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Redux (adhesive)
Encyclopedia
Redux is the generic name of a family of phenyl–formaldehyde
/polyvinyl
–formal adhesives developed by Aero Research Limited
(ARL) at Duxford
, UK, in the 1940s, subsequently produced by Ciba (ARL). The brand name is now used for a range of epoxy
adhesives manufactured by Hexcel
. The name is a contraction of REsearch at DUXford.
and George Newell in 1941 for use in the aircraft industry, the adhesive is used for the bonding of metal-to-metal and metal-to-wood structures. The adhesive system comprises a liquid adhesive and a powder hardener.
The first formulation available was Redux Liquid E/Formvar, comprising an adhesive (Redux Liquid E) and a hardener (Formvar), and after its initial non-aviation related application of bonding clutch
plates on Churchill
and Cromwell
tanks, it was used by de Havilland
from 1943
to the early 1960s, on, among other aircraft, the Hornet
, the Comet
and the derived Nimrod, and the Dove
, Heron
and Trident
. It was also used by Vickers
on the Viking
and by Chance Vought
on the F7U Cutlass
.
Typically, Redux would be used to affix stiffening stringer
s and doublers to wing
and fuselage
panels, the resulting panel being both stronger and lighter than a rivet
ed structure. In the case of the Hornet it was used to join the aluminium
lower-wing skin to the wooden upper wing structure, and in the fabrication of the aluminium/wood main wing spar
, both forms of composite
construction made possible by the advent of Redux.
After initially supplying de Havilland only, ARL subsequently produced a refined form of Redux Liquid E/Formvar using a new liquid component known as Redux K6, and a finer-grade (smaller particle
-size) powder, and this was later made generally available to the wider aircraft industry as Redux 775/Powder 775, so-named because it was sold for aircraft use to specification DTD 775*. Available for general non-aerospace
use it was called Redux Liquid K6/Powder C.
Redux 775/Powder 775 was joined in 1954
by the subsequent Redux Film 775/Powder 775 system, used from 1962
by de Havilland (later Hawker Siddeley and subsequently British Aerospace
) on the DH.125
and DH.146
. Other users included Bristol
(on the Britannia
), SAAB
(on the Lansen
& Draken), Fokker
(on the F.27
), Sud Aviation
(on the Alouette II/III), Breguet
and Fairchild, the film-form having the advantage of greater gap-filling ability with no loss of strength over Redux 775/Powder 775, allowing for wider tolerances in component-fit, as well as easier handling and use.
Other Redux adhesives available included Redux 318, a fire- and heat-resistant Nomex
polyamide paper covered on one side with a tacky film of dry, high-strength adhesive, and Redux 322, a high-strength structural adhesive flexible film, both being used in the British Aircraft Corporation/Sud Aviation Concorde
supersonic airliner.
Currently, Redux 420 and Redux 501 are now marketed as Araldite
420 and Araldite 501.
* DTD = Directorate of Technical Development
process is by condensation
and a typical figure for Redux 775/Powder 775 is 30 minutes at 145 °C (293 °F) under a pressure of 100 lbf/in2 (690 kPa
). This is not critical and variations in curing-time and/or temperature may be used to increase shear
and creep
strength at temperatures above 60 °C (140 °F). Extending the curing-cycle gives benefits in fatigue
strength at some cost in the room-temperature peel strength, the practical limit for aluminium alloy
s being approx 170 °C (338 °F) for one hour, due to the possibility of affecting the alloy's mechanical properties.
Strength of bonds to materials other than aluminium:
Tensile
shear of 0.5 inch (12.7 mm) lap joint
s at room temperature:
1 = HK31A-H24
2 = ICI
Titanium 130
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
/polyvinyl
Polyvinyl
Polyvinyl is a group of polymers derived from vinyl monomers.Polyvinyl may also refer to:* Polyvinyl chloride* Polyvinyl acetate* Polyvinyl alcohol* Polyvinyl Record Co., an independent record label...
–formal adhesives developed by Aero Research Limited
Aero Research Limited
Aero Research Limited was a British company that pioneered several new adhesives, intended initially for the aeronautical industry.Formed in 1934 by Norman de Bruyne at Duxford, Cambridgeshire from an earlier company of his, the Cambridgeshire Aeroplane Construction Company, ARL started a...
(ARL) at Duxford
Duxford
Duxford is a village in Cambridgeshire, England, some ten miles south of Cambridge.-History:The village formed on the banks of the River Cam, a little below its emergence from the hills of north Essex...
, UK, in the 1940s, subsequently produced by Ciba (ARL). The brand name is now used for a range of epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
adhesives manufactured by Hexcel
Hexcel
Hexcel is a materials company incorporated in Delaware and headquartered in Stamford, Connecticut that manufactures advanced composite materials and structural parts...
. The name is a contraction of REsearch at DUXford.
History
Devised at ARL by Dr. Norman de BruyneNorman de Bruyne
Norman Adrian de Bruyne FRS was born in Punta Arenas Chile on November 8, 1904, baptized on March 19, 1905 at the Anglican Church St. James Church, by the Rev. Edwin Aspinall. His father was Dutch and his mother English. He grew up in England, studied science at the University of Cambridge and...
and George Newell in 1941 for use in the aircraft industry, the adhesive is used for the bonding of metal-to-metal and metal-to-wood structures. The adhesive system comprises a liquid adhesive and a powder hardener.
The first formulation available was Redux Liquid E/Formvar, comprising an adhesive (Redux Liquid E) and a hardener (Formvar), and after its initial non-aviation related application of bonding clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
plates on Churchill
Churchill tank
The Tank, Infantry, Mk IV was a heavy British infantry tank used in the Second World War, best known for its heavy armour, large longitudinal chassis with all-around tracks with multiple bogies, and its use as the basis of many specialist vehicles. It was one of the heaviest Allied tanks of the war...
and Cromwell
Cromwell tank
Tank, Cruiser, Mk VIII, Cromwell ,The designation as the eighth Cruiser tank design, its name given for ease of reference and its General Staff specification number respectively and the related Centaur tank, were one of the most successful series of cruiser tanks fielded by Britain in the Second...
tanks, it was used by de Havilland
De Havilland
The de Havilland Aircraft Company was a British aviation manufacturer founded in 1920 when Airco, of which Geoffrey de Havilland had been chief designer, was sold to BSA by the owner George Holt Thomas. De Havilland then set up a company under his name in September of that year at Stag Lane...
from 1943
1943 in aviation
This is a list of aviation-related events from 1943:-Events:* Watanabe Iron Works transfers its aircraft manufacturing business to a new subsidiary, the Kyushu Airplane Company Ltd.-January:...
to the early 1960s, on, among other aircraft, the Hornet
De Havilland Hornet
The de Havilland DH.103 Hornet was a piston engine fighter that further exploited the wooden construction techniques pioneered by de Havilland's classic Mosquito. Entering service at the end of the Second World War, the Hornet equipped postwar RAF Fighter Command day fighter units in the UK and was...
, the Comet
De Havilland Comet
The de Havilland DH 106 Comet was the world's first commercial jet airliner to reach production. Developed and manufactured by de Havilland at the Hatfield, Hertfordshire, United Kingdom headquarters, it first flew in 1949 and was a landmark in aeronautical design...
and the derived Nimrod, and the Dove
De Havilland Dove
The de Havilland DH.104 Dove was a British monoplane short-haul airliner from de Havilland, the successor to the biplane de Havilland Dragon Rapide and was one of Britain's most successful post-war civil designs...
, Heron
De Havilland Heron
The de Havilland DH.114 Heron was a small, propeller-driven British airliner that first flew on 10 May 1950. It was a development of the twin-engine de Havilland Dove, with a stretched fuselage and two more engines. It was designed as a rugged, conventional low-wing monoplane with tricycle...
and Trident
Hawker Siddeley Trident
The Hawker Siddeley HS 121 Trident was a British short/medium-range three-engined jet airliner designed by de Havilland and built by Hawker Siddeley in the 1960s and 1970s...
. It was also used by Vickers
Vickers Armstrong
Vickers-Armstrongs Limited was a British engineering conglomerate formed by the merger of the assets of Vickers Limited and Sir W G Armstrong Whitworth & Company in 1927...
on the Viking
Vickers VC.1 Viking
The Vickers VC.1 Viking was a British twin-engine short-range airliner derived from the Vickers Wellington bomber and built by Vickers Armstrongs Limited at Brooklands near Weybridge in Surrey. In the aftermath of the Second World War, the Viking was an important airliner with British airlines...
and by Chance Vought
Vought
Vought is the name of several related aerospace firms. These have included, in the past, Lewis and Vought Corporation, Chance Vought, Vought Sikorsky, LTV Aerospace , Vought Aircraft Companies, and the current Vought Aircraft Industries. The first incarnation of Vought was established by Chance M...
on the F7U Cutlass
F7U Cutlass
The Vought F7U Cutlass was a United States Navy carrier-based jet fighter and fighter-bomber of the early Cold War era. It was a highly unusual, semi-tailless design, allegedly based on aerodynamic data and plans captured from the German Arado company at the end of World War II, though Vought...
.
Typically, Redux would be used to affix stiffening stringer
Longeron
In aircraft construction, a longeron or stringer or stiffener is a thin strip of wood, metal or carbon fiber, to which the skin of the aircraft is fastened. In the fuselage, longerons are attached to formers and run the longitudinal direction of the aircraft...
s and doublers to wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
and fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
panels, the resulting panel being both stronger and lighter than a rivet
Rivet
A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...
ed structure. In the case of the Hornet it was used to join the aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
lower-wing skin to the wooden upper wing structure, and in the fabrication of the aluminium/wood main wing spar
Spar (aviation)
In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings whilst on the ground...
, both forms of composite
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
construction made possible by the advent of Redux.
After initially supplying de Havilland only, ARL subsequently produced a refined form of Redux Liquid E/Formvar using a new liquid component known as Redux K6, and a finer-grade (smaller particle
Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact . The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations...
-size) powder, and this was later made generally available to the wider aircraft industry as Redux 775/Powder 775, so-named because it was sold for aircraft use to specification DTD 775*. Available for general non-aerospace
Aerospace
Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
use it was called Redux Liquid K6/Powder C.
Redux 775/Powder 775 was joined in 1954
1954 in aviation
This is a list of aviation-related events from 1954:-January:* January 10 – A de Havilland Comet 1, operating BOAC Flight 781, crashes into the Mediterranean Sea near Elba following fatigue failure, killing all 35 people aboard.-February:...
by the subsequent Redux Film 775/Powder 775 system, used from 1962
1962 in aviation
This is a list of aviation-related events from 1962:- Events :* Early 1962 – In Operation High Jump, the United States Navy McDonnell F4H-1 Phantom II fighter sets a number of world climb-to altitude records: 34.523 seconds to 3,000 meters , 48.787 seconds to 6,000 meters , 61.629 seconds to...
by de Havilland (later Hawker Siddeley and subsequently British Aerospace
British Aerospace
British Aerospace plc was a UK aircraft, munitions and defence-systems manufacturer. Its head office was in the Warwick House in the Farnborough Aerospace Centre in Farnborough, Hampshire...
) on the DH.125
British Aerospace BAe 125
The British Aerospace 125 is a twin-engined mid-size corporate jet, with newer variants now marketed as the Hawker 800. It was known as the Hawker Siddeley HS.125 until 1977...
and DH.146
BAe 146
The British Aerospace 146 is a medium-sized commercial airliner formerly manufactured in the United Kingdom by British Aerospace, later part of BAE Systems. Production ran from 1983 until 2002. Manufacture of an improved version known as the Avro RJ began in 1992...
. Other users included Bristol
Bristol Aeroplane Company
The Bristol Aeroplane Company, originally the British and Colonial Aeroplane Company, was both one of the first and one of the most important British aviation companies, designing and manufacturing both airframes and aero engines...
(on the Britannia
Bristol Britannia
The Bristol Type 175 Britannia was a British medium-to-long-range airliner built by the Bristol Aeroplane Company in 1952 to fly across the British Empire...
), SAAB
Saab
Saab AB is a Swedish aerospace and defence company, founded in 1937. From 1947 to 1990 it was the parent company of automobile manufacturer Saab Automobile, and between 1968 and 1995 the company was in a merger with commercial vehicle manufacturer Scania, known as Saab-Scania.-History:"Svenska...
(on the Lansen
Saab Lansen
|-See also:-References:NotesBibliography* Erichs, Rolph et al. The Saab-Scania Story. Stockholm: Streiffert & Co., 1988. ISBN 91-7886-014-8....
& Draken), Fokker
Fokker
Fokker was a Dutch aircraft manufacturer named after its founder, Anthony Fokker. The company operated under several different names, starting out in 1912 in Schwerin, Germany, moving to the Netherlands in 1919....
(on the F.27
Fokker F27
The Fokker F27 Friendship is a turboprop airliner designed and built by the Dutch aircraft manufacturer Fokker.-Design and development:Design of the Fokker F27 started in the 1950s as a replacement to the successful Douglas DC-3 airliner...
), Sud Aviation
Sud Aviation
Sud-Aviation was a French state-owned aircraft manufacturer, originating from the merger of Sud-Est and Sud-Ouest on March 1, 1957...
(on the Alouette II/III), Breguet
Société Anonyme des Ateliers d'Aviation Louis Breguet
The Société des Ateliers d'Aviation Louis Bréguet also known as Breguet Aviation was a former French aircraft manufacturer. The company was set up in 1911 by aviation pioneer Louis Charles Breguet....
and Fairchild, the film-form having the advantage of greater gap-filling ability with no loss of strength over Redux 775/Powder 775, allowing for wider tolerances in component-fit, as well as easier handling and use.
Other Redux adhesives available included Redux 318, a fire- and heat-resistant Nomex
Nomex
Nomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...
polyamide paper covered on one side with a tacky film of dry, high-strength adhesive, and Redux 322, a high-strength structural adhesive flexible film, both being used in the British Aircraft Corporation/Sud Aviation Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...
supersonic airliner.
Currently, Redux 420 and Redux 501 are now marketed as Araldite
Araldite
Araldite is a registered trademark of Huntsman Advanced Materials referring to their range of engineering and structural epoxy, acrylic, and polyurethane adhesives. The name was first used in 1946 for a two-part epoxy adhesive....
420 and Araldite 501.
Usage
To use Redux, a thin film of the liquid adhesive is applied to both mating surfaces and then dusted-with or dipped-in the powder hardener in an approximate ratio by weight of 1 part liquid to 2 parts hardener. The coated joints are then allowed to stand for not less than 30 minutes and not more than 72 hours before the components are brought together under elevated pressure and temperature. The curingCuring (chemistry)
Curing is a term in polymer chemistry and process engineering that refers to the toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation, electron beam or heat...
process is by condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
and a typical figure for Redux 775/Powder 775 is 30 minutes at 145 °C (293 °F) under a pressure of 100 lbf/in2 (690 kPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
). This is not critical and variations in curing-time and/or temperature may be used to increase shear
Shear strength
Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. A shear load is a force that tends to produce a sliding failure on a material along a plane that is...
and creep
Creep (deformation)
In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....
strength at temperatures above 60 °C (140 °F). Extending the curing-cycle gives benefits in fatigue
Fatigue (material)
'In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.Fatigue occurs...
strength at some cost in the room-temperature peel strength, the practical limit for aluminium alloy
Aluminium alloy
Aluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories...
s being approx 170 °C (338 °F) for one hour, due to the possibility of affecting the alloy's mechanical properties.
Performance (typical) Redux 775
- Lap shear strength at ambient temperature = 34.0 MPa (4,930 lbf/in2)
- Young's Modulus (E)Young's modulusYoung's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...
= 3.35 GPa (486,000 lbf/in2) - Shear modulus = 1.20 GPa (174,000 lbf/in2)
Strength of bonds to materials other than aluminium:
Tensile
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
shear of 0.5 inch (12.7 mm) lap joint
Lap joint
In woodworking or metal fitting, a lap joint is a technique for joining two pieces of material by overlapping them. A lap may be a full lap or half lap....
s at room temperature:
- Bright mild steel of thickness 0.0625 in (1.6 mm) - mean failing stress = 4,980 lbf/in2 (33.7 MPa, 3.50 kgfKilogram-forceA kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
/mm2)
- Stainless steelStainless steelIn metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
of thickness 0.048 in (1.2 mm) - mean failing stress = 5,600 lbf/in2 (38.6 MPa, 3.94 kgf/mm2)
- Magnesium alloyMagnesium alloyMagnesium alloys are mixtures of magnesium with other metals , often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys...
1 of thickness 0.063 in (1.6 mm) - mean failing stress = 3,210 lbf/in2 (22.1 MPa, 2.26 kgf/mm2)
- Commercially-pure titaniumTitaniumTitanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
2 of thickness 0.050 in (1.3 mm) - mean failing stress = 4,070 lbf/in2 (28.1 MPa, 2.86 kgf/mm2)
1 = HK31A-H24
2 = ICI
Imperial Chemical Industries
Imperial Chemical Industries was a British chemical company, taken over by AkzoNobel, a Dutch conglomerate, one of the largest chemical producers in the world. In its heyday, ICI was the largest manufacturing company in the British Empire, and commonly regarded as a "bellwether of the British...
Titanium 130