What You Need To Know About Urethane Casting Material

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Our blog is a comprehensive resource for anyone interested in learning more about this versatile and affordable surface finish option.

Urethane casting is a rapid and cost-effective method for producing end-use plastic parts in low to medium volumes. The process involves creating silicone casting molds from a part’s master pattern, then cutting the molds in half so that they can be brought to production. Able to support a wide range of viable part designs, urethane casting is commonly used for parts prototyping, bridge tooling, and fabricating parts with fine details, varying wall thicknesses, and complex geometries.

Urethane Casting Material Selection Factors

When selecting a urethane casting material, there are several key factors to consider to ensure that the material meets the specific requirements of your project. Here are the main selection criteria:

// Hardness (Shore A or Shore D)

Shore A hardness is typically used for flexible or rubber-like materials, while Shore D is used for harder, more rigid materials. The desired hardness will depend on the function of the cast part. Soft, flexible parts will require lower Shore A values, while more rigid parts will need higher Shore A or Shore D values.

Tensile Strength & Elongation 

This is the material's ability to withstand stretching or pulling before breaking. If the part will experience significant mechanical stress, you'll want a urethane casting material with higher tensile strength. 

Elongation refers to the material's ability to stretch before breaking. If flexibility and the ability to deform without breaking are important (e.g., parts that need to bend), look for materials with higher elongation.

Tear Resistance & Impact Resistance & Temperature Resistance & Chemical Resistance

If the cast part will be exposed to sharp edges or rough handling, tear resistance is crucial. Materials with higher tear resistance will last longer under stress and avoid tearing or damage in high-stress environments.

Urethane's ability to withstand sudden, forceful impacts is important for applications where the material will be subject to drops, hits, or sudden stress (e.g., automotive parts, casings, etc.).

Urethanes can vary significantly in how they perform in different temperature ranges. Some materials are suited for high-heat environments, while others may perform best in cooler conditions. Be sure to select a urethane material that is rated for the temperature range it will be exposed to.

Depending on the end use, the urethane material may need to be resistant to oils, solvents, acids, or other chemicals. If chemical exposure is a concern, ensure that the material selected is resistant to the relevant substances.

Color &  Finish

Urethane materials come in different colors, and some can be pigmented or painted. If the final product needs to have a specific color or appearance, make sure to choose a urethane resin that can be easily modified or is available in the desired color.

Shrinkage &  UV Stability

Urethane materials tend to shrink as they cure, although different formulations will shrink to different extents. Minimizing shrinkage is especially important for tight-tolerance applications, where dimensional accuracy is critical.

If the cast part will be used outdoors or exposed to sunlight for extended periods, UV stability will be an important consideration. Urethanes can degrade or discolor when exposed to UV light unless they're specifically formulated to resist UV radiation.

How To Choose Casting Material For Your Projects

Urethane materials can be rigid, elastic, transparent, and in a variety of colors. The designer or engineer can choose the best casting material for their project.

– Aesthetic requirements: appearance texture, color, transparent or not, what result they want to achieve.

– Use environment: Do the parts need to be within the low or high temperature? Do the parts need to be in an environment with ultraviolet light? The casting material option needs to cover these considerations.

– Functional requirements: For example, if the parts need good sealing and flexibility, you can choose a casting material that is similar to rubber. The parts with requirements of good strength can use casting material that is similar to ABS material.

Urethane Casting Material

3 Common Urethane Casting Material

1. Hei-cast 8150

This material is of the Japanese brand and is a common, economical urethane casting material, which is comparable in strength and impact resistance to ABS, a thermoplastic polymer.

This casting material is rigid and durable, can be a good option for the enclosure of most products, such as consumer electronics, toys, equipment, etc.

The color of the casting material can be adjusted for products with a color scheme or for prototypes with various colors. And because the color is not only on the surface, there is no worry about the color falling off, and it does not affect the surface texture.

In addition, due to the UV radiation list of polyurethane castable materials, if the product is to be used outdoors, it needs to be coated with UV protection.

Opaque casting material Transparent casting material

2. PX-5210

This French brand casting material is transparent, which is similar to PMMA material. It is a good option for most transparent optical components, such as light guides, lenses, or other optical parts. If using this material during silicon tooling, which needs to be in a vacuum environment, to avoid bubbles, so as affect the cosmetic appearance. Besides, this casting material can also adjust the color.

For example, a part with two colors requirement but wants to be made in one piece, not separately.

At this time, the transparent casting material can be used to adjust the color. First, casting the opaque part and then the transparent part (to avoid that if casting the opaque part later, the material will flow to the transparent part, thus affecting the appearance), to obtain the overall effect.

In addition, it can also be used to imitate the injection material with a diffusion function. Through the preliminary test, a certain proportion of diffusion powder is added to the casting material and the color is adjusted to obtain diffusion function.

3. UPS-8400

The casting material is flexible and the hardness can be adjusted within a certain range.

This urethanes material is similar to rubber and has many mechanical properties.

Like good impact resistance and flexibility, it can be used for projects such as rubber handles and skins, cladding, buttons and keyboards, cable connectors, and even rubber boots.

Products with the hardness of 50 Shore A and below provide high tensile strength, toughness, and flexibility, while 60 to 80 Shore A products are ideal for wear-resistant parts and fixtures with some flexibility.

Urethane Casting: A Good Option For Low Volume Production

For most projects, urethane casting can shorten production time, reduce mold costs, and allow flexibility in material selection to meet project requirements. No matter it is a rigid material with high strength, or a transparent optical part, or a flexible material with high tensile strength, it can be achieved all these results.

Of course, if you have no idea how to choose, choose IDEAL, a reliable manufacturer, we can reduce the burden, provide professional manufacturing suggestions. If you have an upcoming or ongoing similar project, don't hesitate to contact us.