Microcellular Process Research Articles

Understanding the links between glycemic control, management adherence and hemoglobin level among type 2 diabetes mellitus

Patients with diabetes must be monitored for hyperglycemia due to the risk of macrocellular and microcellular complications. High blood sugar levels force the kidneys to work harder to filter blood, which results in renal leakage. The objective of this study was to establish a relationship between glycemic control, management adherence, and hemoglobin level in patients with type 2 diabetes. This study employed a correlational design with a cross-sectional approach and a sample size of 72 respondents selected using purposive technique. Compliance with diabetes mellitus, which includes diet compliance, exercise compliance, medication compliance, and blood sugar monitoring compliance, is strongly correlated with glycemic control levels. Completely contrary, there was no link between hemoglobin levels and adherence to treatment. Microcellular processes of renal function are linked to the interaction between glycemic control and hemoglobin levels.

Investigation on Film-Substrate Interfacial Characteristics of Parts Fabricated Via a Novel Integrated In-Mold Decoration and Microcellular Injection Molding Process

Investigation on Film-Substrate Interfacial Characteristics of Parts Fabricated Via a Novel Integrated In-Mold Decoration and Microcellular Injection Molding Process

Foamability and Special Applications of Microcellular Thermoplastic Polymers: A Review on Recent Advances and Future Direction

AbstractFoaming of thermoplastics is an area of significant research interest. The substitution of any solid polymer with its foamed counterparts not only results in the lowering of material and fuel consumption but also enhances the scope of tailoring of properties for new applications. The key to manufacturing a useful foam is to achieve the desired morphology and volume expansion ratio as per the product requirements. In addition, other properties may become important, depending on the applications. Open‐cell structure, biocompatibility, biodegradability, and cytocompatibility are required in scaffolds. The ease with which a polymeric material can be foamed to achieve the desired properties depends on material characteristics, processing conditions, and the blowing agent. This article reviews key literature related to factors affecting foamability and ways of enhancing the foamability of various polymeric materials. Other highlights of this review include studies on degradation kinetics of biodegradable foams, special morphology development for scaffolds, packaging, and acoustic applications as well as cell seeding studies in scaffolds. In summary, this review is expected to provide direction for future developments in the field of microcellular processing to advance the technology and applications of thermoplastic foams as sustainable materials.

Study of microcellular foaming of polystyrene aided with 45 kHz of ultrasound waves energy

ABSTRACT In the microcellular foam plastic processing, cellular formation stage was being an essential stage since the nucleation and growth of the cell take place within. Based on classical nucleation theory, diminution of the free energy for nucleation, exponentially lead to an increase in the nucleation rate. This can be done by increasing the super-saturation level which achieved by heating the gas-saturated polymer. Hence, the advance is taken out by utilizing the ultrasound wave simultaneously with heating for foaming Polystyrene-scCO2, which, not only to keep the super-saturation degree but also reduce the nucleation barrier. In this work, foaming was conducted under 45 kHz of ultrasound and varying the foaming temperature after saturating polystyrene with scCO2. The results demonstrate, that foaming under ultrasound, the expansion ratio attained up to 1.5 fold, increase along with the heating temperature. Higher cell densities obtained with ultrasound applied at 50°C, however only slight difference can be seen, which about 1010–1011 cell/cm3. From the cell size distribution results, cell distributed around 0.5–3.5 µm, with or without ultrasound applied for 60 and 70°C, Meanwhile at 50°C of foaming, the lowest cell size obtained with the aid of ultrasound in the range of 0.3–2.4 µm.

Computer Analysis of Polyolefins Produced with Injection Molding Process Using Physical Blowing Agents

The complexity of today's plastic parts as well as the costs, quality makes it necessary to recognize potential errors early, already in the development phase of parts and moulds. Therefore, computer analysis became requisite part of any preprocessing phases. Due to the continuous effort decrease product weight and price many new techniques were developed recently. One relatively new end very effective technique is production of light construction products with using foaming agents. The main aim of this paper is therefore focuses on verification of computer analysis of Microcellular injection moulding process using physical blowing agents for the most used group of polymers which are polyolefins.

Morphology Evolution of the Microcellular Polymethyl Methacrylate with Supercritical CO2: Effects of Shear Stress and Orthogonal Vibration

This study presents a foaming system that was developed to generate shear stress as well as oscillatory mechanical vibration in an orthogonal direction. The microcellular processes of PMMA specimens blown with ScCO2 have been conducted to find the optimal processing parameters under the static conditions as well as dynamic conditions. It is evident that the cells are drawn into elliptical geometries sheared circumferential by the rotor rotation in isolation. However, the orthogonal pulsatile axial vibration superimposed on the polymer melt synchronously drives the oriented and elongated cells to isotropy as well as a more homogenous cells distribution and planar structure.

Analysis of the Influence of Microcellular Injection Molding on the Environmental Impact of an Industrial Component

Microcellular injection molding is a process that offers numerous benefits due to the internal structure generated; thus, many applications are currently being developed in different fields, especially home appliances. In spite of the advantages, when changing the manufacturing process from conventional to microcellular injection molding, it is necessary to analyze its new mechanical properties and the environmental impact of the component. This paper presents a deep study of the environmental behavior of a manufactured component by both conventional and microcellular injection molding. Environmental impact will be evaluated performing a life cycle assessment. Functionality of the component will be also evaluated with samples obtained from manufactured components, to make sure that the mechanical requirements are fulfilled when using microcellular injection molding. For this purpose a special device has been developed to measure the flexural modulus. With a 16% weight reduction, the variation of flexural properties in the microcellular injected components is only 6.8%. Although the energy consumption of the microcellular injection process slightly increases, there is an overall reduction of the environmental burden of 14.9% in ReCiPe and 15% in carbon footprint. Therefore, MuCell technology can be considered as a green manufacturing technology for components working mainly under flexural load.

Influence of Packing Phase Parameters in the Optimization of Mechanical, Weight Reduction and Dimensional Properties of Microcellular Foaming Injection Molding of Polypropilene

Microcellular foaming of injected plastics offers the possibility to manufacture parts with reductions in costs and weight if compared with conventional injection molding. For this reason there is an increasing interest in challenging applications such as HEV (hybrid and electrical vehicles) and lightweight material applications in general. Complexity of microcellular injection molding is very high because the final properties of the material obtained depend largely on the processing conditions and these in turn unalterable factors such as mold design and manufacturing. The shrinkage of the molded part must be applied as an oversize of the mold cavity in the design phase. Shrinkage of a microcellular foam depends on the reduction of foam density. Moreover, the piece is designed to get a mechanical performance and meet the dimensional tolerances. Knowing that the reduction of foam density implies a reduction of the mechanical properties and influences the final piece dimensions the conclusion is that the microcellular injection process has a very small process window to fit all these factors. This research focuses on two objectives. First is the variation of post-molding shrinkage in terms of reduction of weight to determine the process window. Second is the determination of mechanical properties which do not show a proportional reduction but exponentially with weight reduction components. The results obtained with a 750 Tons. injection moulding machine equipped with a MuCell plastication unit and a large spiral mold have shown small variations in the dimensions for a predetermined process window and smaller reduction of mechanical properties with weight reductions for 20% talc filled polypropylene. The goal of this applied research is that all experiments have been developed with scaled-industry tools (large injection molding machine, Mucell unit and mold and test parts) comparing with conventional injection molding.

The Effect of Gas Desorption on Foaming Ratio of Microcellular Foamed Plastics

Microcellular plastics (MCPs) are one of the most significant developments in the plastics industry over the last decade. Microcellular plastics keep mechanical strength loss and plastic weight to a minimum through microcells inside MCPs. The size and number of cells inside MCPs have a direct correlation with foaming ratio. The cell size has to be consistent to ensure higher quality of MCPs, and a great number of cells are needed for a high foaming ratio. This underscores the need to control the size and number of cells to meet products' required performance. In the microcellular batch process, saturation and foaming conditions are major factors that influence the size and number of cells. This article describes how desorption time, defined as the time lapse between saturation and foaming processes, affects cell formation. Our particular concern is the effect of varying desorption time on foaming ratio and cell morphology. The general rule is that the shorter the desorption time, the higher the foaming ratio (i.e., more cells of smaller sizes are formed because of more dissolved gas molecules remaining in the sample). In our study, however, an opposite trend was observed for desorption time less than 2 minutes. As such, different desorption times ranging from 1 to 5 minutes were used to systematically investigate the corresponding changes in foaming ratio and cell morphology. A possible mechanism of action for this anomalous phenomenon is suggested.

Microcellular processing of polylactide–hyperbranched polyester–nanoclay composites

The effects of addition of hyperbranched polyesters (HBPs) and nanoclay on the material properties of both solid and microcellular polylactide (PLA) produced via a conventional and microcellular injection-molding process, respectively, were investigated. The effects of two different types of HBPs (i.e., Boltorn H2004® and Boltorn H20®) at the same loading level (i.e., 12%), and the same type of HBP at different loading levels (i.e., Boltorn H2004® at 6 and 12%), as well as the simultaneous addition of 12% Boltorn H2004® and 2% Cloisite®30B nanoclay (i.e., HBP–nanoclay) on the thermal and mechanical properties (both static and dynamic), and the cell morphology of the microcellular components were noted. The addition of HBPs and/or HBP with nanoclay decreased the average cell size, and increased the cell density. The stress–strain plots of all the solid and microcellular PLA-H2004 blends showed considerable strain softening and cold drawing, indicating a ductile fracture mode. Among the two HBPs, samples with Boltorn H2004® showed higher strain-at-break and specific toughness compared to Boltorn H20®. Moreover, the sample with Boltorn H2004® and nanoclay exhibited the highest strain-at-break (626% for solid and 406% for microcellular) and specific toughness (405% for solid and 334% for microcellular). Finally, the specific toughness, strain-at-break, and specific strength of microcellular samples were found to be lower than their solid counterparts.

The Influence of Microcellular Foaming Process on Electrical Conductivity of Conductive Composites

By compounding ordinary plastics and conductive additives, conductive polymers can possess conductivity. Conductive polymers are diverse, ranging from antistatic to static dissipative and electromagnetic shielding. Usually, carbon fiber, carbon black, nickel-coated carbon fiber copper powder and metal powder etc. are used as conductive additives and conductivity is determined by both the type and contents of the additives. In this research, a microcellular foaming batch process, a microcellular injection molding process and microcellular extrusion process were adopted to diversify the conductive properties of one conductive polymer. The results indicated that changes in the conductivity of conductive polymers are observed in a certain range and the hypothesis that foaming samples have a higher conductivity than non-foaming samples was verified under the specific cell size and foaming condition. We concluded that the optimum cell size and foaming rate exist in conductive polymers for maximum conductivity; we also concluded that the use of the microcellular foaming process is expected to form conductive composites.

Study of Vibration Field on Microcellular Foaming in Nucleating Agents

A novel microcellular processing experimental setup was developed in which various nucleation agents were added to foaming material (Polystyrene). The effect of the nucleation agents on cell morphology of foam plastics was studied in the vibration field. The effects of the processing conditions such as nucleating agents, particle size of the nucleating agents, content of the nucleating agents, and the vibration parameters on polystyrene cell morphology were investigated. The cell morphology was analyzed with a scanning electron microscope. The results showed that the samples blown with nucleating agents, in general, had larger cell density and much smaller cell size than the ones without nucleating agents. It is believed that the smaller nucleating agents will be helpful for the larger bubble densities and the smaller cell size. There is the optimum content range for the maximum bubble densities and the minimum average cell diameter in foaming processing with nucleating agents. In the range of vibration parameter, the cell density increases with an increase of frequency and amplitude, and the cell size is the reverse.

Passive mold temperature control by a hybrid filming-microcellular injection molding processing

Microcellular injection molding (also known as Mucell process) with supercritical fluid (SCF) content is capable of producing parts with excellent dimensional stability while using less material, lower injection pressure, and achieving a shorter cycle time. However, most of microcellular processing studies were done on interior morphology, microstructure of the microcellular products, researches and reports on the splay-like appearance, or even a rougher swirl surface which is the restriction for the application of the microcellular injection molding are insufficient. This study investigates the influence of mold temperature on the surface roughness of Polyethylene terephthalate (PET)/Polycarbonate (PC) parts molded by hybrid filming–microcellular injection processing. The PET film is considered as a passive mold temperature controller because of its lower heat transfer coefficient (0.16 J/kg °C) compared with mold base steel of 31.5 J/kg °C. Temperature field changes of mold base caused by different film thickness (0.125 mm, 0.188 mm) were analyzed. The surface roughness of microcellular parts with/without film was measured by a 3D laser microscope. It was found that surface toughness decreases while film thickness increases with minimum surface roughness 1.8 μm. Compared with conventional mold temperature (60 °C), the hybrid molded parts with 0.125 mm film lowered surface roughness from 26 μm to 5.6 μm, to 1.8 μm of 0.188 mm film. And the hybrid processing also improved the uniformity of foamed parts surface quality by eliminating swirl and even surface roughness.

Bubble Nucleation and Growth in Microcellular Injection Molding Processes

Bubble nucleation and growth are the key steps in polymer foam generation processes. The mechanical properties of foamed polymer are closely related to the size of bubbles created inside the material. Thus, it is necessary to study how to improve mechanical strength by producing extremely fine bubbles inside polymer resin. We developed a theoretical framework to help produce uniformly distributed microcellular bubbles and experimentally verified the theoretical analysis results using an injection molding machine modified to make microcellular foaming products.

Effects of Process Conditions on the Mechanical Properties of Microcellular Injection Molded Polycarbonate Parts

In the supercritical fluid (SCF) microcellular injection molding process, the polymer melt is first mixed with controlled SCF, followed by cavity filling, creating millions of micron-sized voids within the solidified parts. Benefits associated with this microcellular foaming process include significant reductions in part weight, processing temperature, clamping force, shrink/ warpage, dimensional instability, and cooling/cycle. The purpose of this study is to examine the effects of process conditions on the mechanical properties of PC parts, injection molded via microcellular foaming. The thickness of tensile test specimens was 2.5 and 1.2mm. For Izod impact tests, a specimen of 3.2mm thickness was used. On average, the weight of parts was reduced by 40%. Melt temperature can be lowered by about 20—30°C (from 320 to 290°C) and cycle time reduced by 40—70%. Higher injection rates resulted in a more uniform foaming structure. In addition, the supercritical fluid microcellular process did not reduce the tensile strength of the molded parts; instead, the impact energy values increased slightly over parts molded by convectional injection molding.

Microcellular Polymers and Composites. Part 1. Types of Foaming Agents and Technologies of Microcellular Processing

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Solid state microcellular foamed poly(lactic acid): Morphology and property characterization

Poly(lactic acid) or PLA is a plant-based biodegrable plastic which exhibits many properties that are equivalent to or better than many petroleum-based plastics. However, there have been few commercial applications due to its lower impact resistance and higher cost than synthetic plastics. In this paper, the concept of creating microcellular foamed structures in PLA as a means to improve its shortcomings is presented. The effect of the foaming conditions (temperature and time) on the void fraction, volume expansion ratio, impact strength and tensile properties of foamed PLA is discussed. Each step of microcellular processing is addressed including: the manufacture of PLA film; the saturation of the samples with gas; the microcellular foaming of PLA; the void fraction determination, volume expansion ratio calculation, impact and tensile property characterization of foamed samples. The microcellular morphologies developed in PLA samples were a strong function of the foaming conditions. Due to the presence of foamed microcells, a twofold expansion ratio and significant improvements in the impact resistance (twofold increase over unfoamed PLA), strain at break (up to twofold increase over unfoamed PLA) and toughness (up to fourfold increase over unfoamed PLA) were achieved in PLA.

Study on viscosity changes with talc in microcellular foaming process

In the processing of microcellular foamed polymer products, one of the most important factors is the dependence of rheology on the mixture ratio of the polymer and the gas used as the blowing agent. The formation of a cell by employing the thermodynamic instability of the gas in a one-phase condition is the principle behind microcellular foaming. The viscosity change of the polymer and gas mixture is important in designing dies and molds and affects the quality of the microcellular foaming product. In this experiment, the extruder was modified to mix polymer with gas under a one-phase melted condition. The mixed polymer with gas was run through various capillary die shapes to measure the change in polymer viscosity against the gas supply rate. This paper describes the effect of talc and the blowing agent on the viscosity in continuous microcellular processes, revealing major factors in determining the viscosity of a polymer and gas mixture.

Microcellular polymers and composites. Part I. Types of foaming agents and technologies of microcellular processing

In the review the principles of technology of microcellular polymers preparations were presented. The process consists of three steps: the bubbles nucleation, growth and stabilization. The examples physical foaming agents most often used such as carbon dioxide or nitrogen were given. Attention is paid to the fact that choice of foaming agent influences the structures of the foams obtained. An important group of chemical foaming agents, being organic or inorganic solid substances decomposing during the foaming process with carbon dioxide or nitrogen release, was also described. Three basic technologies used for microcellular materials preparation, i.e. MuCell (Fig. 1 and 2), Optifoam (Fig. 3) and ErgoCell (Fig. 4) were discussed in detail. The examples of applications of the materials prepared by the technologies mentioned above were given (Fig. 5-9).

Effect of processing conditions on shrinkage and warpage and morphology of injection moulded parts using microcellular injection moulding

This research investigated the effects of processing conditions on the shrinkage and warpage (SW) behaviour of a box shaped, polypropylene part using conventional and microcellular injection moulding. Two sets of 26–1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyse the data. After the injection moulding process reached a steady state, moulded samples were collected and measured using an optical coordinate measuring machine (OCMM), which had been evaluated using a proper repeatability and reproducibility (RR) measurement study. By analysing the statistically significant main and two factor interactions, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the SW of microcellular injection moulded parts most significantly, whereas hold pressure and hold time have the most significant effect on the SW of conventional injection moulded parts. Investigation of the cell morphology indicated that fine and dense cells are not critical for achieving excellent results regarding SW. Also, the present study quantitatively showed that, within the processing range studied, a reduction in the SW could be achieved using the microcellular injection moulding process.