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20 18 16 14 12 10 8 6 4 2 0

Sweep

Base formula KW

Base formula Temp

200 180 160 140 120 100 80 60 40 20 0

1

12

241

361

481

601

Rubber

½ Silica and

½ Silica and

Black and

Silane

Oil

Additives

Shown is the mixing curve from our 1600ml mixer. The normal fill factor of 70% (~1300g) is based on the gravity of the ingredients. Because at the start of the mix the bulk density is high a ram is used to force the materials into the mixing chamber. The mixing chamber is warmed and cooled with fluid at about 50C. The rubber is 1st added and then the liquid silane is added with ½ the silica. The process oil is then added with the rest of the silica, residue powders are swept back into the chamber and all the secondary additives are added. After the sweep the rpm is changed to try to maintain the temperature at about 180C. Not shown is the ram position which finally reaches bottom at the inflection point at 360 secs. The stock was found to be crumbly up to this time and it became smooth coherent mass after this time. The chemical reactions of the silane for hydrolysis and coupling with silica as well as distributing and dispersing the silica for maximum rubber interaction all takes place under these extreme conditions. Not shown are the 2+1 mixing curves but the object is to keep the temperature under better control and to improve the coupling and dispersion. It also enables more choices in when the various additives can be incorporated.

STP0260

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