VFI®-3161 60 A MDI Molding Rubber

VFI®-3161 60 A MDI Molding Rubber

VFI-3161 60 A MDI Molding Rubber is a 1A:2B, versatile urethane rubber that has high durability to make strong, flexible concrete molds and form liners. MDI-based rubber is best used in controlled, high-production environments where little moisture interaction is involved. The material maintains a workable viscosity, allowing you to pour thin, intricate parts or large parts quickly. Its viscosity also helps dissipate air bubbles without using a vacuum chamber. An extended pot life provides ample time to work with the material. The standard color of VFI-3161 is green, but a neutral color (VFI-3163) is available.

VFI-3161 60 A MDI Molding Rubber from VFI is a versatile urethane with an extended pot life for making strong concrete molds and formliners.

Features & Benefits

  • Captures excellent detail and texture for high-quality, repeatable results
  • Superior physical properties for making concrete molds and form liners
  • 60 A elastomer with excellent rebound properties for easier demolding
  • Moderate viscosity for pouring thin, intricate parts or large parts quickly
  • Removes air bubbles without the need for vacuum degassing
  • Outperforms when casting pigmented and colored concrete
  • Consistent results in large- or small-scale applications
  • Easy processing at room temperature

Instructions for Use:

Mold Preparation

The molding surface must be clean, dry, and free of dirt, oils, and debris. Use only non-sulfurous clay on molds to prevent unwanted adhesion and improper cure. The molding surface must be fully sealed and non-porous. Use a release agent to prevent adhesion. We recommend using Chem-Trend MR-515 Aerosol or a similar release agent. Spray several layers over the entire mold, waiting for the surface to dry before adding more. The release will help protect and extend the life of the mold. Spraying too much release can produce a shiny/glossy surface on the rubber that will transfer over to future castings. The material is compatible with most molds as long as it is used with a proper release agent.

Molding Process

The material should be at least 65°F before use for proper mixing and application. Mixing times may vary depending on volume and mixing method. Vacuum degassing can further reduce air entrapment but is not required.

  • Premix the B side (Poly) until uniform before combining it with the A side (Iso). Mix slowly to minimize air entrapment.
  • Check the technical data sheet for the proper mix ratio by weight or volume and calculate the material needed on both sides.
  • Measure the A side into a clean mixing container.
  • Follow by measuring and adding the B side material into the same container.
  • Mix until uniform. Power mixing or meter mixing equipment is recommended for quantities over 1 gallon. Scrape the bottom and sides of the container to ensure a uniform mix is achieved.
  • Transfer to a new container and mix again before use. It must be fully mixed and poured before the end of the pot life.

Pour the material in one spot at the lowest point of the mold until the desired thickness is reached. VFI recommends pouring at least ½ of an inch thick. Allow the rubber to sit at room temperature for a minimum of 16 hours before demolding. It will develop full physical properties after 7 days at room temperature. It is required that the rubber sits for 3 days at room temperature before use or shipping. When using the rubber for casting, apply a release agent before each use.


*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 all 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

This product contains isocyanate, which can irritate the skin and is toxic if inhaled as particulate matter. Avoid prolonged breathing of vapors and repeated skin contact. It is not UV color stable and has no long-term UV testing. Urethane is very moisture-sensitive, so VFI-3161 should only be used in a controlled, high-production environment to limit moisture interaction. It must be protected from freezing.

  • Incompatible materials – A side: water, alcohols, amines, bases, and acids. B side: 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 – A side: carbon monoxide, carbon dioxide, nitrogen oxides, hydrocarbons, and HCN. B side: may include, and are not limited to, oxides of carbon

Potential Health Hazards

  • May cause respiratory tract irritation. A side material may also cause allergy and asthma symptoms or breathing difficulties if inhaled.
  • Causes skin irritation and sensitization: redness, edema, drying, defatting, and cracking of the skin. Repeated exposure to B side material can result in absorption through the skin, causing a significant health hazard.
  • Causes serious eye irritation: discomfort, pain, excess blinking and tear production, marked redness, and swelling of the conjunctiva.
  • May cause stomach distress, nausea, or vomiting if swallowed.

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

Application Methods:

  • Pour Pour

Available Packaging:

  • Tote
  • Drum
  • 5 Gallon
  • 1 Gallon