The performance and application of ABS
Attention should be paid to the performance testing of plastic ABS
(1) General performance:
The appearance of ABS is opaque and ivory-colored pellets, non-toxic, tasteless, and low water absorption. Its products can be painted in various colors and have a high gloss of 90%. ABS has good combination with other materials and is easy to print on the surface. , Coating and plating treatment. The oxygen index of ABS is 18.2, it is a flammable polymer, the flame is yellow, there is black smoke, it is burnt but does not drip, and it emits a special cinnamon smell.
ABS is a resin with very good comprehensive properties. It has high impact strength and surface hardness in a relatively wide temperature range. Its thermal deformation temperature is higher than that of PA and PVC, and its dimensional stability is good.
The fluidity of ABS melt is better than PVC and PC, but worse than PE, PA and PS, similar to POM and HIPS. The flow characteristics of ABS belong tonon-newtonian fluid, its melt viscosity is related to processing temperature and shear rate, but it is more sensitive to shear rate.
(2) Mechanical properties
ABS has excellent mechanical properties, its impact strength is good, and it can be used at extremely low temperatures. Even if the ABS product is damaged, it can only be damaged by tensile damage instead of impact damage. ABS has excellent wear resistance, and its size It has good stability and oil resistance, and can be used for bearings under medium load and speed. The creep of ABS is larger than that of PSF and PC, but smaller than that of PA and POM.Bending strengthThe mechanical properties of ABS are greatly affected by temperature.
(3) Thermal properties
ABS is an amorphous polymer with no obvious melting point; the melt viscosity is high, the fluidity is poor, the weather resistance is poor, and ultraviolet rays can cause discoloration; the heat distortion temperature is 70-107 degrees Celsius (about 85), and the product can be recovered after annealing. Increase by about 10 degrees Celsius. Sensitive to temperature and shear rate; ABS can still show certain toughness at -40 degrees Celsius, and can be used for a long time in the temperature range of -40 degrees Celsius to 85 degrees Celsius.
(4) Electrical properties
ABS has good electrical insulation and is hardly affected by temperature, humidity and frequency, so it can be used in most environments.
(5) Environmental performance
ABS is not affected by water, inorganic salts, alkali alcohols, hydrocarbon solvents, and various acids, but it is soluble in ketones, aldehydes, and chlorinated hydrocarbons. It will cause stress cracking when it is eroded by glacial acetic acid, vegetable oil, etc.
concept
ABS plastic is acrylonitrile (A) - butene (B) - styrene (S)3-member copolymer.It combines the properties of three components, among which acrylonitrile has high hardness and strength, heat resistance and corrosion resistance; butadiene has impact resistance and toughness; styrene has high surface gloss and easy coloring And easy processability. The characteristics of the above three components make ABS plastic a kind of "hard, tough, rigid" with good comprehensive performance.thermoplastic.Adjust the ratio of ABS3 components, and its performance will also change to meet the requirements of various applications, such as high-resistant ABS, heat-resistant ABS, high-gloss ABS, etc. ABS plastic has good molding processability, and can be injected. It can be formed by extrusion, thermoforming and other methods, and can be processed by sawing, drilling, filing, grinding, etc.3 ChloromethaneIt can also be bonded with organic solvents such as coating and electroplating. ABS plastic is also an ideal wood substitute and building material. ABS plastic has high strength, light weight, high surface hardness, very smooth, easy to clean, and stable size. It has good creep resistance and is suitable for electroplating treatment materials. Its application field is still expanding. ABS plastics are widely used in industry. ABS injection products are often used to make shells, boxes, parts, toys, etc. Extruded products Most of them are plates, rods, pipes, etc., which can be used for hot pressing, composite processing and model making.
Molecular Structure
The structure of ABS resin has elastomer as the main chain.graft copolymerAnd a graft copolymer with hard ABS resin main chain; or a mixture of rubber elastomer and hard ABS resin. In this way, different structures show different properties. The elastomer shows the toughness of rubber, and the hard ABS resin It shows rigidity, and several varieties such as high impact type, medium impact type, general impact type and special impact type can be obtained. Specifically, as the content of rubber component B (generally 5% to 30%) increases, the elasticity and resistance of the resin The impact will increase; but the tensile strength, fluidity, weather resistance, etc. will decrease. The content of the resin component AS (generally 70%95%) increases, the surface gloss, mechanical strength, weather resistance, etc. can be improved. Heat resistance, corrosion resistance, electrical properties, processing properties, etc., while impact strength, etc. will decrease. The proportions of A and B in the resin component are 30 percent 35 percent\/80 percent 65 percent respectively.
main features
Plastic ABS resin is the largest and most widely usedpolymer, it will be PB,PAN,P.S.The various properties of ABS are organically unified, and have excellent mechanical properties of toughness, hardness, and rigid phase balance. ABS isAcrylonitrile,butadienewithStyreneThe ternary copolymer, A stands for acrylonitrile, B stands for butadiene, and S stands for styrene. After actual use, it is found that: ABS plastic pipes are not resistant to sulfuric acid corrosion, and will be crushed and broken when encountering sulfuric acid.
Because it has three kinds of composition, it has good performance; acrylonitrile gives ABS resinchemical stability, oil resistance, certain stiffness and hardness; butadiene improves toughness, impact and cold resistance; styrene makes it have good dielectric properties and presents good processability.
Most of ABS is non-toxic, impermeable to water, but slightly permeable to water vapor, low water absorption, water absorption at room temperature does not exceed 1% for one year, and the physical properties do not change. The surface of ABS resin products can be polished to obtain a high-gloss finish. Products. It is 3-5 times stronger than ordinary plastics.
ABS has excellent comprehensive physical andMechanical behavior, good low temperature impact resistance. Dimensional stability. Electrical properties, wear resistance, chemical resistance, dyeability, finished product processing and mechanical processing are better. ABS resin is resistant to water, inorganic salts, alkalis and acids, insoluble in Most alcohols and hydrocarbon solvents, but easily soluble in aldehydes, ketones, esters and some chlorinated hydrocarbons. ABS resinHeat distortion temperatureLow flammability, poor heat resistance. The melting temperature is 217237 degrees Celsius, and the thermal decomposition temperature is above 250 degrees Celsius. Modified on the market todayABS material, many of which are mixed withNozzle material,Recycled materials.The performance of the customer's molded product is not very stable.
(1) Material properties
1. Good overall performance, high impact strength, chemical stability, and good electrical properties;
2. with 372plexiglassGood weldability, made of two-color plastic parts, and the surface can be chrome-plated and painted;
3. There are high impact resistance, high heat resistance, flame retardant, reinforced, transparent and other grades;
5. Suitable for making generalMechanical Parts, anti-friction and wear-resistant parts, transmission parts and telecommunications parts.
(2) Formability
1.amorphous material, medium fluidity, high moisture absorption, must be fully dry, plastic parts that require a glossy surface must be preheated and dried at 80-90 degrees for a long time, 3 hours;
2. It is advisable to take high material temperature and high mold temperature, but it is easy to decompose if the material temperature is too high (the decomposition temperature is gt; 270 degrees Celsius). For plastic parts with high precision, the mold temperature should be 50-60 degrees Celsius. For high gloss, For heat-resistant plastic parts, the mold temperature should be 60-80 degrees Celsius;
3. If you need to solve the water-entrapment pattern, you need to improve the fluidity of the material, adopt high material temperature, high mold temperature, or change the water level;
4. If heat-resistant or flame-retardant materials are formed, plastic decomposition products will remain on the surface of the mold after 3-7 days of production, causing the surface of the mold to shine. The mold needs to be cleaned in time, and the exhaust position needs to be added on the surface of the mold;
5. The cooling speed is fast, the moldGating systemThe principle should be thick and short, cold slug holes should be set, and the gate should be large, such as: direct gate, disc gate or fan gate, etc., but the internal stress should be prevented from increasing, and an adjustable gate can be used if necessary. Gate. The mold should be heated, and wear-resistant steel should be used;
6. The material temperature has a great influence on the quality of plastic parts. If the material temperature is too low, it will cause material shortage, dull surface, and silver wire disorder. If the material temperature is too high, it will easily overflow, dark silver wire stripes will appear, and plastic parts will change color and blister;
7. Mold temperature has a great influence on the quality of plastic parts. When the mold temperature is low, the shrinkage rate, elongation rate, impact strength, bending resistance, compression resistance, and tensile strength are low. When the mold temperature exceeds 120 degrees Celsius, the cooling of the plastic parts is slow , Easy to deform and stick to the mold, difficult to demould, long molding cycle;
8. The molding shrinkage rate is small, melting cracking is easy to occur, and stress concentration occurs, so the molding conditions should be strictly controlled during molding, and the plastic parts should be annealed after molding;
9. The melting temperature is high, the viscosity is high, and it is not sensitive to shearing. For plastic parts larger than 200 grams, a screw injection machine should be used, and the nozzle should be heated. It is suitable to use an open and extended nozzle, and the injection speed is medium to high speed.
(3) Bonding problem
According to different needs, you can choose the following adhesives:
1. G-977: One-component room temperature curing soft elastic shockproofAdhesive, high and low temperature resistance, different viscosities, bonding speeds of a few seconds to several hours to complete curing;
2. KD-833: Instant adhesive, which can quickly bond PC plastic in a few seconds or tens of seconds, but the adhesive layer is hard and brittle, and it is not resistant to immersion in hot water above 60 degrees;
3. QN-505, two-component adhesive, the adhesive layer is soft, suitable for large-area bonding or compounding of PC plastics. But the high temperature resistance is poor;
4. QN-906: two-component adhesive, high temperature resistance;
5. G-988: One-component room temperaturevulcanized rubberAfter curing, the elastomer has excellent waterproof, shockproof adhesive, high and low temperature resistance, if the thickness is 1-2mm, it will be cured in about 10 minutes, basically cured in 5-6 hours, and has a certain strength. It needs at least 24 hours for complete curing. Hours. One-component, no need to mix, just apply after extrusion and let it stand, no need to heat
Preparation
There are many production methods for ABS, which can be divided into four categories: blending method, grafting method, combined method and grafting-blending method, and about eleven preparation processes. Most of them are emulsion methods, and the most promising one is Emulsion grafting method. By changing the ratio of the three monomers and adopting different polymerization methods, ABS can produce products of various specifications. Its structure includes graft copolymers with elasticity as the main chain and graft copolymers with resin as the main chain. For copolymers, the proportions of the three monomers generally range from 25% to 35% of acrylonitrile, 25% to 30% of butene and 40% to 50% of styrene.
Since PC\/ABS is a blend of two kinds of polymers, and PC is the main one, when processing products, sometimes there will be streaks at the gate, usually due to the expansion of the molten material into the mold cavity during high-speed injection. It is caused by melt fracture. Starting from the molding process, measures such as increasing the temperature of the material, increasing the temperature of the nozzle, and slowing down the injection speed can be taken to reduce the appearance of streaks on PC\/ABS products. Gate size, modify the gate shape, etc. to solve. For example, for large thin-walled parts, fan gates can also be used, and an ear groove can be added at the gate exit to make the jet near the gate, the material Flow impact marks and residual stress are concentrated in the ear groove without affecting the quality of PC\/ABS parts. At the same time, due to multiple gate injection molding or many runners, weld lines will also appear.
general performance
Plastic ABS non-toxic, tasteless, ivory translucent appearance, or transparent particles or powder. The density is 1.051.18g\/cm3, the shrinkage rate is 0.4% 0.9%, the elastic modulus is 2Gpa, the Poisson's ratio is 0.394, the hygroscopicity is less than 1%, the melting temperature is 217237 degrees Celsius, and the thermal decomposition temperature is gt; 250 degrees Celsius.
mechanical properties
Plastic ABS has excellent mechanical properties, good impact strength, and can be used at extremely low temperatures; plastic ABS has excellent wear resistance, good dimensional stability, and oil resistance, and can be used for motors under medium loads and low speeds. Bearings. The creep resistance of ABS is greater than that of PSF and PC, but smaller than that of PA and POM.
thermal properties
The heat distortion temperature of plastic ABS is 93118 degrees Celsius, and the product can be increased by about 10 degrees Celsius after annealing. ABS can still show a certain toughness at -40 degrees Celsius, and can be used in the temperature range of -40100 degrees Celsius.
electrical properties
Plastic ABS has good electrical insulation, and is hardly affected by temperature, humidity and frequency, and can be used in most environments.
Environmental performance
Plastic ABS is not affected by water, inorganic salts, alkalis and various acids, but it is soluble in ketones, aldehydes and chlorinated hydrocarbons. It will cause stress cracking when it is eroded by glacial acetic acid and vegetable oil. ABS has poor weather resistance. It is easy to degrade under the action of ultraviolet light; after half a year outdoors, the impact strength will drop by half.
Manufacturing processes
Injection molding process
ABS resin is inpolystyrene resinA ternary copolymer developed on the basis of modification. Among them, A represents acrylonitrile, B represents butadiene, and S represents styrene. ABS resin has comprehensive properties of three components, and A can improve oil resistance and chemical corrosion resistance. Therefore, it has a certain surface hardness; B makes ABS rubber-like toughness, which improves the impact toughness; S makes ABS plastic show better fluidity, so that it has good performance in thermoplastic molding.
ABS plastics are mainly used in the manufacture of housings for instruments, household appliances, telephones, televisions, etc. and ABS plastics for electroplating in my country, making themMetallic luster, ABS is used to replace metal. Among the liners of various models of refrigerators and various plastic products produced by our factory, ABS injection molding products account for more than 88 percent of the total number of refrigerator plastic products.
Raw material preparation
ABS resin for injection molding except for special grades or asColoringMost of them are light ivory or porcelain white opaque particles. The water absorption of the resin is not very high, such as when the processing allowable value is below 0.1~0.2%, for the case of tight packaging, proper storage and not too high requirements for the product It can be molded without drying treatment. But if the moisture content in the granules exceeds the specified value, it must be dried before forming. For special grade granules or products with higher requirements (such as electroplating products) , must also be dried before molding.
Molding process specification
1. Injection temperature: including barrel temperature (which can be divided into rear, middle and front 3 sections), nozzle temperature and mold temperature. Although the viscosity of ABS melt is less affected by temperature than injection pressure, but under high temperature conditions The mold of thin-walled products is beneficial. The decomposition temperature of ABS is theoretically as high as 270t. The rubber phase contained is not suitable for too high temperature, otherwise it will affect the performance of the product. The molding temperature of ABS requires a slightly higher temperature (at 210-250 degrees Celsius) for resins such as heat-resistant grades and electroplating grades to improve the temperature. It is difficult to fill the melt or it is beneficial to the electroplating performance. For general-purpose, flame-retardant, and impact-resistant ABS resins, the temperature should be lower to prevent decomposition or adverse physical and mechanical properties. Plug injection The temperature selected by the plunger injection molding machine is slightly higher than that of the screw injection molding machine. For general products, the temperature range of the plunger type is between 180 and 230 degrees Celsius, while the temperature range of the screw injection molding machine is 160 to 220X: it can be formed. After molding During the process, the general barrel temperature (rear 150~1701 degrees Celsius, middle 170~180 degrees Celsius, front 180~210 degrees Celsius). The nozzle temperature is generally 170~180 degrees Celsius, and special attention should be paid to any adjustment of the homogenization section and nozzle temperature. Changes will be reflected on the product, causing defects such as flashing, silver thread, discoloration, poor gloss, and obvious weld marks.
2. Mold temperature: Mold temperature has an important effect on the surface roughness of ABS products and reducing the internal stress of products. High mold temperature, easy melt filling, good appearance of products, small internal stress, and at the same time, electroplatability of products There are also improvements or enhancements, but there are also problems such as large molding shrinkage, long molding cycle, and easy deformation after demoulding. For products with general requirements, the mold temperature can be controlled at 40 to 50 degrees Celsius; for appearance and performance requirements. For relatively high products, the mold temperature can be controlled at 60~70 degrees Celsius. And the mold temperature should be uniform, and the temperature difference between the mold cavity and the mold core should not exceed 10. For deep hole products or products with more complex shapes, it is required that the mold cavity The temperature is slightly higher than the temperature of the mold core to facilitate the smooth demoulding of the product.
3. Injection pressure: Compared with polyethylene, polystyrene, nylon and other plastics, ABS has slightly poorer fluidity, so the required injection pressure is higher. However, excessive injection pressure may easily cause difficulty in demoulding or damage to the product. , may also bring greater internal stress to the product. The injection pressure of ABS is not only related to the wall thickness of the product, equipment type, etc., but also related to the grade of the resin. For products with thin walls, long processes, and small gates, the requirements The injection pressure should be high, as high as 130~150MPa, while thick-walled and large gate products only need 100MPa. In the actual production process, the injection pressure often selected by the screw injection machine is below 100MPa, (we use 50~ 70MPa), while the plunger type injection machine is generally above 100MPa. The holding pressure should not be too high. The screw type injection machine generally adopts 30~50MPa, while the plunger type needs to be above 60~70MPa. If the holding pressure is too high High, it will increase the internal stress of the product.
4. Injection speed. The injection speed has a certain effect on the change of the fluidity of the ABS culture body. If the injection speed is slow, there will be ripples on the surface of the product, poor welding, etc.; if the injection speed is fast, the mold can be filled quickly, but it is easy to Poor venting, poor apparent roughness, etc., will also reduce the tensile strength and elongation of the product, and the adhesion force of the coating will also be reduced due to too fast injection speed. Therefore, in the production process, in addition to If it is difficult to fill the mold, a higher injection speed must be used, and it is generally suitable to use a medium or low continuous rate.5