To: Kendy regarding to UL plastic IMP 和STR

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Kendy(313208377) 14:43:34
XDJM，UL网站上查到的塑料件UL证书上：RTI  下面有两栏：ELEC（电器）和MECH（机械）； MECH（机械）下面又有两栏：IMP 和STR 。IMP 和STR 是不是分别代表结构件和冲击件，两者有什么区别？
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/ g7 v/ h5 P9 _+ K6 ?( wThermal-Aging Program
7 Z- E- f. `8 u6 y! U2 ?: y) R# i% RThe materials covered by this program have, in many cases, been investigated with respect to retention of certain critical properties (e.g. dielectric, tensile, impact, and the like) as part of a longtime thermal-aging program conducted in accordance with Underwriters Laboratories Inc. Standard for Polymeric Materials-Long Term Property Evaluations, UL 746B.

  l+ l3 P5 E. P5 {% z& C  v0 BThe end-of-life of a material at each test temperature in this program has been assumed to be the time when the value of the critical property had decreased to 50 percent of its original (as received) value. If a material has been investigated under the thermal-aging program, the Relative Temperature Index (RTI), in degrees C shown is based on a comparison with a material which has acceptable service experience and correlates numerically with the temperatures above which the material is likely to degrade prematurely.
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If a material has not been investigated under the thermal-aging program, the temperature index shown is based on the generic class of the material. A tabulation of the temperature indices according to generic material class is included in UL 746B and is based on past field-test performance and chemical structure.

More than one RTI may be appropriate for a given material depending on the property requirements for a given application. In certain cases, higher temperatures are permitted if so specified by the end-use product standard.
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  M# G3 ?& f$ ]% g# r5 oRelative Temperature Index (RTI)
Maximum service temperature for a material, where a class of critical property will not be unacceptably compromised through chemical thermal degradation, over the reasonable life of an electrical product, relative to a reference material having a confirmed, acceptable corresponding performance defined RTI.

RTI Elec
3 w* o5 J" [6 ?5 G8 f( BElectrical RTI, associated with critical electrical insulating properties.
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" K1 g7 q5 X/ _) v( {RTI Mech Imp
$ ^; x) w6 H5 N5 G, ?Mechanical Impact RTI, associated with critical impact resistance, resilience and flexibility properties.

7 ^8 Y1 K" Z. a/ F2 Z; W+ [! y2 aRTI Mech Str
' T2 f6 f' s  [9 g9 E( p8 OMechanical Strength (Mechanical without Impact) RTI, associated with critical mechanical strength where impact resistance, resilience and flexibility are not essential.
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http://www.ul.com/plastics/thermal.html