2.1. Vinyl-Asbestos Characterization

The prevalent use of vinyl floors containing asbestos was in public buildings and popular housing. In this context, two types of vinyl from public buildings have been considered. In Figure 3, they are shown macroscopically. The green vinyl (F) on the left was laid in the 1990s and shows a flexible structure. The black vinyl (R) on the right was laid in the 1980s and shows a more rigid structure.

(a) Sample F—squared floor green tiles with white and black stripes, more flexible and in good condition (b) Sample R—squared floor black tiles with beige stripes, quite rigid and in fairly good condition.

The density of the two vinyl samples, in line with patent [2], was calculated using surface/volume ratio. The results obtained are shown in Table 4.

Density of two vinyl samples F (green and flexible) and R (black and rigid).

The evaluation of the presence of asbestos was carried out with two methodologies: a simple abrasion of the surface material utilizing a scalpel; a sample burning at 500 °C of a tile fragment followed by a reaction with HCl, to concentrate the asbestos fibers which are resistant to this temperature.

The quantity and dimension of the asbestos (Chrysotile) are different in the two vinyl tiles. Concerning the quantity evaluation, it is difficult due to a non-homogeneous distribution of Chrysotile in the vinyl tiles. For this reason, the quantity defined by M.D. 6/9/94 [4] (10–25%) has been considered. The dimensions were observed through SEM/EDS (scanning electron microscope/energy dispersion micro analytical system) analysis, and the spectrum identification was carried out following the International Standard ISO 14966 [20].

The simple abrasion of surface tile powder was analyzed with SEM/EDS; Figure 4 shows the spectrum obtained by analyzing the powder from vinyl F. The photo on the left shows how the fibers are completely incorporated within the vinyl matrix. The spectrum shows both of the elements that compose chrysotile, Mg and Si, where the Mg peak is greater than the Si peak; the spectrum also reports the elements that compose the vinyl matrix, Cl and Ca.

F sample SEM analysis. (a) Photo of incorporated fibers of chrysotile; (b) spectrum of chrysotile and vinyl chloride composition.

Figure 5 shows the same analysis, performed on the powder obtained from the vinyl sample R. In addition, in this case, the fibers are incorporated in the vinyl matrix; the spectrum confirms this aspect due to the presence of Mg and Si components of the chrysotile.

R sample SEM analysis. (a) Photo of incorporated fibers of chrysotile; (b) spectrum of chrysotile and vinyl chloride composition.

One feature that distinguishes asbestos, and which led to wide use in the past, is its stability at high temperatures. To obtain a higher concentration of asbestos sample from the vinyl, freeing the fibers, a burning treatment on a plate at 500 °C was carried out.

This procedure was used to better identify the fibers and to be able to measure them by SEM. This procedure is not possible with the simple scratching of the surface, as the fibers, in this case, remain incorporated in the matrix.

Figure 6 and Figure 7 show the free fibers obtained, respectively, from samples F and R. The measurements of the fibers of both samples are in line with the particle size dimension declared by Petry US Patent [2], that is, below 2 mm. A difference can also be observed between the particle size dimension of sample R and sample F: the older and more rigid sample R has smaller fiber sizes than sample F.

F sample SEM analysis. (a) Photo of free fibers of chrysotile with measurement values; (b) spectrum of chrysotile.

R sample SEM analysis. (a) Photo of free fibers of chrysotile with measurement values; (b) spectrum of chrysotile.