Poly(vinyl alcohol) (PVA) is a polymer of great interest because of its many desirable characteristics specifically for various pharmaceutical and biomedical applications. The crystalline nature of PVA has been of specific interest particularly for physically cross-linked hydrogels prepared by repeated cycles of freezing and thawing. This review includes details on the structure and properties of PVA, the synthesis of its hydrogels, the crystallization of PVA, as well as its applications. An analysis of previous work in the development of freezing and thawing processes is presented focusing on the implications of such materials for a variety of applications. PVA blends that have been developed with enhanced properties for specific applications will also be discussed briefly. Finally, the future directions involving the further development of freeze/thawed PVA hydrogels are addressed.

Structure and Applications of Poly(vinyl alcohol) Hydrogels Produced by Conventional Crosslinking or by Freezing/Thawing Methods

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(03)00211-7.pdf

Polymeric cryogels as promising materials of biotechnological interest.

Double network (DN) hydrogels as promising soft-and-tough materials intrinsically possess extraordinary mechanical strength and toughness due to their unique contrasting network structures, strong interpenetrating network entanglement, and efficient energy dissipation. It has been ∼11 years since the first PAMPS–PAAm DN hydrogel was developed, but the research and development of new DN hydrogels are still at a very early stage. A vast number of network monomers available in the current chemical inventory provide the possibility to design new DN gels and to explore the fundamental relationship of DN gels among network structures, mechanical properties, and toughening mechanisms, which help to derive new design principles for the next-generation tough hydrogels. In this review, we strive to highlight the development and fundamentals of DN gels covering from preparation methods, network structures, to toughening mechanisms over the last decade.

Fundamentals of double network hydrogels

Poly(vinyl alcohol) cryogels employed as matrices for cell immobilization. 3. Overview of recent research and developments

The present invention provides a laminated polyester film which exhibits a good adhesion property to various adhesives, and can be suitably used in the applications in which a high total light transmittance is required, for example, as a member for protecting a polarizing plate of liquid crystal displays, in particularly, as a protective film disposed on a rear surface of a rear side polarizing plate. The laminated polyester film according to the present invention comprises a polyester film; a coating layer formed by applying a coating solution which comprises at least one resin selected from the group consisting of a polyester resin, an acrylic resin and a urethane resin, polyvinyl alcohol and an oxazoline compound, on one surface of the polyester film; and a coating layer formed on the other surface of the polyester film which has an absolute reflectance exhibiting one minimum value in a wavelength range of 300 to 800 nm wherein the minimum value is not more than 3.5%.

Laminated polyester film

A waste water treatment apparatus which is compact, and excellent in durability, has a high treatment performance and can stably operate for a long time is provided. In a waste water treatment apparatus at least comprising a waste water treatment tank in which a carrier particle immobilizing a microbe is charged and decomposing and eliminating an organic matter and/or an inorganic matter contained in a waste water, and a membrane module for filtrating a water to be treated which flows out from said treatment tank, a non-permeating water not passing thorough the membrane module is returned and circulated to said treatment tank. In a waste water treatment apparatus at least comprising a waste water treatment tank in which a carrier particle immobilizing a microbe is charged and decomposing and eliminating an organic matter and/or an inorganic matter contained in a waste water, a carrier immobilizing a microbe is an acetalized polyvinyl alcohol hydrogel.

Waste water treatment apparatus

A polyvinyl alcohol hydrogel has a surface layer comprising a net-like structure formed by entanglement of fiber-like articles having a diameter of 0.1 to 50 µ m. This gel has a large surface area and high capability of adhering microorganisms and permeating liquid, thereby exhibiting excellent purifying function. Processes for producing the above hydrogel are also provided.

Polyvinyl alcohol hydrogel and process for producing the same

The activated sludge that had been sufficiently cultivated with DMF-containing waste water was entrapped and immobilized in spherical poly(vinyl alcohol) (PVA) hydrogel particles. Features of numbers and distribution of bacteria in the resultant PVA gel were estimated. The DMF-decomposing bacteria named Bacillus cereus D-1 was isolated. Several morphological and physiological responses of the bacteria were revealed. Spherical PVA gel with the DMF-decomposing bacteria prepared through of freezing and thawing was tested for treatment of DMF-containing effluent. Test results have shown the ability of stable operation and maintenance at the same capacity of 1 kg/m3/day by both a basic study and a bench plant test. © 1995 John Wiley & Sons, Inc.

Development of poly(vinyl alcohol) hydrogel for waste water cleaning. II. Treatment of N,N‐dimethylformamide in waste water with poly(vinyl alcohol) gel with immobilized microorganisms

The structures and properties of poly(viny1 alcohol) (PVA) hydrogel prepared by the freezing and thawing method and poly(ethy1ene glycol) and polyacrylamide hydrogels prepared by polymerization were compared in view of immobilizing microorganisms. Observation in a scanning electron microscope and measurement of the physicochemical properties revealed that the frozen PVA gel is superior in water content and oxygen permeability than the other gels. The PVA hydrogel has a high tensile and folding strength and good handleability and processability. The durability against abrasion and chemical resistance of PVA gel were also studied. Activated sludge was immobilized and fixed on PVA gel particles and incubated. This gel had a treating capacity for synthetic sewage of about two to three times that with the standard activated sludge process. © 1995 John Wiley & Sons, Inc.

Development of poly(vinyl alcohol) hydrogel for waste water cleaning. I. Study of poly(vinyl alcohol) gel as a carrier for immobilizing microorganisms

PROBLEM TO BE SOLVED: To provide a metallic coating film free from the variation of hue caused by the interlayer mixing of a metallic base coating film and a clear coating film in the case of coating by a two-coat one-bake coating method, having excellent hue stability of the coating material and dense glittering appearance of the coating film and exhibiting flip-flop property. SOLUTION: The solvent-type metallic base coating composition contains (A) a urea-modified acrylic resin, (B) a urethane-modified polyester resin, (C) a curing agent, (D) a glittering pigment, (E) a color pigment and (F) a dispersion assistant for the color pigment. The weight ratio of (A) the urea-modified acrylic resin to (B) the urethane-modified polyester resin is 60/40 to 95/5 in solid basis. COPYRIGHT: (C)2005,JPO&NCIPI

Hiroaki Fujii

Papers

Waste water treatment apparatus

Polyvinyl alcohol hydrogel and process for producing the same

Development of poly(vinyl alcohol) hydrogel for waste water cleaning. II. Treatment of N,N‐dimethylformamide in waste water with poly(vinyl alcohol) gel with immobilized microorganisms

Development of poly(vinyl alcohol) hydrogel for waste water cleaning. I. Study of poly(vinyl alcohol) gel as a carrier for immobilizing microorganisms

Metallic base coating composition and method for forming layered coating film