Poly acrylic acid PAA ; trade name Carbomer is a synthetic high- molecular weight polymer of acrylic acid. They may be homopolymers of acrylic acid, or crosslinked with an allyl ether of pentaerythritolallyl ether of sucroseor allyl ether of propylene. In a water solution at neutral pHPAA is an anionic polymeri. This makes PAAs polyelectrolyteswith the ability to absorb and retain water and swell to many times their original volume. Dry PAAs are sold as white, fluffy powders that are frequently used as gels in cosmetic and personal care products.
Their role in cosmetics is to suspend solid in liquids, prevent emulsions from separating and control the consistency in flow of cosmetics. Carbomer codes, and P are an indication of molecular weight and the specific components of the polymer. For many applications PAAs are used in form of alkali metal or ammonium salts, e.
In the dry powder form, the positively charged sodium ions are bound to the polyacrylate, however in aqueous solutions the sodium ions can dissociate. Instead of an organized polymer chain, this leads to a swollen gel that can absorb a high amount of water. Polyacrylic acid is a weak anionic polyelectrolyte, whose degree of ionisation is dependent on solution pH.
In its non-ionised form at low pHs, PAA may associate with various non-ionic polymers such as polyethylene oxide, poly-N-vinyl pyrrolidone, polyacrylamide, and some cellulose ethers and form hydrogen-bonded interpolymer complexes  In aqueous solutions PAA can also form polycomplexes with oppositely charged polymers for example, chitosansurfactants, and drug molecules for example, streptomycin. Polyacrylic acid and its derivatives are used in disposable diapers ion exchange resins, adhesives and detergents.
Detergents are often copolymers of acrylic acid that can be used in both zeolites and phosphates in washing powder formulations. They are also popular as thickeningdispersingsuspendingand emulsifying agents in pharmaceuticalscosmeticsand paints. Cross-linked polyacrylic acid has also been used in the processing of household products, including floor cleaners. Acrylic acid is also the main component of Superadsorbent Polymers SAPscross-linked polyacrylates that can absorb and retain more than times of their own weight in liquid.
PAA films can be deposited on orthopaedic implants to protect them from corrosion. Crosslinked hydrogels of AA and gelatin have also been used as medical glue, which has a high bonding strength. For the development of polymeric matrices which allows controlled delivery rate of active substances, the recent investigations aimed towards the clarification of the conformational changes of the polymeric gel during neutralization, light irradiation, and embedment of gold nanoparticles.
Free radical polymerization is still the most common industrial for production of polymers. For the free radical polymerization of acrylic acid, most commonly thermochemical initiators such as potassium persulfate and AIBN are used. The polymerization can take several hours to complete but can be accelerated by drastically increasing the temperature and pressure.
PAA is widely used in dispersants and since the molecular weight has a significant impact on the rheological properties and dispersion capacity, it is crucial to have control over the molecular weight distribution. RAFT polymerization was used to obtain PAA with a defined molecular weight, leading to improved dispersion properties.Carbopol is available in several different grades, which are widely used in manufacture of cosmetics and toiletries, including gels, creams and lotions, detergents, and air fresheners.
Neutralizing agents include triethanolamine TEAsodium hydroxide and potassium hydroxide. Manufacturing methods vary according to the type of product, but can be summarized as follows:. Dispersion is completed in a fraction of the time taken by conventional means, avoiding the risk of overshearing the polymer.
Operation is described below. In certain circumstances Silverson mixers can be used for the neutralization stage, depending on percentage and grade of Carbopol.
The vessel is charged with appropriate base fluid. The mixer is started, and the Carbopol is added. The high speed rotation of the single-piece Ultramix workhead creates a powerful vortex, drawing the powder and liquid down into the workhead where they are rapidly mixed. The materials are then forced through the slots in the side of the workhead and projected back into the body of the mix. Any agglomerates are broken down as they pass through the slots.
The vigorous movement in the vessel created by the Ultramix ensures that in a short mixing cycle all the material passes many times through the workhead, progressively reducing the particle size and exposing an increasing surface area to the surrounding liquid. This rapidly completes hydration. The batch size, grade and percentage of Carbopol, and the product viscosity dependant on pH of solution before neutralization dictate which Silverson mixer is most suitable for individual process requirements.
Have the latest how-to videos, application reports and more delivered straight to your inbox. The Problem Carbopol is generally supplied as a very light, low density powder. It tends to float when added to water, requiring vigorous agitation to be incorporated.
This can cause dusting problems. When added to the water, Carbopol tends to form agglomerates which are not readily dispersed. Some powders have poor flow properties, making controlled powder addition difficult.
While some grades display no significant increase in viscosity until neutralized, others start to thicken immediately, making addition of powder increasingly difficult. Aeration can create a persistent foam which may require chemical additives to disperse. Entrained air is very difficult to remove, clouding clear gels and causing problems where packaging is filled by volume rather than weight.
Potential full yield is difficult to obtain with conventional agitation; many formulations contain unnecessarily high levels of Carbopol to compensate for this. Prolonged exposure to intense high shear can damage the polymer, reducing viscosity. The Solution These problems can be overcome using a Silverson mixer to disperse the Carbopol. Dispersion Dispersion is completed in a fraction of the time taken by conventional means, avoiding the risk of overshearing the polymer. Neutralization In certain circumstances Silverson mixers can be used for the neutralization stage, depending on percentage and grade of Carbopol.
Stage 1 The vessel is charged with appropriate base fluid.
Stage 2 The materials are then forced through the slots in the side of the workhead and projected back into the body of the mix. Stage 3 The vigorous movement in the vessel created by the Ultramix ensures that in a short mixing cycle all the material passes many times through the workhead, progressively reducing the particle size and exposing an increasing surface area to the surrounding liquid.Carbomer is a term used for a series of polymers primarily made from acrylic acid.
Carbomers are white, fluffy powders but are frequently used as gels in cosmetics and personal care products. Carbomers can be found in a wide variety of product types including skin, hair, nail, and makeup products, as well as dentifrices.
Carbomers are thickening agents that help control the viscosity and flow of cosmetic products. They also help distribute and suspend insoluble solids into liquid, and prevent the oil and liquid parts of a solution from separating.
They have the ability to absorb and retain water, and can swell up to times their original volume when dispersed in water. Generally, this class of ingredients is used in gel-like formulations because it forms a colloidal, mucilage-like consistency when mixed in water. This ingredient is contained in a wide range of personal care products such as styling gel, facial moisturizer, sunscreen, shampoo, anti-aging treatment, eye cream, cleanser and scrubs. This ingredient has been assessed as safe to use in cosmetic products.
Home Menu.A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. Edible thickeners are commonly used to thicken saucessoupsand puddings without altering their taste; thickeners are also used in paintsinksexplosivesand cosmetics. Thickeners may also improve the suspension of other ingredients or emulsions which increases the stability of the product.
Thickening agents are often regulated as food additives and as cosmetics and personal hygiene product ingredients. Some thickening agents are gelling agents gellantsforming a geldissolving in the liquid phase as a colloid mixture that forms a weakly cohesive internal structure.
Others act as mechanical thixotropic additives with discrete particles adhering or interlocking to resist strain. Thickening agents can also be used when a medical condition such as dysphagia causes difficulty in swallowing. Thickened liquids play a vital role in reducing risk of aspiration for dysphagia patients. Food thickeners frequently are based on either polysaccharides starchesvegetable gumsand pectinor proteins.
A flavorless powdered starch used for this purpose is a fecula from the Latin faeculadiminutive of faex, "dregs". This category includes starches as arrowrootcornstarchkatakuri starchpotato starchsagowheat flour, almond flour, tapioca and their starch derivatives. Microbial and Vegetable gums used as food thickeners include algininguar gumlocust bean gumand xanthan gum.
Proteins used as food thickeners include collagenegg whitesand gelatin. Sugar polymers include agarcarboxymethyl cellulosepectin and carrageenan. Other thickening agents act on the proteins already present in a food. One example is sodium pyrophosphatewhich acts on casein in milk during the preparation of instant pudding.
Different thickeners may be more or less suitable in a given application, due to differences in taste, clarity, and their responses to chemical and physical conditions.
For example, for acidic foods, arrowroot is a better choice than cornstarchwhich loses thickening potency in acidic mixtures.
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At acidic pH levels below 4. If the food is to be frozen, tapioca or arrowroot are preferable over cornstarch, which becomes spongy when frozen.
Many other food ingredients are used as thickeners, usually in the final stages of preparation of specific foods. These thickeners have a flavor and are not markedly stable, thus are not suitable for general use. However, they are very convenient and effective, and hence are widely used. Functional flours are produced from specific cereal variety wheatmaizerice or other conjugated to specific heat treatment able to increase stability, consistency and general functionalities.
These functional flours are resistant to industrial stresses such as acidic pH, sterilisation, freeze conditions, and can help food industries to formulate with natural ingredients. For the final consumer, these ingredients are more accepted because they are shown as "flour" in the ingredient list.
Flour is often used for thickening graviesgumbosand stews. It must be cooked in thoroughly to avoid the taste of uncooked flour. Rouxa mixture of flour and fat usually butter cooked into a paste, is used for gravies, sauces and stews.
Cereal grains oatmealcouscousfarinaetc. Yogurt is popular in Eastern Europe and Middle East for thickening soups.
Soups can also be thickened by adding grated starchy vegetables before cooking, though these will add their own flavour. Tomato puree also adds thickness as well as flavour. Egg yolks are a traditional sauce thickener in professional cooking; they have rich flavor and offer a velvety smooth texture but achieve the desired thickening effect only in a narrow temperature range. Overheating easily ruins such a sauce, which can make egg yolk difficult to use as a thickener for amateur cooks.Home made hand sanitizer gel (70%ethanol)
Other thickeners used by cooks are nuts including rehan or glaces made of meat or fish. Many thickening agents require extra care in cooking. Some starches lose their thickening quality when cooked for too long or at too high a temperature; on the other hand, cooking starches too short or not hot enough might lead to an unpleasant starchy taste or cause water to seep out of the finished product after cooling.
Also, higher viscosity causes foods to burn more easily during cooking. As an alternative to adding more thickener, recipes may call for reduction of the food's water content by lengthy simmering.Superabsorbent polymer SAP also called slush powder can absorb and retain extremely large amounts of a liquid relative to its own mass.
Water-absorbing polymerswhich are classified as hydrogels when mixed,  absorb aqueous solutions through hydrogen bonding with water molecules.
A SAP's ability to absorb water depends on the ionic concentration of the aqueous solution. In deionized and distilled wateran SAP may absorb times its weight  from 30 to 60 times its own volume and can become up to The total absorbency and swelling capacity are controlled by the type and degree of cross-linkers used to make the gel.
Low-density cross-linked SAPs generally have a higher absorbent capacity and swell to a larger degree. These types of SAPs also have a softer and stickier gel formation. High cross-link density polymers exhibit lower absorbent capacity and swell, but the gel strength is firmer and can maintain particle shape even under modest pressure.
The largest use of SAPs is found in personal disposable hygiene products, such as baby diapersadult diapers and sanitary napkins. The first commercial use was in for use in feminine napkins in Japan and disposable bed liners for nursing home patients in the USA. Early applications in the US market were with small regional diaper manufacturers as well as Kimberly Clark.
Until the s, water absorbing materials were cellulosic or fiber-based products. Choices were tissue papercotton, sponge, and fluff pulp. The water absorbent capacity of these types of materials is only up to 11 times their weight and most of it is lost under moderate pressure. They developed a resin based on the grafting of acrylonitrile polymer onto the backbone of starch molecules i.
The hydrolyzed product of the hydrolysis of this starch-acrylonitrile co-polymer gave water absorption greater than times its weight. Also, the gel did not release liquid water the way that fiber-based absorbents do. A wide range of grafting combinations were attempted including work with acrylic acidacrylamide and polyvinyl alcohol PVA. Today's research has proved the ability of natural materials, e.
Polysaccharides and proteins, to perform super absorbent properties in pure water and saline solution 0. Uses include agricultural and horticultural. Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a poly-acrylic acid sodium salt sometimes referred to as sodium polyacrylate. This polymer is the most common type of SAP made in the world today.
Other materials are also used to make a superabsorbent polymer, such as polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxymethylcellulosepolyvinyl alcohol copolymers, cross-linked polyethylene oxideand starch grafted copolymer of polyacrylonitrile to name a few. The latter is one of the oldest SAP forms created.
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Today superabsorbent polymers are made using one of three primary methods: gel polymerization, suspension polymerization or solution polymerization. Each of the processes have their respective advantages but all yield a consistent quality of product. A mixture of acrylic acid, water, cross-linking agents and UV initiator chemicals are blended and placed either on a moving belt or in large tubs. The liquid mixture then goes into a "reactor" which is a long chamber with a series of strong UV lights.Carbomer is the trade name for polyacrylic acid PAAa group of synthetic high molecular weight polymers of acrylic acid used in cosmetics and personal care products as thickening agents.
They are primarily added to gel-like formulations, such as facial moisturizerssunscreen, shampoo, anti-aging treatments, cleansers, and scrubs, to help control the viscosity, flow, and consistency of the product. The Carbomer polymers have been used in cosmetics for over 50 years.
An article from Cosmetics Info explains that the Carbomers are large molecules prepared from relatively small chemical compounds called monomes. The monomers used to make Carbomer polymers are acrylic acid and polyalkenyl polyethers. All of the Carbomer polymers are chemically similar, differing from each other in molecular weight and viscosity.
Dry Carbomer polymers come in the form of white, fluffy powders. You may notice a number associated with the Carbomer name on the ingredient label. This is the Carbomer code. Carbomer codes i. The Carbomer polymers can have varying pH levels that must be neutralized in order for them to function as thickening agents.
Formulations that contain Carbomer polymers will sometimes have these neutralizing agents listed. Other times, companies will purchase pre-neutralized Carbomer, which may or may not list the neutralizing agent.
There are claims that some of these neutralizing agents may carry contaminants that can be potentially carcinogenic.
An ingredient that is similar to the Carbomers is sodium polyacrylate, a sodium salt of polyacrylic acid. This ingredient is also used as a thickening agent and texture enhancer is cosmetics and personal care products since it is a superabsorbent polymer with the ability to absorb as much as to times its mass in water.
To understand the functions of Carbomers, it is important to first understand how they work. When a Carbomer polymer is placed in a water solution at neutral pH, many of the side chains will lose their protons and acquire a negative charge. Because of this reaction, Carbomers are able to absorb and retain water, and swell to many times their original volume. This is why Carbomers are considered to be texture enhancers and are used to add thickness to products, particularly gel-like formulations.
Additionally, Carbomers have the ability to distribute or suspend an insoluble solid in a liquid.There are many gelling agents. Though each gelling agent has some unique properties, there are some generalizations that can be made:.
As a group, they are dry powders, which have high bulk densities and form acidic aqueous solutions pH around 3. They thicken at higher pHs around 5 or 6. They will also swell in aqueous solution of that pH to as much as times their original volume. Their solutions range in viscosity from 0 to 80, centipoise cps. Some examples of this group of gelling agents are:.
Carbomer polymers are best introduced into water by slowly sprinkling a sieved powder into the vortex created by rapid stirring. This should prevent clumping. Once all of the powder has been added, the stirring speed should be reduced to decrease the possibility of entrapping air bubbles in the formulation.
As mentioned, when the carbomer is dispersed, the solution will have a low pH. A neutralizer is added to increase the pH and cause the dispersion to thicken and gel.
Some neutralizing agents are sodium hydroxide, potassium hydroxide, and triethanolamine. If inorganic bases are used to neutralize the solution, a stable water soluble gel is formed. If triethanolamine is used, the gel can tolerate high alcohol concentrations. The viscosity of the gel can be further manipulated by propylene glycol and glycerin to increase viscosity or by adding electrolytes to decrease viscosity.
The cellulose derivatives methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and carboxymethyl cellulose are commonly used. There are some commonalties in these compounds, and each one has their unique properties. The Pharmaceutics and Compounding Laboratory. Common Gelling Agents There are many gelling agents. Though each gelling agent has some unique properties, there are some generalizations that can be made: If the gelling agent is added to the dispersing medium in a haphazard manner, there is a tendency for the agent to "clump.
The clumps will ultimately hydrate, but it will take more time. A much more efficient manner is to sieve the agents onto the surface of the medium a little at a time as the medium is stirred. Using glycerin as a wetting agent will sometimes minimize clump formation.
Some gelling agents are more soluble in cold water than in hot water. Methylcellulose and poloxamers have better solubility in cold water while bentonite, gelatin, and sodium carboxymethyl cellulose are more soluble in hot water.
Carbomers, tragacanth, and alginic acid gels are made with tepid water. Some gelling agents carbomers require a "neutralizer" or a pH adjusting chemical to create the gel after the gelling agent has been wetted in the dispersing medium. Most gelling agents require 24 to 48 hours to completely hydrate and reach maximum viscosity and clarity. Gelling agents are used concentrations of 0. It is easier to add the active drug before the gel is formed if the drug doesn't interfere with the gel formation.
Will provide a low viscosity formulation. Forms clear gels with water. Very good clarity in water or hydroalcoholic topical gels.