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In this work, the photoacoustic method is employed to monitor the copolymer formation from ethylene vinyltrimethoxy silane and grafted vinyltrimethoxy silane on low-density polyethylene when cross-linked using water saturated vapour. Photoacoustic spectra at overtones of –CH2–, –CH3– and –OH showed that the cross-linking processes were more efficient when the samples were prepared at 80°C with the catalyst concentration in the range between 5% and 7%. Using different light modulation frequency procedure it was observed that –OH and –CH2– groupings were more concentrated near surface, showing a larger concentration gradient for –CH2– than –OH. In addition, the thermal diffusivity analysis did not present a tendency that could be used for understanding the cross-linking process, although, the average value of the product ρcp were 1.6 (J K cm−3) for the grafted polymer and 2.5 (J K cm−3) for the copolymer, respectively. It is suggested that grafted samples present a higher thermal conductivity.

In the present work, the rear photoacoustic signal technique is used to determine thermal properties of human nails. The aging process of the human nail is analyzed through its thermal diffusivity and specific heat and using these results, thermal conductivity and thermal effusivity is determined. The study in vitro of this natural polymer showed a minimum for thermal properties to age about 20 years and an increase and possible saturation of them for ages over 50 years. The minimum value found for thermal diffusivity was close to 10 · 10 )4 cm 2 s )1 with saturation near 18 · 10 )4 cm 2 s )1 . Thermal conductivity and effusivity presents the same behavior.

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