Performance and application of polyacrylamide
Polyacrylamide (PAM), also known as coagulant No.3, is a linear water-soluble polymer with a molecular weight of.
3 million-180,000, white powder or colorless viscous colloid, odorless, neutral, easily soluble in water, and easily decomposed when the temperature exceeds 120℃.
Polyacrylamide has a positive gene (-CONH2) in its molecule, which can adsorb and bridge suspended particles dispersed in solution and has strong flocculation effect, so it is widely used in water treatment and power, mining, coal preparation, asbestos products, petrochemical industry, paper making, textile, sugar making, medicine, environmental protection and other fields.
Name Molecular Weight (10,000) Ionization (%) Effective PH Solid Content% Residual Monomer% Appearance
Cationic polyacrylamide
CPAM 300-120010-501-14 ≥ 900.05 white dry powder.
Molecular weight (ten thousand), degree of hydrolysis (%), high efficiency PH, solid content, residual monomer and appearance.
Anionic polyacrylamide
Apam300-180010-507-14 ≥ 900 0.05-0.15 white granular powder.
Name Molecular Weight (10,000) Ionization (%) Effective PH Solid Content% Residual Monomer% Appearance
Nonionic polyacrylamide
NPAM 200-600 ≤ 31-8 ≥ 90 ≤ 0.05 white granular powder
Name molecular weight (ten thousand) cationic degree% anionic degree% PH solid content% Appearance
Zwitterionic polyacrylamide
NPAM1000-6000 5-50 8-251-14 ≥ 90 white powder
1. anion: structural formula [CH2 CH] n
CONH2
Nonionic type: structural formula: [—ch—CH2—ch—CH2 ——] n
CONH2 CONH2
Cation: structural formula: [—CH—CH2—CH—CH2]n
Bicarbonate
2. Physical characteristics; This product is colloid and powder. Colloidal products are colorless and transparent, non-toxic and non-corrosive. The powder is white granular or fine powdery solid, both of which are soluble in water. The water absorption varies with the ionic characteristics of derivatives. But almost insoluble in common solvents (benzene, toluene, ethanol, ether, acetone, esters, etc.). ), it can only dissolve about 1% in solvents such as ethylene glycol, glycerol, glacial acetic acid, formamide, lactic acid and acrylic acid. Different varieties and products with different molecular weights have different properties.
3. Uses: Mainly used in oil production, sugar production, coal washing, mineral processing, paper making, coating, hydrometallurgy, textile, stone cutting, chemical industry, pesticide, medicine and sewage treatment. Colloidal and powdery polyacrylamide can produce products with different content, molecular weight and degree of hydrolysis according to the product quality requirements provided by users.
PAM flocculant has a wide range of applications, and different applications require different properties. In order to meet the needs of various uses, countries all over the world have developed very complex varieties and specifications, and now they have formed a relatively complete product series.
4. Usage: This product is a high molecular linear polymer, especially when powder is used, the following points should be achieved when preparing PAM:
(1) Neutral water without salt and inclusions is suitable;
(2) Using warm water of about 40℃ but not more than 60℃ can accelerate the dissolution of flocculant;
(PAM is slowly sprinkled into water in the process of dissolution, and difficult sol clusters will appear after repeated sprinkling; Under the possible conditions, it will be more beneficial to the uniform distribution of flocculant by adding it step by step.
(4) When polyacrylamide is put into water, it should be stirred as soon as possible, so that the medicine and water can be mixed quickly and fully. Don't stir too hard and avoid strong mechanical stirring and pumping, otherwise the polymer will degrade, and the stirring speed should be100-300 r/min;
(5) the solubility is controlled at 0.5%-0.8% on a dry basis and diluted to 0.08% before use;
(6) Dilute solution is easy to degrade, no matter how much it is used, how much it is dissolved.
5. The product standard shall be implemented according to GB/T 13940-92.
(1) product standard of colloidal polyacrylamide:
Project index
Anionic nonionic cationic type
Appearance white jelly white jelly white jelly
Solid content ≥% 8-308-308-30
Molecular weight (ten thousand) 300-900 200-900 200-500
Free monomer ≤% 0.5 0.5 0.5
Degree of hydrolysis% 5-30 ≤ 55-30
(2) Product standard of polyacrylamide dry powder:
Project index
Anionic nonionic cationic type
Powder particles with white or yellow appearance
Solid content ≥% 90 90 90
Molecular weight (ten thousand) 300-1800 300-1000 500-1000.
Free monomer ≤% 0.5 0.5 0.5
Hydrolysis degree% 20-30 ≤ 5, and ionic degree 5-30.
The total solution time (hours) is 0.5—2 2—4 0.5— 1.
Acid in acid-base
Polymethyl methacrylate is a polymer polymerized from acrylic acid and its esters, and the corresponding plastics are collectively called polyacrylic plastics, among which polymethyl methacrylate is the most widely used. Polymethyl methacrylate (PMMA), commonly known as plexiglass, is the best synthetic transparent material with reasonable price so far. I. Performance Polymethyl methacrylate is a rigid, hard, colorless and transparent material with a density of1.1.19g/cm3, a small refractive index of about 1.49, a light transmittance of 92% and a haze of no more than 2. It is a high-quality organic transparent material. 1. Mechanical properties Polymethyl methacrylate (PMMA) has good comprehensive mechanical properties, and ranks among the top in general plastics. Its tensile, bending and compressive strength is higher than that of polyolefin, polystyrene and polyvinyl chloride, and its impact toughness is poor, but it is also slightly better than that of polystyrene. The mechanical properties such as tensile strength, bending strength and compressive strength of the cast bulk polymerized polymethylmethacrylate sheet (such as plexiglass for aviation) are high, which can reach the level of engineering plastics such as polyamide and polycarbonate. Generally speaking, the tensile strength of PMMA can reach 50-77MPa, and the bending strength can reach 90- 130MPa. The upper limit of these performance data has reached or even exceeded some engineering plastics. Its elongation at break is only 2%-3%, so its mechanical properties are basically hard, brittle and plastic, and it is notch sensitive and easy to crack under stress, but its fracture surface is not as sharp and uneven as polystyrene and ordinary inorganic glass. 40℃ is the second-order transition temperature, which is equivalent to the temperature at which the side methyl group begins to move. When the temperature exceeds 40℃, the toughness and ductility of the material are improved. Polymethyl methacrylate has low surface hardness and is easy to scratch. The strength of polymethyl methacrylate is related to the stress action time, and decreases with the increase of action time. After tensile orientation, the mechanical properties of PMMA (oriented PMMA) are obviously improved, and the notch sensitivity is also improved. The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104℃, the maximum continuous use temperature varies between 65℃ and 95℃ according to different working conditions. The thermal deformation temperature is about 96℃( 1. 18MPa), and the Vicat softening temperature is about 1 13℃. Heat resistance can be improved by polymerization of monomers with propylene methacrylate or ethylene glycol acrylate. The cold resistance of PMMA is also poor, and the brittle temperature is about 9.2℃. The thermal stability of polymethyl methacrylate is moderate, which is better than PVC and polyoxymethylene, but not as good as polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270℃, and the flow temperature is about 65438 060℃, which still has a wide melting processing temperature range. The thermal conductivity and specific heat capacity of polymethyl methacrylate are at a medium level in plastics, which are 0. 19W/CM respectively. K and 1464J/Kg. K2 respectively. The electrical properties of PMMA are not as good as those of nonpolar plastics such as polyolefin and polystyrene, because there are polar methyl ester groups on the main chain side. The polarity of methyl ester group is not too great, and polymethyl methacrylate still has good dielectric and electrical insulation properties. It is worth pointing out that polymethyl methacrylate and even the whole acrylic plastic have excellent arc resistance, and under the action of arc, there will be no carbonized conductive path and arc trajectory on the surface. 20℃ is the second-order transition temperature, which corresponds to the temperature at which the pendant methyl ester groups begin to move. Below 20℃, the side methyl ester group is frozen, and above 20℃, the electrical properties of the material will be improved. 3. Chemical-resistant and solvent-resistant PMMA can resist dilute inorganic acids, but concentrated inorganic acids can corrode it, and it can resist alkali, but warm sodium hydroxide and potassium hydroxide can corrode it, and it can resist salt and oil, aliphatic hydrocarbons, and is insoluble in water, methanol, glycerol, etc. However, it can absorb stress cracking caused by alcohol expansion and is intolerant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8(J/CM3) 1/2. It can be dissolved in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene and so on. , can also be dissolved with vinyl acetate and acetone. Polymethyl methacrylate has good resistance to gases such as ozone and sulfur dioxide. 4. Weather-resistant PMMA has excellent atmospheric aging resistance. After four years of natural aging test, the weight of the sample changed, the tensile strength and light transmittance decreased slightly, the color turned yellow slightly, the crack resistance decreased obviously, the impact strength increased slightly, and other physical properties remained almost unchanged. 5. Combustible PMMA is easy to burn, and its limiting oxygen index is only 17.3. Second, the processing of polymethyl methacrylate (I) process characteristics 1. Polymethyl methacrylate (PMMA) contains polar side methyl groups and has obvious hygroscopicity. Water absorption is generally 0.3%-0.4%. It must be dried before molding, and the drying condition is 80℃-85℃ for 4-5 hours. 2. Poly (methyl methacrylate) has effective and obvious non-Newtonian fluid characteristics in the temperature range of molding processing, and the melt viscosity will obviously decrease with the increase of shear rate, and the melt viscosity is also very sensitive to temperature changes. Therefore, for the molding of polymethyl methacrylate, increasing the molding pressure and temperature can obviously reduce the melt viscosity and obtain better fluidity. 3. The temperature at which PMMA begins to flow is about 160℃, and the temperature at which PMMA begins to decompose is higher than 270℃, which has a wide processing temperature range. 4. Poly (methyl methacrylate) has high melt viscosity and fast cooling speed, and the products are prone to internal stress, so the process conditions are strictly controlled during molding, and the products need post-treatment after molding. 5. Polymethyl methacrylate (PMMA) is an amorphous polymer, and its shrinkage rate and its variation range are small, generally around 0.5%-0.8%, which is beneficial to molding plastic parts with high dimensional accuracy. 6.PMMA has excellent machinability, and its profile can be easily processed into various required sizes. (II) Processing technology Polymethyl methacrylate can adopt casting, injection molding, extrusion, thermoforming and other processes. 1. Casting molding is used to shape profiles, such as plexiglass plates and rods, that is, profiles are formed by bulk polymerization. After pouring, the products need to be post-treated, and the post-treatment conditions are: 60℃ for 2 hours, 120℃ for 2 hours. Pellets prepared by suspension polymerization are injection molded on a common plunger or screw injection molding machine. Table 1 is a typical process condition of PMMA injection molding. Table 1 injection molding process parameters of polymethyl methacrylate screw injection molding machine 180-200 180-200 middle 190-230 front180-210- +00 2 10-240 mold temperature℃ 40-80 40-80 injection pressure MPa 80- 120 80- 130 holding pressure MPa 40-60 40-60 screw speed rp.m- 1 20-30. 3. The extrusion molding of polymethyl methacrylate can also be used to prepare plexiglass plates, rods, tubes and sheets. Made of granular materials produced by suspension polymerization. However, the profiles prepared in this way, especially plates, are not as good as those formed by casting because of their low molecular weight, and their mechanical properties, heat resistance and solvent resistance have the advantages of high production efficiency, especially for pipes and other molds formed by casting. A contour that is difficult to manufacture. Extrusion molding can adopt single-stage or two-stage exhaust extruder, and the length-diameter ratio of screw is generally 20-25. Table 2 shows the typical process conditions of extrusion molding. Table 2 Extrusion molding process conditions of polymethylmethacrylate Process parameters Compression ratio of sheet rod and screw 2 2 barrel temperature rear150-180150-180 middle 170-200 170-200 front/. A2.8- 12.4 0.7-3.4 inlet temperature℃ 50-80 50-80 mold temperature℃180-200170-1904. Thermoforming Thermoforming is to make plexiglass plates or sheets into products of various sizes and shapes and cut them into required shapes. Pressing can be done by vacuum stretching or directly pressing the punch with the die surface. The hot forming temperature can refer to the recommended temperature range in Table 3. When using rapid vacuum low draft molding products, the temperature close to the lower limit should be used, and the temperature close to the upper limit should be used for deep draft products with complex shapes, generally at room temperature. Table 3 Lower limit temperature Upper limit temperature Normal temperature cooling temperature149℃193℃177℃ 85℃ In addition, the profile can be turned, milled, drilled and cut. Application of PMMA As a transparent material with excellent performance, PMMA is widely used in the following aspects: 1. Lamps and lighting equipment, such as various household lamps, fluorescent lamp covers, automobile taillights, signal lights, road signs, etc. 2. Optical glass, such as making various lenses, mirrors, prisms, TV screens, Fresnel lenses, cameras, etc. 3. Prepare various instrument dials, housings and dials. 4. Preparation of optical fiber. 5. Commercial advertising windows and billboards. 6. Aircraft cockpit glass, bulletproof glass for aircraft and automobiles (with interlayer materials). 7. All kinds of medical, military and architectural glass.
I. Overview of the characteristics of polyetherimide (PEI)
Polyether imide resin is an amorphous thermoplastic resin, abbreviated as PEI.
1. Outstanding high temperature resistance, high strength and high modulus;
4. Wide chemical resistance;
3. It has flame retardancy, low smoke and toxicity when burning (UL94 V-0 grade when the thickness of some brands is 0.25 mm ~ 0.40 mm);
2. Dielectric constant and loss factor are highly stable in a very wide temperature and frequency range;
5. High transparency (dark amber → light amber).
Second, the PEI application summary:
characteristic
Self-flame retardant up to V-0( 1.6 mm), used in electrical/electronic applications and high-end connectors (optical fiber telecommunication equipment).
Aircraft, aircraft and aircraft (internal parts, wires and cables) with low smoke and low toxicity (PH=5.7) when burning.
Radiation-resistant (flexible modification) nuclear power plant (internal components and parts, wires and cables)
Long-term heat resistance (RTI) is as high as 356℉( 180℃), catering services (baking), food equipment and public cookers that do not absorb microwaves.
Dimensional stability high-temperature lighting condenser, reflector, lamp cup and fastener
High temperature strength, high modulus and high fluidity under automobile hood are suitable for thin-walled design.
Hydrolysis resistance, strong chemical stability, medical instruments, trays, water pump pressure parts (repeated washing, high temperature sterilization)
Wave welding and steam welding stability electrical/electronic applications, high-end connectors (optical fiber telecommunications equipment)
FDA and NSF medical equipment, appliances and HVAC applications