Polarizers polyvinyl film

Fig.6.47. Spectral characteristics of polyvinyl film polarizers (Courtesy Oriel Corp., Stratford, CT, USA)...

Linear polarizers can also be made of polyvinyl film that has been stretched so as to align long chains of molecules. Different kinds of polarizers of this type are available for wavelengths from 200 nm up to the near IR. In Fig. 6.47 examples of transmission and extinction curves are shown. 

Nitrile rubber adhesives. The main application corresponds to laminating adhesives. PVC, polyvinyl acetate and other polymeric films can be laminated to several metals, including aluminium and brass, by using NBR adhesives. NBR adhesives can also be used to join medium-to-high polarity rubbers to polyamide substrates. The adhesive properties of NBR rubbers can be further improved by chemical modification using polyisocyanate or by grafting with methyl methacrylate. 

We now discuss the annular tautomerism of azoles. For 5-phenyltetra-zole, the 2//-tautomer was found predominant in polyvinyl alcohol film (based on the determination of polarization angles of electronic transition... 

Similar results are found for doped polyvinyl alcohol44. This system is of interest because its colour changes when the polymer is stretched, and the stretched film is a good polarizer. At low iodine content, the film is brown or yellow, but becomes blue on stretching this change is reversible. The colour can also be enhanced by adding boric acid to the iodinedoping solution. 

Films of polyvinyl fluoride retain their form and strength even when boiled in strong acids and bases. At ordinary temperatures, the film is not affected by many classes of common solvents, including hydrocarbon and chlorinated solvents. It is partially soluble in a few highly polar solvents above 149°C (300°F). It is impermeable to greases and oils [95]. 

Polaroid , the material of which most polarizers are currently made, is composed of a clear sheet of polyvinyl alcohol. It is stretched in one direction to align the molecules and dyed with iodine molecules that align themselves along the polymer molecules. This polaroid film will transmit light only in a direction perpendicular to that in which the film was stretched. Polaroid was first made in 1928 by Edwin Herbert Land from quinine sulfate periodide. " The initial idea for this came from the observation of William Bird Herapath that when iodine is dropped in the urine of a dog that has been fed on quinine, shiny green crystals (now referred to as herapathite) with strongly polarizing properties are formed. 

In this regard, polyvinyl alcohol (PVA), a hydrolysis product of polyvinyl acetate, is well suited for blending with natural polymers since it is highly polar and water-soluble synthetic polymer which is also biodegra ble. PVA and starch films have been prepared for use as agricultural mulch films and as water-soluble laundry bags. Cast films made firom PVA and cellulose, prepared in N,N-dimethylacetamide-lithium chloride, exhibited good miscibility due to their mutual ability to form infra-... 

Chem. Descrip. Acetyltriethyl dtrate CAS 77-894 EINECS/ELINCS 201-066-5 Uses Plasticizer for more polar resins such as cellulosics, polyaciylates, PVAc, polyvinyl butyral, PVC, PVP, PVdC, chlorinated rubber lightfastness for lacquer formulations solvent in household, I I cleaners solvent, film-fonner, plasticizer for inks, adhesives, coatings, food pkg. adhesives/coatings/paper/paperboard/polymers Features Environmentally friendly... 

The solvents used in coatings are hydrocarbons for alkyds, and aromatics in admixture with more polar solvents for most other media. Highly insoluble polymers, such as polyvinyl chloride and polyvinylidene fluoride, are applied as dispersions. Selection of a wrongly formulated solvent mixture may have an adverse effect on the adhesion of a film, when formed af room femperafure. High boiling solvenfs, for example, can become flapped af the film-substrate interface for some considerable time and give rise to a soft and poorly adherent film. 

Extrusion and impregnation, electrospinning, and multilayer films are other processes applicable for reinforced nanocomposites. Thus, preparation of cellulose whiskers reinforced with polylactic acid nanocomposites (by melt extrusion carried out by pumping the suspension of nanocrystals into the polymer melt during the extrusion process), using polyvinyl alcohol as a compatibilizer for the dispersion of cellulose whiskers within the polylactic acid matrix, was reported (de Menezes et al. 2009) bacterial cellulose whiskers incorporated into poly(oxyethylene) nanofibers by electrospinn to enhance the mechanical properties of electrospun fibers (Peresin et al. 2010) or the use of the layer-by-layer assembly technique, which maximizes the interaction between cellulose whiskers and a polar polymeric matrix (Bruno et al. 2009 Aulin et al. 2010), are some examples of nanocomposites reinforced by the last three methods. 

The dispersion of fibers in polymer latex to prepare composite has been reported for poly(6-hydroxyoctanoate) (PHO) [101, 102], polyvinylchloride (PVC) [103], waterborne epoxy [104] and polyvinyl acetate (PVAc) [94]. Most of the works focus on the use of non-polar, non-water-sensitive polymers, while keeping an aqueous media for the processing of the films to preserve the dispersion of the nanoparticles. In their pioneering work, Favier et al [94] adopted the technique of solvent casting using a synthetic latex obtained by the copolymerization between styrene (35 wt%) and butyl-acrylate (65 wt%) (poly(S-co-BuA)). Nanowhiskers were dispersed in the latex and evaporated. The nanocomposite films were obtained by water evaporation and particle coalescence at room temperature, that is at a temperature higher than Tg of poly(S-co-BuA), around 0 C. 

Certain polymers, such as polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), possess special properties in the film form, caileApiezoelectricity and pyroelectricity. Piezoelectricity is electric polarization of a film produced by mechanical strain in some crystals. The polarization is proportional to the amount of strain and changes sign with it. The reverse is true and an electrical polarization induces a mechanical strain in piezoelectric sensors. Pyroelectricity is electric polarization of a film induced by thermal absorption in some polymer crystals. The induced polarization is proportional to the level of thermal change. These properties can be used in the manufacture of transducers, microphones, loudspeakers, pressure gauges, pickup heads, hydrophones, motion sensors, and other devices from biaxially oriented PVDF films. Table 13.37 gives the properties of a piezoelectric film of polyvinylidene fluoride. 

As known, polarizing film mainly consists of CTA and PVA (the structures of CTA and PVA are shown in Figures 17.9 and 17.10). That is to say, in the hydrothermal process, the production of acetic add primarily comes from CTA or PVA. In the chemical structure of CTA, all cellulose hydroxyl groups are replaced by acetyl groups. And the physical characteristics of PVA are dependent on its method of preparation from the hydrolysis, or partial hydrolysis, of polyvinyl acetate. PVA is generally classified into two groups, partially hydrolyzed and fully hydrolyzed. 

Later developments were that the WV film was directly attached to the polyvinyl alcohol (PVA) film of the polarizer, and the second generation design of WV films was developed in cooperation with FUJIFILM and Sanritz. The important experience for me was that the development of this WV film had formed the base for the whole R D activity as well as the later wide-viewing-angle LCD development. 

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