文档介绍：相对温度指数相对温度指数(relative temperature index, RTI): UL 对材料所做的一种长期(6000-20000 小时) 操作温度测试。 RTI 不同于热变型温度(HDT) ,热变型温度乃是一种短期间于一定压力下的待测体变形的温度。了解塑料的长期使用温度,一般情况下都是看 UL 黄卡中的 RTI 值(相对温度指数),也有用 CUT 值(半生命周期连续使用温度)表示,或者用 ARO 值(热老化实际工作值)来表示。 RTI, Elec RTI, Mech w/impact RTI, Mech, w/o impact Elec --Electrical 表示对于电气特性的; Imp--Impact 表示有冲击负荷时的; str 表示静态下的; Mech--Mechanical- 机械条件下; w/impact- 有冲击条件下; W/o Imp--Without Impact- 无冲击条件下 UL94 测试的第二部分是确定材料的相对温度指数(RTI) 。 RTI 是一个特定温度,材料置于该温度中 60,000 小时后其特性的原始值降至二分之一。如果未经测试, 则该材料采用普通级 RTI 。 RTI 值越高, 通常代表该材料等级越高。 Coefficient of Linear Thermal Expansion(CLTE) 的定义: Like metals, thermoplastic materials expand when heated and contract when cooled. Generally, fo ra given change in temperature, plastic materials change dimensionally much more than metals. The coefficient of linear thermal expansion, CLTE, is the ratio of the change ofa linear dimensio n to the original dimension of the material for a unit change of temperature. It is generally given in units of in./in./ °F or cm/cm/ ° C. Table 1 presents typical values for many c ommon materials. This isa very important consideration if dissimilar materials are to be assembl ed. It should be noted that many thermoplastics, especially those with glass reinforcement or liqui d crystalline resins, may have different coefficients for the mold flow, cross-flow, and thickness direc tions. Since the CLTE of plastics can var