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相對(duì)熱指數(shù) (Relative Thermal Index, 以下簡(jiǎn)稱RTI) 為UL高性能塑料材料認(rèn)證的重要參數(shù)之一。RTI的評(píng)估，主要依據(jù)UL 746B標(biāo)準(zhǔn)(Polymeric Materials – Long Term Property Evaluations) 的長(zhǎng)期老化測(cè)試方案 (Long Term Thermal Aging program, 以下簡(jiǎn)稱LTTA) 來(lái)進(jìn)行測(cè)試與分析。

LTTA評(píng)估方案的核心原理來(lái)自于阿倫尼烏斯方程(Arrhenius Equation)，俗稱時(shí)溫等效原理。通過(guò)在較高的溫度下，進(jìn)行相對(duì)較短時(shí)間的實(shí)驗(yàn)。在獲取到材料性能衰退行為的時(shí)間-溫度數(shù)據(jù)組合后，根據(jù)阿倫尼烏斯方程進(jìn)行線性回歸處理，最后綜合評(píng)估以獲得材料性能在相對(duì)長(zhǎng)期使用時(shí)能承受的溫度等級(jí)。

一般而言，您可以根據(jù)材料及性能，選定合適的溫度進(jìn)行長(zhǎng)時(shí)間的老化評(píng)估，直至材料衰退完成。即按照固定溫度法 (Fix-Temperature bbbbbb) 進(jìn)行研究。此方法適合于實(shí)驗(yàn)設(shè)備（高溫烘箱）相對(duì)有限的實(shí)驗(yàn)室。并且對(duì)于大多數(shù)的材料，隨時(shí)間推進(jìn)，皆能獲得材料性能衰退的數(shù)據(jù)，以評(píng)估最終RTI結(jié)果。也正因?yàn)槿绱耍?span style="font-family:Arial, sans-serif;line-height:26px !important;">“時(shí)間”將很有可能成為該評(píng)估方法的zuida成本占比。而且具體完成時(shí)間也無(wú)法在研究開(kāi)始之初作出準(zhǔn)確的預(yù)估。

實(shí)際上，根據(jù)UL 746B標(biāo)準(zhǔn)的描述，依據(jù)相同的原理，還可以從另外一個(gè)角度考慮評(píng)估方案。

以多個(gè)高溫烘箱（通常最少6個(gè)以上）同時(shí)進(jìn)行材料老化試驗(yàn)，選定合適的時(shí)間點(diǎn)獲取不同溫度下的材料性能衰退數(shù)據(jù)。即按照固定時(shí)間法 (Fix-Time bbbbbb) 進(jìn)行研究。此方法適合于設(shè)備相對(duì)充足的實(shí)驗(yàn)室。顯而易見(jiàn)，該方法能夠在研究開(kāi)始階段即可規(guī)劃取樣時(shí)間點(diǎn)，并能更準(zhǔn)確的預(yù)計(jì)研究完成時(shí)間。

在實(shí)際測(cè)試中, 可考慮先按照固定時(shí)間法進(jìn)行規(guī)劃，視乎材料性能衰退行為，有必要時(shí)轉(zhuǎn)至固定溫度法評(píng)估。以期達(dá)到時(shí)效與風(fēng)險(xiǎn)可控兩方面的優(yōu)點(diǎn)。

UL 94 是應(yīng)用最廣泛的塑料材料阻燃性能評(píng)價(jià)標(biāo)準(zhǔn)，共有 12 種等級(jí)：HB、V-0、V-1、V-2、5VA、5VB、VTM-0、VTM-1、VTM-2、HBF、HF-1、HF-2。

UL 94 用來(lái)評(píng)價(jià)材料在被點(diǎn)燃后火焰熄滅的能力。根據(jù)燃燒速度、燃燒時(shí)間、抗滴落能力以及滴落物是否燃燒等有多種評(píng)判方法。每種被測(cè)材料根據(jù)顏色或厚度都可以得到許多值。當(dāng)選定某個(gè)產(chǎn)品的材料時(shí)，其 UL 等級(jí)應(yīng)滿足塑料零件壁部分的厚度要求。UL 等級(jí)必須與厚度值一起報(bào)告。

1 Scope

1.1 These requirements cover tests for flammability of polymeric materials used for parts in devices and appliances. They are intended to serve as a preliminary indication of their acceptability with respect to flammability for a particular application.

1.2 The methods described in this Standard involve standard size specimens and are intended to be used solely to measure and describe the flammability properties of materials, used in devices and appliances, in response to a small open flame or radiant heat source under controlled laboratory conditions.

1.3 The tests in the Standard for Tests for Flammability of Small Polymeric Component Materials should be used to evaluate small components which contain materials that can not be fabricated into standardized specimens in the minimum use thickness and subjected to applicable preselection tests in UL 94. Test procedures in UL 1694 are applicable to small components with an overall volume of less than 2500 mm3 (0.15 in3). UL 1694 is generally not applicable to small components with an overall volume greater than 2500 mm3 (0.15 in3).

1.4 The final acceptance of the material is dependent upon its use in complete equipment that conforms with the standards applicable to such equipment. The flammability classification required of a material is dependent upon the equipment or device involved and the particular use of the material. The performance level of a material determined by these methods shall not be assumed to correlate with its performance in end-use application. The actual response to heat and flame of materials depends upon the size and bbbb, and also on the end-use of the product using the material. Assessment of other important characteristics in the end-use application includes, but is not limited to, factors such as ease of ignition, burning rate, flame spread, fuel contribution, intensity of burning, and products of combustion.

1.5 If found to be appropriate, the requirements are applied to other nonmetallic materials.

1.6 These tests, with the exception of the Radiant Panel Test in Section 10, are not applicable to the evaluation of parts where the thickness exceeds 13.0 mm or where the surface area exceeds 1 m2. These requirements do not cover polymeric materials when used for building construction, finishing, or contents such as wall and floor coverings, furnishings, decorative objects and so forth. In addition, the fire resistance (in terms of an hourly rating), flame spread, smoke characterization, and heat release rate is not evaluated. Other fire tests exist and shall be used to evaluate the flammability of materials in the intended end-use-product configuration.

代理范圍:

(一)水平燃燒測(cè)試,94HB,并指導(dǎo)前期打樣送測(cè);

(二)垂直燃燒測(cè)試,94V-2,94V-1,94V-0,并指導(dǎo)前期打樣送測(cè);

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