composition of calculator cases


Does anyone know what type of plastic was used for the cases of older hp calculators, specifically the 42s and the 48G/GX.?


Traditionally HP used ABS. AFAIK, that's what the 42S and 48G/GX used.


I know you can melt 'em!


Just about anything solid will melt, burn, or sublimate if you get it hot enough.



HP always used ABS on its calculator, and took pride of it every once in a while. Back in 1978 an article pointed out that "ABS, the same material used in football helmets [...] is used for the calculators' cases..."

ABS does melt. Otherwise, it could not be formed. As with almost all polymers, it will melt if heated to the right temperature. Phase transitions (e.g., solid to liquid) do not involve heat only but pressure as well.

My two cents.


Hi Juan,

You said, "as with almost all polymers, it will melt if heated to the right temperature."

I think this is a bit misleading, in the sense that "almost all polymers" is meaningless.

Certainly all thermoplastics will melt, but many thermosets will not.

Examples of polymers that will not melt, but rather will decompose:

crosslinked styrenated unsaturated polyester--"boat resin"
vulcanized rubber
cross-linked PVC
teflon (fluoropolymer)

On the subject of HP calculator cases, I damaged the case of a 15-c with acetone--it dissolved it enough to round off all the edges. It behaved as if it were styrene, but I don't know whether ABS may in fact dissolve in acetone, too. ABS is a terpolymer but is not cross-linked, correct? Therefore it could be dissolved or melted.


It behaved as if it were styrene

It's in that family of polymers... ABS = Acrylonitrile Butadiene Styrene

It is used over basic styrenes due to it's higher impact strength, especially at lower temperatures. Better stress crack ratings are also a factor.

It is resistant to (most):

  • Alkalis
  • Acids
  • Salts
  • Oils and fats

It is *NOT* resistant to:

  • Aromatic hydrocarbons
  • Esters
  • Ethers
  • Ketones

and various chlorinated hydrocarbons (examples):

  • Methylene chloride
  • Ethylene chloride
  • Trichloroethylene


Hello Bill,

Yes, it is a bit misleading. I was thinking of thermoplastics when I wrote my post.

Themoset polymers usually crosslink during polymerization, and the final product has a structure usually impervious to chemicals and/or the external environment. Instead of long polymer chains you have crosslinked chains that form a grid. Depending on the monomers you use, the end polymer can be either very tough or very flexible. And when heated, as you noted, they decompose.

About teflon, "decomposing" is not exactly what happens. Teflon is usually sintered (the powder is heated to about the melting point temperature) and when heated above the melting point, it first turns into long fluorocarbon chains that in turn become the monomer at about 900 degrees (I am getting the temperature from memory, and it may be wrong.) The process is interesting enough and has been researched extensively, but that is another story.

ABS is usually a combination of either polyacrylonitrile/polystyrene and polybutadiene or polystyrene/polybutadiene and polyacrylinitrile (again, I am taking this from memory, it has been a long time since my Polymer Science class, and I might be missing something) that yields a uniform terpolymer.

Another two cents, and please excuse my mistakes.

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