Some applications of polyurethanes
The use of polyurethanes, polyureas and polyurethane dispersions and other compounds participating in their reactions is constantly expanding and various articles and reports are published in this regard.
The applications of these compounds are also constantly evolving.
Polyurethane foam
Polyurethane foam with a closed cell structure that is based on polyurethane, the presence of catalysts and blowers with chemical reaction of polyisocyanates with compounds containing acidic hydrogen. The advantages of polyurethane foam are: low thermal conductivity, which is less than all other common insulation materials, light weight, high strength, high ability to accept changes in formulation to meet practical expectations, strong adhesion to many materials, low permeability Water vapor, heat resistance at temperatures above 100 ° C, the ability to foam in place to fill complex shapes, hard polyurethane foam has been used as a thermal insulator over a wide range of temperatures. .For example, this type of foam is used in insulating liquid nitrogen at -196 degrees Celsius and steam at +126 degrees Celsius. The flexible form of polyurethane can also be used to insulate pipes. Polyurethane foams are used as a thin layer with high efficiency insulation of refrigerators and freezers. Today, attempts are made to make polyurethane foam with a gas other than CFC (carbon chlorofluoride) as a blower. Although these gases do not insulate as well as CFC gases, they do less damage to the ozone layer of the planet Earth, the density of foams made by the new method is usually 32 kg / m3. Low-density open-cell polyurethane foams (8 kg / m3) are also available. Some low-density types use carbon dioxide as a blower, and low-density foams are sprayed into open double-walled walls. They expand quickly and seal the empty space. Slow-expanding foams are intended for existing buildings that do not have thermal insulation. This liquid foam expands very slowly, thus reducing the risk of damage to the wall due to over-expansion. The foam is water vapor permeable, flexible and performs good air sealing against water suction. It is also slow-burning and the flame will not be stable after the fire is extinguished, but the important point is that the toxic gases of hydrogen cyanide (cyanide) are released in the presence of heat or when burning.
Application of polyurethanes and polyureas in flooring
The types of technology used in floor coverings are all based on two principles. One of them is thin film technology, in which one or more coatings with a thickness of about 50 to 125 microns are applied on the floor surface. Sealing and dust removal are also among the important steps in this method, the ultimate goal of which is to achieve floors with the following and decorated designs. Resins used in floor coverings are: alkyds, epoxies or epoxy esters based on water and solvents, suspended mixtures, water-based polyurethane mixtures and various types of acrylic polymers. The best case for this type of flooring is that the effect of materials Chemicals or water on the floor surface can be easily removed and no stain will be left. Alkyd coatings are very weak against caustic soda. Another type of coating is thick film technology, in which the minimum coating thickness is 200 microns and the maximum is sometimes up to ten millimeters. The purpose of this type of coating is to fill cracks, cavities and level heavily worn surfaces. Thick coatings. Cement and stone materials are mixed with a variety of resins. Epoxies, aromatic polyurethanes (often small oils and MDI di_phenylmethane 4_, 4_ SBR latex isocyanate and acrylic are the most commonly used resins. This is followed by manual troweling or roller application. In some cases, unsaturated esters, vinyl esters and 100% solid epoxies are used in thick floors. MDI-based aromatic polyurethanes are used for coating. Floors are widely used because MDI isocyanate is relatively inexpensive, and it is interesting to note that the MDI molecule and the polymer synthesized from it easily absorb ultraviolet light, causing yellowing of coatings exposed to sunlight. This is the issue.
Polyurethane adhesive
Polyurethane resin-based adhesive fills the joints of concrete structures with high flexibility and impermeability. These joints include executive and non-executive joints. Polyurethane adhesive has many valuable properties. They are very resistant to high temperatures and maintain their stability up to a maximum temperature of 210 degrees Fahrenheit (100 degrees Celsius). They are very flexible when dry and are resistant to dissolution in strong acidic or alkaline chemicals. Polyurethane adhesive is a type of adhesive that is used in various commercial industries as well as in entertainment and handicrafts. Some polyurethane adhesives are formulated in such a way that they can be used as a sealant or putty tool. For example, its jelly form is often used in the construction or repair of boats or light aircraft. Other types of polyurethane adhesives are used in carpentry, metalworking and masonry. Construction types of polyurethane adhesives can be used on composite floors, flooring and concrete.
Polyurethane adhesive is available in several common forms. First, it is used in home form and light industrial glue for gluing wood or ceramic materials. It is also used in the form of polyurethane gel in cartridges such as silicone or for sealing in buildings and repairs of houses, furniture and boats and stone buildings. These adhesives are able to connect two objects, one of which is porous. Some heavy-duty polyurethane adhesives are used in cartridges and become 25 percent stronger if they have a longer drying time. There is a component in the market that some of these applications create high added value.