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Polyhydroxyalkanoates (PHA)-Based Materials in Food Packaging Applications
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Lucía Pérez Amaro, David Barsi, Tommaso Guazzini, Vassilka Ivanova Ilieva, Arianna Domenichelli, Ilaria Chicca, Emo Chiellini
The environment is a determining factor in governing the speed and the degree of biodegradation of the matrices of bio-based polymers. The environmental compartments in which biodegradation processes can occur are attributable to two categories: aerobic (presence of oxygen), and anaerobic (lack of oxygen). The biodegradability of polymeric materials and related plastic items in general depends upon [50]: Presence of microbial strains susceptible to colonizing polymeric materials and related fragmented products.Temperature.Availability of oxygen.Moisture content.Chemical environment constitution (e.g., pH-value, presence of salts, etc.).Molecular weight and its distribution.Chemical cross-linking.Chemical structure of the polymer backbone.Morphology (difference between amorphous or semi-crystalline material).
Polymeric Materials for Printed Electronics Application
Published in Anandhan Srinivasan, Selvakumar Murugesan, Arunjunai Raj Mahendran, Progress in Polymer Research for Biomedical, Energy and Specialty Applications, 2023
Solution-processable organic semi (conductors)' utility in fabricating low-cost electronic devices with industry-oriented printing techniques makes it crucial to labor on ink formulation. This is important to fabricate devices with precision and accuracy. Even a slight defect in printing can render the device ineffective. Therefore, it is vital to control the printing parameters, and the most critical one is the ink formulation. The utmost interesting aspect of utilizing conducting polymer ink is the ink's tailor ability by playing with the polymer's structure, concentration, molecular weight, and solvent choice accordingly to formulate the desired ink. For example, the polymer can inherently be tailored for improved solubility or electron affinity by adding side chains in the polymer backbone (Aleeva & Pignataro, 2014). Polymers, being macrostructures, can also be modified intrinsically based on their molecular weight to influence ink's rheology. The increasing molecular weight of polymer strongly decreases the printability due to high elongational flow during the nozzle extrusion, as reported by Berend-Jan de Gans et al. in the inkjet printing process (De Gans et al., 2004). Higher elongational flow does not arise with printing techniques such as gravure printing, but rheology, surface tension, and spreading behavior of ink are of utmost concern (Hrehorova, Pekarovicova, & Fleming, 2006). A primary polymeric ink is composed of a functional polymer, solvent, binder, and a rheology modifier. A functional polymer is selected as per the final application. However, only after choosing the suitable functional polymer, does one determines the appropriate solvent, binder, and rheology modifier. The chemistry of the functional polymer is of great interest and is obligatory to deliberate during ink formulation. To print functional polymer onto the substrate, it is essential to solubilize it in an appropriate solvent.
Polymer Technologies
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
The grafting is other approach used for polymers functioning (Uchida and Ikada 1996; Ranby 1999; Kang and Zhang 2000; Zhao and Brittain 2000). Among the surface-modification techniques developed to date, surface grafting has emerged as a simple, useful, and versatile approach to improve surface properties of polymers for many applications. According to Gopal et al. (2007), the grafting has the following advantages: (1) the ability to modify the polymer surface to have distinct properties through the choice of different monomers; (2) the controllable introduction of graft chains with a high density and exact localization to the surface, without affecting the bulk properties; and (3) long-term chemical stability, which is assured by covalent attachment of graft chains (Gopal et al. 2007). The latter factor contrasts with physically coated polymer chains that can in principle be removed rather easily. The experiment showed that surface grafting provides versatile techniques for introducing functional groups such as amine, imine, hydroxyl, carboxylic acid, sulfonate, and epoxide onto a broad range of conventional polymeric substrates, most of which have a nonpolar, less reactive surface (see Table 19.6). As is known, hydroxyl, amine, carboxyl, and sulfone groups are hydrophilic functional groups (Van der Bruggen 2009). Usually functional groups are localized on the side chains. A typical polymer consists of a backbone, typically made up of a main chain of long strands of monomer units—from ten to millions—and side chains. A side chain is simply a relatively short branch of the polymer molecule, usually several atoms or groups of atoms, that are connected to the polymer backbone. There may be a few or many of them. Sometimes even the branches (side chains) have branches (side chains). The presence of these side chains can affect the physical properties of a polymer. For example, high-density polyethylene, with its near-absence of side chains, is harder, more abrasion resistant, and will withstand higher temperatures, compared to low-density polyethylene that has numerous molecular branches or side chains. The functional groups introduced with help of side chains can be utilized to further reaction with small or large molecules through covalent or noncovalent linkage. Functionalization is achieved by either direct grafting of functional monomer or postderivatization of graft chains.
State of art review on the incorporation of fibres in asphalt pavements
Published in Road Materials and Pavement Design, 2023
Shenghua Wu, Ara Haji, Ian Adkins
Aramid fibres are a class of extremely resilient and heat-resistant synthetic fibres, belonging to the group of aromatic polyamides (Wiśniewski et al., 2020). The fibre-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings. The fibre is produced by spinning a solid fibre from a liquid chemical blend. Aramid fibres are rather expensive and difficult to manufacture, but unlike high molecular weight polyolefin fibres, aramids have a polar aromatic polymer backbone, which results in a much higher glass transition temperature and no melting point. Due to the aromatic structure, aramid fibres have excellent heat resistance, very low flammability and good chemical resistance to most organic solvents, but are sensitive to salt (chlorine), and to some acids and bases, as well as to degradation from ultraviolet radiation.
Evaluation of dopamine and dopamine derivatives as additives in epoxy resin for structural adhesive applications
Published in The Journal of Adhesion, 2023
Ngon T. Tran, Avery J. Boyer, Casey E. Busch, Matthew A. Bartucci, Joshua A. Orlicki, Joseph L. Lenhart, Daniel B. Knorr
Because the dopamine derivatives 6 and 8 are more soluble than neutral dopamine in DGEBA/D230, we were able to perform concentration studies to help understand the effects of catechol content in epoxy formulations (Figure 6). Interestingly, the highest lap shear strengths were reached at 0.28 wt% of additive loading (based on dopamine content) for both dopamine derivatives 6 and 8 under both dry and hot/wet conditions. The shear strengths of the formulation containing maleimide-catechol (6) leveled off, while those of acrylate-maleimide polymer (8) decreased. These results suggest that the acrylate-maleimide polymer backbone may adversely affect adhesive properties at concentrations above 0.28 wt% loading of polymer 8 (based on dopamine content). This may be because catechols in the polymer in close proximity will tend to associate with each other rather than the surface.[42] Unfortunately, 0.84 wt% is approximately the upper limit of solubility in DGEBA/D230 for both dopamine derivatives, and higher catechol concentrations could not be studied.
Remaining useful life prediction of PEMFC based on CNN-Birnn model
Published in International Journal of Green Energy, 2023
Jiale Luo, Tao Chen, Fei Xiao, Yulin Peng
To improve useful life of PEMFC, study of its degradation mechanism is also one of the hot issues of discussion during last few years (Zhang et al. 2018). The main reason for short useful life of FC is failure of its parts. Parts might suffer physical or chemical variations that cause the efficiency of FC to deteriorate with increasing operating hours. (Garcia-Sanchez et al. 2020; Pei and Chen 2014). The main cause of degradation of PEM is chemical degradation because formation of hydrogen peroxide radicals (Kongkanand et al. 2014). The polymer is broken down because of the chemical reaction of radicals with the polymer backbone. As the polymer decomposes, the membrane becomes thinner or develops cracks and pinholes. This leads to an increase in hydrogen crossover, making it easier for hydrogen ions to infiltrate from anode to cathode, resulting in production of more radicals (Helmly et al. 2014). Aging of catalyst layer may occur because sintering of Pt particle or corrosion of the carbon carrier. When carbon corrosion occurs, Pt particles are susceptible to corrosion, which leads to increased ohmic resistance and activation loss (Enz et al. 2015). Gas diffusion layer (GDL) is a hydrophobic macroporous layer attached by carbon fiber and polytetrafluoroethylene (PTFE). Failure of GDL is mainly attributed to loss of carbon caused by the oxidation of the surface to CO or CO2, which leads to damage of hydrophobic materials such as PTFE. The hydrophobic properties of GDL can be lost by this and the pore structure can be altered (de Bruijn, Dam, and Janssen 2008; Huang et al. 2012).