Introduzione ai materiali abs

ABS plastic is a terpolymer of acrylonitrile (A)-butadiene (B)-styrene (S). It combines the properties of three components, acrylonitrile with high hardness and strength, heat and corrosion resistance; butadiene with impact resistance and toughness; and styrene with a high gloss surface, easy colouring and easy processing. The properties of these three components make ABS plastic a “tough, tough and rigid” thermoplastic with good all-round properties. ABS plastics can be molded and processed by injection, extrusion, thermoforming, sawing, drilling, filing, grinding and other mechanical processes, and can be bonded with organic solvents such as trichloromethane, and can be coated and plated. ABS plastics are also ideal as wood substitutes and building materials, etc. ABS plastics are strong, light, hard, smooth, easy to clean and handle, dimensionally stable, creep resistant and suitable for electroplating. ABS plastics are used in a wide range of industrial applications and are often used for injection moulded products such as shells, cases, parts and toys. Extruded products are mostly sheets, rods, tubes, etc. and can be hot pressed, laminated and modelled. [2] Molecular structure
ABS resins are structured as a graft copolymer with an elastomer as the main chain and a graft copolymer with a hard ABS resin substance as the main chain; or as a mixture of rubber elastomer and hard ABS resin. In this way, the different structures show different properties, with the elastomer showing rubber toughness and the hard ABS resin showing rigidity, resulting in several varieties such as high impact, medium impact, general impact and special impact types. Specifically, as the content of rubber component B (typically 5% to 30%) increases, the elasticity and impact resistance of the resin increases; however, tensile strength, fluidity, and weathering resistance decrease. The content of the resin component AS (generally 70% to 95%) is increased to improve the surface gloss, mechanical strength, weather resistance, heat resistance, corrosion resistance, electrical properties, processing properties, etc.. While the impact strength, etc. is to decline. The proportion of A and B in the resin component is 30%~35%/80%~65% respectively.
Main characteristics
ABS is a terpolymer of acrylonitrile, butadiene and styrene, with A representing acrylonitrile, B representing butadiene and S representing styrene. After practical use it has been found that ABS plastic pipes, which are not resistant to sulphuric acid corrosion, crush and break in the presence of sulphuric acid.
Thanks to its three compositions, which give it good properties; acrylonitrile gives ABS resin chemical stability, oil resistance, some stiffness and hardness; butadiene makes it tough, impact and cold resistant; styrene gives it good dielectric properties and presents good processability.
Most ABS resins are non-toxic, impervious to water, but slightly permeable to water vapour, and have a low water absorption rate of no more than 1% at room temperature for one year, without any change in physical properties. The strength of ABS resin is 3-5 times higher than that of ordinary plastics.
ABS has excellent overall physical and mechanical properties and good low temperature impact resistance. Dimensional stability. ABS resin is resistant to water, inorganic salts, alkalis and acids, insoluble in most alcohols and hydrocarbon solvents, and readily soluble in aldehydes, ketones, esters and certain chlorinated hydrocarbons. ABS resin has a low heat deflection temperature is combustible and has poor heat resistance. The melting temperature is 217-237°C and the thermal decomposition temperature is above 250°C. Many of the modified ABS materials on the market today are adulterated with washout and recycled materials. The result is that the performance of the customer’s moulded product is not very stable.
(1) Material performance
1. good overall performance, high impact strength, chemical stability, good electrical properties.
2. good fusion with 372 plexiglass, made of two-colour plastic parts, and can be surface chrome plated, spray paint treatment.
3. available in high impact resistance, high heat resistance, flame retardant, reinforced and transparent grades.
4. a little less fluid than HIPS, better than PMMA, PC, etc., good flexibility.
5. suitable for making general mechanical parts, wear-resistant parts, transmission parts and telecommunication parts.
(2) Molding performance
1. amorphous material, medium fluidity, moisture absorption, must be fully dried, the surface requirements of the glossy plastic parts must be long preheated drying 80-90 degrees, 3 hours.
2. high material temperature, high mould temperature, but the material temperature is too high, easy to decompose (decomposition temperature is > 270 ℃). For high precision parts, the mould temperature should be 50-60°C. For high gloss, heat resistant parts, the mould temperature should be 60-80°C.
3. to solve the problem of water trapping, it is necessary to improve the fluidity of the material, take high material temperature, high mould temperature, or change the water entry level and other methods.
4. if forming heat-resistant or flame-retardant grade materials, the surface of the mould will be left with plastic decomposition after 3-7 days of production, resulting in a shiny mould surface, which needs to be cleaned up in time, and the mould surface needs to be increased with exhaust positions.
5. fast cooling speed, mould pouring system should be thick, short as a principle, should be set up cold material cavity, gate should be taken large, such as: direct gate, disc gate or fan gate, etc., but should prevent the increase of internal stress, if necessary, can be used to adjust the gate. The mould should be heated and made of wear-resistant steel.
6. the temperature of the material has a great influence on the quality of the moulded part, too low a temperature will cause a lack of material, a lack of lustre on the surface, a disorderly silver wire, too high a temperature will easily overflow the edge, a dark silver wire, a discolouration and blistering of the moulded part.
7. mould temperature has a great impact on the quality of plastic parts, mould temperature is low when the shrinkage, elongation, impact strength, bending resistance, compression resistance, low tensile strength. When the mould temperature exceeds 120℃, the moulded part will be slow to cool, easy to deform and stick to the mould, difficult to demould, and the moulding cycle will be long.
8. small shrinkage rate, easy to melt cracking, stress concentration, so molding should be strictly controlled molding conditions, after molding plastic parts should be annealed treatment.
9. high melting temperature, high viscosity, insensitive to shear action, for plastic parts larger than 200 grams, screw injection machine should be used, the nozzle should be heated, it is desirable to use open and smooth extension type nozzle, injection speed in high speed.
(3) Bonding problems
Depending on the needs, the following adhesives can be selected.
1. G-977: one-component room temperature curing soft elastic anti-shock adhesive, resistant to high and low temperatures, different viscosity bonding speed of a few seconds to a few hours curing finished.
2. KD-833: instant adhesive, can quickly bond PC plastics in seconds or tens of seconds, but the adhesive layer is hard and brittle and not resistant to hot water immersion above 60 degrees.
ABS plastic pipe
ABS plastic tubes
3. QN-505, two-component adhesive, with soft adhesive layer, suitable for bonding or laminating PC plastics in large areas. However, it has poor resistance to high temperatures.
4. QN-906: two-component adhesive, high-temperature resistant.
5. G-988: one-component room temperature vulcanisation adhesive, after curing is an elastomer with excellent waterproof, shockproof adhesive, high and low temperature resistance, 1-2mm thickness, about 10 minutes initial solidification, 5-6 hours basic curing, there is a certain strength. It takes at least 24 hours to fully cure. Single component, no mixing required, just apply after extrusion and leave to set, no need to add heat.
Preparation methods
There are many methods of producing ABS, which can be divided into four main categories: doping, grafting, jointing and graft-doping, with about eleven preparation processes. ABS can be produced by changing the ratio of the three monomers and using different polymerisation methods to produce a variety of specifications. Styrene 40% to 50%.
As PC/ABS is a blend of two polymers, with PC being the main one, when processing the product, sometimes there is also the phenomenon of mottling at the gate, usually due to the expansion of the melt into the mould cavity during high speed injection. This is usually caused by the expansion of the melt into the cavity during high speed injection. The melt ruptures. In terms of the moulding process, measures such as increasing the material temperature, increasing the nozzle temperature and slowing down the injection speed can be taken to reduce the occurrence of mottling in PC/ABS products, as well as increasing the mould temperature, increasing the indiscriminate groove, increasing the gate size and modifying the shape of the gate. For example, a fan-shaped sprue can be used for large thin-walled parts, or an ear-shaped sprue can be used, with an additional ear slot at the exit of the sprue, so that the spraying near the sprue, material flow impact marks, and residual stresses are concentrated in the ear slot without affecting the quality of the PC/ABS part. At the same time, fusion lines can occur due to multiple gate injection or when there are many manifolds.


General Properties
Plastic ABS is non-toxic, odourless, with an ivory-coloured translucent appearance, or transparent granules or powder. Density 1.05~1.18g/cm3, shrinkage 0.4%~0.9%, modulus of elasticity 2Gpa, Poisson’s ratio 0.394, hygroscopicity <1%, melt temperature 217~237°C, thermal decomposition temperature >250°C.
Mechanical properties
Plastic ABS has excellent mechanical properties, its impact strength is good and can be used at very low temperatures; plastic ABS has excellent wear resistance, good dimensional stability, and oil resistance, and can be used for bearings under medium loads and low rotational speeds; ABS has greater creep resistance than PSF and PC, but smaller than PA and POM.
Thermal properties
The thermal deformation temperature of ABS is 93~118°C. The product can be increased by about 10°C after annealing treatment.
Electrical properties
Plastic ABS has good electrical insulation and is virtually unaffected by temperature, humidity and frequency, and can be used in most environments.
Environmental properties
Plastic ABS is unaffected by water, inorganic salts, alkalis and a variety of acids, but is soluble in ketones, aldehydes and chlorinated hydrocarbons, and is subject to stress cracking from erosion by ice acetic acid and vegetable oils. plastic ABS has poor weatherability and is susceptible to degradation under ultraviolet light; after six months outdoors, impact strength drops by half.
Main uses edit Podcast
Engineering plastics
PC/ABS recycled material is an important engineering plastic alloy used in a wide range of applications including automotive, electrical and electronic, office and communications equipment. Nowadays, in order to meet the special requirements of fire safety in application areas (especially electronic and electrical products), the flame retardant technology of PC/ABS alloys has become a hot topic of research. However, as technology advances and the requirements for environmental friendliness of materials increase, the hazards associated with traditional halogen-based flame retardancy are becoming increasingly apparent.
In engineering, ABS is widely used in engineering piping, and ABS piping can generally be used in pool bottom piping in municipalities for projects with high material requirements.
3d printing
ABS plastic is one of the main materials used in 3D printing, the reason why it can become a consumable for 3D printing is its characteristics.
The largest areas of application for ABS resins are automotive, electronics and building materials. In the automotive sector, it is used in instrument panels, exterior body panels, interior trim panels, steering wheels, sound insulation panels, door locks, bumpers, ventilation ducts and many other components. In electrical appliances, they are used in refrigerators, televisions, washing machines, air conditioners, computers, photocopiers and other electronic appliances. For building materials, ABS pipes, ABS sanitary ware and ABS decorative panels are widely used in the building materials industry. ABS is also widely used in packaging, furniture, sports and recreational goods, machinery and instrumentation industries.
ABS resin is widely used in the automotive industry. In the electrical and instrumentation industry and the machinery industry, it is often used as gears, car parts, fenders, handrails, refrigerator linings, blades, bearings, handles, pipes, joints, instrument housings, instrument panels, basin helmets, etc. In household appliances and household electronic equipment, the application prospects are even broader, such as televisions, recorders, refrigerators, freezers, washing machines, air conditioners, hoovers and various small household appliances; daily necessities include shoes, bags, various travel boxes, office equipment, toys and various containers, etc. Low foaming ABS can replace wood and is suitable for building materials, furniture and household items.
ABS has a comprehensive range of good properties and good processability, so it has a footprint in a wide range of applications, as outlined below.
1. Automotive industry
The automotive industry has a large number of parts made from ABS or ABS alloys, such as the Santana car in Shanghai, which uses 11kg of ABS per car, ranking third in terms of plastics used in automobiles. ABS is also used in a staggering amount of other vehicles, and in 2000 China used 35,000 tonnes of ABS for automobiles. The main parts of cars use ABS, such as instrument panels with PC/ABS as the backbone, and then PVC/ABS/BOVC films on the surface. In addition, a large number of interior decorative parts use ABS, such as the glove box, glove box assembly is made of heat-resistant ABS, door sill upper and lower trim parts, water tank cover made of ABS, in addition to many parts using ABS as raw material.
2. Office machines
Because ABS has a high gloss and is easy to shape, office equipment machines need to have a beautiful appearance and a good feel, such as telephone casings, memory casings, as well as computers, fax machines and photocopiers in which a large number of parts made of ABS are used.
3. Household appliances
Because of its high gloss and ease of moulding, ABS has a wide market in home appliances and small household appliances, such as home fax machines, stereos and VCDs.
ABS is a tough and rigid thermoplastic made from a blend or terpolymer of acrylonitrile, butadiene and styrene. Styrene gives ABS good mouldability, gloss and rigidity; acrylonitrile gives ABS good heat resistance, chemical resistance and surface hardness; and butadiene gives ABS good impact strength and low temperature resilience. The properties of the three components vary in different proportions.