Plasticizer problem

What you refer to as "Doll's Disease" is an entirely different phenomena that the leaching of plasticizer. Doll's Disease is actually a result of cellulose acetate reacting with the moisture in air to produce degraded cellulose and acetic acid (the vinegar smell). Originally it was seen in celluloid movie film, collar stays, etc. Celluloid is cellulose nitrate with a little plasticizer but the plasticizer has nothing to do with the reaction. With cellulose nitrate, nitric acid is produced. Once the reaction occurs, the acid catalyzes further degradation of the cellulosic plastic. Museum storage in sealed glass cases actually promotes the process. About all that can be done is to neutralize the acid by washing in a dilute sodium carbonate or bicarbonate solution, drying carefully, and placing the item back in storage with flowing dry air.

The problem you are seeing is the leaching out of plasticizer from polyvinyl chloride or polyvinyl acetate items. If you are old enough to remember vinyl automobile seats, you probably also remember the greasy film formed on the inside of windows when the car was parked in the hot sun. Over time, the vinyl would get brittle, shrink, and crack. The film was plasticizer that evaporated from the vinyl. As it left the PVC, the shrinkage. brittleness and cracking occurred. One of the more common plasticizers was bis(2-ethylhexyl) phthalate, more commonly known as dioctyl phthalate or DOP. It is still in wide use today, but many newer plasticizers are also available today such as trioctyltrimellitate (TOTM), dioctyladipate (DOA), diisononyl phthalate (DINP), di(2-ethyl hexyl) adipate (DEHA), acetyl triethyl citrate (ATEC), and even tricresyl phosphate (TCP).

Plasticizers are incorporated with PVC in the manufacturing process.

put plasticizer back into the vinyl with a surface applied product. Many products may contain significant amounts of plasticizers. Very soft and rubbery PVC compounds may contain as much as 40 to 50% plasticizer. Preventing the leaching out or evaporation of plasticizers from vinyl products is prevented more by the choice of plasticizer than anything else, although low temperatures slow the rate significantly. The Wiki page on plasticizers lists a large number of plasticizers and tells where they are most used.

About the only way to prevent plasticizer damage to other plastics is to keep vinyl products away from them. Most coaxial cables for radio frequency use have a center conductor insulated with polyethylene, a wire braid shield, and a plasticized PVC jacket. When the plasticizer leaches from the jacket into the polyethylene, its electrical losses increase greatly. One modern innovation uses either aluminum foil or metalized polyester to wrap around the braid preventing the ingress of the plasticizer. But it also provides better shielding allowing the braid coverage to be lessened from 90 to 95% coverage to less than 75% coverage leading to a much lower weight.

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Many thanks for the full reply. I was totally unaware of the last point, so have added s.e.r as probably a lot there are unaware also. Recently reminded me of this effect because a "rubbery" presumably soft PVC suspension inside a phono cartridge was leaching plasticizer and softening the surrounding hard plastic etc. I don't know if it is also related but often if one "rubber" drive band in a VCR or audio tape deck perishes, then all the others are likely to fail in a sort of contagion -plasticizer gas wafting around inside ?

You are quite welcome. Eastman Chemical Company, a former employer, made both cellulosic plastics and a large number of plasticizers. I even worked on a project to replace plasticized PVC in medical intravenous solution bags with an elastomeric polyester because of the fears of plasticizers leaching into the solutions (which they do!). While being more expensive than PVC, our material was much stronger allowing thinner bags which offset this higher raw material cost. But the perimeter radio frequency sealing process required new equipment and the bag manufacturers were unwilling to modify their manufacturing lines.

As far as VCR decks, I cannot think of any mechanism whereby the failure of one drive belt via plasticizer migration would cause the others to fail unless the plasticizer leaching from one belt actually dripped on another belt. Remember that all belts were likely made at approximately the same time, and had been in the VCR exposed to similar high temperatures for the same time too.