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low pressure PP foaming injection molding research
foam plastics tool has light, ratio strong/high degree high, 隔音, thermal insulation, price low and other advantages, therefore widely used in packaging, 运输, automotive, temperature, construction, and aerospace and other field/area. 自20世纪90 year 代以, foam plastics development separation speed, main/primary product types has polyurethane ester （PUR） soft, hard foam plastics, polystyrene (PS) （PS） and polyethylene (PE) (PE) foam plastics large type.
this foam plastics in, PUR foaming material in foaming process in generate for has 害 异氰 acid ester, and method recycling utilizing; PE foam plastics rigid property and most high use temperature degree relatively low, easy degradation; 而PS foaming material in molding process in use fluorine chlorine material, bad large gas oxygen 层, difficult degradation and recycling, easy formed “ white 污染”, already by prohibited use. is, 人们开始积极寻找 can foaming PS fluorine, light amount ring 境适应 property packaging materials, foaming polypropylene (PP) (PP), used for food, product and electronics product and other packaging [1].
foaming PP因 its excellent force property can, biodegradable recycling property, environmental protection property and products good heat stabilized property and high temperature dimensional stability, formed is foam plastics industry in research hot 点. currently 一 发达国家 large force development foaming PP, as is substitute/replace foaming PS green packaging materials.
PP foaming material usually using/adopting extrusion molding [2], pressure molding [3] and other methods made 备, using/adopting injection molding 却鲜见报道. using/adopting mold opening method for PP进行 injection molding foaming molding [4], research foaming agent, crosslinked agent and filler use amount for PP low foaming material property can effect/influence.
万 can material experiment/testing machine, Instron-1185, USA 英斯特朗 company;
Izod experiment/testing machine, XCJ-500, experiment/testing machine 厂;
electrical plastics hardness 计, XHRD-150, 山东莱州市 experiment/testing machine 总厂;
维卡 soft temperature degree 测定仪, XWY-300B, 济南天辰 machine has company;
扫描 electronics micro 镜(SEM), AIS2100, Korea MIRERO company.
impact property can 按GB/T1843—1996 testing;
邵尔 hardness 按GB/T531—1999 testing;
table/sheet density 按GB/T6343—1995 testing;
heat deflection temperature (HDT) 按GB/T1634—1979 testing, negative 荷0.46MPa;
use SEM观察 foaming products 脆断面 泡孔 structure.
由图1 can 见: foaming PP Sample 脆断断面没 has 泡孔, foaming PP Sample 脆断断面 in in a large amount of 泡孔, 且周边 is structure. this can in material heat resistant property, force property can and hardness and other maintain indicators front lower, make material density obvious decline, is can reduce mono products PP resin use amount, from reduce products cost.
1, low pressure foaming injection molding
PP structure foaming injection molding generally using/adopting below/following types molding methods: low pressure foaming injection molding; high pressure foaming injection molding; pressure foaming injection molding; di separation foaming injection molding.
structure foaming injection molding and injection molding difference. nozzle using/adopting 闭锁式 nozzle, generally using/adopting method. types methods can production large type thick products, its products surface 致密, can printing or coating, is surface coarse degree relatively 差.
曹民 dry use Japan Sumitomo company SSF100/150/200 type low foaming injection mechanism structure foaming PP sheet/plate 材, analysis process parameters for products property can effect/influence, most process parameters is: injection time 5s, injection pressure 80MPa, material temperature degree 240℃, mold temperature degree 70℃, holding pressure time 10s, cooling time 8s.
Peter Zipper and other use low pressure injection molding method in different melt temperature degree lower injection molding PP圆柱状 sample, use small 角X射线衍射 method for sample research, table/sheet 明: formed cycle and sample 圆柱 直径 and melt temperature degree has 关, melt temperature degree high, products dimensions large, formed cycle long.
Sporrer and other development types used for low pressure foaming injection machine mold, by is “排 gas mold ”. its inner surface cover/cap carbon 钢并开 一 槽, but also and other as more easy control. 实验证明: in combined injection parameters conditions lower, use this type of mold injection molding structure foaming products quality relatively good, surface relatively light slip.
2, high pressure foaming injection molding
high pressure foaming injection molding mold cavity pressure is 7～15MPa, and injection machine versus ratio, increase clamping holding pressure plant/unit, its products surface 平整, 清晰, can 体现出 mold cavity inner fine small 形状, clamping generate 折痕, strip/profile and other, therefore for mold manufacturing degree requirements high, mold use high, 二次锁模 holding pressure requirements high.
张 pure and other use mold opening method formed made PP structure foaming products, its products tool has relatively uniform distribution, 泡孔直径都 in 20～30μｍ, density large decline 15％, and foaming PP force property can versus ratio, tensile strength decline 24.8％, notched impact strength improve/increase 125％, flexural strength improve/increase 19.6％.
Norbert Muller and other using/adopting mold opening method, 以PP/ glass fiber blending material is raw materials high pressure foaming injection molding, its products density decrease small 10%~15%, quality decrease light 30%~40%. if in mold upper use 切口代替 separation type 面, rate can to 100%, density decrease/reduce 50%（ density is 0.2～0.4 g/cm3）. mold type thick degree is 2～4mm时 molding PP structure foaming products, foaming most 佳, flexural strength relatively high.
3, pressure foaming injection molding
反 pressure foaming injection molding is in injection front use high pressure gas 体（如空 gas or inert property gas 体） will mold mold cavity 充满, injection retardant plastics foaming 膨胀以 to table/sheet 层, using/adopting method, injection 一定 熔 material rear gas 体排出 make plastics 膨胀而充满整 mold cavity. injection molding products surface coarse degree relatively good, table/sheet 层组织 comparison uniform 致密, is need increase sleeve/set gas pressure plant/unit and can type mold, gas pressure relatively high （20MPa）, investment relatively large, mold 密封也 relatively difficult.
Peter Zipper and other use 广角X射线衍射 method separation amount low pressure foaming injection molding and pressure foaming injection molding PP sample, table/sheet 明, pressure foaming injection molding sample surface quality relatively good.
4, di separation foaming injection molding
di separation foaming injection molding is types high pressure foaming injection molding methods, it using/adopting injection machine, this type of injection machine has sleeve/set injection plant/unit: sleeve/set injection molding products table/sheet 层, sleeve/set injection molding products 芯部. different formulation raw materials, separation through this injection molding plant/unit 按一定顺序先 rear to sleeve/set mold mold cavity, from to tool has table/sheet and foaming light products. for/regarding large type products, can use filling material, waste material, and other, from large large reduce products production cost.
