Blending, curing and reinforcement of NR/BR/EPDM compounds for tire sidewall applications
Hongmei Zhang, Elastomer Technology & Engineering, University Twente
Tire sidewalls generally consist of blends of natural rubber (NR) and butadiene rubber (BR), containing a high concentration of antiozonants to provide ozone resistance. However, antiozonants like N-(1,3-dimethylbutyl)-N
Cross-linking of saturated elastomers using DI-azides
Agata Zielinska, Elastomer Technology & Engineering, University Twente
The main advantage of main chain saturated elastomers, such as EPM and EPDM, over their unsaturated counter-parts is their superior stability against oxygen, ozone and heat. A consequent disadvantage of the absence of unsaturation is their lack of reactivity. Saturated elastomers are reactive only under very specific conditions and towards a very limited number of reactions, what causes problems to crosslink this type of rubber. The common way to overcome the low reactivity is by performing free-radical reactions initiated by peroxides. This reaction, however, suffer from several disadvantages, the main ones being low efficiency and the occurrence of side reactions, such as the degradation of polymer chains. Azides are known as a class of organic compounds that are reactive towards alkanes. Hence, it is interesting to study the performance of di-azides in crosslinking saturated elastomers. The paper covers the synthesis of molecules with two azide-functionalities and their ability to crosslink saturated EPM-rubber. A variety of azide-types has been investigated: alkyl azides (R-N3), aromatic azides (R-C6H4-N3), azidoformates (R-O-C(O)-N3) and sulphonyl azides (R-SO2-N3). The properties of EPM vulcanized with di-sulphonyl azide or azidoformates compare favourably with these of peroxide-cured EPM. Some di-azide activity is consumed by oil plasticizers, but to a similar amount as for peroxide/co-agent combinations. Di-azide cured EPM has greatly improved mould-release properties relative to peroxide/co-agent cross-linked EPM.
De beleving van rubber
Prof. Dr. Ir. Jacques W.M. Noordermeer, Elastomer Technology and Engineering, University Twente
Plasma polymerization of acetylene and thiophene onto silica-AN alternative to improve the reinforcement of silica in S_SBR and EPDM
Mukund Tiwari, Elastomer Technology & Engineering, University Twente & Teijin Aramid
Filler dispersion is a critical factor for the final properties of filled rubber compounds. Silica has a high density of silanol groups on the surface, which leads to flocculation and a poor filler dispersion in a rubber matrix. The hydrophobation of the silica surface by plasma-polymerization is one possibility to improve the dispersion in different polymers, without affecting the bulk properties of the filler. The surface characteristics of silica were modified by plasma-thiophene and -acetylene film deposition. The plasma-coated fillers were blended with S-SBR and EPDM, and their influence on the final vulcanizate properties was compared with untreated silica and silanized silica filled polymers. The results show a lower degree of flocculation for plasma
Practical and theoretical study of solubility of curatives in SBR, NBR and EPDM rubber
Rui Guo, Elastomer Technology & Engineering, University Twente
The distribution and dispersion of curatives (curing agents and accelerators) in rubber blends is related to their solubility in the different rubber phases. Therefore, the knowledge of their solubility is beneficial for the prediction of the performance of rubber blends. In this study the solubility of sulphur and several accelerators: N-cyclohexylbenzothiazole-2-sulphenamide (CBS),N-dicyclohexylbenzothiazole- 2-sulphenamide (DCBS), and 2-mercaptobenzothiazole (MBT) is measured in slightly with dicumyl-peroxide vulcanised Styrene-Butadiene rubber (SBR), Acrylonitrile- Butadiene rubber (NBR) and Ethylene-Propylene-Diene rubber (EPDM) at room temperature and at 60oC. The experimental results can be correlated to the calculated solubility parameters , as determined using the method of Hoftijzer and van Krevelen. Results of are used to judge the solubility of curatives in a specific component in blends of different rubbers.
The effect of DPG on silane chemistry of silica in rubber processing
Satoshi Mihara, Elastomer Technology & Engineering, University Twente & Yokohama Rubber Co.
From the environmental point of view, silica is one of the most important fillers in tire rubber compounding. In silica-filled rubber compounds, large polarity differences between the filler and the polymers are present. Therefore, the silica-silica interaction which has a negative effect on the physical properties of silica-filled rubber, takes place. A silane coupling agent is generally used in silica-filled rubber in order to reduce the polarity difference between filler and polymer. However, the chemistry of silane coupling during rubber processing is complicated. 1,3-diphenylguanidine (DPG), used as a secondary accelerator, has an important function in silica-filled tire rubber. In the present study, the focus is on the effect of DPG on the silane chemistry during processing.