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Intumescent FRs (IFRs)
Published in Asim Kumar Roy Choudhury, Flame Retardants for Textile Materials, 2020
Inorganic acids such as Ammonium polyphosphate (APP) must be available for the dehydration action with the char former (PER) at a temperature below the temperature at which the degradation of the polymeric materials begins. Then, the formation of the effective char must occur via a semiliquid phase (high viscous material) that coincides with gas formation and expansion of the surface (bubble-gum effect). This action must occur before the charring liquid solidifies. Gases released from the degradation of the intumescent material and/or of the polymeric material should be trapped and have to be diffused slowly in the highly viscous molten material in order to create a layer with the morphological properties of interest. Thus, it is essential to examine carefully the dynamic viscoelastic properties of the intumescent shield, because control of the melt rheology is necessary to obtain a multicellular and highly expanded structure. Moreover, the mechanical integrity of the char is a crucial parameter because it has to resist external stress. In short, an intumescent formulation has to be optimized in terms of physical (e.g., char strength, expansion, viscosity) and chemical (thermal stability, reactivity) properties in order to form an effective protective char that can protect its host polymer (reaction to fire) or a substrate such as steel or wood (resistance to fire) (Bourbigot and Duquesne, 2010).
Mediating matters
Published in Jonathan Chapman, Routledge Handbook of Sustainable Product Design, 2017
Another one of our student’s work that exemplifies this is that of Anna Bullus’s ‘Gumdrop Bin’, which is a chewing gum bin made from recycled chewing gum. This highly acclaimed proposition is an elegant product pun, which both visually and materially relates to the blowing of a bubble-gum-bubble. Again, it utilizes conventional mass-manufacturing techniques to enable a closed loop system. The ‘gumdrop bin’ harvests waste chewing gum, which in turn, forms its own supply chain for the creation of more bins and a material language that is authentic, charming and importantly, memorable. All this, whilst serving to responsibly solve an environmental problem (waste chewing gum, and associated impacts of street clean-up) that costs local authorities considerable public money to deal with. Through in-depth material design, a poetic narrative is played-out between users and the product, through a descriptive, physical manifestation of the issue. So eloquently and composed is this material story and the effectiveness of both the symbolism and technical function is difficult to ignore, or misunderstand.
Interaction and self-organization of inclusions in two-dimensional free-standing smectic films
Published in Liquid Crystals Reviews, 2019
P. V. Dolganov, P. Cluzeau, V. K. Dolganov
It is worth noting that in 1997 Poulin et al. [17] observed another state, in which particles in nematic were connected by narrow stripes of orientationally deformed director of the liquid crystal. Stripes expand and shrink with the change of the interparticle distance. A ring disclination is located between the particles. Such a configuration was denoted the ‘bubble-gum’. Numerical calculations have shown [18] that in accordance with experiment [17] the force of interaction (attraction) between the particles practically does not depend on the interparticle distance. The ‘bubble-gum’ structure is energetically less favorable than the configuration with parallel dipoles, however it remains a metastable state for small interparticle distances. At large distances (r ∼ 8R0) the transformation into dipoles takes place.
Creation and topological charge switching of defect loops on a long fibre in the nematic liquid crystal
Published in Liquid Crystals, 2018
M. Nikkhou, H. F. Gleeson, I. Muševič
Figure 6(b) shows the interaction between the +1 point defect with the second kind of colloidal entanglement that is created between −1/2 loop and an elastic dipole. In this case, a dipolar colloidal particle is attracted with its −1 charged hyperbolic defect to the loop with the same −1/2 half charge. The spontaneous attraction between like topological charges creates a vortex-like or bubble-gum binding. A + 1 point defects is released close to this colloidal entanglement using the laser tweezers, which is presented in the first panel of Figure 6(b). The second panel in 6 (b) shows the corresponding schematics of the director field and defects. The +1 defect is spontaneously attracted to the bubble-gum binding which can be understood by considering the schematic drawing of the director escape around the entangled structure. The second and fourth panels of Figure 6(b) clearly show that the escaped region on the right-hand side of +1 defect and the hyperbolic defect of the particle share the same form of distortion, which means they are attracting each other to minimise their elastic energy. When the defect approaches the colloidal binding, the bubble-gum configuration collapses as illustrated in Figure 6(b), sixth panel.