塑料阻燃性深度总结

塑料阻燃性深度总结

原著：SERGEI V. L EVCHIK

1.1 引言

1.2 聚合物燃烧与测试

1.2.1 可燃性的实验室测试

1、Flammability of polymers is assessed primarily through ignitability, flame spread, and heat release。

聚合物的燃烧性主要从易燃性、火焰传播性、释热性三个方面进行评估。

2、Numerous flammability tests are known and are performed either on representative samples or on an assemble d product. Tests can be small, intermediate, or full scale。

许多可燃性测试可用试样或最终产品进行，在规模上分为小型、中型及大型测试。

3、A V-0 classification is given to material that is extinguished in less than 10 s after any flame application. The mean combustion time for the five specimens tested (10 flame applications) should not exceed 5 s, and no combustible drips can be observed. A V-1 classification is received by a sample with maximum combustion time < 50 s and mean combustion time for five specimens < 25 s. No combustible drips should be observed. The sample is classified V-2 if it satisfies the combustion time criteria of V-1 but flammable drips igniting the cotton are allowed。

UL94V0级评定标准：每次点燃后10s内即发生自熄，5个试样（10次点燃）的平均燃烧时间不超过5s，无具有引燃性的熔融滴落。V-1级评定标准：试样最长的燃烧时间小于30s，平均燃烧时间小于25s，无具有引燃性的熔融滴落。V-2级评定标准：符合V-1级标准的燃烧时间限制，允许具有引燃性的熔融滴落。

4、The LOI test does not represent a real fire scenario, but it is good as a screening tool because it gives a numerical value instead of a discrete classification (e.g., V-0, V-1, V-2).

虽然LOI法仅能测试实验室条件而非真实火情下材料的易燃性，但其可提供较详实的数据而非不连贯的等级划分(例如, V-0, V-1, V-2)。

5、The cone calorimeter test is a bench-scale (medium-sized) test developed at NIST which quickly gained popularity in the academic community as well as for standardization purposes (e.g., ISO 5660-1, ASTM E-1354). It is also used as a tool for fire protection engineering because it allows prediction of large-scale test results. A cone calorimeter measures consumption of oxygen from a burning sample 100 ×100 mm in area and up to 50 mm thick. The heat release is calculated from the oxygen consumption data.

锥形量热仪测试法是美国国家标准及技术研究院（NIST）制定与规范的一个中等规模实验室测试法，它很快得到了学术界的普遍认可，并为其制定了相关标准(例如 ISO 5660-1,

ASTM E-1354)。因该法所得数据与大规模测试所得数据具有一定的相关性，故它也是研究火安全防护工程的重要方法。Cone法可测试面积为100mm×100mm、厚度不超过50mm试样的燃烧耗氧量，并由耗氧量计得样品的释热量。

1.2.2 聚合物的燃烧

6、Ignitability depends to a large extent on how quickly the surface can be raised to the ignition temperature. Special consideration has to be given to polymers that melt before thermal decomposition. Usually, at a low heat exposure, melting precedes ignition and the polymer can or , removing heat from the surface.This phenomenon is beneficial for flame retardancy of uncharrable polymers. On the other hand, at a higher heat exposure, ignition may occur before the surface is heated to sufficient depth for the melted material to flow, and such polymers may ignite relatively easy.

材料的易燃性在很大程度上取决于材料表面温度上升到燃点的速度。人们异常关注熔融温度低于热降解温度的聚合物。通常暴露于较小热源时，如果材料在被点燃之前为熔融态，则可通过流动和熔滴来降低表面热量。这十分有益于非成炭类聚合物的阻燃。相反，暴露于较大热源时，材料在可为熔融流动态之前即被点燃，该类聚合物则相对易燃。

7、The possibility of extinguishing a polymer flame depends on the mechanism of thermal decomposition of the polymer. Whereas ignition of a polymer correlates primarily with the initial temperature of decomposition, steady combustion is related to the tendency of the polymer to yield a char, which is produced at the expense of combustible volatile fragments.

聚合物的自熄性取决于其热降解机理，其易燃性则相关于其热降解的初始温度，稳定燃烧则与其成炭性相关，成炭性越好，可燃性挥发物则越少。

8、Four general mechanisms are important for thermal decomposition of polymers: (1) random chain scission, in which the polymer backbone is randomly split into smaller fragments; (2) chain-end scission, in which the polymer depolymerizes from the chain ends; (3) elimination of pendant groups without breaking of the backbone; and (4) cross-linking. Only a few polymers decompose pre-dominantly through one mechanism; in many cases a combination of two ormore mechanisms is in effect. For example, polyethylene and polypropylene tend primarily to decompose via random chain scission, which in the case of polyethylene is also accompanied by some cross-linking. Poly(methyl methacrylate) and polystyrene tend to depolymerize, poly(vinyl chloride) primarily undergoes elimination of pendant groups (dehydrochlorination), and polyacrylonitrile crosslinks. In terms of flammability, random scission and depolymerizationpolymers are usually more flammable than polymers that crosslink or remove pendant groups. Cross-linking leads to precursors of char and as a result, to lower