Tài liệu trích trên mạng dành cho nhân viên công nghệ cty Cao su Việt
Cao su EPDM xứng đáng với sự tin cậy của người tiêu dùng khi sử dụng nguyên liệu này. Có nhiều mã hàng phù hợp cho sự lựa chọn đa dạng từ yêu cầu sốc nhiệt ở nhiệt độ khoảng trên dưới 150 oC, khả năng kháng hóa chất, khả năng thích nghi trong điều kiện va đập khó chịu, và thích nghi với môi trường tiếp xúc với thực phẩm......
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Mời các bạn tham khảo:
http://www.timcorubber.com/rubber-materials/epdm.htm
Product
Description
EPDM (Ethylene Propylene Diene
Monomer) Rubber has outstanding resistance to aging, weathering, ozone, oxygen
and many chemicals. It offers excellent high and low temperature stability,
plus steam and water resistance. In general, EPDM has dynamic and mechanical
properties between natural rubber and SBR.
 |
| Cao su EPDM là một sự lựa chọn |
- Automotive weather-stripping and seals
- EPDM Tubing
- Belts
- Electrical insulation
- Rubber mechanical goods
- Washing machines/dishwashers
- Hydraulic brake systems
NOTE: EPDM should not be used where continual contact with petroleum based products is required.
EPDM Rubber
Material Properties
Common
Names
|
EPDM, EPR,
EPT
|
ASTM
D-2000 Classification
|
CA
|
Military
(MIL-STD 417)
|
RS
|
Chemical
Definition
|
Ethylene
Propylene
|
General Characteristics |
|
Durometer
Range (Shore A)
|
30-90
|
Tensile
Range (P.S.I)
|
500-2500
|
Elongation
(Max %)
|
600
|
Compression
Set
|
Good
|
Resilience
– Rebound
|
Good
|
Abrasion
Resistance
|
Good
|
Tear
Resistance
|
Fair
|
Solvent
Resistance
|
Poor
|
Oil
Resistance
|
Poor
|
Low
Temperature Usage (F°)
|
-20° to
-60°
|
High
Temperature Usage (F°)
|
Up to 350°
|
Aging
Weather – Sunlight
|
Excellent
|
Adhesion
to Metals
|
Fair to
Good
|
 |
| Cao su EPDM được dùng cho van cánh bướm |
Comment – Ethylene Propylene is a polymer that exhibits outstanding properties. It has exceptionally good weather aging resistance as well as resistance to water, chemicals, and ozone. EPDM also shows an excellent resistance to gas permeability and aging due to steam exposure. It is an excellent polymer to use in high temperature applications as it is heat resistant up to 350°F. Ethylene Propylene provides poor resistance to oil and solvents; however it is fairly good in its resistance to ketones and alcohols. EPDM is not recommended for usage in food applications or those that expose it to aromatic hydrocarbons.
EPDM Rubber
Applications
EPDM's properties allow it to be a
widely used, highly versatile, synthetic rubber in both specialty and general
purpose applications. Since EPDM can be processed to meet a number of different
requirements, it has been adopted by many industries for a number of
applications including:
- Automotive weatherstripping
- Glass-run channels
- EPDM Grommets
- Automotive seals
- Radiator, garden and appliance EPDM hoses
- EPDM Tubing
- Electrical insulations and stinger covers
- Roofing membranes
- EPDM belts
- Plastic impact modification
- Rubber mechanical goods
- Water system O rings and hoses
- Ozone exposure applications
- Automotive cooling systems
Chemistry and Compounding
 |
| Cao su EPDM thực phẩm thường được dùng ưu tiên |
When compounded and combined, the
ethylene and propylene monomers of EPDM form a chemically saturated, stable
backbone that provides excellent resistances to ozone, heat, oxidation and
weathering. From here, a third non-conjugated monomer of diene can be
terpolymerized to the polymer to maintain a saturated backbone and subsequently
place the reactive unsaturation in a side chain, making it available for
vulcanization or polymer modification chemistry. The resulting terpolymers
created are referred to as EPDM.
Structure of
EPDM containing ENB
 |
| EPDM có mã hàng phù hợp thực phẩm |
The two most commonly used diene termonomers in the creation of EPDM are ethylidene norbornene (ENB) and dicyclopentadiene (DCPD). These respective dienes will incorporate with the polymer differently, each with their own tendency for introducing long chain branching (LCB), or polymer side chains, that will ultimately influence the vulcanization rates by sulfur or peroxide cures. The following table summarizes the characteristics of the cures using both the ENB and DCPD termonomers.
Termonomer |
Cure & Property Features |
Long Chain Branching |
ENB
|
Fastest
and Highest state of cure
Good tensile strength Good compression set resistance |
Low to
Moderate
|
DCPD
|
Slow
Sulfur Cure
Good compression set resistance |
High
|
Features of EPDM Elastomers
The different properties of a
finished EPDM compound will be largely controlled by the ethylene and diene
content, the Mooney viscosity and the molecular weight distribution. Example –
Lowering ethylene content will decrease crystallinity and thus decrease
hardness and modulus. The follow table highlights some of the general features
in compounding EPDM and the results of having higher or lower levels of
specific attributes.
Characteristics
|
High
|
Low
|
Ethylene
Content
|
Flow at
High Extrusion Temps.
High tensile strength, modulus Good Green Strength High Loading (Reducing Cost) |
Fast
Mixing
Calendering and Milling Low Hardness and Modulus Low Temp. Flexibility |
Diene
Content
|
Acceleration
Versatility
High Modulus, Low Set Good Compression Set Cure Degree and Fast Rate |
High Heat
Stability
Low Hardness and Modulus Scorch Resistance |
Molecular
Weight
|
Good
Modulus and Set
High Loading and Oil Extension Good Green Strength Good Tensile and Tear Resistance Collapse Resistance |
High
extrusion rates
Low Viscosity, Scorch Resistance Good Calendering Fast mixing |
MWD
|
Good
overall processing
Collapse Resistance Good Milling and Calendering Extrusion feed and smoothness |
Fast
extrusion rate
High Cure Low Die Swell Good Physicals |
Manufacturing Processes
EPDM can be manufactured commercially in three major processes, solution, slurry (suspension), and gas-phase.
 |
| EPDM phù hợp tiêu chuẩn FDA |
The process of solution
polymerization is a widely used method which is highly versatile in making a
wide range of polymers. In this process, polymerization of the ethylene,
propylene and catalyst systems takes place in an excess of hydrocarbon solvent.
If the compound requires stabilizers and oils, they are added directly after
polymerization. Following this, the solvent and unreacted monomers are flashed
of by mechanical devolatilization or by using hot water or steam leaving only
the EPDM compound. The remaining polymer, which is in crumb form, is next dried
using either mechanical press, drying ovens, or dewatering in screens. From
here, the crumb can be formed into bales or extruded into pellets.
Gas-phase polymerization was
developed for the manufacturing of ethylene-propylene rubbers. It involves a
reactor that consists of a vertical fluidized bed into which the monomers,
catalysts and nitrogen in gas form are fed, and solid product is removed. The
intense heat of the reaction is removed through the use of circulating gas
which also will serve to fluidize the polymer bed. In gas-phase polymerization,
solvents are not used thus eliminating the needs for solvent stripping, washing
and drying. However, when engaging in this process, continuous injection of a
substantial amount of carbon black is necessary. This additive acts as a
partitioning aid which prevents the polymer granules from sticking to each
other and the reactor walls. To enable rapid mixing, products are made in
granular form.
.....
Nguồn:
http://www.timcorubber.com/rubber-materials/epdm.htm