf/10.1021/je00019a016.