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Interaction of admixtures in the cement-water system
Published in A. M. Paillère, Application of Admixtures in Concrete, 1994
Water reducers consist of Ca, Na or NH4 salts of lignosulphonic acid, Na, NH4 or triethanolamine salts of hydroxycarboxylic acid and carbohydrates. Lignosulphonates containing (OH), (COOH) and SO3H groups are more widely used than others. Hydroxycarboxylic acids, such as citric acid, tartaric acid, salicylic acid, heptonic acid, saccharic acid and gluconic acid, contain (OH) and (COOH) groups. Gluconic acid-based admixtures are used extensively. Carbohydrates include glucose, sucrose or hydroxylated polymers obtained by partial hydrolysis of saccharides. The role of water reducers (normal, accelerating or retarding) in terms of their effect on hydration of cement s similar to that of retarders, accelerators and superplasticizers. The effect of some accelerating and retarding admixtures has already been discussed. In this section the interaction of lignosulphonates with cement will be emphasized.
Polylactic Acid: An Eco-Friendly Material in the Packaging Industry, Paving the Way Toward a Greener Environment
Published in Neha Kanwar Rawat, Iuliana Stoica, A. K. Haghi, Green Polymer Chemistry and Composites, 2021
S. Roopa, B. Sowmya, S. Preethi, Arul Maximus Rabel
PLA is thermoplastic aliphatic polyester which comprises of lactic acid repeating units. Lactic acid, a natural hydroxycarboxylic acid has been used in pharmaceutical, food industries, leather tanning, personal care, and in the production of polymers. About 39% of lactic acid is consumed for the production of biodegradable/biocompatible PLA polymer (Komesu et al., 2017). The chemical structure of lactic acid is given below (Fig. 4.1):
Development of Green Technology Through Renewable and Sustainable Materials
Published in Shrikaant Kulkarni, Ann Rose Abraham, A. K. Haghi, Renewable Materials and Green Technology Products, 2021
Remya Vijayan, Sijo Francis, Beena Mathew
Inventions of versatile chemical resources from renewable and sustainable materials have attained significant attraction in recent years. In this regard, the production of lactic acid from bacteria is seen as an option to cope with environmental problems and is cost-effective. Lactic acid (2-hydroxy propionic acid or 2-hydroxypropanoic acid) is an important organic acid with molecular formula CH3CHOHCOOH. It is a chiral molecule, which exists as enantiomers L- and D-lactic acid. The lactic acid can be synthesized by using chemical synthesis and by microbial fermentation. By chemical synthesis, a racemic mixture of D- and L-lactic acid is obtained. But in the microbial fermentation process, an optically pure L(+)- or D(-)-lactic acid is obtained.52 Also, this method has many advantages compared to chemical synthesis. Various inexpensive materials like molasses and other residues from agriculture and agro-industry have been used as substrates for lactic acid fermentation. Moreover, the efficiency of microorganisms for lactic acid synthesis can be enhanced by gene modification.53,54 The lactic acid is extensively used in the pharmaceutical, cosmetic, food, and chemical industries. Lactic acid is regarded as one of the most important hydroxycarboxylic acids because of its versatile applications as a flavoring, inhibitor of bacteria, and acidulant. Lactic acid can be easily converted into potentially useful chemicals such as various acids, esters, and biosolvents since it contains both carboxyl and hydroxyl groups.55 Lactic acid is also used as a feedstock monomer for the production of biodegradable poly-L-lactic acid, a superior substitute for synthetic polymers derived from petroleum resources.56,57 In the sonochemical synthesis of pyrrole derivatives, lactic acid acts as a bio-based green solvent. Andreev et al. stated that lactic acid fermentation helped to decrease the number of pathogens and to reduce the nutrient loss and hence increasing the agricultural value of plants.58 Thus, the demand for lactic acid has been increasing significantly because of its various promising applications.
The influence of iodate ion additions to the bath on the deposition of electroless nickel on mild steel
Published in Transactions of the IMF, 2018
S. Court, C. Kerr, C. Ponce de León, B. D. Barker, J. R. Smith, F. C. Walsh
Complexants prevent the precipitation of Ni salts and reduce the concentration of free Ni ions. Typical examples include potassium pyrophosphate, malic acid, lactic acid, glycolic acid, monocarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, ammonia and alkanolamines.15 In addition, complexing agents also affect the deposition reaction often altering the phosphorus content of the Ni deposit and the structure of the deposit.16 Jin et al. studied the effects of three complexing agents (sodium citrate, malic acid and lactic acid) on the morphology and porosity of deposits.17 It was noted that the porosity and surface roughness of mild steel substrates decreases with the increasing stability of the Ni complex.