Blowing Agents Research Articles

Phenolic Foam Preparation Using Hydrofluoroolefin Blowing Agents and the Toughening Effect of Polyethylene Glycol.

In this work, a new class of fourth-generation, zero ozone depletion potential, hydrofluoroolefin-based blowing agents were used to prepare phenolic foam. While hydrofluoroolefin blowing agents have been used previously to prepare polyurethane foams, few studies have been reported on their use in phenolic foams. We introduce an effective method for foam preparation using two low-boiling blowing agents, cis-1,1,1,4,4,4-hexafluoro-2-butene and trans-1,1,1,4,4,4-hexafluoro-2-butene, and their combinations with hexane. Traditionally, phenolic foams have been prepared using chlorofluorocarbons and hydrochlorofluorocarbons, which can have harmful effects on the environment due to their high ozone depletion potential or global warming potential. Conductor-like screening model for real solvents (COSMO-RS) modeling studies were performed to understand the effects of different blowing agent combinations on their boiling points. A series of phenolic foams were prepared by varying the concentration of the hydrofluoroolefin and the hydrofluoroolefin-hexane blowing agent combinations. The concentrations of the surfactant, Agnique CSO 30, and the toughening agent, polyethylene glycol, were also varied to yield a formulation with the optimal properties. The foams formulated with the hydrofluoroolefin-hexane mixture displayed a higher compressive strength and a lower thermal conductivity than those prepared with either hydrofluoroolefin or hexane alone. The cell microstructure of all the foams was examined using scanning electron microscopy. By introducing flexible chains into the resin matrix, PEG facilitates proper distribution of hydrofluoroolefin-hexane blowing agents and other reagents and thereby increases the mechanical strength of the foam.

Application of CO2-Soluble Polymer-Based Blowing Agent to Improve Supercritical CO2 Replacement in Low-Permeability Fractured Reservoirs.

Since reservoirs with permeability less than 10 mD are characterized by high injection difficulty, high-pressure drop loss, and low pore throat mobilization during the water drive process, CO2 is often used for development in actual production to reduce the injection difficulty and carbon emission simultaneously. However, microfractures are usually developed in low-permeability reservoirs, which further reduces the injection difficulty of the driving medium. At the same time, this makes the injected gas flow very fast, while the gas utilization rate is low, resulting in a low degree of recovery. This paper conducted a series of studies on the displacement effect of CO2-soluble foaming systems in low-permeability fractured reservoirs (the permeability of the core matrix is about 0.25 mD). For the two CO2-soluble blowing agents CG-1 and CG-2, the effects of the CO2 phase state, water content, and oil content on static foaming performance were first investigated; then, a more effective blowing agent was preferred for the replacement experiments according to the foaming results; and finally, the effects of the blowing agents on sealing and improving the recovery degree of a fully open fractured core were investigated at different injection rates and concentrations, and the injection parameters were optimized. The results show that CG-1 still has good foaming performance under low water volume and various oil contents and can be used in subsequent fractured core replacement experiments. After selecting the injection rate and concentration, the blowing agent can be used in subsequent fractured cores under injection conditions of 0.6 mL/min and 2.80%. In injection conditions, the foaming agent can achieve an 83.7% blocking rate and improve the extraction degree by 12.02%. The research content of this paper can provide data support for the application effect of a CO2-soluble blowing agent in a fractured core.

A Method of Simulating the Dissolution Behavior of Physical Blowing Agents. Dissolution Behavior of Physical Blowing Agent in Low-pressure Foam Injection Molding Process (Part 2)

A Method of Simulating the Dissolution Behavior of Physical Blowing Agents. Dissolution Behavior of Physical Blowing Agent in Low-pressure Foam Injection Molding Process (Part 2)

The Polyurethane-Polystyrene Composite—Influence of the Blowing Agent Type on the Foaming Process, the Structure and the Properties

In this study, polyurethane-polystyrene composites (RPURF-EPS) were obtained with the co-expansion method. This method consists of utilizing the heat of the exothermic reaction of polyurethane (PUR) formation to expand polystyrene beads (PSBs). The materials were obtained using polyurethane systems based on the selected blowing agents, such as cyclopentane, a mixture of fluorocarbons and water. The analysis of the foaming process was carried out using a special device called FOAMAT. The characteristic start, rise, gelation and curing times were defined. The rise profile, the reaction temperature, the pressure and the dielectric polarization were measured. The influence of selected blowing agents on the cell structure and physical–mechanical properties of reference rigid polyurethane foam (RPURF) and RPURF-EPS, such as apparent density, compressive strength and thermal conductivity, were evaluated. Based on the research, the blowing agents that have the most beneficial influence on the properties and structure of the composites and that provide the most efficient expansion of PSBs in a light porous composite were found.

Significantly Tunable Foaming Behavior of Blowing Agent for the Polyethylene Foam Resin with a Unique Designed Blowing Agent System.

The chemical blowing agent plays a crucial role in enhancing the performance of the polyethylene (PE) foaming resin during the rotational foaming process. Previously, the conventional blowing agent of the PE resin commonly used pure azodicarbonamide (AZ). It had the unavoidable drawbacks of releasing NH3 and exhibiting strong reactions during the rotational foaming process. Meantime, pure AZ had a relatively high decomposition temperature, resulting in a sharp foaming process. To address the above issues, this work developed a uniquely designed blowing agent system. In this study, a novel blowing agent for the PE resin was successfully synthesized by a one-pot method. This blowing agent consisted of an activator and AZ, which exhibited a lower decomposition temperature and a milder decomposition rate than AZ. The activator was constituted of small-sized ammonium dihydrogen phosphate on the AZ surface, which could be decomposed properly and deliver phosphoric acid and H2O during the foaming process. Then, AZ reacted with H2O under phosphoric acid catalysis. Also, this reaction generated CO2 emission while reducing the emission of NH3 through recombination with phosphoric acid. Moreover, phosphoric acid catalysis caused a decrease in the AZ decomposition temperature. Meantime, the thermal coupling appeared during the foaming process, which could further reduce the decomposition rate. Consequently, the small activator played a key role in regulating cell formation and diffusion. Compared to AZ, the novel blowing agent system significantly reduced the cell diameter of the PE foam resin and enhanced its flexural modulus by 50%. Furthermore, the novel blowing agent facilitated better demolding performance and improved the surface morphology of the PE foam product. This research provides significant foaming behavior regulation for the PE resin during industrial applications.

Dissolution Mechanism of Physical Blowing Agent into the Polymer in Low-pressure Physical Foam Injection Molding Process (Part 1) Effect of Molding Conditions on Physical Blowing Agent Concentration

Dissolution Mechanism of Physical Blowing Agent into the Polymer in Low-pressure Physical Foam Injection Molding Process (Part 1) Effect of Molding Conditions on Physical Blowing Agent Concentration

Study on the Fire Risk of Blowing Agents during Spray-Type Polyurethane Foam Construction

This study investigates the risk of fire explosion caused by the presence of combustible gas in the propellant of spray-type polyurethane foam and the ammonia gas generated during the curing of polyurethane foam. Analysis of domestic fire cases confirmed that when construction work using polyurethane foam spray and fire handling were conducted simultaneously, fire accidents repeatedly occurred because the welding sparks acted as an ignition source on the surface of the polyurethane foam. Experiments confirmed the possibility of fire explosion owing to the presence of flammable substances in the polyurethane foam and the combustible gas in the propellant. The production of ammonia gas increased during the polyurethane-foam-curing stage, and B3 was more dangerous than B1.

Gas foaming of polyphenyl sulfone: Effect of the blowing agents and operating parameters

AbstractPolyphenyl sulfone (PPSU) is a highly stable and rigid polymer with good chemical and mechanical resistance used in automotive and aerospace industries in high‐temperature applications during long‐operating cycles. PPSU foams are applied as core materials in lightweight composites ensuring high strength, fire resistance, thermal and acoustic insulation. In this paper, PPSU slabs are foamed using CO2, N2, and He as blowing agents (BAs). An experimental campaign is carried out to estimate the BAs' diffusivity in the polymer. In details, CO2 diffusivity ranges from 8E‐11 to 1E‐09 m2/s at temperatures from 220 to 260°C; diffusivity of N2 ranges from 2E‐10 to 5E‐09 m2/s (220–260°C) and it is 4E‐09 m2/s for He at 220°C. Foaming tests reveal an expansion ratio as high as 400% for CO2, 130% for He, and 150% for N2.Scanning electron microscopy analysis is also performed on produced samples, obtaining a cell number density of 1.3E07, 2.6E05, and 1.8E06 cells/cm3 when saturating, respectively, with CO2 at 220°C and 100 bar, N2 at 220°C and 100 bar, and He at 230°C and 100 bar.

Behavior Characteristics and Thermal Energy Absorption Mechanism of Physical Blowing Agents in Polyurethane Foaming Process.

Polyurethane rigid foam is a widely used insulation material, and the behavior characteristics and heat absorption performance of the blowing agent used in the foaming process are key factors that affect the molding performance of this material. In this work, the behavior characteristics and heat absorption of the polyurethane physical blowing agent in the foaming process were studied; this is something which has not been comprehensively studied before. This study investigated the behavior characteristics of polyurethane physical blowing agents in the same formulation system, including the efficiency, dissolution, and loss rates of the physical blowing agents during the polyurethane foaming process. The research findings indicate that both the physical blowing agent mass efficiency rate and mass dissolution rate are influenced by the vaporization and condensation process of physical blowing agent. For the same type of physical blowing agent, the amount of heat absorbed per unit mass decreases gradually as the quantity of physical blowing agent increases. The relationship between the two shows a pattern of initial rapid decrease followed by a slower decrease. Under the same physical blowing agent content, the higher the heat absorbed per unit mass of physical blowing agent, the lower the internal temperature of the foam when the foam stops expanding. The heat absorbed per unit mass of the physical blowing agents is a key factor affecting the internal temperature of the foam when it stops expanding. From the perspective of heat control of the polyurethane reaction system, the effects of physical blowing agents on the foam quality were ranked in order from good to poor as follows: HFC-245fa, HFC-365mfc, HFCO-1233zd(E), HFO-1336mzzZ, and HCFC-141b.

Changes and Trends-Efficiency of Physical Blowing Agents in Polyurethane Foam Materials.

This work developed a novel method for measuring the effective rate of a PBA (physical blowing agent) and solved the problem that the effective rate of a PBA could not be directly measured or calculated in previous studies. The results show that the effectiveness of different PBAs under the same experimental conditions varied widely, from approximately 50% to almost 90%. In this study, the overall average effective rates of the PBAs HFC-245fa, HFO-1336mzzZ, HFC-365mfc, HFCO-1233zd(E), and HCFC-141b are in descending order. In all experimental groups, the relationship between the effective rate of the PBA, rePBA, and the initial mass ratio of the PBA to other blending materials in the polyurethane rigid foam, w, demonstrated a trend of first decreasing and then gradually stabilizing or slightly increasing. This trend is caused by the interaction of PBA molecules among themselves and with other component molecules in the foamed material and the temperature of the foaming system. In general, the influence of system temperature dominated when w was less than 9.05 wt%, and the interaction of PBA molecules among themselves and with other component molecules in the foamed material dominated when w was greater than 9.05 wt%. The effective rate of the PBA is also related to the states of gasification and condensation when they reach equilibrium. The properties of the PBA itself determine the overall efficiency, while the balance between the gasification and condensation processes of the PBA further leads to a regular change in efficiency with respect to w around the overall average level.

Limits of Performance of Polyurethane Blowing Agents

A MATLAB program was developed to simulate urethane-forming reactions by solving over a dozen differential equations, energy balance, mass balance, and constitutive equations simultaneously. The simulation program was developed for half a decade to simulate the basic kinetics of polyurethane reactions and more complex phenomena that cannot be obtained in laboratories. In the current investigation, the simulation is applied to determine the limits of the performance of polyurethane foam formation. n-pentane, cyclohexane, and methyl formate were used as physical blowing agents, and water was used as a chemical blowing agent. The simulation code increases the accuracy of the results and makes the foam performance process less time- and money-consuming. Specifically, the MATLAB code was developed to study the impact of physical and chemical blowing agents at different loadings on the performance of rigid polyurethane foams. Experimental data were used to validate the simulation results, including temperature profiles, height profiles, and the tack-free time of urethane foam reactions. The simulation results provide a window for the proper type and the optimum amount range of different physical and chemical blowing agents.

In-Line Monitoring of the Physical Blowing Agent Concentration by Transmission Near-Infrared Spectroscopy with High-Pressure Resistance Fiber Optic Probes for Foam Injection Molding Processes

In-Line Monitoring of the Physical Blowing Agent Concentration by Transmission Near-Infrared Spectroscopy with High-Pressure Resistance Fiber Optic Probes for Foam Injection Molding Processes

Effect of Blowing Agents on Properties of Cellular rubber of Natural rubber / Chloroprene blends

Cellular or sponge rubber can be by expansion of fluid state by gas produced from decomposition of foaming agents [1]. It can be manufactured from various types of rubber and chemicals depending on properties required [2]. Natural rubber can give excellent mechanical properties except for thermal ageing [3]. The objectives of this work were to improve thermal ageing of NR foam by incorporating chloroprene rubber, CR, into NR and foaming NR/CR blends. In order to study the effects of the type of chemical blowing agents on the properties of cellular NR/CR rubber blends, azodicarbonamide (ADC) and oxybisbenzenesulfonyl hydrazide (OBSH) were used as blowing agents and compared. The cure characteristic, mechanical, morphological, and flammability properties of the foams were investigated. The results indicated an increasing chloroprene rubber loading caused the increase in cure time, but decreased in cure rate index. In both cases of foaming agents, the cellular rubbers were found that tensile and tear strength were decreased with CR rubber loading, but the secant modulus and hardness were increased. Compression set was decreased with CR rubber loading. It is also showed that the flammability of NR/CR foam with high CR contents (more than 80%) was better than that with low CR contents. It is also found that using OBSH as foaming agent can produce cellular rubber containing better cell density and cell size distribution than ADC.

Quantitative Detection of Late Blowing Agents C. tyrobutyricum, C. butyricum, and C. sporogenes in Traditional Turkish Cheese by Multiplex Real-Time PCR

Quantitative Detection of Late Blowing Agents C. tyrobutyricum, C. butyricum, and C. sporogenes in Traditional Turkish Cheese by Multiplex Real-Time PCR

Development of Rigid Polyurethane Foams Based on Kraft Lignin Polyol Obtained by Oxyalkylation Using Propylene Carbonate

This study aimed to develop new rigid polyurethane foams (RPUFs) for thermal insulation based on kraft lignin, the main by-product of the pulp and paper industry. Crude lignin-based polyol (LBP) was obtained via the oxyalkylation of kraft lignin using propylene carbonate (PC). A design of experiments (DoE) was used to evaluate the effect of the isocyanate (NCO)-to-hydroxyl (OH)-group’s ratio, the content of crude LBP, the blowing agent (BA), and catalyst on the thermal conductivity and density of RPUFs. Statistical analysis revealed that the increase in crude LBP and BA content in the formulation decreases the thermal conductivity and density of the foams. In addition, the fact that LBP is a viscous polyol containing PC-oligomers appears to affect the cellular structure of RPUFs, and consequently reduces their mechanical and thermal properties. The main novelty of this study consisted in the careful optimization of the formulation, namely, with regard to the type of blowing agent and with the high content of crude LBP obtained from the oxyalkylation of LignoBoost kraft lignin without purification to obtain good quality RPUF that meets market requirements for insulation materials.

The effect of water and sodium hydrogen carbonate content on flexible polyurethane's microstructure, water, and mechanical properties

AbstractIt is well known that blowing agents (BAs) and polyol are essential components in polyurethane (PU) composition. Utilizing renewable sources in the material's formulation might reduce its environmental hazards while extending its possible engineering applications. In this study, the samples have been synthesized by using palm kernel oil‐based polyol (PKOP). Water and sodium hydrogen carbonate (SHB) have been used as BAs. Scanning electron microscopy (SEM) has shown that adding the mix of BAs is causing the cells' average size to increase up to 227% and have reduced the lamellae width by up to 2% in comparison with the reference sample. The water tests have illustrated that combining two parts per hundred polyol by weight (php) water and 25 php SHB to the sample has increased its water capacity up to 617%. However, the samples are only able to retain 6% of the absorbed water at the 7th day. It has been also found that porosity has affected the water uptake and all the samples are following Fick's diffusion law, and diffusion is correlated to the square root of time. Multivariable power least squares method (MPLSM) and moving least squares method (MLSM) have been applied to find the relation between tear resistance value and BAs ratio. It is found that both methods have a dominant variable compared to the other variables, but MLSM provided optimizable equation with better R2.

Eco-friendly particleboards with low formaldehyde emission and enhanced mechanical properties produced with foamed urea-formaldehyde resins

Urea formaldehyde (UF) is the most widely used thermoset glue in the wood composite board industry. UF has formaldehyde emission, which is harmful to the environment and human health. In this study, it was aimed to ensure more efficient use of glue by foaming UF, as well as to reduce the amount of formaldehyde emission and thus to realize a cleaner production. In the UF resin foaming process, egg white (EW) and blood flour (BF) were used as foaming agents, which increased the resin volume by 4–7 times. Ammonium sulfate (AS) was used as a hardener for the UF. The UF resin and AS solid concentrations were 65% and 30%, respectively. The resins used in the production were prepared by blending UF, AS, and blowing agents using a mixer at 1000 rpm. The resin was then sprayed onto the surface of the wood chips via an air gun under 5 bar pressure. The PBs were produced as a monolayer from only a core layer (CL) of wood chips. The obtained PBs were characterized by their physical and mechanical properties and formaldehyde emissions. The morphological characterization of the foamed resins was also examined. The results showed that the foaming process had improved the mechanical properties of the PBs by about 30%; however, no significant differences were found in the physical properties of the PBs. Morphological characterization showed that the UF foaming with blow agents had proved to be successful and the resin volume had been increased 4–7 times by the foaming. Formaldehyde emissions were found to be lower (2.5–5.1 mg/100 g) than for the un-foamed resins (3.95–7.31 mg/100 g). It was concluded that PBs with good mechanical properties and low formaldehyde emission can be manufactured by using 30% less UF resin.

Density Gradients, Cellular Structure and Thermal Conductivity of High-Density Polyethylene Foams by Different Amounts of Chemical Blowing Agent.

LDPE (low-density polyethylene) foams were prepared using the improved compression moulding technique (ICM) with relative densities ranging from 0.3 to 0.7 and with different levels of chemical blowing agents (from 1% to 20%). The density gradients, cellular structure and thermal conductivity of the foams were characterized. The density and amount of CBA used were found to have a significant effect on the cellular structure both at the mesoscale (density gradients) and at the microscale (different cell sizes and cell densities). In addition, the thermal conductivity of the samples is very sensitive to the local structure where the heat flux is located. The technique used to measure this property, the Transient Plane Source method (TPS), makes it possible to detect the presence of density gradients. A simple method for determining these gradients based on thermal conductivity data was developed.

Antimicrobial polyurethane foams blown by CO 2 adducts from polyethylenimines grafted with alkyl quaternary ammonium groups

Based on previous endeavors on antimicrobial polyurethane (PU) foams and CO2-releasing environment-friendly blowing agents, we explored a series of modified polyethylenimine (PEI)–CO2 adducts, serving as both blowing and antimicrobial agents for PUs. For this purpose, a quaternary ammonium chain with a C12 alkyl (C12+), either alone or together with neutral (C8 and C12) alkyls, was grafted onto branched PEI (Mn = 25,000 Da) backbones prior to saturation with CO2. The resultant four CO2 adducts, 5C12+5C8-, 5C12+5C12-, 10C12+- and 15C12+-PEI-CO2 (where the number indicates grafting rate in percentage of each side chain), all can well disperse into PU foaming mixtures, generating flexible PU foams with antimicrobial activity. 15C12+-PEI-CO2 displays the best dispersibility and highest foaming efficiency, while 10C12+-PEI-CO2 is the most antimicrobial toward both Gram positive and negative bacteria. The relatively high grafting rate in 15C12+-PEI-CO2 drives the formation of micelle-like particles in the foaming system; the outermost hydrophobic chains can somewhat prevent the internal quaternary ammoniums from accessing to the negatively charged cell membrane of bacteria, causing a reduction in antimicrobial efficacy compared with that of 10C12+-PEI-CO2. The developed PEI–CO2 adducts might replace the traditional ozone depletion and/or global warming blowing agents, and would show prolonged antimicrobial activity over rapidly leachable small molecule antimicrobial agents.

Low-Density Particleboards Modified with Blowing Agents—Characteristic and Properties

Although lightweight particleboards have been commercially available for years, they still have a number of disadvantages, including difficulty to process, brittleness, low impact strength, and other mechanical resistance. The aim of the paper was to determine the possibility of producing particleboards of reduced density (dedicated for furniture industry) as a result of using blowing agents from the group of hydrazides, dicarboxamides, or tetrazoles, which were modifiers of the adhesive resin used for bonding the particles of the core layer of three-layer particleboards. The concept presents the possibility of producing low-density particleboards in a standard technological process by modifying the adhesive resin, which has not been practiced by others until now. Analysis of the results of testing the particleboards properties with various types of modifiers (blowing agents), glue content (high 10%/12% and low 8%/10%), differing in glue dosing method, and different particle sizes allowed concluding that the most satisfactory effect was found in particleboards made of the variant modified with p-toluenesulfonyl hydrazide. This variant was characterised by the highest mechanical properties (bending strength, modulus elasticity, and internal bond strength) with high dimensional stability. The presented technology proposal can be applied in the industry.