Showing papers in "Journal of Cellular Plastics in 1984"

A Basic Study of Heat Transfer Through Foam Insulation

Abstract: the development of improved foam insulations has been an evolutionary process. Current research efforts to develop higher R value foams are handicapped by the fact that the mechanisms of heat transfer through foam are not well understood and a basic model is not available. It is the goal of this paper to help develop a better understanding of the mechanisms controlling heat transfer through foams. This will aid future foam developments and form the basis of a fundamental model for the R value of foam. This work also applies to understanding the aging of foams. In a review of the foam literature, Valenzuela [1] showed that published heat transfer models underestimate the effective conductivity of foams, even when upper limits are used for the contribution of solid and gas conduction. Gas convection within the cells was shown to be negligible and hence could not account for the discrepancy. It was hypothesized that thermal radiation accounted for the balance of

A Basic Study of Aging of Foam Insulation

Abstract: uddihy and Moacanin [1] showed that foam inC sulation can be treated as a homogenous media which obeys Fick’s law of diffusion. Once the effective diffusion coefficients of oxygen, nitrogen and Freon gases in foam insulation are determined, they can be combined with the solution of Fick’s law to predict changes in foam gas composition with time. A gas diffusion model to predict the effective diffusion coefficients must consider both the cell to cell gas transfer processes and the effects of foam geometry on overall foam diffusion. Gas transfer through solid membranes was studied by Graham [2] who defined three stages: 1) adsorption of the gas into one side of the membrane, 2) diffusion of the dissolved gas along a concentration gradient through the membrane, and 3) desorption of the gas to a lower pressure on the other side. This overall process is termed permeation and is driven by the difference in partial pressure of each gas across the membrane. Permeation is the rate determining process for gas transfer from cell to cell in a closed cell foam structure. Cuddihy and Moacanin [1] developed a foam geometry model based on one-dimensional flow through a cubical cell structure with uniform cell wall thickness (see Figure la). More recently, Norton [3] analyzed Freon gas diffusion in polystyrene and polyurethane foams using a cubical cell model and

Rapid Method for Measuring the Hydroxyl Content of Polyurethane Polyols

Abstract: There are many methods to determine hydroxyl cont nt [1-3]. Critchfield [4] and Siggia and Hanna [5] describe most of these: those using acetic anhydride, phthalic anhydride, pyromellitic dianhydride (PMDA), phenyl isocyanate, and 3,5-dinitrobenzoyl chloride. ASTM method D 2849-69 [6] describes the currently accepted acetic or phthalic anhydride methods for hydroxyl contents of polyethers and polyesters. The pressure bottle methods require a 2-h minimum reaction time at 98 °C, a serious disadvantage. Studies directed at overcoming this disadvantage have been reported. Connors and Pandit [3] did kinetic studies on analytical acylations by acetic anhydride. The catalyst N-methylimidazole was reported to be about 400 times more active than pyridine. Krueger and Gnauck [7] have reported the application of N-methylimidazole-catalyzed acylations to the measurement of the hydroxyl numbers of polyether polyols. Steglich, Hofle, and Vorbruggen [8-10] have found that 4-dimethylaminopyridine (DMAP) is approximately 104 times more active than pyridine when used as an acylation catalyst. Connors [4] reported applying DMAP to the titrimetric determination of alcohols. Gnauck, Algeier and Krueger [12] applied DMAP to the determination of the hydroxyl number of polyether polyols by acylation. Side reactions, observed through the rapid discoloration of the reaction mixture, limit the concentration of DMAP that

Three-Phase Silicone Based Syntactic Foams:

Abstract: Relations mise en œuvre proprietes de mousses syntactiques a base de polysiloxane et microbilles de silice

Model System for a Urethane-Modified Isocyanurate Foam:

Abstract: far back as the 1800’s [1,2]. However, it has only been recently that this has been used advantageously to prepare rigid cellular plastics having superior ignition resistance* [3,4]. The foam’s thermal stability is due to the cyclic structure and the hydrogen-free nature of the isocyanurate rings. Generally, the best isocyanurate foams are made by polymerizing polymeric methylene diphenyl isocyanate (MDI). While these foams have excellent ignition resistance, the highly crosslinked structure is brittle [5]. As a result, they have poor compressive strength and are very friable. This has been a considerable handicap for commercialization, and there has been a major effort to synthesize modified foams having a balance of properties. Some of these modifications include adding amide, imide, oxazolidone, carbodiimide or urethane linkages [5-10]. The most popular of these approaches-due to convenience, processability, and economics-has been to make urethane-modified isocyanurate foams [11,12].

Closed-Cell Foam Behavior Under Dynamic Loading-I. Stress-Strain Behavior of Low-Density Foams:

Abstract: Plastic foams are frequently subjected to dynamic .t loads. Low density foams are used as cushioning materials in seating and packaging. As building products, they can be subjected to impulse loading during installation. High density foams find applications in equipment cabinets and materials handling containers, where impact can be expected. In this series of papers, the stress-strain behavior of closedcell foams under dynamic loading is examined. The first two papers examine the behavior of low density foams, typically 2 pcf polystyrene and LDPE foams. The models that have been proposed for stressstrain behavior of closed-cell foams in light of our experiments are first reviewed. Then the loading dynamics of these foams are examined. We concentrate on concentrated load behavior and examine the balance between compressiveness and brittleness for

A self-releasing RIM system for increased productivity, operational simplicity, and improved economics

Abstract: To the urethane RIM industry there are three w rds which seem to have a magical aura about them... internal mold release. Yet most often, these words are greeted with valid skepticism. In a sense they are believed, but not believed. Since about 1973 it’s been the hope of this industry, that an additive-a fairy dust-might be found, which when added to a urethane chemical system, would bring about the &dquo;magic&dquo; of self-release. Not surprisingly, there remains a lingering doubt that it can really be done effectively. Some of this doubt has been the consequence of the urethane chemical industry having often stated and promised that it had a self-releasing system via the power of an internal mold release agent. Thus far, however, none have proven both workable and effective. Those which have been trialed, have demonstrated but limited usefulness-not enough performance value to warrant acceptable commercial use. This paper describes the attainment of an effective self-releasing urethane system for RIM. It is based on Dow Experimental Polyol, XA-10888.00L. This is an amine modified polyol containing an internal mold release agent designated IMR-II.

Rapid Hydroxyl Number Determination by Near Infrared Reflectance Analysis

Abstract: ear Infrared reflectance analysis (NIRA), alN though new to the chemical industry, is an established tool in the agricultural industry. It is widely used for the simultaneous measurement of protein, moisture and fat or oil in grains and dairy products [1-5]. Application of NIRA is largely empirical and depends upon whether or not a linear relationship can be developed between the constituent of interest and the NIR spectrum. When reflectance values (R) are expressed as negative logarithms, the linear equation takes the form:

Primary Hydroxyl Content in Polyols-Evaluation of Two Nuclear Magnetic Resonance (NMR) Methods:

Abstract: he relative concentration of primary and secondTary hydroxyl groups is an important property of polyols which determines the reactivity of polyols toward isocyanates and is a vital factor in determining the type of urethane produced. Until the use of nuclear magnetic resonance spectroscopy, the measurement of the primary to secondary hydroxyl group ratio in polyols was determined using reaction rate methods. These kinetic methods [1-3] generally depend on following the disappearance of reactants, such as phenyl isocyanate or the hydroxy of the polyol, by infrared spectroscopy. Some inherent problems with the rate methods are control of temperature, reagent purity, complexity of apparatus, the possibility of interferences from other reactive components and the availability of valid standard materials.

The Importance of Catalysts for the Formation of Flexible Polyurethane Foams

Abstract: T he properties of flexible polyurethane foams are det rmined mainly by the raw materials, isocyanate and polyol. On the other hand, the processing of foams is controlled by the additives, surfactants and catalysts which are auxiliary agents for economical production. The catalyst system regulates the proportion of isocyanate and water (blowing) and isocyanate and polyol reaction (gelling) in time. The right balance of these two reactions is the supposition for foam processing because a blowing reaction that is too fast results in collapse, a gel reaction that occurs too early in closed cells and shrinkage. Based on this fundamental demand a catalyst system should

Method for Predicting Rigid Foam Demold Properties

Abstract: The incorporation of polyurethane foam as insulaJtion in refrigerators and freezers has historically been accompanied by problems in controlling cabinet dimensions. These dimensional changes are a result of the foaming process itself. During foaming, expansion takes place through the vaporization of fluorocarbon (R-11) and the generation of carbon dioxide from the water-isocyanate reaction. This expansion process, accompanied by the progress of the polymerization and the exotherm of the reactions, results in an increasing internal pressure generated. This process exerts a force upon the outer and inner surfaces of the cabinet. Excessive outer case dimensions are not only an aesthetic problem, but can result in a cabinet which will not fit into predesigned kitchen spaces. These same forces on the inner liner of the cabinet can result in the inability to insert the proper shelving into the cabinet and possible cracking of the plastic liner of the cabinet. Each situation results in an unacceptable product. In order to maintain control of this pressure and its effect on cabinet dimensions, appliance manufacturers utilize foaming fixtures. These structures fit the contour of the cabinet both inside and outside to very close tolerances and are designed to withstand the forces exerted by the expanding foam and maintain cabinet dimensions. However, typical production rates in the industry require that the cabinets be removed from the foam-

Experimental Polyurethane Foam Roof Systems - II.

Abstract: : An experimental roofing installation is described in which polyurethane foam (PUF) was spray-applied directly to metal Butlerib-type metal decks, the roof divided into five approximately equal areas, and the PUF protected with five different elastomeric coating systems. Three of the coating systems were damaged by hailstones about a year after installation; these systems were recoated within 3 years of the initial installation. The current coatings include two of the original coating systems - a plural component silicone and a single component silicone - and those applied over the three systems damaged by hail - a single component silicone, an aluminum filled, hydrocarbon-extended catalyzed urethane, and a catalyzed urethane. The performance of these five PUF systems over a 7-year period is reported. The temperature distributions throughout the roof systems are described. The decay in the thermal conductivity of the PUF roof over a 5-year period is presented, and the energy savings realized by foaming the roof are presented. (Author)

Calculation and measurement of reaction temperatures in rigid polyurethane and polyisocyanurate foams

Abstract: This paper was presented at The Society of the Plastics Industry, Inc., (SPI) 6th International Technical/Marketing Conference, San Diego, California, November 2-4, 1983. The paper is being published herein from the conference proceedings after review by the Editorial Board, but without the customary peer review process. less accurate for unmodified polyisocyanurate foams or mixed polyisocyanurate/polyurethane foams.

Evaluation of Hindered Phenols for Minimization of Foam Discoloration Using the Microwave Scorch Test

Abstract: Antioxidants are added to polyether polyols to protect the integrity of the polyol during processing and storage and to prevent discoloration or scorch of the flexible foam during production. In the latter, the antioxidant retards degradation of the foam during the exotherm which results from the chemical reaction of diisocyanate with water and polyol. It is not uncommon for low density foams to reach temperatures in excess of 160 °C on the foam production line and to maintain these elevated temperatures for several hours before cooling. The scorch can range from a slight yellow discoloration at the center of the bun to the extreme of combustion if the antioxidant system is not adequate for the formulation. The reactions leading to scorch have been suggested to consist of oxidation of remaining amine groups to highly colored quinoid type chromophores in the milder form to thermal and hydrolytic degradation of allophonate, urethane and biuret groups and oxidation of the polyether segments in the more severe instances [1,2]. A large number of factors as listed in Table 1 may promote scorch in flexible foams with the more important being the use of higher water containing formulations used to reduce density while attempting to maintain load bearing properties [3,4]. As the trend toward lower density foams continues, polyol manufacturers have attempted to keep ahead by advances in the understanding of scorch and its inhibition by antioxidants. Generally, this has resulted in the use of higher concentrations of antiox-

Humid Aged Compression Set Phenomena in Water Blown Hr Molded Foams

Abstract: A s the U.S. automotive industry continues its move toward lower density HR molded seating foams in which water provides the sole blowing agent, it has become increasingly difficult to meet the humid aged compression set specifications set by the automakers. The lower density foams are being pursued mainly for economic and weight saving concerns. With the use of more reactant water in the foam formulation, the reaction exotherm is increased, the kinetics of the foaming reaction are changed, the polyurea concentration is increased, and a notably different polymer is produced. Compared to foams produced at low water levels, the new low density, all water blown foams exhibit extremely poor humid aged compression set properties. This paper relates differences in the basic polymer formed from low and high water level foam formulations to humid aged compression set performance. Data concerning the critical test parameters of time, temperature, recovery period, and humidity are also presented.

Nitrileipvc and Other Polymer/Resin Closed Cell Foams:

Abstract: E arly in 1947, the potentialities of vinyl resin combinations were recognized as offering possibilities for making a cellular material possessing extreme buoyancy-a feature not contained in other known cellular products manufactured in the United States. Robert W. Pooley, working for the United States Rubber Company, now UNIROYAL, Inc., and under the direction of Lawrence E. Daly, was assigned the cellular vinyl project. The developed productENSOLITE~ ― resulted in a joint patent being issued to Messrs. Daly and Pooley. Pooley further extended his work on ENSOLITE from the buoyant type of material (used first in Navy Life Vests) to a firmer material having exceptional shock-absorbing properties. One of Mr. Pooley’s most important contributions was the combining of polyvinyl chloride with a vulcanized butadiene-acrylonitrile copolymer to yield

A Technical Update on Mdi Based Molded Flexible Foams

Abstract: Etude comparative des proprietes et utilisations de mousses de polyurethanne a base de MDI et du TDI

Flexible Polyurethane Molded Foams Based in MDI

Abstract: Ameliorations des mousses de polyurethanne a base de diisocyanate de diphenylmethane qui deviennent competitives vis-a-vis des mousses a base de diisocyanate de toluene

Reaction Sequences and the Role of Surfactant in High Resilience Foam

Abstract: L'etude de la suite des reactions chimiques montre que la glycerine a un effet remarquable sur le procede d'expansion de la mousse

Recent Advances in High Resilience (HR) Foam Technologies

Abstract: C igarette-induced smouldering of flexible polyurethane foam in upholstered furniture applications has long been recognised as a particular hazard to human life and property. Over the years, the furniture industry has taken steps to solve the problem via specific furniture design, careful selection of components such as cover fabrics, the use of barrier layers between foam and fabric, post-treatment of the foam, etc. All these steps have, to varying extents, alleviated the situation but, because the tendency of flexible polyurethane foam towards smouldering has been considered inalterable, they did not solve the problem itself. BP Chemicals Limited has developed a highly flexible polyurethane foam technology, hereafter abbreviated &dquo;HRS-II,&dquo; which will not sustain cigaretteinduced smouldering and which allows the requirements of U.K. furniture regulations (British Standards 5852, Part I) [1,2] to be met in combination with a most comprehensive selection of cover materials.

New polyols for urethane modified isocyanurate foams

Abstract: In the current climate of difficult economic times, o e key to success in any industry is to lower one’s manufacturing cost. Thus, a considerable amount of interest by the urethane foam industry has been directed toward the use of the inexpensive polyester polyols. Increasing the amount of polyester polyols used in a formulation decreases the direct material cost of a urethane foam. Unfortunately, due to the poor compatibility of polyester polyols with the other components of the B side, the maximum level of the polyester polyols that has been used has been limited to 40 to 50 percent of the total polyol weight of the B side [1]. Concurrent with the interest in polyester polyols, there has been a new direction taken by the urethane industry. This new trend is the manufacture of rigid polyurethane modified isocyanurate foams (PUIR). PUIR foams have an index of 1.5 to 3.5. The main advantage of PUIR foams are [2]:

Improved Rim Processing with Silicone Internal Mold Release Technology

Abstract: Utilisation d'agents de demoulage interne, dont le Dow Carning Q2-7119 pour le moulage reactif de caoutchouc d'urethanne

Is it Really Necessary to Use an Auxiliary Blowing Agent in the Production of Flexible Slabstock Polyurethane Foams? First Approach to Foams Expanded with Water Only.

Abstract: En modifiant la structure des polyols on peut tout en gardant la meme densite de mousse augmenter ou diminuer la durete de la mousse

Methods of Improving Refrigerant 11 Compatibility in Isocyanurate Systems Containing Waste Stream Aromatic Polyesters

Abstract: are perlite, fiberglass, EPS (expanded polystyrene) and various composites including polyurethane/ perlite and polyurethane/ fiberglass. Projections [1] for 1985 indicate that total U.S. consumption should reach over 3.3 billion board feet with average annual growth of about 3 percent from now through 1985. Although polyisocyanurate (PIR) boards currently comprise only a small (~3.5 percent) portion of the total roofing insulation being used, it has, by far, the highest (’V15 percent) projected annual growth rate. In order for PIR boards to remain cost competitive with the other available insulation materials, the availability and cost of the required raw materials are critical. The development and use of polyols based on waste stream aromatic polyesters [2] and, more recently, from polyesters reclaimed from bottles, film scrap, etc., have provided the industry with an inexpensive source of such materials. These polyols, however, suffer the disadvantage of incompatibility with Refrigerant 11, the fluorocarbon blowing agent commonly used in the production of PIR foams. This problem can be partially overcome by using the aromatic polyester polyol in combination with another polyol, the use of compatibilizing agents or by adding the fluorocarbon to the isocyanate. Since most lamination producers are not set-up to blend the fluorocarbon and the isocyanate, this option is the least desirable. The objective of this paper is to describe the effect of various compatibilizing agents, such as methylene chloride, methylpyrrolidone and a compatibilizing surfactant on the physical and flammability characteristics of isocyanurate foams based

Cell Structure Deformation of High Resilient Polyurethane Foam by Scanning Electron Microscopy

Abstract: a high resilient polyurethane (HR PU) foam are important performance requirements, among other processing and property requirements, to be designed into the urethane chemistry. An understanding of the deformation and modes of failure of cell structure in the open cell flexible urethane foam would provide useful information for urethane molecular design. The objective of this study is to determine directly by the use of a tensile stage in a scanning electron microscope, cell structure deformation modes in HR PU foams while under loading. Scanning electron microscopy [1-4] has been used in the determination of cellular structure in plastic foams. Because of the planar nature of the SEM

Fire test comparison of a mini-compartment corner test to a full scale enclosed room fire test

Abstract: m he Combustibility Sections of the various Model Building Codes are intended to promote life safety in fire situations. The references in the codes pertaining to construction insulation have greatly affected the composition of the rigid foam insulations and composites in use today. A variety of test methods have been developed to assess the combustibility of insulation materials such as rigid urethane foams. These tests explore many aspects of material responses, combustion characteristics, or the performance of a composite or assembly in a particular fire scenario. Because of the complex nature of fires, the members of the Rigid Urethane Foam Industry, both individually and through the SPI have emphasized the need for full scale testing to obtain realistic fire performance information. The (8 x 12 ft.) Enclosed Room Fire Test [1, 2] is a widely used test of this nature. It is generally referred to as either a room cor-

The Effect of Surfactant Properties on a Rigid Foam System

Abstract: Surfactants required for rigid, isocyanate-based foam formulations appear to fill at least two roles. The first role is the stabilization of the rising foam. Thus, when gas is generated via vaporization of the blowing agent, the liquid formulation will boil rather than foam unless the proper surfactant is present. As the foam rises the surfactant must stabilize the foam until enough polymerization takes place that it becomes self supporting and the cell walls are resistant to opening. A second role of the surfactant is the dispersion and emulsification of the reactants. If the reactants form multiple phases, then the reaction rate and final foam chemistry are dependent upon ease of emulsification during mixing. Generally a silicone surfactant is selected for a particular foam formulation by trial and error. The manufacturers of surfactants often classify them only in terms of their use in flexible, or rigid foams, etc. but methods that systematically compare surfactants have not generally been used. Kanner, et al. [1], has reported that both simple foaming tests in liquid polyols and water and the spread of monolayers of surfactant on water have a correlation with the initial stages of urethane foaming. These tests however were not able to predict whether the surfactant could prevent premature collapse of the flexible foams.

Titanate Coupling Agents—1983 Urethane Applications

Abstract: P revious SPI Urethane/Titanate papers [1,2] have discl sed that: organotitanates of the types invented by the authors provide a range of catalytic and retardation effects dependent upon organic ligand functionality; no significant NCO depletion effects were exhibited in the RRIM system studied; the performance of titanate surface modified Wollastonite was shown to provide RRIM impact properties and other physical properties equal to or superior to comparable uncoated/silanized fiberglass RRIM systems when studied at the 40% level in hydroxyl component; fiberglass physical property performance in RRIM was substantially enhanced; RRIM system viscosity was reduced; Tg of Poly BD based urethanes was increased by up to 100 °C; and particulate functionality was enhanced significantly-for example, Zeolite efficiency improved threefold. The cited papers also explained that titanium derived coupling agents act as molecular bridges at the interface between two substrates (usually, but not limited to, an inorganic filler and an organic polymer matrix) by reacting with substrate surface protons resulting in the formation of matrix compatible/reactive, organic monomolecular layers on the substrate. The 1982 paper further claimed that titanates may act in both unfilled and filled NCO/polyol urethane systems as catalysts according to a polyol alcholoysis/NCO alkylation mechanism. This (1983) paper will explore titanate applications further, according to the following outline:

"Bimetallic" Bow of Rigid Urethane Foam Composites:

Abstract: Les defauts de courbure de panneaux de refrigerateurs et congelateurs peuvent provenir d'une post expansion due a un enlevement trop premature du moule ou aussi des differences de coefficient de dilatation thermique lineaire des divers materiaux. Etude de panneaux composites ABS/polyurethanne alveolaire/acier