Abstract: Article and method of making same by laser-ablation-machining of (a) aromatic and/or amorphous polyamide material, or (b) polymeric material having repeating in its polymer backbone aromatic rings and aliphatic chains (with the proviso that the aliphatic chains have at least 4 carbon atoms when the material is a polyester, and preferably in all cases U.V. laser radiation is preferred, preferably at wavelengths greater than 248 nm from a KrF or XeCl excimer laser. The preferred polyamides, polyetheresters, and polyimides have superior machining performance and may be useful for making uniaxially electrically conductive articles by machining holes cleanly through laminar sheets of the preferred polymers, which sheets are subsequently metal plated.

Abstract: A polymeric composition comprises:(i) an aromatic polyimide or an aromatic carboxylic ester polymer,(ii) a substantially wholly aliphatic polyamide, and(iii) a polyamide that contains both aromatic aliphatic moieties.It is found that the mechanical properties of blends of the aromatic polymers (i) and the polyamides (iii) can be significantly improved by the incorporation of a quantity of the aliphatic amides (ii), even though the miscibility of polymers, as observed by their glass transition temperatures may remain unchanged.

Abstract: An article of manufacture, for example a conductor for an electrical wire or cable, is provided with a refractory coating preferably formed from a refractory metal or semi-metal oxide or nitride and preferably deposited on the surface of the article by a vacuum deposition process such as a sputter ion plating method. Adhesion of the refractory coating, especially at high temperatures may be improved, and migration of the substrate metal through the coating may be suppressed by varying the stoichiometry of the coating through its thickness and/or by the provision of a metallic or refractory intermediate layer. The articles are particularly suitable for use in circuit and signal integrity cables.The vacuum deposited refractory layer may constitute the sole refractory, or additional refractory layers may be deposited by other methods e.g. a sol-gel method.

Abstract: A sheet laminate of polyimide and amorphous polyamide especially suitable for making anisotropically electrically conductive articles by laser abiation drilling followed by metal plating. Preferred polyimides include those derived from polymerization of 4,4'biphenyldianhydride and 4,4'-diaminobiphenylether or p-phenylenediamine. Preferred amorphous polyamides include those derived from condensation of terephthalic acid with isomers of trimethylhexamethylenediamine.

Abstract: A tubular heat recoverable article comprises conductive polymeric material and is heated to effect recovery by the passage of electrical current therethrough. Elongate electrodes are attached on the surface or embedded in longitudinal flanges extending along the article. The flanges also comprise conductive polymeric material but are not heat recoverable, and therefore remain substantially undeformed on recovery other than bending to accommodate transitions. This means that the contact resistance between the electrode and the conductive material of the flange does not increase significantly on recovery.

Abstract: An article of manufacture, for example a conductor for an electrical wire or cable, is provided with a refractory coating preferably formed from a refractory metal or semi-metal oxide or nitride and preferably deposited on the surface of the article by a vacuum deposition process such as a sputter ion plating method. Adhesion of the refractory coating, especially at high temperatures may be improved, and migration of the substrate metal through the coating may be suppressed by varying the stoichiometry of the coating through its thickness and/or by the provision of a metallic or refractory intermediate layer. The articles are particularly suitable for use in circuit and signal integrity cables.The vacuum deposited refractory layer may constitute the sole refractory, or additional refractory layers may be deposited by other methods e.g. a sol-gel method.

Abstract: A support for an elongated piezoelectric pressure sensor, which is general cylindrical in shape is mounted on a hollow support member that has a thickness and strength selected to meet desired conditions. The elongated piezoelectric pressure sensor is wound in a helical depression on the exterior of the support member, and the support member in turn is filled with a potting material having a bulk modulus of elasticity selected to provide a sufficient flexibility so that the elongated piezoelectric sensing element generates signals that have a desired sign characteristic and improved acoustic response.

Abstract: A pressure sensing transducer comprises a central region which comprises a potting material and which is surrounded by a helix of piezo electric coaxial cable. The transducer includes a barrier that suppresses transmission of external pressure variations to the central region. In addition, the overall radial stiffness of the potting material and barrier is sufficiently low that the electrical signal generated by the coaxial cable have a d.sub.31 polarity (corresponding to axial stretching and contracting of the cable).

Abstract: A water stabilizer polymeric composition incorporating a hydrated alumina filler, which is characterized by the presence of an effective amount of an antimony V compound. The compositions have a reduced tendency to absorb water and specific compositions find applicaiton as electrical insulation and in the production of dimensionally recoverable article.

Abstract: A piezoelectric coaxial cable comprises a central stretchable electrical conductor (1), preferably formed from a low melting point metal alloy, a piezoelectric intermediate layer (2), preferably formed from a vinylidene fluoride polymer which has been stretched and radially polarized to render it piezoelectric, and an outer electrical conductor (3).The intermediate layer has a ratio R of its internal radius to its external radius which is preferably not more than 0.5 and more preferably not more than 0.4. This construction enables coaxial cables to be formed without voiding or breaking of the internal conductor during stretching.

Abstract: A piezoelectric coaxial cable comprises a central stretchable electrical conductor (1), preferably formed from a low melting point metal alloy, a piezoelectric intermediate layer (2), preferably formed from a vinylidene fluoride polymer which has been stretched and radially polarized to render it piezoelectric, and an outer electrical conductor (3).The intermediate layer has a ratio R of its internal radius to its external radius which is preferably not more than 0.5 and especially not more than 0.4. This construction enables coaxial cables to be formed without voiding or breaking of the internal conductor during stretching.

Abstract: Tracking is reduced in insulators comprising one or more polymers and an anti-tracking filler system comprising (a) a hydrate of alumina having a specific surface area of at least 2 m.sup.2 /g measured by the BET method, and (b) a compound selected from the group consisting of oxides, mixed oxides and mixtures of oxides wherein said compound contains at least one element selected from the group consisting of transition series elements, lanthanide series elements and nontransuranic actinide series elements.

Abstract: Novel polymeric compositions having non-linear resistance characteristics, together with electrical equipment comprising such compositions. Any polymer may be used; the polymer contains substantial proportions of certain particulate fillers of a given structure, for example the perovskite and spinel structures.

Abstract: A dimensionally recoverable body, which is preferably heat-recoverable, has a body wall which is provided with a plurality of locking elements that are engageable with each other, or are engageable with corresponding elements located on a separate partition, to furcate the body into a plurality of channels.The body may be used for enclosing branch-offs in electrical cables in order to protect the enclosed branch-off from the environment.

Abstract: Terminations and splices in high voltage electrical cable can be shielded by shrinking over the termination or splice a heat recoverable hollow article which comprises a heat-shrinkable outer sleeve whose outer surface is anti-tracking at voltages of 2.5 KV and at least part of whose inner surface has a layer thereon which is solid at room temperature and which has electrical stress-grading character.

Abstract: A process for the manufacture of a dimensionally recoverable article comprises forming a plurality of separate component parts thereof, joining the component parts together to form the article, cross-linking the polymeric material from which the parts are formed after they have been joined together, and then expanding the article.The process enables dimensionally recoverable articles of complex shape to be manufactured by high speed moulding processes or extrusion processes without the need for curing of the article during formation thereof.

Abstract: Tracking is reduced in insulators comprising one or more polymers and an anti-tracking filler system comprising (a) a hydrate of alumina having a specific surface area of at least 2 m.sup.2 /g measured by the BET method, and (b) a compound selected from the group consisting of oxides, mixed oxides and mixtures of oxides wherein said compound contains at least one element selected from the group consisting of transition series elements, lanthanide series elements and nontransuranic actinide series elements.

Abstract: The invention relates to novel melt processable polymer compositions which comprise a blend of non-silicone polymer and a monoorganic polysiloxane resin. Such compositions are useful inter alia as flameproof and moisture resistant coating compositions and in the product of heat shrinkable silicone elastomer compositions.

Abstract: A polymer composition containing silicon carbide of a critical maximum average particle size can be processed into heat-shrinkable articles possessing nonlinear electrical resistance characteristics. An embodiment of the invention provides a heat-shrinkable article comprising a laminate of a layer of elastomer, including silicon carbide particles, and a layer of a heat-shrinkable polymeric material. The elastomeric layer may be a blend of a rubbery polymer and a low density polyethylene having dispersed therein particulate silicon carbide of particle size finer than about 300 grit.

Abstract: A heat-recoverable article comprises a memory metal member to which has been imparted both thermally-recoverable and resiliently-recoverable strain. The resilient strain is retained by means of a disburdenable keeper, preferably one made from fusible or chemically degradable material, which can be removed, for example, by heating or chemical treatment, to allow resilient recovery. The article is preferably so constructed that it can be heated to obtain both thermal and resilient recovery simultaneously. One preferred form of article is a radially expanded longitudinally split tube, the keeper being positioned in the split. Such an article can be used as a connector to secure an earth lead to the sheath of a mineral-insulated cable.