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橡胶原材料知识-生胶篇-第八章1 o% O7 d. e) A. z9 w
乙烯丙烯酸酯橡胶' ~! {8 p9 U: }& v- u% i3 C9 ]
Ethylene acrylic elastomers-AEM-Vamac®7 c4 D$ ] P# c7 E/ T
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Vamac® ethylene acrylic elastomer (AEM) products are a comprehensive family of heat and fluid resistant elastomers for flexible applications ranging from hoses, dampers and boots to seals and gaskets. Vamac® provides significant performance advantages over low temperature ACM and HNBR grades, including better low temperature resistance and high temperature performance up to 175°C. Compared to HNBR substantial cost savings can be achieved.
. H/ j, b( |9 h2 ~' w# P; ?* v5 xVamac® ethylene acrylic elastomers can be made into cured compounds that have excellent resistance to high temperatures and good resistance to automotive fluids such as transmission fluids and engine oils.
4 A9 Y( k( w; M9 C1 K: e0 J- z! eLOW-TEMPERATURE PERFORMANCE
% p& @' v. {$ q! `4 LThe low-temperature performance of Vamac® surpasses that of most other heat- and oil-resistant polymers. Typical compounds are flexible at temperatures of -40℃(-40℉). For flexibility at even lower temperatures, plasticizers can be used.
& f. K8 a. q4 N! URESISTANCE TO FLUIDS
( o9 J3 ^8 z9 i5 G# s' j+ J. w7 Y9 R" `End products based on Vamac® have excellent resistance to hot oils and hydrocarbon- or glycol-based lubricants, transmission fluids, and power steering fluids. Low oil swell can be obtained with proper Vamac® grade selection and compounding.
4 N, N/ _: d, q/ X$ fVamac® is not recommended for use in components immersed in gasoline or highly aromatic fluids, but can be used as a cover material in fuel line applications to reduce costs. g! Z# u' X; W, ]0 H) A" [
EXCELLENT VIBRATION DAMPING ABILITY. Z2 n6 x n! n3 P& U* T
The high vibrational damping characteristic of Vamac® remains nearly constant over broad ranges of temperature, frequency and amplitude.
Z. p( Q7 I8 n% ?/ kLOW FIRE/SMOKE HAZARD/ @9 L& n8 H2 z' o
Vamac® ethylene acrylic elastomer is not inherently resistant to burning. However, when properly compounded, a wire jacket of Vamac® will pass the demanding UL-44 vertical wire flame test, generating very low smoke compared to other flame-resistant materials and provide non-halogen off-gases in fire situations.
' j4 L. \7 h3 D% F4 D# Y3 IHIGH-TEMPERATURE DURABILITY
9 j/ G! h# h+ p4 `( [Parts made with Vamac® retain elasticity and remain functional after continuous air-oven exposures. Typical times and temperatures are six weeks at 160℃(330℉),18months at 121℃(250℉) or five days at 204℃(400℉). Vamac® Ultra IP provides improved high-temperature durability (6 weeks at 175℃(347℉))7 i8 q$ \0 O8 L' y+ X( d
COMPRESSIVE STRESS RELAXATION
! k2 Y; t. s8 ^+ W* wVamac® compounds perform exceptionally well in seal and gasket applications and have shown good performance in engine oils out to 5000 hours at 150℃(302℉).8 R8 |! {4 q9 l
GRADE SELECTION CRITERIA
. V7 v9 {" A( M, e1 HBasic Heat and Oil Swell Characteristics
, b! R/ h5 G( I/ T4 eCompounds based on Vamac® G and Vamac® DP typically exhibit IRM903 oil swell of 40-60%. If compounded appropriately, the polymer can withstand 6 weeks of continuous use at 175℃(347℉), maintaining 50% elongation. Vamac® is generally assigned an ASTM D2000/SAE200 rating of EG or EF.
$ J/ l3 j1 M9 X" s& hFor Reduced Oil Swell2 Z9 c2 @8 t) `2 }: w9 e& V. ?8 M
For reduced oil swell, Vamac® GLS exhibits about one half the IRM903 oil swell of its G counterpart. However, its lower oil swell is accompanied by a reduction (by 7℃) in low-temperature flexibility.5 s$ W* V& Q6 _+ L
For High-Temperature Dynamic Performance+ s. F' P6 n9 }' l) M$ K) o
Compounds with Vamac® GXF have improved tensile properties and dynamic fatigue resistance at elevated temperatures compared to Vamac® G. At 150℃, tensile strength, ultimate elongation are 12% higher; DeMattia fatigue results show over a 150% improvement. Cure times for Vamac® GXF are slightly longer, compression sets higher than Vamac® G.0 \* o3 x6 `- V( P% n x
For Molding or Extrusion7 C# j& o" l% a
Vamac® Ultra IP can vastly improve productivity through reduced mold fouling, scrap, improved hot tear resistance and cycle time compared with core Vamac® G product. With higher viscosity, Vamac® Ultra IP provides superior compound dispersion with a 1-pass mix and extruded profile stability.! R4 O2 N9 t: V3 {
For Low-Temperature, Dynamic Performance4 x0 f' f6 c& C3 Y$ d
Vamac® Ultra LT delivers low temperature flexibility down to -40℃ and lower in service with fewer performance-draining plasticizers, especially for use in automotive hoses and boots as well as dampers where functional performance is required throughout a thermal range as wide as -54℃ to 160℃.
" _5 d! r0 {& k* }& l# QVamac® invites opportunities to help you formulate compounds to meet specific processing.
; @3 d$ V+ A8 m) [0 p1 `Curing Method # P }9 R8 q6 [$ x
Diamine-cured terpolymer, Vamac® G, is used for most applications. If postcure is impractical or undesirable, Vamac® DP peroxide-cured dipolymer can be used.
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Note:The above from http://www.dupontelastomers.com. |
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