filler-filler interaction VS. filler-rubber interaction IN Tire COM. 1

[joysop]

Dear memebers,

I have 2 questions to ask you.

1. In Tire tread compound, is a filler-filler interaction related with tread's wet traction properties? True? Why & why not?

2. What about a filler-rbber interaction? Has it certain relationship with the rolling resistance? True? Why & why not?

From my knowledge, the silica compound with silane coupling agent reduces filler-filler interaction and increases filler-rubber interaction.

Thanks in advance.

 

[GrahamBennett]

Joysop,

You are asking two very pertinent questions, neither of which I can answer directly. Both of these have tasked many scientists' brains for many years and the subsequent literature base is very wide. I suggest you search on-line for technical papers published by S. Wolff and other workers in this field. I think that Degussa (and possibly Rhein Chemie) publishes technical papers on its website too.

 

[joysop]

Thank you for your kind reply,

It's not that simple as I expected.
But I want to simplify two crucial interactions with tire performance.

I've already reviewed many papers and technical document.
It's hard for me to go into the conclusion.
I like simplicity itself even though it's very complicated matters.

BYW, I'll research it more with your recommandation.

 

[joysop]

Dear GrahamBennett,

My conclusion is so simple that I'm a little bit disappointed.
It's as the following.

Main contributor Sub-contributor
Wet traction Tg of rubber rubber-filler inter.
Rolling resist. rubber-filler inter. Tg of rubber
Wear Tg of rubber thermal degradibility

What do you think about my conclusion?

 

[GrahamBennett]

A good summary.

 

[joysop]

Graham, how does so called the filler-filler interaction effect on tyre performance?

 

[GrahamBennett]

This is something I always get confused about. I think (could be wrong) that filler-filler interactions are bad for wear rates.

 

[joysop]

I've researched on the issue.
Filler-filler interactions reinforce rubber properties, especially modulus.
If its interactions are high, rubber modulus at low strain becomes increased by so call 'Payne-effect'.

But I don't know about how high modulus at low strain contrubutes on tire performance.

& why do you think filler-filler interactions are bad for wear rates? High interactions mean high wear rates?

 

[GrahamBennett]

Joysop. Sorry I haven't got back to you before now but I've been researching this for you. Polymer-filler interactions are very important for wear rates and rolling resistance. The stronger the bond (i.e chemical covalent bonds) between the polymer and the filler, the better the wear rate and rolling resistance will be. Filler-filler interactions are, as you stated, of secondary importance because the bonds between them tend to be either weak chemical or physical bonds. In any case, the Payne effect will have effectively disappeared once a tyre has rolled through about 10 rotations.

 

[joysop]

Graham, It's very very nice for me to get your explanations.
I must have to thank you first for researching the matters for me.

But a silica compound (silia/silane coupler/SSBR) gives poor wear resistance, even though it has a strong filler-rubber interaction. So it would be said that a filler-rubber interacton affects only rolling resistance. I mean it plays a major role in rolling resistance. According to my conclusion, Tg is a crucial element in wear resistance. Lower Tg, better wear properties. But NR is the exception. NR has a poor wear property although its Tg is almost the lowest among synthetic rubbers. It's, I imply, because NR's not thermally stable respectively compared with other rubbers.

I've thought that you already lose the intersets in this matter. But it was not. Thank you again, Graham. I've been learning a lot from you.

 

[GrahamBennett]

You're welcome, I'm glad to be of help. I agree NR is poor for wear which is why it is usually blended with BR (approx 70NR/30BR). Silica/silane/SSBR/BR compounds have good wear resistance compared to the carbon black equivalents in my experience. Lower Tg = higher cis content (ie the vinyl content is low) is why you get better wear resistance.

 

[joysop]

The lower Tg is, the better wear resistance.

It can be simply expalained by the following equation.

Tg=E"/E'=(loss modulus/storage modulus)

Higher Tg means higher E" or lower E' from the equation.
That's why higher Tg= higher E"= higher hysterisis= higher heat build up= lower rebound= higher wet skid resistance.
On the contrary, lower Tg= higher E'= lower hysterisis= lower heat build up= higher rebound(=lower rolling resistance)= lower wet skid resist.

Hegher wet skid resistance means that the unit area a tire contacts the road is high causeing high wear. So, higher Tg= higher wet skid resistance= lower wear resistance.

It could be concluded that every factors which can increase Tg increase wet traction and decrease wear resistance and also decrease rolling resistance.

Graham, what about Silica/Silane/ESBR/BR compared with SSBR equivalent in terms of rolling resistance, wet traction and wear resistance?

 

[GrahamBennett]

Sorry - can't help you with that one.

 

[joysop]

I found that Silica/Silane/ESBR gives lower rolling resistance compared with Carbon Black equivalent.