Crosslinked polyethylene foams are a family of thermoplastic polyolefin foam materials. They are characterized by being closed-cell and having a small, uniform, cell structure. The cross-linking of these foams at the molecular level is achieved by either a chemical or irradiation process.
Both cross-linking processes serve to create bonds between the polymer chains which in turn form a three-dimensional structure.
It is the three-dimensional cross-linked structure of these materials that significantly improves their physical properties. These include:
The inherent properties of these polyethylene-based materials also make them resistant to chemical degradation. These materials are closed-cell and have low water absorption characteristics and the lower densities have good buoyancy characteristics.
Cross-linked polyethylene foams are manufactured using both low-density and high-density polyethylene resins. The attributes of the foams can also be modified by the addition of vinyl acetate. Adding vinyl acetate creates a polyethylene/vinyl acetate copolymer with increased softness, flexibility, and resilience. The higher the percentage of vinyl acetate in the copolymer the softer the resulting foam will be.
Cross-linked polyethylene foam formulations can also be customized for different markets and end-uses. Antibacterial, static-dissipative, and fire-retardant agents can be added to the foams in order to produce materials with characteristics that are beneficial in specific market segments.
Cross-linked polyethylene foams are manufactured in both continuous roll and bun forms. Cross-linked foam rolls are extruded at a thickness from 1/32” to approximately .5” thick. The most common roll width is 60”.
The rolls can be manufactured in densities ranging from 2 lb/cubic foot to 20 lb/cubic foot. Flextech distributes and fabricates Sekisui Voltek’s Volara and Armacell’s Oletex roll foam product offerings.
Cross-linked foam buns are manufactured in a range of thicknesses, width, and lengths depending on the material manufacturer and specific density and grade of material. Buns can come in thickness of 1” to 4” and be 40” to 60” wide and 48” to 72” long. The density of the bun foams can range from 1.5 lb/cubic foot to 18 lb/cubic foot. Flextech distributes and fabricates cross-linked polyethylene buns from Zotefoam’s Azote product line, Sekisui Voltek’s Minicel products, and Armacell’s Oletex brand.
The thermoplastic nature of cross-linked polyethylene foams allows them to be heated and three-dimensionally shaped. This process is generally referred to as thermoforming. Flextech utilizes three unique foam thermoforming processes to create three-dimensional formed parts. The three methods are compression molding, encapsulation molding, and vacuum forming.
Water Resistance – Cross-linked polyethylene foam is inherently water resistant due to its closed-cell structure. The low moisture absorption and vapor transmission properties of this material make it ideal for use in applications where it is exposed to any moisture in the environment.
Thermal Conductivity – Low density (2lb/cubic foot -4 lb/cubic foot cross-linked polyethylene foam have good thermal conductivity values which makes them a superior insulation material. Their insulation properties makes them useful in minimizing condensation and improving machine efficiency by reducing energy loss.
Chemical Resistance – Cross-linked polyethylene foams have exceptional chemical resistance properties. Most common chemicals will not affect or degrade the material. This makes them suitable for use in many applications where exposure to chemicals is a concern.
Non-Abrasive – The small, fine cell-structure of cross-linked polyethylene foam makes it perfect for protecting Class A surfaces. Class A surfaces are surfaces which are visible to the consumer and affect is appearance. Cross-linked foams will not damage Class A surfaces and are therefore ideal for protective packaging applications.
Shock-Absorption– Cross- linked polyethylene foams have superior cushioning and shock absorption properties. This makes them suitable for use in packaging and protective padding applications.
Durable and Resilient – Cross-linked polyethylene foams are durable and have puncture and tear resistant materials. They will also take repeated compressions and deformations without losing their effectiveness.
Buoyancy – Low-density cross-linked polyethylene foams have considerable air entrapped in their closed-cell structure. This makes them ideal for use in marine and floatation applications.
Mold/Mildew Resistant– The closed-cell structure of cross-linked polyethylene foams don’t allow moisture to be absorbed. Therefore, they are more mold/mildew resistant than other materials. Polyethlene foams also don’t promote bacterial growth.
Ease of Fabrication – Cross-linked foams can be skived to thickness, die cut, waterjet cut, machined, laminated, vacuum formed, and compression molded. The ease of fabrication allows these materials to be used in a wide variety of end-use applications.
Because of their exceptional physical properties, cross-linked polyethylene foams are utilized in a wide range of markets and applications.
Personal Protection Market – Cross-linked foams are used for body armor padding, helmet pads, ballistic plate trauma pads, industrial safety padding and many other applications in military, law enforcement and tactical gear.
Medical Market – Cross-linked foams are used for medical device packaging, patient interfaces for diagnostic and therapeutic devices, medical device components, orthopedic device padding, medical consumables, suture holders, support and positioning components.
Industrial Market – Cross-linked foams are used for gaskets and seals, thermal insulation, sound absorption, vibration dampening, packaging, material handling, case inserts, expansion joints, foam tapes and many more.
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