Doc Brown's Chemistry Notes on Formulation Chemistry

What is formulation Chemistry? What are formulations?

(Suitable for AQA, Edexcel and OCR GCSE chemistry students)

Examples of Formulation Products

INTRODUCTION

Alphabetical list of formulations mentioned

adhesives * antiperspirants * cosmetics * deodorants * detergents * dietary supplements

hair colouring * herbicides * inks * nail polish * paints * perfumes * pesticides

petrol * petroleum oil products * pharmaceutical products * sunscreens/sunblockers

INTRODUCTION

Well, examples of the products of formulation chemistry are adhesives, antiperspirants, cosmetics, deodorants, detergents, sunscreens (sunblockers), paints, dietary supplements, hair colourings, herbicides, inks, nail polish, paints, perfumes, pesticides, fuels like petrol or diesel, pharmaceutical products e.g. medicines like headache tablets, alloys, fertilisers and alloys.

Formulation chemistry is the mixing of substances of specific amounts that do not react with each other but produce a mixture (the FORMULATION) with the desired characteristics/properties to suit a particular application/use.

Many modern products contain a combination of several chemical substances, each contributing an advantage to the finished product for a particular application.

Commercially, they are made up from recipes of tried and tested formulations for a particular purpose.

If you look around the house, especially in the kitchen and bathroom, you will lists of ingredients on the side of the bottle or package of products - percentages or relative amounts of the components in the formulation.

This information might be important in your choice of product i.e. you can choose the formulation with the best composition for you particular use.

Most products list the ingredients with any warning signs or advice on the use of the formulation on its packaging. Laws are getting stricter, so beware of any product that does not clearly state what is in the formulation!

People with allergies and other particular medical conditions need to take extra care with many, albeit common, proprietary products.

Because a formulation is a mixture that has been specially designed as a useful product for a particular purpose, many such products are complex mixtures in which each chemical has a particular purpose.

Formulations must be made by mixing the components in carefully measured quantities to ensure that the product has the required properties with no health or safety issues.

Many common formulations like fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods you will very familiar with these proprietary products, and how useful all these formulations are!

What would we do without these formulation products!

Any developed product must be commercially viable i.e. a useful profitable material, so, almost every example quoted below, you will actually find in your home i.e. a broad range of useful household products are the result of the science of formulation chemistry.

Since no reactions happen in making the mixture, most formulations are prepared by measuring liquids by volume and solids by mass ('weight').

It is perfectly possible for a marketed product to go on sale without a chemical equation ever being written down! However, there may be much chemistry going on to actually make some of the ingredients e.g. chemically synthesising a drug is one matter, mixing it with water and other ingredients to make a liquid medicine for oral consumption is another!

Although there are no chemical reactions involved in preparing formulations, there are many chemical aspects to do with formulation.

These include thermodynamics (energy changes) of mixing, phase equilibria, solutions, surface chemistry, colloids, emulsions and suspensions.

These important principles and ingredients may be related to properties such as adhesion, weather resistance, texture, shelf-life, biodegradability, allergenic response and many other properties.

By changing the composition of the mixture, its properties will change to be more or less suited to a particular useful application.

Quite a bit of trial and error goes into product formulation research and even computer programmes have been developed to model and therefore predict the properties a mixture may have - BUT its still got to be tested in the laboratory.

Formulations and GCSE level: You would be expected to appreciate that a formulation is a mixture that has been designed as a useful product, often a complex mixtures in which each chemical has a particular purpose.

Formulations are prepared by mixing the components in carefully measured quantities (mass of solid or volume of liquid or solution) to ensure that the product has the required properties for the desired purpose which may include fuels, cleaning agents, paints, medicines, alloys, fertilisers, foods and many other proprietary products.

Paints

A paint is made up of a base pigment, a mixture of compounds to give the paint a particular colour.

A binder and a solvent to dissolve some of the components to give a well mixed composition and to give the paint the right sort of viscosity ('stickiness').

The solvent eventually evaporates to give a hard solid surface finish (matt or gloss depending on the composition).

There may be other additives to give paints and the finish other distinctive properties.

Binders (resins) bind the pigment to the surface painted and pigments must be insoluble materials e.g. titanium dioxide and zinc oxide are used as white pigments (and have replaced potentially harmful lead pigments). Sometimes the binding action involves a chemical change e.g. polymerisation. Acrylic paints use polymer resins as a solvent and can be thinned with water, but still dry easily and the resin sets hard.

Paints may be water, latex, oil, acrylic or epoxy based. House paints must be reasonably durable at a reasonable price but high durability paints used for car and aircraft bodies are more costly.

Thermochromic paint - changes colour when heated i.e. the colour observed is depends on the temperature.

Photochromic paint - changes colour on exposure to light i.e. observed colour depends on light intensity.

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Inks and Dyes

There is a huge variety of inks available of different compositions to suit different circumstances. Ink used for newspapers or paperback novels must be cheap and have the consistency of a thick sludge to properly feed through the ink rollers of a printing press. Good colour quality is required for glossy magazines. As well as colour composition, appropriate ink flow is important for pens and computer printers. The performance and formulation of a good photocopier or laser printer toner depends upon its electrostatic properties.

Dyes, natural or synthetic (dyestuffs) are used to colour fabric materials.

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Cosmetics and other 'personal products'

The cosmetic industry provides a wide range of formulated products. In the bathroom/bedroom you may find perfumes, moisturizers, rouge, lipstick, anti-aging skin products, face powder, nail polish, sunscreen/sunblocker, hair gel, hair conditioning and colouring products, aftershave and deodorants etc.

In the highly competitive world of cosmetics developments in non-allergenic formulations and longer wearability factors have become increasingly important and the way they look and easy application all help to make a product line more marketable.

Nail polish consists of flexible lacquers, organic dyes for colouring effects, iron or chromium oxides, and ultramarine blue along with drying agents and binders and solvents such as ethyl ethanoate ( ethyl acetate) that evaporate on drying. Nail polish remover is usually an organic solvent such as propanone (acetone) or ethyl ethanoate.

Perfumes have been used for thousands of years and first recorded for posterity by the Egyptians? They and other cultures extracted fragrant substances from plants such as pleasant smelling flowers like roses, geraniums and from lemon oils. Animal extracts like musk were added later. The first perfumes were probably developed to mask the odours from the body or disease - good hygiene is a relatively modern concept! Perfumes are mixtures of various components blended to produce a pleasing scent that will last for several hours. Each fragrant component is called a note. The first note 'impression' is the odour perceived when the scent/perfume is opened or sprayed. The second note is detected after the perfume has made contact with the skin, and the third note is the component to make the fragrance last for a reasonable time. High-quality perfumes are mixtures of 'highly selected' substances that appeal on a personal level. Typical ingredients include extracts of flowers and fragrances such as valerian, lavender, chamomile, passionflower, vanilla, geranium, mint, lemon as well as ambergris or musk, and water or alcohols. The formulation of perfumes is a mixture of 'art' and 'science' and new products are constantly appearing in the 'market place'. As well as products for personal use, perfumes/fragrances are now used in numerous cleaning products and for spraying around the house! Cleopatra would have loved, and been a great patron of the modern cosmetics industry!

Hair colouring products are either temporary or permanent. Temporary hair colours attach to the surface of hair and wash out after repeated shampooing. A dye is considered permanent if it penetrates into the hollow hair fibres. Colouring of hair starts with a treatment of substances such as hydrogen peroxide and ammonia. The ammonia causes hair shafts to swell and open, allowing dye intermediates and couplers to penetrate. Dyes applied during the second step of colouring react with the intermediates/couplers to form pigments that remain in the hair. Melanin compounds determine hair colour and the density of melanin granules determines the shade. Hair colours are combinations of organic dyes chosen to produce particular shades. Hair that contains little or no melanin is very light coloured or white. Hair can be deliberately bleached with oxidising agents like hydrogen peroxide which destroys melanin.

Deodorants and antiperspirants are often mixed in the same formulation. It should be admitted that deodorants don't usually remove bad body odours, but mask them with a more pleasant smell, but some can inhibit the microorganisms that cause body odour in the first place. Deodorants contain a mixture of strong perfumes e.g. with minty or musky odours. Body odour can be partially reduced by decreasing perspiration, a natural gland function primarily to cool the skin and get rid of excess heat, but perspiration carries pheromones and fatty acids with the resulting odour, as well as the excretion of odourless salt. One active wisely used ingredient of antiperspirants is aluminum chloride and when aluminum ions are absorbed by cells in the epidermis cause the sweat gland ducts to close.

Sunscreens/sunblockers/suncreams absorb/block harmful ultraviolet (UV) radiation and allows the skin to tan. UV rays are high energy photons and can cause cancer by damaging DNA and excess UV exposure causes increased wrinkling of the skin. Many of the older 'suncreams' contained organic molecules (usually aromatic compounds) that absorb ultra-violet light (but not necessarily all the UV light) so many products now use reflective-blocking properties of fine zinc oxide (ZnO) and titanium dioxide (TiO₂) particles (nanoparticles) because they block a much wider variation of the wavelengths/frequencies of UV light. There are several factors to consider in formulating a particular product e.g. (1) Most aromatic compounds are potentially carcinogenic and/or interfere with hormones so low concentrations are used to minimise risks. (2) The active ingredients should not precipitate out of the solution/cream or the product feel gritty. (3) It is now possible to encapsulate the active ingredients, i.e. the sunblockers, in tiny polymer bags so the active chemicals do not come into contact with the skin.

Hair gel -

Toothpaste -

Shaving foam -

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Detergents - liquids/gels (e.g. washing up liquids/shampoos) and soaps blocks/powders

Detergents are a type of surfactant molecule in that changes the surface tension of the 'washing' solution and act as wetting agents. Enzymes are added to 'biological' washing liquids/powders/detergents. A good acting enzyme is one which efficiently breaks down the organic matter that some stains are made of with zero/minimal damage to the organic matter which the clothes are made of. Washing up liquid detergents are formulated to effectively clean without harming the skin of the person doing dishes.

Water is a polar compound that readily dissolves most salts and polar compounds such as sugar but it will not dissolve non-polar fatty/oily substances from the body. Non-polar solvents such as alkane hydrocarbons (hexane etc.) and chlorinated hydrocarbons like 1,1,1-trichloroethane (CH₃CCl₃), tetrachloromethane (CCl₄, carbon tetrachloride) do not really mix with water (immiscible), but will dissolve nonpolar substances such as grease or oil.

Shampoo contains a mixture of ingredients, including detergents, that allow water to wet the nonpolar oils found in bodily secretions such as sebum, the oily substances which holds dirt and dead skin in hair. Common detergents include sodium or ammonium lauryl sulfates (lauryl sulphate is an anion - negative ion). Cationic detergents, which act to condition hair as well remove dirt and oil from it, include alkyl ammonium compounds such as stearylammonium chloride or sulphate. Other components of shampoo include surfactants such as polyethylene glycol, antifoaming agents, thickeners, antistatic agents, and buffers (pH balancers) as well as colouring agents and perfumes to make them more attractive to the consumer.

Most soaps are sodium or potassium salts of fatty acids that function well as surface active or wetting agents (soaps!) because they are soluble in water but the hydrocarbon chain can interact with grease, oils and other 'fatty' material to dislodge such materials in the washing process. However, calcium and magnesium ions in hard water form insoluble compounds with these fatty acids that dull shower/was basin walls etc. i.e. scum formation! Shampoos/washing up liquids etc. therefore contain chelating agents such as ethylenediaminetetraacetate (EDTA) that form soluble complexes with the magnesium/calcium ions and stopping 'scum' precipitates forming. In addition, a surfactant such as an ethylene glycol ether wets the wall so water droplets run off. Propan-2-ol (2-propanol, isopropyl alcohol) is a solvent both for the shampoo ingredients and helps dissolve substances such as oils that are not water-soluble.

Research is being done to utilise bleach substitutes.

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Pharmaceutical products - administering drugs and medicines

One of the most important aspects of the pharmaceuticals industry relates to drug delivery, i.e. what is the best means of administering a drug?

The tablet (pill) must ensure the drug

(i) goes to right part of the body,

(ii) is the correct dose - safe effective amount,

(iii) the correct concentration to match (ii) above,

(iv) its palatable to the consumer and a long enough shelf life so that it doesn't 'go off' and become ineffective.

The usefulness of a drug is not just about its effectiveness in treating a condition but also on how readily it can be given to the patient.

A tablet with little taste is one of the most convenient and successful methods of administering medicines.

Tablets can be formulated with additional ingredients to prevent stomach upset, give a timed release and hold the tablet together as a solid.

Liquid medications of an 'unpleasant' tasting drug can be mixed with (mouth watering!) flavourings to mask the taste of the medicine.

(i) and (ii) are the two possible structures of the active ingredient of Aspirin.

(i) the non-salt like insoluble acid (-COOH group) and

(ii) the water soluble sodium salt-like form produced by neutralising the acid.

You can have a formulated mixture of (i) and sodium hydrogencarbonate in the tablet which then dissolves in water to form (ii) administered in the form of a 'fizzy' drink.

Potential side-effects not seen when using an individual drug, but occur with a mixture of assumed beneficial ingredients.

Pharmaceutical formulations can be very sophisticated both in design and delivery.

You need to ensure the right concentration and dose and it gets to the right part of the body to be effective formulation.

Even shelf-life is important - you may need to store a medication for future use, so the formulation may need to be stable for a long time.

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Adhesives

Generally speaking an adhesives is a mixture of a bonding agent and a solvent, which fill surfaces at the microscopic level and harden as the solvent evaporates. Some adhesives, such as super glue - epoxy resins do undergo a chemical reaction as they harden. Silicon based adhesives are used for high temperature applications such as car exhaust repairs.

Fertilisers, Pesticides and Herbicides - agrochemicals

Herbicides are chemicals that are used to control/inhibit plant growth e.g. plants deemed as weeds. Since they tend to be harmful, the formulation and means of delivering herbicides are very important factors in the application.

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Petroleum Oil Products

Much of western society runs on fossil fuels like petrol (gasoline), diesel fuels and heating oil etc. All these are products distilled and blended (i.e. formulated) from petroleum oil to give the product its desired properties. However, it isn't just about combustion, although they all burn well to release heat energy (exothermic combustion reaction), their physical properties are very important too and additives for various reasons may also be added to the hydrocarbon mixture to make up the final 'fuel formulation'.

Crude petroleum oil is complex mixture of hundreds of different hydrocarbon compounds (molecules of H and C atoms) and generally speaking the bigger the molecule i.e. the longer the carbon chain the higher the boiling point (less easily vapourised) and the more viscous ('sticky') the liquid. These are very important factors in designing the formulation of a fuels for a specific combustion process e.g.

Petrol ('gas', gasoline for cars, automobiles) must be a readily vapourised liquid in the carburettor and injected into the cylinders of a car engine so they tend to be relatively small molecules of 6-11 carbon atoms (C₆H₁₄ to C₁₁H₂₄). Smaller molecules like methane (CH₄) or propane (C₃H₈) would be a gas and not conveniently poured into petrol tank! If the molecules were bigger they would not be as readily vapourised and ignited in the car engine cylinders.

Apart from this molecular size factor there are other problems to overcome in using petrol like 'knocking' which is caused by ignition at the wrong time causing engine vibration. This is inefficient combustion and the vibration can damage the engine.

The different blends or formulations of petrol are given an octane rating. A smooth burning fuel has a higher rating than a 'knocking' burning fuel. The straight chain alkane hydrocarbon called heptane (C₇H₁₆, right) is given an octane value of zero.

The much smoother/cleaner burning fuel iso-octane (left), which has a much higher octane rating is an isomer of octane C₈H₁₈ and a highly branched alkane whose real name is 2,2,4-trimethylpentane! The higher the octane rating of the fuel formulation the smoother the fuel burns without knocking in high compression engines.

The octane rating of petrol/gasoline can be raised by adding branched-chain alkanes like iso-octane, cyclic alkanes and oxygenated organic molecules which may be alcohols or ethers, all of which burn more efficiently and cleanly. Therefore it is possible to blend/formulate mixtures of these alkane hydrocarbons into a variety of petrols of different octane rating for different engines. Not surprisingly, the higher the octane number, the higher the price! though combustion efficiency should increase to partly compensate for this.

You can produce a range of petrol formulations by mixing alkane hydrocarbons and ethanol ('alcohol') in different proportions to give different octane values. Brazil has no oil reserves so it imports crude petroleum oil, but it produces lots of sugar cane which can be fermented to ethanol, which it then mixes with petrol from oil.

Historic note - the first octane enhancers were lead compounds such as lead tetraethyl because it was found that a few milligrams per litre of this compound converted cheaper low octane petrol into a much higher octane fuel. The lead compounds have also been phased out for another reason - lead poisons the active surface in catalytic converters which convert harmful carbon monoxide (CO) into carbon dioxide (CO₂) and nitrogen oxides (NO, NO₂) into harmless nitrogen (N₂).

Finally a mention of summer/winter mixtures in petrol formulation. Since the average temperature is higher in the summer than winter, then the volatility of petrol will vary accordingly. The summer petrol blends contain more less easily vapourised hydrocarbons compared to winter formulations and vice versa. This means the ease of volatilisation will stay roughly constant through the year.

Other products derived from petroleum oil

Polymers can be produced to have a variety of physical properties. They are synthesised from oil derived compounds such as alkenes to make poly(ethene) ('polythene'), poly(propene) ('polypropylene', 'polyprene' etc.).

Various additives are used to colour the plastic and plasticizers are added to make it more flexible.

Flexibility is important for electrical cables and clothing and shock absorbance in footwear.

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Food Industry Products: Additives, Dietary supplements

Vegetable oil and margarine - vegetable oil (liquid) is ok as an ingredient in salad dressing emulsion (a sort of formulation!), but needs to be hydrogenated to give a soft solid (margarine) to spread on bread.

Ice creams

Salad dressing/mayonnaise - an emulsion

Processed food contain permitted food additives (given an E number) to improve appearance (colouring), taste (artificial flavours) and shelf-life (so can store safely for a longer time). The potential negative aspects should be considered too e.g. harmful/toxicity? hyperactivity linked to tartrazine.

antioxidants - vitamin C prevents deterioration due to reaction with ingredients with the oxygen in air

flavourings - use of esters, ethanoic acid (acetic acid, vinegar)

flavour enhancers - monosodium glutamate

colourings - food colours like tartrazine

preservatives - benzoic acid/ethanoic acid (vinegar) inhibit the growth of harmful bacteria

sweeteners - aspartame to reduce amount of sugar/calories taken in

thickeners - starch

emulsifiers and stabilisers? help to mix ingredients together and to stop them separating out like oil/cream and water. An emulsifier molecule has water loving part (hydrophilic) and a 'water hating'/'fat loving' part (hydrophobic).

The molecular structure of vitamin C ('ascorbic acid') one of many compounds incorporated in multi-vitamin tablet formulations and is used as an antioxidant.

Baking powder: The thermal decomposition of sodium hydrogencarbonate to give carbon dioxide and subsequent rising action in the bread dough (baking soda addition or self-raising flour) or cake mixtures. Can have solid citric acid in raising mixture, no reaction in solid mixture, but reaction between acid and carbonate occurs in presence of water to give carbon dioxide.

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Other examples of formulated products:

Aerosols -

Fire extinguishers - water, foam, powders, flame retardant liquids/gases

nanotechnology - nano-sized silver particles used as an anti-bacterial, antiviral/antifungal sterilising sprays to clean operating theatres and coat inner surfaces of refrigerators (mentioned in several GCSE science syllabuses)

anticorrosion liquids - in central heating water systems

antifreeze - car cooling systems

cleaning agents - bleaches, TCP

refrigeration liquid/gas mixtures - CFC's banned, replacements developed

Smart materials -

Metal or plastic alloys (mixtures) are classed as formulations.

For notes on alloys see metal structures * transition metals

Related on-site pages involving the chemical industry:

Uses of Chemicals - a quick summary reference table of the use of 220+ elements, compounds or mixtures

Oil Products and their uses - notes on oil, fuels, combustion, alkanes, alkenes, alcohols, polymers, drugs, food additives etc.

Extra Notes on Industrial Chemistry - Limestone, Enzymes, Titanium, Sulphuric Acid etc.

Transition Metals - GCSE level notes on their physical and chemical properties and uses

Ammonia, ammonium salts and fertilisers notes on ammonia synthesis and its uses