Hardness of Plastics - Rockwell & Burnell scale
This has been touched on elsewhere, but I want to get some clarification.
Taken from the commonly available Properties of Plastics Chart, the hardness characteristics (Rockwell & Burnell):
Acetal: R120
PVC: R112
Poly: R118
Acrylic: M93
Is the higher number on the scale harder or softer? How does acrylic compare to these other three given the M-rating.
Taken from the commonly available Properties of Plastics Chart, the hardness characteristics (Rockwell & Burnell):
Acetal: R120
PVC: R112
Poly: R118
Acrylic: M93
Is the higher number on the scale harder or softer? How does acrylic compare to these other three given the M-rating.
Last edited by carter on Thu Jan 27, 2011 3:13 pm, edited 1 time in total.
A higher number means harder, although the M scale and R scale use different test weights and aren't equivalent. But those scales measure hardness in terms of indention/deformation, not in terms of resistance to cutting or scratching, so they don't relate perfectly to how easy a plastic may be to cut. Some type of scratch hardness rating would be more applicable, but I have never seen a chart for plastics.
Mark
Mark
- JuanPabloCuervo
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http://en.wikipedia.org/wiki/Polycarbonate
Polycarbonate M70
Speed of Sound 2270m/s
melting 267°C
Termal conductivity .19 - 22
Heat Capacity 1.2 - 1.3
***
http://en.wikipedia.org/wiki/Polymethyl_methacrylate
acrylic glass
Melting 160°C
PMMA was used in laserdisc optical media. (CDs and DVDs use both acrylic and polycarbonate for higher impact resistance.)
http://en.wikipedia.org/wiki/Vinyl_polymer
http://en.wikipedia.org/wiki/Thermoplastic
***
http://en.wikipedia.org/wiki/Copper
Speed of Sound 3810m/s
Melting 1084°C
Polycarbonate M70
Speed of Sound 2270m/s
melting 267°C
Termal conductivity .19 - 22
Heat Capacity 1.2 - 1.3
***
http://en.wikipedia.org/wiki/Polymethyl_methacrylate
acrylic glass
Melting 160°C
PMMA was used in laserdisc optical media. (CDs and DVDs use both acrylic and polycarbonate for higher impact resistance.)
http://en.wikipedia.org/wiki/Vinyl_polymer
http://en.wikipedia.org/wiki/Thermoplastic
***
http://en.wikipedia.org/wiki/Copper
Speed of Sound 3810m/s
Melting 1084°C