Chrome free organic tannages and molecular level understanding of the tanning process for the production of leather with high hydrothermal stability Samir DasGupta , New Zealand Leather and Shoe Research Association
It is rather strange that today I am talking about chrome-free tannages when I have devoted my whole life to improving the chrome-tanning system. When I was a student, I wondered why chrome tanned leather that stood the boil, did so only for about 1 to 2 minutes. My ambition was to find out how leather could be treated like textile, and we discovered and patented a product and process for improving the hydrothermal stability of chrome-tanned leather. This patent showed how chrome tanned leather could be boiled like textile for an hour without area loss. At LASRA we have also developed LASRA ThruBlu and modified ThruBlu processes to minimise the environmental impact of chrome tanning.
The effect of polymeric phosphate chain length on shrinkage temperature and vegetable tannin penetration rates
The use of linear polyphosphates as pretannages for promoting quick vegetable tannin penetration rates has proceeded without much consideration of the theoretical aspects of polyphosphate chain length mediation of penetration. Polyphosphates are available in a range of chain lengths and empirical evidence suggests those of between 5 and 15 phosphate units as most beneficial. Polyphosphates are known to increase shrinkage temperature and this is shown to occur with increasing chain length. Consideration of spatial dimensions together with experimental evidence allows a theory to be proposed accounting for polyphosphate chain length mediation of vegetable tannin penetration. With small polyphosphates insufficient intermolecular crosslinking occurs to prevent acidic swelling of the fibres and a low degree of permeability results. With very large polyphosphates there is sufficient multipoint intermolecular binding to suppress swelling but the physical size of the bound polyphosphates block the access channels available for vegetable tannin penetration and hence result in slow rates of penetration. Medium chain length polyphosphates exhibit suffficient intermolecular crosslinking potential to inhibit swelling but are small enough to allow the quick passage of vegetable tannins into the interior of the hide.
Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate
Nano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry.