Stretchable films

Very-low-density polyethylene (VLDPE) n. Any polymer of ethylene with some higher-olefin content, in the density range from 0.90 to 0.915g/cm, produced by the Union Carbide gas-phase process (Flex-omer ). The materials have low moduli, with properties between those of low-density polyethylene and ethylene-propylene rubbers. They are useful for stretchable films. 

Figure 5 shows typical x-ray diffraction curves of two types of polyacetylene films. The usual Shirakawa-type film [1,23] gave a very sharp diffraction curve. The halfwidth of the x-ray diffraction peak at 2 of 23.2 (110 and 2(X) reflections) was small (A20 = 1.2 ). However, it increased to 1.8 after the heat treatment for thermal isomerization from cis to trans form, implying that the ordered crystal structure in the as-grown cis-rich film suffered some destruction in the trans film. On the other hand, the highly stretchable film synthesized by the SE method gave a little diffused diffraction curve, as shown in Fig. 5. As the mechanical stretching proceeds, the half-width of the x-ray diffraction peak (A20 = 2.0°) decreased drastically to 1.5...

Poly(o-alkoxyanilines) are soluble in organic solvents in the doped and conductive form. Thus, they can be blended with insulating polymers by codissolution. This method was used to cast flexible, free-standing and stretchable films of blends of various compositions of poly(o-alkoxyaniline) and poly(vinylidenefluoride)... 

Electrical Industry. In addition to the familiar electrician s tape, usually a black adhesive with a stretchable film backing, there are many tapes used by equipment manufacturers for insulation in transformers and motors. These products require PSAs of low conductance. The tapes are rated in terms of temperature resistance. For highest temperature exposure, silicone PSAs must be used with specialty backings like glass cloth, polyvinyl fluoride. Teflon, or polyimide film. Tapes are also used to insulate soldered joints, to secure wire ends and, with fabric backings, to cushion and protect assemblies of wires. Harness tape is used to bundle a group of electrical wires. 

Commodity Applications Packaging. Heat stretchable films, transparent coatings vacuum, skin and blister packaging cosmetic containers, ski-boot parts, golf-ball covers, snap-fittings. 

Kim KS, Zhao Y, Jang H et al (2009) Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457 706-710... 

Stretchability denotes the suitability of a polymer in the solid state (amorphous or semicrystalline) to be stretched in one direction (occasionally in two directions). Of course, this processing step only serves a useful purpose in a specimen with a large aspect (i.e. length to diameter) ratio (fibres, films, sheets). The purpose of this operation generally is to achieve an improvement of mechanical properties, especially in the direction of stretching. 

Shrink and stretch wrapping—shrinkable films (PVC, polypropylene, polythene), sleeve or complete overwraps. Stretchable wraps, e.g. LLDPE, modified PEs. 

The development of flexible pressure sensor films was an important step in endowing robots with skin sensitivity, but e-skins are expected to add at least two more functionalities thermal sensing and conformability. Without conformability, e-skins cannot be applied to three-dimensional surfaces. Stretchable e-skins for humans are commercially available, but they do not possess electric functionality. Indeed, various stretchable materials, like rubber, are used in daily activities, but they have poor... 

In this section, we describe a solution that employs a net-shaped structure to make flexible electronic film devices conformable to three-dimensional surfaces [18]. Although the base films we presently use are of polyimide and poly(ethylenenaph-thalate) (PEN) — materials that are stiff and not inherently stretchable in a rubberlike sense — our solution includes struts of network structures that twist with the application of tension, as can be seen in Figure 6.3.7. Due to this three-dimensional strut deformation, the whole network structure functions electrically with a unidirectional extension of 25%. We have implemented the pressure sensor network on the surface of an egg and have obtained pressure images in this configuration. 

Lee and JGm examined the effect of lamellar structure of the dispersed EVA phase on the gas permeability of LDPE/EVA blends produced by film blowing (Lee and Kim, 1995, 1996). The viscosity ratio and dispersed domains size had a predominant influence on the formation of lamellae. An addition of LDPE-g-MA as a compatibilizer increased the number of particles and reduced the thickness of the layers. Between 5 and 6 wt% of compatibilizer produced a dispersed phase size of around 5 pm and the best oxygen permeability reduction (by a factor of 1600). Above this optimum concentration, the particle size becomes too small, resulting in shorter and thinner, and less effective, lamellae. Dispersed phase stretchability increased when a compatibilizer is present and when the viscosity ratio decreases, but it was not affected by the initial particle size. 

As noted in Section 12.5.1, a family of polyaxial copolyesters described in Chapter 2 can be used to prepare two or more of the critical components of a femoral sealing device. Other compliant members of this family of polymers, which can be converted to compliant, stretchable membranes and strong, stretchable monofilament fibers, can be used to construct a mantle or cover for metallic endovascular stents. Thus, a composite of thin film, reinforced with a monofilament in cross-coiled configuration, can be assembled into a highly compliant, expandable, tubular mantle or sleeve. This can be placed tightly as a cover outside an expandable metallic or polymeric stent so that under concentric irreversible expansion at the desired site of... 

Hu L, Yuan W, Brochu P, Gruner G, Pei Q (2009) Highly stretchable, conductive, and transparent nanotube thin films. Appl Phys Lett 94 161108... 

Perforated release films are made from modified polypropylene and can be rigid (recommended for use on flat or uncomplicated mold surfaces) or elastic (thin and stretchable, for large complex molds without need for tucks and folds). The films have good mechanical properties and performance at elevated temperature and are naturally self-releasing, treated on one side to assist adhesion to the breather fabric or a protective film. 

Carbon nanomaterials themselves also have good electrocatalytic activities, thus their composites with insulating polymers could also be used as counter electrodes of DSSCs. For instance, the CNT/epoxy composite films with CNTs being aligned to be perpendicular and parallel to the film surface have been investigated. However, the performances were lower than bare CNTs. They can also be composited with elastic polymers to be used for stretchable electronic devices. 

Vosgueritchian, M., Lipomi, D.L, Bao, Z., 2012. Highly conductive and transparent PEDOT PSS films with a fluorosurfactant for stretchable and flexible transparent electrodes. Adv. Eunct. Mater. 22,421-428. 

Recently, a large number of stretchable electrode materials for electrostatic actuation have been explored. The thin metal films are pioneered as the earliest candidates due to their high electrical conductivity, but they greatly suffered from the disadvantage of small strain less than 1%. Alternatively, the metallic nanoparticles including titanium, gold, and palladium were coated on the elastomer surfaces through metal ion implantation method. 

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