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PostPosted: 10 Jan 2018, 09:34 
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iskandar taib wrote:
Yeah, we need the high speed cameras... :lol: This is weird.. backspin behaves one way, topspin the opposite.

Iskandar


https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5304273/

Some interesting observations on plastic and celluloid balls using high-speed camera.
Balls under study were as follows:
-- Nittaku Premium 40+ (ABS plastic)
-- Nittaku Premium 40 (celluloid)

Mr. Yuki Inaba of Japan © Editorial Committee of Journal of Human Kinetics, published January 2017 wrote:

Conclusion
Changes between the trajectory of celluloid balls, which had been long used in table tennis, and newly introduced plastic balls were investigated in this study. Plastic balls demonstrated a higher coefficient of restitution than celluloid balls when the initial vertical velocities were higher. Moreover, the coefficient of friction was higher for plastic balls when the initial horizontal contact point velocities were lower. As a result, for slower balls with back-spin, as in the case of a service, plastic balls are expected to experience more deceleration upon collision with the table than celluloid balls. On the other hand, for faster balls with greater amounts of top-spin, plastic balls are expected to experience greater acceleration upon collision with the table than celluloid balls.


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PostPosted: 10 Jan 2018, 13:00 
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I am really confused now. I read that "poly" balls were polystyrene and that is how they got their name, even though I assumed "poly" was short for polymer. Now I read that Nittaku "poly" balls are ABS. So does poly mean polymer or polystyrene?


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PostPosted: 10 Jan 2018, 13:14 
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rsilvers wrote:
I am really confused now. I read that "poly" balls were polystyrene and that is how they got their name, even though I assumed "poly" was short for polymer. Now I read that Nittaku "poly" balls are ABS. So does poly mean polymer or polystyrene?


No, the word "poly" simply means "many", and is a root for many names given to POLYmers (including what are generally known as plastics). POLYstyrene is a polymer made up of repeated units of the MONOmer styrene (go look it up - double benzene ring). Similarly, POLYethylene is made up of repeating units of ethylene (or ethane, C2H4) and POLYvinyl chloride is made up of repeated units of vinyl chloride joined together end to end.

So the "poly" ball is simply a ball made of non-nitrocellulose plastic (never mind that nitrocellulose, or "celluloid", IS also a polymer or plastic - one of the first materials to be used as such, incidentally). Materials used so far have been cellulose acetate (the older DHS and Double Fish 40+ balls, which were sold under many, many brand names), what I think is polyurethane (the Minkow factory say their seamless balls are "P.U.", and this, by extension, means all seamless balls), and acrylonitrile butadiene styrene, a polymer in common use for years and years for such things as car parts (these would be the new DHS D40+ balls and a few others - and the DHS ones will probably be sold under other brands as well). Oh yeah - I saw some polypropylene balls at the local Daiso too - but you probably wouldn't want to play with those. Cheap enough for cat toys though.

Iskandar


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PostPosted: 10 Jan 2018, 16:26 
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The fact that poly means many doesn't explain why that name was given to the newer plastic balls, so I think that in this context, "poly" balls means polystyrene (PS) - the first new material used, and people are just incorrectly calling ABS balls the name originally given to these PS balls.


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