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Sustainable Polymers for Additive Manufacturing
Published in Antonio Paesano, Handbook of Sustainable Polymers for Additive Manufacturing, 2022
Based on a definition of degradation (Whittington 1978), a polymer or plastic material is degradable if it undergoes a damaging change in its chemical structure, physical properties or appearance caused by exposure to heat, light, oxygen, or weathering. According to ASTM D5488-94d and CEN EN 13432, biodegradable means “capable of undergoing decomposition into carbon dioxide, methane, water, inorganic compounds, or biomass in which the predominant mechanism is the enzymatic action of micro-organisms.” A biodegradable plastic is “a degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae” (ASTM D6400-19). The rate of biodegradation is affected by various factors, such as the medium of biodegradation, its temperature and humidity, and chemical features of the degrading polymer, such as composition and MW. Biodegradable polymers are cellulose, chitin, starch, PHAs, PCL, and collagen. Not all biobased polymers are biodegradable. F.e. PET is biobased and not biodegradable. Some SPs are biodegradable, and other SPs do not biodegrade in landfill, because the amount of heat and/or oxygen is not adequate for these plastics to break down. Further information on biodegradable polymers is found in Averous and Pollet (2012). Polyvinyl alcohol (PVA) is a synthetic polymer that is water soluble.
P
Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Poly(vinyl alcohol) (PVA) is useful as an industrial, medical, or biomimetic material. A PVA of high molecular weight is important to the production of a spinning gel that has both a high degree of strength and a high modulus. The initiator-free photo-emulsion polymerization of vinyl propionate and vinyl decanoate resulted in a good yield of polymers. The copolymer compositions were almost the same as those in feed monomer compositions, and the copolymerizations were considered to be random. The tacticities of PVAs obtained from PVAc by this method are the same as those of PVAs obtained through radical polymerization. Polymerization is inhibited by oxygen, and the electron spin resonance signal is observed by irradiation of the frozen vinyl acetate/LWZ/methanol system. These facts indicate that the polymerization takes place radically. As no polymer was obtained by heating the system, initiation by peroxides contained in the system was negligible.
Bionanocomposites
Published in Satya Eswari Jujjavarapu, Krishna Mohan Poluri, Green Polymeric Nanocomposites, 2020
Archita Gupta, Padmini Padmanabhan, Sneha Singh
Poly (vinyl alcohol) (PVA) is a thermoplastic and water-soluble polymer formed by the hydrolysis of poly (vinyl acetate) or condensation of acetaldehyde (Baker et al. 2012). To form a low molecular weight PVA, polymerization of the metal compound or vinyl ester takes place first followed by a saponification or esterification process (Jose et al. 2014). The molecular weight of PVA is significant, as its properties are governed by this and by the degree of hydrolysis. On increasing the molecular weight and hydrolysis, there is an observed increase in tensile strength and solvent resistance while there is a decrease in flexibility, water sensitivity, and solubility (Oviedo et al. 2008). The wide range of properties of PVA, which are its biocompatibility, water solubility, high mechanical strength, resistance towards organic solvents, and inexpensive availability, have attracted its extensive application as an implant (Gross et al. 2002).
Potentiality of high Z doped PVA polymer as a gamma, neutron and charged particles shielding material
Published in Radiation Effects and Defects in Solids, 2023
G. B. Hiremath, N. H. Ayachit, N. M. Badiger
Polymers properties are attractive, such as light weight, good workability, ease of process ability, and stability in harsh environments (33). The addition of high Z in the polymers can act as shielding materials. Recently, several investigators measured radiation shielding properties for polymers composites (34–39). PVA (polyvinyl alcohol) is a synthetic polymer that is water-soluble and has good elastic mechanical, flexible, ductile, and compressive properties, as well as biodegradability and biocompatibility (40,41). Mostafa et al., (40) found that 30 wt % Er+3 in PVA has better gamma shields than 30 wt% Dy+3 in PVA. Muthamma et al., (41) found that Bi-filled PVA polymers, which are lightweight, easily fabricated, and cost-effective composites, show good radiation shields with increases in filler weight. Issa et al., (42) discovered that increasing the mass attenuation coefficient values increases the BaTiO3 content in PVA from 0.65 to 3.57%.
Numerical study of behavior of textile-reinforced composite tubes under lateral compression
Published in Mechanics Based Design of Structures and Machines, 2023
In this research, two fabric types were used as woven (plain weave) and bonded. One of them is alkali-resistant glass (Ar-glass) textile sheets which are made from bundles in warp and weft. Another is polyvinyl alcohol (PVA) textile sheet which is formed by passing over and under each other of the warp and weft yarns in woven fabrics. Thus, a PVA textile sheet does not contain the mesh space of an Ar-glass textile sheet (Daskiran, Daskiran, and Gencoglu 2016, Fidelis et al. 2016, and Sueki et al. 2007). While TRCCs obtained using PVA is more laminated, TRCCs obtained using Ar-glass shows better bonding to cement-based mortar due to their binding of textile nets and cement matrices (Cuypers et al. 2008, Pakravan, Jamshidi, and Rezaei 2016). This paper aims to represent numerically the damage evolution, load-carrying capacity and energy absorption capacities of TRCC tubes (pipes) with different characteristics.
Cement stabilisation of recycled concrete aggregate modified with polyvinyl alcohol
Published in International Journal of Pavement Engineering, 2022
Teerasak Yaowarat, Suksun Horpibulsuk, Arul Arulrajah, Farshid Maghool, Mehdi Mirzababaei, Ahmad Safuan A. Rashid, Avirut Chinkulkijniwat
In addition to fiber-reinforced soil and base/subbase materials, polymer-stabilisation techniques have become progressively popular for soil improvement projects (Santoni et al.2002). There are many polymeric binders that have been proven to be effective as potential particle binders for soil stabilisation (Onyejekwe and Ghataora 2015). Polyvinyl alcohol (PVA) is a polymer, which is recognised as an eco–friendly, odourless, water-soluble, non–ionic and hydrophilic polymer with an excellent film forming potential (Ding et al.2002). Brown et al. (2004) investigated the effect of PVA-stabilised soil and the results indicated that PVA acts as a polymeric binder by entwining within the soil particles and thus stabilising the loose soil into a relatively firm mass. PVA has also been reported to enhance the ductility as well as the toughness of clay similar to the fibre reinforcement (Mirzababaei et al.2017a, Mirzababaei et al.2018a). Moreover, PVA solutions can be prepared easily by dissolving PVA in water (Çay and Miraftab 2013), which can potentially be used to stabilise RCA particles and the distribution of PVA solution can be precisely determined more than the fibres.