Abstract: A process for preparing crosslinked or branched organopolysilanes involves reacting halosilanes with alkali metal and/or alkaline earth metal, the reaction mixture, immediately after reaction has ended, being treated at at least 50° C. for at least 30 seconds with a mineral treating agent which is one or more polysilicic acids, silicates or aluminosilicates.

Abstract: A curable composition is characterized by comprising an organic polymer having at least one silicon-containing group which has a hydroxy or hydrolyzable group bonded to the silicon atom and which is crosslinkable by forming siloxane bonds, and a specific metal salt of a carboxylic acid. The composition ensures practical curability and recovery properties and has mechanical properties including high strength and high elongation.

Abstract: Aqueous organopolysiloxane compositions containing a dispersed solid organopolysiloxane resin bearing both alkoxy and hydroxy radicals, a condensation catalyst, and a wetting agent are suitable for use as binders for the preparation of structures based on mineral fibers.

Abstract: A composition comprising a fluid, silica precursor (A) obtained by subjecting alkoxysilane(s) to hydrolysis/polycondensation in the presence of an acid catalyst, a basic compound (B) having a basic hydroxyl group and/or a basic nitrogen atom, wherein the pH of a 0.1 N aqueous solution of compound (B) is 11 or more, and the vapor pressure of compound (B) is 1.3 kPa or lower at 100° C., and an organic compound (C) having a boiling point of 100° C. or higher, compound (C) being compatible with silica precursor (A), wherein the amount of compound (B) is from 0.0015 to 0.5 mol, in terms of the total molar amount of the basic hydroxyl groups and the basic nitrogen atoms in compound (B), per mole of Si atoms contained in silica precursor (A).

Abstract: A new silicone condensation reaction, the condensation between an alkoxy silane or siloxane and an organo-hydrosilane or siloxane and catalysts therefore is described and claimed.

Abstract: Highly regular and well-defined structured polyorganosilsesquioxane polymer with superior heat resistance, combustion resistance and flexibility, wherein same or different kinds of substituents are bonded alternately, and the preparation method thereof. The polyorganosilsesquioxane prepared according to the present invention has a small molecular weight distribution and a high molecular weight, and is soluble in organic solvents because a three-dimensional network structure is not formed during the preparative condensation polymerization. Polyalkylaromaticsilsesquioxane obtained from the preparing method of the present invention is a useful heat-resistant material. It can be used as a heat-resistant coating agent, a protective coating agent of optical fiber, a coating material for resistor, heat-resistant paint, an adhesive and a releasing agent for precise molding. Also, it can be used for the semiconductor protective layer, interlayer dielectrics for semiconductor integration (e.g.

Abstract: The present invention provides a process for reacting A) polyorganosiloxanes which contain —Si(H) units and are of the general formula (I) with B) a mono- or pholyhydric alcohol, which comprises using small amounts of a mixture which consists of at least one acid and at least one salt of an acid as a catalyst.

Abstract: There is disclosed a three stage method for the preparation of ladder-like silicone polymers. The first stage comprises hydrolysis and polymerization of alkyltrialkoxylsilane-like monomers to give relatively low molecular weight prepolymers. The second stage comprises dehydrated condensation polymerization of the prepolymers to give high molecular weight polymers. The third stage comprises partial blocking of a proportion of the pendant Si—OH (silanol) groups with a pre-determined sub-stoichiometric amount of a blocking agent. Also disclosed are the prepolymers, polymers and partially blocked polymers so produced.

Abstract: By reacting two types of organosiloxane compounds in the presence of an alkaline compound and under conditions that do not substantially promote equilibration reaction, a linear organosiloxane polymer having a single peak molecular weight distribution is simply and economically produced with minimized formation of cyclics.

Abstract: Polydiorganosiloxanes of the general formula R1—(OSiR2)nOH??(I) are prepared by reacting hexaorganocyclotrisiloxanes of the formula (R2SiO)3??(II) with alcohols of the formula R1—OH??(III) where each R is the same or different and is a monovalent, optionally substituted hydrocarbon radical, R1 is a monovalent, optionally substituted hydrocarbon radical and n is an integer of at least 3, in the presence of a carbonate salt as a catalyst.

Abstract: The invention involves new syntheses for poly(methyl- and ethyl-silyne). The invention also includes silicon carbide (SiC) ceramics that can be produced from poly(methylsilyne), as well as other ceramics, which can be produced from these precursors by modified processing conditions.

Abstract: Three processes for the manufacture of polyhedral oligomeric silsesquioxanes (POSS) which utilize the action of bases that are capable of either attacking silicon or any compound that can react with a protic solvent (e.g. ROH, H2O etc.) and generate hydroxide [OH]?, alkoxide [RO]??, etc. The first process utilizes such bases to effectively redistribute the silicon-oxygen frameworks in polymeric silsesquioxanes [RSiO1.5]28 where ?=1-1,000,000 or higher into POSS nanostructures of formulas [(RSiO1.5)n?#, homoleptic, [(RXSiO1.5)n]?#, functionalized homoleptic, [(RSiO1.5)m(R?SiO1.5)n]?#, heteroleptic, and {(RSiO1.5)m(RXSiO1.0)n}?#, functionalized heteroleptic nanostructures. The second process utilizes base to aid in the formation of POSS nanostructures of formulas [(RSiO1.5)n]?# homoleptic and [(RSiO1.5)m(R?SiO1.5)n]?# heteroleptic and [(RSiO1.5)m(RXSiO1.

Abstract: A method of synthesizing metal alkoxide polymers is provided, for use, as an example, in synthesizing hybrid organic/inorganic materials with low optical absorption for optical applications. The method involves a plurality of acidolysis steps involving acidolysis of a metal alkoxide compound with an acid to produce an intermediate acidolysed solution, and combining and condensing the intermediate acidolysed solutions to produce the metal alkoxide polymer.

Abstract: A process for the continuous preparation of addition-crosslinking silicone rubbers from a base composition containing at least one polyvinyl polysiloxane and at least 10% by weight, based on the liquid silicone rubber, of hydrophobicized filler, by removing the base composition from a container whose volume reduces proportionally with the amount removed, and conveying the composition by way of a pump with a positive pressure difference to two further pumps (4) which convey the base composition onward, so a component A is prepared continuously by admixing at least one metal catalyst with one stream of the base composition, and a component B is prepared continuously and simultaneously by admixing the crosslinker and inhibitor with a second stream of the base composition, where the metal catalyst, crosslinker, and inhibitor are fed by way of a feed unit which meters in each of the substances.

Abstract: This invention relates generally to heat curable compositions, particularly well utilized for use as impregnation sealants curable using hydrosilation chemistry. The heat curable compositions of the present invention can be stored and shipped as a one-part composition. The composition includes at least one curable unsaturated organic component, at least one co-reactant, which has at least two functional groups reactive with the organic component, and at least one catalyst of initiating the cure of the composition.

Abstract: Heat-stable poly(ethynylene phenylene ethynylene polysiloxene(silylene)) polymers preferably of determined molecular mass, optionally bearing at the end of the chain groups derived from a chain-limiting agent. Processes for preparing these polymers, cured products obtained by heat-treating these polymers, and composite matrices comprising these polymers.

Abstract: The invention relates to a method for producing a sealed impregnation and/or release coating of flat joints, in particular of cylinder-head gaskets such as composite seals, metallic joints and multi-layered steel joints. The invention uses a silicone composition including at least a polyorganosiloxane A crosslinkable by a cationic and/or radical process by appropriate crosslinking functional groups, for example, of the alkenyl ether, acrylic, acrylate, epoxide and/or oxethane type; at least an initiator salt B selected among onium borates or an organometallic complex; and at least a reactive diluent C including a nonorganosilicon or organosilicon compound comprising in its structure at least a crosslinking functional group and optionally a secondary functional group different from the crosslinking functional group but capable of chemically reacting with a crosslinking functional group, for example of the hydroxyl, alkoxy and/or carboxyl type.

Abstract: The present invention provides novel “hybrid” silyl-terminated polymers that contain at least two different reactive end-capping groups. The “hybrid” silyl-terminated polymers of the present invention are produced by a novel single multi-step end-capping reaction of at least one silanol-terminated polymer with at least two silanes in the presence of a catalyst.

Abstract: A stacked film for semiconductor having superior adhesion to a coating film formed by a CVD process in, for example, semiconductor devices, an insulating film having the stacked film and a substrate for semiconductor using the insulating film are disclosed. The stacked film comprises (A) a film of an organic compound having a carbon content of 60% by weight or more and (B) a film prepared by heating a hydrolytic condensate obtained by hydrolysis and condensation of at least one compound selected from the group consisting of specific compounds represented by the general formulae (51) to (54) described hereinabove.

Abstract: The invention relates to metal complexes of formula (I) These complexes are particularly suitable for use as catalysts of hydrosilylation reactions.

Abstract: Condensation curable poly(fluoroorgano)siloxane-poly(silarylene)siloxane block copolymer compositions having a glass transition temperature not exceeding about −54° C. and excellent solvent resistance have been found useful as sealants. Polyalkoxysilylorgano compounds, such as 1,4-bis[trimethoxysilyl(ethyl)]benzene have been found to be effective as cross-linkers.

Abstract: Method is provided for selectively opening rings of polyhedral oligomeric silsesquioxane (POSS) compounds to from functionalized derivatives thereof or new POSS species. Per the inventive method, the POSS compound is reacted with an acid to selectively cleave bonds in the POSS rings to add functionalities thereto for grafting, polymerization or catalysis, to thus form new familes of POSS derived compounds. Also provided are the new compounds so formed. Method is also provided for expanding rings of POSS compounds. Per the inventive method, a POSS compound is reacted with silane reagents to obtain an expanded POSS framework with added Si ring substituends to form new families of POSS compounds. Also provided are the new compounds so formed.

Abstract: A room temperature curing organopolysiloxane composition is provided which displays no toxicity, is resistant to cracking and discoloration, cures rapidly, and yields a cured product of good hardness. This composition includes (A) an organopolysiloxane with at least two hydroxyl groups bonded to silicon atoms within a single molecule, (B) an organosilicon compound represented by a formula (I) shown below, and/or a partial hydrolysis condensate thereof, RaSiX4-a  (I) (wherein, R represents a substituted or unsubstituted monovalent hydrocarbon of 1 to 10 carbon atoms, X represents a hydrolysable group, and a represents an integer of 0 to 3), and (C) a bismuth compound-based curing catalyst.

Abstract: The invention discloses a novel method for the preparation of globular particles of a silicone resin or, in particular, a polyorganosilsesquioxane resin having properties suitable as an adjuvant in hair-care toiletry preparations by the hydrolysis condensation reaction of an organotrialkoxy silane compound such as methyl trimethoxysilane in an aqueous alkaline medium. Characteristically, the aqueous reaction medium is alkalified with ammonia or, preferably, an amine compound, e.g., mono(n-alkyl) amine compound, to have a specified pH value of 10.0 to 13.0 and the hydrolysis condensation reaction of the starting silane compound in the aqueous medium is conducted in the presence of metallic ions or, in particular, magnesium ions in a specified concentration of 1×10−5 to 1×10−2 mole/liter.

Abstract: Disclosed are an organic domain/inorganic domain hybrid material comprising an organic domain comprising at least one water-soluble organic polymer having anionic and/or cationic functional groups, and an inorganic domain, the organic and inorganic domains being chemically bonded to each other through the functional groups, the inorganic domain comprising inorganic bridges, each independently comprising at least one Si atom, at least two O atoms and at least one divalent metal atom, wherein the Si atom and the O atoms together form at least one siloxane linkage arranged longitudinally of the inorganic bridge, wherein each divalent metal atom is ionically bonded to the O atoms of the siloxane linkages positioned adjacent to the divalent metal atoms, wherein, when at least a part of the organic domain is comprised of at least one organic polymer having an anionic functional group and optionally a cationic functional group, the organic domain/inorganic domain weight ratio is less than 1.

Abstract: A composition having water-repellency at high temperature is provided. Some of the invention compositions also exhibits oil-repellency at high temperature. The composition comprises a fluorocarbon silane or hydrolyzate thereof; a surfactant; a polymerizable, silicon-containing compound; and a catalyst.

Abstract: A room temperature organopolysiloxane composition is provided, which can be cured rapidly and right down to deep sections. The cured products have good rubber characteristics. The composition includes (A) 100 parts by weight of a diorganopolysiloxane represented by a general formula (1) shown below, wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, X represents, independently, an OH group, an alkoxy group or an acyloxy group, a represents an integer from 0 to 2, and n represents a number which results in a viscosity at 25° C. of 25 to 1,000,000 mm2/s; (B) 2 to 50 parts by weight of a hydrolysable silane with at least two acyloxy groups, a partial hydrolysis-condensation product thereof, or a mixture thereof; and (C) 5 to 200 parts by weight of an inorganic filler capable of generating water through a reaction with a carboxylic acid generated by hydrolysis of the constituent (B).

Abstract: This invention relates to polyurethane compositions which cross-link via a silane polycondensation and contain at least one alkoxysilane-functional polyurethane, at least one basic filler, at least one reaction product of an aminosilane with a maleic or fumaric ester, at least one organometallic compound and optionally additional auxiliary substances, to a process for their preparation, and to their use.

Abstract: This invention relates to asymmetrical, substituted polysiloxanes which show good compatibility in a variety of oils and improve the spreading behavior of oil-based formulations, to a process for preparing these asymmetrical polysiloxanes and to oil formulations containing said asymmetrical polysiloxanes. The asymmetrical polysiloxanes of this invention are used in herbicidal and pesticidal compositions, in cosmetic and pharmaceutical preparations as well as in industrial applications. The assymmetrical substituted polysiloxanes have the following formula wherein R1, R2, Z a and b are described herein.

Abstract: Disclosed are a coating composition comprising a polymer dispersed in an aqueous medium, the polymer containing (a) a hydrolysate of an organosilane and/or a condensation product thereof and (b) a vinyl polymer containing a silyl group having a silicon atom bound to a hydrolytic group and/or a hydroxyl group, and further comprising (c) an oxazoline derivative as a crosslinking agent and a hardened film obtained therefrom. The above coating composition completes the hardening reaction of a coating film at low temperature for a short period of time, high in hardness immediately after hardening, and having water resistance, weather resistance, organic chemical resistance, acid resistance, alkali resistance, wear resistance and durable adhesion.

Abstract: Elastomer-modified Epoxy-polysiloxane compositions of this invention are prepared by combining a silicone intermediate, with an epoxy resin, an elastomeric resinous intermediate, a polyfunctional amine, an optional organometallic catalyst, and optional fillers, pigments, and processing agents. The composition is prepared using a sufficient amount of water to promote hydrolysis of the polysiloxane and the polycondensation of the silanols produced by such hydrolysis. In its cured form, the epoxy-polysiloxane composition exists as a uniformly dispersed arrangement of linear epoxy chain fragments that are cross-linked with a continuous polysiloxane polymer chain, wherein either or both of the epoxy and/or polysiloxane polymers are elastomer modified to provide coatings and floorings having significantly improved properties of impact resistance, flexibility, crack resistance, and abrasion resistance with compared to conventional epoxy systems.

Abstract: A coating composition having (A) an alcohol dispersion which includes silica having the hydrophobic surface and dispersed in an alcohol dispersion medium, the content of silica in a solid substance being 80% by weight or more; (B) a solution including a silicone oligomer which is obtained by a reaction of an alkoxysilane with water and has an average structural unit represented by R1nSiOx/2(OH)y (OR2)z (R1 representing an alkyl group, phenyl group or vinyl group, R2 representing an alkyl group and n, x, y and z representing numbers satisfying relations: 0.8≦n≦1.7, 2<x<3.2, y>0, z>0 and y+z=4−n−x); and (C) a curing agent. The coating composition exhibits excellent storage stability after the curing agent is added, suppresses aggregation of fine silica particles in spray coating and provides coating films having a high hardness and exhibiting excellent weatherability, water resistance, chemical resistance and adhesion.

Abstract: Described is the use of nanoscale metal oxide particles as catalysts for the thermal and/or photochemical polymerization of species having at least one polymerizable carbon-carbon multiple bond and/or at least one carbon containing ring capable of undergoing a ring opening polymerization.

Abstract: Disclosed is a method of preparation of a siloxane-functionalized high 1,4-cis polybutadiene using a siloxane compound, in which the siloxane group expands the usage of the high 1,4-cis polybutadiene.

Abstract: A process for producing a solution of a silicone oligomer which comprises adding to an alkoxysilane, as a self-catalyst, a solution comprising a silicon compound which is soluble in hydrophilic solvents and has an average structural unit represented by R1nSiOx/2(OH)y(OR2)z, wherein R1 represents an alkyl group having 1 to 3 carbon atoms, vinyl group or phenyl group, a plurality of R1 may represent a same group or different groups, R2 represents an alkyl group having 1 to 3 carbon atoms, a plurality of R2 may represent a same group or different groups and n, x, y and z represent numbers satisfying relations: 0≦n<3, 0<x<4, y>0, z≧0 and y+z=4−n−x, and hydrolyzing and polycondensing the alkoxysilane; and a film of an organopolysiloxane formed from the solution of a silicone oligomer.

Abstract: A polyorganosiloxane compound obtained by allowing a polyorganosiloxane having silicone resin structure to react with a polyorganosiloxane having silicone oil structure in the presence of a hydrosilylation catalyst, and having the both structures in the molecule. Also disclosed is a coating composition including the polyorganosiloxane compound, a silane or silicone resin having an RO—Si group, and a curing catalyst. The former polyorganosiloxane compound is compatible with silicone resins. The latter coating composition can provide coatings improved in flexibility without lowering the curability, surface hardness and weatherability inherent in silicone resins.

Abstract: The present invention relates to a highly regular and well-defined ladder structured polyorganosilsesquioxane with superior heat resistance, combustion resistance and flexibility. This product is made by alternatingly bonding together two kinds of substituents. The polyorganosilsesquioxane prepared according to the present invention has a small molecular weight distribution and a high molecular weight. It is soluble in organic solvents because its three-dimensional network structure is not formed as a result of a condensation polymerization, which resulted in a product having structure defect(s) and randomness because of the oligomer that was previously used as a starting material for polymerization. Polyalkylaromaticsilsesquioxanes obtained according to the preparing method of the present invention are useful, heat-resistant materials.

Abstract: Silicone resins having the general formula (R1SiO3/2)x(HSiO3/2)y where R1 is an alkyl group having 8 to 24 carbon atoms; x has a value of 0.05 to 0.7; y has a value of 0.3 to 0.95 and x+y =1. The resins are used to form porous ceramic materials and porous thin films on semiconductor devices.

Abstract: A room temperature rapid-curable silicone composition is provided which includes (A) an organopolysiloxane terminated with hydroxyl groups, having a viscosity of from 25 mPa·s to 1,000,000 mPa·s at 25° C.; (B) a compound selected from the group consisting of a hydrolyzable silane represented by the following general formula (1): RnSiX4−n  (1) wherein R represents a monovalent hydrocarbon group having 1 to 12 carbon atoms; X represents a compound selected from the group consisting of a ketoxime group, an alkoxyl group, an alkenoxyl group and an acyloxyl group; and n represents an integer of 0 to 2, and a partial hydrolysis-condensation product thereof; and (C) a water-containing wet-process silica having an average particle diameter of 100 &mgr;m or smaller, which is a chief source for feeding water necessary for condensation curing reaction.

Abstract: A coating liquid for forming a transparent coating comprising fine particles of an inorganic compound and a hydrolyzate of an organosilicon compound represented by the general formula (I): RnSi(OR′)4−n  (I) wherein R and R′ represent organic groups which may be identical to each other or different from each other, and n is an integer of 1 to 3. This coating liquid ensures excellent substrate wettability and compatibility with various organic solvents so that the printability and applicability thereof are desirable, with the result that a transparent coating film of high uniformity, for example, a flattening coating film, can be formed. The present invention comprises a substrate having a transparent coating film formed on the substrate surface from the above coating liquid.

Abstract: Disclosed is a flame retardant resin composition comprising: 100 parts by weight of a resin component (A) which is a resin mixture of an aromatic polycarbonate and a styrene polymer, wherein the resin mixture has an aromatic polycarbonate content of from 50 to 95% by weight and a styrene polymer content of from 5 to 50% by weight; 0.1 to 30 parts by weight of an organopolysiloxane (B) which comprises 0 to 70 mol % of a monofunctional siloxane unit (M unit), 0 to 100 mol % of a bifunctional recurring siloxane unit (D unit), 0 to 100 mol % of a trifunctional recurring siloxane unit (T unit), and 0 to 63 mol % of a tetrafunctional recurring siloxane unit (Q unit); and 0.0005 to 5 parts by weight of at least one inorganic metal salt (C) selected from the group consisting of inorganic alkali metal salts and inorganic alkaline earth metal salts.

Abstract: The invention discloses a method for the preparation of an organopolysiloxane having a branched molecular structure which comprises the steps of: (A) Mixing (A1) an organopolysiloxane represented by the average unit formula [R13SiO½]m[R1SiO{fraction (3/2)}]n[R1(R2O)SiO]q, in which R1 is a monovalent hydrocarbon group, R2 is a hydrogen atom, methyl group or ethyl group and the subscripts m, n and q are each 0 or a positive number with the proviso that (n+q)/m is from 0.6 to 1.5 and q/(m+n) is 0 or a positive number not exceeding 0.

Abstract: A stretch releasing pressure sensitive adhesive tape includes a silicone pressure sensitive adhesive composition that exhibits a 180° peel strength on a glass substrate at 98% relative humidity of at least about 5.47 N/dm and a non-tacky tab. A stretch releasing pressure sensitive adhesive tape includes a pressure sensitive adhesive composition having a modulus at 1 radian/second and −17° C. of no greater than about 1×107 Pa and a non-tacky tab.

Abstract: Disclosed are silicone polymer based compounds, which include a hydrophobic silicone polymer backbone and a hydrophilic component. The hydrophilic component may act as a chelating agent to bind a metal. The hydrophilic component may be hydrophilic prior to binding with a metal or after binding. Also disclosed are methods of making these compounds. The compounds are useful in a variety of applications.

Abstract: An elastomer system having biocide properties is described, useful, in particular, for dental impressions. An efficient system is provided for destroying microbes, without adversely affecting the crosslinking properties and the mechanical qualities of RTV 2 elastomers. Said system comprises an RTV 2 silicone, preferably SiH/SiVi polyaddition product and a biocide selected among active chlorine precursors, preferably among N-chloramines. The system may include functional additives (silicon fillers, alumina, paraffin, vaseline oil). As for the biocide, it can be provided with an antiseptic auxiliary adjuvant along with EDTA-type sequestering agents.

Abstract: A stain-proofing agent comprising a compound represented by the formula (1): and non-aqueous composition for paints comprising the stain-proofing agent, resin, curing agent and/or curing catalyst and being capable of forming a coating film remarkably excellent in stain-proofing property.

Abstract: The invention is directed to improved conductive adhesives for solder-free interconnections in microelectronic assembly processes such as for chip carrier-to-substrate attachment. These adhesives are characterized by low tensile modulus, low resistivity, high adhesion strength, and durability of these properties during reliability stress conditions of thermal shock, thermal aging, and temperature/humidity (85° C./85%) exposure of the assembled devices. The adhesives contain a homogeneous solution of a siloxane containing epoxide, a curing agent, a curing catalyst and an organic polymeric or oligomeric additive. A conductive filler is added to the solution forming the filler. Preferred fillers are Ag coated with Pd and Ag coated with Au.

Abstract: Symmetric and asymmetric cyclic silalkylenesiloxane monomers and copolymers thereof, as well as crosslinked and/or reinforced silalkylenesiloxane copolymers, medical devices containing such materials, and methods of preparation.

Abstract: There is disclosed a method for the preparation of a diene polymer interpenetrated with a polysiloxane comprising the polymerization of (A) at least one silane monomer of the formula: (B) at least one silane monomer of the formula: (C) at least one diene monomer, said polymerization being conducted in the presence of an anionic base, an inert solvent and a polymerization initiator, wherein each R1 is independently selected from the group consisting of alkyl radicals having from 1 to 4 carbon atoms and aryl radicals having 6 carbon atoms and R2 is selected from the group consisting of where x is an integer of from 1 to 8.

Abstract: A polyorganosiloxane containing the units (HR2Si—O1/2) HM units, (Si—O4/2) Q units, (R1Si—O3/2) T units and (R2Si—O2/2) D units in a ratio of from 2:1:0:0 to 6:4:2:2, or (HR2Si—O1/2) HM units, (R1Si—O3/2) T units, (R2Si—O2/2) D units and (R2(R1O)Si—O1/2) in a ratio HM:T:D:alkoxyM of from 1:2:0:0 to 3:4:2:2 is described, where R are identical or different, non-halogenated or halogenated hydrocarbon radicals having from 1 to 18 carbon atoms per radical, or are OR1, where R1 is a monovalent, unsubstituted or substituted hydrocarbon radical having from 1 to 8 carbon atoms, and in each molecule there are at least 3 Si-bonded hydrogen atoms. The polyorganosiloxanes are particularly useful as crosslinking agents in addition curable elastomer formulations.