Caracterização térmica e reológica de borracha de pneu desvulcanizada por microondas

Abstract

Resumo: Borracha de pneu pós-consumo previamente particulada foi submetida a um tratamento em microondas, de forma a promover a quebra de suas ligações cruzadas, ou seja, sua desvulcanização. A influência das variáveis do processo, tais como tempo de exposição às microondas e número de etapas de tratamento, foi investigada. Após o tratamento, estes materiais foram caracterizados em termos de suas propriedades térmicas por calorimetria exploratória diferencial e reológicas por reometria capilar. Também foi feita extração de solúveis em soxhlet, para avaliar a quantidade de borracha que foi efetivamente desvulcanizada durante o tratamento por microondas. O processo de desvulcanização mostrou-se um método viável para produzir um material passível de ser moldado, de forma semelhante a uma borracha virgem. No entanto, em nenhuma condição de desvulcanização utilizada foi possível obter um material 100% solúvel, ou seja, totalmente desvulcanizado. A análise térmica sugere que ocorre um processo semelhante ao envelhecimento do material durante o tratamento com as microondas. Palavras-chave:Reciclagem, borracha, desvulcanização, microondas, borracha de pneu moída. Thermal and Rheological Characterization of Ground Tire Rubber Devulcanized by MicrowavesAbstract: Ground tire rubber was submitted to a microwaves treatment in order to promote its devulcanization, that is, the breaking of the crosslinks between the chains. The influence of the processing parameters, such as time of exposure to the microwaves and number of treatment steps, was investigated. After the treatment, the material was characterized in terms of its thermal, by DSC, dynamic-mechanical, by DMA and rheological, by capillary rheometry, properties. In addition, the extraction of soluble fractions was made in soxhlet, to evaluate the amount of rubber that effectively was devulcanized during the microwaves treatment. The devulcanization treatment showed to be a viable method to produce a material which can be molded, in a similar way to virgin rubber. However, the complete devulcanization of the material was not possible in any devulcanization condition used. The thermal analysis showed that significant changes in the chemical structure were induced when the material was exposed to the microwaves for long times.

Synthesis, thermal studies and conversion degree of dimethacrylate polymers using new non-toxic coinitiators

“…[16][17][18][19][20][21] In the study of these dimethacrylate resins it is important to understand their thermal behavior, thus Thermoanalytical techniques such as Simultaneous Thermogravimetric Analysis -Differential Thermal Analysis (TGA-DTA) and Differential Scanning Calorimetry (DSC) are used in order to determine their thermal stability, degradation steps, glass transition, crystalline transition, crystallization, melt, and polymer cure. [22][23][24][25][26][27][28] Another important point is to study the dimethacrylate monomers' conversion, using different initiators systems. The Mid Infrared Spectroscopy (MIR) is used to get this information, so that it is possible to measure which system is more advantageous.…”

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

“…The technique of devulcanization by microwaves is currently one of the most promising ones, based on the good properties of the devulcanized material and the possibility of high productivity. The process takes advantage of volumetric heating of the material by microwaves, promoting a more uniform heating than that achieved by traditional methods of heating, which depend on conduction and/or convection [3][4][5] . Materials react differently when exposed to an electromagnetic field, like the one generated by microwaves.…”

“…The ability to convert microwave energy into thermal energy depends on the magnitude of the dielectric loss of the material [6,7] . Therefore, in mixtures of materials, it is possible a selective heating of specific regions, a property that has been exploited in the processing of thermosets with mineral fillers [3][4][5] . Elastomers such as natural rubber (NR), styrene-butadiene rubber (SBR), and ethylene propylene diene monomer rubber (EPDM) have low microwaves absorption due to their non polar characteristic.…”

“…According to Scuracchio et al [3] , the technique of devulcanization by microwaves is able to generate a material with properties quite different from the original vulcanized rubber. Among the properties, the most remarkable is the ability to flow and to be remolded.…”

Evaluation of the Effect of the Incorporation of Rubber Tire Waste Particles on the Properties of PP, HIPS and PP/HIPS Matrices

“…Recycling is a good alternative for the elimination of postconsumer plastic, as it generates new materials with equal or better properties than the raw materials, using practical and, above all, inexpensive methods [5,6] . The reuse of rubber tire waste (RT) dispersed in a thermoplastic matrix provides the opportunity to design materials that can be recycled in the future.…”