Scientists have developed a method of making wood transparent. David Taylor reports It sounds like an April Fools’ joke – in fact, the BBC News website recently declared that it should be one – but transparent wood is not a joke, it’s a real thing. Research scientists at the KTH Royal Institute of Technology in Stockholm, Sweden, recently announced that they had succeeded in creating “optically transparent wood” through a process in which the light-absorbing lignin component is chemically removed and the resulting “delignified nanoporous wood template” impregnated with pre-polymerised methyl methacrylate resin. By matching the refractive index of the MMA resin to that of the delignified cellulose fibres, the scientists produced optically transparent wood in thicknesses up to 8mm. Lars Bergland, who led the research, explains that “when the lignin is removed, the wood becomes beautifully white. But because wood isn’t naturally transparent, we achieve that effect with some nanoscale tailoring”. A paper (“Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance”) published by the Stockholm team in the American Chemical Society journal Biomacromolecules, notes that cellulose fibres have already been used to create transparent paper through cellulose dissolution and regeneration, polymer impregnation or decreasing the cellulose fibrous diameter to the nanoscale. Japanese scientists have even done something similar with crab-shell, removing the inorganic calcium carbonate and the protein ‘glue’ and re-impregnating the remaining nanoporous chitin structure with a transparent resin. The Swedish team took samples of balsa wood and extracted the lignin with a solution of sodium chlorite with an acetate ‘buffer’ at 80oC. After the lignin had been dissolved, the samples were washed in de-ionised water and then dehydrated using ethanol and acetone. The remaining nanoporous wood template was impregnated with the prepolymerised MMA solution under vacuum for 30 minutes before being baked in an oven at 70oC for four hours. The refractive index of the prepolymerised MMA was carefully matched to that of the delignified cell walls to maximise transparency. Delignified wood, though white, is not transparent because light is scattered by the difference in refractive index at the interface between the cell walls and the air. Replacing the air with a resin that has the same refractive index as the cell walls renders the material transparent. This is all very clever, but why bother? Why go to all the trouble of making wood transparent when we already have glass and various transparent plastics at our disposal? The answer, it seems, lies in energy efficiency and cost. The built environment accounts for 30 – 40% of total energy consumption, says the research team. Solar energy is free, inexhaustible and clean and hence “light-transmitting buildings can also contribute to reduced demand since artificial light can be partially replaced by natural light”. Wood, the researchers point out, is the most widely used biological building material and has the advantage of having good strength, low density and low thermal conductivity. It is also relatively cheap. If you can enhance these qualities by adding something new – in this case, transparency – you broaden the range of applications for the material. Transparent wood is more thermally-efficient than glass and its main component – cellulose – is renewable. After all, it’s made out of trees with only relatively little synthetic resin added. Different types of wood will yield products of different transparency and ‘haze’ (the amount of light diffusion within the material). The Stockholm team has achieved transparency of up to 85% and haze of 71% in 1.2mm-thick wood samples. “This high haze is attractive in solar cell applications,” explain the scientists. “Light will be trapped in the solar cell for a longer time due to light scattering caused by the wood tissue. Longer trapping time means better interaction between light and the active medium which can lead to better solar cell efficiency.” The combination of the PMMA and delignified wood template produced a strong, tough material – twice as strong as neat PMMA, say the researchers. “Therefore, this nanostructured biocomposite is both a structural (mechanical properties) and a functional (optically transparent with haze) material,” concludes the team’s report. “Optically transparent wood is an excellent candidate for lightweight and low-cost structures in light-transmitting buildings and for transparent solar cell windows.” This article was published on 18 Oct 2016 (last updated on 18 Oct 2016). Source link

Book Course HSL is to run a 5 day course on Ergonomics. 11 – 15 April 2016 Introduction Every year, 35 million days are lost to British industry as a result of accidents and ill health caused by work activities. A large number of these accidents are due to a lack of thought and planning concerning the use of our everyday systems. The course provides the ergonomics theory and techniques used to maximize the design of the tools, tasks and workplaces for improved comfort, safety and performance of the workforce.   The techniques cover both the physical and psychosocial aspects of a workplace design, following relevant HSE guidance and approaches to assess and reduce risks. What will the course cover? Ergonomics principles, methods and techniques Human Beings – physical and psychological factors Applied Anthropometry Workplace Design and DSE Manual Handling risks, assessments and controls Upper Limb Disorders – risks, assessments and controls Stress Management Influencing behaviour User investigation methods, such as interviews, questionnaires and focus groups Task Analysis Controls and Displays Environmental Factors – Lighting, Floors and footwear, Noise Who should attend? The course is suited to all who have an interest in workplace ergonomics and wish to understand more about possible interventions that could be made to assess and improve worker comfort, safety and performance. No previous ergonomics or MSD experience is required. Who will present? Matthew Birtles – Matt has been a practising ergonomist for 13 years. His work at HSL has spanned various industries and topics, such as welding and foundry work, fairground ride safety and other leisure industry projects, food production, railway and train cabin design, furniture manufacturing, construction health and safety and ergonomics in health care. He also co-authored and presents, material on MSD training for HSE inspectors, and manual handing and the material for this Ergonomics course for the public. Matt has particular interest in the prevention of musculoskeletal injury and the design of fit for purpose ergonomic solutions to workplace problems. Liz Brueck is a physicist with considerable experience in noise measurement and instrumentation, and hearing protection (including level dependent protectors). She represents HSE on the standard committees for electroacoustic equipment and hearing protectors, and represents the UK on the ISO working group for the acoustic testing of hearing protectors. Victoria Bennett is a psychologist with experience conducting literature reviews in behavioural change and worker engagement, as well as developing and testing a toolkit looking to provide construction SME’s with the tools and techniques necessary to improve their health, safety and business performance. Victoria has also developed and delivered a comprehensive training course on behavioural change, and developed two further training courses on work-related violence and wellbeing. Jane Hopkinson is a psychologist working in HSL’s Social and Organisational Factors section. Jane’s particular area of expertise is in risk communication, knowledge, attitude and behaviour changing techniques and the management of work related stress and how these can be applied with regard to health and safety. Jane has been responsible for developing and delivering HSL training courses on the topics of behaviour change, wellbeing and work related stress. Comments & Feedback “Just a short note to thank you for an excellent course last week, it was great, one of the most useful and interesting courses that I have ever been on.”Roger Barnes, BAE Systems Venue The course will be run at the HSL laboratory in the spa town of Buxton. Buxton is in the heart of the Peak District and has good links to mainline train stations and Manchester International Airport. Details of hotels in the Buxton area can be found at www.visitpeakdistrict.com. Cost The cost of the course is £1,195 per person  (includes course notes, lunches, refreshments and a course dinner on the second night). Book Course Please note the invoice option is not available within 4 weeks of the course date, or for overseas customers. For further dates and additional information email: training@hsl.gsi.gov.uk or contact the Training & Conferences Unit at HSL directly on +44 (0)1298 218806. Back to Health & Safety Training Courses Source link