Desenvolvimento de novos compostos de borracha natural a partir da desvulcanização em extrusora com rosca dupla
Abstract
The present study investigated the utilization efficiency of an intermeshing
co-rotating twin-screw extruder (ICTSE) in the devulcanization of natural rubber
compounds (NR), evaluating the physical, chemical and mechanical characteristics
of these materials in each project step. Three accelerated compounds with different
sulfur concentrations were submitted to torque rheometry and vulcanized according
these results aiming the achievement of elastomers with different crosslinks
densities. The influences on the characteristics of the devulcanized material caused
by the variation of the extruder barrel temperature, screw rotation, thermoplastics
addition and material stiffness were evaluated. Thermogravimetric analysis (TGA),
differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), soluble
fraction extraction and crosslink density were performed, evaluating the
devulcanized compound. Horikx's theory was also used as an indicator of selective
crosslink cleavage, defining the compounds to be revulcanized for comparison with
the virgin pure material. The revulcanization was carried out with the mixture of the
devulcanized compound with the pure, in the proportions of 30/70 w/w, respectively,
and in the devulcanized compound singularly, with addition of complementary
vulcanization system in both cases. The mechanical, dynamic-mechanical and
crosslink density properties of the revulcanized compounds were characterized and
evaluated in relation to the properties of the pure compounds. The increase in the
concentration of uncrosslinked BN chains and the concentration of sulfur
compounds in the extruded samples was observed by thermal tests and
spectrocopy, together with the verification of a high level of devulcanization
percentage, according to Flory-Rehner, evidencing the regeneration of the natural
rubber existent. Also, satisfactory mechanical properties were found in the
revulcanized compounds, especially when using auxiliary thermoplastics, revealing
the great potential of ERDCI processing for the reuse of discarded BN compounds.