Foaming Temperature Research Articles

Compression Molding of Thermoplastic Polyurethane Foam Sheets with Beads Expanded by Supercritical CO2 Foaming.

Expanded thermoplastic polyurethane (ETPU) beads were prepared by a supercritical CO2 foaming process and compression molded to manufacture foam sheets. The effect of the cell structure of the foamed beads on the properties of the foam sheets was studied. Higher foaming pressure resulted in a greater number of cells and thus, smaller cell size, while increasing the foaming temperature at a fixed pressure lowered the viscosity to result in fewer cells and a larger cell size, increasing the expansion ratio of the ETPU. Although the processing window in which the cell structure of the ETPU beads can be maintained was very limited compared to that of steam chest molding, compression molding of ETPU beads to produce foam sheets was possible by controlling the compression pressure and temperature to obtain sintering of the bead surfaces. Properties of the foam sheets are influenced by the expansion ratio of the beads and the increase in the expansion ratio increased the foam resilience, decreased the hardness, and increased the tensile strength and elongation at break.

Evolution of cell morphology from sub-macroscale to nanoscale in modified thermoplastic polyether ester elastomer via supercritical CO2 foaming

Modified thermoplastic polyether ester elastomer (TPEE) foams with the cell size from sub-macroscale to nanoscale were prepared by solid-phase batch foaming in the presence of supercritical CO2 (scCO2). Multifunctional epoxy chain extender (CE) with the functionality of 9 was incorporated into TPEE to form a moderate crosslinking structure. The rheological property and crystallization behavior of modified TPEE were investigated, and then the cell morphologies of as-prepared TPEE foams were analyzed. It was found that the introduction of branching and crosslinking structure led to an increased melt viscosity and a reduction of crystallinity of TPEE. Moreover, it was identified that the rheological property dominated the foamability at high foaming temperature of 185 °C, and then the fine sub-macroscale cells were seen. Conversely, the change of crystallization behavior mainly affected the evolution of cell morphology at low foaming temperature of 160 °C, and the foams with nano and/or micro cells are obtained. As a result, a series of TPEE foams with the cell morphology from sub-macroscale to nanoscale could be achieved by adjusting the crosslinking degree of modified TPEE and the temperature of supercritical CO2 foaming.

Simulation study of engineered Integral-Layer with Solid-Skin structure in Microcellular Polystyrene Foam using Superheat-Induced-Foaming method

Microcellular plastic foam can be formed by the so-called superheat-induced-foaming method, which known as solid-state foaming process. This process involves the dissolution of the blowing agent (CO2) in polystyrene and foaming the gas-laden polystyrene by induction the superheat on it. This process utilizes the effect of plasticization due to dissolved blowing agent in polystyrene matrices. An interval time which desorption of CO2 occurs, definitely after dissolution CO2 in polystyrene prior the foaming process, would make it is possible to develop the integral layer which consists of transition-cellular-core and solid-skin layer by manipulating the desorption time. In the present study, the solid-skin and integral-core-layer formation is simulated by considering the heat and mass transfer model to predict the solid-skin thickness and classical nucleation theory to predict the amount of cell density. It is concluded that with an increase of desorption time, the solid-skin is thicker, and the cell density is lower, compared with the lower desorption time, thinner solid-skin is obtained. Whereas, an increase in foaming temperature, thinner solid-skin with higher cell density is predicted contrary with lower foaming temperature. Additionally, in this study, the predicted cell nucleation is validated to the experimental results with sum-squared-error about 7.248.

Numerical simulation of foam diversion acidizing in heterogeneous reservoirs

Abstract Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers. Based on the foam diversion principle, the gas trap theory, and volume conservation principle, the foam slug diversion acidizing model was established and solved considering the change of bottomhole temperature and deviation factor of foam. The simulation results show that the change of temperature has a great influence on the diversion effect at the initial stage of injection, but a small influence at the middle and late stage. The effect of temperature on the highly permeable layer is greater than that of temperature on the low permeability layer. The deviation factor of foam is mainly controlled by temperature at the initial stage, and by pressure at the middle and late stage, and the whole process shows a downward trend, which has little influence on the diversion effect. The quasi-skin factor of gas trap is the most important parameter that influences the effect of foam diversion. The water saturation of the low permeability layer rises faster than that of the high permeability layer, and the effect of diversion is obvious. The research results have a strong guiding significance for foam diversion acidizing.

Stability, temperature dependence, and microstructure of high pressure jet-treated dairy foams

The objective of this work was to study the effects of high pressure jet (HPJ) processing on the foaming of whole milk at different temperatures. High pressure jet-treated whole milk (200 and 400 MPa) was foamed at 5, 20, 40, and 50 °C using a custom-made air injection device and the foam expansion and foam stability was compared to a non-HPJ-treated control. Aliquots of the foams (formed at 5 and 50 °C) were extracted for proximate analysis and visualization using confocal scanning laser microscopy (CSLM). The relative foam expansion values for the non-HPJ-treated sample at 5, 20, 40, and 50 °C were 45.5 ± 11.3%, 0 ± 0%, 79.6 ± 9.7%, and 88.2 ± 2.8%, respectively while the 400 MPa-treated sample foam expansion values were 36.4 ± 10.8%, 60.8 ± 5.7%, 50.0 ± 5.3%, and 71.7 ± 3.0%. Notably the HPJ-treated sample foamed at 20 °C while the control milk did not foam at all. Furthermore, the 400 MPa-treated foam was stable for >2 h at all foaming temperatures, unlike the non-HPJ-treated whole milk foam, which completely collapsed in 60 s and 1490 s after being foamed at 5 °C and 40 °C, respectively. CSLM and proximate analysis of the non-HPJ-treated sample revealed differences in foam composition based on foaming temperature with more fat present in the foam formed at 50 °C (3.2 ± 0.3%) than at 5 °C (2.5 ± 0.1%), likely due to the ability of liquid oil (at 50 °C) to migrate to the air-water interface during air incorporation. In contrast, there were no compositional differences in the foams from 400 MPa-treated milk based on foaming temperature, reflecting that there are structural differences, particularly in the fat, compared to the non-HPJ-treated foams. This was supported by evidence of fat-protein complexation and micron-size bubbles in CSLM images of the 400 MPa-treated foam.

Effect of foaming agent concentration and drying temperature on biochemical properties of foam mat dried tomato powder

The purpose of the study was to optimize the effective drying conditions and different foaming agent concentrations on the biochemical properties of foam mat dried tomato powder. Foaming was achieved by using egg albumin as foaming agent and sodium salt of Carboxymethyl Cellulose (CMC) as foam stabilizer with different concentrations. Drying was achieved by using different drying temperatures. The changes in different physicochemical properties of foam mat dried powder viz. total soluble solid (TSS), pH, ascorbic acid, titratable acidity, β-Carotene, DPPH radical scavenging activity were observed. Foams were prepared from different concentrations of egg albumin (3-7% w/w) and sodium salt of Carboxymethyl Cellulose (1%, 0.5%). The drying temperatures were varied from 60°C to 70°C. The drying time changes with different drying temperatures. It was found that the drying time decreased with the increased foaming agent concentrations as well as with higher drying temperature. It takes almost 13 hrs for drying at 70°C. TSS and pH content was increased with the increase of foaming agent concentrations and foam stabilizer’s concentrations but decreased with the increasing temperatures. Ascorbic acid decreased with the increase of foaming agent concentrations and temperatures but increased with CMC concentration. Titratable acidity content of foam mat dried tomato powder was decreased with the increasing foaming agent concentrations but increased with the higher temperatures and decreased CMC concentration. β-Carotene contents increased with the increase of foaming agent concentrations but decreased with the increase of temperatures and foam stabilizer concentration. DPPH free radical scavenging activity increased with the increase of foaming agent, foam stabilizer and temperatures. Based on the maximum retention of physicochemical properties, the optimum treatment of foaming agent was found to be 7% egg white + 1% CMC at 60°C.

Foaming effect influence of PBT / ABS resin as a reducing agent in foamed asphalt

Foamed asphalt provides good environmental protection characteristics and economy. The utilization rate of old materials in foam asphalt recycling technology is higher than that of emulsified asphalt. Due to the lack of performance, the application scope of foam asphalt recycling technology is limited. In order to maintain high utilization rate of recycled asphalt concrete and improve the performance of foamed asphalt mixture, it will be the focus of research. In recent studies, adding a reducing agent into the regeneration process of foamed asphalt is a new technology. According to the test results of reduction performance of asphalt SARA four components, the PBT/ABS resin (Acrylonitrile butadiene styrene modified by Polybutylene Terephthalate) has excellent asphalt reduction effect, and PBT/ABS resin has good compatibility with emulsified asphalt after emulsification. Therefore, based on the existing foaming theory, the influence of asphalt temperature and water consumption on asphalt foaming with PBT / ABS resin reducing agent was designed. The influence of asphalt temperature and water consumption on foamed asphalt modified by PBT / ABS resin reducing agent was discussed. The results show that the PBT/ABS resin has larger foam volume than ordinary foam asphalt, but the average diameter of foam is slightly smaller. Similar to ordinary foamed asphalt, expansion rate and half-life are opposite to that of water consumption. Water consumption and asphalt temperature have significant effects on foaming effect. At the same temperature, with the increase of water consumption, the expansion rate increases and the half-life decreases. Under the same water consumption, the higher the foaming temperature, the greater the expansion rate. However, when the temperature reaches 160 °C, the expansion rate of asphalt does not vary with the temperature. With the increase of temperature, asphalt with different temperature has different optimal foaming water consumption. Finally, the optimum foaming conditions of PBT/ABS resin foam are given as follows: the best foaming temperature is 140 C, the water consumption is 3.8%, the ultimate expansion rate is 21.5%, and the half-life is 22.5s.

Understanding effects of radiation from radiative shock on Richtmyer-Meshkov instability

<sec>Radiative shocks are ubiquitous in stellar environments and are characterized by high temperature plasma emitting a considerable fraction of their energy as radiation. Radiative shocks occur commonly in nature, especially in astronomical systems and inertial confinement fusion. The study of the effects of radiation on Richtmyer-Meshkov (RM) instability will improve our ability to understand and predict the evolution of RM instability under high energy density conditions.</sec><sec>A few experiments have been performed to compare the radiative case with the non-radiative case in Rayleigh-Taylor (RT) instability, thereby studying how the radiative effects change the evolution of RT instability, but the interplay between RM instability and radiative shock has been studied rarely. </sec><sec>This paper reports mainly the role of radiation in the changing of the RM instability. Two experiments are performed at Shenguang III prototype laser facility, the RM instability growth data are obtained by varying the laser intensity. The laser intensity for high-drive experiment is approximately 60% greater than that for low-drive experiment. The target consists of a multiple layer in the axial direction, in which the first layer is a 15μm-thick CH sample serving as an ablator, followed by a 10 μm-thick aluminum used as a shield layer to prevent the preheat effect. The next layer is a 350-μm-thick SiO<sub>2</sub> foam, which is used as a material to produce a radiative shock. The last layer is the CH perturbed sample. There is a sinusoidal perturbation on the surface of CH sample which is adjacent to the SiO<sub>2</sub> foam. The target is irradiated by four overlapping laser beams, and the laser beams produce a large pressure that drives a shock wave, whose velocity can be changed by varying the laser intensity, into the target package.</sec><sec>In the experiments, shock-generated radiative fluxes first ablate the unstable interface which the shock has not passed through, then the shock transmits the unstable interface to produce the RM instability. The images of unstable interface are captured using side-on x-ray radiography, and the experimental results show that the RM growth is suppressed in the experiment for the higher laser intensity. Radiation hydrodynamic code Multi1D is used to evaluate the electron temperature, shock velocity, and electron density. The simulations show that the foam temperature in the high-drive case can reach 80 eV in the front of shock, this energy flows away from the shock front, generating a radiative precursor ahead of the shock. The radiative precursor velocity of 270 km/s is much larger than the shock velocity of 170 km/s, the radiative precursor arrives at the unstable interface before the shock and ablates the unstable interface, so the radiative flux changes the initial conditions of unstable interface. When the shock propagates through the unstable interface, the ablation increases the density gradient length scale and reduces the Atwood number of the unstable interface, so the RM growth is suppressed in the high-drive case because of the ablation of the radiative precursor.</sec>

On the Thermal Signature of the Residual Foam in Breaking Waves

AbstractQuantifying energy dissipation due to wave breaking remains an essential but elusive goal for studying and modeling air‐sea fluxes of heat, gas, and momentum. Previous observations have shown that lifetimes of bubble plumes and surface foam are directly related to the dissipated energy. Specifically, the foam decay time can be used to estimate the timescale of the subsurface bubble plume and the energy dissipated in the breaking process. A mitigating factor is that the foam decay time can be significantly affected by the surfactant concentration. Here we present an experimental investigation of a new technique that exploits the thermal signature of cooling foam to infer wave breaking dynamics. The experiments were conducted in a laboratory wave tank using artificial seawater with and without the addition of a surfactant. We show that the time from the start of the breaking process to the onset of cooling scales with the bubble plume decay time and the dissipated energy, and is not significantly affected by the presence of additional surfactants. We confirm observations from the field of the spatial variability of the temperature of foam generated by an individual breaking event, which has implications for inferring the spatial variability of bubble plume depth.

Highly Efficient Glass Ceramic Thermal Insulation

Alkali-silicate thermal insulation materials (foam silicates) belong to the group of mineral heat insulators. Their main disadvantage is insufficient water resistance, to increase which special water-strengthening additives are introduced into materials. The aim of this work was to obtain and study foam silicates in granular (FGCG) and slab (FGCS) forms using a new production technology characterized by a simple one-stage technological scheme. Natural or technogenic amorphous silica, glassy sodium silicate (with the addition of carbonate or hydroxide) and a carbon-containing foaming agent, were used as the raw materials. Some part of the silica component was included in the binder solution, which made it possible to increase the silicate modulus in the final product to 5-10. This factor together with rather high Al2O3 concentration in the silica raw, made it possible to obtain foamed materials of very high water resistance. Another feature of the applied technology was a high foaming temperature (750–900°C). This factor makes a significant contribution to improving the water resistance of foam silicates, and significantly reducing their thermal conductivity and water absorption. As a result, FGCG was obtained with a bulk density of 170-440 kg/m3 (for FGCS – 300-400 kg/m3), a compressive strength in a cylinder of 0.5-6.3 MPa, a thermal conductivity of 0.046-0.084 W/(m·K) and a water absorption of 7.8-13.5% by volume. Mass loss of the specimens in boiling water was 0.12-0.33%, which puts obtained foamed materials on a par with most waterproof foam silicates being produced today.

The correction of foam glass composition based on its principal parameters

Thermal insulation materials are the main link in solving the problem of enclosing constructions energy efficiency. The number of heat insulators is relatively low, that`s why it is important to develop new insulators that would be better than the existing ones in their characteristics. Such heat-insulating material as foam glass is known, but it is practically not applied, despite the fact that it possesses high heatinsulating and mechanical characteristics, it is non-combustible, durable and environmentally friendly. All the advantages of foam glass are inferior to one drawback. It is the high cost price of this material. If the cost price of foam glass was reduced and its main characteristics were at the same level, foam glass would take a leading position among other heatinsulating materials. The article presents some information about the development of foam glass, in which dolomite flour is used as a foaming agent. The material proposed by the authors has a density of about 200 kg / m3, water absorption of 25%. The material is manufactured at maximum foaming temperature of 750 °C.

Applicability of water glass for the transfer of the glass-foaming process from controlled to air atmosphere

For thermal insulation to be sustainable, its performance and production efficiency must be considered. Foamed glass prepared from the mixture of waste cathode ray tube panel glass (CRT), Mn3O4 and carbon could become such a material assuming that its production efficiency could be improved. In light of this, the aim of the study was to engineer the transfer of the foaming process from inert to air atmosphere without drastically disturbing the primary mechanism of expansion. Foaming of carbon-containing mixtures in air atmosphere is normally a challenge due to premature oxidation of carbon by the oxygen from the air. Here, we systematically investigate how the addition of water glass (WG) affects the process by thermogravimetry coupled with mass spectrometry (TG/MS) and heating-stage microscopy analysis. Further, we propose an explanation about how WG protects the carbon and show that the addition of WG allows for the process to be successfully performed in air atmosphere. Two direct sources of expansion were identified (carbon-Mn3O4 reaction and WG) and quantitatively evaluated, allowing determination of an optimal addition of WG, 12 wt %, for the foaming temperature of 800 °C. The obtained foamed glass samples have a relatively low density and degree of open porosity, which reflects in their low thermal conductivity (λ). The lowest λ obtained was 39 mW m−1 K−1 at a density of 145 kg m−3, which is comparable to the samples prepared in inert atmosphere and best commercial products.

Batch foaming of ultra-high molecular weight polyethylene with supercritical carbon dioxide: Influence of temperature and pressure

This work is aimed at studying the foaming behavior of pure ultra-high molecular weight polyethylene (UHMWPE) with supercritical carbon dioxide (scCO2). The effects of foaming temperature and saturation pressure on the final foam structure were investigated by using two different one-step batch foaming processes. An in-situ high-pressure observing system was used to record the crystal change of UHMWPE film during heating and cooling stages with/without pressurized CO2. The results showed that the cell size and the cell density were affected by the combined effects of crystal, temperature, and pressure. Experimental results with different foaming temperatures showed that higher foaming temperatures led to larger cells and lower cell densities. In the processes of foaming during the heating stage (Proc1) and cooling stage (Proc2), the expansion ratio increased first and then decreased with the increase of temperature. Before obtaining the maximum expansion ratio, compare with Proc2, the cell size and expansion ratio of foams were smaller, and the cell density was higher in Proc1. Experimental results with different saturation pressures showed that higher pressure led to lower cell density and larger average cell diameter in Proc1 due to the reduction of crystals and melt strength. While in Proc2, higher saturation pressure led to higher cell density due to the increase of solubility of CO2, and the cell density decreased as the pressure further increased due to cell coalescence.

Foaming behavior of the fluorinated ethylene propylene copolymer assisted with supercritical carbon dioxide

Foaming behavior of the fluorinated ethylene propylene copolymer (FEP) and its composites assisted with supercritical carbon dioxide (scCO2) as the blowing agent were investigated. The batch foaming process was applied at temperature ranging from 250°C to 265°C and pressure ranging between 12 MPa and 24 MPa. The optimal foaming temperature and saturation pressure were obtained for both pure FEP and FEP composites with 1 wt% different-sized BaTiO3 as nucleating agent. The cell diameter of pure FEP foam ranging from 80–140 µm was observed while the cell diameter decreased to 20–40 µm after adding BaTiO3 particles. The cell density of foamed FEP with BaTiO3 increased significantly from 106 to 108 cells/cm3 and the expansion ratio ranged between 4.0 and 5.5. Moreover, a decrease in an abnormal phenomenon that expansion ratio for the pure FEP foam was observed as the saturation pressure increased. This unexpected phenomenon can be explained by the relationship between foaming and crystallization coupling processes.

Research of the process of foaming of marshmallow mass with synbiotic

Considering that today intestinal dysbiosis to some extent affects about 90 % of the population of Ukraine, it is advisable to develop confectionery products with functional ingredients that can affect the microflora and are used to restore the disturbed balance of intestinal ecostructure. Such ingredients include synbiotics. This paper substantiates the need to develop recipes for confectioneries, including marshmallows, to create new types of pastilles with functional properties. Marshmallow production includes the usage of egg whites in fresh, frozen, or dried form as a foaming agent. In recent years, companies use dry egg whites, which have a number of advantages: increasing the sanitary level of production, reducing production area, improving safety and quality stability of finished products that included it in the formula. The functional and technological properties of dry egg whites have been studied regarding the possibility of obtaining pastille products with high-quality stable foam structure. It has been experimentally established that dry protein should be reduced at 30…40 °C and the optimal foaming ability of the protein is at 40…45 °C. The regularities of the foaming process in confectionery masses with a synbiotic have been determined. It has been found that the marshmallow mass with microencapsulated bifidobacteria and lactulose (5; 7.5; and 10 %) requires 6, 5 and 4 minutes of whisking at 400 rpm to form foam, respectively, whereas the control sample required 8 minutes. The dependence of quality indicators of marshmallow masses (density and air volume concentration) on the foaming temperature has been studied. It has been established that the production of marshmallow mass with a synbiotic of a certain density occurs at 38 °C and the study of air volume concentration confirms that the maximum temperature allowing to produce a high-quality mass is 40 °C. Thus, the whisking temperature required to obtain high-quality and stable foam has been experimentally determined for the marshmallow mass. This research allows us to state with confidence that introducing a synbiotic complex into the structure of a marshmallow mass improves the foaming process which allows to produce high-quality products with soft texture and stable foam structure.

Variations and model of the rheological parameters of low damage BCG − CO2 fracturing fluid

AbstractA BCG − CO2 fracturing fluid composed of a new thickener and CO2 causes low amounts of formation damage, and it can be used to stimulate low‐permeability gas reservoirs with water sensitivity. However, at present the rheological properties of this foam fracturing fluid are unclear, which has limited its field application to some degree. The main purpose of this study was to ascertain the rheological parameters and a model of the BCG − CO2 fracturing fluid. The rheological properties of the BCG − CO2 fracturing fluid were evaluated by using a foam rheological test system. The unfoamed condition test results showed that when the shear rate was lower than 1000 s−1, the effective viscosity exhibited a rapid decreasing trend. The effective viscosity of the BCG − CO2 fracturing fluid was 4 to 26 mPa · s under foamed conditions. The comparison results showed that the viscosity of the BCG − CO2 foam was suitable as a low damage fracturing fluid. The measured data were fitted using the H‐B and power law models in this study. The power law model, by contrast, was fit for describing the relationship between shear rate and shear stress. The foamed condition rheological index n′ first decreased and then increased with increasing foam quality, and the rheological coefficient k′ first increased and then decreased with increasing foam quality. For the different foam qualities, the rheological index n′ first increased and then decreased with increasing temperature. The rheological coefficient k′ showed a decreasing trend with increasing temperature. When an exponential function, in which the foam quality and temperature were independent, was used for fitting, it was not accurate in predicting the rheological properties. The fitting results based on a quadratic polynomial surface model were better. The average calculation errors of the rheological parameters were all less than 3.32%. The findings of this study can help develop a better understanding of the heat transfer and flow coupling process in wellbore and fracture in fracturing treatment.

Influences of high‐impact polystyrene loading on the foaming behavior andflame‐retardantproperties of polyphenylene oxide composites blown withCO2

AbstractPolymeric foam with high expansion ratio, well‐defined cell structure, and excellent flame retardant properties is essential for broadening its applications. Polyphenylene oxide (PPO) is a kind of cost‐effective engineering plastic with excellent flame retardancy, anti‐dripping behavior, and good mechanical strength, but suffers from its poor processability. In this study, microcellular PPO composite foams were fabricated by applying a solid‐state foaming technology using compressed CO2as the blowing agent. High‐impact polystyrene (HIPS) phase was introduced with the aim to improve the fluidity and foaming ability of PPO composites. It was interesting to find that the 18–48% HIPS loading significantly increased the expansion ratio, that is, 1.8–3.3 versus, 10.8–14.3, and broadened the optimum foaming temperature of PPO composite foams, attributing to the miscible character between PPO and HIPS and excellent foaming ability of HIPS. Furthermore, the as‐prepared PPO/HIPS composite foams exhibited high limited oxygen index (LOI) of 22.0–29.9%, low horizontal flammability rate (HFR) of 60.5–141.2 mm/min, and anti‐dripping behavior, and the void fraction was verified to be a critical parameter to determine the flame retardant performance of the composite foam. Besides its lightweight and excellent flame retardant properties, PPO composite foams also presented uncompromised tensile properties and well‐defined thermal insulation properties.

Numerical simulation on bubble wall shape evolution and uniformity in poly(ethylene terephthalate) foaming process

The rheological behaviors of commercial foaming-grade poly(ethylene terephthalate) (PET) were measured and modeled, on the basis of which quantitative simulations on the evolution of the bubble wall shape during PET foaming were conducted. A bubble wall stretching uniformity (BSU) curve was proposed to describe the wall uniformity. A fast dropping BSU curve indicated a nonuniform bubble wall that would lead to the wall rupture. It was shown that the strain hardening and fast relaxation were beneficial for maintaining a uniform bubble wall. Simulations also revealed the initial bubble wall geometry had a strong impact on the bubble wall uniformity. Open-cell foam was produced by aggravating the initial nonuniformity through addition of polytetrafluoroethylene (PTFE) particles. With the analysis on the synergistic effects of bubble rupture and coalescence, the optimized foaming temperature (Topt) for the PET could be determined, which was consistent with the experimental value.

Linking ethylene co-monomer content and stereostructure to polycrystallinity and foam density of random copolymers of polypropylene

Static batch foaming is used in a model investigation aiming to understand and predict the impact of resin molecular structure on the foamability of random copolymers of polypropylene (RCP) for bead foam applications. The foaming behavior of seven polypropylene based resins with ethylene content varying from 0 to 11 mol% can be categorized into two groups related to their respective degrees of regio-defects: below 0.1 and around 0.66 mol%. Increasing the ethylene content from 0 to 4.04 mol% is enough to decrease the foam density by a factor of 6.3, as well as the foaming temperature by 15 °C. For a specific number of stereo and regio-defects, the ethylene content has a linear response with the optimal foaming temperature. Regio-defect impact exhibits a similar linear behavior; however, it is decoupled from ethylene content effects. A hierarchical relationship between the polycrystallinity and the foam mechanism was then drawn. The stress induced by the foam cell growth was shown to provoke the generation of more ordered crystalline structure, adding another layer of complexity in obtaining foams with the desired density.

Synthesis of flexible polyurethane foam for applications in planar orthosis using the response surface methodology

In this work, the process for the formulation of flexible polyurethane foam is presented following a design of experiments for mixtures. The proportion of polyol, diisocyanate, and crosslinker was considered as factors. The response variables considered were foaming time and reaction temperature. The result of the experiments showed that there is an area where the foam formulation is better. This zone is closed with 5% crosslinker, 50% polyol, and 45% diisocyanate, in this formulation denser foams with more uniform bubbles were obtained