This article series about asbestos plastics & molded materials describes the history, manufacturing process & uses of asbestos plastics and molded materials such as asbestos reinforced handles, the Vanguard rocked nose cone, automobile parts & housings, electronic equipment (radar scanner), asbestos-filled Teflon, rocket motor parts, plastic drop tanks for the Hawker Sea Hawk, and hundreds of other products.
Page top photo: the asbestos-plastic drop tank for the Hawker Sea Hawk - Adapted from Rosato (1959) .
This articles series about the manufacture & use of asbestos-containing products includes detailed information on the production methods, asbestos content, and the identity and use of asbestos-containing materials.
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Depending on the country where plastic products were or are produced, the last-used-date for asbestos in plastic and resinous products varies, and technically the use of asbestos in plastics is currently legal.
See details
at ASBESTOS PRODUCTS BANNED vs PERMITTED U.S. 2023
Really? Does this mean that plastics necessarily do contain asbestos? Are those products dangerous?
Keep in mind that asbestos reinforced plastic products are not friable.
Unless you are grinding, chopping, sanding or sawing such materials they will not release meaningful amounts of asbestos fibers in normal use.
What follows here is a history of the use of asbesstos in reinforced and filled plastic products such as Bakelite and Noramite and other plastic materials from door handles to rocket nosecones - which you will read is a very large category.
The following text is Adapted from Rosato (1959) p. 142-177 [1] © 2013 InspectApedia.com
Introduction Asbestos reinforced and filled plastics have played an important role in the progress of the growth of industry since the turn of the century.
[Click to enlarge any image]
Since the development of phenol-formaldehyde resins in 1909, asbestos has been used in large quantities as a reinforcement, additive, and filler. There have been large quantities of short asbestos used in plastics such as those shown in Figure 9.1. Figure 9.2 shows the use of long fiber asbestos in asbestos-reinforced plastic rocket nose cones.
Figure 9.1. Typical difficult molding of long handle which has a hollow center to accommodate the electrical thermostat and wiring for Dominion skillet. - Courtesy Durez Plastics Div., Hooker Electro-Chemical Co.
Plastic materials are available which can be reinforced with such different fibers as asbestos, glass fiber, glass flakes, cotton, and Fiberfrax. These varied fibers provide for either different characteristics or in some cases, they can produce equivalent properties for specific applications.
The review in this chapter concerns only asbestos reinforced plastics.
Generally, when reviewing the subject of asbestos filled or reinforced plastics, phenolic resins or condensation type resins are discussed.
However, asbestos is used with such other resins as those listed in Table 9.1. Asbestos fibers, and in particular short fibers, are used in combinations with such other fibers (including long asbestos fibers) as polyester premix compounds.
Figure 9.3 below shows an automobile air conditioning housing which is made up of 55 per cent by weight of asbestos shorts or floats, 10 per cent chopped glass fiber, and 35 per cent polyester resin (with styrene). An extremely large quantity of asbestos fibers is used with these types of compounds but in most cases they are not identified as containing asbestos.
Plastics is one of the few billion dollar industries in the United States. It is one of the fastest growing industries with approximately a 300 per cent increase in production in the last ten years. The term "plastics" pertains to many different products.
Asbestos is used in many of them. In most applications it provides for meeting property requirements at low cost. As the plastic industry grows, more use of asbestos also develops both in thermoplastic and thermosetting resins.
SOME USES OF ASBESTOS IN PLASTIC COMPOSITIONS * TABLE 9.1 | ||
---|---|---|
Type of Asbestos-Containing Resin | Products & Applications Using This Asbestos Plastic Resin | Method of Fabrication of the Asbestos-Plastic Resin Product |
Rosin, with or without waxes,
gilsonite, creosote, shellac,
mineral oils, phenolic resins,
etc. |
Electrical insulations |
Hot molding, chilling |
Shellac, with rosin, creosote,
lime, etc. |
Electrical insulations and miscellaneous
uses |
Hot molding, with or without chilling |
Asphalts, tars and pitches, with chlorinated rubber, oils, solvents, etc. | Heat insulator coatings for metal pipes Parts for electrical and heat appliances | Brushing Drying, cold molding, using waterproofing molding |
Waxes (Montan, carnauba, etc.) with shellac, natural resins, gilsonite, modified rosins, mineral oils, etc. | Casting, coating, molding Box toe compositions Roofings |
Hot molding, chilling Hot molding, chilling Hot pressing, chilling |
Polymerizable oils | Joints, coating compositions, etc. | Brushing, trowelling, etc., curing |
Rubber or chlorinated rubber, with or without alkyd resins, etc. with or without organic filler and asbestos | Brake linings, clutch facings, valve discs,
gaskets, packings, etc. |
Hot molding, curing |
Phenolics, alone or with natural resins, rubber, inorganic filler (silica or mica) and asbestos, floats, long fiber, paper, yarn or fabric | Laminated boards |
Hot pressing Hot molding Hot molding Curing |
Molded heat resistant compositions Impregnated sheets, panels, or boards, gaskets, valve discs, etc. Asbestos fabric pressed as blocks Asbestos sheet as spacers for heat insulators Asbestos yarns, etc. for clutch facings, etc. |
Hot molding Laminated under heat and pressure Heat and pressure Hot pressing Hot molding |
|
Cellulose esters | Asbestos and cellulose esters used to in- crease strength and toughness of glycerol phtholate molding compounds |
|
Alkyd resins | Commutator rings Mica sheets Brake linings Door stripes, electrical spools, etc. Structural tiles Wood veneer panels Acid proof coatings |
Hot molding, chilling, curing Hot molding, chilling Cold molding, curing |
Phenolic varnishes | To increase adherence to coated surface,
to increase flexibility of undercoatings,
on metal surfaces, also used in
packings, putties and boards |
Varies depending on application |
Sheet protection for metal surfaces | Asbestos paper or sheet is connected to metal surface by phenolic resin and
then coated with the same material |
Curing by heat and pressure |
Typical uses of asbestos in plastic components - Rosato ca 1952
* A. B. Cummins, "Asbestos in Plastic Compositions" Modern Plastics.
Also see these pages from a 1950 catalog CAREY ROOFING CATALOG 1950 [PDF] describing asbestos plastic roof tiles.
Figure 9.2. Vanguard rocket nose cone is made of asbestos-phenolic material. It is subjected to aerodynamic heating, shock heat, and structural loads. The two-piece cone splits apart and drops off after the rocket leaves the atmosphere.
Typical commercial applications of asbestos-plastic materials include pulleys, casters, electrical circuit breakers, pipes, roller and sleeve bearings, metal bearing retainers, bushings, containers, ducts, and washing machine agitators.
Architects and engineers are developing more uses for asbestos based plastics too, inasmuch as they provide for increased resistance to fire and increase structural strength.
Information concerning the impact-porosity resistance of - plastics is applicable to doors or paneling, containers, boats (hull and floor), radomes, pressure bottles or tubes, plywood surface, rocket tubes, decorative panels, and ducts. Asbestos sheet products can be used on the surface, in the center or interleaved with other reinforcements to provide for high impact-porosity resistance.
The impact-porosity resistance of glass fabric or glass woven roving-polyester resin laminates is increased threefold when glass fabric is interleaved and/or surfaced with asbestos felts or papers. *
One of the more important and spectacular applications of asbestos reinforced plastics involves its use in missiles. Its insulation, ablation, and fine structural characteristics are all required in order that parts may function properly. Special asbestos-base plastics have been developed for use in direct rocket blasts which in turn have helped solve some of the high temperature problems.
Parts which are involved in the use of this type of product include nose cones, thermal - insulation barriers between propellant and steel motor bodies, rocket exhaust tubes, electrical conduits, aft insulators, deflector plates, rocket motor pressure plugs, turbine wheels, ducts, bulk head, fins, shrouds, and sliver traps. See Figures 9.8 through 9.10 inclusive.
* U.S. Navy, Bureau of Ships, Final Report, "The Use of Asbestos Fiber Materials in Glass Reinforced Plastic Laminates," Project 4860-Q-27 NS034-045 (Aug., 1957).
Figure 9.8. The Nike-Hercules sustainer motor contains asbestos phenolic insulation from the forward end to the exhaust end. - Courtesy The Thiokol Corporation. Click this or any image at InspectApedia to see a detailed, enlarged version.
Figure 9.9. A rocket motor tube tailpipe fabricated from asbestos phenolic plastic. -Courtesy The Bristol Aeroplane, Ltd.
Figure 9.10. Rocket motor body asbestos-plastic exhaust cone and ring.
Experimental tests using temperatures as high as 20,000°F have been conducted on various asbestos products. The materials are very poor conductors of heat and therefore help to solve some of the thermal problems.
During their exposure to extremely high temperatures for short periods of time their surfaces will oxidize or carbonize and produce a protective outer surface. Ablation or erosion occurs at a relatively slow rate.
Various parts have been made by such different techniques as compression molding, vacuum bag, autoclave, and transfer molding. These plastic parts can be easily mass produced. They have been used in modern development and production devices.
Figure 9.11. Asbestos base plastic 75-gal drop tank for the Hawker Sea Hawk. This tank is the first plastic drop tank in the world to have received full design approval.
The Bristol Aeroplane Company, Ltd., Filton, Bristol, England, has now received world wide acceptance of its asbestos-phenolic external auxiliary fuel tanks for aircraft.
This is the first world wide acceptance of any reinforced plastic part. These drop-tanks are shown in Figure 9.11.
They are required in large numbers and they form an important and costly item in modern air force inventory. The Bristol tank capacities are varied—SO, 100, 150, 200, 300, and 500 gal.
The Bristol tanks have been developed as a logical sequence to the company's work on plastics for primary structures.
The production techniques used, i.e., the molding of cylindrical fuselage sections by the autoclave process and the hydraulic press methods used for central sections and frames, have both been found to be readily adaptable to the manufacture of drop-tanks; the former process is used for the shell and the latter for the internal structure.
Newly developed [1950's - Ed.] high strength asbestos reinforced honeycomb is now in pilot-plant production. This new type of core material is the first of its kind where good physical properties at room and elevated temperatures are developed with asbestos. The presently available type utilizes a heat resistant phenolic resin.
Summary of preliminary properties of this type material identified as Hexcel Type XHRP % 6 —Asb.- 9.0 are shown in Table 9.11. A structural honeycomb utilizing silicone resin with asbestos reinforcement is in an early stage of development.
TABLE 9.11. ASBESTOS-PHENOLIC HONEYCOMB DATA * |
|||
Flexural Shear, psi |
Compressive, flatwise, psi |
||
Test Temperature | Ultimate Strength |
Modulus | Ultimate Strength |
Room | |||
L direction | 785 | 56,000 | 1,450 |
W direction | 435 | 28,800 | |
Tested at 500°F after 1/2 hr at 500°F |
|||
L direction | 475 | 30,800 | 1,145 |
W direction | 300 | 12,200 |
In the early 1950's plastics, including asbestos-reinforced plastics, was one of the few billion-dollar U.S. industries and was growing at a rate of 300% over the prior decade. This table lists the types of asbestos-reinforced resins used and the products made with asbestos-plastics as well as the method of asbestos-plastic manufacture.
Shear Specimens 3 in. by 8 in. simple support over 6 in. span, core 5/8 in. thick with Al. facings .091 in. thick.
Compression Specimens 2 in. by 2 in., 5/8 in. thick core, Al facings .091 in. thick.
* Hexel Co. was an information source for the table above, published by Rosato (seeReferences or Citations for more about the Hexel Corporation).
Original Table as-published: TABLE 9.11 ASBESTOS-PHENOLIC HONEYCOMB DATA [Image File] in Rosato, Op. Cit.
In 1951, a Delta Aircraft wing made of asbestos-phenolic laminate was displayed at the Exhibition of the Society of British Aircraft Constructors at Farnsborough, England. The Royal Aircraft Establishment, Ministry of Supply provided the exhibit in order to show progress on reinforced plastic aircraft parts
. The wing was approximately 8 ft from the fuselage with approximately an lift chord at the root. The shell of the wing continued around a leading edge and over the whole area back to the ailerons. There were no outer skin joints.
Fabrication of the wing was accomplished by two techniques; i.e., zero pressure and vacuum technique. In the zero pressure process, asbestos-phenolic sheet material (Durestos) was saturated with warm water producing a very soft sheet which could be hand rolled into simple curvatures.
By applying heat, these sheets would tend to delaminate and to produce low physical properties. To eliminate this problem, the softened sheets were treated with a water-soluble, coldsetting resorcinol resin. This resin penetrates the material and produces a solid compressed sheet.
During the cure, the resorcinol resin shrinks. Inasmuch as one side of the molded material will be exposed to the air, water is free to evaporate. This method of fabrication is a specialized art; it is not a standard procedure.
The vacuum process is a more desirable method of fabricating parts at low pressure, inasmuch as it provides for the elimination of condensation formed during the curing of the phenolic resin. The phenolic pre impregnated asbestos sheet material is manufactured so that suitable flow and resin conditions exist for this type of fabrication.
A male or female mold is used in conjunction with a vacuum bag which is generally made of rubber.
Two different basic internal structures were manufactured for the Delta wing construction. One was designed to provide compartments for various equipment. The other design involved internal fuel tanks. Asbestos-phenolic plastics were used in the manufacture of a high performance experimental wing for a glider by the Plastics Division of F. G. Miles, Ltd., Shoreham Airport, Sussex, England (1953).
The wing was of the high-performance type, being designed for laminar flow and having an aspect ratio of 18.
The wing had a 60 ft span, a 5 ft chord at the root, and weighed 155 lb. This plastic type of wing had been manufactured inasmuch as a high degree of accuracy was required in the contour of the wing. This accuracy permitted the production of a low cost item as compared with the conventional methods of manufacture.
See our complete list of asbestos-product producing companies found
at ASBESTOS PRODUCING COMPANIES & TRUSTS
Where we give details about each of the companies below and where we also identify any asbestos-settlement trusts associated with them
Editor's note:
The first truly synthetic plastic was created in 1907 by Leo Baekeland [Katz (1984)] from phenol formalde-
hyde and christened ‘bakelite’which is now known to degrade into acrylonitrile, butadiene, styrene,
cyanide and nitrous oxides which include irritants, suspected carcinogens and toxic respiratory system irritants [CAW (2003)
...
Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
(Feb 3, 2020) Tiiu Roiser said:
I have a question regarding old cooking pots, from probably the 1950's? I have several large and medium soup pots that have plastic-like handles. I have no idea what they may be made of.
The imprinted manufacturer says "Artistocrat". I've been reading about old bakelite. Might the handles be the same material and contain asbestos? I've been using these in the dishwasher.
The handles appear to be intact, but the black handles are disclouring to a dull gray.
Any idea what these might be? Is their use dangerous?
This Q&A were posted originally
Tiiu,
Some hard plastics used asbestos so it's certainly possible.
The handle on your Aristocrat saucepan looks like and probably is Bakelite, a molded, hard thermoplastic.
I'm doubt that there's a detectable airborne asbestos hazard if you're not grinding or chopping up the material.
It's not friable.
Aristocraft [sic] or Aristocrat was a West Bend brand of stainless steel cookware still widely-available used and sold ask "vintage cookware".
West Bend, a Wisconsin company, was founded in 1911, sold to Regal Ware, another Wisconsin company in 2001, subsequently re-sold to Focus Products Group, LLC in 2003. The Regal Ware West Bend product line brand is still available under from West Bend Housewares, sold under the product names Lifetime and Royal Queen.
Bakelite plastics, including cookware handles, was produced by chemist Leo Baekeland in 1907. To produce a hard, durable thermosetting plastic, Dr. Baekeland used a mixture of wood fibers, asbestos fibers and asbestos dust or shorts, along with formaldehyde. (Baekeland 1910)
Asbestos in Bakelite was included as both filler and reinforcement. The asbestos shorts (small asbestos fragments) in Bakelite helped prevent shrinkage as the heat-molded thermoset plastic cooled.
Bakelite was very widely used in an enormous range of products beyond cookware, including electrical components, handles ( & knobs on furnaces and other hot objects, radios, TVs, and other electrical applications) and other consumer goods, and parts used in vehicles and weapons, even rocket parts as we discuss above on this page.
As we said above, Bakelite, though it contains asbestos, is not friable, is considered of low toxicity, and is not a banned substance.
Watch out: similar hard plastic products produced using other formulations may contain asbestos too, such as forms of PVC (PolyVinyl Chloride) products, products using phenolic plastics and even some nylon plastic products.
[Click to enlarge any image]
Photo: Leo H. Baekeland, inventor of Bakelite, in 100 Years of Bakelite, the Material of 1000 Uses, Crespy et als 2008, cited below.
Illustration: table illustrating electrical test results performed by Baekeland on Bakelite of various compositions in Industrial & Engineering Chemistry 3, no. 12 (1911) cited below.
...
Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
On 2018-11-20 2 - by (mod) - When was asbestos last incorporated into a phenolic board?
Keith
Because the longer I work on this topic the more I find that there are countless thousands of products that use asbestos, I suggest that you could assume that asbestos was used or may have been used in plastic material such as phenolic boards (circuit boards?) until after the asbestos banned in the country where you live.
That date varies widely by country.
Asbestos was certainly used in phenolic plastics as we discuss here
Also see asbestos in phenolic products cited in:
On 2018-11-19 2 by Keith Chadwick
When was asbestos last incorporated into a phenolic board?
On 2018-09-02 - by (mod) - cones made of asbestos?
Clarifying: Rocket nose cones, aircraft or aircraft fuel tank nose cones.
On 2018-09-02 by Hitesh Jani
Applications of cones made of asbestos?
On 2017-06-21 - by (mod) - asbestos in trucks & other vehicles
Interesting question. I'll do some research.
In the meantime take a look at the firewall in the engine compartment and if you like use the page top or bottom contact link to send me photos of what you see
In ASBESTOS LIST of PRODUCTS you'll see listed uses of asbestos in tires, rubber products, and in insulating products.
Asbestos was and may remain in some talc or powder products used in the packing and handling of inntertubes used in car, truck, and bicycle tires.
See ASBESTOS in TALCUM POWDER
On 2017-06-21 by ayotteman@gmail.com
I have an early 1960's Peterbilt truck. Was wondering if there is any asbestos used in the cab for sound insulation etc?
On 2015-02-03 by J
Did semi truck inner tubes ever contain asbestos?
...
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