TASK® 8

TASK® 8 is a heat resistant polyurethane resin system made specifically for prototyping / casting applications which require thermal resistance of up to 263°F /129°C.

Features

TASK® 8 offers the convenience of a 1A:1B mix ratio and has a very low viscosity, so it is easy to mix and pour. Plastic cures quickly to a Shore 80D and exhibits good physical and performance properties. Heat curing this material is necessary to attain optimal heat resistance. See “Heat Curing” section for curing schedule details.

Applications include making machine housings, thermo-forming and general prototyping / casting.

Instructions

Materials should be stored and used in a warm environment (73° F / 23° C). This product has a limited shelf life and should be used as soon as possible. All liquid urethanes are moisture sensitive and will absorb atmospheric moisture. Mixing tools and containers should be clean and made of metal, glass or plastic. Mixing should be done in a well-ventilated area. Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk.

Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.

Applying A Release Agent - A release agent is necessary to facilitate demolding when casting into or over most surfaces. Use a release agent made specifically for mold making (Universal® Mold Release or Ease Release® 200 available from Smooth-On or your Smooth-On distributor). A liberal coat of release agent should be applied onto all surfaces that will contact the plastic.

IMPORTANT: To ensure thorough coverage, lightly brush the release agent with a soft brush over all surfaces. Follow with a light mist coating and let the release agent dry for 30 minutes.

Most silicone rubber molds usually do not require a release agent unless casting silicone into the mold. Applying a release agent, however, will prolong the life of the mold.


MEASURING & MIXING...

Shake or stir both Part A & Part B before dispensing. After dispensing equal amounts of Parts A and B into mixing container, mix thoroughly. Stir slowly and deliberately making sure that you scrape the sides and bottom of the mixing container several times. Be careful not to splash low viscosity material out of the container.

Remember, TASK® 8 will set up quickly. Do not delay between mixing and pouring.


IMPORTANT: Shelf life of product is reduced after opening. Remaining product should be used as soon as possible. Immediately replacing the lids on both containers after dispensing product will help prolong the shelf life of the unused product. XTEND-IT® Dry Gas Blanket (available from Smooth-On) will significantly prolong the shelf life of unused liquid urethane products.


Pouring - Pour your mixture in a single spot at the lowest point of the containment field and let the mixture seek its level. This will help minimize air entrapment.

For Best Results . . . Best results are obtained using a pressure casting technique. After pouring the mixed compound, the entire casting assembly (mold, dam structure, etc.) is placed in a pressure chamber and subjected to 60 PSI (4.2 kg/cm2) air pressure for the full cure time of the material.

Curing - TASK® 8 will cure in 10-15 minutes depending on mass and mold configuration. Non-hazardous fumes, which may be visible as this product starts to “gel” and cure, will dissipate with adequate (room size) ventilation.

Heat Curing - For maximum physical properties and higher heat resistance, TASK® 8 should be heat cured according to the following cure schedule:

Temperature Duration
Room Temp. (72°F / 23°C) 1 hour
150°F / 65°C 2 hours
212°F / 100°C 2 hours
265°F / 130°C 2 hours

Performance - Cured plastic is rigid and durable. It resists moisture, moderate heat, solvents, dilute acids and can be sanded, machined; primed/painted or bonded to other surfaces (any release agent must be removed). If sanding or machining, wear dust mask or other apparatus to prevent inhalation of residual particles. Plastic can be displayed outdoors after priming and painting. Unpainted castings will yellow when exposed to ultra-violet light.

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