Prepolymer
{{Short description|Monomer material which can undergo further polymerization}}
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.{{cite web |title=Prepolymer - an overview {{!}} ScienceDirect Topics |website=sciencedirect.com |url=https://www.sciencedirect.com/topics/materials-science/prepolymer |access-date=2022-02-13}}
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.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{{cite journal |last1=Harani |first1=H. |last2=Fellahi |first2=S. |last3=Bakar |first3=M. |date=1998 |title=Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters |journal=Journal of Applied Polymer Science |language=en |volume=70 |issue=13 |pages=2603–2618 |doi=10.1002/(SICI)1097-4628(19981226)70:13<2603::AID-APP6>3.0.CO;2-4 |issn=1097-4628|doi-access=free }}{{cite journal |last1=Shi |first1=Minxian |last2=Zheng |first2=Juanli |last3=Huang |first3=Zhixiong |last4=Qin |first4=Yan |date=2011-03-01 |title=Synthesis of Polyurethane Prepolymers and Damping Property of Polyurethane/Epoxy Composites |url=https://www.ingentaconnect.com/contentone/asp/asl/2011/00000004/00000003/art00020 |journal=Advanced Science Letters |volume=4 |issue=3 |pages=740–744 |doi=10.1166/asl.2011.1597}}{{cite journal |last1=Pokharel |first1=Pashupati |last2=Lee |first2=Dai Soo |date=2014-10-01 |title=High performance polyurethane nanocomposite films prepared from a masterbatch of graphene oxide in polyether polyol |url=https://www.sciencedirect.com/science/article/pii/S1385894714006214 |journal=Chemical Engineering Journal |language=en |volume=253 |pages=356–365 |doi=10.1016/j.cej.2014.05.046 |bibcode=2014ChEnJ.253..356P |issn=1385-8947}}{{cite journal |last1=Wang |first1=Lei |last2=Shen |first2=Yiding |last3=Lai |first3=Xiaojuan |last4=Li |first4=Zhongjin |last5=Liu |first5=Min |date=2011-05-01 |title=Synthesis and properties of crosslinked waterborne polyurethane |journal=Journal of Polymer Research |language=en |volume=18 |issue=3 |pages=469–476 |doi=10.1007/s10965-010-9438-9 |s2cid=56442579 |issn=1572-8935 |url=https://link.springer.com/article/10.1007/s10965-010-9438-9}} 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.{{cite journal |last=Howarth |first=GA |date=2003-06-01 |title=Polyurethanes, polyurethane dispersions and polyureas: Past, present and future |journal=Surface Coatings International Part B: Coatings Transactions |language=en |volume=86 |issue=2 |pages=111–118 |doi=10.1007/BF02699621 |s2cid=93574741 |issn=1476-4865}}
Lactic acid as a polymer precursor
{{Main|Polylactic acid}}
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.{{cite journal |last1=Vacaras |first1=Sergiu |last2=Baciut |first2=Mihaela |last3=Lucaciu |first3=Ondine |last4=Dinu |first4=Cristian |last5=Baciut |first5=Grigore |last6=Crisan |first6=Liana |last7=Hedesiu |first7=Mihaela |last8=Crisan |first8=Bogdan |last9=Onisor |first9=Florin |last10=Armencea |first10=Gabriel |last11=Mitre |first11=Ileana |date=November 2019 |title=Understanding the basis of medical use of poly-lactide-based resorbable polymers and composites - a review of the clinical and metabolic impact |url=https://pubmed.ncbi.nlm.nih.gov/31296117/ |journal=Drug Metabolism Reviews |volume=51 |issue=4 |pages=570–588 |doi=10.1080/03602532.2019.1642911 |publication-date=2019-07-24 |issn=1097-9883 |pmid=31296117|s2cid=195893132 }}
Nowadays, lactic acid is used as a monomer for producing polylactic acid (PLA) which later has application as biodegradable plastic.{{cite journal |last1=DeStefano |first1=Vincent |last2=Khan |first2=Salaar |last3=Tabada |first3=Alonzo |date=2020-01-01 |title=Applications of PLA in modern medicine |journal=Engineered Regeneration |language=en |volume=1 |pages=76–87 |doi=10.1016/j.engreg.2020.08.002 |issn=2666-1381|doi-access=free |pmid=38620328 |pmc=7474829 }} 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
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