Effects of ultrasonic treatment on unfilled butadiene rubber

Abstract

The ultrasonic treatment of unfilled butadiene rubber (BR) gum with a grooved‐barrel ultrasonic reactor was carried out, leading to changes in the structure and physical properties. The ultrasonic treatment of BR gum led to gel formation, with the amount dependent on the amplitude. The rheological and mechanical properties of the ultrasonically treated samples and their vulcanizates were measured and compared with those of the virgin samples. Gel permeation chromatography measurements of the sol part of the virgin and the treated samples were carried out. Rheological property and molecular weight measurements indicated the creation of a branched structure and the occurrence of degradation in ultrasonically treated BR gum. Because of degradation, the tensile strength and Young's modulus of treated BR were lower than those of untreated BR, whereas the elongation at break was practically intact. Differential scanning calorimetry (DSC) curves at a high‐temperature range showed exothermic peaks with enthalpy reduction in the treated BR, indicating a decrease in the number of double bonds due to gel formation. DSC curves at a low‐temperature range indicated increased crystallinity in the treated samples. Competing reactions of gel formation, branching, and degradation occurred during the ultrasonic treatment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2959–2968, 2003

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part A: influence of devulcanization process

“…In general, it can be observed that the optimum cure time and scorch time, represented by t 90 and ts 1 respectively, were lower for samples with the highest exposure times to microwaves in one step as well as in multistep treatments. This behavior is characteristic of reclaimed rubber and it was observed by some other authors [14][15][16][17] , which probably happens due to the presence of residual curatives from the first vulcanization. The devulcanization process increases the freedom degree of the polymeric chains, accelerating the reaction with the increasing of the exposure time of the GTR to microwaves, possibly due to the great amount of effective shocks during the process.…”

Relationship among Vulcanization, Mechanical Properties and Morphology of Blends Containing Recycled EPDM

“…Finally, the residue was ground in a knife mill (Marconi, model MA 580, Piracicaba, SP, Brazil). The distribution of particle size was determined by granulometric analysis, according to American Society for Testing and Materials (ASTM) D5644-01, using the sieves with 20,25,28,35,48, and 65 mesh.…”

“…The results showed that this parameter decreased as the residue content increased in the blends. Such a reduction can be attributed to the presence of residual vulcanization additives related to the first vulcanization reaction, which is a characteristic behavior of recycled rubbers [25,[34][35][36]. According to Ismail et al [36], the residual accelerator can act as a sulphur donor, which speeds up the early stages of the vulcanization process and reduces the value of ts 1 .…”

Devulcanization of ground tire rubber: Physical and chemical changes after different microwave exposure times

“…However, there are methods that can be used to obtain recycled materials with enhanced properties, so that the rubber becomes processable and moldable. Once the rubber can flow, it can be revulcanized as the virgin rubber [5] or it can also be incorporated into thermoplastics to produce high toughness materials [6][7][8][9]. The technique known as devulcanization is used for regaining this fluidity.…”