Physics:Prepolymer
In polymer chemistry, the term prepolymer or pre-polymer, refers to a monomer or system of monomers that have been reacted to an intermediate-molecular mass state. This material is capable of further polymerization by reactive groups to a fully cured, high-molecular-mass state. As such, mixtures of reactive polymers with un-reacted monomers may also be referred to as pre-polymers. The term "pre-polymer" and "polymer precursor" may be interchanged.[citation needed]
Polyurethane and polyurea prepolymers
In polyurethane chemistry, prepolymers and oligomers are frequently produced and then further formulated into CASE applications - Coatings, Adhesives, Sealants, and Elastomers. An isocyanate (usually a diisocyanate) is reacted with a polyol. All types of polyol may in theory be used to produce polyurethane prepolymers.[1][2][3][4][5] These then find use in CASE applications. When polyurethane dispersions are synthesized, a prepolymer is first produced usually modified with DMPA. In polyurea prepolymer production, instead of a polyol a polyamine is used.[6]
Lactic acid as a polymer precursor
Two molecules of lactic acid can be dehydrated to the cyclic molecule lactide, a lactone. A variety of catalysts can polymerise lactide to either heterotactic or syndiotactic polylactide, which as biodegradable polyesters with valuable (inter alia) medical properties are currently attracting much attention.[7]
Nowadays, lactic acid is used as a monomer for producing polylactic acid (PLA) which later has application as biodegradable plastic.[8] This kind of plastic is a good option for substituting conventional plastic produced from petrochemicals because of low emission of carbon dioxide. The commonly used process in producing lactic acid is via fermentation; to obtain the polylactic acid, the polymerization process follows.
See also
References
- ↑ Howarth G.A "Synthesis of a legislation compliant corrosion protection coating system based on urethane, oxazolidine and waterborne epoxy technology" page 40 Master of Science Thesis April 1997 Imperial College London
- ↑ Harani, H.; Fellahi, S.; Bakar, M. (1998). "Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters". Journal of Applied Polymer Science 70 (13): 2603–2618. doi:10.1002/(SICI)1097-4628(19981226)70:13<2603::AID-APP6>3.0.CO;2-4.
- ↑ Shi, Minxian; Zheng, Juanli; Huang, Zhixiong; Qin, Yan (March 2011). "Synthesis of Polyurethane Prepolymers and Damping Property of Polyurethane/Epoxy Composites". Advanced Science Letters 4 (3): 740–744. doi:10.1166/asl.2011.1597.
- ↑ Pokharel, Pashupati; Lee, Dai Soo (October 2014). "High performance polyurethane nanocomposite films prepared from a masterbatch of graphene oxide in polyether polyol". Chemical Engineering Journal 253: 356–365. doi:10.1016/j.cej.2014.05.046. Bibcode: 2014ChEnJ.253..356P.
- ↑ Wang, Lei; Shen, Yiding; Lai, Xiaojuan; Li, Zhongjin; Liu, Min (May 2011). "Synthesis and properties of crosslinked waterborne polyurethane". Journal of Polymer Research 18 (3): 469–476. doi:10.1007/s10965-010-9438-9.
- ↑ Howarth, Ga (June 2003). "Polyurethanes, polyurethane dispersions and polyureas: Past, present and future". Surface Coatings International Part B: Coatings Transactions 86 (2): 111–118. doi:10.1007/BF02699621.
- ↑ Vacaras, Sergiu; Baciut, Mihaela; Lucaciu, Ondine; Dinu, Cristian; Baciut, Grigore; Crisan, Liana; Hedesiu, Mihaela; Crisan, Bogdan et al. (2 October 2019). "Understanding the basis of medical use of poly-lactide-based resorbable polymers and composites – a review of the clinical and metabolic impact". Drug Metabolism Reviews 51 (4): 570–588. doi:10.1080/03602532.2019.1642911. PMID 31296117.
- ↑ DeStefano, Vincent; Khan, Salaar; Tabada, Alonzo (2020). "Applications of PLA in modern medicine". Engineered Regeneration 1: 76–87. doi:10.1016/j.engreg.2020.08.002. PMID 38620328.
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