Properties of Coating Materials

Many properties of liquid paints can be measured with considerable accuracy. Samples must be homogeneous. They must also be sufficiently large to be representative for a given batch. Impurities and permanent material defects (e.g., skin formation, a hard sediment, or gelling of the paint) can be detected. The most common investigations to which a sample is subjected before starting the tests are described in ISO 1513. Only those tests that are important for paint storage, transportation, and application are described here. 

Viscosity. Although paint viscosity can be accurately measured with viscometers, paint consistency is normally assessed with /7oh cups. The time in seconds required for a known volume of paint to flow out of the cup through a jet is measured. Paints of higher or lower viscosity can be matched by using cups with different jet diameters. 

Measurement of the run-out time from flow cups has been adopted worldwide since this test can be performed anywhere (e.g., in the laboratory, during production, or on a building site). Nationally standardized sets of flow cups are normally used in major industrial countries and give similar but not identical results. An internationally standardized system of flow cups has been introduced (ISO 2431) to overcome this problem. Since temperature fluctuations greatly affect the viscosity measurement, the flow cups should only be used in conjunction with thermostated jackets. 

Measurements should be made at 23 0.5 C. According to ISO 2431 flow cups should only be used for substances exhibiting Newtonian flow. However, they are also often employed for near-Newtonian paints where the flow behavior at the desired viscosity deviates only slightly from Newtonian behavior (e.g., when adjusting the application consistency by dilution). 

Viscometers are being increasingly used for accurate measurements on modern industrial paints, especially waterborne paints. Rotating viscometers with a concentric cylindrical geometry (Searle system. Fig. 9.1) are advantageous for paints. Precise thermostatic control is easily achieved because the outer cylinder does not rotate. The drive and torque sensor are combined to form a single unit with the rotating inner cylinder. 

---

Initially, cycling in the coin cells, and later, in full prismatic cells with rated capacity of 7 Ah were used in our investigations. Also, advanced impedance spectroscopy methods were used to evaluate the electrochemical properties of coated materials. 

Unfortunately, there are no systematic data regarding the hydrophobic and hydrophilic properties of coating materials in present... 

The availability and formulation (and hence reflectance and outgassing properties) of coating materials and processes change as companies merge or change their focus, and as environmental laws evolve. For critical applications, it is important to monitor and somehow verify that the current version has not changed from the version whose properties were once investigated and found to be acceptable. 

The paper discusses the application of dynamic indentation method and apparatus for the evaluation of viscoelastic properties of polymeric materials. The three-element model of viscoelastic material has been used to calculate the rigidity and the viscosity. Using a measurements of the indentation as a function of a current velocity change on impact with the material under test, the contact force and the displacement diagrams as a function of time are plotted. Experimental results of the testing of polyvinyl chloride cable coating by dynamic indentation method and data of the static tensile test are presented. 

Moisture. Absorbed and retained moisture, especially as ice, has a significant effect on the stmctural and thermal properties of insulation materials. Most closed-ceU plastic foams have low permeance properties most notably where natural or bonded low permeance surface skins exist (29,30). Design, building, and constmction practices requite adequate vapor retarders, skins, coatings, sealants, etc, in order to prevent the presence of moisture. However, moisture vapor cannot be completely excluded, thus the possibiUty of moisture absorption and retention is always present. The freezing of moisture and mpturing of cells result in permanent reduction of thermal and stmctural performance. 

Radiation curing of epoxies with cationic initiators is well known [20—28]. UV-visible light has been the predominant radiation source the process has been limited to thin coatings due to the low penetration of the visible-UV light [22,23], Thermal and mechanical properties of these materials are low and the curing is incomplete. Several studies have shown that commercially available epoxies with various cationic initiators can be polymerized with EB curing [20,29-34]. 

Although the initial choice of coating material applied for reasons (b) or (c) may be dictated by the particular properties required, the corrosion behaviour of the composite metal coating/metal substrate system must also be taken into consideration in so far as it may affect the maintenance of the desired properties. Consequently, in all cases where protective metal coatings are used the corrosion performance of both coating and substrate require careful consideration. 

The CVD coating materials for wear and corrosion resistance consist mostly of carbides and nitrides and, to a lesser degree, borides. Table 17.1 compares the relative properties of these materials. 

Titanium Carbonitride. Ti(C,N) is a solid solution of TiC and TiN and combines the properties of both materials. It offers excellent protection against abrasive wear and has good lubricating characteristics. It is used to coat tools and dies for the processing of ceramics, graphite, and filled plastics. 

Biodegradable films made from edible biopolymers from renewable sources could become an important factor in reducing the environmental impact of plastic waste. Proteins, lipids, and polysaccharides are the main biopolymers employed to make edible films and coatings. Which of these components are present in different proportions and determine the properties of the material, as a barrier to water vapor, oxygen, carbon dioxide, and lipid transfer in food systems (Gomez-Guillen et al. 2002 and 2009). 

---