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Materials and Processes for Textile Warp Sizing
Published in Menachem Lewin, Stephen B. Sello, Handbook of Fiber Science and Technology: Volume I Chemical Processing of Fibers and Fabrics, 2018
Peter G. Drexler, Giuliana C. Tesoro
A dihydric alcohol, neopentyl glycol (NPG), and an aromatic polycarboxylic acid, trimellitic anhydride (TMA), are reacted at various molar ratios (see Table 1.9) at 360°C for 2 hr, to yield a low-molecular weight polyester with a high acid number. The product, when tested in the water-soluble, ammonium-salt form, yields films of good flexibility, hardness, and adhesion. In order to reduce moisture sensitivity and tack, another approach has been described [56]. Isophthalic acid is reacted at 230°C for 16 hr with polyethylene glycol and neopentyl glycol until the acid number of the mixture decreases to 15–14. At this stage, trimethylol propane and trimellitic anhydride are added, and the system is further reacted for 4 hr. The endpoint of the reaction is indicated by a final acid number of 40–42. The polyester resin obtained is then diluted to 30% activity, yielding a product which is readily dispersible in water, and a high number of free carboxyl groups which can be neutralized to attain water solubility. In the free acid form, the dispersion has excellent hydrolytic stability (up to 2 years). This polyester resin has been used in combination with PVA (8% PE: 92% PVA) to give improved results on 50/50 PE/cotton when compared with an acrylic/PVA combination (8% acrylic: 92% PVA) and with PVA alone.
Properties
Published in B. T. Åström, Manufacturing of Polymer Composites, 2018
Table 3-14 gives mechanical properties of glass-fiber reinforced polyester. For Wf = 0.34 the reinforcement was a chopped strand mat; for Wf = 0.47 and 0.53 the reinforcement was a combination mat consisting of a balanced woven fabric and a random mat; while for Wf = 0.61 the reinforcement was the combination mat together with a UD fabric. The resin was a so-called isophthalic NPG-polyester (i.e. formed using neopentyl glycol) and manufacturing was achieved through hand layup. The table clearly illustrates that strengths and stiffnesses increase with fiber fraction in the qualitative fashion that the relationships of Section 3.3.2 indicate. Further, the tensile strength perpendicular to the laminate is only a fraction of the in-plane strength and a fifth of the tensile strength of the neat matrix, apparently indicating unfavorable fiber-matrix bonding. It is also noteworthy that the high strain to failure of the matrix is not translated into the composite.
Thermo-Oxidative Stability of Base Oils for Green Lubricants
Published in Brajendra K. Sharma, Girma Biresaw, Environmentally Friendly and Biobased Lubricants, 2016
Pattathilchira Varghese Joseph, Deepak Saxena
Most of the commercially viable routes for upgrading vegetable oils depend on chemical modification and physical separation. Chemical modification of vegetable oils to improve oxidation stability is still under active investigation. More than 90% of chemical modifications have been those occurring at the fatty acid carboxyl group, while less than 10% have involved reactions at the fatty acid hydrocarbon chain [77]. Synthetic methods applied include transesterification, selective hydrogenation, dimerization/oligomerization, C−C and C−O bond formation for branched molecules, hydroformylation, Friedel–Crafts alkylation, Friedel-Crafts acylation, ene reaction, radical addition, acyloxylation, metathesis, and oxidation reactions (such as epoxidation and oxidative cleavage) [77–81]. Vegetable oils with predominantly unsaturated fatty acids can be converted to products with better thermo-oxidative properties and at the same time maintaining the same viscosity temperature characteristics and lubricity [82]. Vegetable oils transesterified with TMP, PE, and neopentyl glycol have been found to possess better lubricant properties including thermo-oxidative stability and low pour points [83]. These esters have been in the market for formulating synthetic and semisynthetic lubricants with special focus on biodegradability, environmental friendliness, energy efficiency, and long sump life [84]. In epoxidation process the olefinic double bond is saturated by attachment of oxygen between the adjoining carbons of the double bond, forming a three-membered ring. Epoxides are highly viscous oils and are further converted to diesters and other derivatives for lubricant application [85]. Chemical modification in combination with blending additives offers the greatest opportunity for formulating high-performance biolubricants [75].
Hitherto Unexplored Three-Membered Heterocyclic Rings Favorably Alter Tribological Properties of Fatty Acid Linear Esters
Published in Tribology Transactions, 2021
Neha Sharma, Gananath D. Thakre, Anjan Ray
Experimentally, it has been observed that long-chain saturated fatty acids and their corresponding ester derivatives possess relatively poor flow properties at room temperature and are therefore rendered unsuitable as lubricant base fluids. On the contrary, long-chain esters of cis-unsaturated acids such as oleic (cis-9-octadecenoic) acid are widely used for high-viscosity lubricant formulations (5–8). Diesters of iso-hexanol (containing an unusual branched carbon chain in their saturated fatty acids) are used for lubricant formulations suitable for low-temperature applications. The presence of less densely packed structures (due to branching) in these diesters makes them suitable candidates for low-temperature applications. On the other hand, polyol esters, particularly trimethylolpropane esters of unsaturated fatty acids, a diester of neopentyl glycol, etc., are used as base fluids for high-temperature lubricant formulations due to the relatively improved thermal stability. They find application in metalworking, machinery oils, hydraulic fluids, etc. (8–11). Furthermore, surface-active glycerol-based monoesters and amides of unsaturated and saturated long-chain fatty acids are widely used as extreme pressure (EP) additives.
Vegetable Oil Based Compressor Oil-optimising of Tribological Characteristics
Published in Australian Journal of Mechanical Engineering, 2022
P. Chengareddy, Arumugam Shanmugasundaram
In this context, Hashem et al. (2013a, 2013b) formulated polyolester from various vegetable oils through a conventional transesterification process. They concluded that vegetable oil-based polyolester exhibited outstanding thermo-oxidative stability with improved cold flow behaviour. Zulkifli et al. (2014, 2014, 2016) synthesised trimethylolpropane (TMP) and pentaerythritol ester (PE) based polyolester from palm oil and conducted a tribological study using four-ball tribometer, and proved that under the mixed lubrication regime, PE had excellent friction and wear reduction characteristics as compared to TMP ester. Aziz et al. (2016) developed a polyol ester-based lubricant, i.e. pentaerythritol ester (PE) and neopentyl glycol ester (NPG) and executed the tribological experiments and compared it with commercial lubricants (CL). They observed lower coefficient of friction and wear scar diameter for PE compared to CL and NPG. Vithya, Sriram, and Arumugam (2021a, 2021b) optimised the tribological properties of vegetable oil-based polyol ester refrigeration oil and carried out an experimental work using pin-on-disc tribometer under various load and speed conditions by adapting response surface methodology (RSM) based D-optimal design. They found that the vegetable oil-based refrigeration oil blended with commercial refrigeration oil showed superior lubrication properties as compared to vegetable oil-based PE and commercial refrigeration oil. Besides, numerous researchers reported that polyolester-based vegetable oils found extensive attention in a variety of industrial lubricants (Mahmud, Salih, and Salimon 2015; Sripada, Sharma, and Dalai 2013).