Nov 2016 Issue

Have you ever wondered why dentists put a lead blanket on patients before performing X-ray scanning of their teeth?  It’s because X-rays are considered carcinogenic by World Health Organization and exposure to X-rays should be minimized even when medically indicated.  Of course, harmful effects from occasional chest or teeth X-ray scans are limited.  However, healthcare professionals and those at border crossings operating scanners on a daily basis may have serious health problems arising from long-term exposure.  Protective gear or shielding curtain is thus essential to block off some radiation and reduce the dose they receive.  There are lead-rubber shielding aprons, suits, gloves and shoe covers in the market.  Yet, such garments and accessories also pose potential danger of a different kind because toxic lead pellets may be exposed if the rubber is damaged.  In light of this, Dr Bin Fei, Associate Professor, Institute of Textiles & Clothing, and his research team have been working on an alternative shielding material that is safer to use, lighter in weight and less bulky in volume.  The resulting textile is also more flexible and theoretically, it can be recovered repeatedly with unlimited life span.

Lead: toxic chemical to be phased out

U.S. Department of Health and Human Resources and the Environmental Protection Agency Europe (EPA) have determined lead to be a toxic chemical and would like to see it replaced.  It also ranks second on the U.S. Government's Hazardous Substances Priority List.  Possible complications from lead poisoning include behavioural problems, learning disabilities, seizures, and even death.  With growing health, safety and environmental concerns over the mining, processing, handling and disposal of lead, more stringent regulations regarding the sale and use of lead products should be expected.

For this reason, Dr Fei chose the metal tungsten in place of lead to make his novel shielding material.  He explained, “Tungsten is one of the densest naturally occurring elements.  It is non-toxic and non-reactive and can be effectively blended with plastics to produce a green material with better shielding attenuations than lead.  Tungsten has been used in healthcare equipment for years proven to be safe and effective.”

Elastic polyurethane/tungsten (WPU) composite

Dr Fei’s idea is to combine tungsten and polyurethane.  Through a number of pollution-free processes, the resulting polyurethane/tungsten (WPU) composite is made into a continuous sheet of textile that can be cut and sewn right away without any delay.  Besides being safer and more effective in shielding radiation than lead-rubber, WPU is also lighter, less bulky and more flexible.  “WPU is substantially more durable than lead rubber.  Typically, a lead rubber garment has a life span of 2 years whereas WPU is expected to last for 3 years.  When a lead rubber garment is damaged, the lead cannot be recovered and recycled.  Yet, a WPU garment can be patched and fixed with a heat press indefinitely.  Finally, disposal is also a problem because lead rubber cannot be disposed through normal channels.  On the other hand, WPU, when it needs to be disposed of after repeated patching, would not contaminate the landfill and underground water,” said Dr Fei.

The novel shielding textiles against high energy rays won a silver medal at 2016 International Invention Innovation Competition in Canada (iCAN 2016).