Balancing the Properties of Aircraft Tire Tread Compounds by Experimental Design

(1)

Balancing the Properties of Aircraft Tire Treads by Experimental Design:

The Influence of ZnO and DPG Addition

in Hybrid Carbon Black-Silica Filled NR/BR Compounds

Indriasari

1,2

, Kaewsakul, W.

1

,Dierkes, W.K.

1

, Blume, A.

1

1.Elastomer Technology and Engineering, University of Twente, Drienerlolaan 5, Enschede 7522NB, The Netherlands 2. Agency for the Assessment and Application of Technology (BPPT), Indonesia

Email: i.indriasari@utwente.nl, indriasari@bppt.go.id

The research is financially supported by:

• Severe operation conditions of aircraft (AC) tires result in high heat generation and excessive tread wear.

BACKGROUND

Max. tread temperature: 160 - 310°C Severe tread wear

• Conventional AC tread compounds are based on natural rubber (NR) and carbon black (CB).

• Partial substitution of CB with silica (SI) might give the best of both worlds: low wear (abrasion resistance) and reduced hysteresis (tan delta).

• Optimizing of AC tire properties determined by:  Right choice of rubber ingredients

 Correct processing

Study the addition sequence of zinc oxide (ZnO) and 1,3 diphenyl guanidine (DPG) in hybrid CBSI filled NR/butadiene rubber (BR) compounds since it influences the

silanization efficiency, thus affects the final performance, e.g. in terms of mechanic and dynamic properties.

AIM OF THE PROJECT

APPROACH

The factorial design of experiment (DOE) was used with two categorical factors namely Z (ZnO) and D (DPG). Each factor has two levels: level 1 (I = first stage) and level 2 (F= final stage). I F I _F D Z

Run ZnO DPG Notification

1 I F ZIDF 2 F I ZFDI 3 I I ZIDI 4 F F ZFDF 5 I F ZIDF 6 I I ZIDI REFERENCE CB-50°C-130rpm-5min CB OPT

• Addition of ZnO in the first stage of mixing allows the reduction of silica network

formation resulting in lower Mooney viscosities.

• Cure rate index (CRI) decreased when ZnO and DPG were added in the first stage of

mixing due to deactivation of ZnO and DPG resulting from interaction with silanol groups on the surface of silica.

• The delta torque of the hybrid CBSI filled compounds do not differ significantly, so the

network formation is similar.

CONCLUSIONS

Curing behavior

• Early addition of ZnO in the mixing process results in better filler dispersion (lower

Payne effect).

• At 230°C, the tan delta values of compounds with ZnO added in the final stage of mixing

are the lowest due to high filler-polymer interaction as indicated by G’[100].

• The addition of DPG in the first stage of mixing has little influence on Payne effect and

tan delta.

• However, both properties of hybrid CBSI filled compounds are still higher compared to

the CB reference due to the different amount of CBSI (70 phr) needed to obtain the same hardness as the CB filled compound (55 phr).

• The ZnO and DPG addition sequence do not have a significant effect on the mechanical

properties of hybrid CBSi filled compounds, i.e. M300, TS, hardness, tear strength, abrasion resistance.

• The tear strength of hybrid CBSI filled compounds is higher, yet the abrasion resistance

is lower compared to the CB filled compound.

• The ZnO addition sequence allows to significantly influence processing, cure rate, Payne effect, as well as tan delta at high temperatures compared to the DPG

addition sequence.

• The best properties of hybrid CBSI filled compounds are achieved when ZnO is added in the final stage of mixing, and DPG is added in the first stage of mixing.

CB OPT CBSI-ZIDF CBSI-ZIDI CBSI-ZFDI CBSI-ZFDF

0 20 40 60 80 100 ML( 1+4 )1 00 o C 0 5 10 15 20 25 30 0 400 800 1200 1600 2000 CBSI-ZIDF CBSI-ZIDI CBSI-ZFDI CBSI-ZFDF CB-OPT Torq ue (d Nm) Time (seconds)

RESULTS AND DISCUSSION

Processing behavior

Dynamic properties

Mechanical properties

50 55 60 65 70 75 80 85 90 G'[0. 56]-G '[100] ( KP a) G'[0. 56] ( KP a) G'[0.56] I K M1 G'[100] G'[100] G'[0.56] G'[0.56]-G'[100] G'[100] KP a 500 600 700 800 900

0 20 40 60 80 100 120 M3 00 (M Pa), TS ( MPa) , Hard ne ss sh or e A, T ea r st re ng th (KN/m) , ARI (%) Modulus 300 (M300) Tensile strength (TS) Hardness shore A Tear strength

Abrasion resistance index (ARI)

80 100 120 140 160 180 200 220 240 0,1 0,2 0,3 0,4 0,5 CBSI-ZIDF CBSI-ZIDI CBSI-ZFDI CBSI-ZFDF CB-OPT tan de lta @ 20 Hz, 1% s tra in Temperature (oC)