Plasticisers

We have been using plasticisers to make things soft and bendable for thousands of years. Water has been used to soften clay since the early evolution of man and oils are known to have been used centuries ago to plasticise pitch for waterproofing boats.

Modern plasticisers are not different. They are substances which when combined with PVC and other polymers create a whole new world of physical properties for high performing applications and uses that bring a myriad of benefits to everyday life. Today, over 90 percent of all plasticisers consumed in  Europe are employed in flexible PVC applications, largely for the construction, automotive and wire & cable  sectors.   

Globally, approximately six million tonnes of plasticisers are consumed every year, of which European consumption accounts for approximately 1 million tonnes. In relation to phthalates, the European plasticiser market has gradually shifted towards high molecular weight phthalates (high phthalates), which today represent just over 80 percent of all plasticisers consumed  in Europe.  

Plasticisers are colourless and odorless liquids that cannot be simply treated as additives like pigments or fillers. They are, in fact, major functional additives that determine and improve the physical properties of polyvinyl chloride (PVC).

Typically, these plasticisers are esters that have low vapour pressure and good heat stability. Most of them are chemically inert. There have been over 10,000 esters suggested, with over 300 different commercial launches, of which 50 to 100 are in commercial use. They can be divided in two wide application categories, based on their performance features:

• General purpose plasticisers are suited to a very wide range of applications and processing techniques where they bring an optimised balance between cost, versatility and performance.

• Specialty plasticisers impart one or more special properties that cannot be obtained by the use of a general purpose plasticiser alone. They are suited to a narrow range of applications and are produced in smaller quantities than general purpose plasticisers.

Phthalates: Not all phthalates are the same

Phthalates (pronounced THAL-ates) are the most commonly used plasticisers in the world. In Europe, about one million tonnes of phthalates are produced each year, of which approximately 93% are used to make polyvinyl chloride (PVC) soft and flexible. They can be found in a range of everyday items including electrical cables, hoses, flooring, wallcoverings, coated textiles, luggage, sports equipments, roofing membranes, pool liners, footwear as well as life saving medical devices such as tubing and blood bags. In addition, some phthalates are used in non-PVC applications such as coatings, rubber products, adhesives and sealants.

Phthalates are manufactured by reacting phthalic anhydride with alcohol(s)  which range from methanol and ethanol (C1/C2) up to tridecyl alcohol (C13), either as a straight chain or with some branching. They are divided into two distinct groups, with very different applications, toxicological properties and classification, based on the number of carbon atoms in their alcohol chain. High molecular weight (HMW) or high phthalates include those with more than 6 carbons in their backbone, which gives them increased permanency and durability. Low molecular weight (LMW) or low phthalates are those with only 3-6 carbon atoms in their backbone.

Due to their widespread use, phthalates have undergone extensive testing for possible health and environmental effects and are thus amongst the most widely researched of all chemical substances. In Europe, the European Commission, the European Chemicals Agency (ECHA) and EU Member States have undertaken 10-year-long comprehensive scientific assessments of both high and low phthalates under the EU Risk Assessment Regulation.

• High phthalates (DINP, DIDP, DPHP, DIUP, and DTDP) represent just over 80% of all the phthalates currently being produced in Europe. Risk assessments have shown positive results regarding the safe use of this group of substances. They all have been registered for REACH and do not require any classification for health and environmental effects, nor are they on the Candidate List for Authorisation.

• Low phthalates (DEHP, DBP, DIBP and BBP)  represent about 10% of the European market. Risk assessments have led to their classification and labelling as Category 1B Reproductive agents. They have been registered under REACH but are included in the EU Candidate List based on their hazard classification and will therefore have to go through the REACH Authorisation process.These plasticisers will be phased out by the EU by February 2015 unless an application for authorisation is made before July 2013 and an authorisation granted.

Click here to see a list with the structural formula an CAS No. of the most common phthalates.

Typically, phthalates with one or two carbons in their backbone are used as solvents in non-PVC applications. Their very high volatility make them unsuitable for flexible PVC applications.

C4 to C6 phthalates(Low Phthalates) with 3 to 6 carbon atoms in their backbone are used in applications where high solvating plasticisers  and stain resistance are required (for example, foamed leather cloth and flooring).

C9 to C10 phthalates (High Phthalates) with over 6 carbon atoms in their backbone are the most widely used general purpose plasticisers and are used for applications such as wire & cables, geomembranes, roofing membranes, truck tarpaulins, coated fabrics, wallcovering and flooring.

C11 to C13 phthalates are used where high temperature performance or low fogging  is required, typically used in car interior or in automotive cables.