Lead has commonly been used in x-ray devices to limit the amount of radiation exposure for patients and operators. This low-cost and high-gravity compound is among the most effective shields, but we also need to remember that its toxicity makes it very difficult and dangerous to handle.
The Need for a Change
Lead poisoning cases came into the spotlight after the Flint fiasco, and the world soon realized that it needed a substitute for lead, as quickly as possible. A number of governments are also moving away from the use of lead. The EU RoHS directive restricts the use of solders made out of lead in electronics. Medical devices are currently exempted from this list, but only because viable alternate solutions are yet to be available in commercial applications.
Investigating Replacements
A number of high gravity compounds such as tungsten and tungsten alloys are currently being researched. High density plastics have truly begun to take over a number of industries and applications, and it is believed that with additional research, they might even have lead’s manufacturability and convenience. LNP Thermocomp HSG PH1100B, a thermoplastic composite material is currently being projected as that alternative. This compound is believed to offer effective X-ray shielding capabilities and it can also be injection melded into complex designs easily.
LNP Thermocomp HSG PH1100B Vs Lead
Researchers conducted several tests to compare the material to lead in an x-ray shield. Results show that at an equivalent thickness, the HSG PH1100B performed the same, or better, than lead at different voltages. A specific gravity of 11, however, causes high viscosity in the HSG PH1100B when compared to other high density materials used in injection melding applications.
Managing the Viscosity
Researchers recommended the following guidelines to help manufacturers process and manufacture the material.
1. Mold simulations could be inconsistent as the HSG material has special formulations. Therefore, it is essential for an experienced engineer to review the designs. Apart from using standard tool-making practices, standard tool steels can also be chosen for glass fibber applications in order to extend the tool life. Designers also need to use basic plastic-design principles considering anisotropic material properties.
2. Pin gates are recommended to be avoided as they can cause material separation during the first-stage injection. Fans and edge gates offer much better alternatives as they produce lower peak pressure, and this can lead to better aesthetics and over all properties. This also causes lesser shear heating, thereby reducing the chances of separation of the resin and the filler.
3. The wall thickness is recommended to be 3 mm at a minimum. Gate design, vent depth and runner lengths also need special attention to boost performance.
Vast advancements improvements in the field of high density materials and thermoplastic composite materials can encourage designers around the world to choose injection melding solutions in all kinds of applications, including x-ray shielding. The HSG material has already shown that it can offer the same benefits of lead, yet avoid the risks and extra machining that is typically involved while using lead.
With the help of these materials, it is entirely possible for manufacturers around the world to come up with new technologies and better equipment. It might be early days in the x-ray shielding department, but the results do look incredibly promising!
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