Literature

Abstracts

Proceedings of the Polyurethane Foam Association Technical Program, Arlington, VA, May 10, 2001

The Evolution of Silicone Surfactant and Applications, Lee Lawler, OSI Industries, A Crompton Business, Proceedings of the Technical Program of the Polyurethane Foam Association Meeting, Arlington, VA, May 10, 2001.

This paper begins with a timeline of the key events influencing the development of silicone surfactants for use in the manufacture of flexible polyurethane foam. It begins in 1950 with the development of tin catalysts for use in the "one -shot" process and ends with the present work aimed at developing optimum products for use with carbon dioxide blown systems. The paper then goes on to describe the effects of surface tension, and the effect of chemical structure on surfactant properties. The author shows the effect of various alkoxy-pendant groups on hydrophilicity, potency, and processing latitude of the resulting surfactants, followed by a summary of the generalized characteristics of "hydrolyzable" alkoxy-pendant surfactants and "non-hydrolyzable" alkoxy-pendant surfactants.

The description of conventional surfactants for the production of flexible polyurethane foams is followed by a timeline of key events for development of "flame retardant" silicone surfactants, and a summary of the current state of the art for these products.

Fire Safety Activity Update on Upholstered Furniture and Mattresses, Dale Ray, U.S. Consumer Products Safety Commission, Proceedings of the Technical Program of the Polyurethane Foam Association Meeting, Arlington, VA, May 10, 2001.

This paper presents an overview of the U.S. Consumer Products Safety Commission (CPSC) activity regarding upholstered furniture. The 1998 national fire loss estimates for upholstered furniture along with upholstered furniture fire deaths caused by cigarette ignitions, and upholstered furniture fire deaths caused by small open flame ignitions for the period 1980-1998 are presented. The results of the CPSC interlab flammability testing, and the CPSC staff Draft Standard are also shown.

The paper discusses an evaluation of flame retardant chemicals, and reviews NAS conclusions, Polyurethane Foam Industry voluntary standards activity, The Polyurethane Foam Industry petition issues, and the CPSC Briefing Package.

An overview of CPSC activity in the mattress and bedding area is also presented. Included are the 1997 fire loss estimates for mattresses and bedding, and a schedule for mattress and bedding test development.

Formulating Technology for Viscoelastic Slabstock Foam, S. Hagar, R. Skorpenske, Bayer Corporation, Proceedings of the Technical Program of the Polyurethane Foam Association Meeting, Arlington, VA, May 10, 2001.

This paper describes the development of a new and improved polyol for the production of viscoelastic foam. Viscoelastic slabstock foam, also referred to as slow recovery and memory foam, is characterized by the following distinctive performance characteristics: low resilience, shape conformance, vibration and sound dampening, and energy and shock absorption. These unusual traits make viscoelastic foams of interest in many diverse applications; the largest of which include pillows and mattresses. Many different foam grades are produced commercially to meet the performance requirements of these applications.

The production of viscoelastic foams requires different chemical approaches than conventional foam. Most formulations include a high hydroxy polyol and one of several different isocyanates including MDI, 80/20 TDI, or 65/35 TDI. In general, processing and formulating latitudes are narrower than conventional slabstock foam as a result of the high hydroxy polyols and the low isocyanate indices used for their preparation. As a result, specialty silicones and/or cell opening polyols are sometimes used along with other additives to facilitate cell opening and impart special performance traits such as a good hand feel.

In spite of the formulating advances that have been made, viscoelastic foams still provide a significant challenge to foam producers. In addition to narrow processing latitude, there are a number of other common deficiencies that can be encountered. These include high resilience, temperature sensitivity, permanent sets, changes with age /use, and poor hand/feel.

To address these processing and performance limitations, Bayer has carried out systematic design and optimization studies to achieve improved polyol and formulating technology. These studies investigated and optimized the structure of the viscoelastic polyol including hydroxyl number, functionality and composition. Also investigated were formulation variables for controlling the grade (firmness and density) and performance features of the foam. These variables included addition of conventional polyol and polymer polyol, DP-1022 foam modifier and TDI index. A key goal of the optimization was to provide a broad processing window near 100 index. In addition, regression models were developed which related the key performance properties of viscoelastic foams to the formulating variables.

Based on these evaluations, a new viscoelastic polyol, SOFTCEL® VE-1000 was developed which exhibited broad processing and formulating flexibility in full scale Maxfoam machine evaluations. The polyol is designed for use with commodity slab polyols, polymer polyols, foam modifiers, 80/20 TDI and other standard slabstock foam intermediates Formulating technology for use of VE-1000 with MDI and specialty intermediates is currently under development.

Foams produced with this technology exhibit a high level of body conformance, low temperature sensitivity, good compression sets and fine cell structure. This paper also describes more viscoelastic property comparisons on a high density pillow made with VE-1000 and one purchased commercially. These show the influence of temperature and humidity on the compression-time profile and of temperature on stress relaxation rate. Pressure point data is also presented showing favorable performance of the VE-1000 foam.

Behaviour of Expandable Graphite as a Flame Retardant in Flexible Polyurethane Foam, Vijay J. Bhagat, R & D Center, Cleanline Products Pvt., Ltd, Pune India, Proceedings of the Technical Program of the Polyurethane Foam Association, Arlington, VA, May 10, 2001.

There is a growing trend in the polyurethane industry to substitute non-halogenated flame retardants for the more commonly used halogenated ones, in order to reduce or eliminate some of the volatile toxic by-products of combustion, such as carbon monoxide, formed by the latter. This paper addresses the proper selection of various grades of expandable graphite for flame retarding flexible polyurethane slabstock foams. The author examines the effect of purity of the graphite flake, particle size of the flake and the expansion properties of the expandable graphite for achieving optimum results. .

Expandable graphite is manufactured by the oxidation of natural graphite flake in sulphuric acid. When expandable graphite is exposed to heat, it expands to more than 100 times its original volume, and covers the entire burning surface of the foam with a "worm" like structure of expanded graphite. The char, formed by the expanded graphite, acts as an insulating agent and dramatically reduces the heat release, mass loss, smoke generation and toxic gas emission of the foam. Only low temperature expandable graphite can be used as a flame retardant for flexible polyurethane foam. The expansion must occur at a "critical temperature" where decomposition, exothermal reaction and ignition occur spontaneously. This critical temperature, for flexible polyurethane foam, has been determined to be between 300-500oC.

In 1971, Frnaclxzek and co-workers at Dow, first investigated the use of expandable graphite as a flame retardant for flexible slabstock foam. This early work indicated that the physical properties of the foam were deteriorated as a result of the high quantities of expandable graphite required to achieve the desired degree of flame retardance. The current investigators evaluated the effect of various concentrations of expandable graphite in the formulation, various grades of graphite with expansion temperatures between 200-1000oC at a fixed concentration of 35%, and particle size of the expandable graphite. The effects of these variables on flame retardance as measured by the Oxygen Index test and a "torch test" are provided.

The author concludes that an optimum grade of expandable graphite can be selected to produce flexible slabstock foam with improved flame retardant properties. Key parameters of the expandable graphite, which must be controlled, are expansion temperature of the graphite, pH, and contaminants such as iron, nickel, copper, etc.

The Trinity Project: Not Linking Exposure to Health Effects, Steven P. Levine, Professor, University of Michigan School of Public Health, Proceedings of the Technical Program of the Polyurethane Foam Association, Arlington, VA, May 10, 2001.

The Trinity American Corporation's facility in Glenola, NC, was ordered to cease foaming operations by the State Health Director for the State of North Carolina on September 3. 1997. The American Chemistry Council's (ACC) Diisocyanates Panel (Panel), through their contractors(Levine and Redinger) collected documents and analytical information to see if exposure assessment and health effects demonstrated a toluene diisocyanate (TDI) hazard to the community that warranted plant closure.

The Panel concluded that the data did not support plant closure for the following reasons:

  1. Ambient air concentrations of TDI at the Trinity fence line did not exceed State of North Carolina Acceptable Ambient Levels (AAL).
  2. Dispersion modeling conducted by the State of North Carolina and Roy F. Weston, Inc., to determine TDI concentrations from Trinity emissions, did not reveal violation of the State of North Carolina AAL for TDI.
  3. Biological monitoring and clinical tests conducted of residents living near Trinity do not prove that TDI emissions from Trinity 1) were above the AAL, 2) have a dose- response relationship with bio-markers, or 3) were the cause of adverse health effects.
  4. The decision to close Trinity because of potential TDI exposure to residents was made on incomplete information, and was not based on sound science. Alternatives were not adequately considered.

The Panel also concluded that these results do not prove that the Government was wrong. It only proves that the government did not have the data to demonstrate a scientific or legal basis for its actions. A recommendation was also made for companies to be pro-active and take preventative action through the American Chemistry Council's Responsible Care system.

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