Higher Weight Reduction Research Articles

Fabrication of Polyether–Ether–Ketone Foams with Superior Properties and Mitigated Weld Lines by Microcellular Injection Molding

Polyether–ether–ketone (PEEK) as an engineering plastic with excellent mechanical properties requires strict processing conditions. Introducing microcells in PEEK parts is beneficial for reducing the material cost and improving their tenacity. Herein, foamed PEEK parts are fabricated using microcellular injection molding with supercritical nitrogen as the blowing agent. Using optimum processing conditions obtained from orthogonal array experiments based on finite‐element simulation, the foamed PEEK parts achieve a 10% average weight reduction and display a typical sandwich structure with an average cell size of 30 μm in the core region. The cell size is larger, whereas the cell density and skin layer thickness are smaller in the region near the gate than the region far from the gate. The foamed PEEK parts show a slight drop in the tensile modulus and tensile strength but a significant improvement in the elongation at break when compared with the solid parts. Moreover, the foamed PEEK parts with weld lines exhibit less reduction in tensile properties than the solid counterparts, attributed to their tighter interfacial adhesion at the weld line. This study successfully produces foamed PEEK parts with high weight reduction and ductility and provides insights into the weld line mitigation through microcellular injection molding.

The Feasibility of Using Pulsed-Vacuum in Stimulating Calcium-Alginate Hydrogel Balls.

The effect of the pulsed-vacuum stimulation (PVS) on the external gelation process of calcium-alginate (Ca-Alg) hydrogel balls was studied. The process was conducted at four different working pressures (8, 35, 61, and 101 kPa) for three pulsed-vacuum cycles (one cycle consisted of three repetitions of 10 min of depressurization and 10 min of vacuum liberation). The diffusion coefficients (D) of calcium cations (Ca2+) gradually reduced over time and were significantly pronounced (p < 0.05) at the first three hours of the external gelation process. The rate of weight reduction (WR) and rate of volume shrinkage (Sv) varied directly according to the D value of Ca2+. A significant linear relationship between WR and Sv was observed for all working pressures (R2 > 0.91). An application of a pulsed vacuum at 8 kPa led to the highest weight reduction and shrinkage of Ca-Alg hydrogel samples compared to other working pressures, while 61 kPa seemed to be the best condition. Although all textural characteristics (hardness, breaking deformation, Young’s modulus, and rupture strength) did not directly variate by the level of working pressures, they were likely correlated with the levels of WR and Sv. Scanning electron micrographs (SEM) supported that the working pressure affected the characteristics of Ca-Alg hydrogel structure. Samples stimulated at a working pressure of 8 kPa showed higher deformation with heterogenous structure, large cavities, and looser layer when compared with those at 61 kPa. These results indicate the PVS is a promising technology that can be effectively applied in the external gelation process of Ca-Alg gel.

The effect of injection process for microcellular foaming on the cell morphology and surface quality of Polyamide 6

Microcellular foamed polymers have been widely used in the traffic field. However, it is difficult to successfully manufacture microcellular foamed products that simultaneously possess good cell morphology, small size, high cell density, and great surface quality. In this paper, polyamide 6 (PA6) injection microcellular foams were manufactured via short-shot and core-back foaming process to investigate the effect of the foaming process on cell quality and surface quality. Results showed that the core-back injection PA6 foams possessed a smaller cell size, higher cell density, lower cell deformation, and greater surface glossiness than short-shot foams. The cell density of core-back PA6 microcellular foams reached to 12.5 × 105 cell/cm3, which is almost 3.5 times greater than that of the short-shot foams when the weight reduction was 10%. The PA6 microcellular foams manufactured via the core-back foaming process had higher surface glossiness with different weight reduction, whereas the surface glossiness of short-shot microcellular foams dramatically declined with an increase in weight reduction. Hence, the core-back foaming process can be used to fabricate microcellular foamed polymers with good cell morphology, small size, high cell density, and fine surface quality under high weight reduction; this was beneficial for producing products that have good surface quality and high weight reduction and are used in automobiles, high-speed trains, and airplanes to reduce energy consumption.

Polypropylene/talc foams with high weight-reduction and improved surface quality fabricated by mold-opening microcellular injection molding

Microcellular injection-molded part can save materials usage and reduce energy consumption. However, the part molded by conventional microcellular injection molding often encounters problems of a limited weight-reduction and poor surface quality. Focusing on these problems, this paper adopted mold-opening microcellular injection molding and talc as nucleating agent to prepare foamed polypropylene (PP) part. Different PP/talc composites were obtained by twin-screw extruder compounding, and their crystallization and rheological behaviors were investigated. The results show that talc can significantly promote PP crystallization, and the crystallization temperature changes slightly with talc content. However, the viscoelasticity of PP melt cannot be enhanced by the added talc. Then, the effects of packing time, mold-opening distance and talc content on the foaming behavior of PP were studied. It is found that a high packing pressure for long time can effectively eliminate the cells generated in melt filling process, thus a transparent part is obtained. With increasing packing time, the unfoamed skin layer of the part increases and cell size decreases. With increasing mold-opening distance, cell density increases. At a same mold-opening distance, cell density remarkably increases because of the heterogeneous nucleation of talc, thus cell size decreases. When talc content is 10 wt.% and weight-reduction of the part is 62.1%, the average cell size is 56.5 μm and the cell density reaches 1.54 × 107 cells/cm3. Because the high packing pressure is employed in the mold-opening microcellular injection molding, the surface quality of the part is improved.

Efficacy of Partially Purified Soybean Protease Inhibitor on The Development of Cotton Leafworm, Spodoptera littoralis (Bosid.)

Plant protease inhibitors) PIs) are one of the plant strategies to maintain favorable growth and survival. Soybean trypsin inhibitor is the most well-known of the plant serine proteinase. The present study aims to detect the inhibitory activity of two concentrations of partially purified trypsin inhibitors from seeds of soybean(Glycine max). Comparing the results of feeding larvae on partially purified soybean inhibitors with control, revealed that the larval weight reduction caused by soybean PI was noticed after seven days of treatment. The highest larval weight reduction was obtained due to treatment with SPI at levels SPI 30% and SPI 60%, and there was no significant difference between the two levels. Feeding larvae on SPI 60% caused higher larval mortality about 20% than the control followed by SPI 30% which caused 16% larval mortality. The pupation in treated larvae was delayed two days by comparing to control. The highest weight reduction in pupal weight was 3.5± 0.3 gm at SPI 60% compared with control. Besides, the pupation rate decreased from 83% at SPI 60% to 80% at SPI 30%. Also, the reduction in adult emergency % was recorded at SPI level 30% by 41% and at SPI level 60% by 16% compared with the control. Results reveal that soybean protease inhibitors inhibit the growth and development of S. littoralis, and may be used in integrated pest control strategies.

A study of high-speed joining method using spiral nails

• The high-speed joining method using the nail with spiral grooves was proposed in this study. • It was seen that the optimum angle of the spiral groove on the nail was 270° in the high-speed joining condition in this study. • If the nail has the optimum groove angle, the ultimate shear tension force of the proposed method was about twice higher than that of the blind rivets. • If the nail has the optimum groove angle, the ultimate cross tension force of the proposed method was almost the same as that of the blind rivets. A variety of materials have been used to assemble transportation equipment in order to realize both securement of high strength and weight reduction in recent years. In the manufacturing fields, various joining methods are used, and there are as many methods as material variations. Among those joining methods, mechanical joining can join without heating or melting materials. We have proposed a high-speed nailing method using a spiral nail in order to improve the joining strength in this study. The proposed method is characterized by spiral grooves provided on nails, which bite joined parts to improve joining strength. Using nails with several spiral groove angles, this study has verified effectiveness of the spiral groove angles of the nail and also revealed the mechanism of the method that affects joining strength. Incidentally the proposed method can joint dissimilar materials at high speed without supporting behind clamped plates. Since the nail has the spiral grooves, we can easily remove the nails by rotating the nail in the opposite direction. Therefore the method is suitable for recycling and maintenance.

A novel smart assistive knee brace incorporated with shape memory alloy wire actuator

The knee plays a significant role in locomotion and stability of the entire body through supporting the body weight and assisting the lower body kinematics during walking. However, the knee is at constant risk of becoming weakened due to disease, age, and accidents. One approach to treating weakened knee is wearing an assistive knee brace. To design a clinical knee brace, many factors such as weight and compliant mechanism should be considered. In this study, a novel smart assistive knee brace mechanism incorporated with wire actuators made of shape memory alloys is proposed to ameliorate the issues associated with weight and flexibility of existing brace designs. Unlike earlier studies, the proposed orthosis includes pressure sensor, shape memory actuator, and smart linkage. Furthermore, two distinct shape memory alloy actuator design concepts with improved stiffness are developed, and the best option is chosen systematically and prototyped. The novel mechanism proposed in this research overcomes the weight of the lower limb during swing phase using the combined shape memory alloy actuation and feed-forward controller design. As such, it can be used as a potential replacement to its conventional counterparts when the higher weight reduction as well as a flexible and controllable mechanism are simultaneously sought.

Impact of adjunctive tolvaptan on sympathetic activity in acute heart failure with preserved ejection fraction

AimsAcute decompensated heart failure (ADHF) is generally treated by decongestion using diuretic therapy. However, the use of loop diuretics is associated with increased cardiac sympathetic nerve activity (CSNA). We aimed to evaluate the effect of adjunctive tolvaptan therapy on CSNA in ADHF patients with preserved left ventricular ejection fraction (LVEF).Methods and resultsWe enrolled 51 consecutive ADHF patients with LVEF ≥45%. Patients were randomly assigned to receive either tolvaptan add‐on (n = 25) or conventional diuretic therapy (n = 26). Cardiac iodine‐123 metaiodobenzylguanidine (MIBG) imaging was performed after stabilisation of heart failure symptoms, and the cardiac MIBG heart‐to‐mediastinum ratio (HMR) and washout rate (WR) were calculated. There were no significant differences in the body weight change and total urine volume during 2 days after randomisation or in the HMR on delayed image (HMR(d)) and WR between the tolvaptan and conventional groups. After stratification based on the median change in body weight, the patients with higher weight reduction had a significantly lower HMR(d) (P = 0.0128) and tended to have a higher WR (P = 0.0786) in the conventional group, whereas the cardiac MIBG imaging results were not influenced by body weight reduction in the tolvaptan group.ConclusionsAdjunctive tolvaptan therapy may provide rapid decongestion without a harmful effect on CSNA in ADHF patients with preserved LVEF.

Performance analysis of composite ply orientation in aeronautical application of unmanned aerial vehicle (UAV) NACA4415 wing

The advancement in today's material science has driven composite materials to globally use in aircraft design with its superiority in high structural stiffness and significant weight reduction. Composite structures ordinarily comprise of laminates with various fiber orientation angles offers unique outcome, hence lead to optimized design for composite structure. The paper deals with the layerwise finite element model for static structural analysis of a CFRP laminated composite of unmanned aerial vehicle (UAV) wing. The objective of this study is to compare the results for different orientation of ply combinations which contributed to the high performance of composite materials that exhibit both orthotropic strength and stiffness properties. Both properties present unique challenges for analysis and design. The study is further up to determine the optimum design for selected ply combination on a wing with a tubercle design at the leading edge of the wing. Tubercles mimicking the protuberances on the leading edge of a Humpback whale pectoral flipper, offering great performance from an aerodynamic perspective. Hence, optimum design of composite is found from the tabulated stress and displacement for each ply combination, where the tubercles design at the leading edge of UAV wing showed better performance with a reduction in 38.75% of deformation and 46.83% of stress, compared to normal leading edge of NACA4415 airfoil.

Gravimetric, electrochemical and surface study on the good’s buffer ionic liquid as corrosion inhibitor for carbon steel in acidic medium

This corrosion study assessed the inhibition performance of carbon steel in 1 M of hydrochloric acid (HCl) using Good’s buffer ionic liquids (GBIL) namely 1-Butyl-3-methylimidazolium 2-(N-Morpholino) propane, [BMIM][MOPS] using electrochemical impedance, potentiodynamic polarization, and weight loss (gravimetric) measurements. GBIL are synthesized by the combination of Good's buffer as anion and various organic bases as the cation. The gravimetric measurements exhibit higher reduction in weight for carbon steel exposed to the acidic environment in the absence of corrosion inhibitor (CI) as compared to carbon steel immersed in the presence of inhibitor molecule. Potentiodynamic polarization study indicates that the synthesized inhibitor acted as a mixed type inhibitor. The inhibition efficiency increases with increase in the concentration of [BMIM][MOPS]. Corrosion protection efficiency ranging from 88% to 90% was featured at 800 ppm of CI in the HCl medium. The adsorption of [BMIM][MOPS] on the carbon steel surface was described by the Langmuir's adsorption isotherm. The scanning electron micrographs inspected the morphology of the carbon steel surface exposed to the solution without and with the presence of inhibitor. The result showed that compound effectively suppressed corrosion by the appearance of an improved surface structure of carbon steel with increasing concentration of [BMIM][MOPS].

Association of biomass fuel use with reduced body weight of adult Ghanaian women

The association of biomass fuel use with body weight has never been investigated. We therefore examined the effect of biomass fuel use on body weight of adult Ghanaian women. Data from the 2014 Ghana Demographic and Health Survey, a nationally representative population-based survey was analysed for this study. A total of 4751 women who had anthropometric (height and weight) data qualified for inclusion in this study. In linear regression modelling, charcoal use resulted in 3.08 kg (95% CI: 2.04, 4.12) and 0.81 kg/m2 (95%CI: 0.29, 1.33) reduction in weight and body mass index (BMI), respectively, compared to clean fuel (electricity, liquefied petroleum gas and natural gas) use. Use of wood resulted in much higher reduction in weight and BMI. In modified Poisson regression, charcoal users had 19% (Adjusted Prevalence Ratio [aPR] = 0.81; 95%CI: 0.71, 0.92) and 29% (aPR = 0.71; 95%CI: 0.61, 0.83) decreased risk of overweight and obesity, respectively, compared to clean fuel users. Wood users had much higher decreased risk of overweight and obesity. In conclusion, biomass fuel use was associated with reduced body weight and BMI of Ghanaian women and is the first report on the relationship. However, it is important that our findings are confirmed and the biological mechanisms elucidated through rigorous study designs.

Moderation of Mood in the Transfer of Self-Regulation From an Exercise to an Eating Context: Short- and Long-Term Effects on Dietary Change and Obesity in Women.

Behavioral obesity treatments require an improved understanding of the dynamics of associated psychological changes. This study aimed to clarify previous research on self-regulatory skills' transfer from an exercise to eating context, effects of mood on self-regulatory strength, and related effects on a targeted eating behavior. Women with obesity participated in a yearlong community-based cognitive-behavioral treatment that first focused on self-regulatory skills development for exercise maintenance, then use of similar self-regulatory skills and improved mood to facilitate short- and long-term increases in fruit/vegetable intake and reduction in weight. Groups were based on high (≥ 5% of baseline weight; n = 51) and low (< 5%; n = 49) weight reduction 2years post-initiation. Improvements in eating self-regulation and fruit/vegetable intake were greatest in the high weight-reduction group. Using lagged variable analyses to assess directionality, mood significantly moderated the prediction of eating self-regulation change by exercise self-regulation change. The effect of increased exercise self-regulation on fruit/vegetable intake change over 6months was significantly mediated by eating self-regulation change. Participants' initial weight moderated the effect of eating self-regulation change on fruit/vegetable intake. Change in eating self-regulation over 6months predicted self-regulation at 24months. Short-term change in fruit/vegetable intake predicted weight change over 2years through its association with long-term fruit/vegetable consumption. Findings supported the expected carry-over of self-regulation from an exercise to eating context, mood effects on self-regulatory strength, and associations of exercise with eating and weight changes via effects on psychological variables. Results have implications for sustained effects associated with behavioral treatments.

The effects of daily food ingestion on improved immune functions and health promotion of bodybuilding athletes.

The purpose of this study was to investigate the effects of different weight reduction methods on the body composition characteristics, cardiopulmonary functions, and health promotion of elite bodybuilding athletes in a comprehensive manner. For this purpose, the study analyzed the effects of two different weight reduction methods on 25 elite bodybuilding athletes registered at the Bodybuilding Association over a period of 6 weeks. There were interactive effects on macronutrients, macrominerals, and antioxidants according to weight reduction methods as the experiment group (6%±2%) maintained a certain amount of food intakes across various nutrients including energy intakes or made a slow decrease it, whereas the traditional group (16%±4%) made a sharp decrease in it due to relatively greater weight reduction than the experiment group and thus showed pattern differences from it. As for immunity variables, there was an increase to certain cytokines despite the traditional high weight reduction method, but it caused no excessive reduction of immunity or rapid decrease to certain factors of body composition. In addition, there were no significant differences in main and interactive effects on the one-repetition maximum of bench press and squat, which are two functional indicators of health promotion. These findings imply that the low weight reduction method within the range of 6%±2% minimized or maintained changes to muscle circumference or mass while causing no improvement to muscular strength.

Foaming Mechanism of Polypropylene in Gas-Assisted Microcellular Injection Molding

In our recent study, it is reported that gas-assisted microcellular injection molding (GAMIM) is a promising method to fabricate plastic foams with good surface quality, high weight reduction, and improved mechanical performance. To clarify the foaming mechanism, the crystallization behaviors of polypropylene in both conventional injection molding (CIM) and gas-assisted injection molding (GAIM) were studied. It is found that GAIM can significantly promote melt crystallization and refine crystals. To explore the improvement mechanism of crystallization, a numerical model was developed to simulate the filling and cooling processes of CIM and GAIM. The simulation results show that the much stronger shear field and the faster cooling rate lead to the refinement of crystals in GAIM. Finally, a crystallization-driven cell nucleation model was proposed to explain the improved foaming behavior of polypropylene in GAMIM. This paper provides a deep understanding of the foaming behavior and hence benefits the foaming process design.

Investigation of tribological and mechanical properties of aluminium boron carbide composites using response surface methodology and desirability analysis

PurposeAluminium metal matrix composites are used in automotive and aerospace industries because of their high performance and weight reduction benefits. The current investigation aims to focus on the development of the stir cast aluminium-boron carbide composites with enhanced mechanical and tribological properties.Design/methodology/approachThe aluminium-boron carbide composites are produced by stir casting process. Aluminium alloy A356 is chosen as the matrix material and three sets of composites are produced with different weight fractions of boron carbide particles. Higher particle size (63 µm) of boron carbide is chosen as the reinforcement material. Aluminium-boron carbide composites are tested for mechanical and tribological properties. The effect of process parameters like load, speed and percentage of reinforcement on the wear rate are studied using the pin-on-disc method. The interaction of the process parameters with the wear rate is analysed by DesignExpert software using RSM methodology and desirability analysis. The coded levels for parameters for independent variables used in the experimental design are arranged according to the central composite design. The worn surface of the pin is examined using a scanning electron microscope. The phases and reaction products of the composites are identified by X-ray diffraction (XRD) analysis.FindingsAluminium-boron carbide composites reveal better mechanical properties compared to monolithic aluminium alloys. Mechanical properties improved with the addition of strontium-based master alloy Al10Sr. The ultimate tensile strength, hardness and compressive strength increase with an increase in the reinforcement content. The wettability of the boron carbide particles in the matrix improved with the addition of potassium flurotitanate to the melt. Uniform dispersion of particles into the alloy during melting is facilitated by the addition of magnesium. Wear resistance is optimal at 8 per cent of boron carbide with a load 20 N and sliding speed of 348 RPM. The wear rate is optimized by the numerical optimization method using desirability analysis. The amount of wear is less in Al-B4C composites when compared to unreinforced aluminium alloy. The wear rate increases with an increase in load and decreases with the sliding speed. The wear resistance increases with an increase in the weight fraction of the boron carbide particles.Practical implicationsThe produced Al-B4C composites can retain properties at high temperature. It is used in nuclear and automotive products owing its high specific strength and stiffness. The main applications are neutron absorbers, armour plates, high-performance bicycles, brake pads, sand blasting nozzles and pump seals.Originality/valueAl/B4C composites have good potential in the development of wear-resistant products.

Predictors of weight reduction and maintenance in a large cohort of overweight and obese adults in a community setting.

In overweight/obese individuals, modest 5% weight loss and its maintenance promotes health; however, it is challenging and typically unachievable, especially in community settings. Established predictors of weight loss outcome in a community setting are lacking, hindering the development of practical interventions and prevention tools. Our aim was to identify predictors associated with 5% weight reduction (initial 6 months) and maintenance (1 year) in overweight and obese adults undergoing weight reduction treatment, free of charge, in a community setting. Computerised medical files of 11 842 adults aged 50.6 ± 16.3 years, attending 162 primary clinics, were analysed retrospectively. Thirty medical, biochemical and demographic independent variables were tested as potential predictors using multiple logistic regression models. Significant predictors of high successful weight reduction were: not being treated with insulin (odds ratio (OR) = 0.53), higher baseline body mass index (OR = 1.05) and younger age (OR = 0.98). Weight maintenance predictors were: successful initial weight reduction (OR = 1.26), short time intervals between weighings (OR = 0.88) and frequent weighing (OR = 0.95). Visits to a dietitian were significantly associated with success during both periods: each visit raised the probability of success by 13.4 and 7.6%, respectively. Type 2 diabetes or use of hypoglycaemic drugs were not significant predictors. In a community-based setting, number of visits to a dietitian is a strong predictor of successful weight reduction and maintenance. Initial success is a critical predictor of weight loss maintenance. Subgroup of older, diabetic patients treated with insulin has a dramatically lower probability of weight reduction success.

Additive Manufacturing Technology Development: A Trajectory Towards Industrial Revolution

With the recent advancement in complexity of various technological products and the need for faster production, the quest for inventing new manufacturing technologies to reduce the design limitations such as the costs involved in purchasing and maintaining machines, the need for a trained operator, and increase in waste produced during machining in conventional manufacturing methods, has received significant boost in recent time with the advent of additive technology (AM) or 3D printing within various experts in industry, research & development institutes and universities, which invariably has not only enhanced deliverable on time and on budget of products, as well as ability to fabricate complex geometry with high precision and weight reduction. Several types of additive manufacturing (AM) that use different technologies and materials have emerged, in which the 3D systems are used to produce objects through adding rather than subtracting materials, transforming essentially detailed design files to fully functional products, to directly or indirectly alleviate the burden associated with convectional manufacturing and assembly methods. In this paper, an extensive review has been done on several methods adopted in 3D printing. Example include: Fused Filament Fabrication (FFF), Selective Laser Sintering (SLS), Continuous Filament Fabrication (CFF), Stereolithography (SLA), Atomic Diffusion Additive Manufacturing (ADAM) and Selective Laser Melting (SLM). The various steps involve in operation and working principle of 3D printing technology was also stated. The paper also presents the applicable areas of 3-D printing focusing on tooling, aviation/aerospace, medical/biomechanical and city planning.

Measurement of a Conduction Cooled Nb3Sn Racetrack Coil

Use of superconducting coils for wind turbines and electric aircraft is of interest because of the potential for high power density and weight reduction. Here we test a racetrack coil developed as a proof-of-concept for cryogen-free superconducting motors and generators. The coil was wound with 1209 m of 0.7-mm-diameter insulated tube-type Nb3Sn wire. The coil was epoxy-impregnated, instrumented, covered with numerous layers of aluminized mylar insulation, and inserted vertically into a dewar. The system was cooled to 4.2 K, and a few inches of liquid helium was allowed to collect at the bottom of the dewar but below the coil. The coil was cooled by conduction via copper cooling bars were attached to the coil but also were immersed in the liquid helium at their lower ends. Several current tests were performed on the coil, initially in voltage mode, and one run in current mode. The maximum coil Ic at 4.2 K was 480 A, generating 3.06 T at the surface of the coil. The coil met the design targets with a noticeable margin.

A novel free-hanging 3D printing method for continuous carbon fiber reinforced thermoplastic lattice truss core structures

Continuous Fiber Reinforced Thermoplastic (CFRTP) lattice truss core structures are potential to aerospace engineering because of their high weight reduction efficiency and multifunctional application. A novel free-hanging 3D printing method was firstly presented by the authors to manufacture CFRTP lattice truss core structures. The free-hanging printing path generation strategy was established to realize the undercut and overhanging truss structure without any support. Based on the free-hanging 3D printing method, the typical lattice topologies and more complex structures like the integral variable-thickness wing were printed. The cross sectional morphology of samples printed by using the free-hanging printing method were analyzed. The investigations on the parameters such as relative density, fiber volume content and truss angle were conducted to reveal the relationship between the process parameters and out-of-plane compressive properties. The experiment results demonstrated that the average structural error was about 1.89% compared with the theoretical geometry. The compression strength of the printed sample was 224% higher than that of the pure thermoplastic resin counterpart. The specific compressive strength of free-hanging printed samples was in competitive status compared with currently existed CFRTP lattice structures in available literatures.

A novel gas-assisted microcellular injection molding method for preparing lightweight foams with superior surface appearance and enhanced mechanical performance

This paper proposed a novel gas-assisted microcellular injection molding (GAMIM) method by combining the gas-assisted injection molding (GAIM) with the microcellular injection molding (MIM). Firstly, under the assistance of the high-pressure gas from the GAIM, the amount of the polymer melt required for fully filling the mold cavity is reduced in the GAMIM compared with that in the MIM, thus leading to a high weight reduction of the foamed part. Secondly, the high-pressure assisted gas from the GAIM can dissolve all the cells generated in the melt filling stage back into the polymer melt, thus improving the molded part's surface appearance by eliminating the surface sliver marks. Thirdly, the secondary foaming process in a steady state triggered by releasing the high-pressure assisted gas makes the foamed part have a fine cellular structure and a compact solid skin layer, which can help to enhance the part's mechanical properties. In order to verify the effectiveness of the GAMIM, comparison experiments of the MIM and the GAMIM were conducted. The results demonstrate that the GAMIM can not only significantly increase the weight reduction, but also greatly improve the surface appearance and mechanical properties of the foamed part.