Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-a-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and c...

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Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Biodegradation of poly(vinyl alcohol) based materials

Emulsion polymerization mechanisms and kinetics

Pure hydrogen production by PEM electrolysis for hydrogen energy

Proton exchange membrane fuel cells (PEMFCs) have recently passed the test or demonstration phase and have partially reached the commercialization stage due to the impressive worldwide research effort. Despite the currently promising achievements and the plausible prospects of PEMFCs, there are many challenges remaining that need to be overcome before PEMFCs can successfully and economically substitute for the various traditional energy systems. With the many promising research efforts in overcoming these challenges, the most important tools for the commercialization of PEMFCs will be the technical data and information from a real PEMFC application test. For these reasons, this paper introduces and discusses the remaining challenges and some of the latest research on the application test of PEMFC to real systems such as transportation, residential power generation and portable computers. In addition, this paper describes and summarizes the relative prospects and the competitive force of PEMFCs in these fields. These prospects primarily depend on stable and economical high-purity hydrogen supplies, the scale of application, the existence of more efficient competitive power sources and the social viewpoints such as the health and environment benefits as well as infrastructural aspects associated with traditional power supply and demand. The review shows that PEMFC have the most promising applications to buses, recreation vehicles, and lightweight vehicles. Without doubt, the technology for a stable supply of high-purity hydrogen along with the corresponding infrastructure is essential for the success of PEMFC in various application fields.

Applications of proton exchange membrane fuel cell systems

Aqueous polymerization of acrylamide initiated with a redox initiator system composed of cysteine and potassium bromate was investigated as a model of the redox initiator system composed of poly(vinyl alcohol) having a thiol groups at one end and potassium bromate. The rate of polymerization was proportional to almost the square root of cysteine and potassium bromate concentration, indicating the initiation system is a usual free radical polymerization initiator. On the other hand, the rate was proportional to the 1.8th power of the monomer concentration. The activation energy of the rate of polymerization was about 5 kcal. mol -1 , indicating also a typical redox initiation system. Chain transfer constant of polyacrylamide radical to cysteine was calculated to be 0.4. From these results, it is concluded that cysteine exerts two important roles: (1) as a reductant of the redox initiation and (2) as a powerful chain transfer reagent.

Polymerization of acrylamide in aqueous medium initiated with a redox system composed of cysteine and potassium bromate

To clarify the influence of additives on the grafting phenomenon as well as the particle behavior more precisely, we carried out a model emulsion polymerization of vinyl acetate (VAc) in a 1% aqueous solution with ammonium persulfate (APS) using poly (vinyl alcohol) (PVA) as a protective colloid in the presence of additives. The addition of alcohol to the system remarkably affected the particle formation, especially grafting. This is thought to be attributed to competition between hydrogen abstraction from PVA and alcohol with a sulfate radical. Especially, the addition of acetone to the system decreased grafting to a great extent, resulting in an increase in the particle size together with an increase in the number of polymer molecules in a polymer particle. This result is thought to arise from a combination of electron abstraction from acetone with a sulfate radical and the chain-transfer reaction of the propagation radical with acetone.

Influence of additives on model emulsion polymerization of vinyl acetate (VAc) using poly(vinyl alcohol) (PVA) as a protective colloid

Process for the preparation of grafted solid materials of water-affinitive polymers such as polyvinyl alcohol, acetalized polyvinyl alcohol, polyamide, polyacrylonitrile and cellulose, which comprises immersing said solid material in an aqueous solution or suspension of an ester of acrylic acid or metacrylic acid at a temperature of 40 DEG - 120 DEG C., in the presence of 20 - 1,000 ppb of molecular oxygen, as a reaction initiating component, in the aqueous solution or suspension. In this way, the graft polymerization reaction is initiated smoothly and high reaction rate of the graft polymerization is obtained without the substantial formation of homopolymer of the ester in the liquid phase.

Process for the preparation of grafted solid materials of water-affinitive polymers

Anionic groups were introduced with copolymerization of corresponding vinyl monomers with vinyl acetate into poly(vinyl alcohol) (PVA) with an alkylthio end group. The polymers were investigated as a dispersant for coal-water slurry (CWM). Anionic groups such as sodium sulfonate and sodium carboxylate enhance remarkably the ability of PVA with an alkylthio end group to disperse coal. Sodium polyacrylic acid with an alkyl end group also showed a good ability of dispersing coal. The order of the ability of dispersing coal in these polymeric dispersants along with sodium napthalene sulfonate formaldehyde condensate (NSF) varied by the kind of coal used. In cases of the polymeric dispersants, the fluidity of coal in terms of dependence of viscosity on shear rate also varied, from dilatency to thixotropy, in accordance with coal used. Impurities in coal as well as surface properties of coal particles might play important roles in the properties of CWM. © 1995 John Wiley & Sons, Inc.

Application of poly(vinyl alcohol) with an alkyl end group containing anionic groups to coal–water slurry as a dispersant

PURPOSE: To produce a pressuresensitive and surface-protecting material which resists weathering and readily sticks to and peels off from a wide range of wares, such as metal, glass wares, and furnitures, by transferring, to sponge, an adhesive layer which has previously been formed by coating a polyisoprene tackfier of specific composition on releasing paper. COPYRIGHT: (C)1977,JPO&Japio

Takuji Okaya

Papers

Polymerization of acrylamide in aqueous medium initiated with a redox system composed of cysteine and potassium bromate

Influence of additives on model emulsion polymerization of vinyl acetate (VAc) using poly(vinyl alcohol) (PVA) as a protective colloid

Process for the preparation of grafted solid materials of water-affinitive polymers

Application of poly(vinyl alcohol) with an alkyl end group containing anionic groups to coal–water slurry as a dispersant

Material for protecting surface