A novel method for predicting degrees of crystallinity in injection molding during packing stage

Abstract

Being able to predict products’ degrees of crystallinity and thereby optimize their crystallization processes is of great significance for producing high-quality polymeric products in injection molding. However, it is rather difficult to theoretically establish the relationship between the crystallization results and processing conditions (high cooling rates and pressures, strong and complex flow fields). Injection molding simulation software can simulate polymers’ density results during packing stage, and these predicted density results can be used to calculate polymers’ crystallinity results. Based on this idea, a novel method was proposed to predict the degrees of crystallinity for polymers during packing stage. In this method, pressure and temperature results are first simulated by an injection molding simulation software, and then the density results are calculated based on a pressure–volume–temperature model. Next, the crystallinity results are solved according to the densities of the fully crystalline part and the purely amorphous part. Finally, two case studies are conducted to verify the proposed crystallinity prediction method. Moreover, the effects of packing parameters (mold temperature, packing pressure, and packing time) on polymers’ crystallization behaviors are investigated. The experimental results show that the proposed method is correct and effective.

Quantification of the Young's modulus for polypropylene: Influence of initial crystallinity and service temperature

“…However, crystallinity should not be omitted in the consideration of mechanical properties. Considering the limited crystallization range of polypropylene injection molded parts, the model established in this paper has great reliability.…”

Design and Research of Skin Injection Molded TPE Materials Based on Genetic Algorithm

“…From Zhao's work, it can be found that low mold temperature was beneficial for the improvement of crystallinity degree but negative for the uniformity of crystallinity. erefore, the mold temperature was chosen as 40°C in the current study [18]. e melt flow rate instrument was MFI-1211 bought from Chengde Jinjian Testing Instrument Co., Ltd. e mechanical test machine was CMT6104 from Metis Industrial Systems (China) Co., Ltd. e electric cross gravimeter was 430P-I from Erichsen Company, Germany.…”

Nondestructive measurement of layer thickness in water‐assisted coinjection‐molded product by ultrasonic technology

“…To observe the interface of the WACIM part, the specimens were placed in liquid nitrogen for 10 min and experienced brittle fracture. 29 A scanning electron microscope (SEM; fully digital SU8010 instrument, Hitachi, Tokyo, Japan) was employed to observe the interface after sputter-coating the samples with gold for 70 s. The operating parameters of SEM are as follows: the acceleration voltage is 3 kV, the operating distance is 8.9 mm, and the magnification is 40.…”