Electron‐beam irradiation of poly(vinyl chloride)/epoxidized natural rubber blends in presence of trimethylolpropane triacrylate

Abstract

Electron-beam initiated crosslinking of poly(vinyl chloride)/epoxidized natural rubber blends, which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20 -200 kGy) and concentrations of TMPTA (1-5 phr). The gel content increased with the irradiation dose and the TMPTA level, although the increase was marginal at higher doses and higher TMPTA levels. Blends containing 3-4 phr TMPTA achieved optimum crosslinking, which in effect caused the maximum tensile strength (TS) at a dose of 70 kGy. A further addition of TMPTA caused a decline in the TS above 40 kGy that was due to embrittlement, which is a consequence of excessive crosslinking and the breakdown of the network structure. The possible formation of a more open network as a result of the breakdown of the network structure was further confirmed by the modulus results. Dynamic mechanical analysis (tan ␦ curve) and scanning electron microscopy studies on samples irradiated at 0 and 200 kGy were undertaken in order to gain further evidence on the irradiationinduced crosslinking. The plasticizing effect of TMPTA prior to irradiation and the formation of microgels upon irradiation were also discussed.

Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene‐co‐vinyl acetate) and electron beam irradiation

“…This drop could be associated with the embrittlement of EVA caused by excessive formation of crosslinks above 100kGy irradiation dose. A similar observation was reported by Ratnam et al (2001d); while working on radiation induced crosslinking of polyvinyl chloride/epoxidised natural rubber blends. In the initial state of irradiation, larger network structure is formed through radiation induced crosslinking resulting in an increase of the strength.…”

“…On the contrary, EVA showed a distinct increase (18%) in tear strength up to 100kGy irradiation followed by a decrease beyond 100kGy irradiation dose. Such a drop in the tear strength at above 100kGy is in agreement with the observation on tensile strength in which EVA is believed to undergo embrittlement due to the occurrence of excessive radiation induced crosslinking at higher irradiation doses (Ratnam et al, 2001d, Sharif et al, 2000, Sujit et al, 1996, Dutta et al, 1996. Several authors have studied the effects of ionizing radiation (gamma or electron beam) on waste tire dust blends (Sonnier et al, 2006, Sonnier et al, 2008, Sonnier et al, 2007, Mészáros et al, 2012.…”

Caracterização físico-mecânica de filmes de borracha natural epoxidada curáveis em temperatura ambiente

“…Neste trabalho a composição ENR 5 apresenta-se a mais homogênea do que a ENR 10 e ENR 20. Para os filmes de ENR/TMP-SH o aumento do teor do agente de cura faz alargar o pico da tan δ [13] . Nas composições ENR 10 e ENR 20 o alargamento do pico sugere a existência de mais de uma fase [29] .…”

“…Além disso, na literatura é descrito que o grupo epóxido é o responsável pela interação da ENR, aumentando a compatibilidade entre carga-polímeros [7][8][9] ou em misturas físicas [10,11] , e também em sistemas contendo agente de reticulação e alta energia (radiação UV, feixe de elétrons, etc.) [12][13][14] .…”

“…O aumento da adição no teor de TMP-SH nas composições fez diminuir o grau de inchamento em tolueno das composições com ENR o que leva a um aumento no teor de gel, sendo um indicativo de formação de reticulações entre ENR e TMP-SH em função do teor do agente de cura [12,13] . Segundo Tangboriboonrat [25] um valor de grau de inchamento menor do que 500% pode corresponder a uma borracha reticulada.…”