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Waterborne Polyurethanes for Automobile Industries
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Li et al. [41] prepared eco-friendly waterborne polyurethanes using toluene diisocyanate, polypropylene glycol, and ethylene glycol monomers. Eco-friendly waterborne polyurethanes were designed using different soft and hard segment contents. Toluene diisocyanate formed hard segments, whereas polypropylene glycol constituted the soft segments in the eco-friendly polyurethane. Figure 23.4 shows the differential scanning calorimetry (DSC) curves of waterborne polyurethanes. The mixing degree of the soft and hard segments was analyzed. The glass transition temperature (Tg) and enthalpy (ΔH) were premeditated from the DSC thermograms. The 3:2 ratio of soft and hard segments revealed phase separation, as confirmed by the higher ΔH value of ∼6.278 J/g among all the compositions. Phase separation caused the lower Tg value for this composition. Endothermic peaks indicated the crystallinity of the adhesives. In the case of the T-peel strength of the adhesives, the 4:1 ratio of the segments caused the higher value of 136.14 N/25 mm (Figure 23.5). Adhesive strength was found to be lower for the 3:2 sample, at 21.55 N/25 mm. The lower adhesive strength of the 3:2 soft and hard segments also indicated phase separation in waterborne polyurethane. Lesser phase separation properties produced lesser porosity in adhesives, thus proceeding the adhesive properties. Therefore, eco-friendly waterborne polyurethane adhesives have been found to be efficient at forming strong bonds in automobile applications.
Cyclopolymerization Leading to Polycyclic Systems
Published in George B. Butler, Cyclopolymerization and Cyclocopolymerization, 2020
The polymerization of oligourethane acrylates has been studied. Gelation of polypropylene glycol-ethylene glycol monomethacrylate-2,4-tolylene diisocyanate copolymer occurred quite early during the copolymerization at low diisocyanate conversion.31 This early gelling was reported to be due to the cyclization of the oligomeric chains and a decrease in their sequential mobilities. This configuration gives a higher probability of intramolecular cyclization than of intermolecular crosslinking.
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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Polypropylene glycol) and random copolymers of propylene oxide and ethylene oxide are used as so-called functional fluids. Their characteristic properties arising from the nature of the polyether backbone suit them to a large variety of applications such as hydraulic fluids, quenchants, lubricants, and surfactants.
Enhanced corrosion resistance of adhesive/galvanised steel interfaces by nanocrystalline ZnO thin film deposition and molecular adhesion promoting films
Published in The Journal of Adhesion, 2022
Richard Grothe, Jan Striewe, Dennis Meinderink, Thomas Tröster, Guido Grundmeier
A model adhesive was used for the polymer phase consisting of two epoxy and one amine components. These were bisphenol A diglycidyl ether (DGEBA, DER 332, Dow Chemical, USA), diglycidyl ether of polypropylene glycol (DGEPG, DER 736, Dow Chemical, USA) and Jeffamine (D 230, Huntsman Corporation, USA). For the preparation of polymer films, the before mentioned base components were merged in a beaker and then stirred (at 0.4 bar for 2 min) and degassed (at 0.05 bar for 2 h) in a desiccator. The model adhesive was applied onto the metal surfaces under dry atmosphere (< 8% RH) in a glovebox to exclude oxygen and moisture. A uniform film thickness of 150 µm was achieved with Al foil-covered polytetrafluorethylene (PTFE) blocks, clamps and self-adhesive tapes as spacers. The adhesive was cured for 2 h at 130°C in a drying oven, resulting in a pore-free and free-standing film.
Fabrication of novel eco-friendly hybrid biocomposites based on carboxymethyl chitosan /polypropylene glycol @ activated carbon for the efficient removal of Cr (III) from the aquatic medium
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Eslam A. Mohamed, Amal A. Altalhi, Nabel A. Negm
Initially, the formation of carboxymethyl chitosan was confirmed by the presence of an intense absorption near 1734 cm−1 corresponding to the formed ester groups, which proved the methylation of chitosan CMCN (Figure 1a) (Hemming et al. 2019). The reaction between carboxymethyl chitosan and propylene oxide in the presence of chloroacetic acid revealed the formation of carboxymethyl chitosan polypropylene glycol polymer (CMCN-PG). The formation of CMCN-PG was confirmed by the presence of similar absorption bands of chitosan with the relative increase in the intensities of the three bands at 1100 cm−1 corresponded to ether groups of the formed propylene glycol as the result of the grafting of propylene glycol units in the main structure of chitosan, 2920 and 2870 cm−1 assigned for symmetric and asymmetric stretching bands of aliphatic C-H of polypropylene glycol units, which increased by increasing the propylene glycol units (Negm et al. 2012; Ulu et al. 2020).
Effect of mineral particle size on froth stability
Published in Mineral Processing and Extractive Metallurgy, 2021
Innocent Achaye, Jenny Wiese, Belinda McFadzean
A polypropylene glycol ether frother, Dowfroth 250, was used at a constant dosage of 100 ppm. A high frother dosage was necessary to run all the experiments in the bench scale continuous column under the same conditions, otherwise the froth volume obtained with coarse particles would be insufficient to get an acceptable mass flow to the concentrate. The glass wall does not offer a stabilising effect as it is hydrophilic and drainage was high at the surface. Potassium amyl xanthate (PAX) was used as collector at 25% surface coverage of pyrite, corresponding to a pyrite contact angle of 46°. The collector surface coverage was based on the BET surface area of the pyrite and assuming the cross-sectional area of the thiol head group of xanthate to be 28.8 Å (Grano et al. 1997). The collector dosage was chosen to give an intermediate particle hydrophobicity that would generate some pyrite recovery, but not high enough to destabilise the froth.