384 results about "Precursor polymer" patented technology

Apparatus and methods are provided for sealing a puncture extending through tissue to a blood vessel. A delivery sheath is introduced-into the puncture, and a sealing compound, e.g., precursor polymers that mix to create a hydrogel, is introduced through the delivery sheath into the puncture. The delivery sheath is then removed, an introducer sheath is advanced through the puncture into the vessel, and instruments are introduced through the introducer sheath into the vessel to perform a medical procedure. After completing the procedure, the introducer sheath is withdrawn. The sealing compound may expand into the puncture and/or tissue recoil of the surrounding tissue may cause the sealing compound to at least partially occlude the puncture to facilitate sealing and/or hemostasis.

A radiation-sensitive composition and negative-working imageable element includes a polymeric binder comprising pendant allyl ester groups to provide solvent resistance, excellent digital speed (sensitivity) and can be imaged and developed without a preheat step to provide lithographic printing plates. The polymeric binder can be prepared with a precursor polymer having pendant carboxy groups that are converted to allyl ester groups using an allyl-containing halide in the presence of a base in order to avoid gelation.

A heat resistant negative working photosensitive composition that comprises

• • (a) one or more polybenzoxazole precursor polymers (I):
  • wherein x is an integer from about 10 to about 1000, y is an integer from 0 to about 900 and (x+y) is about less then 1000; Ar¹ is selected from the group consisting of a tetravalent aromatic group, a tetravalent heterocyclic group, or mixtures thereof; Ar² is selected from the group consisting a divalent aromatic, a divalent heterocyclic, a divalent alicyclic, a divalent aliphatic group that may contain silicon, or mixtures thereof; Ar³ is selected from the group consisting a divalent aromatic group, a divalent aliphatic group, a divalent heterocyclic group, or mixtures thereof; Ar⁴ is selected from the group consisting Ar¹ (OH)₂ or Ar²; G is an organic group selected from the group consisting groups having a carbonyl, carbonyloxy or sulfonyl group attached directly to the terminal NH group of the polymer;
  • (b) one or more photo-active compounds which release acid upon irradiation (PAGs);
  • (c) a latent crosslinker which contains at least two ˜N—(CH₂OR)_n units wherein n=1 or 2 and R is a linear or branched C₁-C₈ alkyl group, with the proviso that when a glycoluril is employed as the latent crosslinker, the G group in the polybenzoxazole precursor polymer is produced from the reaction of a cyclic anhydride; and
  • (d) at least one solvent that is not NMP.

A liquid composition is applied onto the surface of the part to be treated, the composition containing a ceramic precursor polymer and a refractory solid filler. After cross-linking, the polymer is transformed into ceramic by heat treatment, and subsequently ceramic is deposited by chemical vapor infiltration. Before the chemical vapor infiltration step, the surface of the part is shaved so as to return the composite part to its initial shape so that the chemical vapor infiltration forms a deposit that fills in the residual micropores in the shaved surface of the part.

The present invention is made to provide a carbon catalyst capable of preventing the coarsening of particles of nanoshell structure of carbon which causes reduction in activity for oxygen reduction reaction. The carbon catalyst is produced by the steps of: preparing a carbon precursor polymer; mixing a transition metal or a compound of the transition metal into the carbon precursor polymer; spinning the mixture of the carbon precursor polymer and the transition metal or the compound of the transition metal into fibers; and carbonizing the fibers.

This invention describes a new concept of flexible template-directed microporous partially pyrolyzed polymeric membranes which have greatly improved performance in separation of gas pairs compared to their precursor polymeric membranes. Organic hosts, such as crown ethers, cyclodextrins (CDs), calixarenes (CXs), and spherands, or polymeric additives, such as poly(ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were used as the micropore-forming templates. Micropore-forming template/polymer blend membranes comprising organic micropore-forming templates embedded in a polymer matrix were prepared by dissolving the organic micropore-forming templates in the polymer solution followed by solution-casting and solvent evaporation or solvent exchange. Low-temperature selectively pyrolyzing micropore-forming templates in the micropore-forming template/polymer blend membranes at a nitrogen flow resulted in the formation of flexible microporous partially pyrolyzed polymeric membranes.

A method for reducing peeling of a cross-linked polymer passivation layer in a solder bump formation process including providing a multi-level semiconductor device formed on a semiconductor process wafer having an uppermost surface comprising a metal bonding pad in electrical communication with underlying device levels; forming a layer of resinous pre-cursor polymeric material over the process surface said resinous polymeric material having a glass transition temperature (Tg) upon curing; subjecting the semiconductor process wafer to a pre-curing thermal treatment temperature below Tg for a period of time; and, subjecting the semiconductor process wafer to at least one subsequent thermal treatment temperature above Tg for a period of time to form an uppermost passivation layer.

The invention provides a Cellulose acetate (CA) thin, porous membranes produced by electrospinning precursor polymer solutions in acetone at room temperature and a process for manufacturing the same. The invention also provides a Cellulose acetate (CA) thin, porous membranes produced by electrospinning precursor polymer solutions in acetone at room temperature further comprising ceramic nano-structured component (carbon nanotubes) in the polymer membranes to provide additional strength and porosity and a process for manufacturing the same. The fabricated CA-CT membranes specifically mimic the topography and porosity of natural Extracellular Matrix (ECM) and can be used as scaffolding for cell growth.

The invention discloses a preparation method of a porous silicon carbide nanofiber. The preparation method comprises the following steps of: (1) preparing a carbon nanofiber precursor polymer spinning solution; (2) performing electrostatic spinning to prepare a polymer nanofiber; (3) carrying out pre-oxidization crosslinking on the polymer nanofiber; (4) carrying out high-temperature firing on the pre-oxidized polymer nanofiber to prepare a carbon nanofiber; and (5) carrying out carbon thermal reduction on the carbon nanofiber and silicon powder to obtain the porous silicon carbide nanofiber. According to the preparation method, the morphology, the diameter and the ordering of the obtained silicon carbide nanofiber can be effectively regulated and controlled through simple means; the production cycle is relatively short so that expanded production can be conveniently realized and the preparation process is simple so that the industrial production can be conveniently realized; the porous silicon carbide nanofiber has wide application prospect in the fields of high-temperature filtration, high-temperature catalysis, catalyst carriers, heat insulation and sound insulation, gas separation, chemical sensors and the like.

A method for fabricating an ultra-sensitive metal oxide gas sensor is disclosed, which comprises the steps of spinning a mixture solution including a metal oxide precursor and a polymer onto a sensor electrode to form a metal oxide precursor-polymer composite fiber; thermally compressing or thermally pressurizing the composite fiber; and thermally treating the thermally compressed or thermally pressurized composite fiber to remove the polymer from the composite fiber. Since the gas sensor includes a macro pore between nanofibers and a meso pore between nano-rods and/or nano-grains, gas diffusion and surface area can be maximized. Also, the ultra-sensitive sensor having high stability in view of mechanical, thermal, and electrical aspects can be obtained through rapid increase of adhesion between the metal oxide thin layer and the sensor electrode.

The present invention relates to a continuous, carbon fiber with nanoscale features comprising carbon and carbon nanotubes, wherein the nanotubes are substantially aligned along a longitudinal axis of the fiber. Also provided is a polyacrylonitrile (PAN) precursor including about 50% to about 99.9% by weight of a melt-spinnable PAN and about 0.01% to about 10% of carbon nanotubes. Other precursor materials such as polyphenylene sulfide, pitch and solution-spinnable PAN are also provided. The precursor can also include a fugitive polymer which is dissociable from the precursor polymer.

A synthesis method of polycarbosilane capable of being used for thermosetting crosslinking comprises the following steps: taking polycarbosilane used for preparing a composite material as a raw material; placing the polycarbosilane used for preparing the composite material and an organosilan compound containing 2 to 3 -C=C- groups into a reaction vessel; adding dimethyl benzene; mixing uniformly for dissolving; adding a Si-H additive reaction catalyst; vacuumizing; carrying out replacing with high-purity nitrogen; carrying out an Si-H additive reaction under a normal-pressure or high-pressure heating condition and the protection of the high-purity nitrogen. The synthesis method is simple and convenient, and easy to implement; the product PVCS can be used for self-setting crosslinking under an inert atmosphere after being treated at 400 DEG C; the smelting outflow of PCS during heat treatment can be avoided; the ceramic yield can be improved remarkably; the polycarbosilane synthesized according to the synthesize method can be used as a precursor polymer of ceramic-based composite materials such as Cf/SiC, and SiCf/SiC.

The invention provides a method for preparing a composite ceramic material through utilizing ceramic and a precursor. The method comprises the steps that (1) ceramic powder and the precursor are mixed uniformly; (2) the mixture material is solidified, wherein the solidifying temperature is between 120 and 500 DEG C, and the thermal insulation time is between 0.5 and 10 hours; (3) the solidified product is subjected to die pressing so as to preform a body, and then, the body is further densified through isostatic pressing; (4) the body is subjected to net final dimension processing through adopting a mechanical processing mode; and (5) the processed product is sintered in a sintering furnace, so that the composite ceramic product is finally obtained, wherein the sintering pressure is between 100 pascals and 10 mega pascals, the sintering temperature is between 1600 and 2200 DEG C, and the sintering time is between 0.5 and 10 hours. A precursor polymer has plasticity and plays a role of a 'plasticizer' during the body forming process; and moreover, the 'plasticizer' can be directly converted into a component which is required by composite ceramic through cracking during the subsequent high-temperature processes, other impurities cannot be brought in, and the dispersion of all the components can be effectively improved.

The invention provides a graphene/carbon nano tube/carbon nanofiber electrocatalyst and a preparation method thereof. The electrocatalyst is prepared with the method comprising steps as follows: (1), spinning solution preparation: transition metal salt, a carbon nanofiber precursor polymer and a solvent are mixed uniformly, and a homogeneous spinning solution is obtained; (2), electrospinning: the homogeneous spinning solution is used for electrospinning, fibril felt is obtained; (3), pre-oxidation: the fibril felt is pre-oxidized in an air atmosphere, and pre-oxidized fiber felt is obtained; (4), pyrolysis: the pre-oxidized fiber felt is mixed uniformly with a graphite-phase carbon nitride precursor and graphite-phase carbon nitride and pyrolyzed in an inert atmosphere, and the graphene/carbon nano tube/carbon nanofiber electrocatalyst is obtained. The electrocatalyst has high electrical conductivity, many favorable active sites, good oxygen reduction electrocatalysis performance and better electrocatalysis performance, can be widely applied to the fields of super capacitors, cathode catalysis of fuel cells and the like; the preparation method is simple and large-scale production can be realized.

The invention relates to a method for preparing activated carbon. The method comprises the following steps of: weighing one of soluble phenolic resin, furfuryl alcohol resin, polyacrylonitrile and soluble starch, a carbon precursor polymer and one pore-forming agent of polyethylene glycol, polyvinyl alcohol and polyvinyl butyral, mixing, and adding one of methanol, ethanol and deionized water as a solvent for dissolution; and weighing the activated carbon raw material, adding into the solution for dipping, then drying, and carbonizing in a microwave high-temperature sintering furnace at the temperature of 500-1100 DEG C in a nitrogen atmosphere for 0.5-24h. According to the method for preparing activated carbon, provided by the invention, an activated carbon product prepared by the method has abrasion resistance and micropore porosity which are equivalent to those of the raw material activated carbon; and furthermore, the mesopore porosity is further increased in comparison with the raw material activated carbon, and the activated carbon has the advantages of double aperture distribution, large specific surface area and high abrasion resistance, and can meet the application requirements under specific conditions.

The invention relates to a method for preparing silicon carbide and precursor composite fibers. A silicon carbide precursor polymer is dissolved in at least one organic solvent to form uniform oil phase solution with the mass fraction of 10-70%; a water-soluble fiber-forming polymer is dissolved in water, surfactants are added, uniform water phase solution with the mass fraction of 1-50% is formed, and the quantity of the surfactants is 0.1-10% of the mass of the solution; the precursor solution and the water-soluble polymer solution are mixed according to the volume ratio of 1:10-1:1 to obtain stable oil-in-water (O/W) spinning solution; spinning precursor fibers with the spinning solution by a solution jet spinning method to obtain a precursor composite fiber with the diameter ranging from 50 nanometers to 50 micrometers; and the precursor fibers are not melted and calcined at high temperature to obtain silicon carbide fibers. The method has the advantages of high production efficiency, simple process, uniformity of fiber diameter distribution and the like, and is suitable for large-scale production.