Page 358 - Handbook of Plastics Technologies

PLASTICS ADDITIVES

5.38 CHAPTER 5

5.5.5.5 Polycarbonate. 0.1 to 1.2 percent Ca stearate, stearyl stearate, or montan ester
as mold release.
5.5.5.6 Acetal. 0.5 percent amide wax.
5.5.5.7 Polyethylene Terephthalate. Silica, talc, zeolites, and calcium carbonate for an-
tiblocking.
5.5.5.8 Unsaturated Polyester. Butcher wax, Ca and Zn stearates, fatty amides, lecithin,
vegetable oil, or organic phosphates as mold release agents.

5.5.5.9 Polyurethanes. 0.5 to 2.0 percent polar ester such as montan for mold release.
0.2 to 1.0 percent for calendaring.
5.5.5.10 Nylon. Silica, talc, zeolites, and calcium carbonate for antiblocking.
5.5.5.11 Phenolics. Ca and Zn stearates or fatty amides for mold release.

5.5.5.12 Common Mold Release Agents. Fatty esters and amides, wax, polyethylene,
oxidized polyolefins, PTFE powder, silicones, metal stearates, talc, mica.

5.5.6 Other Processing Aids

5.5.6.1 Acrylics for Rigid PVC. Melt processability of rigid PVC is greatly improved
by addition of several percent of an acrylic processing aid, generally a graft of PMMA
onto a polyacrylic ester such as ethyl or butyl acrylate. Improvements reported include in-
creased friction producing faster fusion, increased melt viscosity, reduced jetting in injec-
tion molding, increased shear producing faster mixing, increased melt strength and
elongation for blow molding and thermoforming, die swell for blow molding, and in-
creased surface gloss. Typical concentrations are 0.5-3.0 percent for injection and blow
molding; 1-5 percent for extrusion, calendering, and thermoforming; and 5-12 percent for
foaming.
5.5.6.2 Branched Polypropylene. This is added to regular polypropylene to produce
high melt strength for blow molding and foam production.

5.5.6.3 Viscosity Depressants. PVC plastisols are made more fluid by 0.5 to 2.0 percent
of ethoxylated fatty esters. Filled plastisols use silanes and titanates.
5.5.6.4 Thixotropes. Latex, plastisols, epoxies, and polyesters are thickened by precipi-
tated or fumed silica as well as clays. Latexes are also thickened by cellulose ethers, Na
CMC, and Na polyacrylate.
5.5.6.5 Surfactants. Foaming of plastisols and polyurethanes is improved and stabilized
by liquid silicones.

5.5.6.6 Emulsifiers. Emulsifiers are used for emulsion polymerization and for com-
pounding additives into polymer latexes. They may be anionics such as sodium soaps, sul-
fonates, sulfates, and phosphated organic molecules; cationics such as quaternary
ammonium organics; or nonioncs, generally polyethoxylated organic acids and alcohols.
Anionics and nonionics are often used together, anionics for more powerful emulsification
and nonionics for resistance to acid and hard water.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.