VFI®-3280 80 A MDI Molding Rubber

Thickness Requirements

Pour the material in one spot at the lowest point of the mold until the desired thickness is reached. VFI recommends pouring at least 3/8 of an inch thick. For thinner pours, use a higher durometer rubber such as VFI-3290 90 A MDI Molding Rubber.

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. Porous molding surfaces must be fully sealed. Use a release agent to prevent adhesion. We recommend 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.

Mixing

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.

Thoroughly mix the POLY “B” component before mixing with the ISO “A” component. Usually, this takes a minimum of 3 minutes per “B” container with proper mixing equipment. Power mixing or meter mixing equipment is recommended for quantities over 1 gallon. Once the “B” component is thoroughly mixed, properly pour 1 part of the “A” component into 2 parts of the “B” component by volume, 56.1 parts “A” component into 100 parts “B” component by weight. Thoroughly mix for at least 30 seconds while scraping the sides and bottom of the container, ensuring the mix is uniform and homogenous. Transfer to a separate, clean mixing container and mix again before use.

Post-Cure

Allow the rubber to sit at room temperature for a minimum of 4 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. Use a release agent from a reputable release company, such as Chem-Trend, Stoner Molding Solutions, or Cresset Chemical Co. Do not use a solvent-containing release, as it can distort (shrink or expand) the mold.

Storage/Shelf Life

Store between 60°F – 90°F in a clean, dry building. The shelf life of unopened containers is 12 months after the date of manufacture. VFI-3280 does not need to be freeze-protected and if it has frozen, bring it up to 65°F before use. Once open, use it immediately. If you plan to store open containers after use, we recommend sealing both sides with a nitrogen purge; otherwise, the pot life will be greatly reduced.

Precautions

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 moisture-sensitive and may foam when exposed to too much moisture, so use VFI-3280 in a controlled, high-production environment to limit moisture interaction. Use only with adequate ventilation. Do not thin or add foreign material to the product. See the Safety Data Sheet for complete safety information.