polystyrene(English:Polystyrene, short forPS）It is colorless and transparentThermoplastic, of which expanded polystyrene is commonly known asStyrofoam(also calledPolylon, commonly known in Hong KongStyrofoam）。With temperature higher than 100 ℃Glass transition temperatureTherefore, it is often used to make various disposable containers that need to withstand the temperature of boiling water, andDisposable foam lunch boxEtc.
Put styrene ininert gasThe temperature is controlled within the range of 60-90 ℃Dibenzoyl peroxideThe transparent block resin can be obtained by polymerization with catalyst.This kind of resin has high purity, good transparency and luster.
Emulsion method
Under the action of catalyst, the water emulsion temperature of styrene monomer is controlled at 80-95 ℃ for polymerization, and then the polymer is separated from the mother liquor and treated to obtain powdered resin.The heat resistance of the finished product is slightly higher than that of the bulk polymer resin, but the electrical insulation and transparency are slightly poor.
Combustion phenomenon
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It has good combustion performance and is flammable. It will continue to burn after leaving the fire with styrene odor.The flame is yellow and emits black smoke;Softening and foaming during combustion.
performance
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The structural formula of polystyrene belongs to linear structure, but there are large phenyl groups with continuous spacing on the carbon atoms of the molecular chain, which determines the special properties of polystyrene.
1. Rigid texture,Impact strengthLower;Random polystyrene has good luster, high light transmittance and good colourability.
2. The softening temperature is 80 ℃. Below 80 ℃, it is a solid as hard as glass, and above 80 ℃, it will become a softer object with similar rubber properties. Avoid using it at high temperatures.
3. Good molding performance, small shrinkage deformation of finished products and stable size within the use temperature range;Good water resistance,chemical stabilityIt decreases with the increase of temperature;It has good resistance to certain concentrations of inorganic acids, organic acids, salt solutions, alkalis, alcohols, vegetable oils, etc. It will gradually turn yellow, become impermeable and crack after long-term storage in sunlight.
4. Cracking, discoloration, viscosity and melting often occur in contact with oils and insect repellents, which are prone to aging and yellowing under the action of light, oxygen and heat.
5. Easily soluble in chloroformdichloromethane, toluene, butyl acetate and other organic solvents, do not contact with the above solvents during storage.
Modification
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Polystyrene has many disadvantages, such as high brittleness, low softening temperature and easy to crack, which seriously affects its use.In order to eliminate its shortcomings, modified polystyrene has emerged;The way is to copolymerize styrene monomer with other units, or mix polystyrene with other polymers and copolymers.The modified varieties are mainly as follows:
1. Tough polystyrene
In order to improve the brittleness and fragility of polystyrene, the toughened polystyrene was prepared by blending with elastomers such as rubber (styrene butadiene or nitrile butadiene), which improved the impact strength of polystyrene, but reduced the transparency and electrical properties of the product.
2. Chlorinated styrene
Two chlorine atoms are introduced into the styrene structure to makeDichlorostyreneMonomer, and then polymerize to dichlorobenzenesynthetic resin。The modified polystyrene is still transparent, and its heat resistance and impact strength have been greatly improved.
3. Styrene and acrylonitrile copolymer (AS)
Due to the introduction of acrylonitrile monomer, the chemical corrosion resistance, heat resistance and mechanical strength of the material can be improved without cracks. It is an ideal material.
Butadiene is a good elastomer, and various monomers play their own excellent properties in the copolymer.So,ABS plasticIt is an ideal engineering plastic with good comprehensive properties.
purpose
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Polystyrene plastic is widely used in optical instruments, chemical departments and daily necessities, and is used to make tea trays, sugar bowls, soap boxes, cigarette boxes, student rulers, combs, etc.Due to certain air permeability, when making film products, it can also make goodFood packaging materials。
Polystyrene is hard and brittle, colorless and transparent, and can be mixed with a variety of dyes to produce different colors.Expanded polystyrene(commonly known asStyrofoam，Foam plastic）It is also used as building materials, with sound absorption, sound insulation, heat insulation and other effects. Recently, it has been widely used in hollow floor (new construction method).
history
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In 1839, German Eduard Simon extracted polystyrene from natural resin for the first time.
In 1930, BASF began to commercially produce polystyrene in Germany.
In 1934, Dow began to produce polystyrene in the United States.
In 1954, Dow began to produce polystyrene foam.
Production and application
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Polystyrene is often used to make foam plastic products, and can be used with other rubber typesPolymer materialsCopolymerization produces products with different mechanical properties.Common applications in daily life include disposable plastic tableware, instant noodles, family barrels, and transparent CD boxes.In the field of building materials, foamed polystyrene (styrofoam) is widely used as a sound insulation and heat insulation material for hollow floor slabs.Most disposable beverage cups are made of this plastic, but if it is coffee or tea, these hot drinks will be made of paper cups orPolypropylene plasticAnd other heat resistant varieties.
Impact resistant polystyrene (HIPS)
Impact resistant polystyrene（High impact polystyrene）By adding polybutyl rubber The particle method produces an impact resistant polystyrene product.This polystyrene product will add micron gradeRubber particlesThe polystyrene andrubberThe particles are connected together.When impacted, the stress at the tip of crack growth will be released by relatively soft rubber particles.Therefore, the crack propagation is hindered and the impact resistance is improved.
Styrene acrylonitrile (SAN)
SAN isStyrene acrylonitrile resinAbbreviation of.Styrene acrylonitrile isstyrene acrylonitrile Is a colorless and transparent copolymer with high mechanical strengthpolypropyleneBased engineering plastics.The chemical stability of SAN is better than that of polystyrene.The transparency and UV resistance of SAN products are inferiorPolymethyl methacrylateClass products, but the price is relatively cheap.
Because of its low quality (especially foaming type) and low residual value, polystyrene is not easy to recycle.Generally, polystyrene cannotStreet CollectionMethod.However, the reuse of expanded polystyrene has also been greatly improved in industry, and many new methods for densification have emerged.This method, which can increase its density, usually increases the density by 15 slugs/ft3 (29.1 g/cm3) and forms the center of suitable regeneration operation on clean polystyrene.Some polystyrene manufacturing plants can recycle the waste foamed polystyrene after use.For example, in Michigan, Mason's Dart Container factory is recycling used polystyrene and industrial polystyrene.
Discarded polystyrene cannot pass throughbiodegradationandPhotolysisget intoBiogeochemical cycle。Due to the low content of expanded polystyrene (styrofoam)proportionAs a result, it floats on the water surface or moves with the wind, causing subjective landscape damage.according toCalifornia Coastal Commission (California Coastal Commission)Marine drift。For the plastic marine organisms that are eaten by mistakedigestive systemCause injury.
Styrene monomer is not easily soluble in water and will be decomposed into 90% after 16 weeks in soil.
Bread worm（Tenebrio molitorLarvae) A certain kind of bacteria found in the digestive tract can achieve the way of natural decomposition of the material.
Recovery and recycling
Resource recycling: in the plastic classification mark, the PS code is 6 (a triangle number mark is formed by a clockwise circular arrow). The bottom of the plastic body or the packaging must be listed so that consumers and recyclers can classify properly.
