Functions of Plasticizers

Brings down the viscosity of a liquid polymer. Also, lowers the melt viscosity of a thermoplastic polymer. Thus it improves the workability and enhances the loading capability of a polymer with explosives, fillers or oxidizers. This is of special interest in the field of explosives or propellants where the amount of an explosive or oxidizer ingredient considerably increases leading to improvement in their performance. 

Also brings down modulus and tensile strength and as a result, increases elongation which improves the low temperature characteristics. This may also lower Tg of the polymer or resin and thus facilitates their processing at a lower temperature. Some aliphatic dicarboxylic acid esters such as bis (2-ethyl hexyl) adipates, sebacates, azelates, etc. are most effective for this purpose. 

Sometimes, addition of plasticizer imparts flame retardant characteristics in addition to other properties. Phosphate esters such as tris(2-ethyl hexyl) phosphate (TOP), tricresyl phosphate (TCP), chlorinated paraffin hydrocarbons etc. impart excellent flame retardant characteristics to many polymers. 

but the most important is improvement in terms of safety, that is, processing of the explosive or propellant formulations becomes safer. 

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The initial strain hardening rate (df/dy)o is given as a function of plastic strain rate for strain rates up to 10 s (which includes shock compression to 5.4 GPa) as [38]... 

Slope AB = function of elastic deformation Slopes BC and DE = function of plastic deformation and brittle fracture... 

Figure 4. Crystalline melting points (Tm) and glass transition temperatures (T0) of plasticized polycarbonate as a function of plasticizer content...

Liquid chlorinated paraffins are the main halogen-containing fire-retardant additives used for poly(vinyl chloride) often in combination with a phosphate ester. In this case, the chlorinated paraffins have the secondary function of plasticizers. The thermal degradation mechanism of chlorinated paraffins is similar to that of poly(vinyl chloride), so in this case poly(vinyl chloride) stabilizers have also the secondary function to stabilize chlorinated paraffins. 

The effects of plasticizers has also been studied by PAL [64, 65]. The addition of a plasticizer to polymers generally has the effect of lowering the Tg, however in some cases an anti-plasticization can occur. Borek et al [65] have shown that the fraction of free volume in PVC polymers could be fit with a fourth order polynomial as a function of plasticizer concentration. The decrease in th Tg with increasing amount of plasticizer is attributed to this increase in the free volume of the polymers. 

Fig. 2. Variations of temperature rise as function of plastic strain and strain rate.

Table 1 Glass transition temperature (Tg) of Eudragit RS 30 D polymeric films as a function of plasticizer type and concentration...

The fineness of the clay with reference to its finest particles, i.e., grains of the magnitude of 0.01 to 0.003 mm., is indicative in general of the content of the dispersed or colloidal portion, but is not necessarily a function of plasticity. Plasticity, therefore, is not merely a matter of fineness. The apparent specific gravity of the dried clay is sometimes useful in comparing different materials. 

Spin-lattice relaxation has been studied by Cu NMR for dilute Cu-Mn and Cu-Cr alloys at temperatures of 0.32-20K while the NMR lines in deformed Cu alloys with Si, A1 and Ga were investigated as a function of plastic deformation. Variations in Cu Knight shifts in Cu-Zn alloys have been reported. Spectra from NMR experiments performed on binary Cu-Au ordered alloys and martensitic ternary Au-Cu-Zn alloys in order to study crystallographic Cu sites microscopically have revealed different distributions of Cu atoms that change appreciably with Cu content. 

Chloroparaffines are used, for instance, in coolants and lubricants in the metalworking industry and as additives in paints, plastics and rubber. They fulfil the function of plasticizer and flame retardant. 

FIGURE 6.3 Hardness as a function of plasticizer concentration (% DOP) for different percentages of snlfnr in rnbber samples. (Reproduced with permission from Rubber Chemistry and Technology, Copyright 1982. 55 328-36. A. Accetta and J. M. Vergnaud, Figure 8,... 

Vane shear test correction factor as a function of plasticity index. (From Bjerrum, L., Embankments on soft ground. Proceedings on Performance of Earth Supported Structures, American Society of Civil Engineers, 11, 1-54, 1972. Reprinted with permission of ASCE.)... 

The variation of P as a function of plasticity index is shown in Figure 4.24. 

The efficiency of separation (Ep) in dense-medium baths was found to depend on the plastic viscosity of the media, and a high yield stress (to) of the medium is claimed to cause elutriation of the finer particles into the float as they (and near-density particles) are unable to overcome the threshold shear stress required before the movement takes place. When a particle is held in a suspension, the yield stress is responsible for it but when it is moving, its velocity is a function of plastic viscosity. It is understandable then that dispersing agents used to decrease medium viscosity may improve separation efficiency quite significantly. They may also decrease mag-nitite loses. 

Roe, D., Karandikar, B., Bonn-Savage, N., Gibbins, B., Roullet, J.B., 2008. Antimicrobial surface functionalization of plastic catheters by silver nanoparticies. J. Antimicrob. 

Therefore, in order to produce plastic moulding compounds with reasonable melt flow characteristics, as a rule, 15 to 35% plasticizer is added for CA and 3 to 25% for CAP and CAB [22]. In Figure 3.11 the melt flow index (MFI), as a measure of melt viscosity, is shown for typical cellulose ester moulding compounds as a function of plasticizer content. Obviously, as expected, the esters with longer side chains are more flexible and need considerably less plasticizer than the shorter chain esters to reach the same flowability at a given temperature. 

Figure 3.11 Melt flow index of cellulose ester moulding compounds as a function of plasticizer content. (Data calculated from ref 122].)...

Table G. Polysulfide Elongation at Break as a Function of Plasticizer Lever...

Two processes may potentially take place in the presence of plasticizers increased mobility may induce crystallization or the solvating power of the plasticizer may affect crystalline phase or interfere with crystallization. Before these two potential results are discussed the effect of the plasticizer on chain mobility is reviewed. Figure 10.55 shows that the glass transition temperature of plasticized PVC is a linear function of plasticizer concentration. Figure 10.56 shows that introduction of the plasticizer increases a free volume. Figure 10.57 shows that the free volume linearly increases in plasticized polyethylene oxide. " These three graphs are characteristic of the main functions of plasticizers which are to make polymers more elastic and increase their tolerance to lowering the temperature. In fact, addition of the plasticizer and temperature increase have a very similar effect on the resultant flexibility and mobility of chain (plasticization and plastification, respectively). 

MAIN FUNCTIONS PERFORMED BY PLASTICIZERS A short list of the functions of plasticizers in epoxy resins includes ... 

Figure 11.36 shows that the glass transition depression is a linear function of plasticizer concentration. Two ester plasticizers depress the glass transition temperature more extensively than paraffinic oil. Dioctyl sebacate deerease the flexural modulus more rapidly with smaller concentrations of plasticizer (up 10 wt%) then the flexural modulus levels... 

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