Bitumen combination coatings

The properties of bitumen paints (Section 2.14.2) can be favorably modified and adjusted to suit practical requirements by combination with other film-forming substances. For example, the thermoplasticity can be reduced and/or mechanical properties (e.g., hardness, extensibility) can be improved by adding polymers such as polyethylene, polypropylene, polyisobutene, and styrene-butadiene copolymers. The chemical resistance can also be improved high-quality corrosion protection coatings can be obtained by combination with alkyd resins. 

Bitumen is permanently compatible with only a few polymers and only when the latter are added in small amounts. Compatibility depends largely on the nature and origin of the bitumen. 

Combinations of bitumen with reaction-curing paint binders (e.g., epoxy resins and polyurethanes) are not usually employed in solvent-based paints due to their unsatisfactory compatibility. Only with high epoxy resin contents can a certain compatibility be achieved by addition of solubilizing phenols and aromatic oils. 

One and two-component waterproofing thick coatings, based on destination or polymer bitumen (bitumen emulsions), have become an increasing importance for the protection of buildings in wet-duty areas like cellar, bathrooms e.g. 

Those trowel-grade or sprayable materials can bridge cracks up to 5 mm and are leakproofed for soil moisture and pressurized water, depending on the layer. 

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In combinations with bituminous substances the proportion of chlorinated rubber ranges from 1 10 to 10 1. The ratio depends on whether the goal is to improve the bitumen-based coating without any substantial increase in cost, or to reduce the cost of the chlorinated rubber coating. Adhesion is improved but with the disadvantage of darker shades caused by the black bitumen. 

In thermoplastic solidification, the initial waste is dried and then combined with bitumen and polyethylene at a high temperature the mixture on cooling becomes a solid. In the second step, the solid waste is thermoplastically coated and then disposed of. This process is used for inorganic and radioactive wastes. 

Combinations with Bituminous Substances. Chlorinated rubber can be combined with bitumen and tars but compatibility has to be checked. Addition of chlorinated rubber reduces thermoplasticity, accelerates drying, and prevents cracking of the final coating in adverse weather conditions, without, however, adversely affecting the good adhesion, water resistance, and chemical resistance of the bituminous substance. 

Coal tar pitches are less readily available than they used to be their content of polynuclear aromatic hydrocarbons makes their safe use suspect. They have been replaced to some extent by the less effective petroleum bitumens whose mechanical properties are improved by combination with poly(vinyl chloride) and other chlorinated polymers as one-pack, nonconvertible coatings, or by combination with epoxy or polyurethanes in high-performance two-pack convertible coatings. Similar materials are preferred for coating ballast spaces and double bottoms in vessels, where economical systems are required that do not have to be attended throughout the lifetime of the vessel (15-25 years). Multiple coats with a total thickness of 250-400 pm are usually employed. 

Organic coatings include phenol formaldehyde, epoxy, polyacryl and polyacryl acid resins, polyamide, polyolefin, bitumen and rubber. The required properties of lining materials in combination with cathodic protection are given in Section 5.2.1. In addition, adequate resistance to water vapor diffusion is required (see Section 5.2.2). These properties are discussed in the basic standard for internal cathodic protection [2], which also reports how these properties can be assured by testing with the aid of Ref. 3. It is convenient to limit the protection potential region to [7 5 = -0.8 V in the presence of resin coatings, which makes potential-controlled protection current equipment necessary. 

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