Page 244 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Free Radical Chain Polymerization 207

TABLE 6.7
General Physical Properties of Selected Fluorine-Containing Polymers
Polymer→ PTFE PCTFE PVDF PVF
o
Heat deflection temperature (1,820 kPa; C) 100 100 80 90

Maximum resistance to continuous heat ( C) 250 200 150 125
o
–5
– o

Coefficient of linear expansion (cm/cm C, 10 ) 10 14 8.5 10
Compressive strength (kPa) 2.7 × 10 4 3.8 × 10 4 – –
Flexural strength (kPa) – 6 × 10 4 – –
Impact strength (Izod: cm-N/cm of notch) 160 130 – –
Tensile strength (kPa) 2.4 × 10 4 3.4 × 10 4 5.5 × 10 4 –
Ultimate elongation (%) 200 100 200 –
Density (g/mL) 2.16 2.1 1.76 1.4

A slice of quartz develops a net positive charge on one side and a net negative charge on the
other side when pressure is applied. The same effect is found when pressure is applied by means of
an alternating electric field. This effect is known as the piezoelectric effect and is used for quartz

watches and clocks, for TVs, hearing aids, and so forth.
Several polymers are also effective piezoelectric materials. The best known of these is PVDF
(6.55). PVDF is employed in loud speakers, fire and burglar alarm systems, earphones, and

microphones.
R
R
F F (6.55)

Table 6.7 contains physical properties of selected fl uorine-containing polymers.
Nylon 11 (Equation 6.56) is also a piezoelectric material that can be aligned when placed in a
strong electromagnetic field giving films used in infrared-sensitive cameras, underwater detection

devices, and in electronic devices since it can be overlaid with printed circuits.
H N–(CH ) –COOH → –(–HN–(CH ) –COO–)– (6.56)
2
2 10
2 10
11-Aminoundecanoic acid Nylon 11

Ethylene tetrafluorethylene (ETFE) (6.57) was developed by DuPont in the 1970s to be an aero-
nautical insulation. ETFE was made from a waste product of lead and tin mining. ETFE is being

used in a variety of applications. It is used as a covering for electrical wring, inflated in pillows as a
building material, and as glass-like sheets that have an equal to and better light transmission com-
pared with glass. In the nuclear industry, it is used for tie and cable wraps. Recently, it has become a
material in innovative building exteriors, including use in the Eden Project, Cornwall; Kansas City
Power and Light District, Kansas City; whale-shaped aquarium on New York’s Coney Island; and
most prominently displayed in Beijing’s National Stadium also called the Bird’s Nest. The Bird’s
Nest appears to be composed of loosely woven twigs. “Pillows” made from ETFE fi ll the spaces
between and above the “twigs.” It is also used to make the pneumatic panels that cover the outside of
the soccer stadium Allianz Arena in Munich and the Beijing National Aquatics Center, also called
the Water Cube, for the 2008 Olympics. ETFE panels are also employed as a dual laminate bonded
with fiber-reinforced polymer composites that are used as corrosive protective liners in pipes, ves-

sels, and tanks.

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