962 results about "Phenyl sulfide" patented technology

The invention provides a supported polyphenylene sulfide (PPS) filter material which belongs to the field of filter materials. The supported PPS filter material is prepared by the following method: making a PPS fiber into a PPS filter material; performing water bath acidification in nitric acid, and washing with deionized water to neutrality; drying to obtain acidified polyphenylene sulfide nitride (PPSN); preparing a catalyst into a solution and stirring; soaking PPSN in the solution; performing water bath baking, and drying in air; and calcining in a nitrogen atmosphere to obtain the supported PPS filter material with denitration function. The denitration-catalyst-supported PPS filter material provided by the invention can be used as a dedusting agent and a denitration agent at the sametime, is prepared by simple steps, realizes dedusting and denitration functions as well, and has the advantages of high denitration rate, high temperature resistance, acid-base resistance, good waterresistance, long service life and the like; and a new application field of the filter-bag catalytic denitration is created.

The invention discloses a polyphenylene sulfide composite material which comprises the following components in percentage by weight: 10-40 percent of polyphenylene sulfide, 10-40 percent of polyamide, 5-30 percent of glass fiber, 5-20 percent of compatilizer, 0.2-1.5 percent of coupling agent, 0-1 percent of antioxidant, 0-1 percent of light stabilizer and 0-1 percent of processing aid. The method for preparing the polyphenylene sulfide composite material comprises the following steps: preparing various raw materials; sequentially adding polyphenylene sulfide, polyamide, the compatilizer, the coupling agent, the antioxidant, the light stabilizer and the processing aid into a high-speed mixer for dispersing and mixing; putting the mixed materials into an extruder after mixing is finished, independently introducing the glass fiber through a glass fiber port of the extruder during extrusion, and mixing, extruding and pelleting the materials to obtain granules of the polyphenylene sulfide composite material. The provided polyphenylene sulfide composite material has high rigidity, strength and toughness and can be widely applied to the fields of aerospace and aviation, chemical industry, electronic products, machinery, automobiles and railways.

The invention discloses a wear-resistant and high-toughness polyphenylene sulfide composite material and a preparation method thereof. The composite material is composed of the following components of, by weight, 30-75 parts of polyphenylene sulfide, 20-50 parts of glass fibre, 5-20 parts of carbon fiber, 5-30 parts of a toughening agent, 0-20 parts of polytetrafluoroethylene, 0-20 parts of an ultrahigh molecular weight polyethylene, 2-10 parts of molybdenum disulfide, 0.2-1.5 parts of a coupling agent, 0.2-1 part of an antioxidant, 0.1-0.5 part of a light stability agent and 0.2-2 parts of a processing auxiliary agent. The composite material has a series of outstanding advantages of excellent low-temperature impact performance, high strength, high modulus, high heat stability, easy processing and molding, and the like, and has wide application fields such as automobiles, aeronautics and astronautics, etc.

The invention discloses a polyphenylene sulfide composite material and a preparation method thereof. The polyphenylene sulfide composite material comprises, by weight, 10-40 parts of polyphenylene sulfide, 10-40 parts of polyamide, 5-25 parts of carbon fibers, 10-50 parts of packings, 5-20 parts of compatilizers, 0.2-1.5 parts of coupling agents, 0-1 part of antioxidants, 0-1 part of light stabilizers and 0-1 parts of processing additives. The polyphenylene sulfide composite material prepared by the method has advantages of excellent heat and electric conductivity, high strength, high modulus, high stability, easiness in processing and forming and the like, is wide in application range including fields of electronics and electrics, automobiles, aerospace and the like.

The present invention relates to polymer compositions containing polyphenylene sulfide, a polymeric grafting agent and an ethylene copolymer. The polymeric grafting agent is a copolymer of at least about 50% by weight ethylene, about 0.5% to about 15% by weight of a first reactive moiety selected from the group consisting of: (i) an unsaturated epoxide of 4-11 carbon atoms, (ii) an unsaturated isocyanate of 2-11 carbon atoms, (iii) an alkoxy or alkyl silane wherein the alkyl group is from 1-12 carbon atoms, and (iv) an oxazoline; and about 0 to about 49% by weight of a second moiety selected from at least one of an alkyl acrylate, alkyl methacrylate, vinyl ether, carbon monoxide, and sulfur dioxide, where the alkyl and ether groups are of 1-12 carbon atoms. The ethylene copolymer comprises about 1% to about 20% by weight of an ethylene copolymer which comprises at least about 50% by weight ethylene, about 1% to about 35% by weight of an acid-containing unsaturated mono-carboxylic acid, and about 0 to about 49% by weight of a moiety selected from at least one of alkyl acrylate, alkyl methacrylate, vinyl ether, carbon monoxide, and sulfur dioxide, and further wherein the acid groups are neutralized from 0-100% by a metal ion. The molar ratio of polymeric grafting agent to ethylene copolymer preferably ranges from about 1.0 to about 5.5.

The invention discloses a high electric conduction polyphenylene sulfide (PPS) composite material and the preparation method thereof. The percentage by weight of the compositions of the high electric conduction polyphenylene sulfide composite material is as follows: 40 to 70 percent of polyphenylene sulfide, 5 to 30 percent of conducting fiber, 5 to 30 percent of conducting powder, and other auxiliary agents from 0 to 5 percent. The conducting fiber and conducting powder in the conducing plastics provided by the invention disperse evenly with a plurality of lapping joints and high electric conductivity, thereby remarkably improving electric conductivity. The surface resistivity and volume resistivity of the material respectively reach 0.3-11.0 ohm and 0.07-8.5 ohm*cm, thereby meeting the requirements of plastic shaping techniques such as repeated injection molding, plastic extruding or die stamping. The processing art of the material is simple and can control the conducting fiber and conducting carbon black to evenly disperse in plastic particles, thereby enabling the PPS composite material to have high electric conductivity and meeting the requirements of industrial big production.

The invention relates to a low warpage liquid crystal polymer composition and a preparation method thereof; the composition comprises the following components by weight percentage: 20wt% to 80wt% of thermotropic liquid crystalline polymer with a melting point of at least 290 DEG C, 5wt% to 20 wt% of thermoplastic polyphenylene sulfide with a melting temperature of from 280 DEG C to 290 DEG C, 10 wt% to 70 wt% of reinforcing material and 0 wt% to 10 wt% of other additives. The preparation method comprises the steps: LCP and PPS resin are respectively dried at the temperature of 160 DEG C and 140 DEG C for 4-6 hours; a lubricating agent and a compatilizer to be added are uniformly mixed in a high speed blender and then are dried at the temperature of 80 DEG C for 4 to 6 hours; polyester resin to be added is dried for 4 to 6 hours at the temperature of 120 DEG C; the dried materials are uniformly mixed in the high speed blender and put into a main feeding hopper of a double-screw extruder; the reinforcing material is added from a side feeding opening of the double-screw extruder; and the materials are melted, squeezed out and pelleted. The preparation method has the advantages that the addition of polyphenylene sulfide can obviously reduce the warping degree; the fiber reinforcing material and lubricating material can be matched with polyphenylene sulfide so as to lead the mechanical property of the polyphenylene sulfide in the components to be reinforced.

The invention provides a method for generating a denitration catalyst on a filter material in situ. The method comprises the following steps: firstly, modifying the filter material by utilizing the oxidative self-polymerization reaction of dopamine, coating a layer of poly-dopamine film substances rich in such active groups as phenolic hydroxyl groups, nitrogenous functional groups on the surface of the filter material so as to activate the surface of a polyphenylene sulfide filter material fiber which is inert originally; and then generating a MnO2 catalyst on the surface of the poly-dopamine coated filter material by taking potassium permanganate as an oxidizing agent under the chelation of the poly-dopamine layer and a divalent manganese ion, thereby preparing the composite filter material with the denitration function. The method has the advantages of simplicity in operation, low requirement for instrument equipment, mild reaction conditions, no special requirement for types and shapes of base materials, no pollution to the environment and the like, and a novel concept and a method are provided for the modification and denitration functionalization for the filter material.

The invention discloses a high strengthening and toughening type polyphenylene sulfide composite material. 100 wt% of the composite material comprises 45-55 wt% of polyphenylene sulfide resin, 30-50 wt% of glass fibers, 4-8 wt% of a toughening agent, 0.4-1.0 wt% of a compatibilizer and 0.1-3 wt% of other additives; the surface of the glass fibers is impregnated with a silane coupling agent; the toughening agent is at least one selected from nylon 6, nylon 66, ethylene-methyl acrylate-glycidyl methacrylate and a maleic anhydride grafted styrene-ethylene-butadiene-styrene block copolymer elastomer; and the compatibilizer is selected from epoxy resins. The polyphenylene sulfide composite material disclosed in the invention has the advantage of high rigidity, high toughness and high flame retardation property, is especially suitable for producing small parts and ultrathin parts which have high requirements for the impact performance, and greatly broadens the application range of a phenyl sulfide material.

The invention discloses a polyphenylene sulfide composite material and a preparation method of the composite material, belonging to the technical field of macromolecular material. The polyphenylene sulfide composite material disclosed by the invention comprises following components in parts by weight: 20-35 parts of polyphenylene sulfide resin, 25-50 parts of heat-conducting filler, 10-35 parts of reinforcing fiber, 2-17 parts of elastomer, 0.2-1 parts of antioxidant, 0.3-0.8 parts of coupling agent, 1-2 parts of lubricant, 0.5-1 parts of dispersant and 0.2-0.5 parts of nucleating agent. The invention also discloses a preparation method of the polyphenylene sulfide composite material. The preparation method of the invention is simple; and the polyphenylene sulfide composite material has good heat conductivity and mechanical property.

The invention relates to a gear oil composition and applications thereof, mainly solving problems of abnormal gear wear and poor oxidation stability of an oil product which are caused by that the extreme pressure property of industrial gear oil in the prior art fails to satisfy a part of using requirements of the metallurgy industry. According to the technical scheme adopted by the gear oil composition, the gear oil composition comprises following components by weight: a) 100 parts of mineral base oil; b) 0.1-10.0 parts of an anti-wear reagent at extreme pressure; c) 0.01-2.0 parts of an antioxidant; d) 0.01-0.5 part of a metal deactivator and e) 0.01-1.5 parts of an oiliness agent, wherein the anti-wear reagent at extreme pressure is a mixture of sulfurized isobutylene and at least one selected from sulfurized olefin, phenyl sulfide, sulfurized aliphatic ester or amine thiophosphate diester; and the antioxidant is at least one selected from 2,6-di(tertbutyl)-p-cresol, 3.5-di(tertbutyl)-4-hydroxy phenyl acrylate, pentaerythrite tetra[beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate], N-phenyl-1-naphthylamine or alkylated diphenylamine. By the technical scheme, the problems are solved well and the gear oil composition can be used for industrial production.

The invention discloses modified polyphenylene sulfide resin suitable for 3D printing. The modified polyphenylene sulfide resin is a combination of the following components in parts by weight: 65-85 parts of polyphenylene sulfide resin, 0.05-0.6 part of a chain extender, 0.5-1 part of an end capping agent, 0.1-0.7 part of a crosslinking agent, 3-20 parts of low-molecular-weight polymer, 2-10 parts of a toughening agent, 1-5 parts of a reinforcing agent, 1-6 parts of a lubricating agent and 0.1-0.7 part of a heat stabilizer. The polyphenylene sulfide resin is modified by adopting the simple processes of mixing materials and extruding, and the processing temperature of the modified polyphenylene sulfide resin is reduced greatly. The melting temperature of the device formed by printing by adopting the modified polyphenylene sulfide resin is not reduced significantly, and the toughness is improved, and thus the polyphenylene sulfide resin can be widely applied to the field of 3D printing.

The filter fabric containing polyphenylene sulfide fibers, characterized in that the following (1) and/or (2) is satisfied is used to provide a filter fabric and a bag filter composed of the filter fabric excellent in dust-collecting efficiency and high in mechanical strength: (1) Containing at least two webs, one of which on the dust side contains 50 wt % or more of heat resistant fibers with a fiber, diameter of 15 μm or less, while the other web on the clean side contains 50 wt % or more of heat resistant fibers with a fiber diameter of 20 μm or more (2) Containing a web containing polyphenylene sulfide staple fibers with their fineness kept in a range from 1 to 3 dtex and fluorine-based staple fibers with their fineness kept in a range from 2 to 4 dtex.

An electrical cable is provided which includes an electrical conductor, a first insulating jacket disposed adjacent the electrical conductor and having a first relative permittivity, wherein the first insulating jacket is prepared from an admixture of: a polymer selected from the group consisting of polyaryletherether ketone polymer, polyphenylene sulfide polymer, polyether ketone, maleic anhydride modified polymers, Parmax® SRP polymers, and any mixtures thereof; and, a fluoropolymer additive. A second insulating jacket disposed adjacent the first insulating jacket and having a second relative permittivity that is less than the first relative permittivity, and wherein the insulating jacket is mechanically bonded to the second insulating jacket. In another aspect of the present invention, a method is provided for manufacturing a cable that includes providing an electrical conductor, extruding a first insulating jacket over the electrical conductor, and extruding a second insulating jacket thereon.

The present invention relates to a wear-resistant and mildewproof non-stick pan coating. The coating comprises a bottom layer and a surface layer; The bottom layer consists of the following materials in parts by weight: polyimide resin, modified polyvinylidene fluoride resin, a high-temperature-resistant pigment filler, modified polyorganosiloxane polymer, polyetheretherketone PEEK and graphite. The surface layer consists of the following materials in parts by weight: polytetrafluoroethylene resin, phenylene sulfide, acrylate rubber latex, epoxy accelerated resin, a catalyst, fumed silica, nano silver and the like. The wear-resistant and mildewproof non-stick pan coating prepared in the invention is chemically stable at the cooking temperature and does not generate hazardous substance PFOA. The coating has relatively great hardness and the damages of spatulas or spoons to the surface coating of the non-stick pan can be avoided. The non-stick pan prepared from the coating has low cost and a long service life.

The invention discloses auxiliary-addition-free polyphenylene sulfide resin industrial synthetic process. The formula of raw materials required in the auxiliary-addition-free polyphenylene sulfide resin industrial synthetic process is as follows: the mole ratio of sodium sulfide to sodium hydroxide to santochlor to N-methyl-2-pyrrolidinone is 0.93-1.15 to 1.00-1.28 to 1.98-2.98 to 1.18 to 1.48. The industrial synthetic process mainly comprises the following steps: firstly, in a sodium hydrosulfide dehydration treatment stage, a pipeline filter is adopted to filtrate a sodium hydrosulfide solution to treat mechanical impurities in the solution, then a sodium hydroxide solution with the concentration 84 mol percent is added in the formula for chemical treatment on the sodium hydrosulfide; secondly, in the condensation polymerization stage, anaerobic deionized water is added to further appropriately adjust the molecular weight and molecular weight distribution coefficient of synthesized polyphenylene sulfide resin; thirdly, deionized water is adopted for repeatedly scrubbing for 3 to 6 times, and finally, the target product of the auxiliary-addition-free polyphenylene sulfide resin industrial synthetic process provided by the invention is obtained. The resin in the obtained product of the auxiliary-addition-free polyphenylene sulfide resin industrial synthetic process is low in polydispersity index and high in oxygen index, and has an excellent electrical insulation property.

The invention discloses a method for recycling lithium salt and a solvent in preparation of polyphenylene sulfide. The method comprises the following operation processes: 1', washing a polyphenylene sulfide product by use of an N-methyl pyrrolidone solution of which the percentage by weight of water is not larger than 50% at the temperature of 150 to 250 DEG C in an inert gas environment, and combining the washing solution with a reaction medium solution; 2', transforming sodium sulfide into sodium chloride under the condition that the pH value of the combined solution is regulated to 6.5-7.0 in the inert gas environment; 3', adding water into the solution transformed in the step 2 so that the low-molecular polyphenylene sulfide is precipitated and then separated; and 4', respectively separating and recycling the sodium chloride, the N-methyl pyrrolidone and the lithium chloride from the separated solution under the inert gas environment. According to the method, the solvents need not to be evaporated out completely, so the energy consumption is reduced greatly; the method can be performed in various intermittent or continuous ways and convenient and easy to implement, degradation caused because the solvent is at high temperature for a long time is avoided, so the recycle rate of the solvent is high, and the recycling quality is good; a separated and recycled polyphenylene sulfide oligomer is utilizable, the purity of the recycled lithium chloride is not lower than 98%, and the quality of the recycled sodium chloride is excellent.

Disclosed is a flame retardant thermoplastic resin composition that includes about 100 parts by weight of a mixed resin (A) including about 10 to about 90 wt % of an aromatic polyamide resin (A-1) and about 10 to about 90 wt % of a polyphenylene sulfide resin (A-2), about 0.5 to about 30 parts by weight of a phosphinic acid metal salt flame retardant (B), and about 10 to about 100 parts by weight of a filler (C).

The invention relates to a method for preparing polyphenylene sulfide spun-bonded needle punched non-woven fabrics, comprising the steps: slicing of polyphenylene sulfide-pneumatic conveying-precrystallization-drying- melt spinning-air drawing-filament web-forming-needle-punching reinforcement-after finishing-winding, resulting in the polyphenylene sulfide spun-bonded needle punched non-woven fabrics. The invention further discloses a device for the implementation of the method for preparing polyphenylene sulfide spun-bonded needle punched non-woven fabrics. Compared with short fiber needle-punched method for the production of polyphenylene sulfide needle punched non-woven fabrics, the method for preparing polyphenylene sulfide needle punched non-woven fabrics by using spun-bonded filament needle punched method has the advantages of short technological procedures, small number of apparatuses, less required labor force, high production efficiency and large yield.

The invention discloses a method for preparing polyphenylene sulfide-based strong basic ion exchange fibers, which comprises the following steps of: first swelling raw polyphenylene sulfide fibers in a solvent, adding a raw material polyphenylene sulfide and a catalyst after the raw polyphenylene sulfide fibers are swelled, heating the mixture for chloromethylation and crosslinking reaction, and obtaining chloromethylated crosslinked polyphenylene sulfide fibers after the reaction is finished; then swelling the obtained chloromethylated crosslinked polyphenylene sulfide fibers in the solvent, adding trimethylamine solution after the chloromethylated crosslinked polyphenylene sulfide fibers are swelled, heating the reaction solution for quaternization reaction, and obtaining the polyphenylene sulfide-based strong basic ion exchange fiber products after the quaternization reaction is finished; and finally washing the products, and performing extraction, brine-washing and drying. The method for preparing the polyphenylene sulfide-based strong basic ion exchange fibers is simple and easy to industrially popularize and apply, and ensures relatively lower production cost. The products prepared by the method can be applied in the fields of treatment of industrial wastewater, air purification, preparation of ultrapure water, separation and extraction of medicinal chemicals, and the like.

The invention relates to the polyphenylene sulfide resin processing preparation field, and in particular relates to a glass fiber reinforced polyphenylene sulfide composite with high metal bonding strength and a preparation method thereof; the glass fiber reinforced polyphenylene sulfide composite comprises the following raw materials by weight: 51.7-81.2 parts of polyphenylene sulfide resin, 0-40 parts of continuous glass fiber; 5-13 parts of a toughening agent; 0.2-1 part of a weathering agent; 0.3-0.5 part of an antioxidant; 0.3-0.5 part of a lubricant and 2-4 parts of an additive A, the glass fiber reinforced polyphenylene sulfide composite not only has excellent weathering properties and excellent metal bonding strength, after metal bonding and anode oxidation treatment, the glass fiber reinforced polyphenylene sulfide composite may not discolor, the bonding strength decay is small, the glass fiber reinforced polyphenylene sulfide composite also has excellent weather resistance and low dielectric properties and loss factor, can satisfy the customer demand of different colors, and greatly improves the product appearance design freedom degree.

The invention relates to a silicon dioxide surface grafting modification method, and aims at insufficient atomic coordination number on silicon dioxide surface, high surface energy and easy agglomeration. An epoxy silane coupling agent and ammonia water react on the silicon dioxide surface in an alkaline environment to improve the dispersibility and compatibility with polymer; the silicon dioxide surface is subjected to grafting modification with a hindered amine antioxidant; the grafting modified silicon dioxide is nano powder particles with diameter no more than 30 nm; and the the purity of product is high up to 97.6%. the preparation process has advanced strict process and accurate data; the grafting modified silicon dioxide can be used as the additive for polyphenylene sulfide composite material, can well improve and the dispersibility and compatibility with polyphenylene sulfide matrix, and can improve processability and thermal oxidation resistance performance in fiber preparation and application.

The invention discloses a dedusting filter material containing a MnO2 catalyst, and a preparation method and application of the dedusting filter material. A polyphenylene sulfide punched felt is taken as the filter material; potassium permanganate is reduced into an amorphous MnO2 denitrification catalyst, which is inserted and disperses into a polypyrrole matrix, through in-situ reaction of acidic potassium permanganate and pyrrole monomer on the surface of the punched felt, so that the MnO2 has a high denitration rate; and besides, the polypyrrole formed in situ is taken as a medium for connecting the catalyst and the filter material, and therefore, the catalyst is unlikely to drop. The catalytic filter material has a function of removing PM2.5 and NOx simultaneously, and can overcome the disadvantages of complexity, high treatment costs and the like of a tail flue gas purification system in the prior art.

The invention discloses an antioxidant toughening modified polyphenylene sulfide (PPS) monofilament and a preparation method of the PPS monofilament. The method of the invention comprises the steps of adding an antioxidant, a toughener, and a dispersing coupler into the polyphenylene sulfide powder to prepare antioxidant toughening modified polyphenylene sulfide chip, and melting and spinning; wherein the antioxidant toughening modified polyphenylene sulfide chip consists of the following components by weight: 95-97% of polyphenylene sulfide powder, 0.2-0.6% of antioxidant, 1-4% of inorganic toughener and 1-2% of dispersing coupler. According to the formula of the antioxidant toughening modified polyphenylene sulfide chip and the preparation method of the antioxidant toughening modified polyphenylene sulfide monofilament of the invention, modified polyphenylene sulfide monofilaments with superior breaking strength, breaking elongation, dry-heat shrinkage, antioxidant performance and toughness can be produced, and the method is stable in production process, low in cost, and good in product quality.

A plastic pipe 10 is a pipe utilized in a cooling water systems, and the bonding strength of each layer is heightened, and resistance capabilities of the antifreeze solution are enhanced. The plastic pipe 10 comprises an inner layer 22 formed from either a polyphenylene sulfide or an aromatic polysulfide, which is a denatured substance thereof, an intermediate layer 24, which is a mixture of PPS resin and a polyamide resin, and an outer layer 26 including a polyamide resin. The inner layer 22 is formed such that permeation of an antifreeze, which has mainly ethylene glycol, is less than 3.0 g/m2 per day. The resistance capabilities of the antifreeze solution can be achieved by making the thickness of the inner layer 22 0.2 mm or greater.

The invention discloses a preparation method of a polyphenylene sulfide composite filter material filter bag. The method includes the steps of: 1. preparation of a polyphenylene sulfide composite filter material: selecting a polytetrafluoroethylene filter cloth of 100-200 grams per square meter as the base cloth, selecting 1.0-1.5 dtex superfine polyphenylene sulfide fiber to pave a surface layer, and selecting 1.0-1.5 dtex superfine polyphenylene sulfide fiber and 2.0-2.5 dtex ordinary polyphenylene sulfide fiber to pave a bottom layer mixedly; 2. preparation of the polyphenylene sulfide composite filter material filter bag: blanching a polytetrafluoroethylene composite adhesive tape evenly to a lapped seam line of the polyphenylene sulfide composite filter material filter bag by a blancher to completely cover needle eyes and lap side seam. The polytetrafluoroethylene composite adhesive tape includes a polytetrafluoroethylene substrate and a hot melt adhesive layer, and the hot melt adhesive layer is ethylene-vinyl acetate copolymer holt melt adhesive. The method provided by the invention can improve the filtering effect and service life of the PPS composite filter material filter bag to meet the requirements of practical use.

The invention relates to a heat-conducting polyphenylene sulfide and polyamide composite material, which comprises the following components in parts by weight: 30-50 parts of polyphenylene sulfide, 20-30 parts of polyamide, 20-40 parts of heat-conducting filler, 10-20 parts of glass fiber, 10-15 parts of epoxy resin, 0.5-1 part of antioxidant and 0.2-1 part of lubricant. By using a melt blending method, the preparation method comprises the following steps of: weighing each component according to the content of the formula and then placing in a high-speed mixer to uniformly mix; and extruding and granulating through a double-screw extruder. According to the heat-conducting polyphenylene sulfide and polyamide composite material, the heat conduction performance and the mechanical property of the polyphenylene sulfide can be synergistically improved, the heat conduction efficiency of the heat-conducting filler in the composite material is increased, the preparation process is simplified, and the material cost is reduced while good heat conduction performance and mechanical property of the material are kept.