Page 330 - Handbook of Plastics Technologies

PLASTICS ADDITIVES

5.10 CHAPTER 5

TABLE 5.7 Synergistic Stabilization of PVC: Gardner
Color After Aging in 150°C Oven
Aging time, minutes 0 50 200

1 percent barium laurate 1 13 14
1 percent cadmium laurate 1 3 3
1 percent zinc laurate 1 18 18
5 percent epoxidized soybean oil 2 10 13
1 percent alkyl diaryl phosphite 1 17 18
All five together 1 1 2

sometimes is octyl for food packaging or methyl for higher efficiency. The most powerful
X group is –SCH CO C H , which is called isooctyl thioglycollate or isooctyl mercap-
2 8 17
2
toacetate. For greater lubricity or UV stability, the X group may be maleate or laurate
(Table 5.8). The relative amounts of R and X are sometimes varied for subtle reasons. In
rigid PVC, where high melting point and high viscosity cause the most serious instability
problems, organotin is always used. Concentrations range from 2 to 3 percent down to one
tenth as much, depending on the equipment and process.
TABLE 5.8 Organotin Stabilization of PVC: Gardner
Color After Aging in 175°C Oven
Aging time, minutes 30 60
Unstabilized 13 15

3% dibutyl tin dilaurate 2 5
3% dibutyl tin maleate 2 3
3% dioctyl tin bis-octylthioacetate 1 2
3% dibutyl tin bis-octylthioacetate 1 2
3% dimethyl tin bis-octylthioacetate 1 1

5.1.3.4 Miscellaneous Stabilizers. A variety of other stabilizers are vaguely mentioned
in the literature, mainly by vendors. Polyols and organo-nitrogen compounds may be
added to complex iron impurities in fillers and keep them from catalyzing degradation of
PVC. Other additives are more secretive and their benefits less clear. Bisphenol is added to
wire and cable insulation to stabilize the plasticizer rather than the PVC. UV stabilizers
may be added for outdoor use, and biostabilizers are important to protect the plasticizer.
5.1.3.5 Other Organohalogens. Thermal instability is also a problem in other polymers
such as chlorinated polyethylene, chlorinated PVC, polyvinylidene chloride, chlorinated
rubber, and chlorinated and brominated flame-retardants. PVC heat stabilizers may help
here, too, but require careful adjustment for optimum performance in each system.

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