Using Gas Counter Pressure and Combined Technologies for Microcellular Injection Molding of Thermoplastic Polyurethane to Achieve High Foaming Qualities and Weight Reduction

Technical development and application of supercritical CO2 foaming technology in PCL foam production

Polycaprolactone (PCL) has the advantages of good biocompatibility, appropriate biodegradability, non-toxicity, flexibility, and processability. As a result, PCL-based foams can successfully work in bone tissue engineering, medical patches, drug delivery, reinforcing materials, and other applications. A promising technology for producing PCL foam products is supercritical CO2 (ScCO2) foaming technology, which avoids using organic solvents, is green, and has low foaming agent costs. However, due to the limitations of ScCO2 foaming technology, it is no longer possible to use this technology alone to meet current production requirements. Therefore, ScCO2 foaming technology must combine with other technologies to develop PCL foam products with better performance and matching requirements. This paper systematically reviews the technological development of ScCO2 foaming in producing PCL foams. The molding process of ScCO2 foaming and the conventional preparation process of PCL foam products are discussed comprehensively, including the preparation process, advantages, and disadvantages, challenges faced, etc. Six combined technologies for ScCO2 foaming in the production of PCL foams and the applications of PCL foams are presented. Finally, the future remaining research for producing PCL foams by ScCO2 foaming is analyzed.

Advanced Injection Molding Methods: Review

Injection molding is a method commonly used to manufacture plastic products. This technology makes it possible to obtain products of specially designed shape and size. In addition, the developed mold allows for repeated and repeatable production of selected plastic parts. Over the years, this technology grew in importance, and nowadays, products produced by injection molding are used in almost every field of industry. This paper is a review and provides information on recent research reports in the field of modern injection molding techniques. Selected plastics most commonly processed by this technique are discussed. Next, the chosen types of this technique are presented, along with a discussion of the parameters that affect performance and process flow. Depending on the proposed method, the influence of various factors on the quality and yield of the obtained products was analyzed. Nowadays, the link between these two properties is extremely important. The work presented in the article refers to research aimed at modifying injection molding methods enabling high product quality with high productivity at the same time. An important role is also played by lowering production costs and reducing the negative impact on the environment. The review discusses modern injection molding technologies, the development of which is constantly progressing. Finally, the impact of the technology on the ecological environment is discussed and the perspectives of the process were presented.

Impact of a Novel Phosphoramide Flame Retardant on the Fire Behavior and Transparency of Thermoplastic Polyurethane Elastomers

In many application fields of thermoplastic polyurethane (TPU), excellent flame retardancy and transparency are required. However, higher flame retardancy is often at the expense of transparency. It is difficult to achieve high flame retardancy while maintaining the transparency of TPU. In this work, a kind of TPU composite with good flame retardancy and light transmittance was obtained by adding a new synthetic flame retardant named DCPCD, which was synthesized by the reaction of diethylenetriamine and diphenyl phosphorochloridate. Experimental results showed that 6.0 wt % DCPCD endowed TPU with a limiting oxygen index value of 27.3%, passing the UL 94 V-0 rating in the vertical burning test. The cone calorimeter test results showed that the peak heat release rate (PHRR) of the TPU composite was dramatically reduced from 1292 kW/m² (pure TPU) to 514 kW/m² by adding only 1 wt % DCPCD. With the increase of DCPCD contents, the PHRR and total heat release gradually decreased, and the char residue gradually increased. More importantly, the addition of DCPCD has little effect on the transparency and haze of TPU composites. In addition, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were carried out to investigate the morphology and composition of the char residue for TPU/DCPCD composites and explore the flame retardant mechanism of DCPCD in TPU.

Modelling and Simulation of MuCell®: The Effect of Key Processing Parameters on Cell Size and Weight Reduction

Microcellular injection moulding is an important injection moulding technique to create foaming plastic parts. However, there are no consistent conclusions on the impact of processing parameters on the cell morphology of microcellular injection moulded parts. This paper investigates the influence of the main processing parameters, such as melt temperature, mould temperature, injection pressure, flow rate, shot volume and gas dosage amount, on the average cell size and weight reduction of a talc-reinforced polypropylene square part (165 mm × 165 mm × 3.2 mm), using the commercial software Moldex 3D. The effect of each parameter is investigated considering a range of values and the simulation results were compared with published experimental results. The differences between numerical and experimental trends are discussed.