bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blowing Agent Emission Calculations for a Refrigerator
Authors: Shankland I. R. 
Published: July 2017

This paper presents an outline of a model which can be used to estimate the concentration of blowing agents emitted from the foam insulation into the cavity of a domestic refrigerator. The basic assumption of the model is that blowing agent is emitted from the foam via a diffusion process and finds its way into the refrigerator cavity via holes and slots (for feed-throughs, shelves, etc.) which are cut in the plastic liner. The concentration of blowing agent inside the refrigerator decays asymptotically with time and depends on the diffusion coefficient and initial concentration of blowing agent in the foam, the number and surface area of holes through the plastic liner, whether or not the foam is adhered to the plastic liner, and the air exchange rate for the refrigerator. The model calculations indicate that, under normal operating conditions, the blowing agent concentration inside the refrigerator is very low, typically, parts per billion by volume. It is believed that the assumptions on which the model is based are conservative, i.e., the model over-estimates the concentration of blowing agent in the refrigerator. The sensitivity of the calculated concentrations to these assumptions is also discussed.
Effective Diffusion Coefficients of CO2 and HCFC-22 in Polyurethane and Polyisocyanurate Foams
Authors: Bhattacharjee D. , Booth J. R. 
Published: July 2017

Thin-slice accelerated desorption of gases using a gravimetric methodology has been used to determine effective diffusion coefficients of both carbon dioxide and HCFC-22 in thermoset foam structures. Foam samples consisting of a polyurethane appliance foam and a polyisocyanurate boardstock foam both blown with CFC-11, and polyurethane foams blown with HCFC-22 and carbondioxide have been employed as polymer substrates for the desorption measurements. A modification of the sorption equations has been developed to describe the special case of two component simultaneous desorption from a uniformly heterogeneous continuum. One component must desorb significantly faster than the other component to separate the individual weight-loss slopes. For those foam samples that were manufactured with CFC-11 and the diffusion of the blowing agents is still occurring, the initial slope must be determined. Core slices from each sample, 0.25 cm thick, were allowed to saturate with air. The sample weights were monitored daily for several weeks. The initial blowing agent loss slopes, weight against scaled age, were determined for each slice. The slices were then saturated with a gas mixture, of 1 atmosphere air and 0.5 atmosphere of the secondary gas, either CO2 or HCFC-22, for one month. After the gas pressure was vented to the ambient atmospheric pressure, the slice weight was monitored until the weight curve for a slice coincided with the continuation of the initial blowing agent slope for that slice. The difference (increase) in the slope of weight loss during the desorption of the recharged blowing agent was used to compute the effective diffusion coefficient for the sample. The average diffusion coefficient of CO2 was found to be approximately one order of magnitude higher than that of HCFC-22 (i.e., 7.0 × 10-8 compared to 6.6 × 10-9 cm2/sec) through a foam co-blown with HCFC-22 and CO2. The ratio of the effective diffusion coefficients of CO2 and HCFC-22 was not, however, constant from one polymer substrate to another.
Dimension-Dependent Long-Term Aging of Cellular Plastic Insulations
Authors: Fan Youchen , Kokko Erkki 
Published: July 2017

The commercially available closed-cell cellular plastic insulations are typically faced by gaseous impermeable metal foil to prevent transfer of gases from inside and from outside of the foam. Thus, the long-term aging properties of the foams will be different from the unfaced situation. In this research, it has been found by experiments and simulations that the long-term thermal conductivity of the faced foam will follow a simple logarithm correlation. [ILLEGIBLE] Where AX is the thermal conductivity increase of the foam after some years later (say 25 years); P is the perimeter of the unfaced surfaces of the foam; A is the unfaced surface areas of the foam; αo and α1, are determined constants. In addition, this research will give this correlation with respect to the CFC-11 and n-pentane based cellular plastic insulations (CPI) under different facing conditions.
Carbon Black in Appliance Foam Insulation
Authors: Pisipati J. S. , Ball E. E. , Galligan P. L. , Gluck D. G. 
Published: July 2017

Efforts are continually being made to improve the insulation efficiency of appliance foam to reduce dependency on fossil fuels and to meet federally mandated product energy use requirements. These efforts have become even more important due to impending elimination of chlorofluorocarbons (CFCs) as the blowing agent for polyurethane and polyisocyanurate foams. Conversion to hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) generally leads to decreased insulation value of foams and therefore, decreased overall energy efficiency for the appliances. The effects of incorporating carbon black to reduce thermal conductivity of HCFC-141b blown appliance foams are discussed. The work was jointly carried out by Miles Inc. and the Center for Applied Engineering. Studies previously conducted at the Center had demonstrated that carbon black is well suited for use in rigid insulating foams, particularly in urethane-modified isocyanurates. The Celotex Corporation has now commercialized this technology in the building insulation market. Improvements of 6-9% in initial k-factors were observed when carbon black dispersed in polyols or isocyanates was used either in TDI- or PMDI-based appliance systems. The use of carbon black in HCFC-141b blown systems has the potential to produce foams with insulation values equivalent to CFC-11 blown production foams. The very fine particle size and inert character of commercially available carbon blacks allow loadings up to 12% by weight in foam polymer. Since the dispersions can result in excessively high viscosities, efforts were also directed towards modifying formulations to improve flow characteristics. Various approaches were taken to optimize carbon black loading in reactants as well as to facilitate processing in the foam process equipment.
Performance of MDI Pour-in-Place Automotive Seating Incorporating Recycled Content
Authors: Hicks D. A. , Kirk A. C. , Stapleton R. J. 
Published: July 2017

Increasingly, the automotive industry is requiring demonstration that polymers in automotive applications are recyclable. The techniques for the recovery and recycling of polyurethane foam from MDI Pour-in-Place automotive seating have been demonstrated. This seating technology is uniquely suited to the recovery of foams for physical and chemical recycling. The pulverization of flexible foam and its physical recycling back into automotive seating is described with estimations of the costs involved and performance of the resulting product. Recent work on the chemical recycling of MDI automotive seating is outlined.
An Image Analysis Method for Cell-Size and Cell-Size Distribution Measurement in Rigid Foams
Authors: Lewis K. M. , Kijak I. , Reuter K. B. , Szabat J. B. 
Published: July 2017

The basic morphological unit of a closed cell rigid foam is the gas-filled cavity surrounded by cell walls and struts. Typically, these cavities (cells) are pentagonal dodecahedral or tetrakaidecahedral. Their average dimensions and dispersity are known to influence foam physical properties and foam performance. We have devised a reliable method for the measurement of cell-size and cell-size distribution which exploits both geometry and statistics, and which has allowed the realization of useful correlations and trends in our development of rigid foam formulations and additives. A thin slice of foam (100-300 microns) is subjected to optical microscopy and image analysis. Measurements of the areas of cell windows and of the average ferets of these windows are made independently. Windows are usually pentagonal, hexagonal or square and are variously distorted. Cells are assumed to be dodecahedral and cell diameter ( d) is calculated by the formulae: d = 2.1354 (area)1/2 d = 1.7013 (feret) Thereby, two independent determinations of cell diameter are obtained from each window viewed. Values are typically within 2% of each other. Cell-size distribution is quantified by measuring a large number (~ 500-1000) of windows and calculating the simple and weighted averages. This paper will present the mathematical basis for the method, illustrate the excellent agreement between the window area and the feret cell-size determinations and demonstrate the utility of cell-size and cell-size distribution data in physical property correlations, for example for k-factor.
The Elimination of Radiative Heat Transfer in Fine Celled PU Rigid Foams
Authors: Eeckhaut G. , Cunningham A. 
Published: July 2017

Considerable research in the early 1980s led to the identification of radiative heat transfer as a major contributor to the overall thermal conductivity of PU rigid foam. Fundamental heat transfer analysis showed that for foam model matrices in which the primary variable was cell-size, an approximately linear relationship was obtained between the radiative heat transfer thermal conductivity contribution λ rad and cell-size. λ rad, was shown to theoretically decrease to below 1 mW/mK when foam cell-sizes were reduced to about 50 μ. This decrease to below 1 mW/mK is considered in this presentation as an effective elimination of the radiative heat transfer mechanism. With the establishment of a phase-out timetable for R-11, considerable global research activity was focused on the development of fine celled technology capable of exploiting these predictions. In recent years technology for the production of closed cell foams with cell-sizes in the range 100-300 μ have been developed. More recently open celled foams have now been developed for vacuum panel applications with cell-sizes down to the 50 μ level. This series of foams provided a unique opportunity to determine directly the real level of radiative heat transfer that occurs and to therefore determine for the first time the real effectiveness of polyurethane foam matrices to attenuate radiative heat transfer. The theoretical framework for the investigation adopts what is known as a 3 flux approximation, which allows both absorption and scattering contributions to be taken into account. Spectral I-R directional-hemispherical transmission and reflection measurements were performed using an integrating sphere accessory on a BIORAD FTS-40 spectrometer equipped with a CsI beam splitter. The wavelength region of investigation covered 98% of the black body spectrum. From the experimental reflection and transmission spectra and the three flux approximation method, the spectral extinction coefficient was determined and then Rosseland averaged. From this Rosseland averaged extinction coefficient, the foam radiative thermal conductivity λ rad at a mean temperature of 283°C was calculated. Using a mean intercept length analysis of an SEM characterization of the foam both parallel and perpendicular to the symmetry axis, it was possible to determine the Z-average cell-size. Analysis of the results displayed a strong linear relationship of λ rad, with the Z-average foam cell size. It is shown that for the very fine open celled foams designed for vacuum panel applications, λ rad values below 1 mW/mK could be obtained. This remarkable level of radiative attenuation for PU foam, in combination with the expected thermal conductivity contribution from solid conduction, is shown to strongly support their suitability as potential vacuum insulation matrices.
Research of HCFC Blown Integral Skin Foam[UNKNOWN]mMorphology Study
Authors: Lee L. J. S. , Tsai C. C. , Yuh N. H. 
Published: July 2017

HCFCs are well-known to be the most likely liquid candidates which would replace CFC-11 as the blowing agent for polyurethane rigid foam and polyurethane integral skin foam. HCFC-123 (CHCI2CF3) is utilized in this research effort for replacing the conventionally used CFC-11 (CCl3F) in the polyurethane integral skin foam with ozone depletion potential (ODP) level as high as 1.0. CFCs should be phased out prior to 1996. First, suitable polyurethane integral skin foam is selected from formulation screen bench tests which employ HCFC-123 as the physical blowing agent (optimal chain extender/amine catalyst/organotin catalyst combination). Second, the formulation is scaled up to a pilot plant type line. Additionally, SEM (Scanning Electronic Microscopy) technology is used to study the influence of the factors (i.e. the blowing agent, the overall density, the processing parameters and the position of the product) on intermediate layer morphology. A morphology model has already been proposed by Shutov (morphology of integral polymer foams[UNKNOWN]mMacromol. Chem., Macromol. Symp. 2, 1986) which concerns itself with the intermediate layer between the skin and the core foam of polyurethane integral skin foam. Polyurethane integral skin foam intermediate layer morphology by SEM technology has not yet been reported in previous literature. Applying SEM technology toward studying the polyurethane integral skin foam intermediate layer is a topic of valuable interest. The research information contained within could be presented as a reference for the complete replacement of CFCs in the polyurethane integral skin foam which, subsequently, would be aimed toward the final goal of solving global environmental problems caused by the ozone layer depletion from CFCs.
Recycling of Rigid Polyurethane Articles and Reformulation into a Variety of Polyurethane Applications
Authors: White Walter R. , Durocher David T. 
Published: July 2017

Recycling of thermoset polymeric materials offers a unique challenge. It is often assumed that thermoset materials in general, and polyurethanes specifically, are not recyclable or only recyclable in limited applications as regrind. Herein, we report the recyclability of polyurethane materials by glycolysis and recovery of a polyol. The glycolysis technology utilized is unique in that the residual free amine content is very low, and the entire reaction mixture is useful as a urethane polyol. This is in contrast to other glycolysis technologies that involve separation steps and ultimately in the production of other more hazardous waste streams. The reaction proceeds at ambient pressure and moderate temperature obviating the need for highly sophisticated control mechanisms. The recyclate properties are relatively insensitive to the waste stream utilized, thus permitting the mixed waste streams as raw materials in the process. In this investigation, high density non-cellular rigid urethanes have been successfully glycolyzed and formulated into a variety of polyurethane systems. These include applications in energy management technology, as well as other rigid and semi-rigid applications. Inclusion of the recyclate shows little detriment to the physical properties of the resulting polyurethane in a variety of applications. An example of a closed loop recycling strategy is demonstrated in rigid insulating foam. A cyclopentane blown rigid polyurethane can be glycolyzed and the resulting polyol incorporated into the original system at up to 20% of the polyol component with excellent dimensional stability and thermal conductivity results. Up to 100% replacement shows little sacrifice in physical properties. Preliminary laboratory results also show excellent potential for both rigid insulation foam and high density, rigid, non-cellular polyurethanes to be amenable to the glycolysis process. This paper describes aspects of our efforts to meet the challenge posed by an increasing number of our customers to render polyurethanes readily recyclable.
Amide-Modified Polyisocyanurate Foams Having High Thermal Stability
Authors: Zhang Zhongyi , Ashida K. 
Published: July 2017

Due to increased fire regulations in the building industry, urethane-modified isocyanurate foams (U-IR foams) have been widely used in place of flame retardant rigid urethane foams. However, commercial U-IR foams still have inherent defects in thermal stability, flammability, friability, and smoke density. This paper discusses a novel method for the preparation of amide-modified isocyanurate foams (A-IR foams) having excellent thermal stability and low friability. A-IR foams having higher thermal stability and higher flame retardation than those of U-IR foams were prepared using quasi-prepolymers prepared by the reaction of adipic acid with a polymeric MDI at about 70°C in tetrahydrofuran as solvent and at unusual COOH/NCO equivalent ratios of 1/30 to 1/10. After the reaction is completed, tetrahydrofuran was distilled out. In contrast, the one shot process using adipic acid as modifier resulted in inferior foams. As control, U-IR foams were prepared using prepolymers made by the reaction of 1,6-hexanediol with the same polymeric MDI. Both A-IR and U-IR foams were prepared using the prepolymers, HCFC-141b as blowing agent, and the same surfactants and catalysts. The thermal stability of the amide linkage is higher than that of the urethane linkage, and therefore, the resulting A-IR foams exhibited higher thermal stability than that of U-IR foams. The higher thermal stability of the A-IR foams resulted in higher temperature resistance, lower flammability and less smoke generation. In addition, A-IR foams exhibited lower friability even at high equivalent ratios. On the other hand, U-IR foams having the same NCO/OH equivalent ratios exhibited higher friability. Detailed studies in the relationship between chemical structure and properties were carried out. These studies included the effect of equivalent ratios on foam properties, e.g., thermal stability, friability, compressive strength, flammability, etc. The effect of catalysts on the reaction profile was also investigated. Comparison of thermal stability by means of TGA and of surface flammability by means of the Butler Chimney flammability test exhibited outstanding improvements in the A-IR foams in comparison with U-IR foams. In view of these data, it could be concluded that A-IR foams prepared by the quasiprepolymer process at high equivalent ratios exhibited superior properties. Accordingly, amide-modified polyisocyanurate foams could be advantageously used for high-rise building insulation, chemical plant insulation, residential insulation, etc. in place of urethane-modified polyisocyanurate foams.
New Insight into the Chemical and Morphological Differences between Slab and High Resilient Foam Elastomers
Authors: Lidy W. A. , Rightor E. , Thanh H. Phan , Cadolle D. 
Published: July 2017

By use of Small Angle X-Ray, Infrared and Rheology methods a wealth of knowledge has been generated in the past about the formation and final morphology of the elastomers which constitute Flexible Polyurethane Foams. The current view is that Slab foam polymers have a three phase structure with polyurea microdomains, macrophase separated polyurea and the soft polyether phase. High Resilient foam polymers do not show the polyurea macrophase and have less of the strongly hydrogen bonded urea visible in IR. The chain length of the polyurea segments is unknown due to experimental difficulties with isolating these structures from a crosslinked polymer. A new method is being described using monols of the same equivalent weight in place of the triols and separating the species containing the hard segments according to their length by solvent extraction. The chemical composition of the urea segment can then be analyzed by 13C NMR or IR. It was found that a considerable number of short urea chains are present in both Slab and HR foam polymers.
The Effect of Blowing Agent Solubility on the Long Term Dimensional Stability of Rigid Polyurethane Foams
Authors: Singh S. N. , Biesmans G. , Karremans M. , Randall D. 
Published: July 2017

More environmentally acceptable blowing agents, such as hydrochlorofluoro-carbons (HCFCs), hydrofluorocarbons (HFCs), hydrocarbons, and carbon dioxide have now replaced chlorofluorocarbon (CFC) blowing agents in many rigid polyurethane (PUR) and polyisocyanurate-modified polyurethane (PIR) foam applications. However, these new blowing agents were not simply "drop-in" replacements for CFCs. In most cases, the structural matrix of the foam had to be adapted in order to accommodate the new blowing agent. Concerns about the long term performance of these new technologies have led to extensive programs of research, not only to address thermal performance, but also to understand the effects of these blowing agent changes on mechanical properties. While a great deal of progress has been made, the polyurethane industry is still in need of a means to fully assess long term mechanical and dimensional stability performance. One particular problem related to the long term dimensional stability of rigid polyurethane foams is the effect of blowing agent dissolution into the polymer matrix. Such dissolution may cause a softening of the matrix known as a "plasticization effect." In order to reduce the risk of mechanical failure, foam density may be increased, in order to strengthen the foam. However, this raises foam cost, and makes polyurethanes less competitive against other insulation materials. Clearly, the rigid polyurethane foam industry is in need of an accurate means of predicting lowest reasonable density which provides acceptable long term performance. This paper describes the results of a new test designed to quantify the plasticization effect, which provides a fast and accurate means of assessing long term dimensional stability. The new methodology was successfully applied to a number of PUR and PIR foams, expanded with several blowing agents. The degree of blowing agent uptake into the matrix was quantified, and its effects on mechanical properties of the foam was established. In addition, a few correlations were drawn between the new test and real life long term performance data. The results indicate that the methodology presented in this paper allows for effective prediction and quantification of possible plasticizing effects associated with any blowing agent in a PUR or PIR matrix.
Vibrational Characterization of Various Polyurethane Foams Employed in Automotive Seating Applications
Authors: Kinkelaar Mark R. , Cavender K. Doug , Crocco Guy 
Published: July 2017

As vehicle seat designs have moved from a spring/foam composite design to a foam/pan or deep foam design the vibrational characteristics of the foam has become increasingly important. It is now necessary to understand how to improve the vibrational properties of polyurethane foam to assure a comfortable ride and attenuation at the appropriate frequency ranges. It has been demonstrated via modeling foam vibrational characteristics that one can optimize the vibrational performance of foam by simply comparing foam peak frequency and peak transmissivity—these properties predict the foam transmissivity curve. Foam technologies included in this work were TDI HR, TDI hot cure and MDI HR systems. Data were presented which explored how vibrational properties correlated to foam IFD and ball rebound. Regression analysis data were also presented which demonstrated how foam formulation and processing variables could change foam vibrational characteristics. Generally, TDI chemistry provided the desired lower natural frequency response and was the least sensitive to processing variables. An understanding of these trends is the first step to assuring a quality ride for deep foam seating.