VFI-4278 78 D Polyurethane Casting Plastic

VFI-4278 78 D Polyurethane Casting Plastic is a rigid, two-component urethane plastic for part-making applications that require a fire-retardant material with high heat deflection (HDT). It is typically poured into platinum silicone, metal, or prototyping urethane molds and can be machined with CNC equipment if desired. With an extended pot life, there is ample time to vacuum-degas and cast the material for limited defects in the final part. VFI-4278 can be used to make plastic housings, electronic components, models, and more in a variety of industries.

Physical Properties	Test Method	Test Results
Shore Hardness	ASTM D2240	78 D
Tensile Strength	ASTM D638	6,900 psi
Tensile Modulus	ASTM D638	288,000 psi
Elongation at Break	ASTM D638	18%
Flexural Modulus	ASTM D790	260,000
Izod Impact, Notched	ASTM D256	.89 ft-lb/in
Linear Shrinkage	ASTM D2566	<0.005 in/in
Heat Deflection Temperature (@ 66 psi)	ASTM D648-18	180.9°F ± 2°F
Flame Test	UL 94-V0	TBD
Cure Color	N/A	White

Physical Properties

Test Method

Test Results

Shore Hardness

ASTM D2240

78 D

Tensile Strength

ASTM D638

6,900 psi

Tensile Modulus

ASTM D638

288,000 psi

Elongation at Break

ASTM D638

18%

Flexural Modulus

ASTM D790

260,000

Izod Impact, Notched

ASTM D256

.89 ft-lb/in

Linear Shrinkage

ASTM D2566

<0.005 in/in

Heat Deflection Temperature (@ 66 psi)

ASTM D648-18

180.9°F ± 2°F

Flame Test

UL 94-V0

TBD

Cure Color

N/A

White

Liquid Properties	Test Method	Test Results
Mix Ratio by Volume	N/A	100A:85B
Mix Ratio by Weight	N/A	100A:74.57B
Weight per Gallon A Side	ASTM D1475	9.41 lb/gal
Weight per Gallon B Side	ASTM D1475	10.66 lb/gal
Mixed Weight per Gallon	ASTM D1475	9.91 lb/gal
Viscosity A Side	ASMT D2196	100 cps
Viscosity B Side	ASMT D2196	2,900 cps
Mixed Viscosity	ASMT D2196	600 cps
Pot Life	N/A	19 minutes
Gel Time	N/A	22 minutes
Demold Time	N/A	3-4 hours
Full Cure Time	N/A	5-7 days

Liquid Properties

Test Method

Test Results

Mix Ratio by Volume

N/A

100A:85B

Mix Ratio by Weight

N/A

100A:74.57B

Weight per Gallon A Side

ASTM D1475

9.41 lb/gal

Weight per Gallon B Side

ASTM D1475

10.66 lb/gal

Mixed Weight per Gallon

ASTM D1475

9.91 lb/gal

Viscosity A Side

ASMT D2196

100 cps

Viscosity B Side

ASMT D2196

2,900 cps

Mixed Viscosity

ASMT D2196

600 cps

Pot Life

N/A

19 minutes

Gel Time

N/A

22 minutes

Demold Time

N/A

3-4 hours

Full Cure Time

N/A

5-7 days

Thickness Requirements

VFI recommends pouring the material at least 1/8^th inch thick at room temperature. Thinner pours may not develop the necessary film to cure and develop full physical properties.

Mold Preparation

All surfaces should be clean, dry, and free of dirt, dust, and debris. Release agents are recommended for all molding applications to extend the life of the mold. When working with prototyping urethane molds, release is required. VFI recommends using a silicone-based release agent. Be careful not to overspray the release, as this may result in a shiny/glossy surface or loss of detail transferred to the casting.

We do not recommend using a heated mold or any mold over 120°F with this material. Compatible molds include aluminum, platinum silicone, and prototyping urethane rubber.

Mixing

The material should be between 65°F – 85°F before use for proper mixing and application. Premix the B side (Poly) material before each use. The A side (Iso) does not need to be premixed. Avoid introducing moisture or air into the mix by working in a temperature-controlled environment with low humidity.

The material should be vacuum degassed for bubble-free castings. Prepare a container that is an appropriate size for degassing with at least 2/3 of headspace. Pour 100 parts of the A component into 85 parts of the B component by volume, 100 parts A component to 74.57 parts B component by weight. Thoroughly mix by hand or power mixer while ensuring the material is uniform and homogeneous. 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 3-4 hours at room temperature (77°F), the material must be post-cured in an oven at 180°F for 16 hours to achieve full physical properties. Do not exceed temperatures above 200°F. If you do not post-cure the material, physical properties will be delayed until after 5-7 days at room temperature.

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 does not have any long-term UV testing. Do not add foreign material to the product. See the Safety Data Sheet for complete safety data.