3.4. Swelling behavior
All the composites had a rapid weight gain during the first 3 h in toluene, but then the sorption rate decreased reaching a plateau (Fig. 6) (swelling curves of composites containing 10 and 20 phr of waste-derived fillers are not shown). Variations of swelling ratio at equilibrium and crosslink density were observed among the different guayule rubber compounds (Table 3). Composites containing 5 phr of waste-derived fillers had very similar swelling behavior to composites containing only carbon black.