Plasticizers are substances which, by virtue of their polar or polarizable structure, weaken the secondary valence forces of polymers. By incorporation of plasticizers into compatible polymers, the materials can be modified in such a way that it becomes soft and flexible, even at sub-zero temperatures. The degree of flexibility attainable depends on the type and quantity of plasticizer used. Among the most firmly established plasticizers are esters of aromatic and aliphatic monocarboxylic and aliphatic dicarboxylic acids, sulfonic acid and phosphoric acids.
In practice a plasticizer is expected to combine as many as possible of the following properties:
- Satisfactory compatibility with the polymer
- High plasticizing capacity
- Adequate thermal stability and saponification resistance
- Low volatility
- Migration and extraction resistance
- Low temperature flexibility
- Fire retardancy
Monomeric and polymericA distinction is made according to the molecular structure between monomeric and polymeric plasticizers. The principal properties of plasticized polymers such as modified mechanical data, low-temperature flexibility and low flammability can be achieved through the use of monomeric plasticizers. If the requirements include low plasticizer migration into other plastics, coatings and adhesives or resistance to extraction by other chemicals, polymeric plasticizers from the Ultramoll® range should be used.
In view of the wide range of demands on articles made from plasticized polymers, the addition of a single plasticizer will not usually suffice, and mixtures of plasticizers have to be employed. In this way an attempt is made to find the best possible compromise between the properties of the plasticizers and the range of practical demand on the polymeric material.
Plasticizers of low viscosity and low polarity have a good plasticizing capacity and can be used over a wide range of temperatures, since their viscosity is less dependent on temperature than that of high-polarity plasticizers. Their viscosity–temperature curve is very flat. These plasticizers with special good resistance to low temperatures are used whenever a plasticized polymer is required to have high flexibility even at sub-zero temperatures. Typical low temperature plasticizers include Adimoll® adipates, Uniplex® sebacates and Disflamoll® TOF.
Compatibility of a plasticizer can be determined fairly quickly and simply by way of the dissolution temperature. A PVC / plasticizer suspension (1:19) is heated. The temperature at which the PVC becomes visible and has dissolved completely is known as the dissolution temperature. As a universal rule, the lower this temperature is, the more compatible is the plasticizer. Mesamoll® has a low dissolution temperature of about 120 degree C and is an efficient primary and secondary plasticizer for PVC. In addition, Mesamoll® is a versatile plasticizer demonstrated by divers usability, including PUR sealants and adhesives, in acrylates for metal coatings and in NBR rubbers. The saponification resistance of Mesamoll® allows our customers to produce products with a long service life.
Many applications for plasticized polymers demand good fire performance. These include PVC cable, coating, flooring, materials used in the mining industry, PVC/NBR insulation foams, thermoplastic polyurethanes and thermosets like PF. Of all the common plasticizers only the phosphoric esters are fire-retardant, the aromatic Disflamoll® DPK and TKP and Reofos® more so than the aliphatic Disflamoll® DPO and TOF. The fire retardant properties can be further improved by the addition inorganic fire-retardants. If other plasticizers with no fire retardant properties are used alongside fire retardant plasticizers, the fire performance of the polymer compound is invariably impaired.
Some plasticizers develop a high potential regarding scope of use, but they are designed for a specific use. Unimoll® AGF, our largely bio based plasticizer, was developed for the use in articles intended to come into contact with foodstuffs. Our Uniplex Benzoates are mainly solid special plasticizers used in hot-melt adhesive & equipment cleaning. Uniplex 214 is the sulfonamide plasticizer for commodity polyamides in the applications hydraulic tubings, fuel lines and monofilament fibers.