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泡沫聚乙烯配料中含有在特定温度下能分解和发生大量气体的化学发泡剂。气体使塑料膨胀为微孔结构。例如牌号为DFD—4960的泡沫聚乙烯含有的发泡剂在一大气压下足够使塑料的体积增加一倍,见图1。它降低绝缘的密度为实芯绝缘的一半。化学泡沫塑料成功的挤出发生在高压力下的挤塑机内发泡剂被分解而没有形成相当大的气泡,即没有膨胀塑料的时候。这性能允许发泡剂在机身和机头内分解到预定的程度,并不因切向流动而有微孔断裂的危险和气体损失。因线从模子移动到水槽时不存在切力,在发泡
Foam Polyethylene formulations contain chemical blowing agents that decompose and generate large quantities of gas at specific temperatures. Gas expands the plastic into a microporous structure. For example, a foamed polyethylene, grade DFD-4960, contains a blowing agent sufficient to double the volume of plastic at one atmosphere, as shown in Figure 1. It reduces the density of insulation to half that of solid insulation. Successful Extrusion of Chemical Foams The foaming agent that occurs in a high pressure extruder is decomposed without the formation of considerable bubbles, ie without the expansive plastic. This property allows the blowing agent to disintegrate to a predetermined extent within the fuselage and nose without the risk of micro-hole rupture and gas loss due to tangential flow. There is no shear when the wire is moved from the mold to the sink, foaming