Medical material quality advances have been taking hold of the medical device and plastics injection mold business. Plastics come in many shapes and forms and are used from children’s toys to Space Craft. I was first was introduced to plastics in the 1960’s, when I was working on the repair and overhaul of nuclear powered submarines. The nose of each submarine is made of a plastic; it is actually a composite material (fiberglass) that incases an array of transducers that allow the submarine to see where the submarine is going. It is based on the Dolphin’s world of sonar communications and ability to identify objects (food) at great distances. We ultrasonically inspected the sonar dome of composite material for de-lamination as a final manufacturing inspection. In the event of in-service damage to the sonar dome we would use ultrasonic’s for the detection of delaminating, x-ray or gamma ray inspection cannot easily detect laminations.
Today I am working with a material called PEEK (PolyEtherEther-Ketone). First known as PAEK it was used to replace metal bearings in food processing equipment because PEEK would not cause damage to the body if digested.
PEEK was invented by a company called VICTREX® PEEK® mainly for medical; today PEEK type products are use in Automotive, Marine, Oil and Petroleum environments, Electronics, Aerospace and for many other General Industrial uses. In the medical industry PEEK is used to replace metal implants, especially in orthopedics and trauma. PEEK resins, coatings and films conform to the FDA requirements and are considered safe for repeated use in food contact, and is not rejected in implanted into the body for spine or joints.
Some of the Medical and Spinal benefits of PEEK:
- Bone-like material has a modulus that stimulates bone healing
- Resists creep; a deformation of the implant that changes its shape when subject to weight over time
- Has a high compression strength
- Has a longer implant life and reduced likelihood of inflammation problems
- Can withstand a high range of motion over time without wearing out
The thermal conductivity of polymeric materials is lower than that of metals. This means that when you heat metal, the metal dissipates the heat, or rapidly moves the heat throughout the metal. Polymeric materials do not dissipate the heat well. The heat build-up during machining (turning, milling, drilling, reaming) operations is rapid. A cooling fluid is used to remove some of the heat generated by working the material. Water is generally recommended for use with all the PEEK polymer based materials.
Annealing PEEK and other Polymeric materials after working is used to refine the crystalline stricture, remove any thermal history, limit dimensional changes at high temperatures and can be used to remove stress. The annealing method depends on the chemical and mechanical properties desired by the customers and the requirements necessary to achieve specific characteristics of the part or component
We use similar Nondestructive inspection methods during the processing and final inspections on plastic as we use on metal and look for the similar type discontinuities. Elimination, porosity, gas pockets, foreign material (FOD), cracks, etc. We even have to Heat Treat some plastic products because of the thermal conductivity..
Destructive testing on PEEK Material is also similar to metal and tests performed are used to determine characteristics like; hardness, elasticity, tensile strength, elongation, fracture toughness, melting point, heat transfer and linear expansion of coefficients.