VFI®-4240 78 D Polyurethane Casting Plastic

VFI-4240 78 D Polyurethane Casting Plastic is a two-component, 1A:1B by weight urethane plastic with high impact resistance, high heat deflection, and low shrinkage. It works well when vacuum-degassed and pressure-potted to provide repeatable, uniform, and void-free casts. It is a multi-faceted plastic capable of being used in rapid prototyping, production parts, and equipment housings for large part runs. If needed, it can be machined with CNC or woodworking equipment. There are alternative formulas available with 14-minute (VFI-4241) and 23-minute (VFI-4242) work times if needed.

Physical Properties	Test Method	Test Results
Shore Hardness	ASTM D2240	78 D
Tensile Strength	ASTM D638	7,700 psi
Tensile Modulus	ASTM D638	297,000 psi
Elongation at Break	ASTM D638	13%
Flexural Modulus	ASTM D790	336,000 psi
Izod Impact, Notched	ASTM D256	1.4 ft-lb/in
Linear Shrinkage	ASTM D2566	<0.005 in/in
Heat Deflection Temperature (@ 66 psi)	ASTM D648-18	206.96°F (97.2°C)
Flame Test	UL 94 V-0	No
Standard Cured Color	N/A	Off-White / Opaque

Physical Properties

Test Method

Test Results

Shore Hardness

ASTM D2240

78 D

Tensile Strength

ASTM D638

7,700 psi

Tensile Modulus

ASTM D638

297,000 psi

Elongation at Break

ASTM D638

13%

Flexural Modulus

ASTM D790

336,000 psi

Izod Impact, Notched

ASTM D256

1.4 ft-lb/in

Linear Shrinkage

ASTM D2566

<0.005 in/in

Heat Deflection Temperature (@ 66 psi)

ASTM D648-18

206.96°F (97.2°C)

Flame Test

UL 94 V-0

Standard Cured Color

N/A

Off-White / Opaque

Liquid Properties	Test Method	Test Results
Mix Ratio by Volume	N/A	89.5A:100B
Mix Ratio by Weight	N/A	1A:1B
Weight per Gallon A Side	ASTM D1475	9.75 lb/gal
Weight per Gallon B Side	ASTM D1475	8.75 lb/gal
Mixed Weight per Gallon	ASTM D1475	9.25 lb/gal
Viscosity A Side	ASTM D2196	100 cps
Viscosity B Side	ASTM D2196	890 cps
Mixed Viscosity	ASTM D2196	300 cps
Pot Life	N/A	6 minutes
Gel Time	N/A	7 minutes
Demold Time	N/A	1-2 hours
Full Cure Time	N/A	5-7 days

Liquid Properties

Test Method

Test Results

Mix Ratio by Volume

N/A

89.5A:100B

Mix Ratio by Weight

N/A

1A:1B

Weight per Gallon A Side

ASTM D1475

9.75 lb/gal

Weight per Gallon B Side

ASTM D1475

8.75 lb/gal

Mixed Weight per Gallon

ASTM D1475

9.25 lb/gal

Viscosity A Side

ASTM D2196

100 cps

Viscosity B Side

ASTM D2196

890 cps

Mixed Viscosity

ASTM D2196

300 cps

Pot Life

N/A

6 minutes

Gel Time

N/A

7 minutes

Demold Time

N/A

1-2 hours

Full Cure Time

N/A

5-7 days

Thickness Requirements

To create the necessary exotherm to fully cure the part, it cannot be poured less than 1/4 inch thick at room temperature. For thinner pours, you must elevate the mold and molding temperature to 115°F.

Mold Preparation

All surfaces should be clean, dry, and free of dirt, dust, and debris. Release agents are recommended for any molding application to extend the life of the mold, and for prototyping urethane molds, it is a requirement. Heated molds are not recommended for this product or any mold over 120°F because it will cause an uneven cure. These materials are compatible with prepared platinum-cured silicone, metal, and prototyping urethane molds.

Mixing

The material should be at least 65°F before use for proper mixing and application. The B side (Poly) must be premixed once daily before each use, being careful not to introduce extra moisture or air. The A side (Iso) does not need to be premixed.

Prepare a container that is an appropriate size for vacuum degassing. It is recommended to use one with at least 2/3 of head space. Pour 1 part of the A component into 1 part of the B component by weight, 89.5 parts A component to 100 parts B component by volume. Mix until uniform by hand with a gallon paint stick or power mixing equipment. Transfer to a new, clean container and mix again before use. Be sure to scrape the sides and bottom of the container for uniformity.

Post-Cure

After an initial cure of 1-2 hours at room temperature (77°F), you may post-cure in an oven at 180°F for 16 hours to achieve full physical properties faster. Physical properties at room temperature will be delayed for 5-7 days and may not fully develop without post-curing.

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. Once opened, use immediately. If storing after opening, both sides must be nitrogen purged immediately after use.

Precautions

This product contains isocyanate, which may irritate the skin and is toxic if inhaled as particulate matter. Avoid prolonged breathing of vapors or repeated skin contact. Use only with adequate ventilation. It is not UV stable and has no long-term UV testing. Do not add foreign material to the product. See the Safety Data Sheet for complete safety data.