Surfactants PDF

Surfactants • The substances that drastically lower the surface tension of water even at low concentrations. • Structure of surfactants • The Amphiphilicity is the basic characters of surfactants • They have both polar and nonpolar moieties. • Hydrophilic group, hydrophobic / lipophilic group. 100...

Surfactants • The substances that drastically lower the surface tension of water even at low concentrations. • Structure of surfactants • The Amphiphilicity is the basic characters of surfactants • They have both polar and nonpolar moieties. • Hydrophilic group, hydrophobic / lipophilic group. 100 Hydrophilic group -COOH, carboxyl -OSO3H, sulphate -SO3H, sulphonic acid -NR4+, ammonium -CH2- CH2-O-, poly-ethylene oxide etc. Hydrophobic group (CH2)n (CF2)n (SiR2-O-)n (-CH2-CH2 -CH2-O-)n 101 • Surfactants, or surface-active agents, or tensides • They form a large group of organic substances that have the ability to modify the interface between two immiscible phases. • The most commonly cited example is a surfactant's ability to lower the interfacial tension between air and an aqueous surfactant solution. • This phenomenon is quite specific and should not be confused with the concept of spreading oil on "troubled waters" or the phenomenon of Newton’s rings in which an additional insoluble phase is added to the system 102 • Cleansers are designed to remove dirt, sweat, sebum, and oils from the skin. • This is achieved through the use of surfactants. • Surfactants are used widely in cosmetic and toiletries formulations for their detergency, foaming, conditioning, solubilization and emulsification properties. • The selection of a surfactant for a cosmetics should take into account the functions to be fulfilled (detergency , emulsification ). 103 • They contain polar (hydrophilic) and non- polar (hydrophobic) regions in the same molecule • The non-polar is usually a long chain hydrocarbon. • The polar portion may carry: • A negative charge= anionic. • A positive charge= cationic. • A positive and negative _ charge = amphoteric. • No charge = nonionic. 104 • The hydrophilic and hydrophobic parts of the molecules must be of comparable “strength ‘ • If the strength of either part overwhelms the other, the substance will have little or no surfactant property . • e.g. ethanol is strongly hydrophilic that it is completely water soluble . • e.g. stearic acid is too hydrophobic which makes it insoluble in water . Stearic acid 105 The Cleansing action of a detergent Cleansing process: 1. Wetting: the detergent reduces the surface tension of water so it is able to spread over and wet the greasy surface 2. Emulsification : the detergent molecules embed their hydrophobic/lipophilic “tail” in the grease and gradually rise it off the surface 3. Rinsing : rinsing with clean water washes away the emulsified grease and loosened dirt to leave the surface clean 106 • The emulsification of the grease is helped by: A. Warm water to melt the grease and help it form into droplets. B. Certain amount of agitation to move away the droplets of emulsified grease and bring fresh detergent to the surface to emulsify the next layer of grease 107 Classification of surfactant (1) Classification by structure anionic ionic cationic amphoteric ester ether nonionic amine amide mixed nonionic-cationic nonionic-anionic 108 Surfactant classes and Examples Surfactant class Examples Anionic Sulfates , phosphates , carboxylates Cationic Quaternary ammonium salts Amphoteric Amino propionates , glycinates Nonionic Ethoxylates 109 Anionic Surfactants • In solution, the head is negatively charged. This is the most widely used type of surfactant for laundering, dishwashing liquids and shampoos because of its excellent cleaning properties. An examples are: 1. Sodium dodecyl sulfate (SDS): Or Sodium lauryl sulfate (SLS) (C12) A detergent 2. Sodium stearate (c18): A soap 3. Sodium c12-15 pareth-15-sulfonate A detergent 110 • Soap: is made by reacting together, animal and vegetable fats and oils with an alkali (sodium hydroxide for hard soap and potassium hydroxide for soft soap) • Soapless detergents and emulsifiers. e.g. Sodium lauryl sulphate 111 Cationic Surfactants • In solution, the head is positively charged (based on quaternary ammonium cations) • E.g.:hexadecyltrimethylammonium bromide is a quaternary ammonium surfactant. 112 Cationic surfactant • Quaternary ammonium compounds • Not good cleansers or emulsifier and they do not foam well • valuable as: - Conditioner for hair. - have a bactericidal action (cetrimide is used in antiseptic/disinfectant products such as savlon 113 Zwitterionic (amphoteric) Surfactant • These surfactants are very mild, making them particularly suited for use in personal care and household cleaning products. • They can be: • anionic (negatively charged) • cationic (positively charged) or • non-ionic (no charge) in solution, depending on the acidity or pH of the water. 114 • An example of an amphoteric/zwitterionic • surfactant is alkyl betaine: • Cocamidopropyl betaine: • Betaines are used in baby shampoo and also used to build lather and viscosity in lauryl sulfate based shampoos. 115 Nonionic surfactants • They do not ionize in solution: • • • • There is no alkaline harshness on the skin Unaffected by hard water There are no incompatibility problems with other ingredients Can be tailored to specific applications (e.g. detergency, wetting agent,..etc • Examples: • • • • Alkylpolyoxyethylenes Spans® (Sorbitan fatty acid esters) Tweens® (Polyoxyethylene sorbitan fatty acid esters) Pluronic® (Poloxamer) 116 Span® • Spans® (sorbitan esters) is synthetic non-ionic surfactant • Spans® (sorbitan esters) are lipophilic surfactants that tend to form w/o 117 emulsions Tween® • • Tweens® (polysorbates) is synthetic non-ionic surfactant Tweens® (polysorbates) are hydrophilic surfactants that tend to form o/w emulsions 118 Poloxamer (Pluronics®, Synperonics®, and Kolliphor®) • Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)) • Commonly named with the letter P (for poloxamer) followed by three digits: • the first two digits multiplied by 100 give the approximate molecular mass of the polyoxypropylene core, and the last digit multiplied by 10 gives the percentage polyoxyethylene content. • e.g. P407 = poloxamer with a polyoxypropylene molecular mass of 4000 g/mol and a 70% polyoxyethylene content. 119 Micelle Formation A. Surfactants will adsorb at the interface between the water and oil phases. B. As we add more surfactant to the system, they will occupy more and more space at the interface. C. At a certain concentration, the surface will be saturated with surfactant molecules, and the addition of more surfactant will cause them to form aggregates known as micelles. The concentration at which this happens is called the critical micelle concentration (CMC) • Any further increase in the total concentration of the surfactant will result in an increased number of micelles. 120 ▪ There is a wide range of relative strength of the hydrophilic and hydrophobic/lipophilic parts. This makes each surfactant suitable for a particular purpose. Those in which the hydrophobic/lipophilic part is dominant tend to form water in oil emulsions. Those in which the hydrophilic part dominates form oil in water emulsion or act as detergent, cleansers or as solubilizes *HLB (hydrophile-Iipophile balance) values 121 HLB (Hydrophile-Lipophile balance) values • There is a wide range of relative strength of the hydrophilic and hydrophobic/lipophilic parts, this makes each surfactant suitable for a particular purpose. • Those in which the hydrophobic/lipophilic part is dominant tend to form water in oil emulsions. • Those in which the hydrophilic part dominates form oil in water emulsion or act as detergent, cleansers or as solubilizes 122 HLB (Hydrophile-Lipophile balance) values More hydrophilic HLB scale showing classification of surfactant function. 123 Functions of Surfactants • The most commonly desired properties for surfactants in cosmetic formulations include: • • • • • • Cleaning Wetting Emulsification Solubilization Dispersion Foaming • Some additional functions include: • Penetration Enhancement • Antimicrobial Activity 124 Chemistry of Surfactants •The selection of a surfactant for use in a cosmetic product is complicated and depends on the product's function. • Six major functions have already been identified 125 Anionic Surfactants • In aqueous solution, anionic surfactant molecules carry negative charges if the composition pH is not too low (slightly acidic, neutral, or alkaline). • The ionized moiety can be a carboxylate, sulfate, sulfonate, or phosphate 126 Anionic Carboxylates • Surfactants belonging to this class generally derive from oleochemistry. • Carboxylate salts (or soaps) are directly produced by the alkaline hydrolysis (or saponification) of animal and vegetable glycerides and result from the neutralization of fatty acids. • Saturated sodium soaps are extremely soluble in water up to C8 • Those with chain lengths approaching C18 become less soluble, and they are insoluble above C20. • Because of their good foaming properties and substantivity on the hair, ester carboxylates are especially suitable in shampoos; in combination with alcohol ethoxy sulfates (AEOS), they provide reduced skin irritation. • Short-chain lactylates (i.e., issued from lactyllactic acid) are important on the skin and show humectant properties. 127 Anionic Alkyl sulfates. • They are generally good foamers, more especially in hard water • Alkyl sulfates are used in cosmetics and personal care areas [e.g., diethanolamine (DEA) lauryl sulfate in shampoos; they are associated with other surfactants and improve foaming characteristics of detergent systems. 128 Cationic Surfactants • Their major interest in cosmetic industry is in hair care; they are used as hair conditioners and antistatic agents. • Cationics are also found in the personal care area as emulsifiers in some cosmetic preparations and as bactericidal agents. 129 Quaternary Ammonium Compounds • They show poor detergency, wetting, and emulsifying capacities. • Note: It is worth to note that, in cosmetic applications, quaternaries may cause ocular and local irritation • Not compatible with anionics because of the formation of water-insoluble complexes • The major use: a) The ability to adsorb on natural or synthetic substrates and fibers. b) Softening agents in rinse fabric softeners. c) Germicides and disinfectants (e.g., dodecyl dimethyl ammonium chloride and benzalkonium chloride). 130 Alkyl betaines • Betaines are good foaming, wetting, and emulsifying surfactants, especially in the presence of anionics. • Betaines have low eye irritation and skin irritation; moreover, the presence of betaines is known to decrease the irritation effect of anionics 131 Amphoteric Surfactants • Amphoteric surfactants are generally used as secondary tensioactives for their foam stabilizing effect, their thickening capacity, and their skin irritation reduction capacity on alkyl sulfates and alkyl ethoxy sulfates. • Example: coco amphocarboxy glycinate used in personal products, in baby shampoos because they reduce eye irritation. • Other applications are fabric softeners, industrial cleaners, and car cleaners. 132 Nonionic Surfactants • Nonionic surfactants do not dissociate into ions in aqueous medium. • They generally deliver a weak to moderate foam • They have good skin and eye compatibility • They have anti-irritant potential when they are combined with anionics in appropriate concentration ratio. • Therefore numerous products for sensitive skin, babies, or the face incorporate nonionics as major surfactant 133 Safe Use of Surfactants • Very little effort has been made to assess potentially damaging impurities in commercial amphiphiles • Nonionics are commonly considered to be the least damaging to human skin. • Anionic sulfates and soaps can provoke serious skin responses when examined via closed patch tests. In normal use, exposure to cleansing amphiphiles is relatively short and causes very little objectively visible damage. A subjective complaints about skin tightness, a phenomenon that is not fully explained. • Cationics cause to proteinaceous tissue and are not readily removed by rinsing. Their retention by the skin may play a role in their germicidal activity 134 Cosmetics Sun Preparation 1st Semester 2022/2023 135 Sunscreen • The purpose of sunscreen preparations is to prevent or minimize the harmful effects on skin of solar/UV radiation. • As such, they are considered to be drug products by the Food and Drug Administration (FDA). • In contrast, suntan preparations are cosmetic products because they are intended to enhance skin color. 136 Sunscreen Agents • The FDA defines sunscreen active agents as "An ingredient listed in Sec. 352.10 that absorbs, reflects, or scatters radiation in the ultraviolet range at wavelengths of 290 to 400 nanometers." 137 Exposure to sun Helpful The first source of energy Harmful Causes Sunburns Initial for growth Makes Our Skin Wrinkle Helps synthesizing Vitamin D Causes Skin Cancer Light source Causes Eye Damage 138 • The sun generates radiation called Ultraviolet (UV) radiation. • UV radiation cannot be seen or felt. • UV radiation causes changes to skin color, damage to eyes, and other bad health effects. 139 Ultraviolet Index or UV Index • The ultraviolet index or UV Index is an international standard measurement of the strength of sunburn-producing ultraviolet (UV) radiation at a particular place and time. 140 UV Index • • The UV Index informs the public of the level of UV exposure expected on a given day. It is reported as a prediction of the UV level at noon. When the UV Index is presented on a daily basis, it represents UV intensity around the Sun's highest point in the day, called solar noon, halfway between sunrise and sunset. This typically occurs between 11:30 and 12:30, or between 12:30 and 13:30 in areas where daylight saving time is being observed. 141 142 Sun Protection Messages 143 Variations in the UV Index 144 UV radiation is not always the same it changes based on… • • • • • • • Time of day Time of year Location Altitude Weather Reflection Ozone Layer 145 • UV light have the greatest impact of all extrinsic factors on how skin ages. • Approximately, 80-85% of the aging symptoms are caused by the rays of the sun . • As we age, the collagen and elastin fibers of the skin naturally weaken. 146 • Weakening of collagen and elastin happens at a much faster rate when the skin is frequently exposed to UV light without proper protection. • UVA rays: (320-400 nm) also known as aging rays, are deep penetrating rays that can even go through a glass window. These rays weaken the collagen and elastin fibers, causing wrinkling of the tissues. • UVB rays: (290-320 nm) also known as burning rays, cause sunburns, tanning of the skin, and the majority of skin cancers. These are shorter rays that stop at the surface of the skin. 147 Sun damage prevention • One way to prevent premature skin aging is to avoid deliberate sun exposure and to use a broad spectrum sunscreen, which is one that filters both UVA and UVB rays and has an SPF (Sun Protection factor) of at least 15, on a daily basis. • Avoid prolonged exposure to the sun during peak hours, when UV exposure is highest. When exposure is highest. This is usually between 10 and 3 pm. 148 • Sunscreen should be applied thirty minutes before sun exposure to allow time for absorption. Many people make the mistake of applying sunscreen after they have been exposed to the heat of sun for thirty minutes or more. • The already inflamed skin is more likely to react to the sunscreen chemicals when the sunscreen is applied after sun exposure. 149 SPF Rating • Sun Protection Factor • SPF is a measure of how much solar energy (UV radiation) is required to produce sunburn on protected skin (i.e., in the presence of sunscreen) relative to the amount of solar energy required to produce sunburn on unprotected skin. As the SPF value increases, sunburn protection increases. • Ratings vary from SPF 1 to 45 or even higher. 150 • There is a popular misconception that SPF relates to time of solar exposure. • For example, many consumers believe that, if they normally get sunburn in one hour, then an SPF 15 sunscreen allows them to stay in the sun 15 hours (i.e., 15 times longer) without getting sunburn. This is not true because SPF is not directly related to time of solar exposure but to amount of solar exposure. Although solar energy amount is related to solar exposure time, there are other factors that impact the amount of solar energy. For example, the intensity of the solar energy impacts the amount. The following exposures may result in the same amount of solar energy: • one hour at 9:00 a.m. • 15 minutes at 1:00 p.m. 151 • The effect of sun light on the skin depends in several factors: • Amount and intense of the solar energy and that relate to the time of the day that your skin will expose to the sun and the geographic location • skin type • amount of sunscreen applied • reapplication frequency 152 Understanding the sunscreen label Broad spectrum • Not all sunscreens are broad spectrum • Broad spectrum sunscreen provides protection from the sun’s ultraviolet (UV) radiation. • Broad spectrum provides protection against both UVA and UVB by providing a chemical barrier that absorbs or reflects UV radiation before it can damage the skin. • Sunscreens that are not broad spectrum or that lack an SPF of at least 15 must carry the warning: "Skin Cancer/Skin Aging Alert: Spending time in the sun increases your risk of skin cancer and early skin aging. This product has been shown only to help prevent sunburn, not skin cancer or early skin aging.” 153 Sun protection factor (SPF) • Sunscreens are made in a wide range of SPFs. • The SPF value indicates the level of sunburn protection provided by the sunscreen product. • All sunscreens are tested to measure the amount of UV radiation exposure it takes to cause sunburn when using a sunscreen compared to how much UV exposure it takes to cause a sunburn when not using a sunscreen. • The product is then labeled with the appropriate SPF value. • Higher SPF values (up to 50) provide greater sunburn protection. • Because SPF values are determined from a test that measures protection against sunburn caused by UVB radiation, SPF values only indicate a sunscreen's UVB protection. 154 • As of June 2011, sunscreens that pass the broad spectrum test can demonstrate that they also provide UVA protection. Therefore, under the label requirements, for sunscreens labeled: "Broad Spectrum SPF [value]", they will indicate protection from both UVA and UVB radiation”. • To get the most protection out of sunscreen, choose one with an SPF of at least 15. • If your skin is fair, you may want a higher SPF of 30 to 50. 155 Ultraviolet Protection Factor (UPF) • Ultraviolet Protection Factor (UPF) indicates how much UV radiation (both UVB and UVA) a fabric allows to reach your skin. For example, a UPF 50 fabric blocks 98 percent of the sun’s rays and allows two percent to penetrate, thus reducing your exposure risk significantly. • A fabric must have a UPF of 30 to qualify for The SKIN CANCER FOUNDATION’S SEAL OF RECOMMENDATION. • A UPF of 30 to 49 offers very good protection, while UPF 50+ rates as excellent. 156 Sun screen versus Sun block • A sun screen is an SPF 2 and higher • A sunblock has a physical sunscreen ingredients with an SPF 12 or higher • Products often contain a mixture of physical and chemical block ingredients • Chemical sunscreen ingredients absorb sunlight thus preventing sun damage of skin. • Physical ingredients act as a natural barrier on skin 157 Skin type according to response to sun exposure 1) Always burns, never tans 2) Burns easily, tans minimally 3) Sometimes burns. Average tan 4) Burns minimally, tans well 5) Rarely burns, tans easily 6) Dark brown or black skin 158 Amount of sunscreen applied • Sun protection products are often labelled with instructions such as “Apply freely”. The recommended amount to be applied is based on mg/cm2 body surface area. • This can be more easily thought as a “golf ball” size amount of product per body, or at least six tea spoonful. 159 • Sunscreen products in the United States are regulated by the FDA as over-the-counter (OTC) drugs. In Australia, they are therapeutic agents. • The main component of sunscreen acts as UV filters or simply filters, acting as a barrier against light penetrating skin by: 1. Either absorb energy in the UV range-in this category we find the organic sunscreens, sometimes falsely referred to as the "chemical" sunscreens. In fact, of course, all materials are "chemical" in nature. 2. Materials that block, scatter, and may absorb energy in the UV range—titanium dioxide and zinc oxide belong to this group. Titanium dioxide reflects and scatters practically all radiation in the UV and visible range (290-777 nm), thereby preventing or minimizing both sunburn and suntan. • There are physical and chemical blockers 160 161 UVB Filters: They may also be classified by their absorption spectrum. 1. 4-Aminobenzoic acid (PABA) and Its Derivatives 2. Cinnamates 3. Salicylates 4. Camphor Derivatives 5. Octocrylene 6. Triazones 162 UVA filters They may also be classified by their absorption spectrum 1. 2. 3. 4. Benzophenones Menthyl Anthanilate Butylmethoxydibenzoylmethane Tetraphthalydine Dicamphor Sulfonic Acid 163 They may also be classified by their absorption spectrum. • Original sunblocks were opaque formulations reflecting or scattering UVR. • Color cosmetics containing a variety of inorganic pigments function in this fashion. • TiO2 and ZnO are chemically inert and protect through the full spectrum of UVR. • They offer significant advantages. Poor cosmetic acceptance limited the widespread use of these two ingredients until microsized forms became available. By decreasing particle size of these materials to a microsize or ultrafine grade, it is less visible on the skin surface. 164 After-Sun Products • Sunlight is highly energetic. • Upon interaction with the skin, sunlight can be reflected, scattered, or absorbed. • To initiate a physical or chemical process, light needs to be absorbed by an atom or molecule. • Human skin is an abundant source of numerous chromophores with strong absorption, particularly in the UVB, UVA, and blue visible region, e.g., porphyrin, bilirubin 2, and pheomelanin 165