表面剥离Delamination.doc

表面剥离Delamination何谓表面剥离（外观）What is delamination ? (appearance) 顾名思义，表面剥离是指成型品表层发生剥落的一种现象Delamination is a phenomenon that surface layer of mold piece is easily delamination , as its name suggests.。 注射成形品的构造通常分为表层（称为皮层）和内层（称为芯层）。这是因为熔化了的树脂通过喷流进入模腔内，在表层固化的同时，内部还在流动。这两层界面因某种原因而发生剥落的现象便是界面剥离Inside of mold piece generally has surface layer called skin layer and inner layer called core layer. These layers are generated from fountain flow which is common flowing style in injection molding. Delamination is generated when these two layers are separated by any reason.。图1. 120平板表面上出现的剥离Figure.1 Delamination on surface of 120*120 flat plate( Delamination size : about 2cm in this picture)（本例中的剥离程度约为2cm（2）表面剥离的生成原因Causes of surface delamination(2-1) 剪切力偏大High shear剥离是因树脂流动时的剪切力过大而产生的。剪切力变大的条件如下。特别是在厚度小且压力高的情况下容易产生这种成型不良Delamination is generated when shear in resin flowing is high. The conditions of high shear include the following. Delamination is a molding trouble frequently caused when wall thickness is thin and pressure is high.（1）机筒温度偏低（包括喷嘴）Too low cylinder temperature (including nozzle),（2）模具温度偏低Too low mold temperature,（3）浇口偏小（通过浇口时剪切力变大）Too small gate (Shear increases in gate passing through,（4）产品厚度偏薄Too thin wall thickness,（5）保压压力过高Too high holding pressure（6）注射速度过快 Too fast injection speed.此外还应注意流动距离、充填时间是否过长。如果充填时间长，则浇口附近的固化层和流动层的温差就会增大，从而容易产生剥离Besides, it may be caused by too long flow distance and too much time for filling. Too much time for filling increases the temperature difference between the solidified layer and the flowing layer to cause delamination.。图2. 剪切力 偏大时容易产生剥离Figure.2 High shear make delamination 2-2) 混入不同材料Foreign material contamination不同种类的树脂混入时也会产生剥离。塑料中具有相溶性（完全混合）的组合非常少，不同树脂可相溶的事例几乎没有。在成型过程这些树脂被拉长变薄，在成形品内部呈层状并分散开来，从而容易发生表层剥离。Surface delamination is generated when foreign resin is contaminated. In plastics compatible (complete mixing with each other) combinations are rare, and different resins are scarcely compatible. These resins are frequently extended thin in molding and dispersed in layers, leading to surface delamination as a result.与一般的等级相比，含油的滑动等级 和合金材料更容易产生表层剥离。Sliding grades as obtained by adding oil and alloy materials have a tendency to generate surface delamination compared with general materials.图3. 混入不同材料Figure.3 Foreign material2-3) 大量气体混入表层Too much gas mixed in surface layer含有大量气体时也会产生剥离。这是因为滞留在表层下面的气体会集聚成很薄的气体层。容易产生气体的条件如下：Surface delamination is generated when much gas is contained. Gas retained just under the surface layer gathers and forms a thin gas layer to cause surface delamination. The conditions of easy gas generation includes:（1）机筒温度过高（树脂已经分解）Too high cylinder temperature (resin decomposing),（2）干燥不足（含有大量水分）Too short drying (contains much moisture),（3）螺杆转速过快（空气卷入）Too high screw rotation speed (air catching),（4）背压过低（空气卷入）Too low back pressure (air catching)（5）保压压力过高Too high holding pressure,（6）注射速度过快Too fast injection speed,（7）使用了回收材料Using a recycled material.表面剥离的对策Countermeasures against surface delamination3-1) 降低剪切力有各种方法To reduce shear，但首先从容易改变的条件着手：There are many ways, but at first check the following conditions which are easy to change:提高机筒温度（包括喷嘴）To raise cylinder temperature (including nozzle),提高模具温度To raise mold temperature减慢注射速度To reduce injection speed,降低保压To reduce holding pressure此时，如果原因在于气体，则提高机筒温度有时反而会使情况恶化。就机筒温度而言，一般应遵守相应的树脂的推荐使用温度。At that time, if the cause is in gas generation, cylinder temperature raising may worsen the trouble. Basically, cylinder temperature should be within the recommended using temperature limits of the resin.其次应检查浇口和产品厚度。如果剥离发生在浇口附近，则原因可能是浇口过小。如果产品厚度过薄，剪切力偏高，则应考虑使用流动性好的等级。另外,就浇口而言，侧浇口比点浇口或隧道浇口更可取，可能的话 改变浇口设计也是一种方法。此外采用多点浇口也很有效果。Then, check the wall thickness of the gate and the product. If the position of delamination is near the gate, the cause is probably too small gate. If the wall thickness is too thin to cause high shear, use of a high flow grade should be considered. In such a case, the preferable gate system is side gate rather than pinpoint gate and tunnel gate. If possible, consider to change the gate system. The multipoint gate system is also effective.3-2) 抑制气体To suppress gas generation 为使成型品不含无用气体，应检查下列几点或实施相应的对策Check the following points or carry out the countermeasures so as not to contain unnecessary gas.：检查机筒温度是否在推荐的温度范围内To check if the cylinder temperature is within the recommended temperature limi