Photoacoustic study of cross-linking process in grafted polymer and copolymer based on ethylene and vinyltrimethoxy silane

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.