1、 Material characteristics

PC+ABS
It is a thermoplastic plastic made of two material alloys, PC and ABS, which combines the excellent properties of both materials. Can be widely used in automotive accessories, lampshades, handles, and other components; Household and commercial appliances such as computers and peripheral devices, such as mobile phones, can replace PCs for thin-walled, long process products. Camera components, instrument panel, fan cover, safety helmet casing, rotating cover, radiator grille, computer and optical instrument casing, hair dryer, coffee pot, etc.

PC/ABS alloy material
It has the following characteristics:
1. Good overall performance, high impact strength, chemical stability, and good electrical performance
2. It has good fusion performance with 372 organic glass and is made into dual color plastic parts, which can be surface chrome plated and painted
3. It has high impact resistance, high heat resistance, flame retardancy, reinforcement, transparency, and other levels.
4. The fluidity is slightly worse than HIPS, better than PMMA, PC, etc., and has good flexibility.
5. Excellent balance of mechanical performance
6. High impact strength at low temperatures
7. Indoor UV stability
8. Higher thermal deformation temperature (80-125 ℃)

2、 Common injection molding issues
We have learned about the characteristics of PC+ABS, so let's take a look at common problems during the injection molding process.

1. Flow mark problem
Flow marks are generated during injection of materials due to poor fluidity. Unlike silver marks, flow marks are not caused by moisture or material decomposition, and their appearance is also different.

Solution
It can be avoided by increasing the material temperature to improve flowability, and appropriately increasing mold problems to increase material flowability within the mold and reducing injection speed can also solve the problem.

2. Silver wire issue
Poor silver wire is the most common problem in PC/ABS materials. Silver wire, also known as silver streaks, water splashes, and material splashes, is a phenomenon of silver white filamentous stripes appearing on the surface of products along the flow direction.
The main reason is due to the interference of gases, which are mainly divided into three components:
Air: The air involved in the melting and injection stages;
Moisture: The moisture contained in the material itself;
Cracking gas: Gas produced by high-temperature hydrolysis/thermal decomposition.

Solution
Firstly, check whether the material is sufficiently dry. After confirming that the material is sufficiently dry, adjust the injection molding process to improve the silver wire defects. At the same time, poor injection molding of silver wire is also related to mold exhaust.

3. Shrinkage and dents issues
Shrinkage is caused by insufficient filling of materials in the mold cavity.

Solution
: Increase the mold temperature and material temperature appropriately to improve material fluidity, extend the injection pressure holding time, increase injection pressure, increase injection speed to improve mold filling ability, or increase the size of the gate and heat the gate runner to reduce and eliminate product shrinkage;

Dents are caused by improper material temperature and improper product design. When the material temperature is too low, not only will shrinkage occur, but also the problem of dents will occur. If the material temperature is too high and the mold temperature is too high, it will cause excessive shrinkage of the molten material during cooling, resulting in dents.

Solution
Adopting appropriate processing issues, improving injection speed and measures.

4. Warpage deformation problem
The warping deformation of injection molded parts is caused by the unreasonable design of the parts, improper gate position, and unreasonable injection molding conditions, resulting in internal stress, uneven or excessive shrinkage. The mold temperature is too high or uneven, causing difficulty in demolding the parts due to the mucous membrane, or uneven cooling, which can also cause warping deformation;

Solution
In terms of processing technology, extend the injection molding cycle, reduce the injection temperature, adjust the injection pressure and speed appropriately, while slowing down the ejection speed, increasing the ejection area, and maintaining a balanced ejection force;
In terms of product design, increasing wall thickness, adding reinforcing ribs, and reinforcing the corners can reduce warping deformation;
5. Speckle problem

Usually, it is caused by the expansion of molten material into the mold cavity during high-speed injection, resulting in "melt fracture".

Solution:
In terms of molding process, measures such as increasing material temperature, increasing nozzle temperature, and slowing down injection speed are taken to reduce the occurrence of spots;
In terms of molds: increase mold temperature, add overflow slots, increase gate size, and modify gate shape.

6. Pitting issues
Solution:
Poor dispersibility, add dispersants or oil, increase temperature, and add back pressure.
Pay attention to any mold issues. Try using other materials.
Is the baking temperature and time sufficient.
Mold temperature adjustment.

7. Product peeling problem
The peeling problem of plastic products is closely related to the rupture of fluids caused by high shear stress. Under low shear stress or rate, small disturbances caused by various factors are suppressed by the melt; At high shear stresses or rates, disturbances in the fluid are difficult to suppress and develop into unstable flows; When a critical shear force is reached, it will cause the fluid to rupture.

Solution:
In terms of materials: The PC and ABS components are partially compatible, so it is necessary to add appropriate compatibilizers during the modification process to improve their compatibility. Of course, the peeling problem caused by mixing materials is the first step we need to eliminate;

In terms of molds: The principles of mold design should follow the direction of minimizing shear as much as possible. Generally speaking, products with densely textured surfaces are more prone to peeling (caused by the friction and shear between the melt in the cavity and the inner wall of the cavity during high-speed filling); At the same time, in the design of the gate, if the gate size is too small, it will cause excessive shear of the melt when passing through the gate, which will then lead to peeling on the surface of the product;

Injection molding process: The main direction is to avoid excessive shearing. When it is difficult to fill the product, high-speed and high-pressure methods can be used to improve it. Therefore, in the actual injection molding process, increasing the injection temperature/mold temperature, and improving the material fluidity can also be considered to reduce the flow resistance during the actual filling process, thereby avoiding excessive shear caused by high-speed and high-pressure.

If you encounter any other problems during the injection molding process, please feel free to consult us for solutions!