Polymeric Plasticisers

Polymeric plasticisers have been used as partial or total replacements for di(2-ethylhexyl)adipate (DEHA) in PVC cling film to reduce levels of plasticiser migration when used for food contact. Castle et al. [792] used SEC in combination with H 1-NMR and MS for the isolation and identification of seven individual oligomers in the most commonly employed polymeric plasticiser, poly(butylene adipate) (Reoplex R346). Both mass (RI) and specific ester moiety (UV) were being monitored (Figure 4.21). The oligomers were identified... 

Figure 4.21 High-performance size-exclusion chromatograms of the polymeric plasticiser Reoplex R346 using (a) RI and (b) UV detection. After Castle et al. [792]. Reproduced from L. Castle et al., Food Addit. Contain., 8, 565-576 (1991), by permission of Taylor Francis Ltd (http //www.tandf.co.uk/journals)...

The use of IR spectroscopy for the identification of plasticisers was discussed in Section 2.4. Separation by SEC is often required to confirm the use of polymeric plasticisers. Most of the common plasticisers for plastic materials can be detected and analysed either by GC-MS or LC-MS. Complex plasticisers such as epoxidised soya bean oil can be fully characterised by LC-MS using chromatography in hexane/propionitrile with detection by positive ion APCI. 

The most common plasticiser used in this application is di-2-ethylhexyl adipate (DEHA), in combination with polymeric plasticisers and epoxidised soya bean oil. 

For applications requiring high temperature and extraction resistance, polymeric esters are used (88). New polymeric plasticisers are in development (87) including adipate based for improved low temperature properties (103). Plastisols based on propyleneglycol adipate have been examined (198) and the thermal degradation has been determined using dynamic and isothermal thermogravimetric analysis (188). 

The heat stabilising action of polymeric plasticisers has also been investigated (181, 223). 

Printing on vinyl surfaces can be problematic due to the influence of the formulation ingredients, particularly heat stabilisers and lubricants, on print adhesion. Spectroscopic analysis of PVC-P films has identified the formation of a barium zinc stearate complex which formed in the PVC matrix and migrated to the surface (207). Polymeric plasticisers have been developed to increase the surface energy, and so improve print adhesion. The incorporation of stearic acid had a surface energy reducing effect when used with the polymeric plasticiser (193). 

Polymeric plasticisers are an important part of the total plasticiser market and are used primarily in speciality... 

The behaviour of an adipic acid-based polymeric plasticiser for poly(vinyl chloride)s, developed to give improved low temperature flexibility, was compared with that of a conventional adipate plasticiser of the same molecular weight. Blends containing 50 phr plasticiser were prepared. The new plasticiser exhibited a similar softening efficiency and permanence whilst improving the glass transition and brittle temperatures (3-4 C lower). The dry blend time was reduced by 10%. The viscosity of the new plasticiser was 25% lower than that of comparable conventional adipates. 1 ref. 

Macromolecular Symposia Vol. 176, Nov. 2001, p.39-48 STABILISING ACTION OF POLYMERIC PLASTICISERS IN PVC... 

Thermal degradation and degradation kinetics of polyvinyl chloride (PVC) plastisols, plasticised by polymeric plasticiser, were examined using dynamic and... 

Based on low-toxicity polymeric plasticisers, new formulations of PVC plastisols were proposed and characterised. The study used propyleneglycol adipate as the polymeric plasticiser and compared its properties with two conventional phthalates DEHP and DINP. Mechanical and optical properties were examined, together with the determination of the optimum processing conditions for the higher viscosity plastisols using the polymeric plasticiser. 21 refs. 

Many polymeric plasticisers, impact modifies, and processing aids for PVC are incorporated into the PVC by mechanical mixing Many of these, including butadiene-acrylonitrile copolymers, ethylene-vinyl acetate copolymers chlori-... 

Plasticised PVC may sometimes seem a misnomer, as the plasticiser content can occasionally be greater than the PVC. Plasticisation also reduces chemical resistance and increases gas and moisture permeation. Typical plasticisers used include adipates, citrates, sebacates, phosphates and phthalates, e.g. di-iso-octyl adipate, acetyl-tri-n butylcitrate, di-octyl phthalate (DOP). Polymeric plasticisers and urethanes are also used. Plasticised PVCs are soft and very flexible (see IV bag usage). 

There are various ways of reducing the rate at which plasticiser leaches into the body. The higher molecular weight polymeric plasticisers, such as poly 1,3 butylene adipate (PBA) are less mobile in the PVC. When DEHP is replaced by PBA in plasticiser blends, the amount extracted by kerosene at room temperature in 24 h reduces more than tenfold (Fig. 15.9). 

Plasticisers Polymeric plasticisers - usually polyesters, based on adipic acid are preferred for food contact applications - which have very low level of migration. 

The release of low molecular weight plasticizer has resulted in polymeric plasticisers being developed, but esters are still widely used and are effective in plasticisation. (Black, 1992 Brydson, 1982, and Park and Lakes, 1992). 

Polymeric plasticisers are resistant to leaching and migration. Common examples include polypropylene glycol adipate and sebacate, but there are also polymeric phthalates. Polymeric adipates are recommended for instrument panels, upholstery, roofing and clothing. 

Polymeric plasticisers such as polypropylene adipate, azelate, glutarate and sebacate (or mixtures of these substances) are much less volatile than ordinary low molecular weight plasticisers. They are not easily extracted, and they weather well, but they cost more than phthalates and are not as easily processed, being mostly high viscosity substances. They are often blended with phthalates as a compromise. The polyester adipates are the most widely used. 

Polymeric plasticiser sales are believed to be roughly 20,000 tonnes/year in Europe. 

PMMA and polyvinylidene fluoride (PVDF) form miscible blends in which PMMA acts as a polymeric plasticiser when added in low amounts. PMMA improves processing and both PMMA and PVDF are resistant to ultraviolet degradation. Applications include weatherable film [37-41]. 

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