28.12.2013 Views

preface to fifteenth edition

preface to fifteenth edition

preface to fifteenth edition

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

POLYMERS, RUBBERS, FATS, OILS, AND WAXES 10.61<br />

10.4.12 Polysulfide Rubbers<br />

Polysulfide rubbers are prepared as follows:<br />

Cl9R9Cl Na9S9S9S9S9Na : HS[9R9S9S9S9S9] n R9SH<br />

where R can be<br />

9CH 2 CH 2 9, 9CH 2 CH 2 9O9CH 2 CH 2 9,<br />

or 9CH 2 CH 2 9O9CH 2 9O9CH 2 CH 2 9.<br />

Polysulfide rubbers possess excellent resistance <strong>to</strong> weathering and oils and have very good electrical<br />

properties.<br />

10.4.13 Poly(vinyl Chloride) (PVC)<br />

Poly(vinyl chloride) as previously discussed in Sec. 10.3, Formulas and Key Properties ofPlastic<br />

Materials, has the following structures:<br />

PVC polymer plus special plasticizers are used <strong>to</strong> produce flexible tubing which has good chemical<br />

resistance.<br />

10.4.14 Silicone Rubbers<br />

Silicone rubbers are prepared as follows:<br />

Other groups may replace the methyl groups.<br />

Silicone rubbers have excellent ozone and weathering resistance, good electrical properties, and<br />

good adhesion <strong>to</strong> metal.<br />

10.4.15 Styrene-Butadiene Rubber (GRS, SBR, Buna S)<br />

Styrene-butadiene rubber is prepared from the free-radical copolymerization of one part by weight<br />

ofstyrene and three parts by weight of1,3-butadiene. The butadiene is incorporated by both 1,4-<br />

addition (80%) and 1,2-addition (20%). The configuration around the double bond ofthe 1,4-adduct<br />

is about 80% trans. The product is a random copolymer with these general features:

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!