{{Chembox | Reference = <!-- Names --> | Name = Polypropylene glycol | OtherNames = Propylene oxide homopolymer<BR />Poly (propene oxide) <BR /> | ImageFile = Polypropylenglycol.svg | ImageClass = skin-invert | Section1 = {{Chembox Identifiers | 3DMet = | Abbreviations = | Beilstein = | CASNo = 25322-69-4 | CASNo_Ref = {{cascite|correct|CAS}} | UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 01SEY4236K | CASNo_Comment = | CASNoOther = 106-62-7 | ChEBI = | ChemSpiderID = | EINECS = | EC_number = | EC_number_Comment= | Gmelin = | InChI = | KEGG = | MeSHName = | PubChem = | RTECS = | SMILES = | UNNumber = }} | Section2 = {{Chembox Properties | AtmosphericOHRateConstant = | Appearance = | BoilingPt = | BoilingPtC = | BoilingPt_ref = | BoilingPt_notes= | Density = | Formula = C<sub>3n</sub>H<sub>6n+2</sub>O<sub>n+1</sub> | HenryConstant = | LogP = | MolarMass = 58.08n + 18.08 (repeat unit), mass of polymer variable | MeltingPt = | MeltingPtC = | MeltingPt_ref = | MeltingPt_notes= | pKa = | pKb = | Solubility = | SolubleOther = | Solvent = | VaporPressure = }} | Section3 = {{Chembox Structure | Coordination = | CrystalStruct = | MolShape = }} | Section4 = {{Chembox Thermochemistry | DeltaGf = | DeltaHc = | DeltaHf = | Entropy = | HeatCapacity = }} | Section5 = {{Chembox Explosive | ShockSens = | FrictionSens = | DetonationV = | REFactor = }} | Section6 = {{Chembox Pharmacology | ATCvet = | ATCCode_prefix = | ATCCode_suffix = | ATC_Supplemental= | AdminRoutes = | Bioavail = | Excretion = | HalfLife = | Metabolism = | Legal_status = | Legal_AU = | Legal_AU_comment= | Legal_CA = | Legal_CA_comment= | Legal_NZ = | Legal_NZ_comment= | Legal_US = | Legal_US_comment= | Legal_UK = | Legal_UK_comment= | Legal_EU = | Legal_EU_comment= | Legal_UN = | Legal_UN_comment= | Pregnancy_category = | Pregnancy_AU = | Pregnancy_AU_comment = | ProteinBound = | Dependence_liability = | Addiction_liability = }} | Section7 = {{Chembox Hazards | AutoignitionPt = | ExploLimits = | FlashPt = | LD50 = | LC50 = | MainHazards = | NFPA-H = | NFPA-F = | NFPA-I = | NFPA-S = | PEL = | REL = | ExternalSDS = | GHSPictograms = | GHSSignalWord = | HPhrases = | PPhrases = }} | Section9 = {{Chembox Related | OtherAnions = | OtherCations = | OtherFunction = | OtherFunction_label = | OtherCompounds = }} }} '''Polypropylene glycol''' or '''polypropylene oxide''' is the polymer (or macromolecule) of propylene glycol.<ref>{{Cite web |work = PubChem |title=2-(2-Hydroxypropoxy)propan-1-ol |url=https://pubchem.ncbi.nlm.nih.gov/compound/32881 |access-date=2022-11-14 |publisher = U.S. National Library of Medicine |language=en}}</ref> Chemically it is a polyether, and, more generally speaking, it's a polyalkylene glycol (PAG) H S Code 3907.2000.{{huh|date=May 2026}} The term polypropylene glycol or '''PPG''' is reserved for polymer of low- to medium-range molar mass when the nature of the end-group, which is usually a hydroxyl group, still matters. The term "oxide" is used for high-molar-mass polymer when end-groups no longer affect polymer properties. Between 60 and 70% of propylene oxide is converted to polyether polyols by the process called alkoxylation.<ref>{{Ullmann|vauthors = Adam N, Avar G, Blankenheim H, Friederichs W, Giersig M, Weigand E, Halfmann M, Wittbecker FW, Larimer DR, Maier U, Meyer-Ahrens S, Noble KL, Wussow HG | display-authors = 6 |date=2005 |title=Polyurethanes |doi=10.1002/14356007.a21_665.pub2}}</ref>

== Polymerization == Polypropylene glycol is produced by ring-opening polymerization of propylene oxide. The initiator is an alcohol and the catalyst a base, usually potassium hydroxide. When the initiator is ethylene glycol or water the polymer is linear. With a multifunctional initiator like glycerine, pentaerythritol or sorbitol the polymer branches out.

300px|center|Polypropylene glycol

Conventional polymerization of propylene oxide results in an atactic polymer. The isotactic polymer can be produced from optically active propylene oxide, but at a high cost. A salen cobalt catalyst was reported in 2005 to provide isotactic polymerization of the prochiral propylene oxide<ref name="pmid16104709">{{cite journal | vauthors = Peretti KL, Ajiro H, Cohen CT, Lobkovsky EB, Coates GW | title = A highly active, isospecific cobalt catalyst for propylene oxide polymerization | journal = Journal of the American Chemical Society | volume = 127 | issue = 33 | pages = 11566–7 | date = August 2005 | pmid = 16104709 | doi = 10.1021/ja053451y }}</ref>

== Properties == PPG has many properties in common with polyethylene glycol. The polymer is a liquid at room temperature. Solubility in water decreases rapidly with increasing molar mass. Secondary hydroxyl groups in PPG are less reactive than primary hydroxyl groups in polyethylene glycol. PPG is less toxic than PEG, so biotechnologicals are now mainly produced with PPG.<ref>{{cite journal | vauthors = Thurman EM, Ferrer I, Rosenblum J, Linden K, Ryan JN | title = Identification of polypropylene glycols and polyethylene glycol carboxylates in flowback and produced water from hydraulic fracturing | journal = Journal of Hazardous Materials | volume = 323 | issue = Pt A | pages = 11–17 | date = February 2017 | pmid = 26947804 | doi = 10.1016/j.jhazmat.2016.02.041 | series = Special Issue on Emerging Contaminants in engineered and natural environment | doi-access =free }}</ref><ref>{{cite journal | vauthors = Wang R, Hughes T, Beck S, Vakil S, Li S, Pantano P, Draper RK | title = Generation of toxic degradation products by sonication of Pluronic® dispersants: implications for nanotoxicity testing | journal = Nanotoxicology | volume = 7 | issue = 7 | pages = 1272–1281 | date = November 2013 | pmid = 23030523 | pmc = 3657567 | doi = 10.3109/17435390.2012.736547 }}</ref><ref>{{Cite journal | vauthors = Thangavelu SA, Mukherjee M, Layana K, Kumar CD, Sulthana YR, Kumar RR, Ananthan A, Muthulakshmi V, Mandal AB | display-authors = 6 |date=2020-06-15 |title=Biodegradable polyurethanes foam and foam fullerenes nanocomposite strips by one-shot moulding: Physicochemical and mechanical properties |journal=Materials Science in Semiconductor Processing |language=en |volume=112 |article-number=105018 |doi=10.1016/j.mssp.2020.105018 |s2cid=213206957 |issn=1369-8001}}</ref>

<gallery widths=200 heights=160> File:Polypropylene oxide catalyst.svg|Cobalt catalyst for isotactic polypropylene oxide File:PPG4000vsPPG400WaterSolubility.jpg|Difference in water solubility of PPG4000 and PPG400 </gallery>

== Uses == PPG is used in many polyurethane formulations.<ref>{{Cite journal | vauthors = Chattopadhyay DK, Raju NP, Vairamani M, Raju KV |date=2008-04-01 |title=Structural investigations of polypropylene glycol (PPG) and isophorone diisocyanate (IPDI) based polyurethane prepolymer by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-mass spectrometry |journal=Progress in Organic Coatings |language=en |volume=62 |issue=2 |pages=117–122 |doi=10.1016/j.porgcoat.2007.09.021 |issn=0300-9440}}</ref><ref>{{Cite journal | vauthors = Xu Z, Cui Y, Li T, Dang H, Li J, Cheng F |date=July 2020 |title=Enhanced Mechanical and Shape Memory Properties of Poly(propylene glycol)‐Based Star‐Shaped Polyurethane |journal= Macromolecular Chemistry and Physics |language=en |volume=221 |issue=13 |article-number=2000082 |doi= 10.1002/macp.202000082 |s2cid=225563251 |issn=1022-1352}}</ref> Synthesis of waterborne polymers has been a feature with this substance.<ref>{{Cite patent | inventor = Kim KJ, Hu R, Grove JL | assign1 = Arkema Inc | country = US | title = Water soluble polymers and polymer adducts along with aqueous solutions thereof Patent | number = 10920011 | gdate = 16 February 2021 }}</ref> As the basic building block is propylene oxide, there are 3 carbons per oxygen on the backbone. This confers some degree of water miscibility though not as good as ethylene oxide-based molecules.<ref>{{cite thesis | vauthors = Howarth GA | title = Synthesis of a legislation compliant corrosion protection coating system based on urethane, oxazolidine and waterborne epoxy technology | pages = 36-28, 52-60 | degree = Master of Science | date = April 1997 | publisher = Imperial College | location = London }}</ref> It is used to synthesize the epoxy reactive diluent and flexibilizer, Poly(propylene glycol) diglycidyl ether.<ref>{{Cite journal | vauthors = Crivello JV |date=2006 |title=Design and synthesis of multifunctional glycidyl ethers that undergo frontal polymerization |journal=Journal of Polymer Science Part A: Polymer Chemistry |volume=44 |issue=21 |pages=6435–6448 |doi=10.1002/pola.21761 |bibcode=2006JPoSA..44.6435C |issn=0887-624X}}</ref><ref>{{Cite patent|country=US|pubdate=1992-11-10|assign1=Ciba-Geigy Corp.|number=5162547|title=Process for the preparation of glycidyl ethers|=|inventor = Roth M, Wolleb H, Truffer MA }}</ref> Another use of PPG is as a surfactant, wetting agent and dispersant in leather finishing.<ref>{{cite journal | vauthors = Zgoła-Grześkowiak A, Grześkowiak T, Zembrzuska J, Łukaszewski Z | title = Comparison of biodegradation of poly(ethylene glycol)s and poly(propylene glycol)s | journal = Chemosphere | volume = 64 | issue = 5 | pages = 803–809 | date = July 2006 | pmid = 16343594 | doi = 10.1016/j.chemosphere.2005.10.056 | bibcode = 2006Chmsp..64..803Z }}</ref> PPG is also employed as a reference and calibrant in mass spectrometry and HPLC.<ref>{{cite journal | vauthors = Rychłowska J, Zgoła A, Grześkowiak T, Lukaszewski Z | title = Isolation of poly(propylene glycol)s from water for quantitative analysis by reversed-phase liquid chromatography | journal = Journal of Chromatography A | volume = 1021 | issue = 1–2 | pages = 11–17 | date = December 2003 | pmid = 14735971 | doi = 10.1016/j.chroma.2003.09.003 }}</ref><ref>{{Cite journal | vauthors = Castillo M, Ventura F, Barceló D |date=1999-04-01 |title=Sequential solid phase extraction protocol followed by liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry for the trace determination of non ionic polyethoxylated surfactants in tannery wastewaters |url=https://www.sciencedirect.com/science/article/pii/S0956053X99000045 |journal=Waste Management |language=en |volume=19 |issue=2 |pages=101–110 |doi=10.1016/S0956-053X(99)00004-5 |issn=0956-053X|url-access=subscription }}</ref> PPG and derivatives may be used as defoamers in drilling and other applications.<ref>{{Cite journal | vauthors = Tan SN, Pugh RJ, Fornasiero D, Sedev R, Ralston J |date= February 2005 |title=Foaming of polypropylene glycols and glycol/MIBC mixtures ] |journal=Minerals Engineering |series=Reagents '04 |language=en |volume=18 |issue=2 |pages=179–188 |doi=10.1016/j.mineng.2004.08.017 |issn=0892-6875}}</ref><ref>{{Cite book | vauthors = Bava L, Mahmoudkhani A, Wilson R, Levy L |date=2013-03-23 |title=New Generation of Green Defoamers for Challenging Drilling and Cementing Applications |chapter=New Generation of "Green" Defoamers for Challenging Drilling and Cementing Applications |chapter-url=https://onepetro.org/SPEOKOG/proceedings/13POS/All-13POS/SPE-164504-MS/177686 |language=en |publisher=OnePetro |doi=10.2118/164504-MS}}</ref> It is also used as a primary ingredient in the making of paintballs.<ref>{{Cite journal | vauthors = Dhiman M, Singh K, Gupta DP, Singh DP, Upmanyu A |date=2020-05-04 |title=Study of excess acoustical and thermo-dynamical parameters of binary solutions of polypropylene glycol-400 and n-alkanols at 303 K |url=https://aip.scitation.org/doi/abs/10.1063/5.0001107 |journal=AIP Conference Proceedings |volume=2220 |issue=1 |page=080001 |doi=10.1063/5.0001107 |s2cid=218923617 |issn=0094-243X|url-access=subscription }}</ref> It has been evaluated as a corrosion inhibitor.<ref>{{Cite journal | vauthors = Solomon MM, Umoren SA, Israel AU, Etim IG |date= January 2016 |title=Synergistic inhibition of aluminium corrosion in H2SO4 solution by polypropylene glycol in the presence of iodide ions |journal=Pigment & Resin Technology |volume=45 |issue=4 |pages=280–293 |doi=10.1108/PRT-01-2015-0010 |issn=0369-9420}}</ref>

== References == {{Reflist}}

==External websites== * [https://monumentchemical.com/products/solvents-intermediates?id=558455&category_id=557047 Polypropylene Glycol (PPG) | Monument Chemical] * [https://cameochemicals.noaa.gov/chemical/9002 POLYPROPYLENE GLYCOL | CAMEO Chemicals | NOAA] * [https://polymerdatabase.com/polymers/polypropyleneglycol.html Poly(propylene glycol) (polymerdatabase.com)] * [http://www.ampolymer.com/SDS/PolypropyleneGlycolSDS.html Polypropylene Glycol '''Safety Data Sheet''']

Category:Polyethers