Propylene Glycol

• CAS: 57-55-6
• Catalog Number: ACM57556-3
• Category: Main Products
• Molecular Weight: 76.09
• Molecular Formula: C3H8O2
• Description: Modified alcohol (1,2-propanediol), metabolized to lactic acid in the body.
• Synonyms: Propyleneglycol manufacturer
• IUPAC Name: Propane-1,2-diol
• SMILES: CC(CO)O
• InChI: InChI=1S/C3H8O2/c1-3(5)2-4/h3-5H,2H2,1H3
• InChI Key: DNIAPMSPPWPWGF-UHFFFAOYSA-N
• Boiling Point: 187 °C(lit.)
• Melting Point: -60 °C(lit.)
• Flash Point: 225 °F
• Density: 1.036 g/mL at 25 °C(lit.)
• Solubility: Soluble in water, ethanol, acetone
• Appearance: Liquid
• Application: All kinds of skin care products, hair care products, color cosmetics, soaps (glycerin soap).
• Storage: 5-30 °C
• Autoignition Temperature: 700 °F (USCG, 1999);700 °F (371 °C);420 °C
• Color/Form: Colorless viscous liquid
• Complexity: 20.9
• Composition: Propylene glycol
• Covalently-Bonded Unit Count: 1
• Decomposition: When heated to decomposition it emits acrid smoke and irritating fumes.
• Defined Atom Stereocenter Count: 0
• EC Number: 200-338-0;200-338-0;613-293-0
• Exact Mass: 76.052429494
• Features And Benefits: Effective humectant and wetting agent preventing water loss in products and in the skinIncreases skin permeability of active ingredients as it penetrates into the outermost skin layersEmollient and lubricant propertiesExcellent solubilizer of other ingredientsIncreases spreading of creams
• Formal Charge: 0
• H-Bond Acceptor: 2
• H-Bond Donor: 2
• Heat of Vaporization: 168.6 cal/g at BP
• Heavy Atom Count: 5
• HS Code: 2905320000
• Hydrogen Bond Acceptor Count: 2
• Hydrogen Bond Donor Count: 2
• ICSC Number: 0321
• LogP: -0.92 (LogP);-0.92;log Kow = -0.92;-0.92;-0.92
• Monoisotopic Mass: 76.052429494
• NSC Number: 69860;35749;35748;35747
• Odor: Practically odorless
• Other Experimental: Specific heat: 0.590 cal/g at 20 °C; hygroscopic;Heat of vaporization = 15.4 kcal/mol at 25 °C; heat of formation = -116.1 kcal/mol at 25 °C (liquid); heat capacity = 45.1 kcal/mol at 20 °C; viscosity = 56.0 cP at 20 °C; surface tension = 36.51 dyne/cm at 25 °C;BP: 88-90 °C at 12 mm Hg; 187-189 °C at 760 mm Hg. Specific optical rotation: -15 deg at 20 °C /l-form/;BP: 95-96 °C at 14 mm Hg; Specific optical rotation: +15 (neat) deg at 20 °C; Density: 1.04 at 25 °C/4/ degC /d-form/;Henry's Law constant = 1.3X10-8 atm-cu m/mol at 25 °C (est);Hydroxyl radical reaction rate constant = 1.2X10-11 cu cm/molec-sec at 25 °C
• Physical State: Viscous liquid
• pKa: 14.49±0.20(Predicted)
• Refractive Index: n20/D 1.432(lit.)
• Rotatable Bond Count: 1
• RTECS Number: TY2000000
• Stability: At cool temperatures, propylene glycol is stable in a well-closed container, but at high temperatures, in the open, it tends to oxidize, giving rise to products such as propionaldehyde, lactic acid, pyruvic acid, and acetic acid. Propylene glycol is chemically stable when mixed with ethanol (95%), glycerin, or water; aqueous solutions may be sterilized by autoclaving.
• Storage Conditions: 5-30 °C
• Topological Polar Surface Area: 40.5 Ų
• Vapor Density: 2.62 (NTP, 1992) (Relative to Air);Relative vapor density (air = 1): 2.6;2.62
• Vapor Pressure: 0.08 mm Hg at 68 °F ; 0.13 mm Hg at 77° F (NTP, 1992);0.13 mmHg;0.13 mm Hg at 25 °C /Extrapolated/;Vapor pressure, Pa at 20 °C: 10.6;0.08 mmHg
• Viscosity: 0.581 cP at 20 °C
• XLogP3: -0.9

Case Study

Evaluating Propylene Glycol as an Antimicrobial Vehicle for Endodontic Disinfection

Nalawade, Triveni Mohan, et al. Journal of International Society of Preventive and Community Dentistry 5.2 (2015): 114-119.

Successful endodontic therapy requires thorough root canal disinfection, particularly in refractory cases where standard irrigation is insufficient. This investigation assessed the in vitro bactericidal activity of propylene glycol (PG) alongside glycerine, PEG 400, PEG 1000, and a PG/PEG 400 combination against key endodontic pathogens: Streptococcus mutans ATCC 25175, S. mutans ATCC 12598, Enterococcus faecalis ATCC 35550, and Escherichia coli ATCC 25922.
Methodology: A broth dilution assay determined the minimum bactericidal concentration (MBC) for each vehicle. PG was evaluated both independently and in combination with PEG 400 to identify its specific antimicrobial contribution.
Key Findings on Propylene Glycol
· PG demonstrated bactericidal activity against three clinically relevant pathogens: S. mutans ATCC 25175 at 50% concentration; E. faecalis ATCC 35550 at 25% concentration; E. coli ATCC 25922 at 50% concentration.
· The combination of PG and PEG 400 did not exhibit any synergistic antimicrobial effect and, in fact, was less effective against S. mutans, E. faecalis, and E. coli than PG utilized alone.

Solubility Study of Carvedilol in Propylene Glycol/Ethanol Mixtures

Vahdati, Sahel, et al. Industrial & Engineering Chemistry Research 52.47 (2013): 16630-16636.

Carvedilol (CVD), a critical Class II drug (low solubility/high permeability) for cardiovascular conditions, faces bioavailability limitations. Developing pediatric liquid formulations or soft gelatin capsules requires non-aqueous solubility enhancement. Propylene glycol (PG) and ethanol are established pharmaceutical cosolvents, but systematic data on their combined efficacy for CVD is essential to replace trial-and-error formulation methods.
Methodology
This study quantified CVD solubility in binary PG/ethanol mixtures at 298.2K-313.2K (25°C-40°C). Thermodynamic properties (ΔH°, ΔS°, ΔG°) were derived via modified van't Hoff and Gibbs equations. Four mathematical models (Jouyban-Acree, its combination with van't Hoff, and two modified versions) correlated solubility data. Enthalpy-entropy compensation analysis elucidated cosolvency mechanisms.
Key Findings
The solubility behavior of CVD in mixtures of (ethanol (1) + PG (2)) exhibits a nonlinear pattern with distinct maxima. Furthermore, the Jouyban-Acree model was utilized to develop a quantitative structure-activity relationship (QSAR) model for predicting drug solubility in these solvent mixtures at various temperatures. It is evident that the solubility process of CVD in (ethanol (1) + PG (2)) is significantly influenced by the composition of the cosolvent. A nonlinear enthalpy-entropy compensation relationship was observed for CVD in this solvent system, as indicated by the plot of ΔH° against ΔG°.

The safety of propylene glycol in cosmetics

Fiume, Monice M., et al.International journal of toxicology 31.5_suppl (2012): 245S-260S.

Propylene glycol is an aliphatic alcohol used in cosmetics as a skin conditioning agent, viscosity reducer, solvent, and fragrance ingredient. Clinical studies have shown no skin sensitization at the concentrations used, although concerns about irritation remain. The expert panel determined that available information supports the safety of tripropylene glycol and all PPGs. The panel concluded that PG, tripropylene glycol, and PPGs 3 are safe for use in cosmetic formulations when formulated to be non-irritating.
Dermal absorption of PG into the outermost layer of the skin was measured using thermal emission attenuated Fourier transform infrared (TED-FTIR) spectroscopy. Propylene glycol was applied to the fingertip of a human participant using PG-soaked cotton wool for 30 minutes. The area was rubbed and allowed to dry for 1 minute. The surface layer of the stratum corneum was probed to a thickness of 0.71 mm. Measurements were taken every 25 minutes over 3 hours, with one measurement taking 15 minutes. The concentration of PG remaining on the surface of the stratum corneum decreased over time.

Propylene glycol studies in dairy cows

Nielsen, Nicolaj Ingemann, and Klaus Lønne Ingvartsen. Animal Feed Science and Technology 115.3-4 (2004): 191-213.

This study describes how propylene glycol (PG) is metabolized in the rumen and liver and how it affects metabolites, hormones, liver composition, feed intake, and milk production. The goal was to evaluate whether PG might prevent excessive fat mobilization and imbalances in carbohydrate and fat metabolism, thereby reducing the risk of ketosis. Generally, PG has no statistically significant effect on milk production, but in early-lactation cows, PG tends to increase milk production and reduce milk fat percentage, while preserving milk protein percentage.
463 g of propylene glycol (PG) was infused intraruminally, and reticulocytes were washed as previously described. The study demonstrated that PG accumulated in plasma and was metabolized at a low rate, although approximately 0.1% of absorbed PG was metabolized to lactate. Under normal rumen conditions, PG is primarily metabolized in the rumen, not the liver. Cows and heifers receiving PG have a significantly higher proportion of propionate in rumen volatile fatty acids (VFA), indicating that PG is extensively metabolized in the rumen.

Custom Q&A

What is the molecular formula of propylene glycol?

The molecular formula of propylene glycol is C3H8O2.

What are some synonyms for propylene glycol?

Some synonyms for propylene glycol are 1,2-propanediol, propane-1,2-diol, and methyl glycol.

How is propylene glycol classified by the Food and Drug Administration (FDA)?

The FDA has classified propylene glycol as an additive that is "generally recognized as safe" for use in food.

What industries use propylene glycol as an antifreeze?

The chemical, food, and pharmaceutical industries use propylene glycol as an antifreeze when leakage might lead to contact with food.

What is the molecular weight of propylene glycol?

The molecular weight of propylene glycol is 76.09 g/mol.

What role can propylene glycol play in pharmaceuticals, cosmetics, and food products?

Propylene glycol can absorb extra water and maintain moisture in certain medicines, cosmetics, or food products.

What is the structure of propylene glycol?

The structure of propylene glycol is CH3CHOHCH2OH.

How is propylene glycol used in fire-fighting training and theatrical productions?

Propylene glycol is used to create artificial smoke or fog used in fire-fighting training and theatrical productions.

Can propylene glycol exist in air in vapor form at room temperature?

Propylene glycol must be heated or briskly shaken to produce a vapor and exist in air in the vapor form.

What is the odor and taste of propylene glycol?

Propylene glycol is practically odorless and tasteless.