Page 354 - Handbook of Plastics Technologies

PLASTICS ADDITIVES

5.34 CHAPTER 5

5.4.6 Commercial Practice
5.4.6.1 Polyvinyl Chloride. Polyvinyl chloride is about 85 percent amorphous regions
that can absorb plasticizer and produce flexibility, and 15 percent crystalline regions that
remain firmly bonded and retain strength and creep resistance. This is an ideal balance,
which accounts for the fact that PVC uses about 80 percent of the total plasticizer market.
Most of this is phthalic esters. Di(2-ethylhexyl) phthalate was the first and remains the
leading material, and it is called “general-purpose.” For higher permanence, diisodecyl
and ditridecyl phthalates are common; trimellitates are more permanent but more expen-
sive. Surprisingly, linear alkyl phthalates are superior to branched (isoalkyl) phthalates for
both efficiency and permanence. For still greater permanence, liquid polyesters of MW
1000 to 3000 are used, but they are less efficient and more expensive. For flooring, butyl
benzyl phthalate is used for fast fusion and stain resistance. For low-temperature flexibil-
ity, dioctyl adipate is most common; azelate and sebacate esters are more efficient but
more expensive. For greater flame-retardance, tricresyl phosphate is common, and, for ef-
ficiency as well, trialkyl phosphates are excellent but more expensive. And, of course, for
thermal stabilization synergists, epoxidized soybean and linseed oils and tall oil esters are
standard practice (Sec. 5.1.3.2).

5.4.6.2 Rubber. Rubber is commonly plasticized by hydrocarbon oils from the petro-
chemical industry, particularly to improve melt flow in calendering and extrusion. This
practice rarely finds its way into the technical literature or market analyses.

5.4.6.3 Cellulose Esters. These and ethyl cellulose are rigid plastics that are lightly
plasticized to improve melt processability and to impart some impact resistance and flexi-
bility in sheet form. Lower alkyl phthalates are most common, while phosphates are used
for flame retardance.

5.4.6.4 Ultra-High-Molecular-Weight Polyethylene. This is extremely difficult to pro-
cess. Addition of paraffin wax or low-molecular-weight polyethylene wax permits conven-
tional melt processing.
5.4.6.5 Polystyrene. Polystyrene melt processability is improved by addition of a small
amount of mineral oil or butyl oleate to increase melt flow.
5.4.6.6 Nylon. Nylon’s melting point is reduced by addition of toluene sulfonamide for
use as a laminating adhesive in multilayer textile construction.

5.4.6.7 Market Analysis. See Table 5.28 for a plasticizer market analysis.

TABLE 5.28 Plasticizer Market Analysis

Plasticizer % Plasticizer %
Phthalates 69 Phosphates 3
Epoxy esters 9 Trimellitates 2
Glutarates 4 Azelates 1
Adipates 4 Others 5
Polyesters 3

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