Analysis of thermally aged adhesion specimen between precured and uncured rubber sheets

Retreading of tire is closely related with adhesion between precured and uncured rubber sheets. Adhesion specimens between precured and uncured rubber sheets of BR and NR were prepared and thermally aged at 90 °C for 3 days. Organic materials remained in the adhesion sheets were extracted with THF and analyzed using gas chromatography/mass spectrometry (GC/MS). Elemental sulfur (S8), mercaptobenzothiazole (MBT), antidegradants, and fatty acids were detected as major organic materials remained in the adhesion sheets. Amounts of the organic materials were reduced by the thermal aging and varied with the adhesion specimens of BR/BR, NR/NR, BR/NR, and NR/BR as the precured and uncured rubber sheets. Decrements of the S8, MBT, and fatty acids in the NR sheet were larger than in the BR one due to the faster cure characteristics of NR. Changes of the adhesion forces and crosslink densities by the thermal aging were measured. Adhesion force of only the precured BR/uncured NR specimen by the thermal aging was enhanced whereas those of the other specimens were reduced. This was explained with the crosslink density changes and migration of the organic materials through the interface of the adhesion specimen.