ROOFING WITH POLYURETHANE MASTIC MATERIALS

At the present time among the mastic polymer materials used for waterproofing roofs, the most common are cold curing polyurethane mastics. These mastics are pigmented liquid viscous masses, which, being applied to the protected surface, polymerize to form a seamless monolithic elastomeric membrane. By the nature of curing polyurethane mastics are divided into one-component, curing by air moisture, and two-component, curing by special curing agents. The plant "Bitum Petrochemical Industries ltd" produces one-component polyurethane materials Polyseal 400, Polyseal 600-aliphatic polyurethane mastic material.
Roofing membranes based on polyurethane mastic elastomers - a fundamentally new waterproofing materials, which have such parameters of reliability, which even remotely can not come close not only polymerbitumen roll-fed and mastic materials, but sometimes roll-fed polymer roofing (membranes).

It is well known that the structures of roofing in the process of operation experience temperature, static, dynamic loads and deformations: temperature compression and stretching, shrinkage, wind loading, bending and stretching in the expansion and settlement joints, etc. Such deformations are small and in most cases do not exceed fractions of a percent. Nevertheless, within a few years such sign-variable deformations loosen the roof system, forming defects in it, mainly in the joints of roll roofing materials. Deformation and, consequently, and the stresses in the roofs are distributed very unevenly, concentrated in the weakest places of roofs - temperature seams, the adjacency of horizontal and vertical surfaces, expansion joints with different settlements of parts of buildings, etc. In these places, deformation and stresses are very high. And it is in these places often occur tears in the roof mat.

1. Polyurethane mastics have excellent adhesion to all building materials: stone, concrete, metal, bitumen, some polymers, wood. Removal of the mastic membrane from the substrate is only possible by mechanical means. As a rule, the use of primers under the quality polyurethane waterproofing systems is not required. Their use is recommended when applied to wet substrates (humidity from 10 to 20%), as well as weak substrates that require fixation. This does not cancel the careful preparation of the protected surface, as the most important condition for obtaining the desired result.

2. Mastic polyurethane roofs are seamless. And it is the seams are the potential defective places of roofs and sources of leaks. For example polymerbitumen roll roofing for 1000 m2 gain more than 1000 pg. m. seams, in polymer roll membrane roofing - half as much.

3. Polyurethane mastic membranes are characterized by exceptional strength, and elasticity (relative deformations at rupture 600%), remaining in the whole range of operating temperatures from -500C to +800C. Such membranes are capable of stretching without rupture within the limits exceeding the deformation of the protected structure. Due to the ability to large deformations, polyurethane mastic roofs are indispensable in areas with a harsh continental climate, large daily cyclical temperature differences, including low negative temperatures.

4. Polyurethane mastic membranes have high resistance to ultraviolet solar radiation, temperature resistance (up to 900C), resistance to mechanical damage, wear resistance. Polyurethane membranes are resistant to aggressive environments - saline solutions, dilute acids and alkalis, abrasion and shock loads, the effects of roots, as well as biological effects - biodegradable mold fungi.

5. Vapor permeability of polyurethane membranes. Polyurethane mastic membranes are diffusively permeable to water vapor, unlike bituminous roofing materials. This significantly reduces the risk of moisture accumulation in the insulation and screed under the membrane and its possible separation from the substrate. Low resistance to diffusion of water vapor is one of the most important advantages of polyurethane membranes, allowing, for example, to repair old polymerbitumen roll roofing without completely removing the wet roofing pie. Polyurethane membranes will not interfere with the gradual drying of roofing materials. However, in order to obtain a guaranteed result is still necessary to install under the polyurethane membrane roof aerators.

These physical and mechanical parameters of polyurethane membranes almost do not change over time, which makes it possible to predict their service life up to 50 years. Such roofs are not afraid of frost, temperature fluctuations, hot summers.

6. No or low mass fraction of solvents. Volatile organic solvents contained in some mastic polymeric materials (e.g., based on chlorosulfated polyethylene) cause problems associated with fire hazards and toxicity of their use. Due to the absence of solvents, polyurethane mastics meet modern environmental requirements. Polymerization of such mastics goes practically without changing their volume (shrinkage), typical of materials with high solvent content.

7. Technological efficiency and high speed of works on the arrangement of mastic membranes. Polyurethane mastics are completely ready to use, easy to work, applied in several layers by hand, brush, roller, rubber trowel, or mechanized, by airless spraying.

Especially noticeable advantages of the technology of the device mastic roofing for waterproofing problem areas (numerous junctions at the walls, parapets, elevator and ventilation shafts, pipes, drains, nodes, details). In these places, the thick roll bitumen materials must be cut to complex shapes, which significantly increases the labor intensity of work and increases the risk of leaks in the future. The use of polyurethane mastics makes such work simple and guaranteed more reliable.
Rapid polymerization of polyurethane elastomers (at 200C drying "on the stick" the initial liquid mastic takes 60-90 minutes and its transformation into a polymer membrane - for 4-5 hours) can apply 2-3 layers of coating for 1-2 days over an area of about 500-1000 m2, in a short time making a polyurethane membrane ready for use. This is much faster than the device polymerbitumnyh roofing roll coating. However, please note that the lower ambient temperature dramatically slows down the process of polymerization of mastic. The minimum temperature for applying mastics +50 ° C.

8. Ease of repair in the event of damage to the roof (e.g., a puncture). An additional layer of polyurethane mastic can be applied to the area in the form of a reinforced or unreinforced patch in a short time.

The above-mentioned technical characteristics of the mastic polyurethane materials can be used not only as a waterproofing layer, but also as the finish coating of the roof without further protection. To increase the resistance of the roof from the effects of UV light, the top layer of the roof can be performed with an aliphatic polyurethane composition is absolutely resistant to such influences.
The choice of colors of polyurethane roofing mastics is almost unlimited. However, when constructing roofing membranes preference should be given to light-colored mastics with high reflectivity. Light-colored roofing absorbs less solar energy, less heat, less susceptible to thermal degradation and, therefore, more durable. In addition, the high reflectivity of roofing coatings such favorably affects the temperature conditions inside the building with such roofs, which is sometimes quite important, for example, for poultry and livestock facilities.

A variety of mastic roofing on the basis of polyurethanes is a mastic roofing with reinforcement. A special polyester calendered geotextile with a density of 100-110 g/m2 is used as a reinforcing layer. When performing such a system, first the first layer of mastic is applied to the substrate, then a layer of geotextile is placed, which is closed with 1-2 layers of mastic.

The system can be used for repairs with or without continuous reinforcement. A system without reinforcement is used to repair roofs with relatively small damages. In such a system, reinforcement is used only directly on the damaged areas to make patches.
The use of geotextiles increases the durability of the coating, but more importantly significantly reduces the preparation requirements for the substrate and allows you to control the thickness of the waterproofing layer. Mastic roofing should preferably be carried out with an aliphatic polyurethane topcoat, such as Polyseal 600. Due to the fact that aliphatic mastics have the highest resistance to UV radiation, their use as a finishing layer significantly increases the service life of the coating, as well as eliminates color fading under the influence of sunlight.
Polyurethane mastics are excellent for repairing almost all types of roofs: rolled bitumen and polymer, metal, concrete, etc. If necessary, repairs can be made without removing the old roof.
To create an anti-slip effect on a moderately pitched roof using a fine-grained mineral sprinkles from the materials used for sprinkling of bituminous roofing roll (granite or marble chips, dry sand, etc.). Consumption of mineral dusting 1.1-1.5 kg/m2. This sprinkling increases the roughness of the coating, which is beneficial when walking on the roof, especially in the fall and winter. Mineral sprinkles evenly with the excess spread on the still liquid top layer of mastic until it is completely covered. After polymerization of mastic, unattached particles of crumbs or sand are removed from its surface with brushes or vacuum cleaner.
Polyurethane mastic roofing has only one serious disadvantage - high price. Polyurethane mastics are much more expensive than cheap bitumen mastics and roll roofing. However, the price is not so dramatically different as a measure of longevity of the roof.

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