EXPERT WITHIN THERMOANALYSIS AND ANALYTICAL CHEMISTRY

Antiblocking agents are used mostly in the packaging industry, where you want to prevent, for example, film material to stick to each other during manufacture, storage or use. These agents are mainly used for PP and LLDPE because they are most commonly used as packaging materials. Antiblocking agents work by roughening the surface to reduce surface contact. Common antiblocking agents are inorganic substances such as silica, talc, magnesium sulfate and carbonates of magnesium and calcium.

Antifogging additives

Water condensed on a surface inside, for example, food packaging does not look good and may even affect the food negatively. This can be solved in two different ways. One way is to add antifogging agents within the polymer which then migrates to the surface during the processing process. Here, they reduce the surface tension so that water is not accumulated in drops. Another solution is to add a coating that has the same function as the internally added antifogging agents.

Antioxidants

Antistatic Agents

Biocides

Biocides are added to either protect polymers from microbial degradation or to protect the surface so as not accumulating bacteria or similar organisms. Important biocides used are halogen and zinc compounds and even silver compounds are common. For PVC, a lot of OBPA (an oxybisphenoxarine) was previously used, but this use is reduced because the substance is an arsenic toxic compound.

Biodegradation promotors

There are additives added to polymeric materials to help them break down biologically. Some believe that they help to break down also common commercial polymers such as PET and PE. However, this has been tested and could not prove that it would be the case.

Fragrance additives

Fragrance additives can be added to mask a bad odor or give a specific aroma to a polymeric product. There are a wide variety of fragrances and flavors that can be added to polymers to make them smell in a special way (for example vanilla, citrus, etc.). It is also believed that in the future it will be possible to add smells to the plastic similar to what the product inside smells so that you can smell the packaging and get an idea of what's inside.

Extenders

Extenders are substances that you can mix into polymeric materials, primarily to reduce costs. For example, you can supplement plasticizers with extenders. For example, to PVC one can add epoxidized soybean oil or epoxidized linseed oil, which is much cheaper than plasticizers and they also to some extent have the same plasticizing effect.

Flame Retardants and smoke suppressants

Most polymeric materials are easily combustible and some also emit black smoke in the event of fire. There are various reasons for adding flame retardants / fire retardants / smoke suppressants and they have different mechanisms. You may want to make the polymer less combustible, you want to delay an ignition, you want to slow down the fire, or you want to reduce smoke evolution or change heat. Adding these agents not only gives positive properties but also negative. For example, chemical resistance changes, mechanical properties can be adversely affected, they can affect other additives, and they also make the polymer more expensive. Examples of common flame retardants are halogenated compounds (usually containing bromine) where they emit a halogenated gas (e.g., HBr) that affects the combustion. Antimony and zinc compounds improve the ability of the previous as well as make ignition difficult. Antimony also promotes char formation that isolates the heat. Phosphorus substances are often found in electronic products, aluminum trihydrate (ATH) is common and forms water and aluminum oxide. Furthermore, there are also borates, nitrogen compounds and tin compounds.

Fillers

Fillers can be added for various reasons. An important reason from the start was to try to reduce costs because fillers are cheaper than polymers and you could therefore dilute the more expensive polymer with cheaper substances. However, it is believed that cost savings do not get as high since there are some process steps that add costs. Fillers are often added to change certain properties of the polymer or improve processing and facilitate process equipment. Key features that change are stiffness, hardness, and decrease in creep. Common fillers are calcium carbonate, coal, kaolin, mica, talc, wollastonite. There are also nanofillers for which you use the large surface and you do not need to add so much to obtain the properties needed.

Colorants

Coloring agents are added to give the polymer just the color you want. Often, a so-called "master batch" is purchased in which all additives and pigments already exist in solid or liquid form. When adding colors, make sure that the color is compatible with the polymer. Certain pigments come from minerals that also contain other contaminants that can lead to incompatibility.

Blowing agents (foaming agents)

These substances are added to form gas bubbles in the liquid polymer. This procedure reduces the density and increases the volume of the polymer and thus it require less polymer to a larger volume. It is used to improve a material's insulation properties. There are both chemical and physical means for producing gas bubbles. The chemical, through a chemical reaction, forms a gas such as carbon dioxide or nitrogen to form gas bubbles in the molten polymer. The physical means give gas bubbles through evaporation where you can use hydrocarbons and earlier even freons. Nowadays it is common to form gas bubbles directly using gases like water vapor, carbon dioxide or nitrogen gas, but these are not counted as an additive.

Clarifying agents (nucleating agents)

Clarifying agents improve the optical properties of polymeric materials by reducing the size of the crystalline portions that spread light. This is done by initiating more nucleating sites so you get many small ones instead of fewer larger ones. This also reduces light scattering. Clarifying agents are therefore also nucleating agents. PP is the polymer using most additives. Examples of clarifying agents may be sorbitol derivatives. Nucleating agents affect the crystallization process by starting crystallization at several different positions. These create better mechanical properties and shorter cycle times in processing and manufacturing processes. Common nucleating agents are benzoates and minerals such as talc and kaolin.

Combination agents

Polymer blends are common and cover almost one third of the world's polymer consumption. Blending of polymers is common to achieve certain specific properties or to reduce costs by blending a more expensive polymer with a significantly cheaper one. In blends, compatibilisers may be needed to make the mixture miscible and not form two different phases. Compatibilisers are often polymers containing units of segments that are compatible with the polymers to be blended.

UV and light stabilisers

Air releasing agents

Air release agents are often used for thermosets. Here two components are mixed and air comes into the mixture that you need to get rid of. Then these agents are added to work in a two-step mechanism. First, air bubbles are eliminated and then they are transported to the surface and disappear.

Low profile additives

So-called low profile agents (LPA) are used for thermosetting plastics where you want to reduce the shaping of the molded product during polymerization. They can also be added to glass fiber reinforced plastics for better surface finish.

Plasticizers

Plasticizers are used almost exclusively for PVC. They increase the polymer's flexibility and resistance to cracking especially at low temperatures. If a polymer is to be soft, it must be compatible with the plasticizer as well as some but not too much crystalline. There are not many polymers except PVC that can meet these requirements. Common plsticizers used are phthalates (eg DEHP, DINP, DIDP) but many of them are phased out because of their hormone-destructive effects. Recently, some of these (DEHP, DBP, DIBP and BBP) were brought up by the EU on the list of substances that should only be used in exceptional cases. Other plasticizers used are citrates (designated as safe), trimellitates (tolerate higher temperatures), adipates, sebacates, etc. Plasticizers also affect the manufacturing process.

Rodent repellants

Some polymer products such as cables and pipes may need to be protected from, for example, rodents. Then you can add additives to protect the products. This can be done, for example, by filling an acrylic polymer with a mixture of smelly chemicals and very bitter components.

Optical brighteners

Optical brighteners or clarifying agents may be added to enhance certain colors or may be added to mask the yellowing of certain polymers. It is often organic substances that absorb UV light. The colorless dyes work by releasing visible light when they absorb invisible UV light.

Pigment dispersants

When adding pigments or other solids to a liquid mixture, one needs an additive that helps to distribute and stabilize the mixture. Then one has to add a dispersant. It reduces the volatility of the mixture and makes it stable so that it is not separated after a while.

Polarising additives

These agents can be added to only pass through polarized light through a polymeric material. These additives are widely used for sunglasses made in polymeric materials.

Antiscratch agents

Often, one would like the appearance of a product to be as good as possible during its lifetime. Some polymers such as PP are very scratch sensitive and do not look good after a while. To improve appearance and make the polymer less sensitive antiscratch additives are added. It not only makes the surface finer and more attractive, but it prevents scratches in which it can accumulate dirt and microorganisms. Common antiscratch agents contain silicone polymeric parts.

Impact modifiers

Some polymers crack easily under stress especially at low temperatures. Then there is the possibility of adding impact modifiers in order to increase its ability to resist cracking. Impact modifiers are usually rubber components (e.g., polybutadiene) which in the polymer matrix works by diverting the mechanical energy and thus stop cracking. The polymers that are most commonly have added impact modifiers are PS, PMMA, PVC, epoxy and polyester.

Releasing agents

Releasing agents can be used with antiblocking agents to reduce friction. These additives function by being added to the molten polymer and when polymer crystallizes they are separated to the surface where they form a low-friction layer. Releasing agents often consist of long amides containing a cis-double bond which prevents them from crystallizing. Examples of common release agents are erucamide, oleamide and stearamide. One should be aware that these agents can easily get caught on processing equipment.

Lubricants and processing aids

Lubrication and processing aids often have same properties. Lubricants help improve flow behavior. You can divide these substances into internal and external lubricants. External migrates to the surface and prevents polymer adhesion to the surface of the processing equipment. Internal lubricants are more miscible with the polymer and affect the flow character, reduce shear stresses and allow lower process temperatures to be used and reduce wear and tear on equipment. There is also a reduced risk of thermal degradation and improved surface finish. Lubricants for PVC are usually fatty acids such as stearic acid or hydroxystearic acid, stearates, amides or alcohols. Polymers other than PVC have less lubricant requirements. Releasing agents and / or antiblocking agents usually provide sufficient effect. Process aids are added in small amounts to reduce defects and improve process properties.

Oxygen scavengers

Oxygen scavengers are especially important in food packaging. By adding these, you can reduce the oxygen content of the package and thus extend the product stability. Ethylene unsaturated hydrocarbons (usually 1,2-polybutadiene) and fatty acids can be embedded in the polymer package (such as PE, PP, PS) and extend the food stability by significantly reducing the oxygen content.

Thixotropic additives

Thixotropic additives may be added to change the viscosity of the polymer blend and improve the injection molding process so that, for example, the blend is not too thin and flows too much inside the mold.

Desiccants and channelling agents

In some packages it may be important to keep the product (such as a food) inside as dry as possible. Here you can then create a desiccant inside the packaging material (the polymer). You first mix a channelling agent into the polymer and then a desiccant. When the product is shaped and ready, channels have formed into the polymer where moisture can enter and reach the desiccant that takes care of it.

Tribological additives

These are additives that can be added to reduce mechanical wear of a polymer by friction. Common additives are PTFE, graphite, silcon and various carbon and glass fibers.

Heat stabilizers

Heat stabilizers are added to protect against degradation due to heat. PVC is a polymer that must have these stabilizers. Otherwise the PVC polymer will be easily degraded. Previously, some lead compounds were used to stabilize PVC but these are phased out due to environmental impact and toxicity. It is common to use a combination of two metal carboxylates where common combinations are barium zinc, calcium zinc or even a triple system of calcium-barium zinc.

Surfactants, nucleating agents and catalysts

For example, in the manufacture of polyurethane foam, a number of different additives are necessary in this process, including surfactants, nucleation agents and catalysts, which play an important role.