Classified by physicochemical properties
According to a
variety of different physical and chemical properties of plastic, you can put
plastic into thermosetting plastics and thermoplastic plastics types.
⑴
thermosetting plastics
It refers
thermosetting plastics under heat or other conditions can be cured or with
insoluble (melt) plastic characteristics, such as phenolics, epoxy plastic.
Thermosetting plastic was divided formaldehyde cross-linking and other
cross-linking of two types. When heated to soften, harden when cooled, can
repeatedly soften and harden and maintain a certain shape. Soluble in certain
solvents, having a fusible soluble nature. Thermoplastics with excellent
electrical insulation properties, in particular polytetrafluoroethylene (PTFE),
polystyrene (PS), polyethylene (PE), polypropylene (PP) has a very low
dielectric constant and dielectric loss, should for use as a high-frequency and
high-voltage insulation material. Thermoplastic easy molding, but low in heat
resistance, easy to creep, with the degree of creep under load, the ambient
temperature, the solvent, the humidity varies. To overcome these weaknesses
thermoplastics, meet the need of space technology, new energy development and
other fields, countries are developing melt molding heat-resistant resin, such
as polyether ether ketone (PEEK), polyether sulfone (PES) , polyarylsulfone
(PASU), polyphenylene sulfide (PPS) and the like. To them as a matrix resin
composite material having high mechanical properties and chemical resistance,
thermoforming and welding between energy, interlaminar shear strength is better
than epoxy resin. As with PEEK as a matrix resin and carbon fiber composite
materials, the fatigue resistance than epoxy / carbon fiber. Its good impact
resistance, excellent creep resistance at room temperature, process, and can be
used continuously at 240 ~ 270 ℃, it is an ideal high temperature insulation material. It has high
strength and hardness at 200 ℃ with PES as a composite material matrix resin and carbon fibers, at
-100 ℃ can still maintain good impact resistance; non-toxic,
non-flammable, fuming at least, radiation resistance Well, the key components
for the spacecraft is expected to use it, but also molding into a radome and
the like.
Formaldehyde-crosslinked
plastics include phenolics, aminoplasts (such as urea - formaldehyde - melamine
- formaldehyde, etc.).
Other cross-linked
plastics include unsaturated polyesters, epoxy resins, diallyl phthalic acid
resins and the like.
Refers to
thermoplastic plastics can be repeatedly softened by heating and hardened by
cooling of the plastic, such as polyethylene, polytetrafluoroethylene or the
like within a specific temperature range. Thermoplastic plastic was divided
hydrocarbons, vinyl containing polar gene engineering, cellulose and other
types. After thermo-forming insoluble infusible form a cured resin molecules by
the linear structure of its cross-linked into a network structure. Thermal
decomposition will again strengthen damage. Typical phenolic thermosetting
plastic, epoxy, amino, unsaturated polyesters, furan, polysiloxane and other
materials, as well as newer polyethylene phthalate and propylene carbonate
plastic or the like. They have high heat resistance, heat easily deformed and
so on. The disadvantage is that the mechanical strength is generally not high,
but by adding fillers, made of laminate or molding material to improve its
mechanical strength.
Phenolic resin as the main raw
material of thermosetting plastics, such as phenolic molded plastic (commonly
known as Bakelite), with a durable, dimensionally stable, resistant to other
chemicals in addition to strong base effects and other characteristics.
According to different purposes and requirements, the addition of various
fillers and additives. Such as requiring high insulation performance of
varieties, can be mica or glass fiber as filler; to resistant varieties, may be
asbestos or other heat-resistant filler; species such as seismic requirements,
various appropriate fiber or rubber filler and a number of toughening agent to
produce high toughness materials. Further aniline may also be used, epoxy,
polyvinyl chloride, polyamide, polyvinyl acetal-modified phenolic resin, etc.
to meet the requirements of different applications. It can also be made with
phenolic resin phenolic laminate, which is characterized by high mechanical
strength, good electrical properties, corrosion resistance, easy processing,
widely used in low-voltage electrical equipment.
Aminoplast have urea
formaldehyde, melamine-formaldehyde, melamine urea formaldehyde. They have a
hard, scratch-resistant, colorless, translucent, etc., can be added to products
made of bright color pigment, commonly known as Bakelite. Because of its oil,
affected by the weak base and an organic solvent (but not acid), long-term use
at 70 ℃, short-term resistant to 110 ~ 120 ℃, can be used
electrician products. Melamine formaldehyde plastic plastic hardness than urea
formaldehyde, have better water resistance, heat resistance, arc resistance,
arc resistant insulating material can be used.
Epoxy resin as the main raw
material of thermosetting plastic varieties, many of them with a bisphenol A
type epoxy resin as a base of about 90%. It has excellent adhesion, electrical
insulation, heat resistance and chemical stability, shrinkage and water
absorption, good mechanical strength and other characteristics.
Unsaturated polyester and epoxy
resins can be made of glass steel, it has excellent mechanical strength. Such
as unsaturated polyester, glass, steel, good mechanical properties, low density
(only 1/5 to 1/4 of steel, aluminum, 1/2), easily processed into a variety of
electrical components. Electrical and mechanical properties of plastics to
phthalate acrylate resin are better than phenolic and amino thermoset plastic.
It is hygroscopic small, products dimensional stability, good moldability acid
and boiling water and some organic solvents. Molding plastic suitable for
manufacturing complex structure, both have high temperature insulation parts.
Usually long-term use in the temperature range of -60 ~ 180 ℃, the heat
levels up F grade to H level, higher than the phenolic and amino plastic heat
resistance.
Polysiloxane structure in the
form of silicone plastic used more often in Electronics & Electrical
Technology. Silicone laminated plastic over glass cloth as reinforcement
material; silicone molded plastic over glass fibers and asbestos packing, for
the manufacture of high temperature, high or submersible motors, electrical
appliances, electronic equipment parts. Such plastics are characterized by a
small dielectric constant and tgδ value, by the frequency of small, for
electricians and electronics industry corona resistance and arc discharge even
cause decomposition, the product is capable of conducting silica rather than
carbon black Such materials have outstanding heat resistance, can be used
continuously at 250 ℃. The main
disadvantage of polysiloxane is low mechanical strength, adhesiveness small,
oil poor. Has developed a number of modified silicone polymers, such as
plastics, polyester-modified silicone technology has been applied in the
electrician. Some plastic both thermoplastic and thermosetting plastics. Such
as polyvinyl chloride, usually thermoplastics, Japan has developed a new type
of liquid PVC is thermosetting molding temperature of 60 ~ 140 ℃; Lund
plastic American called Alex, both thermoplastic processing features, there are
the physical properties of thermoset plastics.
① hydrocarbon
plastics. Is a non-polar plastics, crystalline and non-crystalline points,
crystalline hydrocarbon plastics include polyethylene, polypropylene,
non-crystalline hydrocarbon plastics, including polystyrene and the like.
② vinyl
plastic containing polar gene. Fluorine plastic, most non-crystalline
transparent body, including polyvinyl chloride, polytetrafluoroethylene,
polyvinyl acetate and the like. Most vinyl-based monomer may be polymerized
using a free radical catalyst.
③ engineering
thermoplastics. Including polyoxymethylene, polyamide, polycarbonate, ABS,
polyphenylene oxide, polyethylene terephthalate, polysulfone, polyether
sulfone, polyimides, polyphenylene sulfide and the like.
Polytetrafluoroethylene. Modified polypropylene or the like are also included
in this range.
④
thermoplastic cellulose-based plastics. It includes cellulose acetate,
cellulose acetate butyrate, celluloid, cellophane and the like.
Third, according to the processing method
of classification
According to the
different kinds of plastic molding methods can be divided into membrane
pressure, lamination, injection, extrusion, blow molding, reaction injection
molding plastics and other types of plastic.
Membrane pressure,
mostly plastic processing performance and general properties similar to solid
plastic plastic; laminated plastic means of fabric impregnated with resin, the
laminated, hot materials incorporated as a whole; injection, extrusion and blow
mostly plastic properties and processability of thermoplastics with generally
similar plastic; means capable of molding plastic under no pressure or little
pressure, poured in a mold shaped article can harden into a liquid resin
mixture, such as MC nylon; Reaction Injection plastic material with a liquid,
the membrane cavity injection pressure, and allowed to react solidified into
shaped articles of plastic, such as polyurethane or the like.
more information www.injectionmoldchina.com
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