Abstract:
A band-shaped high-temperature superconductor (HTSL) with high critical current density can be produced economically in a wet-chemical process. In the process, a first precursor solution is applied to a carrier, dried, and annealed. Additional precursor solutions may then be applied, with the first precursor solution contain little or no pinning centers, and any subsequent precursor solutions contains a higher concentration of pinning centers than the first precursor solutions.
Abstract:
A method for preparing a bis(alkoxysilylorgano)dicarboxylate includes reacting a haloorganoalkoxysilane, a dimetal salt of a dicarboxyl functional compound, and a phase transfer catalyst. A quaternary iminium compound of a polyaza, polycycloalkene is useful as the phase transfer catalyst. The product may be a bis(alkoxysilylalkyl)fumarate, which is useful as a coupling agent in rubber compositions for tire applications.
Abstract:
The invention provides a process for grafting silicone onto a polyolefin comprising reacting the polyolefin with a silicon compound containing an unsaturated group in the presence of means capable of generating free radical sites in the polyolefin, characterized in that the silicon compound is a branched silicone resin containing at least one group of the formula —X—CH═CH—R″ (I) or —X—C≡C—R″ (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the —CH═CH— or —C≡C-bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of —X—CH═CH—R″ or with the acetylenic unsaturation of —X—C≡C—R″, X being bonded to the branched silicone resin by a C—Si bond, and R″ represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the —CH═CH— or —C□C-bond. The polyolefin is reinforced by grafting the branched silicone resin onto it.
Abstract:
A process for grafting hydrolysable silane groups to polyethylene includes reacting polyethylene with an unsaturated silane having at least one hydrolysable group bonded to Si, in the presence of a compound capable of generating free radical sites in the polyethylene. The grafted polyethylene prepared by the process can be shaped into a pipe and crosslinked by water flowing through the pipe.
Abstract:
The formation of band-shaped HTSL on a metal substrate is disclosed. The HTSL includes at least one buffer layer comprising zirconates and/or rare-earth oxides. The HTSL layer is formed on the buffer layer. The buffer layer has a texturing that in the case of a RHEED measurement results in discrete reflexes and not only in diffraction rings. In particular, the buffer layer may be textured along its interface with the HTSL layer.
Abstract:
The invention provides a process for grafting silane or silicone functionality onto a polyolefin, comprising reacting the polyolefin with an unsaturated monomer (A) containing an olefinic —C═C— bond or acetylenic —C≡C— bond and a reactive functional group X in the presence of means capable of generating free radical sites in the polyolefin and with an organosilicon compound (B) having a functional group Y which is reactive with the functional group X of the unsaturated monomer (A), characterized in that the unsaturated monomer (A) contains an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic —C═C— or acetylenic —C≡C— unsaturation of the unsaturated monomer (A).
Abstract:
The invention relates to a process for grafting hydrolysable silane groups to a polyolefin in which ethylene units, if present, form less than 50% by weight of the total polyolefin. The polyolefin is reacted with an unsaturated silane, having at least one hydrolysable group bonded to Si, or a hydrolysate thereof, in the presence of means capable of generating free radical sites in the polyolefin. The unsaturated silane has the formula R″—CH═CH—Z (I) or R″—C≡C—Z (II) in which Z represents an electron-withdrawing moiety substituted by a —SiRaR′(3-a) group wherein R represents a hydrolysable group; R′ represents a hydrocarbyl group having 1 to 6 carbon atoms; a has a value in the range 1 to 3 inclusive; and R″ represents hydrogen or a group having an electron withdrawing or any other activation effect with respect to the —CH═CH— or —C≡C— bond. The use of an unsaturated silane of the formula R″—CH═CH—Z (I) or R″—C≡C—Z (II) in carrying out the grafting reaction on the polyolefin may give enhanced grafting yield compared to grafting with an olefinically unsaturated silane such as vinyltrimethoxysilane not containing an electron withdrawing moiety Z. The invention permits to provide a silane-modified polyolefin having a high grafting efficiency while limiting/preventing polymer degradation by chain scission. The silane-modified polyolefin can be further reacted with a polar surface, a filler or a polar polymer or reacted on itself to crosslink the polyolefin and obtain enhanced physical properties of the composites made thereof.
Abstract:
This invention relates to the modification of elastomers by reaction with unsaturated silanes, to the modified elastomers produced and to articles produced by shaping and curing modified elastomer compositions. In a process according to the present, the silane has the formula: R″—CH═CH—C(O)X—Y—SiRaR′(3-a) (I) or R″—C≡C—C(O)X—Y—SiRaR′(3-a) (II) in which R represents a hydrolysable group; R′ represents a hydrocarbyl group having 1 to 6 carbon atoms; a has a value in the range 1 to 3 inclusive; Y represents a divalent organic spacer linkage comprising at least one carbon atom separating the linkage —C(O)X— from the Si atom, X is S or O; and R″ represents hydrogen or a group having an electron withdrawing effect with respect to the —CH═CH— or —C═C— bond; and the silane is reacted with the diene elastomer in the absence of any free radical initiator. This is advantageous because free radical initiators such as peroxides tend to degrade diene elastomers. In addition, safe handling and mixing of peroxides can be difficult for rubber compounders. The grafted diene elastomer produced has improved adhesion to substrates, for example reinforcing cords and fabrics used as reinforcement in rubber articles such as tyres.
Abstract:
The invention relates to a process for grafting hydrolysable silane groups to a polyolefin, comprising reacting the polyolefin with an unsaturated silane, containing an olefinic —C═C— bond or acetylenic —C≡C— bond and having at least one hydrolysable group bonded to Si, or a hydrolysate thereof, in the presence of means capable of generating free radical sites in the polymer. The silane contains an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic —C═C— or acetylenic —C≡C— unsaturation of the silane. The unsaturated silane may also contains electron-withdrawing moiety with respect to the olefinic —C═C— or acetylenic —C≡C— bond. The invention permits to provide a silane-modified polyolefin having a high grafting efficiency while limiting/preventing polymer degradation by chain scission. The silane-modified polyolefin can be further reacted with a polar surface, a filler or a polar polymer or reacted on itself to crosslink the polyolefin and obtain enhanced physical properties of the composites made thereof.
Abstract:
The present invention relates to a curable rubber composition comprising an organic elastomer, a filler and at least one curing agent for the elastomer. Such curable rubber compositions are widely used in the production of cured rubber articles, such as tyres, belts and hoses. The composition contains a branched silicone resin having Si-bonded hydroxyl groups or azo groups. This may lead to a reduction in the mixing energy required for processing, particularly in the energy required in the first (non-productive) mixing phase to give good dispersion of the filler in the organic elastomer. Use of the branched silicone resin can also accelerate cure (vulcanization), thus reducing the required cure time or reducing the amount of cure accelerator required.