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ABS plastic degradation (brittle) - HP34401A (circa 1992)
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lugaw:
Unfortunately there's nothing we can do about ABS becoming brittle over time because ABS is brittle by nature and a plasticizer is added to make it softer and over time the plasticizer evaporates.  So once it get brittle it's all over.  Also don't trust the used replacement for handles since they also suffer the same defect since they have the same composition as the one you had.  Try to buy a new one even if it's a copy since it is stronger than old handles.
kosine:
ABS doesn't actually contain plasticisers. It's a terpolymer made from three monomers. The acrylonitrile is basically a cyanide group, the styrene is a large benzene ring (you can see why they changed the names!) A copolymer of just those two is known as SAN, and it's commonly used as clear plastic in a lot of kitchenware. The drawers in your freezer are probably SAN.

SAN is quite brittle though, so the modified ABS version was developed to improve on this aspect. The butadiene is normally used in rubbery elastomers as it can be cross-linked. Copolymerising it into SAN makes it tougher, and the result is ABS. The properties are adjusted by simply changing the proportions of the three monomers, so there's no need to plasticise it. Just use a grade with more butadiene content if you need something softer.
EE-digger:
I believe that combustion products of propane and perhaps natural gas can damage plastics.  I can't substantiate this however.  These combustion products will damage or destroy foam such as that used in transit cases.  This info from first hand experience, and a large case designer / supplier.

My 34401A is early Agilent and the handle looks, feels and bends like new.

So, there may be something in your environment that's accelerating the aging, or I just got lucky.

I've had old Fluke equipment that was a dingy brown and with purple cleaner, it ran off like an orange river, leaving new looking fluke underneath.  This just shows that the environment is in and on the plastic.
Cerebus:

--- Quote from: EE-digger on June 14, 2022, 02:26:01 pm ---I believe that combustion products of propane and perhaps natural gas can damage plastics.  I can't substantiate this however.  These combustion products will damage or destroy foam such as that used in transit cases.  This info from first hand experience, and a large case designer / supplier.

--- End quote ---

For both of those gases, the combustion products are essentially water and carbon dioxide, both things that are already in the atmosphere naturally and both are essentially unreactive over everyday temperature ranges with the kind of organics in plastics. So the thesis that "combustion products of propane and perhaps natural gas can damage plastics" is extremely unlikely to be correct.

In a lifetime of using these



I've noticed no tendency to degradation, and I somehow think that the manufacturers would be the first people to discover whether burning hydrocarbon gases near plastics actually causes degradation and would have changed materials many years ago.
lugaw:

--- Quote from: kosine on June 14, 2022, 02:11:39 pm ---ABS doesn't actually contain plasticisers. It's a terpolymer made from three monomers. The acrylonitrile is basically a cyanide group, the styrene is a large benzene ring (you can see why they changed the names!) A copolymer of just those two is known as SAN, and it's commonly used as clear plastic in a lot of kitchenware. The drawers in your freezer are probably SAN.

SAN is quite brittle though, so the modified ABS version was developed to improve on this aspect. The butadiene is normally used in rubbery elastomers as it can be cross-linked. Copolymerising it into SAN makes it tougher, and the result is ABS. The properties are adjusted by simply changing the proportions of the three monomers, so there's no need to plasticise it. Just use a grade with more butadiene content if you need something softer.

--- End quote ---

Thanks for the explanation! I am not a chemist so I just think ABS is not made the same and it depends on the formula used by the manufacturer on how pliable it is and read somewhere that plasticisers are added to make it bendable just like we make the resin in 3d printer flexible by adding flexible resins.
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