Ultrasonic Devulcanization of Carbon Black Filled Polyurethane Rubber

Abstract

Following our success with the recycling of unfilled polyurethane rubber (PUR), an attempt was made to devulcanize carbon black (CB)-filled PUR. Although CB was added in various proportions, only samples with lower filler loading could be treated. Devulcanization experiments were carried out at various feed rates, gap sizes, and amplitudes in a grooved barrel as well as a coaxial reactor with ultrasonic attachments and the optimum processing conditions were determined. Gel fraction, crosslink density, and dynamic properties of the treated samples were determined. However, attempts to cure the 100% devulcanized samples obtained from the grooved barrel reactor failed possibly due to severe degradation of main chains and reduced polymer–filler interactions under ultrasound treatment. Hence the next plausible step was to prepare blends of the devulcanized and filled virgin vulcanizates. These blends were successfully cured and their mechanical properties were determined. It was found that blends containing 50% or higher amount of devulcanized rubber exhibited reasonable mechanical properties thereby proving that the application of ultrasound is a suitable method for the recycling of CB-filled PUR.

New Reclaiming Process of Thermoset Polyurethane Foam and Blending with Polyamide-12 and Thermoplastic Polyurethane

“…One factor limiting their widespread recycling is that unlike thermoplastics, they cannot be re-melted and re-molded once cured. Therefore, extensive research efforts have been directed toward polyurethane reclaiming by its decrosslinking using several methods such as mechanical, thermo-mechanical, cryomechanical, mechano-chemical, microwave and ultrasonic processes, providing properties similar to the raw materials [1][2][3][4][5][6][7][8][9][10]. The reclaimed materials can then be re-incorporated into the precursor polymer or can be used to produce blends and composites with other polymers [11][12][13].…”

Recycling of Waste Tyre into Silica-Rubber Compounds for Green Tyre Application

“…As a result, waste rubber creates serious environmental hazards [2]. So far, a number of different methods are introduced like mechanical [3][4][5][6], mechanochemical [7][8][9][10][11][12], microwave [13][14][15] and ultrasound [16,17] treatments. However, the desired level of devulcanization to regenerate the raw rubber has not been attained.…”

Reclaiming of waste guayule natural rubber vulcanizate—reclaim rubber for green tire applications: An approach for sustainable development

“…But ASTM STP 184A defines devulcanization as a combination of depolymerization, oxidation, and increased plasticity as they usually occur during the process of reclaiming. 12 A great number of research works on the devulcanization of waste tires have been published and depending on the process of devulcanization, it may be classified into different types such as mechanical, 13 –15 mechanochemical, 16 –19 thermochemical, 20 biological, 21,22 ultrasonic, 23,24 and microwave 25 –27 devulcanization process. Among all these different devulcanization processes, intensive research has been carried out through mechanochemical devulcanization.…”