This contradicts what people like Yogi and I have been saying.
Tacky rubbers grip better than non tacky rubbers at low impact speeds as when brushing. When brushing the impact is more tangential than normal. The ball "sticks" to the rubber like a fly on fly paper. It also requires extra force to for the ball to break free. Read the Tieffenbacher document.
Non tacky rubbers rely on the coefficient of friction. One the impact force is high enough, coefficient of friction stops the spin of the ball relative to the paddle except for what ever stretching the of top sheet occurs.
Tsk, tsk...😒
There are so many opinions but no one has facts.
It is important that myths are not perpetuated. The forum should have useful facts instead of useless opinions.
It feels odd and gets old to have the omniscient engineer tell yours truly who has posted countless papers on table tennis topics over the years to keep reading the same document. Let's try something new.
Here is the fact. When it comes to the spin capacity of rubber, regardless of the type(tacky, grippy, shortpips, longpips...), the story is more complicated than just the coefficient of friction(CoF). The contact area and topsheet stretch play a larger role.
M. Varenberg et al. have conducted a study on the CoF of popular inverted tacky and grippy rubbers(Tackiness Drive, Tackiness Chop, Sriver L, 729 FX Super Soft) and non-inverted rubbers(Feint Soft, Clippa, 802, Grass D.TecS). Using a static test, a table tennis ball with different loads(1N, 2N, 3N, 5N) was pulled across the rubber surface facing upward horizontally at 3.5mm/s for a distance of 30mm. The results show that:
1. All rubbers, inverted and non-inverted, show a largely linear behavior in CoF with increasing load;
2. Stickiness appears to be related to surface roughness and tends to be lower for rougher surfaces;
3. Inverted rubbers, tacky or grippy, tend to have a greater difference in stickiness than CoF;
4. Non-inverted rubbers, shortpips or longpips, tend to have a greater difference in CoF than stickiness.
In another study by the same authors on the effect of humidity on the CoF of Feint Long III, Challenger Attack, Super Anti, and T05, using S40+, A40+ and G40+ balls, at 60% relative humidity(used in the previous paper), T05 and Sriver L show comparable CoF and stickiness.
JTTA has conducted a similar study on the CoF of various popular inverted tacky rubbers(Nittaku H3 and TG3, Butterfly Spinart...), grippy rubbers(T05, T64, Fastarc G-1...), and non-inverted shortpips(Flarestorm, Spectol, Moristo SP, Attack 8...) and longpips(Curl P-3 Soft, Feint Long III and Grass D.TecS).
In the static test, by pulling the rubber faced down horizontally atop 3 table tennis balls at 3 loads and velocities(140g@5m/s, 200g@7m/s, 240g@10m/s), they found that inverted rubbers exhibit 3 CoF patterns:
A. CoF stays relatively constant, like the dash sign -;
B. CoF decreases with increasing load and velocity, like the backward slash \;
C. CoF increases first but then decreases with increasing load and velocity, like the caret sign ^.
In the dynamic test, by shooting topspin and backspin balls on the rubber faced up horizontally at 2 spin rates(3000-4000rpm, 4000-5000rpm), they found that for both topspin and backspin balls:
1. Tacky rubbers tend to have a lower CoF than shortpips rubbers at both spin rates;
2. Tacky rubbers see a substantial increase in CoF at the higher spin rate;
3. Shortpips rubbers see only a moderate increase in CoF at the higher spin rate.
Then again, as I pointed out in my first post, the angular momentum of a spinning ball is just much lower than a swinging racket to overcome the tack and harder sponge, it's only natural for the CoF of tacky rubbers to be lower in that scenario. We need an experiment that tests with a swinging racket.
Sumitomo, the manufacturer behind the Mizuno Q series, has published experimental data on both inverted(tacky and grippy) and shortpips rubbers made with different formulas with a swinging racket.
All topsheets were paired with the same sponge at 50° Asker C on a Senkoh Super 95 S, and swung at a stationary ball at 14m/s with a 60° racket angle. The friction force was measured by pulling 3 table tennis balls with a total load of 20N at 300mm/min on a rubber faced up horizontally. The data show that:
1. Despite the highest CoF, tacky topsheets made with different types of tackifier produced less spin than a grippy topsheet with a lower CoF made with practically the same formula.
2. With slightly different formulae, grippy topsheets with a substantially lower CoF could produce more spin than grippy topsheets with a higher CoF.
3. With slightly different formulae, shortpips with a substantially lower CoF could produce comparable spin as grippy topsheets with a higher CoF.
The reason many folks get the illusion that tacky rubber spins better than grippy rubber at lower impact force when brushing comes from the fact that the tack makes it easier for players to apply tangential force without slipping, which is harder to achieve with grippy rubber. What they don't realize is that the force direction is already different there. With tacky rubber, you are applying more force in the tangential direction than in the normal direction when brushing. In other words, you're trading speed for spin. With grippy rubber, you have to apply more force in the normal direction to bite the ball and get the topsheet to stretch or risk slipping, but on the flip side, you get more speed, and in turn you get a lower spin/speed ratio. To remedy that and to facilitate brushing, grippy rubber tends to have a softer topsheet than tacky rubber.
That's why tacky rubber is superior when playing close to the table and mid-distance because it kills the incoming speed and spin, yet offers the player a greater range/gradation(more gears) of outgoing speed and spin, and subsequently gives the player more "control" when transitioning from serve/receive to 3rd/5th/2nd/4th ball attack to the rally.