approaching the service limit, strong caustic solutions will cause partial dissolution. PVDF is autoclavable if tanks are empty and externally supported.

B.5 Chemical Resistance Chart

The following table lists a wide variety of chemicals and their effects on a variety of polymers. In addition, several concentrations of a chemical are included if each affects the same polymer differently. Chemicals affect polymers by one (or more) of three different mechanisms:

1. Chemical attack on the polymer chain, with resultant reduction in physical properties, including oxidation, reaction of functional groups in or on the chain, and depolymerization.

2.Physical change in the polymer, including absorption of solvents (resulting in softening and swelling of the plastic), permeation of solvent through the plastic, and dissolution in the solvent.

3.Stress-cracking from the interaction of a "stress-cracking agent,"* with molded-in or external stresses.

Because heat typically enhances chemical reactions, each polymer indicates the compatibility of two temperatures: The first one shows the compatibility at room temperature (20°C) and the second shows the compatibility at an elevated temperature (50°C). Thus, "GN" indicates that at 20°C the polymer is "good" to use, but at 50°C the polymer is "not recommended." The following codes are used in Table B 1:

*Environmental stress-cracking is the failure of plastic materials in the presence of certain chemicals types. This failure is not a result of chemical attack, but rather the simultaneous presence of three factors: tensile stress, a stress-cracking agent, and inherent susceptibility of the plastic to stresscracking.

Table B-l Chemical Resistance Chart (continued)

Table B-l Chemical Resistance Chart (continued)

Table B-l Chemical Resistance Chart (continued)

Table B-l Chemical Resistance Chart (continued)

Table B-1 Chemical Resistance Chart (continued)

Appendix C

Manufacturers

This appendix lists of some of the major U.S.manufacturers of the materials, components, equipment, and/or support described in this book. The list is organized by chapter.

Most laboratories order materials through laboratory supply houses. This standard approach hasdeveloped because it is easy and efficient. It is also much easier to look through oneor twocatalogs than a room that is full of catalogs. However, there maybe occasions when youneed either (a) specific information that a supply house cannot provide or (b)materials that a supply house does notcarry.

Any product or manufacturer mentioned here is notnecessarily an endorsement of that product or manufacturer. Similarly, thelack of any mention of a product or manufacturer is notmeant to withhold anendorsement. Often, thespecific materials mentioned in this book were selected by my familiarity with them in my academic environment. Thus, materials peculiar to medical, industrial, and manufacturing environments may have been overlooked.- Fortunately, because many specific laboratory equipment pieces have a variety of applications, a piece of equipment used in a chemistry laboratory mayalso be used (for example) in a geology laboratory.

If you prefer to purchase from a laboratory supply house, the following are the most common supply houses in the United States. Thelisting shown below gives information for each supplier's main office. Because all of these suppliers have offices all across theUnited States andCanada, simply call themain office for the local office near you.

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