Tuesday, August 1, 2023

‘Curious’ worker ignites foam, causes huge warehouse fire in China “好奇”工人点燃泡沫,引发中国仓库大火

‘Curious’ worker ignites foam, causes huge warehouse fire in China

South China Morning Post on Youtube has the story.

A warehouse storing EPE foam burst into flames after a worker ignited highly flammable foam rolls with a lighter in southern China’s Guangdong province.

Expanded polyethylene is an interesting product.

(Polyethylene foam) Expanded polyethylene (aka EPE foam) refers to foams made from polyethylene. Typically it is made from expanded pellets ('EPE bead') made with use of a blowing agent, followed by expansion into a mold in a steam chest - the process is similar to that used to make expanded polystyrene foam.

EPE foams are low density, semi-rigid, closed cell foam that are generally somewhere in stiffness/compliance between Expanded polystyrene and Polyurethane. Production of EPE foams is similar to that of expanded polystyrene, but starting with PE beads. Typical densities are 29 to 120 kg/m3 (49 to 202 lb/cu yd) with the lower figure being common. Densities as low as 14 kg/m3 (24 lb/cu yd) can be produced.

Base polymer for EPE foams range from Low-density polyethylene (LDPE) to High-density polyethylene (HDPE).

Expanded polyethylene copolymers (EPC) are also known - such as 50:50 (weight) materials with polystyrene. Though other properties are intermediate between the two bases, toughness for the copolymer exceeds either, with good tensile and puncture resistance. It is particularly applicable for re-usable products.

EPE foams were first manufactured in the 1970s.

Production of the PE beads is usually by extrusion, followed by chopping, producing a 'pellet'. Autoclave expansion is the most common route the bead foam. Butane or pentane is often used as a blowing agent (before 1992 CFCs may have been used). Depending on the specific process uses the beads may be cross-linked either by electron beam irradiation (see Electron beam processing), or by the addition of a chemical agent such as Dicumyl peroxide.

How easily does butane ignite? The Effects of Butane Exposure are interesting. Butane is highly flammable and can ignite easily through static electricity, open flames, or other ignition sources. As a combustible gas, butane concentrations anywhere between 1.6% and 8.4% can provide an explosive mixture with air.

An alternate route (JSP Process) to the beads uses carbon dioxide as a blowing agent which is impregnated into the pellets in an autoclave at a temperature close to the plastic's crystalline melting point. The pellets are foamed by "flashing" into the (lower pressure) atmosphere to expand.

Finally molding is done by steam chest compression molding; usually the low pressure variant of the process is used, though the high pressure variant may be used for HDPE based EPE foams.



YouTube 上的《南华早报》有这个故事。

在中国南部广东省,一名工人用打火机点燃高度易燃的泡沫卷,一间存放 EPE 泡沫的仓库突然起火。


(聚乙烯泡沫)发泡聚乙烯(又名EPE泡沫)是指由聚乙烯制成的泡沫。 通常,它是由使用发泡剂制成的膨胀颗粒(“EPE 珠子”)制成,然后在蒸汽箱中膨胀到模具中 - 该过程类似于制造膨胀聚苯乙烯泡沫的过程。

EPE 泡沫是低密度、半刚性、闭孔泡沫,其硬度/柔顺性通常介于发泡聚苯乙烯和聚氨酯之间。 EPE 泡沫的生产与发泡聚苯乙烯的生产类似,但从 PE 珠开始。 典型密度为 29 至 120 kg/m3(49 至 202 lb/cu yd),其中较低的数字较为常见。 可以生产密度低至 14 kg/m3 (24 lb/cu yd) 的产品。

EPE 泡沫的基础聚合物范围从低密度聚乙烯 (LDPE) 到高密度聚乙烯 (HDPE)。

膨胀聚乙烯共聚物(EPC)也是已知的——例如与聚苯乙烯的50:50(重量)材料。 尽管其他性能介于这两种基材之间,但该共聚物的韧性超过了其中任何一种,并且具有良好的拉伸和抗穿刺性能。 它特别适用于可重复使用的产品。

EPE 泡沫首次生产于 20 世纪 70 年代。

PE 珠粒的生产通常是通过挤出,然后切碎,形成“颗粒”。 高压釜膨胀是珠粒泡沫最常见的途径。 丁烷或戊烷通常用作发泡剂(1992 年之前可能已使用 CFC)。 根据具体的工艺用途,珠子可以通过电子束照射(参见电子束处理)或通过添加化学试剂(例如过氧化二异丙苯)进行交联。

丁烷有多容易点燃? 接触丁烷的影响很有趣。 丁烷高度易燃,很容易通过静电、明火或其他火源点燃。 作为一种可燃气体,丁烷浓度在 1.6% 到 8.4% 之间时,可与空气形成爆炸性混合物。

生产珠粒的另一种途径(JSP 工艺)使用二氧化碳作为发泡剂,在接近塑料晶体熔点的温度下将二氧化碳浸渍到高压釜中的颗粒中。 颗粒通过“闪蒸”到(低压)大气中膨胀而发泡。

最后采用蒸汽室压缩成型进行成型; 尽管高压变体可用于基于 HDPE 的 EPE 泡沫,但通常使用该工艺的低压变体。

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