164 results about "Percolation threshold" patented technology

An optical sensing enhancing material (and corresponding method of making) comprising: a medium, the medium comprising a plurality of aggregated nanoparticles comprising fractals; and a microcavity, wherein the medium is located in a vicinity of the microcavity. Also an optical sensor and sensing method comprising: providing a doped medium, the medium comprising a plurality of aggregated nanoparticles comprising fractals, with the material; locating the doped medium in the vicinity of a microcavity; exciting the doped medium with a light source; and detecting light reflected from the doped medium. Also an optical sensing enhancing material comprising a medium, the medium comprising a semicontinuous metal film of randomly distributed metal particles and their clusters at approximately their percolation threshold. The medium preferably additionally comprises a microcavity/microresonator. Also devices and methods employing such material.

The invention discloses a dynamic polymer elastomer with a hybrid cross-linked network. The elastomer comprises the hybrid crosslinked network, and the hybrid crosslinked network contains covalent crosslinking and supermolecular hydrogen bond crosslinking, wherein the covalent crosslinking achieves a percolation threshold or more of a covalent cross-linked gel, and the hydrogen bond crosslinking is realized through hydrogen bond groups brought by polymer chain side groups and/or side chains. According to the invention, hydrogen bonds are dynamically reversible, thus the dynamic polymer elastomer has good performance such as toughness, energy dissipation performance, and self repairability. The dynamic polymer elastomer with the hybrid cross-linked network is widely applied to aspects suchas body protection in sports and daily life and work, military police body protection, explosion protection, airborne and air-drop protection, automotive collision avoidance, and electronic material impact resistant protection.

The invention relates to a method for preparing a polyethylene/graphene conductive composite material, and belongs to the technical field of preparation of composite conductive polymer materials. The method comprises the following steps of: putting graphite oxide into a solvent consisting of water and ethanol, performing ultrasonic dispersion, adding polyethylene powder, and performing mechanicalstirring; evaporating the solvent, and drying in vacuum to remove the residual solvent so as to obtain core-shell structured composite particles in which the polyethylene powder is coated with a layer of graphene oxide; and adding the core-shell structured composite particles into a hydrazine hydrate solution, heating and stirring, and reducing the graphene oxide on polymer into graphene so as toobtain the powdered polyethylene/graphene conductive composite material. By the method, the graphene oxide can be effectively and uniformly coated on the surface of the polymer; the graphene does notfall into the solution in the reduction process, and the agglomeration of a final product, namely the graphene is effectively reduced; and a platy composite material prepared by hot pressing has a low percolation threshold value and high electric conductivity.

The present invention relates to a kind of nanometer conductive composite polyamide/graphite material and its preparation process. The nanometer conductive composite material consists of polyamide as main base 100 weight portions, auxiliary base 5-60 weight portions, and graphite 2-40 weight portions. It has relatively low percolation threshold, 3-4 %, and relatively high conductivity. Owing to the filled conductive material in relative small amount, the nanometer conductive composite material has excellent mechanical performance and processability similar to that of nylon and high electrostatic resistance, so that it is wide application foreground in electrostatic resisting material, electromagnetic shielding material, microwave absorbing material, etc.

The invention discloses a carbon nanotube/polylactic acid conductive composite material and a preparation method; the conductive composite material comprises the following blended components: levorotatory polylactic acid resin, and dextrorotatory polylactic acid resin, carbon nanotube and an anti-oxidant; the using amount of the carbon nanotube is 0.2-3 parts by weight; the weight ratio of the levorotatory polylactic acid resin and the dextrorotatory polylactic acid resin is (80-50):(20-50). The method comprises the following steps: performing melt blending of the levorotatory polylactic acid resin, the carbon nanotube, and the anti-oxidant according to the using amounts to prepare a master batch, then performing melt blending with the dextrorotatory polylactic acid resin to prepare the carbon nanotube/polylactic acid conductive composite material. The conductive composite material of the invention is added with a few CNTs, and thus the material is provided with good conductivity; the conductive percolation threshold is significantly reduced to 0.5 wt%; the operation process is simple, and is suitable for continuous mass production.

The invention discloses a conductive polyester/graphite oxide composite material and a preparation method thereof. The composite material is prepared from the following raw materials in part by mass: 0.25 to 10 parts of graphite oxide, 100 parts of terephthalic acid or ester thereof, 60 to 200 parts of alkaline glycol, 0.01 to 3 parts of catalyst, 0.01 to 0.5 part of stabilizing agent and 0 to 100 parts of dispersant. The polyester/graphite oxide composite material of the invention is prepared by polymerizing a polyester substrate and a nano-graphite packing in situ, has the percolation threshold of 0.5 to 1.0 weight percent, can achieve the electric conductivity of 10 to 5 S/cm when graphite content is 3.5 weight percent, and compared with a conventional natural graphite conductive composite material and an expanded graphite conductive composite material, can achieve the high properties of low packing amount and high electric conductivity without adding an auxiliary substrate, and can be widely applied in the fields of conductive materials, antistatic materials, electromagnetic shielding materials, microwave absorption and the like.

The present invention discloses nanometer conducting polyamide/graphite composite material and its preparation process. The nanometer conducting polyamide/graphite composite material is prepared through the following steps: soaking 30-200 mesh natural scale graphite powder in mixed liquid of concentrated sulfuric acid and concentrated nitric acid in the weight ratio of 4 to 1 for 24 hr, water washing, drying and heating at 900-1100 deg.c in a muffle furnace to obtain expandable graphite of expansion ratio over 200; dissolving polyamide resin in 90-99 weight portions in some solvent, adding the expandable graphite in 1-10 weight portions, ultrasonically dispersing for 2 hr, adding precipitant while stirring, suction filtering the precipitate and drying to obtain the composite material. The composite material with relatively low percolation threshold and high conductivity may be applied as antistatic material, electromagnetic shielding material, etc.

The invention which discloses a composite medium film material based on polyvinylidene fluoride and graphene, and a preparation method thereof belongs to the technical field of electric functional materials. The composite medium film is obtained through compounding polyvinylidene fluoride and graphene, wherein the graphene mass percent content is 0.5-3% of the mass of the composite medium film. The preparation method comprises the following steps: preparing an organic solution (a system A) of polyvinylidene fluoride powder; adding graphene powder to the system A to obtain a system B; spraying the system B on the surface of a substrate through adopting an ultrasonic atomization technology; and drying the system B sprayed on the surface of the substrate to obtain the composite medium film material based on the polyvinylidene fluoride and the graphene. According to the invention, the graphene which approaches and does not exceed a percolation threshold is added to a polyvinylidene fluoride film to obtain the composite medium film material with the dielectric constant 100% higher than that of the pure polyvinylidene fluoride film material, and the original flexibility and the easy processability are maintained; and the preparation method has the advantages of simplicity, easy control and low cost.

The invention belongs to the technical field of manufacturing of conductive polymer composites, and in particular relates to a preparation method of a conductive polymer composite with negative temperature coefficient (NTC) characteristics. The invention discloses a polymer based temperature-sensitive resistance material with a NTC effect, and the polymer based temperature-sensitive resistance material comprises the following raw materials in parts by weight: 88.5-96.9 parts of a polymer 1 and a polymer 2, 0.1-1.5 parts of a conductive filler and 3-10 parts of a compatilizer; moreover, the conductive filler is selectively distributed in the polymer 2; the MFI of the polymer 1 is less than or equal to 7g/10 minutes, and the MFI of the polymer 2 is more than or equal to 12g/10 minutes; the thermal expansion coefficient of the polymer 2 is greater than that of the polymer 1, and the conductive filler is a two-dimensional conductive filler; and the mass ratio of the polymer 1 to the polymer 2 is (3:7)-(7:3). The resistance material prepared by the method disclosed by the invention is low in percolation threshold, the NTC characteristic repeatability of the obtained resistance material is good, and the resistance material is convenient to use for a long time.

The invention provides a conductive polymer composite and a preparation method thereof. The conductive polymer composite comprises 100 parts by weight of matrix and 0.01-1.5 parts by weight of conductive nanofiller, wherein the matrix is an incompatible polymer blend system with dual-continuous structure, and the length-diameter ratio of the conductive nanofiller is greater than or equal to 100. Compared with a conductive fibering polymer composite prepared from carbon black, polyethylene and polyethylene terephthalate in the prior art, the conductive polymer composite has the advantages that firstly, the length-diameter ratio of the conductive nanofiller adopted in the conductive polymer composite is larger, so that the insulated polymer can conduct electricity by few addition of the conductive nanofiller, thus the conductive percolation threshold of the conductive polymer composite is reduced; secondly, the matrix of the dual-continuous structure and the conductive polymer nanofiller are distributed on a two-phase interface of the incompatible polymer blend system with the dual-continuous structure, so that the conductive percolation threshold of the conductive polymer composite is reduced; and finally, the preparation method provided by the invention is simple, safe and environment-friendly.

A strain sensor consisting of a non conducting polymer incorporating conductive nanoparticles below the percolation threshold and preferably less than 10% v/v of the polymer. The polymer is a polyimide and the conducting nanoparticle is carbon black having an average particle size of 30-40 nm and an aggregate size of 100-200 nm. The sensor can sense strain in extension, compression and torsion.

The invention relates to a preparation method of a graphene/silicon rubber pressure-sensitive conductive composite and belongs to the technical field of composite preparation. The preparation method comprises the following steps: dispersing the graphene used as a packing into a silicon rubber matrix by using an ultrasonic-assisted solution mixing method, and furthermore, preparing the graphene/silicon rubber pressure-sensitive conductive composite by using a high-temperature sulphidization method. The graphene has a high diameter-thickness ratio, and a conductive network can be formed in silicon rubber by using a relatively small quantity of graphene through the ultrasonic-assisted solution mixing and high-temperature sulphidization methods, so that the percolation threshold of the graphene/silicon rubber composite is relatively low; in addition, the system is sensitive to pressure so as to achieve a remarkable positive piezoresistive effect. The composite provided by the invention is widely applied to the fields of antistatic rubber, electromagnetic shielding products and pressure sensors.

A high-sensitivity pressure conduction sensor is presented. The present invention includes a pair of locally resilient conductive layers and a locally resilient pressure conduction composite disposed between and contacting both conductive layers. Alternate embodiments include at least three locally resilient conductive layers and at least two locally resilient pressure conduction composites, each having a critical percolation threshold. Each composite is disposed between and contacting two conductive layers in a multi-layer fashion. Other embodiments include a locally resilient pressure conduction composite, a flexible substrate completely surrounding the composite so as to seal it therein, and a pair of electrical leads contacting the composite and terminating outside of the flexible substrate. Pressure conduction composites are composed of a plurality of conductive particles electrically isolated within a non-conductive matrix. Conductive particles are loaded so as to have a volume fraction approaching the critical percolation threshold of the material system and exhibit a conductance that greatly increases with pressure. Sensors may be arranged to form one or more arrays including planar and conformal configurations. The present invention has immediate application in keyboards, intrusion systems, control systems, submarines, ships, sonobuoys, doors, and switches.

The invention discloses a conductive and antistatic nylon which adopts polyamide resin as basic material and adds nano inorganic filling material, conductive carbon black, a lubricating agent, a surface processing agent and an antioxidant and the like; the part by weight ratio of all the components is as follows: 60 parts to 98 parts of polyamide resin, 1 part to 15 parts of nano inorganic filling material, 5 parts to 30 parts of conductive carbon black, 0.1 part to 1.0 part of lubricating agent, 0.1 part to 1.0 part of surface processing agent and 0.1 part to 0.5 part of antioxidant; the invention adds the conductive carbon black in the polyamide resin to improve the conductive effect of the material, reduces the using amount of the carbon black under the premise of guaranteeing the same conductivity and antistatic electricity and effectively improves the cost performance of the material, effectively improves the dispersion of the carbon black, and reduces the 'percolation threshold' of plastic; and the nano material is added into the nylon and has the effect of a nucleating agent, which has obvious strengthening and toughening effects to matrix resin and improves the comprehensive performance of the product.

The presently described embodiments provide electric paper, in one form, that is bisymmetrical, both sides of the paper have the same thicknesses of mylar layers and the same thicknesses and patterns of ITO islands. In another form, a disordered layer of conductive particles, non-conductive particles and display elements has the same percolation threshold throughout, and thus is bisymmetrical. In either form, in a system for printing all asymmetries in the printing process are transferred to the printhead, just like in conventional ink printers and paper. As a result, both sides of the electric paper are equally capable of being printed on, just like conventional paper, and the electric paper has the same flexural properties when flexed in a concave or convex manner, just like conventional paper. This construction has the additional practical advantage that there is no longer any need to ensure the electric paper is oriented “right side up” before printing on it. These improvements all make electric paper more paper-like in feel and use.

The invention discloses a polymer matrix composite material with high PTC strength and stability and a preparation method thereof, and the composite material comprises UHMWPE and PVDF, CB and MWNT conductive filling materials which are treated by surface treatment by a titanate coupling agent, and an antioxidant 1010; the preparation method comprises the following steps: performing surface treatment of the CB and MWNT conductive filling materials by the titanate coupling agent, performing vacuum drying of PVDF and UHMWPE with a volume ratio of 1:1, adding PVDF into a torque rheometer, heating and melting for 2 min, adding another matrix of UHMWPE and the antioxidant 1010, wherein the amount of the antioxidant 1010 is 1% of the total mass of the matrix; mixing the mixture of the two matrixes for 10 min, adding the filling materials, mixing at 250 DEG C for 15 min; after melt blending, performing hot pressing with a constant temperature of 250 DEG C and a constant pressure of 18 MPa for 10 min to obtain the sample. The composite material of the invention has good conductivity and low room-temperature conductivity, and has a conductivity of up to 10-1 near a percolation threshold; the conductivity of the composite material can be changed by adjusting the contents of the filling materials in the composite material; the composite material has high PTC strength, good repetition stability, and reduced NTC effect.

The invention discloses a conductive composite material and a manufacturing method and an application thereof, comprising a second polymer and the conductive composite which is combined with the second polymer and is provided with continuous phase, the conductive composite is composed of a first polymer and conductive filler which is contained in the first polymer and forms a conductive network, fusion temperature of the second polymer is higher than the fusion temperature of the first polymer, the invention adopts the manufacturing methods of stretching and heat treatment, so that the conductive composite material has relatively low percolation threshold after processing and forming, in addition, in the process of the processing, the conductive composite material can still maintain most of the mechanical properties after the heat treatment at relatively high temperature, thus ensuring that the whole material has fine conductivity and mechanical properties and can be applied to anti-static products, electromagnetic shielding products or circuits. The invention features easy operation of the manufacturing method, good universality and relatively easy recovery of the conductive composite material, in addition, the invention eliminates the problem in the prior art that the recovery of the composite material is difficult as the high strength fiber is added to the composite material to increase strength of the composite material.

The invention discloses a graphene-containing composite material as well as a preparation method and application thereof. The graphene-containing composite material comprises a composite functional material with a double-conductive channel and a polymer matrix, wherein the composite functional material with the double-conductive channel is sulfonated graphene surface grafted conductive polymer poly-3,4-(ethylenedioxythiophene), and the structure formula is as shown in formula I in the specification. The composite functional material with the double-conductive channel and the graphene-containing composite material can be used for preparing a piezoresistance response material, or an antistatic or electromagnetic shielding material and the like and have excellent piezoresistance response, piezoresistance repeatability and electromagnetic shielding effect. The graphene-containing composite material is simple and easy to operate, can be prepared in large scale and has excellent piezoresistance performance and sensitive piezoresistance response, the percolation threshold is 0.5Wt%, original performance of the polymer can be maintained, and an unstable conductive network system can be formed to be beneficial to improving the sensitivity of piezoresistance response.

The invention aims to propose a preparation method of a graphene/polystyrene conductive composite material. A kind of preparation method of graphene/polystyrene conductive composite material, adopt following steps: Step 1: the preparation of graphene oxide (GO) powder; Step 2: dispersion polymerization prepares cationic polystyrene (PS+) microsphere; Step 3 : Preparation of GNS/PS composites. The invention can inhibit the self-aggregation and induction of GNs and the selective distribution of graphene on the surface of polymer particles, forming a perfect three-dimensional graphene network skeleton; the relatively ordered three-dimensional structure of GNs constitutes a free electron conduction path, and GNs/ The PS composite material exhibited extremely low conductive percolation value and high conductivity; the addition of graphene improved the thermal stability of PS, and the decomposition temperature of PS increased by 13.5 °C. This facile method provides a new idea for the construction of ordered inorganic filler microstructures in high-viscosity polymer systems, which is conducive to further expanding the application field of graphene-based conductive composites.