Ethan Clarke
Polyvinyl chloride (PVC) is the third most widely used plastic. Without plasticizers, PVC is hard and brittle. Plasticizers are added to polymers and plastics such as PVC to increase their plasticity and make them softer, more flexible, and easier to handle during manufacture. Plasticizers are organic substances that intercalate the rigid polymer structures of PVC, making them more precisely plastics. Plasticizers are classified based on their chemical composition, with the most common being phthalate esters. They are distinguished between primary and secondary plasticizers, each with specific characteristics that influence the properties of plasticized PVC.
| Characteristics | Values |
|---|---|
| Definition | A plasticizer is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. |
| Use in PVC | Plasticizers are commonly added to polymers and plastics such as PVC, to facilitate the handling of the raw material during fabrication, or to meet the demands of the end product's application. |
| Types | Liquids are usually called "plasticizers", whereas solids like nitrile rubbers, compatible polyesters and some polyacrylates are called plastifiers or flexibilizers. |
| Migration | Plasticizers may migrate from plasticized PVC by contact with other polymeric substances if the resistance at the interface is low and if the plasticizer is compatible with the second polymer. |
| Efficiency | Plasticizer efficiency is used to describe the ability of a plasticizer to make the product softer and is reported as a ratio of the slope of the hardness versus plasticized concentration to the slope of that found for DOP. |
| Temperature | The effect of plasticizers on elastic modulus is dependent on both temperature and plasticizer concentration. |
| Safety | Substantial concerns have been expressed over the safety of some polymer plasticizers, especially because some low molecular weight ortho-phthalates have been classified as potential endocrine disruptors with some developmental toxicity reported. |
| Examples | Phthalates, sebacates, adipates, terephthalates, dibenzoates, glutarates, azelates, lignosulfonates, and more. |
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What You'll Learn
Plasticizers make PVC softer and more flexible
Polyvinyl chloride (PVC) is the third most widely used plastic. Without plasticizers, PVC is hard and brittle, but with them, it becomes flexible and soft. Plasticizers are organic substances that intercalate the rigid polymer structures of PVC, making it easier to move and more flexible. They are added to polymers and plastics like PVC to increase their plasticity, decrease their viscosity, and reduce friction during handling and manufacture.
PVC plasticizers are commonly used in the production of electrical cables, as well as in the construction industry, flooring, metal surfaces, and automotive interior trim. They are also used in plumbing, roofing, vinyl flooring, rain gutters, and electric wire insulation. The largest market sector for plasticizers is the film, sheet, and coated fabric market sector. These products are used to produce a wide variety of goods, including tablecloths, packaging films, swimming pool liners, tarpaulins, agricultural films, wall coverings, office products, awnings, shower curtains, upholstery fabrics, and shoe fabrics.
Plasticizers are classified based on their chemical composition, with the most common type being phthalate esters. They can also be categorised as primary or secondary plasticizers, each with distinct characteristics that influence the properties of plasticized PVC. Primary plasticizers enhance elongation, softness, and flexibility, whereas secondary plasticizers typically cannot be used as the sole plasticizer in a plasticized polymer. Examples of primary plasticizers include monomeric, polymeric, epoxy, and specialty flame-retardant plasticizers, while secondary plasticizers include chlorinated paraffin oils with various degrees of chlorination.
The efficiency of a plasticizer is determined by its ability to soften the product and is influenced by factors such as temperature, mobility, and concentration. The molecules of plasticizers control the mobility of the polymer chain, and their presence can decrease the glass transition temperature and elastic modulus of PVC. The balance between the polar and non-polar portions of the plasticizer molecule is critical to controlling the solubilizing effect.
The selection of the right plasticizer for a specific application is crucial to achieving the desired softness and flexibility in PVC.
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They are organic substances that intercalate rigid polymer structures
Plasticizers are organic substances that are added to polymers and plastics such as PVC to increase their plasticity, decrease their viscosity, and/or decrease friction during handling in manufacture. They intercalate rigid polymer structures, making them softer, more flexible, and easier to shape and mould. This process is known as plasticization, and the final product is referred to as plasticized PVC or flexible PVC.
PVC without plasticizers is hard and brittle, but with the addition of plasticizers, it becomes suitable for products such as vinyl siding, roofing, vinyl flooring, plumbing, and electric wire insulation. Plasticizers are also added to concrete formulations to make them more fluid for pouring and workable, thus reducing the amount of water required.
The molecules of plasticizers take control of the mobility of the polymer chain. They embed themselves between the chains of polymers, spacing them apart and increasing the free volume. The effect of plasticizers on the elastic modulus of the polymer depends on both temperature and plasticizer concentration. The ideal plasticizer should have a balance between polar and non-polar portions to control the solubilizing effect.
There are two main types of plasticizers: primary and secondary. Primary plasticizers enhance elongation, softness, and flexibility and are highly compatible with polymers. They can be added in large quantities, up to 50% in some cases, like in vinyl gloves. Secondary plasticizers typically cannot be used alone as they have limited compatibility with the polymer and/or high volatility. However, they can be used with primary plasticizers to reduce costs.
The most common type of plasticizer used in PVC is phthalate esters, which provide improved flexibility, durability, and UV resistance. Other types include polymeric plasticizers, which have high migration resistance and good resistance to high temperatures, and adipate esters, which improve low-temperature performance.
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Plasticizers are liquids or solids with low volatility
Plasticizers are substances added to materials to make them softer, more flexible, and easier to handle and mould. They are commonly added to polymers and plastics, especially polyvinyl chloride (PVC), to improve their flexibility and workability. Without plasticizers, PVC is hard and brittle, but with them, it becomes suitable for products such as vinyl siding, roofing, vinyl flooring, plumbing, and electric wire insulation.
Plasticizers are either liquids or solids with low volatility, and they are classified as primary or secondary. Primary plasticizers are low-volatility liquids that are compatible with PVC and exhibit good permanence and high efficiency. They are essential in modifying the flexibility and workability of the polymer. The most efficient plasticizers are the most highly solvating and fastest fusing. The amount of plasticizer needed to obtain a certain hardness or elongation is a measure of its efficiency.
Secondary plasticizers, on the other hand, have opposite characteristics and will exude if used alone. However, they can be used with primary plasticizers to reduce costs. Examples include chlorinated paraffin oils with various degrees of chlorination.
The selection of a plasticizer depends on meeting a combination of end-use performance requirements, processing needs, costs, and regulatory requirements. The efficiency of a plasticizer is determined by its ability to make the product softer, reported as a ratio of hardness versus plasticizer concentration. Plasticizer efficiency increases as the molecular weight of the plasticizer decreases and as the linearity of the alcohol chain increases.
The migration of plasticizers from PVC to other polymeric substances can occur if the resistance at the interface is low and if the plasticizer is compatible with the second polymer. Serious migration can result in a substantial loss of plasticizer and stiffening of the PVC. An example is the softening of nitrocellulose or acrylic lacquer following prolonged contact with plasticized PVC.
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They are classified based on chemical composition and intended use
Plasticizers are organic chemicals that improve the flexibility, viscosity, softness, friction level, and plasticity of materials. They are commonly added to polymers and plastics such as PVC, either to facilitate the handling of raw materials during fabrication or to meet the demands of the end product's application.
Plasticizers are classified based on chemical composition and intended use. The most common classification is based on chemical composition, with several chemical families fitting the description of plasticizers. The most common among them are phthalate esters, produced by the esterification of phthalic anhydride or phthalic acid. Phthalate esters have useful properties such as low volatility, weather resistance, low solubility in water, and remarkable resistance to biodegradation. They are compatible with PVC polymers, making them suitable for various applications.
Another classification of plasticizers is based on their intended use. For example, energetic plasticizers are used in fuels and propellants to improve their physical properties and specific yield. They are commonly used in smokeless gunpowder and rocket propellants to extract more energy from the propellants. However, energetic plasticizers can be expensive and unsafe.
Plasticizers can also be classified as primary or secondary plasticizers, each with specific characteristics that influence the properties of plasticized PVC. Primary plasticizers are low-volatility liquids that are compatible with PVC and will not be easily removed by moderate pressure. Secondary plasticizers are also low-volatility liquids, but they will exude if used alone. They can be used with primary plasticizers to reduce costs.
Additionally, plasticizers can be classified as general-purpose or performance plasticizers. General-purpose plasticizers provide the desired flexibility to PVC while balancing quality and cost. Performance plasticizers offer secondary desired properties beyond general-purpose plasticizers but are more costly.
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Safety concerns have been raised over some polymer plasticizers
Plasticizers are substances added to materials, usually polymers and plastics like PVC, to make them softer, more flexible, and easier to handle during the manufacturing process. They are especially important for the usability of polyvinyl chloride (PVC), the third most widely used plastic.
The dominance of ortho-phthalate esters as plasticizers has decreased due to regulatory issues and concerns. In Europe, the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) regulation has restricted the use of low molecular weight plasticizers. The European Union (EU)'s Chemicals Regulation, REACH, prohibited the use of bis(2-ethylhexyl) phthalate (DEHP) in 2015 unless authorization was granted. Additionally, benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), and di-iso-butyl phthalate (DiBP) have been added to the EU REACH Authorization List.
The presence of hazardous substances in PVC products has been a cause for concern, especially in the building and construction sector, a major user of PVC. A study found that 16% of new flooring samples from the Swiss market contained regulated chemicals, mainly lead and DEHP, likely due to the use of recycled PVC. This highlights the need to accelerate the phase-out of hazardous substances and increase transparency in the chemical compositions of plastics to protect human and ecosystem health.
To address these safety concerns, organizations like the European Stabilizer Producers Association (ESPA) are prioritizing the development of PVC stabilizers that do not contain substances of high concern. ESPA has created tools to assist in stabilizer product development, aiming for sustainable production and alternative assessment. Additionally, risk assessment studies on plasticizers are being conducted by universities and organizations like the United States Environmental Protection Agency (EPA) to evaluate their potential health impacts.
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Frequently asked questions
A plasticizer is a low-volatility liquid or solid substance that is added to a raw polymer to improve its flexibility, make it easier to shape and mold, and reduce friction on its surface.
Some examples of plasticizers used in PVC include phthalates, fatty acid esters, DIHP, DOP (DEHP), DINP, DIDP, and chlorinated paraffin oils.
Plasticizers are added to PVC to make it softer and more flexible, increase its plasticity, decrease its viscosity, and reduce friction during handling and manufacturing. They also help to improve the workability and flow of the polymer, making it easier to process and shape into the final product.
