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Polyvinyl Alcohol and Polyvinyl Acetate
Published in Abdullah Al-Mamun, Jonathan Y. Chen, Industrial Applications of Biopolymers and their Environmental Impact, 2020
The radical formed at either the tertiary carbon atom or at the acetate group will then initiate polymerisation and form branched structures. Since polyviny1 acetate is usually used in an emulsion form, the emulsion polymerisation process is commonly used. In a typical system, approximately equal quantities of vinyl acetate and water are stirred together in the presence of a suitable colloid-emulsifier system, such as polyviny1 alcohol and sodium lauryl sulphate, and a water-soluble initiator such as potassium persulphate. Polymerisation takes place over a period of about 4 hours at 70°C. The reaction is exothermic and provision must be made for cooling when the batch size exceeds a few liters. In order to achieve better control of the process and to obtain particles with a smaller particle size, part of the monomer is first polymerised and the rest, with some of the initiator, is then steadily added over a period of 3–4 hours. To minimise the hydrolysis of vinyl acetate or possible comonomers during polymerisation, it is necessary to control the pH throughout reaction. For this purpose, a buffer such as sodium acetate, is commonly employed.
EEMS2015 organizing committee
Published in Yeping Wang, Jianhua Zhao, Advances in Energy, Environment and Materials Science, 2018
At present, we often use the external carbon sources such as methanol, sodium acetate, and glucose to solve the problem of insufficient carbon source. Methanol is a kind of colorless, transparent, flam- mable, volatile, toxic liquid, as carbon source, it is expensive and toxic determine, in operation unsafe, easy to employee health harm. Glucose is a kind of simple carbohydrates, is the most widely distributed in nature and most important a monosaccharide. It can also be as a carbon source; sodium acetate is colorless, odorless, crystalline, soluble in water, slightly soluble in ethanol, insoluble ether. The mate- rials such as water hydrolysis, alkali, sodium acetate as carbon source are widely used. De-nitrification process mainly includes aerobic nitrification and anaerobic de-nitrification, in which aerobic nitri- fication occurred in the two-stage biological aer- ated filter, effluent total nitrogen for 2430 mg/L, and the COD value only 5060 mg/L, cannot meet the normal survival needs of denitrifying bacteria; anaerobic de-nitrification occurred in a denitrify- ing bio-filter. Therefore, it is necessary to denitrify bio-filter to add carbon source.
FEA Based Design and Stability Study of Electroless Ni-P Coating Plated over a Stepped Shaft under Thermal Load
Published in Australian Journal of Mechanical Engineering, 2023
Tarik Hassan, Subhasish Sarkar, Tapendu Mandal, Nitesh Mondal, Gautam Majumdar
Nickel sulphate is used as the source of nickel with sodium hypophosphite which is the reducing agent and sodium citrate is added as a complexing agent. Sodium acetate was used in the bath works as a buffering agent and stabilises the pH of the solution. The pH of the solution is maintained at around 9 by continuous monitoring with a pH meter, and the temperature of the bath is maintained at 85°C by an automated heating system. Details of the bath parameters are provided in Table 1. Four copper substrates are dipped into the electroless bath having a volume of 250 ml and deposition is carried out for a period of 80 minutes. After that, the substrates coated with Ni-P are taken out of the bath and rinsed in distilled water. The coated sample is then dried and mounted with the help of epoxy resin. It is done with utmost caution as the sample is very thin (0.3 mm). Special care is also provided to assure proper adhesion of the sample to the mounting material.