Polysulfone, dielectric

Polymers are used as inserts for pins and contacts. Important properties of the commonly used insert materials have been compiled (31). Polysulfones are high temperature thermoplastics that have high rigidity, low creep, excellent thermal stabiHty, flame resistance, low loss tangents, and low dielectric constants. The principal weakness of polysulfones is their low chemical resistance. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

Polysulfones are good insulators even in hot environments, with high dielectric resistivities and low or moderate loss factors. Special grades are marketed for electrical applications. 

Polysulfone Cheiin DvncUtiics. Carbon-13 nmr has been used recently to resolve a puzzling problem in the dynamics of polysulfone chains (9,10,11). Some years ago. Bates, Ivin and Williams (12) reported that measurements of the dielectric dispersion in solutions of alternating 1 1 copolymers of sulfur dioxide with hexene-1 and 2-methylpentene-1 show no loss in the high frequency region, Le. 

Figure 18.18 Map of dielectric properties of engineering plastics. Among engineering plastics, SPS (impact modified and GF-reinforced HB and IR grades) has very low dielectric dissipation factor and dielectric constant following those of fluorocarbon polymers. PSF, polysulfone PPE, poly(phenylene ether) PES, poly(ether sulfone) PAr, polyarylate...

The effect of diluents on the viscoelastic behavior of amorphous polymers is more complex at temperatures below T, i.e., in the range of secondary relaxation processes. Mechanical, dielectric and NMR measurements have been performed to study the molecular mobility of polymer-diluent systems in this temperature range (see e.g. From extensive studies on polymers such as polycarbonate, polysulfone and polyvinylchloride, it is well known that diluents may suppress secondary relaxation processes. Because of the resulting increase in stiffness, these diluents are called antiplasticizers . Jackson and Caldwell have discussed characteristic properties... 

Polysulfone is UL listed for continuous service at 320F, although it will withstand higher temperatures intermittently. It offers a good combination of electrical properties dielectric strength and volume resistivities are high, while dielectric constant and dissipation factor are low. 

Dielectric measurements on polysulfone were conducted at 10, 10, and 10 Hz. The data were... 

An enhanced dielectric loss maximum was observed at -85°C when a polysulfone sample which contained 0.76 wt. % unassociated water and no detectable level of clustered water (<0.01 wt. %) was run (Fig. 6, curve A). An apparent low temperature broadening of the dielectric loss dispersion was noted for another polysulfone specimen with 0.76 wt. % unassociated water and an additional 0.04 wt. % clustered water (Fig. 6, curve B). However, when a polysulfone sample which contained the same amount of unassociated water as the two prior samples but had 0.16 wt. % clustered water was analyzed, it had a significantly more intense loss peak centered near -105°C (Fig. 6, curve C). We believe that this shift in loss maximum and increase in loss intensity is caused by the development of an additional secondary loss peak about 20° below the 3-transition (Figure 6). In earlier work we had observed the same phenomenon in polycarbonate where the new loss peak occurred about 40 below its 3-transition as a separate loss peak. 

Figure 5. Polysulfone beta transition s dielectric loss as a function of unassociated...

Figure 6. Effect of clustered water on the polysulfone beta transition s dielectric...

Polyethylene samples were also exposed to conditions which created 0.4% clustered water and dielectric data taken at low temperatures on the samples. The same loss maximum noted In polycarbonate and polysulfone near -100 C at 1 kHz was also noted In polyethylene. A special polyethylene sample was molded around a PTFE sheet. The PTFE was removed and replaced with distilled water. This sample was equivalent to a thin water layer between polyethylene sheets. The dielectric behavior of this sample was quantitatively equivalent to that of the polyethylene containing spherical clusters of water if the difference in geometry of the water phase is taken into account. Figure 7 shows the logarithm of the frequency of loss maxima due to water clusters versus reciprocal temperature for polyethylene, polycarbonate, poly(vlnyl acetate and polysulfone. The polysulfone data from Allen are shown for comparison and It Is seen that the data can be Interpreted as a single mechanism with an activation energy of 7 kcal/ mole. 

Figure 8. Fourier transform dielectric spectrometer data for polysulfone containing clustered and urmssociated water...

Water absorbed in a polymer can exist in an unassociated state or as a separate phase (cluster). In this investigation the DSC technique of water cluster analysis was used in conjunction with coulometric water content measurements to characterize the water sorption behavior of polysulfone and poly(vinyl acetate) The polysulfone had to be saturated above its Tg (190°C) and quenched to 23°C for cluster formation to occur while cluster formation occurred isothermally at 23°C in the poly(vinyl acetate) Both polymers showed an enchancement of their low temperature 3-loss transitions in proportion to the amount of unclustered water present. Frozen clustered water produced an additional low-temperature dielectric loss maximum in PVAc and polysulfone common to polyethylene and polycarbonate as well. Dielectric data obtained on a thin film of water between polyethylene sheets was in quantitative agreement with the clustered water data. 

The simple and complex aromatic polyesters, polysulfones and polyarylene ketones possess the complex of valuable properties such as high physic-mechanical and dielectric properties as well as increased thermal stability. 

The polysulfone on the basis of bisphenylpropane also possesses high dielectric characteristics volume resistivity 10 electric inductivity at a frequency 10 Hz is 3, 1 dielectric loss tangent at a frequency 10 Hz is 6... 

Initial evaluation of commercially available plastic films disclosed that none simultaneously satisfied all our requirements. Dielectrically acceptable tapes were mechanically weak, and mechanically strong tapes had unacceptable dielectric properties (see Table II). The Teflons, Kaptons, and other exotic tapes had attractive properties but were set aside because of their very high costs. Attempts to reduce the 60 Hz, 4.2 K loss tangents of polysulfone and polycarbonate by altering their chemical construction were unsuccessful. Consequently, the decision was made to modify the dielectric and mechanical characteristics of the less expensive, intrinsically lower loss polyolefins. This development work is described in the following sections. 

Polysulfones exhibit excellent dielectric properties. They exhibit high dielectric breakdown strength and low dielectric constant. They also exhibit low dielectric loss. Because they are amorphous, the electrical properties such as dielectric constant and dissipation factor are stable across a wide temperature range. They are also stable over a wide frequency range. The desirable electrical properties in concert with attractive flammability properties have made polysulfones successful in many electrical and electronic insulation, business machine, and lighting applications. Polysulfone electrical properties can be found in Table 13.7. 

Polysulfones are used in quite a few electrical and electronic applications. They offer a very good fit in such applications because of their good dielectric strength, low dielectric constant and low dissipation, and excellent dimensional stability. PSF and PSF blends are used in a variety of electronic connectors because of flammability resistance, dimensional stability and warp resistance, and heat resistance. Good processability is also critical in this application in that tight dimensional tolerances are required for success in connector applications. For similar reasons, PES... 

The effect of moisture on the p relaxations in amorphous phenylene polymers is well documented (93-95) for many of the systems cited previously. For example, Allen and co-workers (93) determined that both the dielectric and mechanical P relaxations in polysulfone, polycarbonate, polyphenylene oxide, and polyether sulfone were dependent on the water content of the samples. In addition, the amount of water absorbed depended on the polarity of the molecule. The effect of moisture on the dielectric p process in these polymers appears to be greater than for the mechanical loss process, as illustrated in Figures 41 and 42 (93). 

Saxena Pooja, Gaur Mulayam Singh, Shukla Prashant, et al. Relaxation investigations in polysulfone Thermally stimulated discharge current and dielectric spectroscopy. J. Electrostat. 66 no. 11-12 (2008) 584-588. 

Fluorized carbon polymer films have been applied as a low-loss substrate material for flexible circuits. However, they do not have good dimensional stability or adhesion characteristics. High cost of the materials is the major reason that they cannot be standard in flexible circuits. In the last 20 years, several heat-resistant films, such as polypalabaUc acid film and polysulfon film, have been developed as alternative substrate materials in flexible circuits instead of polyimide films. Unfortunately, there was no successful material from a business standpoint. LCP films and PEEK have been considered as the new materials of high-speed flexible circuits based on the low dielectric constant and loss tangents. 

Mackinnon, A.( Jenkins, S.D., McGrail, P.T., and Pethrick, R.A. (1993) Dielectric, mechanical and rheological studies of phase-separation and cure of a thermoplastic modified epoxy-resin -incorporation of reactively terminated polysulfones. Polymer, 34 (15),... 

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