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detrmine material typ from hardness test

detrmine material typ from hardness test

detrmine material typ from hardness test

(OP)
does anyone have experience, know
if a given polymer materials behaviour
can be characterised reliably as being
brittle or ductile at a given Temperature
by, say, a SHORE hardness value?

Or is this to sloppy, to vague
as a criteria.

It's clear that you can just drop the pice
and see what happens, that (may) give an idea.

But question applies if you haven't a pice,
can't brake it, need a more definite answer,
have e.g a SHORE value from specs at hand only.

Thanks,
Frank

RE: detrmine material typ from hardness test

No, this would only work for a well-defined material (especially, density & MW) having a known T curve.
For example, the same material can have different Shore nummbers at a given temperature depending upon filler or density (if a celluar material).
See catalog pages 3250 for Neoprene rubber of different hardness in http://www.mcmaster.com/
A very brief comparison of the various Shore scales is on p. 3242.

RE: detrmine material typ from hardness test

(OP)
thank's kenvlach,

but if the material IS well defined in terms of
density, MW(what is MW for cortesy) and
SHORE scale & value is available in line with
www.mcmaster.com/catalog/109/gfx/small/j2duroxxs.gif

Would this be sufficient to distinguish brittle
from ductile stuff - speaking about homogenous
plastics as duro/thermoplast type plate/stick/bar
(no rubber, foam, composite) only ?

By ductile vs brittle I mean:
ductile: break at ultimate strenght at finite strains
         does not break easily with impacts
brittle: break at about yield strength w/o any much strain
         does break under impact e.g. droptest

Thanks again,
Frank

RE: detrmine material typ from hardness test

(OP)
to focus in, I'd intend the 'extra hard'
range of the picture in the link

Regards,
Frank

RE: detrmine material typ from hardness test

Hi,
MW = molecular weight is proportional to degree of polymerization.
I think of Shore hardness for 2 things: specifying properties & a rough QC method to determine degree of polymerization. I've never heard of it being used to identify a material, but yes, it could give information for that purpose in conjunction with other observations and meaasurements.

Re your original question "if a given polymer materials behaviour can be characterised reliably as being brittle or ductile at a given Temperature by, say, a SHORE hardness value?
-- I would agree that a given set of solid plastic samples of the same material but different MWs (& crosslinking, if applicable) could be arranged in order of Tg by doing hardness measurements.

RE: detrmine material typ from hardness test

(OP)
Hello,

you say "I would agree that a given set of solid plastic samples of the same material but different MWs (& crosslinking, if applicable) could be arranged in order of Tg by doing hardness measurements". I assume Tg is the glass transition temperature.

I'am unable to derive a statement wrt the question asked, so I conclude the answer is a clear 'maybe'. Concluding further that the conclusion is, that plastics, as with metals, can't be judged being ductile or brittle by means of a hardness test alone.

Frank Exius
IFE Bonn Germany
www.ife.subito.cc

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