Plasticizer

Plasticizers (UK: plasticisers) or dispersants are additives that increase the plasticity or decrease the viscosity of a material. These are the substances which are added in order to alter their physical properties. These are either liquids with low volatility or solids. They decrease the attraction between polymer chains to make them more flexible. Over the last 60 years more than 30,000 different substances have been evaluated for their plasticizing properties. Of these, only a small number – approximately 50 – are today in commercial use. The dominant applications are for plastics, especially polyvinyl chloride (PVC). The properties of other materials may also be modified when blended with plasticizers including concrete, clays, and related products. According to 2014 data, the total global market for plasticizers was 8.4 million metric tonnes including 1.3 million metric tonnes in Europe. Plasticizers (UK: plasticisers) or dispersants are additives that increase the plasticity or decrease the viscosity of a material. These are the substances which are added in order to alter their physical properties. These are either liquids with low volatility or solids. They decrease the attraction between polymer chains to make them more flexible. Over the last 60 years more than 30,000 different substances have been evaluated for their plasticizing properties. Of these, only a small number – approximately 50 – are today in commercial use. The dominant applications are for plastics, especially polyvinyl chloride (PVC). The properties of other materials may also be modified when blended with plasticizers including concrete, clays, and related products. According to 2014 data, the total global market for plasticizers was 8.4 million metric tonnes including 1.3 million metric tonnes in Europe. Plasticizers for plastics are additives, most commonly phthalate esters in PVC applications. Almost 90% of plasticizers are used in PVC, giving this material improved flexibility and durability. The majority is used in films and cables. It was commonly thought that plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing the 'free volume'), or swelling them and thus significantly lowering the glass transition temperature for the plastic and making it softer; however it was later shown that the free volume explanation could not account for all of the effects of plasticization. For plastics such as PVC, the more plasticizer added, the lower their cold flex temperature will be. Plastic items containing plasticizers can exhibit improved flexibility and durability. Plasticizers can become available for exposure due to migration and abrasion of the plastic since they are not bound to the polymer matrix. The 'new car smell' is often attributed to plasticizers or their degradation products. However, multiple studies on the makeup of the smell do not find phthalates in appreciable amounts, likely due to their extremely low volatility and vapor pressure. Plasticizers make it possible to achieve improved compound processing characteristics, while also providing flexibility in the end-use product. Ester plasticizers are selected based upon cost-performance evaluation. The rubber compounder must evaluate ester plasticizers for compatibility, processibility, permanence and other performance properties. The wide variety of ester chemistries that are in production include sebacates, adipates, terephthalates, dibenzoates, gluterates, phthalates, azelates, and other specialty blends. This broad product line provides an array of performance benefits required for the many elastomer applications such as tubing and hose products, flooring, wall-coverings, seals and gaskets, belts, wire and cable, and print rolls. Low to high polarity esters provide utility in a wide range of elastomers including nitrile, polychloroprene, EPDM, chlorinated polyethylene, and epichlorohydrin. Plasticizer-elastomer interaction is governed by many factors such as solubility parameter, molecular weight, and chemical structure. Compatibility and performance attributes are key factors in developing a rubber formulation for a particular application. Plasticizers also function as softeners, extenders, and lubricants, and play a significant role in rubber manufacturing. Antiplasticizers exhibit effects that are similar, but sometimes opposite, to those of plasticizers on polymer systems. The effect of plasticizers on elastic modulus is dependent on both temperature and plasticizer concentration. Below a certain concentration, referred to as the crossover concentration, a plasticizer can increase the modulus of a material. The material's glass transition temperature will decrease however, at all concentrations. In addition to a crossover concentration a crossover temperature exists. Below the crossover temperature the plasticizer will also increase the modulus. Antiplasticizers are any small molecule or oligomer additive which increases the modulus while decreasing the glass transition temperature. Plasticizers used in PVC and other plastics are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. These compounds are selected on the basis of many critieria including low toxicity, compatibility with the host material, nonvolatility, and expense. Phthalate esters of straight-chain and branched-chain alkyl alcohols meet these specifications and are common plasticizers. Ortho-phthalate esters have traditionally been the most dominant plasticizers, but regulatory concerns have led to the move away from classified substances to non-classified which includes high molecular weight ortho-phthalates and other plasticisers, especially in Europe. In the concrete technology, plasticizers and superplasticizers are also called high range water reducers. When added to concrete mixtures, they confer a number of properties including improve workability and strength. Unless the mix is 'starved' of water, the strength of concrete is inversely proportional to the amount of water added, i.e., the water-cement (w/c) ratio. In order to produce stronger concrete, less water is added (without 'starving' the mix), which makes the concrete mixture less workable and difficult to mix, necessitating the use of plasticizers, water reducers, superplasticizers, or dispersants. Plasticizers are also often used when pozzolanic ash is added to concrete to improve strength. This method of mix proportioning is especially popular when producing high-strength concrete and fiber-reinforced concrete. Adding 1-2% plasticizer per unit weight of cement is usually sufficient. Adding an excessive amount of plasticizer will result in excessive segregation of concrete and is not advisable. Depending on the particular chemical used, use of too much plasticizer may result in a retarding effect.