Polymer Basics for Elastomers

 

In Brief

The word elastomer is derived from the term 'elastic polymer.' Elastomers are rubbery materials composed of polymers that can return to their original shape after being stretched even to great extents.

Characteristics and Properties of Elastomers

A typical elastomer has a chemical composition of oxygen, hydrogen, and silicone. Elastomers have approximately 3,000 to 10,000 repeating units, and thus high polymer chain flexibility. Additionally, they are biocompatible and chemically inert.
Elastomers are the ideal raw material for making numerous medical devices such as artificial ears and body implants. Thermoplastic elastomers are low modulus and flexible materials that allow for extensive stretching to double or more of their original length. Their properties and characteristics range between those of plastics and rubber. Thermoplastic elastomers are used in several medical applications, such as surgical films, heat shrink tubing, disposable gloves, and eye drop bottles.

Production Methods

Elastomers can be manufactured in several ways, depending on the compound and the desired outcome. The processing method can be classified as a low-temperature curing process (LTV) or a high-temperature curing process (HTV) based on the type of polymer used. Curing refers to the process of forming crosslinks between silicon and rubber before the fabrication into real products is done. Some of the fabrication methods include:

  • Extrusion - This fabrication process is used to form a silicone elastomer product by using a die. This method involves feeding raw materials consisting of silicon, binders, rubber, and catalyst into an extruder at high temperatures. The material is then pushed through a die of a specific shape before post-curing it.
  • Injection molding - Injection molding is used to make complex shapes. Cured raw materials are injected into a mold that ranges from simple to complex shapes. The material is then given time to cool before it is removed from the mold as a finished product.
  • Compression molding - This method involves the creation of products by putting a silicone rubber into a heated mold. The mold cavity is sealed with a heated plunger that applies a high amount of pressure. The materials will eventually melt to flow through the mold cavities. The high temperature is maintained until the product is fully cured.

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Common Uses in Medical Devices and Life Sciences

Health care facilities use several varieties of elastomers at all levels. Elastomers are chosen for their outstanding sterility, low leaching level, and biocompatibility. Some standard medical devices made from elastomers include:

Gloves

Latex in gloves is produced from natural rubber. These medical devices are common in the medical field. Besides, non-latex gloves are also made from elastomeric materials.

Implants and Prosthetics

These critical medical devices are made from medical-grade elastomers. The manufacturing process makes use of the material's flexibility attributes to achieve the desired results. Essentially, implants require some level of flexibility for ultimate comfort.

Medical Tubing

There has been a significant increase lately in the application of elastomers in medical tubing. There are several explanations for this new trend. Elastomers are FDA compliant, easy to sterilize, and recycle. They also boast of a low coefficient of friction, low opacity, and high transparency.

Syringe Gaskets

Syringe gaskets benefit from elastomer compounds. Its applications can be found in syringe plunges, forming a leak-proof seal with the syringe barrel. The elasticity typically guarantees no backflow against the syringe's sides, and the material doesn't succumb easily to pressure when the plunger is pushed.

Oxygen Masks

Oxygen masks made from elastomers benefit from excellent elastic properties. These properties allow for a comfortable fit and gentle natural molding to facial curvature.

The Best Method of Sterilization

Sterilizing medical equipment is an essential element of modern medicine to ensure the safety of patients, medical personnel, and the environment. There are specific sterilization methods for elastomer devices approved by the FDA, and the method chosen will depend on the properties of each medical device being sterilized. These methods include:

Ethylene Oxide (EtO)

This method is ideal for sterilizing medical instruments with low heat tolerance and involves immersing the device in a chamber of ethylene oxide gas prior to aeration.

Hydrogen Peroxide

In this method, devices are placed in a sterilization chamber vacuumed and filled with hydrogen peroxide vapor. Afterward, they are removed and then aerated before being used.

E-beam Radiation 

This type of sterilization uses ionized energy that has low penetration and high dose rate to rid pathogens. Typically, beams of electrons produced by an accelerator are focused on the medical device being sterilized.

Dry Heat

Dry heat sterilization utilizes hot air and heat on the medial equipment being sterilized. Dry heat sterilization is arguably one of the most efficient methods to sterilize polymer-made medical equipment. The heat typically reaches all surfaces of an assembled product and thus highly effective.

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