Background
Plastic cover plates injection molded with styrene-acrylonitrile (AS) from various production lots of IRPC Public Company Limited showed silver streaks problem in various locations on the workpiece probably caused by moisture, residual monomers upon the polymerization reaction, or additives mixed into the resin. Therefore, it is necessary to study systematically to determine the exact cause. This will lead to direct and effective solutions to the problem.
Goal
To analyze the root cause of silver streaks and propose solutions to the problem precisely.
What does the research team do?
1. Analyze the thermal decomposition rate of polymers by Thermogravimetric Analysis, TGA
2. Apply knowledge of injection mold design together with injection molding simulation.
3. Trial to optimize molding of cover plate
Research results
Silver streaks in plastic cover plate is of air streak type. This is caused by improper design of the workpiece and the mold has no air vents causing air to be trapped. The problem will be more severe if the workpiece is injected with a more thermally unstable grade AS.
Research status
Completed
Outlook
The company uses the knowledge gained as a guideline for production planning and shutdown in order to clean the AS resin synthesis line to have a production cycle that is not too long, before there is a risk of accumulation of various substances within the synthesis line, especially AS grades containing substances that are readily thermally decomposed. This is to reduce the likelihood that the AS will undergo thermal degradation during injection molding.
Moreover, the company will transfer the knowledge of mold design that is guided by our research team to the customer. This will help avoid the problem of trapped air in the mold which is one of the main reasons in this case why the injection molded part has silver streaks.
Research team
Dr.-Ing. Patcharee Larpsuriyakul, Jareenuch Rojsatean, Dumrong Thanomjitr and Natcha Prakymoramas
Contact
Dr.-Ing. Patcharee Larpsuriyakul
Material Processing and Manufacturing Automation Research Group
Tel: 02 564 6500 ext. 4449
Email: Patcharl@mtec.or.th