Okunzuwa

This study investigates the influence of phenol-based oxidative discoloration on the raw rubber properties of natural rubber (Hevea brasiliensis). Three fresh latex samples namely samples A, B and C (control) were collected randomly on the Rubber field at the Rubber Research Institute, Benin City, Nigeria and processed. The discoloration was observed immediately after tapping, resulting from the oxidation of naturally occurring phenolic compounds present in the latex upon exposure to air. Evaluation of the three samples’ raw rubber properties - dirt content, volatile matter, ash content, nitrogen content, initial plasticity (P₀), plasticity after 30 minutes (P₃₀), and plasticity retention index (PRI) – were done and compared with the standard ISO procedures. Results showed that the phenol-oxidized samples A and B exhibited a slight increase in volatile matter (0.34–0.41%) and nitrogen content (0.47–0.56%), alongside a reduction in PRI values (76–82%) compared to the control but all three samples remained within the acceptable ISO acceptable range for the raw rubber properties. However, dirt (0.020.05%) and ash (0.39–0.43%) contents remained within the acceptable limits specified by ISO standards. These findings indicate that natural oxidative discoloration caused by phenolic compounds slightly reduces the oxidative stability and elasticity of raw rubber but does not significantly compromise its conformity to industrial quality standard