Patrick E. Cassidy

POLYMERS DERIVED FROM HEXAFLUOROACETONE

Abstract The continuing demand for polymeric materials with a unique combination of properties has brought forth a sizable research effort concerning the use of trifluoromethyl substituents, particularly the 1,1,1,3,3,3-hexafluoroisopropylidene (HFIP) function derived from the incorporation of hexafluoroacetone (HFA) into the monomer. This work had its beginnings approximately 25 years ago when Rogers briefly reported in a patent the preparation of polyimides (PIs) from an hexafluoroisopropylidenebrideged diamine [1,2]. Since then numerous efforts have been made toward the synthesis, characterization, and evaluation of CF3-containing polymers. Much of this information is found in patents, indicating the importance of these polymers to industry. At the present time, at least 11 known classes of polymers containing pendant or backbone-incorporated bis-trifluoromethyl groups have been reported. These polymers show promise as film formers, gas separation membranes, seals, soluble polymers, coatings, and in ot...

A Review on Biodegradable Plastics

Abstract The interaction between synthetic polymers and the natural environment in terms of the effects of oxygen, radiant energy, and living organisms has been extensively studied over the past two decades [1]. However, the recent trends in the preservation of the environment have created much public interest. This is due to the heavy usage of plastics as packaging materials in consumer industry. Materials used as packaging films and the like are not expected to have a long service life. Among several such materials, polyolefins have received special criticism because of their longevity and stability under soil burial conditions. The most likely degradative processes acting on buried polyolefins are simple oxidation and microbial attack, in addition to photodegmdation under the influence of UV sunlight. The disposal of plastics as refuse or litter is thus a volume problem rather than a weight problem. The relative proportion of plastics in refuse increases every day on account of their low degradability....

Water Permeation through Elastomers and Plastics

Abstract The available data on permeability, diffusivity, and solubility of water and water vapor through elastomers and plastics have been summarized. In many ways, the last five years have been a...

Gas transport properties of a series of poly(ether ketone) polymers

Abstract The gas sorption and transport properties of a series of poly(aryl ether ketone) materials are reported. In this series, the isopropylidene group (C(CH 3 ) 2 ) in the backbone are systematically replaced with a hexafluoroisopropylidene group (C(CF 3 ) 2 ). Dynamic mechanical analysis and differential scanning calorimetry were used to show that the substitution of C(CF 3 ) 2  for C(CH 3 ) 2  units results in a stiffer polymer chain. Free-volume calculations show that the substitution opens up the polymer structure and leads to an increase in diffusion coefficients. Methane and carbon dioxide sorption measurements were made to examine the solubility and diffusivity contributions to the permeability. The permeability increases as C(CF 3 ) 2  units replace the C(CH 3 ) 2  groups and, in general, it is the increase in diffusivity that accounts for the permeability increase. Along with the increase in permeability is an increase in the selectivity for gas pairs like helium/methane and carbon dioxide/methane. This simultaneous increase in permselectivity and permeability when C(CF 3 ) 2  units replace C(CH 3 ) 2  units seems to be a general trend, as it has been observed for polycarbonate and polysulphone materials as well.

Poly(oxadiazole-amide)s containing hexafluoroisopropylidene

Abstract A series of new poly(oxadiazole-imide)s that are soluble in polar solvents, and some of which are soluble in chloroform, have been prepared by incorporating the hexafluoroisopropylidene unit and other flexible linkages into the backbone. Films of these poly(oxadiazole-imide)s cast from solution are light-tan to yellow in colour and have ultimate tensile strengths ranging from 89.0 to 95.6 MPa. Initial weight loss occurs near 380°C in air by thermogravimetric analysis, while one polymer appears unchanged after isothermally ageing for 300 h at 300°C in air. The inherent viscosities ranged from 0.34 to 0.54 dl g −1 in N , N -dimethylacetamide. The refractive indices of the poly(oxadiazole-imide)s are near 1.6 and the dielectric constants range from 2.9 to 3.2 at 1 MHz. Moisture absorptions of the poly(oxadiazole-imide)s are near 3% by weight. A new hexafluoroisopropylidene- and imide-containing dicarboxylic acid and its diacid chloride and six new ether- and imide-containing dicarboxylic acids and their diacid chlorides are also presented. These monomers were prepared from commercially available diamines and trimellitic anhydride without the use of an amide solvent.

Thermally Stable Polymers: Polyoxadiazoles, Polyoxadiazole-N-Oxides, Polythiazoles, and Polythiadiazoles

Abstract This review is organized into four sections according to backbone functional group: (1) poly(l)3,4-oxadiazoles), (2) poly(l,2,4-oxa-diazoles) and poly(l,2,4- and 1,2,5-oxadiazole-N-oxides), (3) poly -thiazoles, and (4) polythiadiazoles. The structures of the principal groups are given below.

Synthesis of novel fluorine‐containing poly(aryl ether ketone)s

The high-performance fluorinated polymers have been receiving considerable attention as interesting advanced materials. The incorporation of fluorine atoms into polymer chains leads to polymers with increased solubility, flame resistance, thermal stability and glass transition temperature while also leading to decreased color, crystallinity, dielectric constant and moisture absorption. 2,3,4,5,6-Pentafluorobenzoic acid (PFBA) is a valuable intermediate for pharmaceuticals, pesticides, perfumes, cosmetics and so on, and it is available as a commercial product. However, the polymers derived from PFBA have not been reported so far. In this paper, we report the synthesis and characterization of novel fluorinated poly(aryl ether ketone)s (PEKs) containing 2,3,5,6-tetrafluoro-1,4-phenylene moieties derived from PFBA. Novel fluorinated PEKs are prepared from PFBA by aromatic nucleophilic substitution reaction, of which Mn values range from 2.28 × 104 to 1.04 × 105. They have all para connected linear structures. The aromatic fluorine of the para position to the carbonyl groups of monomers is preferentially substituted by phenoxide and this para orientation is mainly attributed to the steric effect rather than π-electron density. The obtained PEKs except 8F-PEKEK (BP) show excellent solubilities in common solvents and can be cast into tough transparent films. They also exhibit high glass transition temperatures depending on the structures and outstanding thermal stabilities. Furthermore, these fluorine-containing PEKs exhibit low dielectric constants from 2.87 to 3.52 at 1 MHz. Copyright

Electrical resistivity of carbon-black-loaded rubbers

Abstract Uses are growing for rubbers with varying levels of resistivity. High electrical resistivity is very much essential in wire and cable insulation applications. Low levels of resistivity are needed for electrostatic discharge in phonograph records and many medical, industrial, and military products and for semiconductive cable compounds. The level of resistivity depends upon the number of contacts or near contacts between conductive particles in the rubber matrix. Loading level is obviously a major determinant in addition to physicochemical characteristics of the black. In the latter regard, the highly conductive grades are characterized by small particle size, high structure, high surface porosity, and low volatile content. One would, therefore, seek the reverse of those factors for high-resistivity rubbers. One of the goals of materials research now is to create new materials with physicomechanical properties tailored to a particular application and to understand the physical processes which dete...

The Relationship of Glass Transition Temperature to Adhesive Strength

Abstract The effects of glass transition temperature (Tg ) on mechanical properties have been further demonstrated by the observation of adirect relationship between the Tg of an epoxy adhesive and its lap shear bond strength to metal at elevated test temperatures. An additive (coupling agent) which lowers the Tg from a point near or above the test temperature to below it causes a subsequent decrease in the strength of the system and generally increased cohesive failure. Therefore effects on the Tg of the adhesive are more important than on interfacial properties. The end result is that differential thermal analysis (DTA) can be utilized as a effective screening method for adhesives and additives, and can be a good indicator of maximum use temperature. From these data Tg can also be used to estimate adhesive strength at a given use temperature.

Synthesis and Properties of Hexafluoroisopropylidenecontaining Polyarylates and Copolyarylates

A homologous series of four aromatic polyesters and two series of copolyarylates were synthesized under phase-transfer conditions from monomers containing the isopropylidene (IP) and/or the hexafluoroisopropylidene (HFIP) moiety. The homopolymers were obtained in good yields, were soluble in common organic solvents, and would readily form clear, colorless films from solution. Thermal stabilities in air (dynamic-10% weight losses at 440°C-490°C; isothermal-100 h at 350°C, 7%-86% weight loss) revealed that resistance to thermo-oxidation was highest when the HFIP group replaced the IP moiety in the bisphenol rather than in the diacid. Other properties of the homopolymers which were measured were water absorption of 0.07%-0.35% (by weight), and the dielectric constant of 2.32 for the fully fluorinated polymer. Copolymers were prepared from mixtures of bisphenols A and AF, and each of the two diacids. The thermal stability and water absorption of both series were measured as functions of BPAF content. No significant change in properties was observed for copolymers with less than 70 mol.% BPAF comonomer.