PLASTICISER

Plasticisers are known for their effectiveness in producing flexible polymers such as flexible PVC, acrylate copolymers and so on. Plasticisers are normally liquids, and are used in glassy polymers to reduce their glass transition temperature (Tg) with compatibility to avoid phase separation. Phase separation would cause migration to the surface. The rubbery effect results from the high levels of plasticiser bringing the Tg of the polymer to below room temperature. In semi-crystalline polymers, plasticisers would not only reduce the Tg of the amorphous domain but also decrease the melting point of the crystalline phase. 

The application fields of plasticisers range from automobiles and construction to toys and medical products. Phthalate plasticisers such as dibutyl phthalate and di(2-ethylhexyl) phthalate are widely used due to the higher plasticising efficiency and lower volatility of these phthalate plasticisers. Phthalate plasticisers are still widely used in the processing of flexible PVC [29]. However, recently, the use of phthalate plasticisers has been questioned due to their debatable toxicity in consumer products made of PVC matrices, especially in blood supply and similar medical plastics, because the content of 

Eco-friendly and non-toxic phthalate plasticisers, such as hiodegradahle trihutyl citrate, triethyl citrate, acetyltrihutyl citrate, acetyltriethyl citrate and tri(2-ethylhexyl) citrate, have been widely used in the food and medical packaging fields [33-37]. 

Plasticisers act under the same phenomenon as solvents, increasing the free volume of the polymer but without producing complete dissolution. Both are governed by the same laws of solubility. However, each plays a different role. While solvents serve mostly as viscosity modifiers, plasticisers modify the curing properties of the sealant, softening and lowering the glass transition temperature. Common plasticisers in polyurethane sealants are  

Plastic products are prepared by addition of plasticisers. Esters of phthalic, of phosphoric and of aliphatic dicarboxyhc acids, epoxides and some high molecular weight compounds are especially suitable. Since some of these substances are highly toxic, a sensitive chemical method of detection was desirable. GC analysis is rendered difficult by the high boiling points of the plasticisers but identification with the help of TLC is most successful. Plasticisers authorised in the USA for use in plastic package 

Solvents I Isooctan -ethyl acetate (90 + 10) (95 + 5) III Dibutyl ether-hexane (80 + 20). II Benzene-ethyl acetate  

Also using silica gel G layers, Bbaun [4, 5] has separated numerous plasticisers with methylene dichloride, after they had been extracted from the plastic material with benzene or ether (provided the polymer itself was not soluble). Antimony(V)chloride (Rgt. No. 18) is a generally applicable spray reagent it yields brown spots with most of the plasticisers after the plate is heated to 120° C. Phthalate esters can be detected in addition with resorcinol solution (Rgt. No. 218) and phosphate esters with a diazonium salt reagent (No, 238). 

As can be seen from the hjR/-values, plasticisers of low molecular weight are more easily separated than esters of longer-chain alcohols. 

Ester plasticisers can be directly analysed or acid and alcohol (or phenol) products of saponification may be detected by TLC. 

This section will focus on the environmental debate around PVC. Recycling and sustainability issues will be reviewed in Section 7. 

Members of the European Council of Vinyl Manufacturers (ECVM), who account for 98% of production in the EU, have signed charters covering the production of VCM, S-PVC and E-PVC. This covers environmental standards for limits on emissions to air and discharges to water of VCM, EDC, HC1, ethylene, dioxin-like components and copper. VCM concentration in PVC is also strictly controlled (particularly for food/medical applications) (126). 

Subject to external audit, the industry has agreed to work towards these limits from 1998 for VCM and S-PVC, and 2003 for E-PVC. 

For a material to act as a plasticiser it must conform to the following requirements  

The solubility parameters of a number of commercial plasticisers are given in Table 5.7 

From Table 5.7 it will be seen that plasticisers for PVC such as the octyl phthalates, tritolyl phosphate and dioctyl sebacate have solubility parameters within 1 cgs unit of that of the polymer. Dimethyl phthalate and the paraffinic oils which are not PVC plasticisers fall outside the range. It will be noted that tritolyl phosphate which gels the most rapidly with PVC has the closest solubility parameter to the polymer. The sebacates which gel more slowly but give products which are flexible at lower temperatures than corresponding formulations from tritolyl phosphate have a lower solubility parameter. It is, however, likely that any difference in the effects of phthalate, phosphate and sebacate plasticisers in 

Data obtained by Small s method expect for that of Saniicizec 8 which was estimated from boiling point measurements. 

PVC is due more to differences in hydrogen bonding or some other specific interaction. It has been shown by Small that the interaction of plasticiser and PVC is greatest with the phosphate and lowest with the sebacate. 

External lubricants are used to reduce the friction between the polymer and the surface of the extruding equipment. To function effectively these should be not too soluble in the plastic in order to enhance the concentration of lubricant at the surface. The most commonly used external lubricant is calcium stearate added at the 0.05 to 0.3% level. 

In extrusion - blow moulding operations, molten polymer passes through a stage where it is processed with little external support. In these circumstances the moulding is likely to distort. The incorporation of a melt strength additive reduces the possibility of this occuring. Frequently, the materials used to improve melt strength are the same as those used for internal lubrication or plasticisation. 

These are used to coat the mould in order to reduce the possibility that the moulded article will stick. Silicones are usually used for this purpose now, although paraffin oil or petroleum jelly are still used to a small extent. 

Some important plasticisers include di-2-ethylhexyl phthalate used in PVC formulations, dipentyl phthalate, di-(2-ethyl hexyl) adipate di-octyladipate, diethyl phthalates, diisobutylphthalate and di-n-butyl phthalate used in polyethylene. Polymeric plasticisers include poly(l,2-propylene adipate) and polybutylene succinate. 

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In the case of poly(vinyl chloride) plastics, the FWA is mixed dry with the PVC powder before processing or dissolved in the plasticising agent (see Vinyl polymers). Polystyrene, acrylonitrile—butadiene—styrene (ABS), and polyolefin granulates are powdered with FWA prior to extmsion (2,78) (see... 

C. D. Craver, Infra Red Spectra of Plasticisers and Other Additives, 2nd ed.. The Coblent2 Society, Kirkwood, Mo., 1980. 

PET does not crystallise well in the unoriented state even in a hot mold unless nucleating agents and/or plasticisers are added. Commercial PET ... 

PVC. Poly(vinyl chloride) (PVC), a very versatile polymer, is manufactured by the polymerisation of vinyl chloride monomer, a gaseous substance obtained from the reaction of ethylene with oxygen and hydrochloric acid. In its most basic form, the resin is a relatively hard material that requites the addition of other compounds, commonly plasticisers and stabilisers as well as certain other ingredients, to produce the desired physical properties for roofing use. The membranes come in both reinforced and nonreinforced constmctions, but since the 1980s the direction has been toward offering only reinforced membranes. The membrane thickness typically mns from 0.8—1.5 mm and widths typically in the range of 1.5—4.6 m. 

N. A. J. Plat2er, Plasticicyation and Plasticiser Processes, American Chemical Society, Washington, D.C., 1965. 

D. F. Cadogan, Plasticisers N Consideration of Their Impact on Health and the Environment, Plasticizers Sector Group, CEFIC, Brussels, Belgium, 1992. 

The majority (92% in 1988) of the butyraldehyde produced in the United States is converted into 1-butanol and 2-ethyIhexanol (2-EH). 2-EH is most widely used as the di(2-ethylhexyl) phthalate [117-81-7] ester for the plasticisation of flexible PVC. Other uses for 2-EH include production of intermediates for acryflc surface coatings, diesel fuel, and lube oil additives (24). 

Type AD-G is used in an entirely different sort of formulation. The polymer is designed for graft polymerisation with methyl methacrylate. Typically, equal amounts of AD-G and methyl methacrylate are dissolved together in toluene, and the reaction driven to completion with a free-radical catalyst, such as bensoyl peroxide. The graft polymer is usually mixed with an isocyanate just prior to use. It is not normally compounded with resin. The resulting adhesive has very good adhesion to plasticised vinyl, EVA sponge, thermoplastic mbber, and other difficult to bond substrates, and is of particular importance to the shoe industry (42,43). 

Non-ionic surfactants used in detergents, paints, herbicides, pesticides and plastics. Breakdown products, such as nonylphenol and octylphenol, are found in sewage and industrial efffuents Products of combustion of many materials Widely used as plasticisers for PVC. Common environmental pollutants... 

However, not all EDs with a high log possess or require the ability to bioaccnmulate in order to be biologically active. For example, phthalate plasticisers, chlorophenols from Kraft mill effluents and natural or synthetic hormones can influence an organism s hormone profile and affect reproductive function and immune response without exhibiting bioaccnmiilation. ... 

Architectural uses (window frames, etc.). Plasticised to moke artificial leather, hoses, clothing. 

In summary, then, design with polymers requires special attention to time-dependent effects, large elastic deformation and the effects of temperature, even close to room temperature. Room temperature data for the generic polymers are presented in Table 21.5. As emphasised already, they are approximate, suitable only for the first step of the design project. For the next step you should consult books (see Further reading), and when the choice has narrowed to one or a few candidates, data for them should be sought from manufacturers data sheets, or from your own tests. Many polymers contain additives - plasticisers, fillers, colourants - which change the mechanical properties. Manufacturers will identify the polymers they sell, but will rarely disclose their... 

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