FRANCIS S. INGRAHAM D. F. WOOLEY, JR.
Polvvinvlidene Fluoride A corrosion resistant material with a record
of satisfactory
psi.), the Izod impact (unnotched, 30 ft.-lbs./in.), and superior abrasion resistance (17.6 mg./lOOO cycles). Color possibilities are unlimited. In flammability tests, the material is nondripping and self-extinguishing. Since crystalline melting point of polyvinylidene fluoride resin is 340" F., it can be fabricated at reasonably low temperatures-400-550" F. Finished parts can be molded directly by use of any of the standard molding techniques-i.e., compression, injection, transfer, or blow molding. Polyvinylidene fluoride resin is also easily extruded for wire coating, tubing, rod, or pipe. In certain cases it might be desirable to make a basic shape of Kynar, and then machine it to final size and shape; it can be easily machined under standard conditions. Intricate shapes can also be formed by hot-air welding. Similarly, sheets or film can be welded together to form a continuous barrier. The excellent thermal oxidative stability of this material is illustrated by the fact that no changes in tensile properties occur after an exposure (on film) of one year in an air-circulating oven at 300' F.
performance in equipment f o r
the chemical industry olyvinylidene fluoride resin is a new member in the pfamily . "of fluortne-containing : polymers. The other fluorocarbon polymers are polytetrafluoroethylene and polychlorotrifluorwthylene ; two copolymers, the copolymer of tetrafluoroethylene and hexafluoropropylene and the copolymer of chlorotrifluoroethylene and vinylidene fluoride complete the family. (Pennsalt produces polyvinylidene fluoride resin under the trade name of Kynar) . The chemical equations for the production of these various polymers are shown in Figure 1. Polyvinylidene fluoride contains carbon, hydrogen, and fluorine. PTFE and FEP contain only carbon and fluorine. Polychlorotrifluoroethylenecontains carbon, chlorine, and fluorine. The copolymer of vinylidene fluoride and chlomtrifluoroethylenecontains carbon, hydrogen, chlorine, and fluorine. Polyvinylidene fluoride is one of the higher fluorinecontaining polymers. Of the group presented, only FTFE and FEP contain a higher percentage of fluorine than Kynar-76% compared to over 59%. This high fluorine content explains the stability and chemical resistance of this material.
Commmial Forms of Resin
Kynar is supplied in four basic forms: powder, pelicts, solution, and dispersion. The powder is used for molding or for making special solutions or dispersions. The pellets are used for molding or extruding. The solution is used for film casting; the dispersion is applied by brushing or spraying to various substrates for chemical and/or corrosion resistance. Three melt viscosity grades are available in each of the basic forms to provide a greater range in processing ease and impact properties. The spread in molecular
Physical Properties
The physical properties of Kynar are presented in Table I. Of particular importance are the high tensile strength (7000 p.s.i.), compressive strength (10,000
17W F. 2HCFI 2HCF$J
3CFE * CFs-
2HF 100' F.
+ CF, = I
7 2HCl + Cfy 600" F
CFy
-
Potytehnfluoroethylene IPEE1
CFl
2CF1 * Cf-CF,
I -I
(CF2-CFl-CF,-CF-J, Cfi
Copolymer of tetmfluoroethylsl~ and hrx&aropropylene I FEP)
t
Kh- Wh
m-
I
(CF, -&-CFE
(CF,-
CFCI).
Polyvinylidene fluorids
-CFCl).
to*lyrner ot rhlorotrifiuoroethylens ond vinylidene fluoride
Pol~,duonthloroet~ene
I
VOL 56
NO. 9 S E P T E M B E R 1 9 6 4
53
TABLE I.
Property
Measurement
Claritv
Transparent tc Translucent
Melting point, crystalline
340
Specific gravity
1.74-1.78
Specific volume
15.7
iYnd
PHYSICAL PROPERTIES
4STM Test
'Measurement
Heat distortion temperature, 66 p.s.i. 264 p.s.i.
F. D792 cu. in./lb.
Abrasion resistance, Tabor
I ASTM
1
Unit
F.
300 195
' F.
17.6
mg./1000 cycles
-
1.42
Molding temperatures
400-550
Mold shrinkage, average
0.020
in./in.
Tensile strength, 77' F.
7000
p.s.i.
D638
Tensile strength. 212'F
5000 20-400
p.s.i.
D638
per cent
D638
Yield point, 77' F.
5500
p.s.i.
D638
Test
I D648 ~
D648
CS-17
Yield point, 212' F.
2500
p.s.i.
D638
Creep, 2000 p.s.i., 77' F., 10,000 hrs.
0.02
in. /in.
Compressive strength, 77' F.
IO, 000
p.s.i.
Modulus of elasticity, 77" F., in tension
2 . 5 X 105
Izod impact, notched, 77' F.
D542 F.
Coefficient of sliding friction to steel Thermochemical properties (estimated) l / n (CH2CFA CH2CF2(g) A H 2 9 8 1/n (CH*CF2), -+ 2C 2HF(g) Thermal coefficient of linear expansion
-
+
0.14-0. I ?
$37.8
kcal.
-16.3
kcal.
8 . 5 X lo6
11' F.
Thermal conductivity (room temperature to 325" F.)
0.14-0.11
B. t.u. /hr.-ft.O F.
Specific heat
0.33
B.t.u./lb.-o F.
D695
Thermal degradation temperature
>600
a
p.s.i.
D638
Low temperature embrittlement
