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Файл:Chemistry, technology and properties of synthetic rubber. Tutorial
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Continuation of Table 11
Rubber
Mooney viscosity at 100°С
50-70 70-100 60-100
Tensile stress, MPa 15-17 15-17 17-21
Elongation at break, % 400 250 250-320
Tear resistance, кН/м 50-70 60-80 60-80
Shore A hardness 80-90 70-80 70-80
Elasticity, % 11-15 28-33 30-35
Brittle temperature, °С — -(40-44) -(40-44)
Saturation coefficient at
— 03 0,3
35°С
Residual set at 20% during
20-25 20-30
24 h at 100°С
Swelling in the isooctane:
1-4 8-10 15-20
toluene mixture (50:50), %
* Herchlor-Н, hydrin-100, gechron-100, epichroma -Н. ** Herchlor С, hydrin -200, gechron -2000, epichroma -С. *** Herchlor -Т,
hydrin -400, epichroma -Cg.
Production
Epichlorohydrin rubber are synthesized in solution (diluents
are aromatic or aliphatic. hydrocarbons, ethers and their mixtures
with hydrocarbons) or in bulk in the presence of catalyst systems
based on trialkyl aluminium at 30-70°C and pressure of 0.2-0.3 MPa
for 8-12 hours. Epichlorohydrin rubbers are stabilized with nonstaining (substituted phenols) and coloring (secondary aromatic
amines derivatives) antioxidants. Rubber compounds based on
epichlorohydrin rubber are prepared in mixing mills (15-17 minutes
at 40-50°C) or in the mixer (7-10 min at a temperature not above
100°C). For epichlorohydrin rubber vulcanization there are used
polyamines and thio compounds which in the presence of metal
oxides react with the mobile chlorine atoms. For temperature
stabilization of rubbers nickel dibutyldithiocarbamate is used.
Rubber based on epichlorohydrin rubbers are oil, petroleum,
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gasoline, gas and ozone resistant at both low and high temperatures.
For heat resistance they are superior than chloroprene rubber,
butadiene-nitrile and acrylic rubber. Epichlorohydrin copolymers
rubbers have also satisfactory frost resistance that rises when
introducing an ester plasticizer, for example, dibutyl phthalate.
Application
Epichlorohydrin rubber is used to produce oil-resistant parts
(hoses, gaskets, sleeves, cuffs, rings, face seals) used in the
petroleum, automotive and aircraft industry. Homopolymer is also
used as a fire retardant and for cables covering. Due to the resistance
to vapor diffusion of oils, fuels and refrigerants the epichlorohydrin
rubber is used for making refrigerator parts, gas and vacuum
diaphragms.
Trade marks
Epichlorohydrin rubber production is small tonnage.
Basically it is produced in USA (hydrin, herchlor) and Japan
(Gechron, epichroma).
3.9 Polychloroprene
C
Cl
C
CH
n
HC
Polychloroprene (CR) is a family of synthetic rubbers that are
produced by polymerization of chloroprene.
History
Polychloroprene (Neoprene) was invented by DuPont
scientists in 1930.
DuPont first marketed the compound in 1931 under the trade
name DuPrene, but its commercial possibilities were limited by the
original manufacturing process, which left the product with a foul
odor. A new process was developed, which eliminated the odorcausing byproducts and halved production costs, and the company
began selling the material to manufacturers of finished end-products.
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Since the company itself did not manufacture any DuPrenecontaining end products, the trademark was dropped in 1937 and
replaced with a generic name, neoprene, in an attempt "to signify that
the material is an ingredient, not a finished consumer product". By
1939, sales of neoprene were generating profits over $300000 for the
company.
Properties
Neoprene resists degradation more than natural or synthetic
rubber. It resists burning better than exclusively hydrocarbon based
rubbers. Neoprene's burn point is around 260°C. Neoprene exhibits
good chemical stability, and maintains flexibility over a wide
temperature range.
Production
H2CCHC
Cl
CH
hυ
2
HC
C
Cl
C
CH
n
Neoprene is produced by free-radical polymerization of 2chlorobutadiene. In commercial production, this polymer is prepared
by free radical emulsion polymerization. Polymerization is initiated
using potassium persulfate. Bifunctional nucleophiles, metal oxides
(e.g. zinc oxide), and thioureas are used to crosslink individual
polymer strands. Outside of Russia and China, about 300000 tons of
neoprene are produced annually.
Applications
General
Neoprene’s relative inertness makes it well suited for
demanding applications such as gaskets, hoses, and corrosionresistant coatings. It can be used as a base for adhesives, noise
isolation in power transformer installations, and as padding in
external metal cases to protect the contents while allowing a snug fit.
It’s fire resistance results in its appearance in weather stripping for
fire doors and in combat related attire such as gloves and face masks.
Because of its tolerance of extreme conditions, neoprene is used to
line landfills.
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Aquatics
Neoprene is commonly used as a material for fly fishing
waders, as it provides excellent insulation against cold. Neoprene
waders are usually about 5 mm thick, and in the medium price range
as compared to cheaper materials such as nylon and rubber.
However, neoprene is less expensive than breathable fabrics. A
foamed neoprene containing gas cells is used as an insulation
material, most notably in wetsuits. Foamed neoprene is also used in
other insulation and shock-protection (packing) applications. In its
native state, neoprene is a very pliable rubber-like material, with no
better insulating properties than rubber or other solid plastics. For
diving and exposure protection applications, neoprene is
manufactured by foaming the plastic with nitrogen gas, for the
insulation properties of the tiny enclosed and separated gas bubbles.
The foam cells thus created also make the material quite buoyant. A
recent advance in neoprene for wet suits is the "super-flex" variety,
which mixes spandex into the neoprene for greater flexibility.
As a result, wetsuit neoprene sheets are manufactured in
different grades dependent on the application. Diving suit neoprene
is denser and less flexible; this ensures its durability and reduces
compression at depth. Sailing wetsuits are never exposed to large
compressive forces and contain more gas, so are warmer for the same
thickness. Competitive swimming wetsuits are made of the most
expanded foam; they have to be very flexible to allow the swimmer
unrestricted movement. The downside is that they are quite fragile.
Home accessories
Recently, neoprene has become a favorite material for
lifestyle and other home accessories including laptop sleeves, tablet
holders, remote controls and cycling chamois. In this market, it
sometimes competes with LRPu (low-resilience polyurethane),
which is a sturdier (more impact-resistant) but less-used material.
Sports
Also in recent years neoprene was incorporated into the
construction of some of popular product-lines, owing to
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reinforcement which neoprene adds to them (ankle support) and
guards against abrasions as few materials do. As a simple matter of
durability and product lifespan, liners constructed with neoprene
additives are typically more expensive than those that are not.
In the equestrian world, it is used in cinches, saddle pads,
bareback pads, and many other applications in all disciplines.
It is often used in Airsoft as a protective garment, as it is thin
enough to feel the hit, but thick enough to reduce the impact velocity,
thus avoiding breakage of the skin by the pellet.
Training knives and swords are made of Neoprene for safe
self-defense instructions, practice, sparring, and martial arts
demonstrations.
Hydroponic Gardening
Hydroponic and aerated gardening systems make use of small
neoprene inserts to hold plants in place while propagating cuttings, or
using net cups. Neoprene is a good choice for supporting plants
because of its flexibility and softness, allowing plants to be held
securely in place without the chance of causing damage to the stem.
Other
Neoprene is used for masks used for face protection, for
insulating CPU sockets, to make waterproof automotive seat covers,
in liquid and sheet-applied elastomeric roof membranes or flashings,
and in a neoprene-spandex mixture for manufacture of wheelchair
positioning harnesses. Because of its chemical resistance and overall
durability, neoprene is sometimes used in the manufacture of
dishwashing gloves, especially as an alternative to latex.
Precautions
Some people are allergic to neoprene while others can get
dermatitis from thioureas residues left from its production. The most
common accelerator in the vulcanization of polychloroprene is
ethylene thiourea (ETU), which has been classified as reprotoxic.
The European rubber industry project called SafeRubber focuses an
alternative to the use of ETU.
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Trade names
Neoprene (Du Pont)
3.10 Polynorbornene
Polynorbornenes are polymers with high glass transition
temperatures and high optical clarity.
[Ru]
n
Norbornenes are the monomers in ring-opening metathesis
polymerizations (ROMP) with for instance the Grubbs' catalyst. In
addition to ROMP polymerization, norbornene monomers also
undergo vinyl-addition polymerization. Ethylidene norbornene is a
related monomer derived from cyclopentadiene and butadiene.
Norbornene or norbornylene or norcamphene is a bridged
cyclic hydrocarbon. It is a white solid with a pungent sour odor. The
molecule consists of a cyclohexene ring with amethylene bridge
between C-3 and C-6. The molecule carries a double bond which
induces significant ring strain and significant reactivity.
Norbornene, like many of its derivatives, is made by a DielsAlder reaction of cyclopentadiene and ethylene. Related bicyclics are
norbornadiene which has the same carbon skeleton but with two
double bonds and norbornane which is completely saturated without
double bonds.
Properties
Reachable performances: Loss factors (tan delta) larger than
3, rebounds of less than 1%, tear strengths of 50 N/mm², friction
coefficients of 2 and more, Shore hardness between 4 and 90 Shore
A.
Application
Polynorbornene is used mainly in the rubber industry for antivibration (rail, building, industry), anti-impact (personal protective
equipment, shoe parts, bumpers) and grip improvement (toy tires,
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racing tires, transmission systems, transports systems for copiers,
m
feeders, etc.).
Second main application: oil-binding system with absorption
capability of hydrocarbons, 10 times of own weight.
Trade names
Norsorex is a brand from Astrotech Advanced
Elastomerproducts GmbH since 2008.
3.11 Chlorinated Polyethylene
CH2CH CH
n
Cl
CH
2
2
Chlorinated Polyethylene (CPE, CM) is a thermoplastic polymer,
composed of high molecular weight polyethylene which has been
chlorinated - a process that yields a flexible rubber-like material.
Properties
Density (g/cm3) 1.16
Surface Hardness SA70
Tensile Strength (MPa) 12.5
Flexural Modulus (GPa) 0.002
Linear Expansion (/°C·10-5) 18
Elongation at Break (%) 700
Strain at Yield (%) N/Y
Max. Operating Temperature (°C) 60
Volume Resistivity (log Ohm·cm) 13
Dielectric Strength (MV/m) 12
Dissipation Factor 1kHz 0.1
Dielectric Constant 1kHz 5.5
Melting Temperature Range (°C) 150 - 170
Mould Shrinkage (%) 3
Mould Temperature Range (°C) 20 - 40
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Advantages
Good UV resistance. Flexible. High tear strength. Good
chemical resistance. Inherently difficult to ignite. CPE offers
excellent compatibility with various polymers. It can be blended with
CR, CSM, NBR,EPDM, SBR and NR in any ratio.
Disadvantages
Evolution of hydrogen chloride during combustion. High gas
permeability.
Application
Mainly used as impact modifier for PVC or compounded with LDPE
or HDPE film to improve toughness. Films used as pond liners and
for agricultural applications. Performs well in automotive,
construction, wire and cable, and a wide variety of plastics
modification applications (ABS, SAN,)
3.12 Chlorosulphonated Polyethylene
Chlorosulphonated polyethylene (CSM, CSPE) is noted for its
resistance to chemicals, temperature extremes, and ultraviolet light. It
was a product of DuPont Performance Elastomers, a subsidiary of
DuPont.
(CH2CH2CH2CHCH2CH2CH2)12(CH)
17
n
SO2ClCl
Chlorosulphonated polyethylene is a product of the chemical
modification of polyethylene by chlorine and sulfur dioxide. It's
density is 1.11–1.26 g/cm3, a chlorine content of 27–45 %, and a
sulfur content of 0.8–2.2 %.
Properties
Owing to the presence of chlorine, CSM is resistant to fire,
oil, and the action of microorganisms and exhibits good adhesion to
various surfaces. It is insoluble in aliphatic hydrocarbons and
alcohols, slightly soluble in ketones and esters, and readily soluble in
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aromatic hydrocarbons, such as toluene and xylene, and in
chlorinated hydrocarbons.
Chlorosulfonated polyethylene is better than others rubbers
because of its resistance to the effects of ozone and inorganic acids,
such as chromic, nitric, sulfuric, and phosphoric acids, as well as to
the effects of concentrated alkalies, chlorine dioxide, and hydrogen
peroxide. It is resistant to light, is impermeable to gas, and has good
dielectric properties. The —SO2Cl groups and labile chlorine atoms
participate in the vulcanization of chlorosulfonated polyethylene; a
typical vulcanizing system consists of MgO, 2mercaptobenzothiazole, diphenylguanidine, and rosin. The tensile
strength of pure rubbers made of chlorosulfonated polyethylene may
reach 32 MN/m2 (320 kilograms-force/cm2), with a relative
elongation of 350–600 percent. Such rubbers have high resistance to
wear and repeated deformation. The temperature range for their most
efficient use is from –60° to 180°C. CSM made from high-density
polyethylene may also be used in unvulcanized form.
Application
Chlorosulfonated polyethylene is used in the production of
industrial and household goods and of anticorrosion coatings to be
applied by the rubberizing method. It is used for insulating various
cables, including ship cables. It is also used as a film-forming agent
in varnishes and paints for the preservation of wood, metal, and
reinforced concrete and as a base for adhesives and hermetic
sealants.
Along with PVC, CSM is one of the most common materials
used to make inflatable boats and folding kayaks. It is also used in
roofing materials, and as a surface coat material on radomes, owing
to its radar-transparent quality.
Hypalon is also used in the construction of the decking of
modern snowshoes, replacing neoprene, as a lighter, stronger
alternative.
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Trade names
m
A trademark for chlorosulfonated polyethylene (CSPE)
synthetic rubber (CSM) is Hypalon. Hypalon has become the
common name for all kinds of CSM, even though DuPont was not
the only manufacturer. Tosoh Corporation of Japan produces CSM
under the trade names Toso-CSM and extos. The trade name of
chlorosulfonated polyethylene in Russia is KhSPE.
Now DuPont Performance Elastomers's sole plant for CSM
materials is closed.
3.13 Ethylene-Vinyl Acetate Copolymer
Ethylene-vinyl acetate copolymer (EVA, EAM) is a general-purpose
thermoplast.
CH2CH
2
CH2CH
n
O
C
OH3C
EVAs are the products obtained by copolymerization of
ethylene with other monomers and different monomers grafting to
the polyethylene macromolecule or ethylene grafting to other
polymer macromolecule.
Properties
Elastic crystallized material, resembling high-density
polyethylene, but more transparent, flexible (especially at low
temperatures), and having a lower hardness. Allows heating up to
80°C. Melting point: 61-108°C. Brittle temperature: -65/-100°C. The
material properties are highly dependent on the content of vinyl
acetate (5 to 50%, the material with less than 5% of vinyl acetate
content are LDPE) and flow. With increasing content of vinyl acetate
the crystallinity decreases, the resistance to lubricants and oils rises.
Compared with LDPE, the material has lower barrier properties to
gases and water vapor, less chemical resistance and heat resistance.
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