Silicone surfactants Wetting

Ananthapadmanabhan KP, Goddard ED, Chandar P (1990) A study of the solution, interfacial and wetting properties of silicone surfactants. Colloid Surf 44 281-297... 

Many small-molecule silicone surfactants have been made and their properties (especially wetting) characterized [7-11]. The best known small-molecule silicone surfactants are the trisiloxane surfactants based on 1,1,1,3,5,5,5-heptamethyltrisiloxane, shown in Figure 6.19. 

Silicone surfactants are specialty surfactants that are primarily used in applications that demand their unique properties. Most applications are based on some combination of their (a) low surface tension, (b) surface activity in nonaqueous media, (c) wetting or spreading, (d) low friction or tactile properties, (e) ability to deliver silicone in a water-soluble (or dispersible) form, (f) polymeric nature or (g) low toxicity. The major applications will be discussed briefly in following sections. 

Surface treatments are often necessary for aesthetic and performance reasons. This can involve printing or lacquering, using both solvent and non-solvent based inks, which are applied to the surface using rollers, pads, silk screen, inkjet or lasers. Waterborne coatings are environmentally more desirable and silicone surfactants are claimed to give the best performance to improve substrate wetting (456). 

Silicone Surfactants - Hydrolytically Stable Wetting Agents 615... 

AI3-23126 3,5-Dimethyl-1-hexyn-3-ol EINECS 203-500-9 1-Hexyn-3-ol, 3,5-dimethyl- NSC 978 Surfynol Surlynol 61, Surfactant, wetting agent used for paper coatings. Inks, floor polishes, and glass cleaning formulations cleaner In silicon wafer industry, bp = 150° d= 0.859 08 = 1.4340. Air Products Chemicals Inc. 

Of the various surface active chemistries currently available, this paper will mainly concentrate on a class of materials called Silicone Polyethers. This family of copolymers is used to provide multifunctional benefits in water borne systems. The main uses of silicone polyethers in inks and coatings include de-foaming, de-aerating, improved substrate wetting, levelling and enhanced slip properties (1,2). The three most common molecular structures for silicone surfactants are rake type copolymers, ABA copolymers and trisiloxane surfactants. These are illustrated in Figs 1,2 and 3 respectively and the performance of these structures will be described in two types of coatings ... 

Water has a typical surface tension of 72mN/m and, as can be seen fi om the above table, all the surfactants tested reduced the surface tension of the s em, and as a result the aqueous medium wets more efficiently. For the silicone surfactants the best results were achieved with product A, a low molecular weight material. Trisiloxane A gives a very low figure that is only improved upon by the fluorosurfactant. The Critical Micelle Concentration (CMC) is the required level of product to initiate the formation of micelles in the bulk of the liquid. Up to this point the surfactant added to die water migrates to the liquid/air interface to form a film which reduces the surface tension. The low CMC for A shows its high packing efficiency at the intoface, in the much lower level required in comparison to the other products. 

A wetting agent it helps the wetting of the drug and. upon adsorbing on the surface of the particles, improves their stability by electrostatic repulsion, protective action, or both. Additives typically used include surfactants such as polyoxyethylene, sodium dodecyl sulfate, and, more recently, silicone surfactants (88). and polyols (particularly propylene glycol and PEG see Ref. 89). 

Uses Surfactant, wetting agent, flow aid, leveling agent for waterborne coatings, esp. on leather or syn. substrates Features Compat. with most waterborne and some solv. systems effective at low cones. silicone-free... 

Uses Surfactant, wetting agent, lubricant, detackifier, emulsifier, foam stabilizer, humectant, spreading agent, resin plasticizer for personal care prods, (hair fixatives, skin care, shave prods., shampoos), textiles, paints Properties Clear to straw liq. water-sol. below 73 C sol. in aromatic hydrocarbons, castor oil, 95% ethanol, 99% IPA, propylene glycol, octyidimethyl PABA sp.gr. 1.07 dens. 8.82 Ib/gal vise. 250-600 cSt flash pt. (CC) > 150 C surf. tens. 24.5 dynes/cm 100% silicone Use Level 0.5-3.0%... 

Keywords Polymers / Hybrid Organic-Inorganic Polymers / Polymer Network / IPN / Hybrid Polymer Technologies / Contact Lenses / Coatings / Surfactants / Wetting Agents / Silicones / Silicone Polyimides / Siloxane Resins... 

K. D. Klein, W. Knott, G. Koemer, Silicone Surfactants — Development of Hydrolytically Stable Wetting Agents in Organosilicon Chemistry II From Molecules to Materials (Eds. N. Auner, J. Weis), VCH, Weinheim, 1996. 

K. P. Anathapadmanabhan, E. D. Goddard, P. Chandar A Study of the Solution, Interfacial and Wetting Properties of Silicone Surfactants , Colloids and Surfaces 1990, 44, 281-297. 

X-N1586/X-N1587 in combination (formulations IV and VIII). Furthermore, Japanese wet set values [6] can be improved by 5 to 8% with the Dabco BL-53, and experimental silicone surfactants X-N1586 and X-N1587. Wet set values are improved nearly 20% when the two additives are utilised in combination as evidenced by Formulations IV and VIII. Equally important, humid aged compression set, tensile and tear physical properties display a positive improvement trend as compared to the control formulations. 

Tables 1.8 and 1.9 illustrate the physical properties for selected formulations at TPR times of 130 and 150 seconds. Control physical properties were not evaluated at these extended TPR times since the control formulations I and V had visual surface distortions and severe scalloping. The data in Tables 1.8 and 1.9 demonstrate that the TPR window can be extended by using these newly developed additives without negative impact to the physical properties. In fact, the data indicates that several of the physical properties for the experimental formulations exceed the control formulation properties at the 90 second TPR time. For example, airflow measurements are improved when utilising the extended TPR times. Improvements are greater than 10% with the Dabco BL-53 catalyst and experimental silicone surfactant combinations. Additional improvements are also observed with wet set and 50% humid aged compression set values.

Adjuvants are most often nsed with herbicides, but they are also used with selected insecticides and fungicides. The adjuvants conunonly in use include surfactants, oils, solvents, polymers, foams, salts, and photo protectants, as weU as combinations of these components. Adjuvants for herbicides delivered from water dilutions are most commonly nonionic surfactants and crop oil concentrates. Nonionic surfactants are added for wetting of the leaf surfaces, and the crop oil concentrates are added as penetration enhancers. Organosilicone surfactants have been shown to enhance the availability of several pesticides. The silicone surfactants reduce the surface tension below 20 dyne/cm and are often referred to as super wetting surfactants. 

These surfactants can lower the surface tension of water to below 20 mN (most surfactants described above lower the surface tension of water to values above 20 mN m typically in the region of 25-27 mN m ). Fluorocarbon and silicone surfactants are sometimes referred to as superwetters as they cause enhanced wetting and spreading of their aqueous solution. However, they are much more expensive than conventional surfactants and are only applied for specific applications whereby the low surface tension is a desirable property. 

Somewhat curiously, Binks and Dong [73] report a case of partial wetting with 48 mPa s PDMS on solutions of a non-ionic ethoxylated silicone surfactant of quoted [73] formula... 

Even on micellar solutions of this compound, the PDMS oil forms lenses with zero spreading pressure. Similar behavior is seen with submicellar solutions even up to air-water surface tensions of 45 mN m. Since the oil spreads on water, this suggests a possible first-order wetting transition between partial wetting and pseudo-partial wetting at even higher air-water surface tensions. Rather surprisingly then, this means that no penetration of the monolayer of this silicone surfactant by the PDMS must occur. 

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