PT7240 & PT7250 Soft, Flexible Urethane Elastomers
DESCRIPTION
The Shore A-40 and A-50 urethane systems described here are tough, soft, highly resilient polyurethane elastomers that have good handling characteristics and excellent cured properties. These high physicals make them ideally suited for applications such as bumpers, pads, flexible molds or soft parts where a high degree of flexibility and toughness is required. Their relatively high tensile strengths make them good performers for complicated masking or holding fixtures where the tooling needs to be stretched to apply and remove. These two systems are very low in viscosity, so they mix and pour with great ease. The will duplicate the finest detail without trapping air. They are very clear, and light amber in tint, so they can be easily pigmented if desired for a broad range of finished part colors.
PRODUCT SPECIFICATIONS
| Shore A-40 System | Shore A-50 System | ||||
| PT7240 A | PT7240 B | PT7250 A | PT7250 B | ASTM Method | |
| Color | Amber | Amber | Light Amber | Light Amber | Visual |
| Viscosity | 1175 cps | 25 cps | 1600 cps | 20 cps | D2392 |
| Specific Gravity, gms./cc | 1.04 | 1.08 | 1.04 | 1.08 | D1475 |
| Mix Ratio, by Weight | 100 : 75 | 100 : 70 | PTM&W | ||
| Pot Life, 4 fl oz Mass @ 77°F | 20 – 25 min. | 18 – 22 min. | D2471 |
HANDLING & CURING
Generally, with polyurethane elastomers, full properties are developed
in 7 days at room temperature (75°F). Temperatures below 75°F will
lengthen the cure time, and if the ambient temperature is below 60°F,
additional heat may be necessary for proper cure. Elevated temperatures
will accelerate the cure of urethanes, but care must be taken if a
higher temperature is used to cure the material. Generally, the higher
the curing temperature, the greater the final cured shrinkage. When heat
curing for more rapid processing, to best control shrinkage, the
casting should be allowed to set for 12 to 18 hours at room temperature
before an oven post cure. A typical accelerated curing cycle, therefore,
would be: Allow to gel on the pattern for 12 to 18 hours at room
temperature (70°F to 80°F), then post cure for a minimum of 8 hours at
150°F to 165°F and allow to cool before demolding.
PACKAGING WEIGHTS
| Gallon Kit | Pail | |
| PT7240 Part A | 8 lb. | 40 lb. |
| PT7240 Part B | 6 lb. | 30 lb. |
| Kit | 14 lb. | 70 lb. |
| PT7250 Part A | 8 lb. | 40 lb. |
| PT7250 Part B | 5.75 lb. | 28 lb. |
| Kit | 13.75 lb. | 68 lb. |
Inasmuch
as PTM&W Industries, Inc. has no control over the use to which
others may put material, it does not guarantee that the same results as
those described herein will be obtained. The above data was obtained
under laboratory conditions, and to the best of our knowledge is
accurate. This information is presented in good faith to assist the
user in determining whether our products are suitable for his
application. No warranty or representation, however is intended or
made, nor is protection from any law or patent to be inferred, and all
patent rights are reserved. Before using, user shall determine the
suitability of the product for his intended use, and user assumes all
risk and liability whatsoever in connection therewith. In no event with
PTM&W Industries, Inc. be liable for incidental or consequential
damages. Buyer’s sole and exclusive remedy in such instances shall be
limited to replacement of the purchase price.
TYPICAL MECHANICAL PROPERTIES
| PT7240 A/B | PT7250 A/B | ASTM Method | |
| Mix Ratio, by Weight | 100 : 75 | 100 : 70 | PTM&W |
| Color | Light Amber | Light Amber | Visual |
| Mixed Viscosity, @77°F, centipoise | 825 cps | 950 cps | D2393 |
| Working Time, 4 fl. oz. Mass @ 77°F | 25 min. | 20 min. | D2471 |
| Cured Hardness, Shore D | 40 A±5 | 50 A±5 | D2240 |
| Shrinkage, in/in, Mold #1, Vol: .053 Gal | .0006 | .0009 | D2566 |
| Specific Gravity, grams, cc | 1.057 | 1.056 | D1475 |
| Specific Volume, cu. in./lb. | 26.2 | 26.2 | D792 |
| Tensile Strength, psi | 800 psi | 775 psi | D638 |
| Elongation at Break, % | 525 % | 450 % | D638 |
| Tear Strength, Die C, pli | 180 pli | 165 pli | D624 |
| Compression Set, Method B | 45 % | 30 % | D395 |
| Bashore Rebound | 65 % | 64 % | D2632 |
| Taber Abrasion, H18 Wheel, 1000, grams, 1000 cycles, mg loss | 6 mg. | 5 mg. | D1044 |
SAFETY & HANDLING
PTM&W epoxy products are made from raw materials carefully chosen to minimize or even eliminate toxic chemicals, and therefore offer the user high performance products with minimum hazard potential when properly used. Generally, the PTM&W epoxy resins and hardeners will present no handling problems if users exercise care to protect the skin and eyes, and if good ventilation is provided in the work areas. However, all epoxy resins and hardeners can be irritating to the skin, and prolonged contact may result in sensitization; and breathing of mist or vapors may cause allergenic respiratory reactions, especially in highly sensitive individuals. As such, avoid contact with eyes and skin, and avoid breathing vapors. Wear protective rubber apron, clothing, gloves, face shield or other items are required to prevent contact with the skin. In case of skin contact, immediately wash with soap and water, followed by a rinse of the area with vinegar, and then a further wash with soap and water. The vinegar will neutralize the hardener and lessen the chances of long term effects. Use goggles, a face shield, safety glasses or other items as required to prevent contact with the eyes. If material gets into the eyes, immediately flush with water for at least 15 minutes and call a physician. Generally, keep the work area as uncluttered and clean as possible, and clean up any minor spills immediately to prevent accidental skin contact at a later time. Keep tools clean and properly stored. Dispose of trash and empty containers properly. Do not use any of these types of products until Material Safety Data Sheets have been read and understood.