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我國是世界上最大的ABS樹脂消費國，自20世紀(jì)80年代以來，我國的ABS樹脂消費量迅猛增長，近年來每年消費量已超過120萬t。據(jù)業(yè)內(nèi)專家估計，今后ABS制品的應(yīng)用領(lǐng)域?qū)⑦M(jìn)一步拓寬，其市場需求潛力巨大。
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ABS塑料擠出成型工藝 ????
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原材料干燥 ?????
ABS樹脂有一定的吸濕性，含水量一般在0.3%～0.8%范圍內(nèi)，加工前需對其進(jìn)行干燥處理，一般將ABS樹脂在80～85℃恒溫干燥4h左右即可，干燥后的水分含量應(yīng)小于0.2%。若干燥不足，則制品表面會出現(xiàn)癍痕、水紋或起泡現(xiàn)象。若干燥時間過長或干燥溫度偏高，會造成樹脂結(jié)塊、制品發(fā)黃。 ????
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設(shè)備 ?????
采用單螺桿擠出機(jī)擠出，螺桿的長徑比（LID）為18～22，壓縮比為2.5～3；擠出機(jī)料斗可配置干燥預(yù)熱裝置，機(jī)筒可采取排氣式結(jié)構(gòu)。 ???
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擠出機(jī)機(jī)筒與機(jī)頭溫度 ?????
在滿足擠出機(jī)正常擠出條件下，機(jī)筒溫度160～180℃，機(jī)頭溫度175～185℃。溫度偏高時，熔體流動性好，但擠出波動太大且不穩(wěn)定，難以保證擠出制品質(zhì)量；溫度過高，還易造成原料降解。連接器的溫度一般比螺桿頭部均化段的溫度低5℃，或者同溫。該溫度對原料的流動性起決定作用，其溫度偏高，原料易降解變色，擠出波動大；溫度偏低，易堵塞排氣口，使真空度下降，擠出型材表面出現(xiàn)氣泡。 ????
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冷卻條件的控制 ?????
從口模擠出的型坯需采用及時、合理的冷卻方式和恰當(dāng)?shù)睦鋮s水溫進(jìn)行冷卻定型，方能得到理想的制品。ABS型材擠出過程中冷卻水溫在14～18℃較為理想，有效水壓應(yīng)大于0.2MPa。在生產(chǎn)過程中，如果冷卻水水溫過高或水壓偏低、水流量偏小，使型材在出定型模后溫度偏高甚至發(fā)生后變形，應(yīng)適當(dāng)降低擠出速度，以確保冷卻時間；如果冷卻水溫過低，會形成驟冷，容易使型材內(nèi)部殘留有內(nèi)應(yīng)力，在自然存放過程中產(chǎn)生后變形，或者引起牽引阻力過大甚至顫車。
China is the largest consumer of ABS resin in the world. Since the 1980s, the consumption of ABS resin in China has been increasing rapidly. In recent years, the consumption of ABS has exceeded 1.2 million tons.Industry experts estimate that the application of ABS products will be further expanded in the future, and its market demand potential is huge.
ABS resin extrusion molding process
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Drying of raw materials
?????ABS resin has certain moisture absorption, water content is generally within the range of 0.3% ~ 0.8%.Before processing, it needs to be dried, and the ABS resin is generally kept in a temperature of 80 ~ 85 to about 4h.After drying, the moisture content should be less than 0.2%.If the drying is not enough, the surface of the product will have a ripple, water pattern or bubbling phenomenon.If the drying time is too long or the drying temperature is too high, it will cause the resin caking and the product yellowing.
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Equipment
Using single screw extruder, the length diameter ratio (LID) of screw is 18 ~ 22, and the compression ratio is 2.5 ~ 3.Extruder hopper can be equipped with dry preheating device, and the cylinder can adopt exhaust structure.
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Temperature of the?barrel and head?of extruder
???Normal extrusion temperature: the temperature of the cylinder is 160 ~ 180, and the head temperature is 175 ~ 185.When the temperature is high, the melt flow is good, but the extrusion fluctuation is too large and unstable to ensure the quality of extrusion products.Connector temperature generally lower than the screw head of homogenization temperature of 5 ℃.
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Control of cooling conditions
???In order to get the ideal product, the mold extruded form must be cooled by a timely, reasonable cooling method and proper cooling water temperature.The cooling water temperature in ABS extrusion process is ideal in 14 ~ 18 degrees, and the effective water pressure should be greater than 0.2mpa.
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