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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Estudo do sistema N-Ciclohexil-2-Benzotiazol-Sulfenamida(CBS)/enxofre na vulcanização da borracha natural

Fagundes, Enio César Machado January 1999 (has links)
O comportamento elástico dos reticulados de borracha natural, NR, obtidos a partir da reação com enxofre e acelerador, CBS foi examinado. Estudou-se a cinética de reação através das curvas reométricas para amostras com diferentes razões de concentração acelerador/enxofre. Observou-se que a reação de vulcanização é de primeira ordem, enquanto a energia de ativação cresce com a quantidade de enxofre e se mantém praticamente constante com a quantidade de acelerador. As amostras foram vulcanizadas sob calor e pressão e submetidas a medidas de tensãodeformação. Detemúnou-se a densidade de reticulação a partir do módulo de Young e pela teoria de Mooney-Rivlin. Paralelamente, a densidade de reticulação foi também obtida a partir de medidas de inchamento, aplicando-se a teoria de Flory - Rehnner. Este estudo indicou que a densidade de reticulação é proporcional a concentração de acelerador e também de enxofre. Nas amostras submetidas a análise mecânico-dinâmica, avaliou-se a tangente de delta, observando-se a mesma independente do grau de reticulação, na freqüência avaliada, enquanto a Tg aumenta com o grau de reticulação. / The elastic behavior of natural rubber networks, NR, obtained by reaction with sulfur and accelerator, CBS, was investigated. The kinetics of the reaction was studied through the rheometric curves for samples with different rations of accelerator/sulfur. It was observed that the vulcanisation showed first order kinectics, while the activation energy increase with the amount of sulfur and it stays constant with the increase of accelerator. The samples were vulcanisated under heat and pressure and submitted the stress-strain measurements. The crosslinking densities was determined by Y oung module and by Mooney - Rivlin theory. The crosslinking densities was also obtained from swell measurements, applying the Flory- Rehnner theory. This study indicated that the crosslinking densities is proportional the accelerator and sulfur concentration. Samples were submitted the dynamic mechanical analysis. The delta tangent was evaluated being observed that it independent of the crosslinking degree, in the appraised frequency, while Tg increases with the crosslinking degree.
2

Estudo do sistema N-Ciclohexil-2-Benzotiazol-Sulfenamida(CBS)/enxofre na vulcanização da borracha natural

Fagundes, Enio César Machado January 1999 (has links)
O comportamento elástico dos reticulados de borracha natural, NR, obtidos a partir da reação com enxofre e acelerador, CBS foi examinado. Estudou-se a cinética de reação através das curvas reométricas para amostras com diferentes razões de concentração acelerador/enxofre. Observou-se que a reação de vulcanização é de primeira ordem, enquanto a energia de ativação cresce com a quantidade de enxofre e se mantém praticamente constante com a quantidade de acelerador. As amostras foram vulcanizadas sob calor e pressão e submetidas a medidas de tensãodeformação. Detemúnou-se a densidade de reticulação a partir do módulo de Young e pela teoria de Mooney-Rivlin. Paralelamente, a densidade de reticulação foi também obtida a partir de medidas de inchamento, aplicando-se a teoria de Flory - Rehnner. Este estudo indicou que a densidade de reticulação é proporcional a concentração de acelerador e também de enxofre. Nas amostras submetidas a análise mecânico-dinâmica, avaliou-se a tangente de delta, observando-se a mesma independente do grau de reticulação, na freqüência avaliada, enquanto a Tg aumenta com o grau de reticulação. / The elastic behavior of natural rubber networks, NR, obtained by reaction with sulfur and accelerator, CBS, was investigated. The kinetics of the reaction was studied through the rheometric curves for samples with different rations of accelerator/sulfur. It was observed that the vulcanisation showed first order kinectics, while the activation energy increase with the amount of sulfur and it stays constant with the increase of accelerator. The samples were vulcanisated under heat and pressure and submitted the stress-strain measurements. The crosslinking densities was determined by Y oung module and by Mooney - Rivlin theory. The crosslinking densities was also obtained from swell measurements, applying the Flory- Rehnner theory. This study indicated that the crosslinking densities is proportional the accelerator and sulfur concentration. Samples were submitted the dynamic mechanical analysis. The delta tangent was evaluated being observed that it independent of the crosslinking degree, in the appraised frequency, while Tg increases with the crosslinking degree.
3

Estudo do sistema N-Ciclohexil-2-Benzotiazol-Sulfenamida(CBS)/enxofre na vulcanização da borracha natural

Fagundes, Enio César Machado January 1999 (has links)
O comportamento elástico dos reticulados de borracha natural, NR, obtidos a partir da reação com enxofre e acelerador, CBS foi examinado. Estudou-se a cinética de reação através das curvas reométricas para amostras com diferentes razões de concentração acelerador/enxofre. Observou-se que a reação de vulcanização é de primeira ordem, enquanto a energia de ativação cresce com a quantidade de enxofre e se mantém praticamente constante com a quantidade de acelerador. As amostras foram vulcanizadas sob calor e pressão e submetidas a medidas de tensãodeformação. Detemúnou-se a densidade de reticulação a partir do módulo de Young e pela teoria de Mooney-Rivlin. Paralelamente, a densidade de reticulação foi também obtida a partir de medidas de inchamento, aplicando-se a teoria de Flory - Rehnner. Este estudo indicou que a densidade de reticulação é proporcional a concentração de acelerador e também de enxofre. Nas amostras submetidas a análise mecânico-dinâmica, avaliou-se a tangente de delta, observando-se a mesma independente do grau de reticulação, na freqüência avaliada, enquanto a Tg aumenta com o grau de reticulação. / The elastic behavior of natural rubber networks, NR, obtained by reaction with sulfur and accelerator, CBS, was investigated. The kinetics of the reaction was studied through the rheometric curves for samples with different rations of accelerator/sulfur. It was observed that the vulcanisation showed first order kinectics, while the activation energy increase with the amount of sulfur and it stays constant with the increase of accelerator. The samples were vulcanisated under heat and pressure and submitted the stress-strain measurements. The crosslinking densities was determined by Y oung module and by Mooney - Rivlin theory. The crosslinking densities was also obtained from swell measurements, applying the Flory- Rehnner theory. This study indicated that the crosslinking densities is proportional the accelerator and sulfur concentration. Samples were submitted the dynamic mechanical analysis. The delta tangent was evaluated being observed that it independent of the crosslinking degree, in the appraised frequency, while Tg increases with the crosslinking degree.
4

Comparação entre os intumescimentos de borracha natural e polibutadieno com alto teor 1,4-cis em solventes (n-octano, ciclo-hexano e esqualeno) e em soluções poliméricas / Comparison between the swellings of natural rubber and polybutadiene with higb CIS-1, 4-content in solvents (n-octane, cyclohexane and squalen) and in polymer solutions / Vergleich zwischen den quellungen von naturkautschuk und polybutãdien mit hohem CIS-1, 4-gehalt in lösungsmitteln (n-octan, cyclohexan und squalen) und in polymerlösungen

Ojeda, Telmo Francisco Manfron January 1984 (has links)
Naturkautschukproben wurden durch Gammastrahlung vernetzt (2,4,6 und 8 MRad Dosis). Dann wurden sie unter folgenden Bedingungen gequollen: a) in n-Octan, Cyclohexan und Squalen; b) in flüssigem Polybutadien (k = 1830 g/Mol; hoher cis- 1,4-Gehalt), bei 45°C; c) in Niedrigrmolekulargewichtpolybutadienlösungen (Mn = 1830 g/Mol; hoher cis-1,4-Gehalt) in n-Octan und Cyclohexan; d) in Hochmolekulargewichtpolybutadienlösungen (Mn= 1 75.000 g/Mol; hoher cis-l ,4-Gehalt) in n-Qctan und Cyclohexan; e) in Naturkautschuklösungen (h = 779.000 g/Mol) in Cyclohexan bei 25°C. Polybutadienproben wurden durch Gammastrahlung vemetzt (1, 5; 18 cnd 25 MRad Dosis) und unter folgenden Bendingungen gequollen: a) in n-Octan, Cyclohexan und Squalen. Falls nicht anders erwähnt,wurden die Proben bei 25, 35 und 45°C gequollen. AUS der Quellungsmessungen wurden die Wechselwirkungsparameter zwischen (vernetzten) Polymeren und Lösungsmitteln (oder flüssigem Polyrmeren das als Lösungsmittel fungiert) berechnet. Dazu wurde die Flory-Rehner'sche Gleichung verwendet. Der Einfluss von Temperatur und Polymerkonzentration im Gel auf den Flory-Huggins Parameter wurde untersucht. Die Verträglichkeit zwischen Naturkautschuk und polybutadien wurde auch durch den Wechselwirkungsparameter untersucht. Es wurde gezeigt, dass lineare Niedrigmolekulargewichtpolybutadienketten in die vernetzte Naturkautschukproben eindringen können, wenn das Molekulargewicht der linearen Ketten sehr niedriger als den Netzwerksparameter Mc des Netzwerks ist. Lineare Hochmolekulargewicht- Polybutadienketten und-Naturkautschukketten, im Gegenteil, können nicht in die vernetzte Naturkautschukproben eindringen, wenn ihr Molekulargewicht höher als Mc des Netzwerks ist. Je höher die Konzentration der äusseren Lösungen im linearen Naturkautschuk (hohes Molekulargewicht), desto geringer die Quellung der Naturkautschukproben gewesen ist. / Amostras de borracha natural foram reticuladas por meio de radiação gama (doses de 2, 4, 6 e 8 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esqualeno; b) em polibutadieno líquido (Mn=1830 g/mol; alto teor 1,4- cis) a 45°C; C) em solução de polibutadieno de baixo peso molecular (M,= 1830 g/mol; alto teor 1,4-cis) em n-octano e ciclo-hexano; d) em solução de polibutadieno de alto peso molecular (Mn= 175.000 g/rnol; alto teor 1,4-cis) emn-octano e ciclo-hexano ; e) em solução de borracha natural (Mn=779.000 g/mol) em ciclo- hexano, a 25°C. Amostras de polibutadieno (alto teor 1,4-cis) foram reticuladas por meio de radiação gama (doses de 1,s; 18 e 25 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esquaieno. Salvo quando mencionado em contrário, as amostras de borracha natural e de polibutadieno foram intumescidas nas temperaturas de 25, 35 e 45°C. A partir dos ensaios de intumescirnento acima mencionados, foram determinadas as solubilidades de borracha natural e de polibutadieno em n-octano, ciclo-hexano e esqualeno através dos parâmetros de Flory-Huggins, calculados com o emprego da equação de Flory-Rehner. Verificou-se a influência da temperatura e da concentração de polimero no gel sobre o valor do parâmetro de Flory-Huggins. Também através desse parâmetro procurou-se determinar a compatibilidade entre borracha natural e polibutadieno. Foi demonstrado que cadeias lineares de baixo peso molecular de polibutadieno conseguem penetrar em amostras reticuladas de borracha natural, quando o peso molecular das cadeias lineares for bem inferior ao do arco de rede Mc das amostras reticuladas. Cadeias lineares de polibutadieno e de borracha natural com peso molecular superior ao do arco de rede da borracha natural reticulada, entretanto, não conseguem penetrar no retículo. Quranto mais alta a concentração da solução externa em moléculas de alto peso molecular, tanto menor é o grau de intumescimento da amostra reticulada. / Samples of natural rubber were crosslinked by gamma radiation (2,4,6 and 8 MRad doses) and swollen: a) in n-octane, cyclohexane and squalen; b) in liquid polybutadiene (h = 1830 g/mol; high cis-1,4- content) by 45°C; c) in solution of low molecular weight polybutadiene (%= 1830 g/mol; high eis-1,4-content) in n-octane and cyclohexane; d) in solution of high molecular weight polybutadiene (h = 175.000 g/mol; high cis-1,4-content) in n-octane and cyclohexane; e ) in solution of natural rubber (Mn = 779.000 g/mol) in cyclohexane by 25QC. Samples of polybutadiene (high cis- 1 ,4-content) were crosslinked by gama radiation (1 "5; i 8 and 25 MRad doses) and swollen : a) i n n-octane, cyclohexane and squalen. Except weather mentioned otherwise, the samples of natural rubber and polybutadiene were swollen by 25, 35 and 45°C. From the swelling rneasurements over refered, the solubilities of natural rubber and polybutadiene in n-octane,cyclohexane and squalen were determined, through the Flory-Huggins parameters. These were calculated by the agplication oF the Flory-Rehner equation. The influentes of temperature and polymer concentration on the Flowy- Huggins parameter were investigated. The compatibility between natural rubber and polybutadiene was also investigated by means of the: Flory-Huqgins parameter. It was demonstrated that linear low molecular weight chains of polybutadiene can penetrate crosslinked samples of natural rubber, weather the molecular weight of the linear chains is much lower than the,network parameters Mc of the networks. Linear high molecular weight chains of polybutadiene and natural rubber, on the contrary, can not penetrate crosslinked samples of natural rubber, weather their molecular weight is higher than Mc of the networks. The higher the concentration of the solution outside the gel in high molecuiar weight chains, the lower was the degree of swelling of the crosslinked samples .
5

Comparação entre os intumescimentos de borracha natural e polibutadieno com alto teor 1,4-cis em solventes (n-octano, ciclo-hexano e esqualeno) e em soluções poliméricas / Comparison between the swellings of natural rubber and polybutadiene with higb CIS-1, 4-content in solvents (n-octane, cyclohexane and squalen) and in polymer solutions / Vergleich zwischen den quellungen von naturkautschuk und polybutãdien mit hohem CIS-1, 4-gehalt in lösungsmitteln (n-octan, cyclohexan und squalen) und in polymerlösungen

Ojeda, Telmo Francisco Manfron January 1984 (has links)
Naturkautschukproben wurden durch Gammastrahlung vernetzt (2,4,6 und 8 MRad Dosis). Dann wurden sie unter folgenden Bedingungen gequollen: a) in n-Octan, Cyclohexan und Squalen; b) in flüssigem Polybutadien (k = 1830 g/Mol; hoher cis- 1,4-Gehalt), bei 45°C; c) in Niedrigrmolekulargewichtpolybutadienlösungen (Mn = 1830 g/Mol; hoher cis-1,4-Gehalt) in n-Octan und Cyclohexan; d) in Hochmolekulargewichtpolybutadienlösungen (Mn= 1 75.000 g/Mol; hoher cis-l ,4-Gehalt) in n-Qctan und Cyclohexan; e) in Naturkautschuklösungen (h = 779.000 g/Mol) in Cyclohexan bei 25°C. Polybutadienproben wurden durch Gammastrahlung vemetzt (1, 5; 18 cnd 25 MRad Dosis) und unter folgenden Bendingungen gequollen: a) in n-Octan, Cyclohexan und Squalen. Falls nicht anders erwähnt,wurden die Proben bei 25, 35 und 45°C gequollen. AUS der Quellungsmessungen wurden die Wechselwirkungsparameter zwischen (vernetzten) Polymeren und Lösungsmitteln (oder flüssigem Polyrmeren das als Lösungsmittel fungiert) berechnet. Dazu wurde die Flory-Rehner'sche Gleichung verwendet. Der Einfluss von Temperatur und Polymerkonzentration im Gel auf den Flory-Huggins Parameter wurde untersucht. Die Verträglichkeit zwischen Naturkautschuk und polybutadien wurde auch durch den Wechselwirkungsparameter untersucht. Es wurde gezeigt, dass lineare Niedrigmolekulargewichtpolybutadienketten in die vernetzte Naturkautschukproben eindringen können, wenn das Molekulargewicht der linearen Ketten sehr niedriger als den Netzwerksparameter Mc des Netzwerks ist. Lineare Hochmolekulargewicht- Polybutadienketten und-Naturkautschukketten, im Gegenteil, können nicht in die vernetzte Naturkautschukproben eindringen, wenn ihr Molekulargewicht höher als Mc des Netzwerks ist. Je höher die Konzentration der äusseren Lösungen im linearen Naturkautschuk (hohes Molekulargewicht), desto geringer die Quellung der Naturkautschukproben gewesen ist. / Amostras de borracha natural foram reticuladas por meio de radiação gama (doses de 2, 4, 6 e 8 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esqualeno; b) em polibutadieno líquido (Mn=1830 g/mol; alto teor 1,4- cis) a 45°C; C) em solução de polibutadieno de baixo peso molecular (M,= 1830 g/mol; alto teor 1,4-cis) em n-octano e ciclo-hexano; d) em solução de polibutadieno de alto peso molecular (Mn= 175.000 g/rnol; alto teor 1,4-cis) emn-octano e ciclo-hexano ; e) em solução de borracha natural (Mn=779.000 g/mol) em ciclo- hexano, a 25°C. Amostras de polibutadieno (alto teor 1,4-cis) foram reticuladas por meio de radiação gama (doses de 1,s; 18 e 25 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esquaieno. Salvo quando mencionado em contrário, as amostras de borracha natural e de polibutadieno foram intumescidas nas temperaturas de 25, 35 e 45°C. A partir dos ensaios de intumescirnento acima mencionados, foram determinadas as solubilidades de borracha natural e de polibutadieno em n-octano, ciclo-hexano e esqualeno através dos parâmetros de Flory-Huggins, calculados com o emprego da equação de Flory-Rehner. Verificou-se a influência da temperatura e da concentração de polimero no gel sobre o valor do parâmetro de Flory-Huggins. Também através desse parâmetro procurou-se determinar a compatibilidade entre borracha natural e polibutadieno. Foi demonstrado que cadeias lineares de baixo peso molecular de polibutadieno conseguem penetrar em amostras reticuladas de borracha natural, quando o peso molecular das cadeias lineares for bem inferior ao do arco de rede Mc das amostras reticuladas. Cadeias lineares de polibutadieno e de borracha natural com peso molecular superior ao do arco de rede da borracha natural reticulada, entretanto, não conseguem penetrar no retículo. Quranto mais alta a concentração da solução externa em moléculas de alto peso molecular, tanto menor é o grau de intumescimento da amostra reticulada. / Samples of natural rubber were crosslinked by gamma radiation (2,4,6 and 8 MRad doses) and swollen: a) in n-octane, cyclohexane and squalen; b) in liquid polybutadiene (h = 1830 g/mol; high cis-1,4- content) by 45°C; c) in solution of low molecular weight polybutadiene (%= 1830 g/mol; high eis-1,4-content) in n-octane and cyclohexane; d) in solution of high molecular weight polybutadiene (h = 175.000 g/mol; high cis-1,4-content) in n-octane and cyclohexane; e ) in solution of natural rubber (Mn = 779.000 g/mol) in cyclohexane by 25QC. Samples of polybutadiene (high cis- 1 ,4-content) were crosslinked by gama radiation (1 "5; i 8 and 25 MRad doses) and swollen : a) i n n-octane, cyclohexane and squalen. Except weather mentioned otherwise, the samples of natural rubber and polybutadiene were swollen by 25, 35 and 45°C. From the swelling rneasurements over refered, the solubilities of natural rubber and polybutadiene in n-octane,cyclohexane and squalen were determined, through the Flory-Huggins parameters. These were calculated by the agplication oF the Flory-Rehner equation. The influentes of temperature and polymer concentration on the Flowy- Huggins parameter were investigated. The compatibility between natural rubber and polybutadiene was also investigated by means of the: Flory-Huqgins parameter. It was demonstrated that linear low molecular weight chains of polybutadiene can penetrate crosslinked samples of natural rubber, weather the molecular weight of the linear chains is much lower than the,network parameters Mc of the networks. Linear high molecular weight chains of polybutadiene and natural rubber, on the contrary, can not penetrate crosslinked samples of natural rubber, weather their molecular weight is higher than Mc of the networks. The higher the concentration of the solution outside the gel in high molecuiar weight chains, the lower was the degree of swelling of the crosslinked samples .
6

Comparação entre os intumescimentos de borracha natural e polibutadieno com alto teor 1,4-cis em solventes (n-octano, ciclo-hexano e esqualeno) e em soluções poliméricas / Comparison between the swellings of natural rubber and polybutadiene with higb CIS-1, 4-content in solvents (n-octane, cyclohexane and squalen) and in polymer solutions / Vergleich zwischen den quellungen von naturkautschuk und polybutãdien mit hohem CIS-1, 4-gehalt in lösungsmitteln (n-octan, cyclohexan und squalen) und in polymerlösungen

Ojeda, Telmo Francisco Manfron January 1984 (has links)
Naturkautschukproben wurden durch Gammastrahlung vernetzt (2,4,6 und 8 MRad Dosis). Dann wurden sie unter folgenden Bedingungen gequollen: a) in n-Octan, Cyclohexan und Squalen; b) in flüssigem Polybutadien (k = 1830 g/Mol; hoher cis- 1,4-Gehalt), bei 45°C; c) in Niedrigrmolekulargewichtpolybutadienlösungen (Mn = 1830 g/Mol; hoher cis-1,4-Gehalt) in n-Octan und Cyclohexan; d) in Hochmolekulargewichtpolybutadienlösungen (Mn= 1 75.000 g/Mol; hoher cis-l ,4-Gehalt) in n-Qctan und Cyclohexan; e) in Naturkautschuklösungen (h = 779.000 g/Mol) in Cyclohexan bei 25°C. Polybutadienproben wurden durch Gammastrahlung vemetzt (1, 5; 18 cnd 25 MRad Dosis) und unter folgenden Bendingungen gequollen: a) in n-Octan, Cyclohexan und Squalen. Falls nicht anders erwähnt,wurden die Proben bei 25, 35 und 45°C gequollen. AUS der Quellungsmessungen wurden die Wechselwirkungsparameter zwischen (vernetzten) Polymeren und Lösungsmitteln (oder flüssigem Polyrmeren das als Lösungsmittel fungiert) berechnet. Dazu wurde die Flory-Rehner'sche Gleichung verwendet. Der Einfluss von Temperatur und Polymerkonzentration im Gel auf den Flory-Huggins Parameter wurde untersucht. Die Verträglichkeit zwischen Naturkautschuk und polybutadien wurde auch durch den Wechselwirkungsparameter untersucht. Es wurde gezeigt, dass lineare Niedrigmolekulargewichtpolybutadienketten in die vernetzte Naturkautschukproben eindringen können, wenn das Molekulargewicht der linearen Ketten sehr niedriger als den Netzwerksparameter Mc des Netzwerks ist. Lineare Hochmolekulargewicht- Polybutadienketten und-Naturkautschukketten, im Gegenteil, können nicht in die vernetzte Naturkautschukproben eindringen, wenn ihr Molekulargewicht höher als Mc des Netzwerks ist. Je höher die Konzentration der äusseren Lösungen im linearen Naturkautschuk (hohes Molekulargewicht), desto geringer die Quellung der Naturkautschukproben gewesen ist. / Amostras de borracha natural foram reticuladas por meio de radiação gama (doses de 2, 4, 6 e 8 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esqualeno; b) em polibutadieno líquido (Mn=1830 g/mol; alto teor 1,4- cis) a 45°C; C) em solução de polibutadieno de baixo peso molecular (M,= 1830 g/mol; alto teor 1,4-cis) em n-octano e ciclo-hexano; d) em solução de polibutadieno de alto peso molecular (Mn= 175.000 g/rnol; alto teor 1,4-cis) emn-octano e ciclo-hexano ; e) em solução de borracha natural (Mn=779.000 g/mol) em ciclo- hexano, a 25°C. Amostras de polibutadieno (alto teor 1,4-cis) foram reticuladas por meio de radiação gama (doses de 1,s; 18 e 25 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esquaieno. Salvo quando mencionado em contrário, as amostras de borracha natural e de polibutadieno foram intumescidas nas temperaturas de 25, 35 e 45°C. A partir dos ensaios de intumescirnento acima mencionados, foram determinadas as solubilidades de borracha natural e de polibutadieno em n-octano, ciclo-hexano e esqualeno através dos parâmetros de Flory-Huggins, calculados com o emprego da equação de Flory-Rehner. Verificou-se a influência da temperatura e da concentração de polimero no gel sobre o valor do parâmetro de Flory-Huggins. Também através desse parâmetro procurou-se determinar a compatibilidade entre borracha natural e polibutadieno. Foi demonstrado que cadeias lineares de baixo peso molecular de polibutadieno conseguem penetrar em amostras reticuladas de borracha natural, quando o peso molecular das cadeias lineares for bem inferior ao do arco de rede Mc das amostras reticuladas. Cadeias lineares de polibutadieno e de borracha natural com peso molecular superior ao do arco de rede da borracha natural reticulada, entretanto, não conseguem penetrar no retículo. Quranto mais alta a concentração da solução externa em moléculas de alto peso molecular, tanto menor é o grau de intumescimento da amostra reticulada. / Samples of natural rubber were crosslinked by gamma radiation (2,4,6 and 8 MRad doses) and swollen: a) in n-octane, cyclohexane and squalen; b) in liquid polybutadiene (h = 1830 g/mol; high cis-1,4- content) by 45°C; c) in solution of low molecular weight polybutadiene (%= 1830 g/mol; high eis-1,4-content) in n-octane and cyclohexane; d) in solution of high molecular weight polybutadiene (h = 175.000 g/mol; high cis-1,4-content) in n-octane and cyclohexane; e ) in solution of natural rubber (Mn = 779.000 g/mol) in cyclohexane by 25QC. Samples of polybutadiene (high cis- 1 ,4-content) were crosslinked by gama radiation (1 "5; i 8 and 25 MRad doses) and swollen : a) i n n-octane, cyclohexane and squalen. Except weather mentioned otherwise, the samples of natural rubber and polybutadiene were swollen by 25, 35 and 45°C. From the swelling rneasurements over refered, the solubilities of natural rubber and polybutadiene in n-octane,cyclohexane and squalen were determined, through the Flory-Huggins parameters. These were calculated by the agplication oF the Flory-Rehner equation. The influentes of temperature and polymer concentration on the Flowy- Huggins parameter were investigated. The compatibility between natural rubber and polybutadiene was also investigated by means of the: Flory-Huqgins parameter. It was demonstrated that linear low molecular weight chains of polybutadiene can penetrate crosslinked samples of natural rubber, weather the molecular weight of the linear chains is much lower than the,network parameters Mc of the networks. Linear high molecular weight chains of polybutadiene and natural rubber, on the contrary, can not penetrate crosslinked samples of natural rubber, weather their molecular weight is higher than Mc of the networks. The higher the concentration of the solution outside the gel in high molecuiar weight chains, the lower was the degree of swelling of the crosslinked samples .

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