Design Properties for Special Applications

Electrical Properties
The electrical properties of KYNAR PVDF grades 460 and 710-760 are shown in Table III. The combination of high dielectric strength and excellent mechanical properties over a broad temperature range is the reason that KYNAR resins are used for thin-wall primary insulation and as a jacket for industrial control wiring. Although its high dissipation factor limits the use of KYNAR resins at high frequencies, this property becomes an advantage in the fabrication of parts utilizing dielectric heating strengths.

Dielectric Variations with Temperature and Time
Values reflect the method of sample preparation, which influences the characteristics of the polymer that dictate the electrical properties. Above 1 MHz, the dependence of these properties upon frequency, temperature, and nature of the sample is complex.

Optical Properties
KYNAR PVDF films up to 0.005 in (0.125 mm) thick are transparent to translucent. The transmission spectrum in Table IV shows how light transmission varies with thickness for KYNAR 460 resin. See Figure 5 for the infrared absorption spectrum.

Stability to Effects of Weather and Ultraviolet Radiation
Table V shows that KYNAR PVDF Film maintains its mechanical properties throughout many years of outdoor exposure. Clear films, exposed to the sun at a 45° angle South, retain their tensile strengths over a 17-year period. During the first few months of exposure when normal crystallization takes place, the percent of elongation at break decreases to a level that remains essentially constant with time. In addition, the weathered films remain flexible and capable of being bent 180° without cracking. 

Table III : Electrical properties for various grades of KYNAR Homopolymer resins at room temperature.             Table IV : Precentage transmission of extruded KYNAR PVDF film in the ultraviolet region (200-400nm) as a fuction of thickness.   Table V : Stress/strain properties of 0.204 mm (0.008 in) weathered KYNAR PVDF film determined by ASTM method D882.

Outgassing Under High Vacuum
KYNAR homopolymer resins exhibit extremely low weight loss when exposed to high vacuum. At 100°C (212°F) and a pressure of 5x10(to the power or 6) torr, the measured rate of weight loss is 13 x lO(to the power of 2) g/cm squared

Fungus Resistance
KYNAR resins will not support growth of fungi when tested as described in Method 508 of Military Standard 810B (June 15, 1967).

Solubility
KYNAR resins have limited solubility. Table VI lists active, intermediate, and latent solvents. Generally, KYNAR resins are not soluble in aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated solvents, alcohols, acids, halogens, and basic solutions.  

Figure 5 : Infrared absorption spectrum of KYNAR PVDF film.                 Table VI : Solvents

Resistance to Nuclear Radiation The resistance of KYNAR fluoropolymers to nuclear radiation is excellent. The original tensile strength of the resin is essentially unchanged after exposure to 1000 megarads (Mrads) of gamma radiation from a Cobalt-60 source at 50°C (122°F) and in high vacuum (10 to the power of 6 torr). The impact strength and elongation are slightly reduced due to cross-linking. This stability to effects of radiation, combined with chemical resistance, has resulted in the successful use of KYNAR PVDF components in plutonium reclamation plants. Tables VII and VIII show minimal changes in tensile properties of KYNAR homopolymer and KYNAR FLEX resins exposed to E-Beam radiation in doses up to 20 Mrads according to ASTM D882 testing. Radiation Crosslinking The different grades of KYNAR homopolymer resin are readily crosslinked and do not degrade when irradiated with moderate doses of high energy electron or gamma radiation. The efficiency of crosslinking is influenced by the grade, that is, molecular weight variations are important. Figure 6 shows the response of various grades to high energy electron beam irradiation in terms of the amount of polymer that becomes insoluble in dimethylacetamide (DMAC), an excellent solvent for non-crosslinked PVDF resins. Examples of KYNAR PVDF-fabricated products utilizing radiation technology are heat-shrinkable tubing and insulated wire capable of withstanding high temperatures.

Table VII : Radiation crosslinked K KYNAR PVDF Tensile Modulus versus radiation dose exposure (Kpsi).         Table III : Radiation crosslinked KYNAR PVDF ultimate strength versus radition dose exposure (psi).