Plastic material problem analysis



What if the TPE product needs highly smooth surface, it must be dried before injecting.

Generally, it is hopper type drying 70~80°C/2h or tray drying 80~100°C/1h. Regarding tray drying, it should be noted that the thickness of the prepreg layer should not exceed 50mm. It is recommended to use tray drying. If there is foaming on the surface, or the strip is cut, or there is a cavity inside, or the surface of the product is scattered with silver, it can be judged that the TPE/TPR material have too much water.
There are possible problems with product during injection process:
First, the trace of activity
A streak phenomenon in which gloss is different on the surface.
Generally speaking, in the injection molding of resin:
1. The stripe is narrowly spaced.
2. Wider stripe shape appear on or under the surface
3. There are three types of narrow stripes on the surface.
Solutions : add pure monomer resin, enhance injection speed, raise mold temperature, enlarge injection
port, increase resin temperature and injection rate and molding temperature or decrease injection
speed. Both increase injection speed and the mold temperature are useful.
Second,the mold release is poor
The poor mold release property means that adhesive material easily give rise to this problem, but it
can be improved when add release agent on material or apply release agent on the mold which is before
injected .
Finished product lack of cooling , which also can lead to the same problem.Therefore ,it is necessary
to sufficiently cool the finished product. Besides, the mold design unreasonably, which will be the one
of the reasons, especially in the parts that are easy to stick injection port and feed path, etc.So it
is extremely significant to broaden injection gate and feed path.
Third, agingPhenomenon: the mechanical performance decrease obviously, and the shape of the product
is flawed.
Reason: Compared with inorganic materials and metal materials, the high heat resistance and UV-
resistance are poor, which cause aging of products. Most of the products occur poor appearance quality
due to mechanical performance decrease obviously
Solution : The main method is that control aging phenomenon by stabilizer of heat and weather
resistance or adding ultraviolet light absorber or light stabilizer.
Fourth, the color is uneven
It is simple to appear phenomenon of uneven color when masterbatch is coloring by utilizing
thermoplastic elastomer particles and dry blend.
As for solution, go forward screw back pressure and reinforce mixing when it is filling.

Written by Jerry-Ho
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