What are the advantages and disadvantages of polyurethane?

Advantages of polyurethane:
(1) Wide hardness range.
(2) High strength.
(3) The adjustable range of performance is large. A number of physical mechanical performance indicators can change through the selection of raw materials and formulas to change within a certain range, thereby meeting the user's different requirements for product performance
(4) wear resistance. There is a good name for "wear -resistant rubber".
(5) Oil resistance. The oil resistance of polyester polyurethane elastic body is not lower than that of chores, which is equivalent to polysulfonal rubber.
(6) Excellent ozone resistance.
(7) Good resistance to shock absorption, radiation resistance and air resistance.
(8) There are diverse processing methods and wide applicability.
The disadvantages of polyurethane:
(1) endogenous heat, general high temperature resistance, especially not well -damp -resistance. The normal use temperature range is used -40 ~ 120 ℃. If a long -term effect is required under high -frequency oscillation conditions or high temperature conditions, corresponding modification measures must be taken in structural design or formula.
(2) Inaulte -resistant polar solvent and strong acid and alkali medium. At a certain temperature, alcohol, acid, and ketone will cause polyurethane elastic bloating and degradation, and solvents such as chloroform, dichloromethane, di metamimamide, and methamphetamine at normal temperature will cause polyurethane elastic bodies.
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The advantages and disadvantages of epoxy resin:
(1) High mechanical performance. Epoxy resin has a strong internal agglomeration and dense molecular structure, so its mechanical properties are higher than that of phenolic resin and unsaturated polyester and other universal thermal solid resin. (2) Strong adhesion. The epoxy resin curing system contains polarity groups such as epoxyl, hydroxyl groups, and polar groups such as ether bonds, amine bonds, ester bonds, etc., which gives cyclic oxides to metals, ceramics, glass, concrete, wood and other extremely Sexual base materials with excellent adhesion. (3) Little curing and contraction. Generally 1%to 2%. It is one of the varieties with the smallest curing rate in thermoso resin (the phenolic resin is 8%to 10%; the unsaturated polyester resin is 4%to 6%; the silicon resin is 4%to 8%). The lineflating coefficient is also very small, generally 6 × 10-5/℃. Therefore, the volume change after curing is not much. (4) Good craftsmanship. When the epoxy resin is curing, the low -molecular volatilizer is basically not produced, so it can be formed at a low voltage or contact the pressure. It can cooperate with various curing agents to create environmentally friendly coatings such as solventless, high -solids, powder coatings and water -based coatings. (5) Excellent electrical insulation. Epoxy resin is one of the best varieties of thermosetry intermediary electrical performance. (6) Good stability and excellent anti -chemical drugs. Epoxy resins without alkali, salt and other impurities are not easy to deteriorate. As long as it is stored properly (sealed, non -moisture, no high temperature), its storage period is 1 year. If the inspection is qualified after the overdue, it can be used. Epoxy curing is excellent chemical stability. The performance of a variety of media such as alkali, acid, and salt is better than unsaturated polyester resin and phenolic resin. Therefore, epoxy resin is used as a large number of anti -corrosion primer, and due to the three -dimensional mesh structure of epoxy resin curing, it can also be impregnated with oil resistance. (7) The heat resistance of epoxy curing is generally 80-100 ° C. The heat -resistant variety of epoxy resin can reach 200 ° C or higher

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