Case Study: Development of a Two-Color Overmolding Product Using TPE Material—A Perfect Combination with ABS+PC Materials
Time of issue:2026-01-19
I. Project Background
In this product development project, a two-color molding process will be employed. Our company’s TPE material (grade: TA75A-15) will be used to overmold ABS+PC materials, and the products will be manufactured using hot-runner injection molding. Given the high demands on both appearance and performance in real-world applications, it is essential during the trial production phase and machine adjustment process to ensure consistent product quality and prevent any defects from occurring.
II. Test Samples and Problem Identification
During the trial production, we used a 250T injection molding machine with a screw diameter of 32 mm. The injection molding temperature was set between 185°C and 195°C, and the initial hot runner temperature was 220°C. During the injection molding process, we experimented with various process parameters, such as high pressure at low speed and adjusting the injection time duration; however, the product consistently suffered from bubble defects. Subsequently, we reduced the hot runner temperature from 220°C to 190°C, yet the bubble problem persisted. At the same time, we observed that when the temperature was further lowered, the adhesion between the TPE material and the ABS+PC material deteriorated, resulting in poor bonding.
III. Problem Analysis
After analyzing the production process and materials, we preliminarily believe that the problem may lie in the hard plastic material (ABS+PC). Since the hard plastic tends to exhibit black streaks and the quality of sprue material cannot be reliably guaranteed, there is a possibility of other hard plastics being mixed in. Moreover, there are differences among materials from different batches. These variations affect the adhesion between the TPE soft plastic and the ABS+PC hard plastic, preventing gases from escaping smoothly and thus causing bulges and bubbles on the product surface.
IV. Implementation of the Solution
To address the bubble issue, we decided to switch to a harder plastic material. We used a standard new material—ABS+PC—mixed externally with color masterbatch and conducted a new trial run. After switching materials, the adhesion between the TPE soft rubber and the new ABS+PC hard plastic significantly improved. During the injection molding process, the soft rubber was able to better conform to the surface of the hard plastic, effectively preventing gas accumulation. As a result, the product surface no longer exhibits bubbles or blistering.
V. Results and Conclusions
By switching to a hard-rubber material, we successfully resolved the issue of air bubbles that had been occurring during injection molding of TPE two-color overmolding products (ABS+PC). This demonstrates that the quality and consistency of the hard-rubber material play a crucial role in determining the molding quality of two-color overmolding products. In subsequent product development and production processes, it is essential to strictly control the quality of the hard-rubber material and avoid using unstable runner materials or hard rubber containing impurities from other materials, thereby ensuring consistent product quality and improving production efficiency. At the same time, adjustments to process parameters must also be made rationally based on the specific characteristics of the materials, in order to achieve optimal molding results.
This case study on the development of a two-color overmolding product using TPE material (ABS+PC) has provided valuable experience for the production of similar products, highlighting the importance of material quality control and optimization of process parameters in two-color injection molding.
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