Self tapes

Self-taped turnout gear with SCBA provides sufficient protection in an unknown nerve agent environment for a three-minute reconnaissance to search for living victimsJlpr a two-minute reconnaissance if HD (mustard, blister agent) is suspected. ... 

Figure 9.8 Mechanical fastening with (a) self-taping screws and (6) bolts, nuts, and washers. ...

Self-Adhering Silicone Rubber Tape" in GeneralElectric Company bulletin. Insulating Materials Data PD 1302, General Electric Co., Schenectady,... 

An important application for polypropylene is film tape. This is made by slitting unoriented film (cast or blown) into tapes 2 or 3.5 mm wide and stretching under heat about seven-fold. With cast film the orientation is more completely monoaxial and there is a tendency for the film to split along its length (fibrillate). Tubular film does not self-split so easily and also has a somewhat softer feel. Such tapes may be woven into sacks and these have... 

The use of coatings applied in the form of tape is also increasing. Polyethylene and polyvinyl chloride films, either self adhesive or else supporting films of butyl adhesive, petrolatum or butyl mastic are in use as materials applied cold at ambient temperatures. Woven glass fibre or nylon bandage is also used to support films of filled asphalt or coal tar and these are softened by propane gas torches and applied to the steel surface hot, cooling to form a thick conforming adherent layer. 

Spiral corrosion due to inadequate overlap has been detected with self-adhesive tapes, and a 25 mm (or preferably half-tape-width) overlap is to be advocated. Within normal limits, the thicker the adhesive the better. 

The self-adhesive tape coatings are thin and the adhesive itself does not necessarily come into contact with the valleys in the cleaned metal surface. Under these circumstances, the transmission of water vapour through the film to the metal may be possible. Moisture-transmission characteristics and other properties of p.v.c. and polyethylene tapes, as given by major manufacturers, are provided in Table 14.6. 

Table 14.6 is only indicative of general properties, and the latest developments of specific manufacturers of self-adhesive tapes may show advances on these. 

Weld joints may be coated in the field with FBE powder, utilising a portable blast cleaning/induction heating and powder application system. Alternatively joints may be provided with self-adhesive laminate tapes or heat-shrink crosslinked polyethylene sleeves. 

Repairs to the coating are made with either hot-melt polyethylene sticks or polyethylene sheet patches with mastic profiling compounds for small damaged areas. Large repair areas are best treated as for field weld joint coating, where either heat-shrink crosslinked polyethylene sleeves or cold-applied self-adhesive laminate tapes are employed. 

In addition to the petrolatum tapes and those based on a laminate of p.e. or p.v.c. with an elastomeric sealant or pressure-sensitive adhesive layer, recent developments have centred around self-adhesive bituminous laminates. These tapes are commonly constructed with a p.v.c. backing, whose thickness ranges from 0 08 to 0 75 mm and a bituminous adhesive compound layer to provide a total tape thickness of up to 2 mm. In order to maintain conformability without compromising impact values, tapes may also be manufactured with a fabric reinforcement within the bituminous layer. 

The monitoring of temperatures for electronic control systems is now mainly by thermocouples, secured onto the outside of the pipe with self-adhesive tape and the pipe then insulated over. 

Von Neumann s machine is actually an example of a universal constructor. It must not only carry out logical operations (i.e. act as a universal computer), but must also be able to identify and manipulate various components. The universal constructor C must be able to both (1) construct the machine whose blueprint appears in symbolic form on its input tape and (2) attach a copy of that same blueprint to the machine once it is constructed. Self-reproduction is the special case where C s input tape actually contains the blueprint data for C itself. Alas, there are a few subtleties. 

Suppose we start with an automaton A that is given a tape with a blueprint B a on it. The composite machine will then construct a copy of A but it is not, in and of itself, self-reproducing i.e, the aggregate machine A + creates A, not A + B. This situation is not remedied by simply adding a description of B to B, since in this case A + yields A + B and not A + B +Ba Thus, whatever we... 

Fig. 10 (a-f) Hierarchical self-assembly model for chiral rod-like units A curly tape (c ), a twisted ribbon (d ), a fibril (e ) and a fibre (f). Adapted from Aggeli et al. [20], Copyright 2001 National Academy of Sciences, USA... 

For instance, Pn-2 forms ribbons at concentrations >0.1 mM in water. At 0.6 mM, these ribbons self-assemble into fibrils and at higher concentrations into fibres. Conversely, glutamine-rich Pn-1 (Ac-QQRQQQQQEQQ-Am) forms ribbons at 1 mM and does not form fibrils, even at concentrations as high as 25 mM. Association of Pn-2 into ribbons is much more favourable due to it having hydrophobic aromatic residues arranged such that there is a large disparity between the hydrophobicity of each of its tape faces. 

For technological applications it is highly desirable to be able to design self-assembling systems to have particular physico-chemical properties under a given set of experimental conditions. Using computer simulation, it is possible to construct an atomistic model of tapes, ribbons and fibrils to study all of the interatomic interactions within the system in a quantitative manner. Figure 13 shows atomistic... 

Aggeli A, Bell M, Boden N et al (1997) Responsive gels formed by the spontaneous self-assembly of peptides into polymeric beta-sheet tapes. Nature 386 259-262... 

Office supplies and office communication have been revolutionized by the introduction of the 3M product Post-it Notes in 1980. The temporary adhesive of these self-sticking notes actually was initially rejected as a glue by its inventor, 3M chemist Spencer Silver, because of its impermanence. However, 3M researcher Art Fry found a niche for the adhesive—as an adhesive for a temporary bookmark for his choir hymnal. Key to the performance of these removable, repositional adhesive products is the application of the adhesive to the backing of a note sheet via tiny microspheres rather than a continuous film. With an average particle diameter of 25-45 fim, the microsphere adhesives form a discontinuous layer that assists in retaining the ability to re-apply the note to new surfaces. Traditional adhesive tape contains particles of smaller dimension (typically 0.1 to 2.0 pm) that coalesce to form a continuous film that limits removal. ... 

The chiral l,3,5-triazepane-2,6-dione 149 and its ring fused analogue 150 have been shown to form H-bonded helical molecular tapes with P chirality on self assembly in the solid state. With 149, this self assembly proceeds through aromatic-aromatic ring interactions resulting in hollow tubular structures <06CC4069>. 

Figure 5.24 Model of hierarchical self-assembly of chiral rodlike monomers.109 (a) Local arrangements (c-f) and corresponding global equilibrium conformations (c -f) for hierarchical selfassembling structures formed in solutions of chiral molecules (a), which have complementary donor and acceptor groups, shown by arrows, via which they interact and align to form tapes (c). Black and the white surfaces of rod (a) are reflected in sides of helical tape (c), which is chosen to curl toward black side (c ). (b) Phase diagram of solution of twisted ribbons that form fibrils. Scaled variables relative helix pitch of isolated ribbons h hh /a. relative side-by-side attraction energy between fibrils eaur/e. Reprinted with permission from Ref. 109. Copyright 2001 by the National Academy of Sciences, U.S.A.

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