Phenolic foam thermal insulation

Steel Deck Corrosion under Phenolic Roof Insulation. Phenolic foam roof insulation (PFRI) was hailed as the next panacea of roofing in the 1980s, as it had all the desired qualities of ideal roof insulation. It exhibited exceptional insulation with no thermal drift, great dimensional stability and easily passed fire resistance tests [1]. However, severe steel deck corrosion was observed as soon as three years after commercial PFRI was installed on some steel decks. 

A variety of cellular plastics exists for use as thermal insulation as basic materials and products, or as thermal insulation systems in combination with other materials (see Foamed PLASTICS). Polystyrenes, polyisocyanurates (which include polyurethanes), and phenolics are most commonly available for general use, however, there is increasing use of other types including p olye thylene s, polyimides, melamines, and poly (vinyl chlorides) for specific applications. 

Phenol-formaldehyde (PF) was the first fully synthetic macromolecular material ( Bakelite , 1907). In a slightly precured condition and provided with fillers, it is, as a moulding powder, available for processing into end-use articles such as bulb fittings, switch housings, coils, laminated wood and foam for thermal insulation. 

Multiple layers of low conductivity phenolic foam insulation and small temperature differences between the primary coolant and the ambient minimized the heat loss from the primary loop to the ambient. Also, the heat addition to this loop was minimized by using a recirculation pump with an extremely low heat dissipation rate, which was calculated from the pump curves supplied by the manufacturer. With the pump heat dissipation and the ambient heat loss being small fractions of the secondary loop duty, the test section heat load was relatively insensitive to these losses and gains. Local heat transfer coefficients were therefore measured accurately in small increments for the entire saturated vapor-liquid region. Additional details of this thermal amplification technique are provided in the paper by Garimella and Bandhauer [32]. 

The test methods mostly follow British Standards, but some are more closely related to the ISO tests. Care must be taken to ensure that the correct sample size is u.sed. The determination of water absorption by diffusion is based on the Swiss Standard SIA 279 Part 5.07 [13] (see Section 2.6 below). Similarly the properties of extruded board are specified in BS 3837, Part 2, 1990 [14]. BS 3927, 1986 [15], specifies rigid phenolic foam for thermal insulation in the form of slabs and profiled sections. The material is classified as types A. B. and C. which differ principally in thermal conductivity, water vapor permeability and apparent water absorption. Thermal conductivity is measured by methods described in BS 4370, Part 2, Method 7 [16] or Appendix B of BS 874 [17]. ... 

Rigid foams tend to be closed cell in nature, and this characteristic is necessary for some of the typical application areas such as thermal insulation and floatation aids. Some rigid foams do exist however with an open cell structure such as the phenol-fonnaldehyde-based horticultural and floral foams. 

BS 5927. Rigid phenolic foam (PF) for thermal insulation in the form of slabs and profiled sections. 1986. 

PhenoKc foam is a light weight foam created from phenolic resins. It is used in a large range of applications, such as flower foam blocks, building thermal insulation, fire protection, damping, and civil engineering in a wide variety of shapes blocks, sheets, and sprayed foams. 

THERMAL INSULATION FROM PHENOLIC FOAM PLASTICS FOR PIPELINES. 

FOAMED PHENOL-FORMALDEHYDE /POROFEN/ WITH CLOSED PORES USED FOR THERMAL INSULATION. 

Phenolic resin foam is an interesting material for the cellular insulation industry because of its high temperature resistance, fire resistance, and very low smoke generation [16]. The aqueous resole is crosslinked in the presence of a surfactant and a low boiling liquid, that volatizes during the increase ofviscosity or plasticity of the mixture. The surfectant is necessary to develop a uniform fine cellular foam stracture [1,6], Carbonization of phenolic foams yields carbon foams with an excellent thermal resistance, that are applied as high temperature insulation materials for the production of filters for corrosive agents and catalyst supports [1]. 

Such safety considerations have led to an increase in the number of specifiers requiring phenolic foam insulation. Although this is a cellular plastic, it has good fire performance, exhibits low flame spread, extremely low smoke emission and is a very efficient thermal insulant. 

Polyphenols. Another increasingly important example of the chemical stabilization process is the production of phenolic foams (54-57) by cross-linking polyphenols (resoles and novolacs) (see Phenolic Resins). The principal features of phenolic foams are low flammability, solvent resistance, and excellent dimensional stability over a wide temperature range (54), so that they are good thermal-insulating materials. 

To prepare thermal insulating materials, Carvalho et al. (2003) prepared phenolic and lignophenolic (lignin-phenol-formaldehyde) foams and determined their thermal conductivities 0.057 W m K (density of 0.12 g cm ) for phenolic foam and 0.072 W m" K" (density of 0.45 g cm ) for lignophenolic foam. Tondi et al. (2009) prepared tannin-based rigid foams with thermal conductivity values between 0.024 and 0.030 W m K" for densities between 0.08 and 0.12 g cm", respectively. 

Foams of phenol formaldehyde resins can be made from a dispersion of a volatile diluent (isopropyl ether dispersed with the aid of a surfactant) in an aqueous solution of an incomplete phenol-formaldehyde reaction product [46]. Addition of an acid catalyst such as hydrochloric or sulfuric acid causes further condensation of phenol and formaldehyde to give a dimensionally stable, network structure. At the same time the heat of reaction volatilizes the diluent, yielding a foam. The foaming can be done in place. Phenolic foams are used as heat-stable, flame-retardant, thermal insulation. 

Phenol—formaldehyde resins are used as mol ding compounds (see Phenolic resins). Their thermal and electrical properties allow use in electrical, automotive, and kitchen parts. Other uses for phenol—formaldehyde resins include phenoHc foam insulation, foundry mold binders, decorative and industrial laminates, and binders for insulating materials. 

Table 26.1. Overview of insulation materials sorted by their ambient condition thermal conductivities conventional (red) and superinsulation materials and components (turquoise) can be classified by their respective thermal conductivity values. Phenolic and polyurethane foams mark a transition area between those two families (pink)...

Mineral fillers and mineral fibers also increase temperature resistance. Phenolic resin-bound textile non-wovens exhibit excellent properties regarding changing climatic conditions, aging behavior, and thermal resistance compared to other insulation materials (PUR, PS foams, crosslinked PE). 

Table 10.1 Thermal conductivity of phenol formaldehyde insulation foam. By permission of Kooltherm Ltd...

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