Polydimethylsiloxane

Last updated
Polydimethylsiloxane
PmdsStructure.png
Silicone-3D-vdW.png
Names
IUPAC name
poly(dimethylsiloxane)
Other names
  • PDMS
  • dimethicone
  • dimethylpolysiloxane
  • E900
Identifiers
3D model (JSmol)
ChemSpider
  • None
ECHA InfoCard 100.126.442 OOjs UI icon edit-ltr-progressive.svg
E number E900 (glazing agents, ...)
UNII
  • n = 12:C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C
Properties
CH3[Si(CH3)2O]nSi(CH3)3
Density 0.965 g/cm3
Melting point N/A, vitrifies
Boiling point N/A, vitrifies
Pharmacology
P03AX05 ( WHO )
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, is a silicone polymer with a wide variety of uses, from cosmetics to industrial lubrication and passive daytime radiative cooling. [1] [2] [3]

Contents

It is particularly known for its unusual rheological (or flow) properties. PDMS is optically clear and, in general, inert, non-toxic, and non-flammable. It is one of several types of silicone oil (polymerized siloxane). Its applications range from contact lenses and medical devices to elastomers; it is also present in shampoos (as it makes hair shiny and slippery), food (antifoaming agent), caulk, lubricants and heat-resistant tiles.

Structure

The chemical formula of PDMS is CH3[Si(CH3)2O]nSi(CH3)3, where n is the number of repeating monomer [Si(CH3)2O] units. [4] Industrial synthesis can begin from dimethyldichlorosilane and water by the following net reaction:

n Si(CH3)2Cl2 + (n+1) H2O → HO[Si(CH3)2O]nH + 2n HCl

The polymerization reaction evolves hydrochloric acid. For medical and domestic applications, a process was developed in which the chlorine atoms in the silane precursor were replaced with acetate groups. In this case, the polymerization produces acetic acid, which is less chemically aggressive than HCl. As a side-effect, the curing process is also much slower in this case. The acetate is used in consumer applications, such as silicone caulk and adhesives.

Branching and capping

Hydrolysis of Si(CH3)2Cl2 generates a polymer that is terminated with silanol groups (−Si(CH3)2OH). These reactive centers are typically "capped" by reaction with trimethylsilyl chloride:

2 Si(CH3)3Cl + [Si(CH3)2O]n−2[Si(CH3)2OH]2 → [Si(CH3)2O]n−2[Si(CH3)2OSi(CH3)3]2 + 2 HCl

Silane precursors with more acid-forming groups and fewer methyl groups, such as methyltrichlorosilane, can be used to introduce branches or cross-links in the polymer chain. Under ideal conditions, each molecule of such a compound becomes a branch point. This can be used to produce hard silicone resins. In a similar manner, precursors with three methyl groups can be used to limit molecular weight, since each such molecule has only one reactive site and so forms the end of a siloxane chain.

Well-defined PDMS with a low polydispersity index and high homogeneity is produced by controlled anionic ring-opening polymerization of hexamethylcyclotrisiloxane. Using this methodology it is possible to synthesize linear block copolymers, heteroarm star-shaped block copolymers and many other macromolecular architectures.

The polymer is manufactured in multiple viscosities, from a thin pourable liquid (when n is very low), to a thick rubbery semi-solid (when n is very high). PDMS molecules have quite flexible polymer backbones (or chains) due to their siloxane linkages, which are analogous to the ether linkages used to impart rubberiness to polyurethanes. Such flexible chains become loosely entangled when molecular weight is high, which results in PDMS' unusually high level of viscoelasticity.

Mechanical properties

PDMS is viscoelastic, meaning that at long flow times (or high temperatures), it acts like a viscous liquid, similar to honey. However, at short flow times (or low temperatures), it acts like an elastic solid, similar to rubber. Viscoelasticity is a form of nonlinear elasticity that is common amongst noncrystalline polymers. [5] The loading and unloading of a stress-strain curve for PDMS do not coincide; rather, the amount of stress will vary based on the degree of strain, and the general rule is that increasing strain will result in greater stiffness. When the load itself is removed, the strain is slowly recovered (rather than instantaneously). This time-dependent elastic deformation results from the long-chains of the polymer. But the process that is described above is only relevant when cross-linking is present; when it is not, the polymer PDMS cannot shift back to the original state even when the load is removed, resulting in a permanent deformation. However, permanent deformation is rarely seen in PDMS, since it is almost always cured with a cross-linking agent.

If some PDMS is left on a surface overnight (long flow time), it will flow to cover the surface and mold to any surface imperfections. However, if the same PDMS is poured into a spherical mold and allowed to cure (short flow time), it will bounce like a rubber ball. [4] The mechanical properties of PDMS enable this polymer to conform to a diverse variety of surfaces. Since these properties are affected by a variety of factors, this unique polymer is relatively easy to tune. [6] This enables PDMS to become a good substrate that can easily be integrated into a variety of microfluidic and microelectromechanical systems. [7] [8] Specifically, the determination of mechanical properties can be decided before PDMS is cured; the uncured version allows the user to capitalize on myriad opportunities for achieving a desirable elastomer. Generally, the cross-linked cured version of PDMS resembles rubber in a solidified form. It is widely known to be easily stretched, bent, compressed in all directions. [9] Depending on the application and field, the user is able to tune the properties based on what is demanded.

Fabric embedded within PDMS. This technique enables a user to retain a thin layer of PDMS as a substrate while achieving a higher stiffness through the insertion of reinforcement. FabricwithinPDMS.jpg
Fabric embedded within PDMS. This technique enables a user to retain a thin layer of PDMS as a substrate while achieving a higher stiffness through the insertion of reinforcement.
Linear relationship in Sylgard 184 PDMS between curing temperature and Young's modulus PaperYoungTemperature.png
Linear relationship in Sylgard 184 PDMS between curing temperature and Young's modulus

Overall PDMS has a low elastic modulus which enables it to be easily deformed and results in the behavior of a rubber. [10] [11] [12] Viscoelastic properties of PDMS can be more precisely measured using dynamic mechanical analysis. This method requires determination of the material's flow characteristics over a wide range of temperatures, flow rates, and deformations. Because of PDMS's chemical stability, it is often used as a calibration fluid for this type of experiment.

The shear modulus of PDMS varies with preparation conditions, and consequently dramatically varies in the range of 100 kPa to 3 MPa. The loss tangent is very low (tan δ ≪ 0.001). [12]

Chemical compatibility

PDMS is hydrophobic. [8] Plasma oxidation can be used to alter the surface chemistry, adding silanol (SiOH) groups to the surface. Atmospheric air plasma and argon plasma will work for this application. This treatment renders the PDMS surface hydrophilic, allowing water to wet it. The oxidized surface can be further functionalized by reaction with trichlorosilanes. After a certain amount of time, recovery of the surface's hydrophobicity is inevitable, regardless of whether the surrounding medium is vacuum, air, or water; the oxidized surface is stable in air for about 30 minutes. [13] Alternatively, for applications where long-term hydrophilicity is a requirement, techniques such as hydrophilic polymer grafting, surface nanostructuring, and dynamic surface modification with embedded surfactants can be of use. [14]

Solid PDMS samples (whether surface-oxidized or not) will not allow aqueous solvents to infiltrate and swell the material. Thus PDMS structures can be used in combination with water and alcohol solvents without material deformation. However most organic solvents will diffuse into the material and cause it to swell. [8] Despite this, some organic solvents lead to sufficiently small swelling that they can be used with PDMS, for instance within the channels of PDMS microfluidic devices. The swelling ratio is roughly inversely related to the solubility parameter of the solvent. Diisopropylamine swells PDMS to the greatest extent; solvents such as chloroform, ether, and THF swell the material to a large extent. Solvents such as acetone, 1-propanol, and pyridine swell the material to a small extent. Alcohols and polar solvents such as methanol, glycerol and water do not swell the material appreciably. [15]

Applications

Surfactants and antifoaming agents

PDMS derivatives are common surfactants and are a component of defoamers. [16] PDMS, in a modified form, is used as an herbicide penetrant [17] and is a critical ingredient in water-repelling coatings, such as Rain-X . [18]

Dimethicone is used in the active silicone fluid in automotive viscous limited slip differentials and couplings.

Daytime radiative cooling

PDMS is a common surface material used in passive daytime radiative cooling as a broadband emitter that is high in solar reflectivity and heat emissivity. Many tested surfaces use PDMS because of its potential scalability as a low-cost polymer. [19] [20] [21] As a daytime radiative cooling surface, PDMS has also been tested to improve solar cell efficiency. [22]

Soft lithography

PDMS is commonly used as a stamp resin in the procedure of soft lithography, making it one of the most common materials used for flow delivery in microfluidics chips. [23] The process of soft lithography consists of creating an elastic stamp, which enables the transfer of patterns of only a few nanometers in size onto glass, silicon or polymer surfaces. With this type of technique, it is possible to produce devices that can be used in the areas of optic telecommunications or biomedical research. The stamp is produced from the normal techniques of photolithography or electron-beam lithography. The resolution depends on the mask used and can reach 6 nm. [24]

The popularity of PDMS in microfluidics area is due to its excellent mechanical properties. Moreover, compared to other materials, it possesses superior optical properties, allowing for minimal background and autofluorescence during fluorescent imaging. [25]

In biomedical (or biological) microelectromechanical systems (bio-MEMS), soft lithography is used extensively for microfluidics in both organic and inorganic contexts. Silicon wafers are used to design channels, and PDMS is then poured over these wafers and left to harden. When removed, even the smallest of details is left imprinted in the PDMS. With this particular PDMS block, hydrophilic surface modification is conducted using plasma etching techniques. Plasma treatment disrupts surface silicon-oxygen bonds, and a plasma-treated glass slide is usually placed on the activated side of the PDMS (the plasma-treated, now hydrophilic side with imprints). Once activation wears off and bonds begin to reform, silicon-oxygen bonds are formed between the surface atoms of the glass and the surface atoms of the PDMS, and the slide becomes permanently sealed to the PDMS, thus creating a waterproof channel. With these devices, researchers can utilize various surface chemistry techniques for different functions creating unique lab-on-a-chip devices for rapid parallel testing. [7] PDMS can be cross-linked into networks and is a commonly used system for studying the elasticity of polymer networks.[ citation needed ] PDMS can be directly patterned by surface-charge lithography. [26]

PDMS is being used in the making of synthetic gecko adhesion dry adhesive materials, to date only in laboratory test quantities. [27]

Some flexible electronics researchers use PDMS because of its low cost, easy fabrication, flexibility, and optical transparency. [28] Yet, for fluorescence imaging at different wavelengths, PDMS shows least autofluorescence and is comparable to BoroFloat glass. [29]

Stereo lithography

In stereo lithography (SLA) 3D printing, light is projected onto photocuring resin to selectively cure it. Some types of SLA printer are cured from the bottom of the tank of resin and therefore require the growing model to be peeled away from the base in order for each printed layer to be supplied with a fresh film of uncured resin. A PDMS layer at the bottom of the tank assists this process by absorbing oxygen : the presence of oxygen adjacent to the resin prevents it adhering to the PDMS, and the optically clear PDMS permits the projected image to pass through to the resin undistorted.

Medicine and cosmetics

Activated dimethicone, a mixture of polydimethylsiloxanes and silicon dioxide (sometimes called simethicone), is often used in over-the-counter drugs as an antifoaming agent and carminative. [30] [31] PDMS also works as a moisturizer that is lighter and more breathable than typical oils.

Silicone breast implants are made out of a PDMS elastomer shell, to which fumed amorphous silica is added, encasing PDMS gel or saline solution. [32] The use of PDMS in the manufacture of contact lenses was patented (later abandoned). [33]

Skin

PDMS is used variously in the cosmetic and consumer product industry as well. For example, dimethicone is used widely in skin-moisturizing lotions where it is listed as an active ingredient whose purpose is "skin protection." Some cosmetic formulations use dimethicone and related siloxane polymers in concentrations of use up to 15%. The Cosmetic Ingredient Review's (CIR) Expert Panel, has concluded that dimethicone and related polymers are "safe as used in cosmetic formulations." [34]

Hair

PDMS compounds such as amodimethicone, are effective conditioners when formulated to consist of small particles and be soluble in water or alcohol/act as surfactants [35] [36] (especially for damaged hair [37] ), and are even more conditioning to the hair than common dimethicone and/or dimethicone copolyols. [38]

Contact lenses

A proposed use of PDMS is contact lens cleaning. Its physical properties of low elastic modulus and hydrophobicity have been used to clean micro and nano pollutants from contact lens surfaces more effectively than multipurpose solution and finger rubbing; the researchers involved call the technique PoPPR (polymer on polymer pollution removal) and note that it is highly effective at removing nanoplastic that has adhered to lenses. [39]

As anti-parasitic

PDMS is effective for treating lice in humans. This is thought to be due not to suffocation (or poisoning), but to its blocking water excretion, which causes insects to die from physiological stress either through prolonged immobilisation or disruption of internal organs such as the gut. [40]

Dimethicone is the active ingredient in an anti-flea preparation sprayed on a cat, found to be equally effective to a widely used more toxic pyriproxifen/permethrin spray. The parasite becomes trapped and immobilised in the substance, inhibiting adult flea emergence for over three weeks. [41]

Foods

PDMS is added to many cooking oils (as an anti-foaming agent) to prevent oil splatter during the cooking process. As a result of this, PDMS can be found in trace quantities in many fast food items such as McDonald's Chicken McNuggets, french fries, hash browns, milkshakes and smoothies [42] and Wendy's french fries. [43]

Under European food additive regulations, it is listed as E900 .

Condom lubricant

PDMS is widely used as a condom lubricant. [44] [45]

Domestic and niche uses

Many people are indirectly familiar with PDMS because it is an important component in Silly Putty, to which PDMS imparts its characteristic viscoelastic properties. [46] Another toy PDMS is used in is Kinetic Sand. The rubbery, vinegary-smelling silicone caulks, adhesives, and aquarium sealants are also well-known. PDMS is also used as a component in silicone grease and other silicone based lubricants, as well as in defoaming agents, mold release agents, damping fluids, heat transfer fluids, polishes, cosmetics, hair conditioners and other applications.

It can be used as a sorbent for the analysis of headspace (dissolved gas analysis) of food. [47]

Safety and environmental considerations

According to Ullmann's Encyclopedia of Industrial Chemistry , no "marked harmful effects on organisms in the environment" have been noted for siloxanes. PDMS is nonbiodegradable, but is absorbed in waste water treatment facilities. Its degradation is catalyzed by various clays. [48]

See also

Related Research Articles

<span class="mw-page-title-main">Silicone</span> Family of polymers of the repeating form [R2Si–O–SiR2]

In organosilicon and polymer chemistry, a silicone or polysiloxane is a polymer composed of repeating units of siloxane. They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking utensils, thermal insulation, and electrical insulation. Some common forms include silicone oil, grease, rubber, resin, and caulk.

<span class="mw-page-title-main">Hair conditioner</span> Hair care product

Hair conditioner is a hair care cosmetic product used to improve the feel, texture, appearance and manageability of hair. Its main purpose is to reduce friction between strands of hair to allow smoother brushing or combing, which might otherwise cause damage to the scalp. Various other benefits are often advertised, such as hair repair, strengthening, or a reduction in split ends.

A fabric softener or fabric conditioner is a conditioner that is applied to laundry after it has been washed in a washing machine. A similar, more dilute preparation meant to be applied to dry fabric is known as a wrinkle releaser.

<span class="mw-page-title-main">Siloxane</span> Organic functional group (Si–O–Si)

In organosilicon chemistry, a siloxane is an organic compound containing a functional group of two silicon atoms bound to an oxygen atom: Si−O−Si. The parent siloxanes include the oligomeric and polymeric hydrides with the formulae H[OSiH2]nOH and [OSiH2]n. Siloxanes also include branched compounds, the defining feature of which is that each pair of silicon centres is separated by one oxygen atom. The siloxane functional group forms the backbone of silicones [−R2Si−O−SiR2−]n, the premier example of which is polydimethylsiloxane (PDMS). The functional group R3SiO− is called siloxy. Siloxanes are manmade and have many commercial and industrial applications because of the compounds’ hydrophobicity, low thermal conductivity, and high flexibility.

In inorganic chemistry, chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.

<span class="mw-page-title-main">Silicone rubber</span> Elastomer

Silicone rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations. Silicone rubbers are often one- or two-part polymers, and may contain fillers to improve properties or reduce cost. Silicone rubber is generally non-reactive, stable, and resistant to extreme environments and temperatures from −55 to 300 °C while still maintaining its useful properties. Due to these properties and its ease of manufacturing and shaping, silicone rubber can be found in a wide variety of products, including voltage line insulators; automotive applications; cooking, baking, and food storage products; apparel such as undergarments, sportswear, and footwear; electronics; medical devices and implants; and in home repair and hardware, in products such as silicone sealants.

<span class="mw-page-title-main">Plasma cleaning</span>

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<span class="mw-page-title-main">Decamethylcyclopentasiloxane</span> Chemical compound

Decamethylcyclopentasiloxane, also known as D5 and D5, is an organosilicon compound with the formula [(CH3)2SiO]5. It is a colorless and odorless liquid that is slightly volatile.

<span class="mw-page-title-main">Hexamethyldisiloxane</span> Chemical compound

Hexamethyldisiloxane (HMDSO or MM) is an organosilicon compound with the formula O[Si(CH3)3]2. This volatile colourless liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chloride. The molecule is the protypical disiloxane and resembles a subunit of polydimethylsiloxane.

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<span class="mw-page-title-main">PDMS stamp</span> Patterned silicone piece]

PDMS stamps are pieces of polydimethylsiloxane (PDMS), a silicone, that have been patterned usually against a master mold to form a relief pattern used in soft lithography. This PDMS stamp can be used in either its current form as a relief surface for techniques such as microcontact printing or can also be attached to an external source by tubing so that liquid may be passed through channels on its surface. In this second case it will often be laminated to a surface so that chemistry can be performed on that surface producing a pattern of the PDMS stamp on to the surface. Alternatively a PDMS stamp can be laminated to a second piece of PDMS to form a contained device. It is possible to pattern PDMS with nanometre resolution.

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References

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  27. ↑ "Inspired by Gecko Feet, UMass Amherst Scientists Invent Super-Adhesive Material" (Press release). UMass. 16 Feb 2012. Archived from the original on 2012-02-23.
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  30. ↑ Prentice, William E. & Voight, Michael L. (2001). Techniques in musculoskeletal rehabilitation. McGraw-Hill Professional. p. 369. ISBN   978-0-07-135498-1.
  31. ↑ Hunt, Richard H.; Tytgat, G. N. J. & Pharma, Axcan (1998). Helicobacter Pylori: Basic Mechanisms to Clinical Cure 1998. Springer. p. 447. ISBN   978-0-7923-8739-8.
  32. ↑ Evaluation of sustained release of antisense oligonucleotide from poly DL (lactide-co-glycolide) microspheres targeting fibrotic growth factors CTGF and TGF-β1 (PDF).
  33. ↑ USAbandoned 20050288196,Gerald Horn,"Silicone polymer contact lens compositions and methods of use",published 2005-12-29, assigned to Ocularis Pharma Inc.
  34. ↑ Nair, B; Cosmetic Ingredients Review Expert Panel (2003). "Final Report on the Safety Assessment of Stearoxy Dimethicone, Dimethicone, Methicone, Amino Bispropyl Dimethicone, Aminopropyl Dimethicone, Amodimethicone, Amodimethicone Hydroxystearate, Behenoxy Dimethicone, C24-28 Alkyl Methicone, C30-45 Alkyl Methicone, C30-45 Alkyl Dimethicone, Cetearyl Methicone, Cetyl Dimethicone, Dimethoxysilyl Ethylenediaminopropyl Dimethicone, Hexyl Methicone, Hydroxypropyldimethicone, Stearamidopropyl Dimethicone, Stearyl Dimethicone, Stearyl Methicone, and Vinyldimethicone". International Journal of Toxicology. 22 (2 Suppl): 11–35. doi:10.1177/1091581803022S204. PMID   14555417.
  35. ↑ Schueller, Randy; Romanowski, Perry (1999). Conditioning Agents for Hair and Skin. CRC Press. p. 273. ISBN   978-0-8247-1921-0. Amodimethicone is recognized for its extremely robust conditioning and for its ability to form clear products when used in high-surfactant shampoos. Amodimethicone is a useful ingredient in conditioners, gels, mousses, and permanents, but its use in shampoos has proved troublesome due to interactions between the cationic and the anionic surfactants, which can result in compatibility problems. However, the amodimethicone emulsion can be made compatible in high-surfactant-level shampoos
  36. ↑ Goddard, E. Desmond; Gruber, James V. (1999). Principles of Polymer Science and Technology in Cosmetics and Personal Care. CRC Press. p. 299. ISBN   978-0-8247-1923-4. Amodimethicone is typically an emulsion-polymerized polymer; however, utilizing linear processing technology amodimethicone fluids may be prepared as neat fluids, and then emulsified by a mechanical process as desired. The most widely utilized amodimethicone emulsions contain as the surfactant pair either (1) tallowtrimonium chloride (and) nonoxy- nol-10, or (2) cetrimonium chloride (and) trideceth-10 or -12. These "uncapped" amino- functional silicone compounds may be characterized by a linear or branched structure. In either case, amodimethicone polymers will undergo a condensation cure reaction during drying to form a somewhat durable elastomeric film on the hair, providing wet- and dry- combing benefits, lowering triboelectric charging effects, and increasing softness of the dry hair. They are excellent conditioning agents, often found in conditioners, mousses, setting lotions, and less frequently in 2-in-1 shampoos
  37. ↑ Iwata, Hiroshi (2012). Formulas, Ingredients and Production of Cosmetics: Technology of Skin- and Hair-Care Products in Japan. Springer Science & Business Media. p. 144. ISBN   978-4-431-54060-1. Amodimethicone is the most widely used amino-modified silicone. It has an aminopropyl group attached to the methyl group of Dimethicone. Amodimethicone of various degrees of amino modification are available as well as those that have POP, POE, or an alkyl group attached. Amino-modified silicones are cationic and affinitive to hair keratin. They are particularly highly affinitive to damaged hair, which is anionic due to the presence of cysteic acid
  38. ↑ Barel, André O.; Paye, Marc; Maibach, Howard I. (2014). Handbook of Cosmetic Science and Technology, Fourth Edition. CRC Press. p. 567. ISBN   978-1-84214-564-7. ...and amodimethicone, which is an amino-substituted silicone and silicone quats, which contain permanently quaternized ammonium groups. In general, amodimethicones and silicone quats condition better than dimethicones, which condition better than dimethicone copolyols
  39. ↑ Burgener, Katherine; Bhamla, M. Saad (2020-05-19). "A polymer-based technique to remove pollutants from soft contact lenses". Contact Lens and Anterior Eye. 44 (3): 101335. arXiv: 2005.08732 . doi:10.1016/j.clae.2020.05.004. ISSN   1367-0484. PMID   32444249. S2CID   218673928.
  40. ↑ Burgess, Ian F. (2009). "The mode of action of dimeticone 4% lotion against head lice, Pediculus capitis". BMC Pharmacology. 9: 3. doi: 10.1186/1471-2210-9-3 . PMC   2652450 . PMID   19232080.
  41. ↑ Jones, Ian M.; Brunton, Elizabeth R.; Burgess, Ian F. (2014). "0.4% Dimeticone spray, a novel physically acting household treatment for control of cat fleas". Veterinary Parasitology. 199 (1–2): 99–106. doi:10.1016/j.vetpar.2013.09.031. ISSN   0304-4017. PMID   24169258.
  42. ↑ "McDonald's Food Facts: Ingredients" (PDF). McDonald's Restaurants of Canada Limited. 2013-09-08. p. 13.
  43. ↑ "Wendy's: Menu: French Fries - Ingredients". Wendy's International, Inc. Retrieved 2022-11-14.
  44. ↑ Coyle, Tiernan; Anwar, Naveed (2009). "A novel approach to condom lubricant analysis: In-situ analysis of swabs by FT-Raman Spectroscopy and its effects on DNA analysis". Science & Justice. 49 (1): 32–40. doi:10.1016/j.scijus.2008.04.003. PMID   19418926.
  45. ↑ Blackledge, R. D.; Vincenti, M. (1994). "Identification of polydimethylsiloxane lubricant traces from latex condoms in cases of sexual assault". Journal of the Forensic Science Society. 34 (4): 245–256. doi:10.1016/s0015-7368(94)72928-5. PMID   7844517.
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