Water-soluble PVA film

Water-soluble PVA film belongs to green eco-friendly packaging materials. On packing, it has some features as follows ... 

The water-soluble PVA film has comparatively higher mechanical performance and heat seal strength as well as outstanding gas barrier property and maintains... 

The dissolving speed of water-soluble PVA film can be controlled and can be dissolved in cold water. 

The medical package bags made of environment-friendly material of water-soluble PVA film have ideal antifriction and is environment-friendly. They have some advantages as follows ... 

From a macroscopic perspective, almost all the water-soluble films are hydrophilic materials. There is a large number of hydrophilic polar group in the molecular structure. The dissolution mechanism of water-soluble PVA film can be explained as follows PVA absorbs large amounts of water molecules and in order to make the molecules expand and resolve, the temperature is raised with continued heating. Then the numerous molecules which are made of carbon, oxygen, and hydrogen, are resolved into CO2 and H2O. And CO2 ultimately evaporates into air. It explains the fact that hydrolysis products of PVA do not harm the environment and they are environment-friendly materials. 

Water-soluble PVA film has low toxicity to living organisms and it is hardly absorbed by the gastrointestinal tract. Furthermore, PVA cannot be accumulated in one s body. 

Other applications of PVA-based hydrogels include different coatings for metals (e.g., silver nanoparticles, or Ag NPs [Eisa et al. 2012]), carbon nanotubes (CNTs) (Malikov et al. 2014), or cellulose (Han et al. 2014), as well as paper coatings, water-soluble packaging films, textile sizing, and hydrophilic membranes for pervaporation (Zhang et al. 2012). 

As already mentioned, PVA is a water soluble polymer used in applications such as packaging films where water solubility is desired. It is the most readily biodegradable of the vinyl polymers, which makes it a potentially useful material in biomedical, agricultural, and water treatment areas, for example, as a flocculant, or scavenger of metal ions. Moreover, due to its water solubility, PVA can also be used as a model for particle dispersion in aqueous suspensions, especially those from CNWs and some clays. As a consequence, PVA has been largely used to produce nanocomposites with clays, cellulose, and chitin whiskers, silver nanoparticles, graphite oxide, and carbon nanotubes. 

Cu(NH,) JXj (X = CIO4, NO, Cl, Br, or SO,), (3) the degree of crystallinity in PVA film, and (4) the degree of orientation of crystallites in PVA film. (b) Preparation of Cu(lI)-Poly(vinyl alcohol) Complex Film /22. The water-in.soluble PVA films were prepared by spreading a 2% aqueous solution of PVA on a polyethylene plate and heating to dryness for about 2 h at about 80°C. The film strips peeled off the plate were heated further al 1 lO C for 1.5—2 h. The dried film (about 0.03 X 40 X 40 mm) swelled isotropically when su.spended in water. When the film was suspended in an aqueous... 

The main applications for PVA are in textile sizing, adhesives, polymerization stabilizers, paper coating, poly(vinyl butyial), and PVA fibers. In terms of percentage, and omitting the production of PVA not isolated prior to conversion into poly(vinyl butyral), the principal applications are textile sizes, at 30% adhesives, including use as a protective colloid, at 25% fibers, at 15% paper sizes, at 15%, poly(vinyl butyral), at 10% and others, at 5%, which include water-soluble films, nonwoven fabric binders, thickeners, slow-release binders for fertilizer, photoprinting plates, sponges for cosmetic, and health care applications. 

Several different film-forming polymeric binders were used, including polar, water-soluble materials (PVA, poly(vinyl alcohol)) and organic materials of lower polarity (CAB, cellulose acetate/butyrate, and Elvamide , a polyamide polymer). Figure 6 illustrates the optical spectra obtained for films in CAB binder in the visible region. Note that substantial differences are obtained depending on the nature of the activator. 

Poly(vinyl) alcohol (PVA) is a semi-crystalline polymer, which is already widely used for various applications, either under the form of films or fibers. Compared to other polymers, as it is water-soluble at high temperature, it is easy to process from aqueous solutions. Carbon nanotubes can also be dispersed or solubilized in water via different functionalization approaches. It was quite natural for researchers to try to mix carbon nanotubes and PVA to improve the properties of the neat polymer. In this chapter, we will first examine the different methods that have been used to process CNT/PVA composites. The structures and the particular interaction between the polymer and the nanotube surface have been characterized in several works. Then we will consider the composite mechanical properties, which have been extensively investigated in the literature. Despite the number of publications in the field, we will see that a lot of work is still to be done for achieving the most of the exceptional reinforcement potential of carbon nanotubes. 

Whether or not the surface of a polymer is hydrophilic or hydrophobic is not determined by whether hydrophilic or hydrophobic moieties exist in a polymer molecule but by what kind of moieties actually occupy the top surface of the polymer. Namely, the surface properties are controlled by the surface configuration but not by the configuration of polymer molecules. The configuration of PVA can be represented by -[CH2-CH(OH)] -, which indicates that the polymer is highly hydrophilic, and PVA is water soluble. However, the surface characteristics of a film of PVA depend entirely on how many OH groups exist on the top surface or buried in the bulk phase of the polymer that is described by the surface configuration. 

Since the sublimation or vaporization rate of most monomers under vacuum is not insignificant, a thin polymer film was coated on top of the resist as a monomer sublimation barrier. Two water soluble polymers, poly(vinyl alcohol) (PVA) and poly(vinyl pyrroidone) (PVP), were used. It has been found that PVA solution yields more uniform films, and after e-beam exposure, can be removed easily by dipping in water for 30 seconds. There was no evidence of crosslinking in PVA after e-beam exposure. However, PVP acts as a negative resist with sensitivity (Dg ) approximately equal to 60yC cm-. PVA, therefore, was used as the monomer barrier for most experiments. 

The radioelectric properties of the resulting films strongly depend on the water content of the monomer solution. Indeed, the diffiision of water significantly affects the reproducibility of processes since PVA is water soluble. Two dominating factors have been identified ... 

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