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Poly(ethylene terephtalate), PET, can be modified with N,N-dimethylacrylamide to obtain a better incorporation of disperse dye (Disperse Blue 79). Minimal variations in the decomposition at 10% level, melting, and glass transition temperatures, show that the thermal stability of modified PET films does not change when compared to nonmodified PET. The atomic force images show nanopeaks formation on the surface due to the modification. Modified PET films show a decrease in the contact angle and then, an increase in the superficial tension measurements, when compared to the value of 37 Ϯ 1 dynes ⅐ cm Ϫ1 (nonmodified), with values liying in the range of 42-46 Ϯ 0.5 dynes ⅐ cm Ϫ1 . The data obtained by photoacoustic spectroscopy (PAS) for dyed PET films show a dye peak at 580 nm. The data analysis of the peak area show that PET films modified with N,N-dimethylacrylamide for 15 min at 85°C, dyed for 6 h at 85°C with a dye concentration of 0.333 g/L, incorporate three times more dye than the nonmodified films dyed in the same conditions. By the data obtained from PAS, it was possible to calculate the depth profile of dyeing with values around 54 m. Factorial analyses show that the dyeing time was the most important variable. The major amount of incorporated dye was obtained by the following combination of variables: temperature and time of modifier treatment were, respectively, 72.5°C and 15 min; time and temperature of dyeing were, respectively, 90°C and 195 min for a dye concentration of 0.133 g/L.

http://dx.doi.org/10.5007/2175-7941.2016v33n3p896 Este artigo trata de uma experiência didática, como proposta do PIBID de Física, de Porto Velho/RO, realizada numa Escola Pública da rede estadual de ensino, para alunos do 1º Ano do Ensino Médio. Neste trabalho analisa-se a viabilidade de se ensinar Física com base numa sequência didática alicerçada na aplicação diversificada de tirinhas e inspirada nos ideais construtivistas, com foco na participação do aluno, objetivando-se a Aprendizagem Significativa. As tirinhas foram usadas como organizadores prévios, como instigadoras do raciocínio e da criatividade em algumas etapas. Também são aproveitadas para se promover a diferenciação progressiva e a reconciliação integradora. A avaliação da metodologia revelou satisfação dos alunos com as atividades, bem como mostrou um maior desempenho em relação às outras turmas que não participaram deste projeto. A atividade culminou na produção de tirinhas por parte dos próprios alunos, reunidos em grupos, para facilitar uma possível troca de conhecimentos e experiências. Os resultados mostraram que é possível tirar proveito do uso das tirinhas e Histórias em Quadrinhos (HQs) nas aulas de ciências, pois são estratégias que permitem um planejamento de aula capaz de envolver os alunos, facilitando um ensino que leve à aprendizagem eficaz, por servir de ponte entre a realidade do aluno e os conceitos científicos ensinados.

Poly(ethylene terephtalate), PET, can be modified with N,N‐dimethylacrylamide to obtain a better incorporation of disperse dye (Disperse Blue 79). Minimal variations in the decomposition at 10% level, melting, and glass transition temperatures, show that the thermal stability of modified PET films does not change when compared to nonmodified PET. The atomic force images show nanopeaks formation on the surface due to the modification. Modified PET films show a decrease in the contact angle and then, an increase in the superficial tension measurements, when compared to the value of 37 ± 1 dynes · cm−1(nonmodified), with values liying in the range of 42–46 ± 0.5 dynes · cm−1. The data obtained by photoacoustic spectroscopy (PAS) for dyed PET films show a dye peak at 580 nm. The data analysis of the peak area show that PET films modified with N,N‐dimethylacrylamide for 15 min at 85°C, dyed for 6 h at 85°C with a dye concentration of 0.333 g/L, incorporate three times more dye than the nonmodified films dyed in the same conditions. By the data obtained from PAS, it was possible to calculate the depth profile of dyeing with values around 54 μm. Factorial analyses show that the dyeing time was the most important variable. The major amount of incorporated dye was obtained by the following combination of variables: temperature and time of modifier treatment were, respectively, 72.5°C and 15 min; time and temperature of dyeing were, respectively, 90°C and 195 min for a dye concentration of 0.133 g/L. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 269–282, 2000

Photoacoustic (PA) spectroscopy was applied to study the dyeing process in poly(ethylene terephthalate) films and fibers when supercritical (SC) pressure of CO2 is used. The samples were prepared according to a factorial design having four variables in two levels. They were dyed in red or blue. Following the PA intensity as a variable of response, it was applied an algorithm to take into account the effects of the dyeing variable. The results show that treatment and time were the more influent for blue dyed films and fibers. In contrast, time and temperature were more effective for red films. Depth penetration of the red dye shows saturation near 60 μm with a characteristic time of 30 min. Overall, the results presented CO2 pressure as the less effective variable and the SC–CO2 dyeing method being more effective if compared to conventional bath.

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In this work we report thermal diffusivity and specific heat measurements in N,N-dimethylacrylamide modified poly (ethylene terephthalate) (PET) films for incorporating the dye blue Samaron HGS. These thermophysical properties were studied by changing the sample preparation conditions, such as the temperature and time of N,N-dimethylacrylamide treatment, and the time and temperature of dyeing. The results showed that the heat conduction was improved when the PET film was dyed at a temperature below the glass transition (T<70 °C). On the other hand the thermal diffusivity decreased for samples dyed at T>70 °C. This behaviour can be attributed to microstructure changes in the polymer chains, as shown by the change in the amorphous/crystalline ratio, observed in the x-ray diffraction data.