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

Abstract

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.

Statistical Design of Experiments: Study of Cross-Linking Process through the Phase-Resolved Photoacoustic Method as a Multivariable Response

“…Thus, each peak was catalogued in order to understand the relationship between peaks and the crosslinking process. 10,14 The condensation reaction mechanism involved in the cross-linking processes is considered as that shown in Figs. 1a and 1b.…”

“…Superimposed overtone intensities arising from the combinations of -OH, -CH 2 -, and -CH 3 groups had been previously located and studied by means of the photoacoustic spectra. It was done using a Gaussian fitting of the curves 12,14 and phase differences through the phaseresolved photoacoustic method. 13 By considering the condensation reaction (Fig.…”

“…It is worth emphasizing the importance of using the factorial design and the methodology of response surface when the design has just a few samplings 14 to be analyzed; the affirmation of the optimum point is more ra-tional when the design is drawn to have a wider sampling for both variables. A simple question that arises here is how one can assure that 5% of the catalyst is the ideal instead of 5.5% or 6.0% if in the sampling designed there are no such values for these catalyst percentages.…”

“…The experimental setup for the photoacoustic spectroscopy (PA) is described elsewhere. 3,12,14 In this paper, data were collected using a homemade photoacoustic configuration for the UV-VIS and mid-infrared regions. In this setup, a white light (Xe arc lamp, ORIEL 68820, 1000 W) passes through a monochromator (ORIEL 77250, 180 nm to 3800 nm).…”

Investigating the crosslinking effects on surface characteristics of vinyltrimethoxysilane‐grafted moisture‐cured low‐density polyethylene/ethylene vinyl acetate blend

“…In this step, moisture curing and crosslinking are carried out via hydrolysis of the methoxysilane (SiOCH 3 ) groups to form silanol (SiOH) structures, followed by condensation of the formed hydroxyl groups to produce siloxane structures (SiOSi). Water is produced in the latter reaction as by‐product . This reaction is often catalyzed by organo‐tin compounds such as dibutyltin dilaurate (DBTDL) …”