1、塑料注塑成型加工塑料注塑成型加工向 明四川大学高分子研究所高分子材料工程国家重点实验室良好的注塑件质量获得的条件良好的注塑件质量获得的条件适合的注塑设备适宜的螺杆结构良好的材料预处理工艺合适的注塑工艺条件合理的模具结构塑料注塑基础塑料注塑基础注塑加工涉及的过程1、塑料胶粒的软化和塑化（螺杆塑化过程）螺杆结构的设计必须保证得到均匀一致的熔体2、塑料熔体计量 螺杆转速，背压3、塑料熔体向锁闭型腔注射 锁模力比型腔压力高20%，熔体以均衡的方式充填模具型腔，以避免内应力的产生 多级注塑、充模流动行为、型腔压力分布、熔体PVT性质4、冷却熔体凝固并保持模具型腔形状 均匀的模具表面温度，避免制件翘曲、保
2、证尺寸精度5、制件顶出塑化过程塑化过程最大计量行程最大计量行程屏障螺杆屏障螺杆关于塑料的特征关于塑料的特征分子量熔体指数PVT性质剪切稀化行为热稳定性收缩行为最大流动比吸湿性PVT性质性质材料的收缩特性材料的收缩特性温度引起的体积变化 结晶高分子 29%无定型高分子 8%压力引起的体积变化 10-15%Poly-merDensityRoomTemp.Process temp.degree cDensity process temp%age injection utilisa-tion capacityPermissible residence time-min.Max-flow ratio f
3、or 1mm wall thicknessScrew cushionmmShrinkage%Output ratio related toPsScrew rpm related toPsABS1.05220-2600.9640-80 100-1404-60.4-0.70.830.83CA1.29170-2501.1050-805-830030.4-0.7NANAPOM1.42192-2151.1630-8015100-2302-62NANAPMMA1.18220-2601.0935-804-8100-1302-60.4-0.80.940.74PPO1.06250-290NA30-808100-
4、1403-40.4-0.7NANAPA6/61.14220-2800.9540-805100-2302-4NA0.580.50PC1.22280-3101.0850-802-360-10040.7-0.80.670.57PES1.37330-400NANANA60-1204-50.60.950.83PBT1.31220-270NA40-803-4125-1854NANANAPPS1.5-2.1300-360NA50-802-4120-1504-60.2NANAPETP1.38260-3001.250-802-450-9041.3-1.50.80.74PS1.05220-2700.9525-90
5、2-4150-20040.451.001.00HDPE0.95220-2800.7410-85 1702-61.5-20.730.94LDPE0.92180-2800.7410-95 2002-6NA0.821.05PP0.91250-2750.7310-85 17041.2-2.20.630.86RPVC1.3-1.6170-190NA25-802060 0.5-0.2NANASPVC1.1-1.14180-200NA20-801518041.2NANASAN1.08240-2700.9940-805-6140-18040.50.961.12TPU1.20180-225NA40-803050
6、31-1.15NANA剪切变稀行为剪切变稀行为螺杆压缩区的剪切稀化螺杆压缩区的剪切稀化喷嘴的剪切稀化喷嘴的剪切稀化热稳定性热稳定性 K x 最大射胶体停留时间=-x 成型周期 型腔体积注塑过程注塑过程充模过程 85-98%注塑行程切换过程压实过程冷却过程注塑过程中的收缩行为注塑过程中的收缩行为加工过程对收缩的影响加工过程对收缩的影响不同材料的收缩率不同材料的收缩率MATERIALS%SHRINKAGEMATERIALS%SHRINKAGENylon 61-1.5Polycarbonate0.8Nylon 6-GR0.5Acetal2Nylon 6/61-2PVC-Rigid0.5-0.7Nyl
7、on 6/6-GR0.5PVC-Soft1-3LDPE1.5-3ABS0.4-0.6HDPE2-3PP1.2-2Polystyrene0.5-0.7Cellulose acetate0.5Styrene-acrylonitrile0.4-0.6Cellulose acetate.butyrate0.5Acrylic0.3-0.6Cellulose propionate0.5 收缩收缩收缩与翘曲收缩与翘曲收缩与结晶收缩与结晶收缩与加工过程收缩与加工过程收缩与取向收缩与取向收缩与冷却收缩与冷却充模与冷却充模与冷却均衡流动均衡流动调整均衡性调整均衡性调整均衡性调整均衡性与模具和机台相关的注塑缺陷与模
8、具和机台相关的注塑缺陷缩痕 壁厚设计不均匀 可通过注塑压力、保压压力、注塑速度调整尺寸变化 冷却不均匀，调整保压压力、时间、强化冷却均匀性翘曲熔接缝降解重量变化POSITIONSPEEDPRESSUREFILLING PHASEAlso known as Speed phase.Select end of 1st step and start of 2nd step.Set SPEED 1Try to set high.Only one pressure setting is required during FILLING PHASE.Pressure Setting should be mo
9、re than actual filling pressure.as relief valve should not be actuated.If it is actuated,then speed control will be lost.Filling pressure depends on resistance to move the melt.It depends on flow ratio and viscosity of melt.Also known as Speed phase.There may be no.of steps available on machine.Sele
10、ct end of 2nd step and start of 3rd stepSet SPEED 2Lower speed for crossing narrow passage/gateSteps are position controlled.Select end of 3rd step and start of SWITCH OVER POINT.This point is at around 80-95%of the injection stroke.Set SPEED 3Reduce to lower sink mark/increase to shift weld line.PR
11、ESSURE PHASE-Holding phase.There may be no.of steps available on machine.Timer controls the Holding pressure steps if available on machine.Holding pressure time for step 1 is set on a timer,Set SPEED low value say up to 35%not more.This can be one step of speed for different Holding steps.Speed set
12、is low,as there is less or no space to move the melt.Holding pressure 1 set just enough to fill cavity without overpacking.Steps are timers controlled.Holding pressure time for step 2 is set on a timer,Holding pressure 2 set just enough to fill cavity without overpacking.Holding pressure time for st
13、ep 3 is set on a timer,Holding pressure 3 set just enough to fill cavity without overpacking.均衡热交换均衡热交换均衡凝固均衡凝固熔接缝熔接缝改变熔接缝位置改变熔接缝位置成型周期成型周期The predominantly material causes involved in failure were:The predominating process faults were:Environmental Stress Cracking,Excessive moulded-in stresses,Cycl
14、ic Fatigue,Voiding,Notch Sensitivity,Poor weld lines,Chemical Attack and;Stress Cracking,Adverse Orientation,UV Degradation,Material contamination,Thermal Degradation,Longer Residence time in the machine,Creep,Wrong material selection or poor part design,Buckling,Wrong material selection or poor par
15、t design工程塑料的加工缺陷及解决方工程塑料的加工缺陷及解决方法法热塑性工程塑料的加工热塑性工程塑料的加工材料加工在材料应用中处于举足轻重的地位 特定用途 材料选择 依据材料性能的准确测试 但在实际的过程中,加工过程并不能完整的将材料性能表达到具体的制件上 特定用途 材料选择 加工条件 如果选择的工程塑料的加工窗口过窄,塑料会在加工过程中发生力学、物理、化学的变化通常,加工窗口越窄,制件的不合格率越高一般在塑料加工过程中，制件的质量控制主要通过将其与已知性能的好样品进行比较热塑性工程塑料的加工缺陷的热塑性工程塑料的加工缺陷的发现发现目测 表面、外观质量力学性能测试 材料性能和加工条件对制
16、件使用性能的影 响重量比较尺寸稳定性观察内应力的表征加工缺陷加工缺陷表观缺陷 外观、尺寸、重量变化、制件发脆等隐性缺陷 导致材料过早失效热塑性工程塑料加工的表观缺热塑性工程塑料加工的表观缺陷陷黑点原因 down time too long barrel switched off over a long period of time poor purging of barrel dirty plasticizing unit inadequate nozzledead edges in gate/runner system granule impurities degradation by ot
17、her resins pick-up of degraded material from cylinder wall during cooling 气泡 injection pressure too low inadequate functioning of back flow valve suck-back too long plasticizing too fast air trap in the hopper feed improper feed volatiles and trapped gas mould temperature too low thin to thick trans
18、ition melt overheating1.control holding/injection pressure 2.increase back pressure 3.increase mould temperature 4.check back flow valve 5.allow for adequate venting 6.enlarge gate 7.shorten land length 流痕injection speed too slow or too fast injection pressure too low hold pressure too long inadequa
19、te mould cooling mould too hot around gate mould too cold gate too small wrong gate location gate land length too long wrong hot runner system melt temperature too low 1.adapt injection speed 2.add a large cold slug area 3.add cold wells at the end of runner systems 4.control nozzle heat better:if n
20、ecessary add beryllium copper tip(not recommended for FR resins)5.shorten or eliminate standard sprue bushing:use a hot sprue bushing 6.clean flow must exist from the cylinder,adaptor,nozzle and tip:avoid and eliminate any dead pockets or sections 胶烧problems with back flow valve injection speed too
21、fast back pressure too high inadequate venting:entrapped air frictional burning check sprue diameter melt too hot or too cold:may create shear 起层injection speed too high melt too hot poorly melted Incompatible colour dyes cross contamination with other polymers too much use of recycled material 变色 飞
22、边射流纹路 缩痕缺料银丝热塑性工程塑料加工的隐性缺热塑性工程塑料加工的隐性缺陷陷收缩率、翘曲后收缩率大空洞ZIPPER不熔颗粒及熔体不均匀性熔接痕强度低模温设定不正确引起的性能劣化其他加工条件引起的性能劣化飞边引起的缺口效应残留内应力 提高生产效率-减少成型周期-低模温 -高内应力-应力开裂检查内应力检查内应力ABS 冰醋酸，甲醇SAN 甲苯/异丙醇（1/5）PA 6，PA 66 氯化锌饱和水溶液，50POM 硫酸，50PC 甲苯/异丙醇（1/3）结语结语 在正确选用材料的前提下，热塑性工程塑料加工中的缺陷是造成制件失效的主要原因。可以通过优化加工条件、模具设计的改善、以及材料的流动特征及冷却凝固行为的控制，来避免加工过程产生的缺陷减少制件的失效破坏。谢 谢！
