Yuxuan Xu

Injection molding (IM) is one of the most essential forming methods for plastics. However, some potential risks which influence part quality may occur in the molding process. A non‐return valve (NRV) is a major component on the screw head whose function is to seal during the injection process to prevent the backflow of the melt. The NRV will wear in this process and cause fluctuations in parameters and quality but the wear states of NRVs cannot be monitored without the disassembly of the injection barrel. In this study, we proposed an optimization method to compensate for the wear damage of the NRVs. The V/P switchover point in each molding cycle was recalculated and output to stabilize the part quality. As a result, the wear damage of the NRV on the current machine was able to be predicted and the part quality could be initially optimized in the condition that the NRV had a degree of wear. The experimental results reveal that our proposed compensation algorithm can monitor the type of wear of NRV online, and at the same time, it can compensate the axial wear of NRV and finally improve the consistency of product weight, which established a fundamental for further research in the future.

Recently, ever-increasing requirements of the application environment with respect to working efficiency, environmental adaptability and energy efficiency, it is impossible for traditional active heat dissipation technologies to adapt to the needs of modern electronic components which are miniaturised and highly integrated. To achieve high heat flux conduction in micro spaces, for example, it will significantly reduce the utilization ratio of internal space of electronic components if we use traditional cooling techniques such as wind cooling and water cooling. In this and similar applications, a heat dissipation system which can improves both heat flux density and utilization ratio of space is urgently needed, while efficient heat-dissipating coatings can perfectly fit for this application requirement, addressing the limitations that problems of heat dissipation present in the development of this realm. In this paper we review the research status of efficient heat-dissipating coatings at home and abroad and analyse the rational application of heatdissipating coatings, especially those working in infrared radiation mode, under different requirements.

Injection molding (IM) is one of the essential forming methods for thermoplastic polymers, which is widely used in modern industries such as automobiles, electronics, and medical industries. At present, the machine parameters of the IM machine (IMM) have achieved sufficient high control accuracy and repeatability. However, the viscosity of thermoplastic melt is still easily influenced by the external environment, such as the fluctuations in batches, the compounding in recycled materials, and so on. Conventional IM equipment cannot sense and conduct adjustments correctly, which leads to the production of rejects. A real‐time monitoring and controlling model employed for viscosity compensation was established in this article, which could monitor viscosity fluctuations and implement self‐adjustment in the IM process. Three kinds of polypropylenes (PP) with different viscosity and materials with different percentages of recycled pellets were randomly added into the barrel for comparison. The results revealed that the pressure integral relative to time is able to monitor the melt viscosity and illustrate the IMM to optimize the V/P switchover and packing pressure in the current molding cycle. The part weight could achieve a higher stability and the model could bring about a decrease in weight fluctuations of 50% to 70%.

Injection molding machines are widely used to fabricate plastic products with complex geometries and structures. They consist of an injection unit and a clamping unit. To withstand the pressure of the mold cavity, the clamping unit needs a high clamping force to hold the mold halves. Unfortunately, the clamping force is among the overlooked parameters of the injection molding parameters. Setting the clamping force at max is needed in practice to avoid flash defects for most operators. However, excessive clamping force creates problems for the machine. This study proposes a verification method for determining optimal clamping force based on the clamping force change ΔCF. When ΔCF becomes zero, the current set value of the clamping force is appropriate. A positive and negative ΔCF corresponds to an excessive and insufficient set value of the clamping force, respectively. Verification experiments are implemented on an electric injection molding machine with polypropylene (PP). The experimental results show that the novel strategy can basically calculate and identify the optimal clamping force with iteration method. The optimal clamping force value for current working conditions (620kN) is acquired after several automatic molding trials, which provides a direction for further research.

In this study, polyethylene (PP)/polyethylene terephthalate (PET)/multiwalled carbon nanotube (MWCNT) nanocomposites with nanofibrillary structure were processed by hot drawing‐assisted extrusion technology, and nonfoaming and microfoaming samples were processed by injection molding machine. Scanning electron microscope micrographs showed that when PET content was 2.5 wt%, PET fibers had a larger aspect ratio, which brought an outstanding promotion on microfoaming of PP matrix, and further details were provided by DSC and rheology analysis. When foaming sample loaded with 2.5 wt% PET and 3 wt% MWCNT, the best shielding effectiveness achieved 29.91 dB·cm³·g⁻¹ in the test frequency range about 8.2–12.4 GHz. The results proved that the introduction of PET fibers optimized the microfoaming effect, and the uniform cell structure promoted the MWCNT dispersion and internal reflection of electromagnetic wave. Therefore, the shielding property is absorption‐dominated type and meets the requirements of lightweight and ultraefficient shielding demand of industry.

Recent trends in energy and environmental protection have led to many studies of high‐performance microcellular foams. Polymer blends provide an effective way to improve foamability, microstructure, and performance versus single component thermoplastics. However, challenges remain for morphological control of polymer blends because the reinforcing effect depends upon the morphology of the dispersed phase. In this work, we present a feasible method for attaining microfibrils with high aspect ratios based on the in situ fibrillation of immiscible polymers to improve the morphology and distribution of the blend phase and improve the microcellular structure and mechanical properties of composite foams. Composite foams of polypropylene (PP)/thermoplastic polyester elastomer (TPEE)/polytetrafluoroethylene (PTFE) were fabricated, which were the polymer matrix, blend phase, and in situ fibrillation phase, respectively. The presence of PTFE and its effect on crystallization, rheology behavior, cellular structure, and mechanical properties were investigated. The results showed that PTFE microfibrils can promote melt strength, crystallization, and rheology properties. Thus, the multi‐composite foams achieve improved microcellular structure and mechanical properties, and improvements in these properties indicate the positive effects of an in situ fibrillation phase on the polymer blend foams.