Water-repellent Products Research Articles

Basic methodology for the assessment and selection of water-repellent treatments applied on carbonatic materials

In this paper, a basic methodology to assess and select water-repellent treatments applied on carbonatic rocks has been carried out. In order to characterize the substratum—a biosparitic limestone—petrological, mineralogical, chemical and petrophysical properties have been determined. Ten water-repellent products have been applied, selected according to their frequent use in the conservation of stone and to their compositional variety: organic, organosilicic and inorganic products, soluble both in organic solvents and in water. In order to evaluate the effectiveness of the treatments, color determination, water–stone contact angle and water-vapor permeability were carried out. The penetration depth of the treatments into the stone, and their distribution within, were studied through scanning electron microscopy. Conclusions obtained are that treatment efficiency is higher, the higher its capacity to coat the walls of the porous system; treatment penetration in the stone, which depends much more on rock porous system than on pore volume, increase effectiveness but is not as significant as its filming capacity. Best results for carbonatic materials analyzed were obtained from siloxane-based compounds, on organic solvent.

Influence of water-repellent treatment on the properties lime and lime pozzolan mortars

The influence that water-repellent products can have on physical and micro-structural properties of lime mortars, and lime plus pozzolan mortars has been studied. Three water repellent products have been used. Mixes of the previously mentioned three water repellents plus a biocide product were also applied. Treatments make the total porosity and saturation coefficient of both mortars to decrease, while colorimetric coordinates bear little alteration. All treatments with water repellent products provided mortars with a hydrophobic property index close to 100%. Durability of such mortars has been also studied: salt crystallization test, frost-thaw and dry-wet cycles, as well as ultraviolet radiation test were carried out. Relationship between mortars behavior and their porosity and saturation coefficient were found.

A SYSTEM TO SIMULATE POLLUTED ATMOSPHERES AND ITS APPLICATION TO THE STUDY OF STONES USED IN ANDALUSIAN CATHEDRALS AND OF TREATMENT PRODUCTS

One of the main problems affecting monuments today is the effect of atmospheric pollution on their materials. From this arises the need to develop test methods to evaluate these effects, on the original materials (to define weathering mechanisms), on new materials for restoration and on treatment products to be applied. An installation has been designed and developed that allows the simulation of polluted atmospheres (with several pollutants) and other climatic conditions. The response of the system is studied when simulating specific conditions, by submitting samples of stone used in important Andalusian monuments, treated with various water-repellent products, to an accelerated weathering test with a sulphur dioxide atmosphere and variable humidity conditions. The installation is of a modular type and can be divided into 10 sections. In sections 1 and 2 the conditioning of air used to generate the simulated atmosphere is carried out: the air is first dried with 96% sulphuric acid and then cleansed of solid particles, sulphuric acid vapour and organic compounds. In sections 3-8, pollutants are added to the airstream and their flow is controlled. Hydrogen fluoride is added to the air by evaporation from a solution; sulphur dioxide, ammonia and propene are added from bottles of liquified gas; nitrogen dioxide is added from a heated bottle of liquified gas. The degree of humidification is achieved by evaporation. The test chamber is made of polyester reinforced with glass fibre and has a volume of one cubic metre; it is cylindrical, with a thermostatic bath to control the temperature. The gas streams go into a mixing chamber with a sampling device and then into the test chamber. Samples are placed on a rack; there are spray nozzles to simulate rain over the samples or to generate salt vapour. With the normal air flow of 25 litres per minute, the residence time is 40 minutes. When the conditions change, 99% of new conditions are reached in 147 minutes. The radiation source has to be located outside the chamber, due to the corrosive nature of the atmospheres generated. As radiation transmitter, films of Teflon FEP are used, as it has good resistance to chemical attack and excellent transmission of ultraviolet radiation of every wavelength. The sampling device has five independent lines that allow sampling simultaneously at five points in the test chamber. To obtain samples of pollutant gases, sampling ports with the appropriate absorbing solutions are used. Five types of limestone used in cathedrals of Andalucia were studied, as well as samples from quarries in the region. Their most important characteristics are as follows:

Evaluation of hydrophobic treatments applied to stones used in andalusian cathedrals. III.-Accelerated weathering test with polluted atmosphere

SUMMARY In this work we study the weathering resistance of samples of five types of stone used in Andalusian Cathedrals, treated with six water repellent products, by subjecting the samples to a SO 2 polluted atmosphere. To evaluate the alteration of the samples, besides visual observation of macroscopic aspect, changes in weight and the quantity of sulfate that remains on the surface have been measured. Also properties related with water have been measured after the test to determine if there have been any changes in the hydrophobic characteristics.

Properties of Cotton Fabrics Treated with Fluorocarbon Combinations with Water Repellents

This paper shows some of the effects which can be obtained on cotton through the combined use of a fluorochemical textile finish and conventional water-repellent products. The types of water repellents included in this study are quaternaries, stearamide-resin dispersions, silicones, aluminum salt-wax emulsions, zirconium salt-wax emulsions, and a cationic thermosetting compound. The effects studied, and for which data are presented, include dynamic absorbency, spray ratings, soil resistance, whiteness, and mildew resistance. The properties obtained are also evaluated for their resistance toward laundering, dry cleaning, weathering, and abrasion.