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Understanding Heat Resistant Materials

It is often extremely important to choose parts made with a heat resistant material, which can withstand the temperatures of extreme climates or vehicle engines without suffering damage.

However, not every heat resistant material is created equal. Ceramics can maintain their form at extremely high temperatures, but are extremely brittle and break after only the slightest drop or impact. Metal rarely melts, but it can rust, corrode or wear down in other ways – not to mention the fact that it is heavy, bulky, and often expensive.

Luckily, Romeo RIM has the solution for you. Our heat resistant thermoset polymers – particularly polyurethane – possess all of the benefits of ceramics or metals without any of the weight, price, brittleness or other drawbacks. This guide discusses in detail the heat resistant properties of our polymers and how they can improve the performance of molded parts for any number of markets.


Thermoset Polymers and Their Heat Resistance

Thermoset polymers, also referred to as thermosetting plastics or thermosetting polymers, are a specific subset of manmade compounds with a unique property: while initially existing as a liquid, they retain their solid state indefinitely after being cured only once.

It is this quality which gives this particular class of polymers their higher than average resistance to heat – and a number of other factors as well. To put it simply, a thermoset polymer will not melt even when exposed to extreme heat; nor will it warp or corrode when exposed to extreme cold or any number of strong chemicals.

Their heat resistance is in direct contrast to another group of polymers, thermoplastics, which melt easily when exposed to only a small amount of heat. While this means that thermoplastics can be easily recycled and re-formed into new shapes, it also means that they are unsuitable for use in the manufacture of parts which will regularly experience any kind of high temperatures.

Common examples of thermoset polymers used in the molded parts industry include epoxy, silicone, phenolic, polyester, and polyurethane. They can be cured via the quick, efficient process of reaction injection molding (RIM). Thermoset polymers can also easily be reinforced via the addition of fibers such as glass, carbon, graphite or aramid. These fibers increase the already excellent heat resistance of the polymers even further, and grants them higher stiffness which allows them to resist deformation caused by temperatures, weather, impacts, or natural wear and tear.

Polyurethane: Above and Beyond Just Resisting Heat

Of the thermoset polymers listed above, polyurethane possesses a particularly high heat resistance. In fact, polyurethane was initially invented to be used as a protective coating for European military aircraft during World War II, and was specifically designed to be able to resist the high temperatures regularly reached by jet engines.

In addition, polyurethane is strong, durable and up to 60-80% more lightweight than metals such as steel and aluminum. For this reason, it is the primary material used in the majority of Romeo RIM’s reaction injection molding processes.

Polyurethane reaction injection molding is a quick, efficient, simple process. Liquid polyol and isocyanate are injected into an impinging mixer, where they are combined at a high velocity. A chemical agent is added to induce the curing reaction; pressure is applied and the closed mold, typically constructed from aluminum, is heated to approximately 325 degrees Fahrenheit (163 degrees Celsius). The entire cycle takes only a few minutes; the resulting part is fully cured and requires no post-cure processing.

Reinforcing fibers, typically glass or carbon, can be added to increase the heat resistance of the final part. If the fibers are added in a chopped or milled form, it is referred to as reinforced reaction injection molding (RRIM), while the addition of fiber mats, meshes or preforms is known as structural reaction injection molding (SRIM). Both processes create a molded polyurethane part which will retain function without experiencing even the slightest deformation at high temperatures. If your part will operate in a hot climate or be regularly exposed to open flame or other sources of extreme heat, RRIM or SRIM may be the right process for you.

Why Choose a Heat Resistant Thermoset Polymer?

Heat plays a large role in a number of industries ranging from consumer vehicles and heavy agricultural machinery to hot tubs and personal spas. In particular, vehicle engines have grown increasingly hotter and harsher as smaller, high performance, fuel-efficient engines become ever more popular and prevalent. Some engines on even the smallest of modern consumer vehicles can regularly reach temperatures of approximately 446 degrees Fahrenheit (230 degrees Celsius).

In an increasingly heat-focused and heat-dependent world, there is possibly no more important property for molding materials than heat resistance. Romeo RIM’s thermoset polyurethane can easily withstand the temperatures discussed above without melting, breaking down or beginning to show even the slightest deformation. This allows polyurethane parts to function for years and years while retaining their original strength, durability, and excellent aesthetic qualities. In addition, beneficial qualities such as stiffness, flexibility or elasticity – depending on the part and its intended purpose – are not lost at high temperatures.

Whether your part needs to survive the heat of a revving car or machine engine or the therapeutic but boiling temperatures of a personal spa, thermoset polyurethane is the solution that you have been looking for. Its excellent heat resistance pairs with strength, durability and glossy Class A finishes capable of being painted directly within the mold.

In addition, the reaction injection molding process is simple as well as both cost- and time-efficient, completed in only a few minutes with the assistance of Romeo RIM’s high-tech robots and molding machinery. If that wasn’t enough, reaction injection molding can be used to produce a wide range of part geometries and details, including variable wall thickness and B-side geometry. Contact Romeo RIM today to learn more about our heat resistant thermoset polyurethane and its usefulness in producing a wide range of high quality molded parts.

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