Engineered Elastomer: Pentathane®
Molded Dimensions is a custom molder of cast polyurethane and molded rubber. Pentathane® is MD's trade name for our custom, cast polyurethane formulations.
Pentathane® is known for:- Outstanding physical properties
- Advantages over metal, rubber, and plastic
- Wide range of part applications and industries
- Compatibility to various polyurethane molding methods
- Ability to be finished in numerous ways
- Low to mid volume production
- Diversity in part size
Outstanding Physical Properties
- Wide range of hardnesses
- High load-bearing capabilities
- High abrasion resistance
- Low coefficients of friction
- Good resistance to gas, oil, alkali and acid
- Tear resistance and toughness
The two main types of cast polyurethanes, Polyester and Polyether, offer specific properties:
Ester- Solvent, Oil and Fuel Resistance
- Abrasion resistance
- Excellent Mechanical Properties
- Dry heat resistance to 200F
- Vibration Dampening
- Higher Split Tear Strength
Ether
- Superior Rebound Properties
- Low Temperature Flexibility
- Excellent Hydrolytic Stability
- Excellent Mechanical Properties
- Resistance to Dynamic Heat
- Reduced frictional properties
Key Advantages of Cast Polyurethane
Typical material competitors for polyurethane molding applications are metal, rubber, and plastic. When considering a polyurethane vs rubber, metal or plastic, it’s important to recognize the advantages polyurethane brings:
vs Metal:- Less weight
- Less Noise
- Better wear
- Corrosion resistance
- Cheaper fabrication
- Non-sparking
- Non-conductive
- Impact resistance
vs Rubber:
- Abrasion resistance
- Cut and tear resistance
- Higher load bearing
- Harder durometer range
- Clarity, Translucence
- Non-marking, non- staining
- Pourable, castable
- Ozone resistance
- Micro organism resistance
- High dampening
vs Plastic:
- Non-brittle
- Abrasion resistance
- High elongation
- Elastomeric memory
- Impact resistance
- Lower tooling cost
Typical Applications
- Rollers
- Scrapers
- Gears
- Liners
- Couplings
- Wheels
- Impellers
- Insulators
- U Cups
- Squeegees
- Plates
- Cams
- Bumpers
- Fans
- Seals
- Mounts
- Plugs
- Guides
- Grippers
- Isolators
- Guide Rings
- Bushings
- Cushions
- Gaskets
- Wear Plates
- Springs
- Wipers
Molding Technologies
Polyurethane (PU) can be molded in a variety of ways — open-cast, compression, spin cast and low-pressure injection. Polyurethane tooling is lower cost due to the simplicity of the tooling, the ability to gravity fed individual cavities, and the constant temperature processing, requiring no cooling lines.- Open Cast Polyurethane Molding - Because of the liquid nature of the uncured resin, PU polyurethane parts are often molded using an open-cast process. The polymer and curative agents are premixed and poured into an open cavity of a mold. After the parts reach "green strength" or are partially cured, they are demolded and moved to a secondary post cure oven. Open-cast molded parts are subject to a looser tolerance on the open-cast surface and may require a secondary cutting or machining operation if a tighter tolerance is needed.
- Compression Polyurethane Molding - Polyurethane can be cast using a compression or closed mold process. The polymer and curative are premixed and poured into the open mold. The mold is overfilled with raw material, helping to drive out air as the mold is closed and placed under pressure. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven. In this process, all surfaces are controlled by the closed mold.
- Spin Casting Polyurethane Molding - The polymer and curative are premixed and poured into a spinning, closed mold. This process is designed to remove air that can be trapped during molding. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven. Like the open cast urethane molding process, a secondary machining process may be needed to remove the risers or gates.
- Low Pressure Injection Polyurethane Molding - In the polyurethane injection molding process, the polymer and curative are premixed and injected under low pressure into a closed mold. Bleeder vents are used to allow the excess air to escape during the injection process. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven.
Insert Molding
When additional mechanical structure is needed in a component, cast urethane is easily overmolded onto a substrate. A variety of metals including carbon steel, aluminum, stainless, brass and bronze can be used. Non-metallic, rigid materials, such as fiberglass and glass-filled nylon, are also candidates.Urethane may be either mechanically or chemically bonded to an insert. Mechanical bond is the encapsulation of the substrate without the use of a secondary adhesive. A chemical bond utilizes an adhesive system to ensure an unyielding bond between the substrate and urethane.
Finishing Operations
- Deflashing - During the custom polyurethane molding process uncured PU can seep between plates causing excess material extending from the part. After the parts are cured, the thin flash or excess material is removed in a batch process called cryogenic deflashing. The parts are frozen using liquid nitrogen, tumbled and blasted with media to remove the flash while retaining the part integrity.
- Machining and Grinding - Machining or grinding can be used to achieve tighter tolerances than molding alone can create.
- Die Cutting - Die cutting can be used to create a smooth, clean-cut edge as is often required for squeegee blades.
- Knifing - Knifing is a manual operation whereby excess, unwanted material like flash or overpour is removed from the part by removal with a blade.
- Kitting - Products may be special packaged, labeled or assembled per customer requirements.
- Inventory Programs - Flexible systems, including KANBAN, are set up to hold raw, WIP and/or finished goods inventory depending on customer need.
Annual Volume Sold
MD has low- to mid-volume polyurethane molding production capabilities. Some of our customers, including military, often only require small production runs, while other customers require weekly releases and a supporting Kanban program to keep them in supply. The systems and methodologies we learn from larger, more structured companies can be applied to benefit customers across the board.Part or Product Size
Precision mechanical polyurethane components range in size from 50 grams to over 60 pounds. In-house production utilizes a range of hot table and oven sizes for open-cast molding, with our largest ovens measuring 10' square, and presses up to 24" square for compression molding.Industries Served
Our diverse customer base crosses many industries, as we like to say, "from medical to mining." The engineering expertise we gain based on the range of parts we manufacture benefits all customers with high-quality, consistent products meeting application requirements. In addition, the knowledge and experience gained from servicing large-scale customers with high service and quality requirements benefits all customers, no matter their size or industry.Download our Pentathane brochure
