寻UL 157 Gasket Tensile Strength & Elongation Test, Hardness Test

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UL157 Gaskets and Seals

5 Tensile Strength and Ultimate Elongation Test
# _0 i2 |/ r  r, k' o5.1 General
# E, K9 c7 |& l# B5.1.1 The tensile strength and ultimate elongation tests are to be conducted on all materials except that elongation tests need not be conducted for composite gasket materials.
1 V5 ^5 j! J+ h1 e4 R5.2 Apparatus
* L! v; \% W) J; ]- S9 p8 m% ^% U8 j5.2.1 The buffing or skiving equipment is to be as specified in Standard Practice for Rubber– Preparation of Pieces for Test Purposes from Products, ASTM D3183-84 (1992).
1 j: M3 V* m0 H1 L- d4 r% |5.2.2 Dies A, C or D are to be as specified in Standard Test Methods for Rubber Properties in Tension, ASTM D412-92.
5.2.3 A micrometer or equivalent is to be used for measuring dumbbell specimens as specified in Method A, Standard Practice for Rubber – Measurement of Dimensions, ASTM D3767-84 (1992).
$ D) C/ Y2 l+ x" ^5.2.4 A micrometer or equivalent is to be used for measuring flexible cellular material as specified in Standard Specification for Flexible Cellular Materials – Sponge or Expanded Rubber, ASTM D1056-91 .
5.2.5 A micrometer or equivalent is to be used for measuring ²O² rings as specified in Method C, Standard Methods of Testing Rubber O-Rings, ASTM D1414-94.
! |& c2 q0 ?) K3 [( f3 p6 ?4 i5.2.6 A bench marker, if required, is to be as specified in Standard Test Methods for Rubber Properties in Tension, ASTM D412-92.
( F& F4 N, m1 ], X# @' p5.2.7 Tensile test equipment is to be as specified in Standard Test Methods for Rubber Properties in Tension, ASTM D412-92.
5.2.8 An extensometer, scale, or other device is to be capable of indicating the elongation with an accuracy of 0.1 inch (2.5 mm).
5.3 Specimens
5.3.1 Tensile strength and elongation test specimens are to be as specified in Table 5.1.
5.4 Method
5.4.1 A set of three specimens is to be used for the tensile strength and elongation tests. See Table 5.1 for specimen preparation.
# T, J6 D& L5 M6 d5.4.2 For elongation, two benchmarks, 1 inch (25 mm) apart, are to be marked on the central portion of each specimen. If an extensometer is used that does not require bench marks, the bench marks may be omitted. The specimens are to be conditioned for a minimum of 1/2 hour under the conditions specified in 4.3.
; c: C+ f& ?9 a& _: h5.4.3 Tensile strength and ultimate elongation of the specimens of gasket and seal materials is to be determined in accordance with 5.4.4 – 5.4.7 using a power-driven testing machine as specified in the Test Methods for Rubber Properties in Tension, ASTM D412-92.
5.4.4 The rate of travel of the power-actuated grip is to be:
0 G1 B6 o4 j  F) K& H/ {a) 5 ±1/4 inches (127.0 ±6.4 mm) per minute for Composite Gasket Material, and
b) 20 ±1 inches (508.0 ±25.4 mm) per minute for all other gaskets and seal materials.
$ {! o9 d( K7 ?3 C# B5.4.5 The elongation, if required, is to be measured by means of a scale, extensometer, or other device indicating the elongation with an accuracy of 0.1 inch (2.5 mm).
. E: K& i" U& {5.4.6 After conditioning the specimen is to be placed in the grips of the power-driven testing machine so that the bench marks are between and not covered by the grips. The movable grip is to be adjusted to make the specimen taut but not under tension. The grips are to be separated at the rate specified in 5.4.4 until rupture. During separation, the distance between bench marks is to be measured an recorded at
. Q2 S( [- e9 }. e" }: zthe point of rupture to the nearest 0.1 inch (2.5 mm).
4 u( P7 o, X% J* V/ s% `5.4.7 Calculations are to be made for each of the specimens and averaged using the following formulas.
) j/ ~- w& Y2 }' |Specimen measurements for the calculation of the area are to be made before aging and exposure.
a) Tensile strength, psi equals F/A in which:
! w, i4 Z' y# D+ dF is the maximum observed force in pounds.
5 U5 z- q$ r7 q, q0 @A is the cross-sectional area of the unstressed specimen in square inches. See (b) – (e).
b) Cross-sectional area of die-cut or straight specimen equals W x T in which:
W is the width of the constricted portion of the die-cut or straight specimen in inches.
* N7 ~( N9 z, H+ Y, nT is the minimum thickness of the specimen in inches.
+ Y: L( f0 M8 D/ V7 @c) Cross-sectional area of ²O² ring specimens and specimens with a circular cross-section equals 0.7854 D2 in which:
( g1 Z1 a3 Q& m& X+ j+ f: H  |D is the cross-sectional diameter in inches as measured in accordance with Table 5.1.
7 r9 I  o5 n" J$ q, g3 Od) Cross-sectional area of tubular specimen equals 0.7854 (D2 – d2) in which:
% }$ r9 Y( Z1 z4 c! d' b( dD is the outside diameter in inches and d is the internal diameter in inches.
e) Cross-sectional area for irregular shaped specimens equals W/163.87G in which:
, @$ v* O; {2 j8 B7 |W is the grams mass (to the nearest 0.005 g) of a specimen length or lengths totaling 10 inches (254 mm).
G is the specific gravity of the compound. The specific gravity may be determined by means of the following: G = W1/(W1+W3-W2) in which:
# z1 O3 F( u  P$ f% T6 |  A+ ?W1 is the gram mass on the balance pan of the specimen (to the nearest 0.005 g).
% b; d0 j: y' h9 |& G4 S( b0 oW2 is the gram mass of the fully immersed specimen and its partially immersed suspending wire (to the nearest 0.005 g).
% t' x! O" X, p; I* z  |W3 is the gram mass of the partially immersed suspending wire.
* b, s/ e' h  P* r  dReference may be made to Test Method for Specific Gravity and Density of Plastics by Displacement, ASTM D792-91.
f) Elongation percent equals [(L-Lo)/Lo] x 100 in which:
  l6 w& N" u: V' d3 w9 JL is the measured distance between the bench marks at rupture.
Lo is the original distance between the bench marks.

2 r6 [- m1 u4 y
9 Hardness Test
9.1 General
: A4 U2 D6 v* Z/ M( N9.1.1 The hardness test is to be conducted on solid elastomer, the elastomer portion of coated fabrics and thermoplastic material. See Table 4.1 for the requirement.
9.2 Apparatus
" f( P% f3 x7 l* P' K7 P7 G. ?9.2.1 The apparatus is to be as specified in Standard Test Method for Rubber Property – Durometer Hardness, ASTM D2240-91 and Tests for Rubber Deterioration in an Air Oven, ASTM D573-88(1994).
. R/ A. Z( k- e9.3 Specimens
9.3.1 The specimens are to be as specified in ASTM D2240-91. Three specimens are to be used for each test.
9 E$ U4 |: ^2 M% B. k4 C9.4 Method
2 f2 ], ~; d, o! ]- A9.4.1 The test is to be as specified in ASTM D2240-91 and is to be conducted on the same specimens before and after aging in accordance with Table 4.3. The conditioning for the as-received measurements is to be at least 1/2 hour at 23 ±2°C (73 ±3.6°F). The conditioning for the aged measurements is to be not less than 16 hours and not more than 96 hours at 23 ±2°C. The hardness is the average of the three specimens.