Post-harvest maturation of Hevea brasiliensis latex coagula: ranking of the key drivers of the mesostructure and physical properties of natural rubber

The coagula derived from Hevea latex are the main raw material for block natural rubber production, especially for the two most commercialized grades (TSR10 and TSR20). The properties and mesostructure of dry natural rubber depend on several factors during coagula maturation. This work investigated an experimental design allowing concomitant control of several factors during maturation of cup coagula, namely, temperature, relative humidity, atmosphere, vertical weight, coagulation conditions, clone, and maturation duration. For each combination of factors, several indicators were measured. They dealt with the coagula (thickness, DRCcoag), with the dry rubber (physical properties (P0, PRI, ASHT), and the mesostructure (Gel>1µ, Mn, Mw, Mz). Statistical treatment of the results (recursive partition) led to a hierarchical ranking of factors for each measured indicator. The first-ranked parameter was coagulation mode followed by genotype (clone) or maturation duration, temperature, or weight application. The provided identification of the most important drivers occurring during coagula maturation could allow improvements of the post-harvest operational handling aiming at a better control of the variability of produced natural rubber properties.