VFI®-178 90 A Polyurethane Casting Rubber

VFI®-178 90 A Polyurethane Casting Rubber

VFI-178 90 A Polyurethane Casting Rubber is a fast-setting urethane rubber with good rebound properties. The urethane’s viscosity allows for easy processing when pouring or injecting and the creation of larger castings that maintain final properties. VFI-178 has superior tensile strength, tear strength, and elongation, providing castings with increased durability and resilience. With a high amine content, the rubber provides good chemical resistance and low-temperature flexibility for extended use of a mold or part. The material’s fast setting capabilities allow for a quick demold time that increases part production.

VFI-178 90 A Polyurethane Casting Rubber from VFI is a fast-setting, hard rubber with excellent properties to produce durable and resilient castings.

Features & Benefits

  • Excellent physical properties for making industrial parts and prototypes
  • Highly durable, versatile urethane with good rebound properties
  • 1:1 mix ratio for easy processing to avoid costly off-ratio mixes
  • Capable of curing without a robust post-curing process
  • Great chemical resistance and low-temperature flexibility

Instructions for Use:

Mold Preparation

Clean all molding surfaces to ensure they are free of dirt, debris, oils, and other contaminants. The surface must be sealed with a release agent for ease of demolding the material. The release agent will help extend the life of the mold and prevent unwanted adhesion. Compatible molds for casting include urethane and metal when properly prepared. The material can be used with platinum silicone molds but will create a surface tack, so it must be removed from the silicone mold and post-cured. You may heat the mold between 70°F-150°F to accelerate the cure process and achieve a quicker demold. However, heating the mold will shorten the pot life.

Casting Process

Premix the B side (Poly) until uniform before combing with the A side (Iso). We recommend injecting this material due to the short work time, but it can also be hand poured. When pouring by hand, pour the weighed B side into the weighed A side and mix until uniform. You may mix smaller amounts by hand, but we recommend using a power mixer if you are using over ½ a gallon of material. Transfer the material into a new container and mix again until uniform. The material must be fully mixed and used before the duration of the pot life (3 min.), which will shorten at temperatures above 72°F.

There is no limit to thickness when using VFI-178, but if you are pouring or injecting less than 1/16th of an inch thick, you will have to post-cure the material. Allow the material to cure for at least 20 minutes at room temperature before demolding. Thinner pours will need more time to cure to develop the necessary green strength to demold. VFI-178 will reach full physical properties after 10 days. To achieve final properties faster, the material can be post cured in an oven at 150°F for 16 hours. Silicone molds must be post-cured at room temperature for one day or at 150°F in an oven for 2 hours to remove surface tack.


*Always read the safety data sheet before working with chemicals 

Use chemicals only as directed and for their intended purpose. Do not dispose of chemicals down the drain. Most chemicals must be disposed of as hazardous waste.

PPE to avoid unnecessary exposure:

  • Eye protection – wear approved safety glasses and any additional eye protection as necessary
  • Hand protection – wear chemically resistant protective gloves (nitrile, butyl, or neoprene)
  • Skin and body protection – wear suitable protective clothing
  • Respiratory protection – in case of insufficient ventilation, wear suitable respiratory equipment. Respirator selection must be based on known or anticipated exposure levels, the hazards of the product, and the safe working limits of the selected respirator

Product Limitations

VFI-178 contains isocyanate, which is irritating to the skin and toxic if inhaled. Avoid prolonged breathing of vapors and repeated skin contact. The material is not UV color stable and has no long-term UV testing. It is sensitive to moisture and cannot be cross mixed with other materials.

  • Incompatible materials – A side: strong bases, acids, alcohols, amines, and water. B side: strong oxidizers
  • Conditions to avoid – heat and incompatible materials
  • Chemical stability – stable under normal storage conditions
  • Reactivity & hazardous reactions – no dangerous reaction known under normal use
  • Hazardous decomposition products – may include, and are not limited to, oxides of carbon as well as oxides of nitrogen and isocyanates for the A side

Potential Health Hazards

  • May cause stomach distress, nausea, or vomiting if swallowed.
  • May cause respiratory tract irritation. A side may cause allergy and asthma symptoms or breathing difficulties if inhaled.
  • Causes skin irritation or sensitization: redness, edema, drying, defatting, and cracking of the skin.
  • Causes serious eye irritation: discomfort, pain, excess blinking and tear production, marked redness, and swelling of the conjunctiva.

*If you are experiencing any of these symptoms, seek medical advice or attention. Call a poison control center or doctor if swallowed. 

Application Methods:

  • Inject Inject
  • Pour Pour

Available Packaging:

  • Tote
  • Drum
  • 5 Gallon
  • 1 Gallon