Composites news

COMPOSITES news New corrosion resistant

Tests show dramatic differences in weight loss in coated and uncoated honeycomb after exposure to salt spray (see illustration). After 30 days" exposure, for example, 2024 standard core loses on the order of 2500 mg of weight per square foot of foil surface area. T h e CR III core loses only 4. I mg when subjected to the same test.

aluminium honeycomb

A new aluminium honeycomb that offers high resistance to corrosion, even at elevated temperatures, has been introduced by Hexcel. Called CR IIl, the corrosion-resistant coating is applicable to 5052 and 5056 alloys as well as 2024. This makes corrosion resistant aluminium honeycomb avail able for the first time for many aerospace applications where 2024 alloys are used. This honeycomb does not corrode and it exhibits virtually no loss of strength after 30 day salt spray exposure tests. T h e effectiveness of the corrosion-proof coating is not reduced by long term exposure to temperatures of 350°F (177°C) or short term exposure to 450°F (232°C). Process advantages of the CR Ill system allow Hexcel to offer the new corrosion resistant 2024 core at the same price currently charged for standard 2024 aluminium haneycomb. CR III-coated 5052 and 5056 core will be available at no increase in cost over present corrosion resistant cores.

T h e CR III system is a clear, protective film which in.teracts with the aluminium surface to form a stable, tightly adherent bond. T h e coating is primarily an organo-metallic polymer type, which differs from the normal conversion type of corrosion coatings. T h e CR I I I protective film is placed on the foil prior to the node bond adhesive, assuring corrosion protection in the nodal area. CR III has no measurable weight difference when compared with standard, uncoated honeycomb core. T h e node bond adhesive and .the relationships of alloy condition, foil gauge, cell size, density, mechanical properties and tolerances remain unchanged from those established for the standard aluminium honeycomb core.

CR I I I is available in the full range of cell sizes, alloys, densities and tolerances offered with standard 5052, 5056 and 2024 aluminium honeycomb. It meets the requirements of the latest revision of military specification MIL-C-7438. Hexcel, 11711 Dublin Boulevard, Dublin, California 94566, USA

Adhesives for wood A bulletin has been published by the Princes Risborough Laboratory of the Building Research Establishment setting out the basic requirements. general characteristics, met'hods of use and overall properties of wood adhesives. This bulletin incorporates the most recent information on current types. Both natural and synthetic glues are covered; terms used in gluing work are explained in detail and each adhesive is classified and described. There are British Standard Specifications for expressing the durability of glues; these are explained and tabulated. T h e advantages and drawbacks of the various glues are compared and their setting processes described. The report, FPR Bulletin No 20, Fifth Edition, 'Requirements and properties of adhesives for wood', by R. A. G. Knight, revised by R. J. Newall, 197I, 14 pp, is available from Her Majesty's Stationery Office (Mail Orders), PO Box 569, London SE1. UK, price 40p net.

'Building with plastics'

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b

Aluminium honeycomb alter 30 days in 5% sodi.um chloride spray: material, 2024-T81 aluminium; 0"015 in foil gauge; 3/16in (4.76mm) cell size; density 3.5 Ib/[t ~ (56 kg/m~): (a) Hexcel's CR III: (b) bare honeycomb

COMPOSITES May 1972

Twenty-six case histories in an illustrated booklet entitled 'Building with plastics' show the valuable contribut:'on these versatile materials are making in the building industry. Intended primarily as a g u i d e to architects the book, produced by B P Chemicals International Limited. highlights building problems and shows how plastics can solve them. Particular reference is made to BP Chemicals' own research and development in this field. Many and varied applications of plastics are explained by means of photographs, line drawings and text. Applications of composite materials are cited in cladding (CRY and eveclad aluminium); flooring (Estercrete polyester cement and Dunlop Synthanite): parti,tioning (ArmaboardCellobond polyester resins on aluminium-framed flax board); and paving (Estercrete). Copies of the booklet are available fi'om BP Chemicals International Limited, Devonshire House, Piccadilly, London W I X 6AY, UK.

COMPOSITESnew Hercules carbon fibre price reductions From 1 January 1972 Hercules Incorporated will charge the following leduced prices for their three types of continuous carbon fibre. This is part of a continuing effort by Hercules to stimulate composites applications using large quantities of carbon fibre. HM O- 9 9 1 b 100- 9991b 1000-29991b 3000-49991b 50001bandover

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$215 $195 $165 190 170 140 180 160 133 170 153 126 150 135 112

All operating functions of the Advanced Composites Group, including fibre and prepreg manufacturing. structures fabrication, design, engineering support and sales are now situa,ted at Hercules Incorporated, PO Box 98, Magna. Utah 84044, USA

Hot press moulding of GRP T h e first of a new series of Process Guides - - "Hot press moulding fibreglass reinforced plastics' - - a 24-page booklet, has been published by Fibreglass Limited. This attractive booklet gives basic information on mass production m o u l d i n g techniques for GRP and is of particular interest to the designer in deciding when this process can be used to economic advantage and to the moulder contemplating a change to hot press moulding. T h e r e has been a rapid increase in mechanized' production techniques for reinforced plastics and, while it is not a complete primer on production techniques, this booklet fills a gap in currently available literature. Materials used in hot press moulding are described and are linked to the processes by which they are converted to finished products. Sheet and d o u g h - m o u l d i n g compounds, oreforms and both chopped and continuous strand mats are covered. T h e r e is a comparative summary of production costs for a simple moulding using either mat, preform or s i c to illustrate costing methods and the differences which a change of ma'terial can be expected to make. Information on component design, tool design, and the properties of hot press moulded components follows and is supported by a table indicating possible faults, their cause and remedy. T h e booklet concludes with a list of raw material suppliers and a bibliography. It is available to designers and moulders in GRP from Fibregla~s Limited, Publicity Department, St Helens, Lancashire, UK.

Bonding of polyurethane A new range of vulcanizable bonding agents for polyurethane are being marketed under the name T h i x o n by C o m p o u n d i n g Ingredients Limited of Manchester, a subsidiary of Dayton Rubber Company, Ohio, USA. T h i x o n AB 1244 is the latest development. It will bond castable and thermoplastic polyurethane to metals, ceramics, fabrics, other elastomers and polyurethane itself. T h e bond is resistant to high and low temperatures and curing can be carried out over a wide range of temperatures up to 230°C. C o m p o u n d i n g Ingredients Ltd, Byrom Honse, Quay Street, Manchester 3, UK

Courtaulds carbon fibre price reductions Courtaulds Limited announce new prices for their Grafil A continuous carbon fibre, to come into operation immediartely. This fibre has a modulus of 1 8 0 - 2 2 0 G N / m 2 and an ultimate tensile strength of 1'90-2-60 G N / m ~. T h e price for Grafil A fibre in 50 tonne lots is now £8.20/lb (£18/kg). For 10 tonne lots it is £13.60/1b (L'30/kg), for 1 tonne lots £20.50/11) (£45/kg). For the smallest evaluation quantities - - less than 5 0 k g - - it is still £ 3 5 / l b (£77/kg). Whilst the prices quoted apply specifically to Grafil A continuous fibre, substan,tially lower prices now exist for larger orders of Grafil H T and H M continuous fibre, and these are available on application. Courtaulds Limited, Carbon Fibres Unit, PO Box 16, Coventry CV6 5AE, UK

Polyurethane foam composite structures T h i n sheet polyurethane foams are being manufactured in three distinct forms by Speciality Converters Inc of Delaware, USA: (1) Itexible foams ill thicknes~s of 0"8-25 mm with densities ranging from 4 8 k g / m = to 480kg/m:': (2) composite structures of polyurethane foam bonded to, for example. p a p e r , paperboard, mylar, po b propylene, foil, fibre board, PW:, metal, foamed plastics and urethane film; (3) polyurethane foam reinforced with fabric or scrim. T h e foam, which has the trade name Tufcote, is manufactured by a continuous process which permits the incorporation of reinforcing scrim or laminae of other materials. This continuous process consists of sandwiching liquid urethane between two sheets of a special casting surface, passing it through metering rolls. allowing it to foam and then passing it through a heat-curing process. T h e uniform sheets of foam are then ~ p a r a t e d from the c~sting surface and wound on large diameter rolls or sheeting. T o produce laminated foams the casting surfaces are replaced by the required flexible substrate on one or both sides and bonding occurs during the normal process, liquid urethane acting as the adhesive. Reinforced foam is also produced without the need for any separate stage - - t h e reinforcing ~ r i m is introduced during the foaming process and an encapsulated structure results. Speciality Converters ]nc, Delaware Industrial Park, Newark, Del 19711, ! TSA

Carbon-fibre/glas.~-fibre ribbo,, a product of Courtaulds Limited. was ar~nounced in the January~February issue o[ Composites (page 5). ,4 clOse-up of the ribbon is shown above left: it consists of one or more tows of Grafil high performance carbon fibre in a knitted glass fibre tape. The knitting operation is undertaken by ]ames Bennett Limited of Hinckley using glass fibre supplied by Marglass Limited,. Sherborne, Dorset. The standard ribbon is 16 m m wide. ,'1 panel reinforced with the new ribbon is shown above right. Additional reinforcement at cross-over points is provided by the knitted glass. Courtaulds Ltd, Carbon Fibres Unit, PO Box 16, Coventry CV6 5AE

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[COMPOSITESnews[ GRP racing car replicas Replicas of five Marlboro-BRM racing cars are being made in the Huntingdon works of Specialised Mouldings Limited. BRM have supplied steering, suspension and brakes but otherwise everything is made of GRP. T o make the replicas realistic, the c.RP tyres have been given a thin rubber tread and powdered alumihi,um has been added to the plastic gel coat used on the GRP engine and gearbox casings to give the effect of cast aluminium. T h e contract, worth £12000, has been awarded to Specialised Mouldings by Philip Morris (Europe) SA, European headquarters of the makers of Marlboro cigarettes, who will be using the replicas for publicity. T h e cars appeared at the motor show in Geneva. Specialised Mouldings Ltd, Red,aongs Way, Huntingdon PE18 7HB, UK

Publication on strength of concrete pavements A theoretical study of the effects of strength of concrete on the performance and economics of concrete pavements has been published by the Road Research Laboratory, Crowthorne, Berkshire, UK. Results of a number of experiments are reported, the most important being tests carried out on the A1 road at Alconbury Hill (Hunts) in 1957 using a mixture of concrete slabs of normal strength (for the UK) and also slabs of higher strength similar to that used in some continental countries. T h e slabs were studied after 10 years of trafficking and it was concluded that the life of a concrete road slab is approximately proportional to the flexural strength to the power 3.2. J. M. Gregory of the Road Research Laboratory, the author of the present report, uses ~ i s result to develop a method for assessing the economics of using concrete slabs with different thicknesses and strengths. He concludes that in certain circumstances ,~nall economies can be made by using concretes of higher strength than usual. Copies of the report, 'The effect of strength on performance and economics of concrete pavemen~ts' by J. M. Gregory, may be obtained by wri,ting to the Director of Road Research, Road Research Laboratory, Crowtheme, Berkshire, UK

Metal plating of plastics A new technique for plating hydrophobic plastics, silicone rubber and lacquers has been developed by the Process and Applied Research

1100 COMPOSITES May 1972

Laboratory of RCA International I,imited. T h e first stage in plating plastics with metals must be an electroless process since plastics do not conduct electricity. However, some plastics, such as polytetrafluoroethylene are hydrophobic and cannot be coated efficiently using conventional .techniques. T h e technique developed by RCA improves the wetting of plastics like ~rrE, that is, it reduces the contact angle at the liquid/solid interface. T h e non-conducting material to be plated is dipped into a sensitizer and then into an activator liquid. This sequence forms a thin catalytic layer on the surface of the material and this causes initiation of the electroless plating process. T h e new sensitizer component used by RCA is an aged stannic chloride solution in a certain concentration range. Both stannous and stannic ions are thought to be essential ingredients. I,t is believed that a polymerized form of a stannic compound is formed during ,the ageing and that this improves the wett~bility. Stannous ions are absorbed on the substrate surface and addition of the activator, a solution of pMladium chloride, ca,use~ a chemical reaction in which elemental palladium is ,formed : this initiates the electroless plating process. Adding sodium chloride .to the sensitizer further improves its performance. With ,the RCA sensitizer the contact angle of a liquid on PaWE is 15 °, compared with 105 ° with a conventional sensitizer. This technique should permit the plating of a range o~ hydrophobic materials, previously thought to be unplatable. R C A International Ltd, R C A House, 50 Curzon Street, L o n d o n W1Y 8EU, UK

New epoxy adhesive A new, thicker type of epoxy adhesive which combines high tensile and adhesive strengths with the ability to fill gaps between surfaces to be joined has been introduced by Lamacrest Ltd, Harrogate, UK. Called Lamacrest Epoxy Adhesive 517, it has a paste-like consistency and has been specially formulated to provide stress-transmitting bonds between concrete elements, for anchoring steel rods into concrete, and for a variety of other adhesive tasks where a degree of gap filling is required, such as sticking fascia to walls or chipboard to floors. It can also be used for sticking down kerbs, road markings, signs, etc. Compressive strength is 125 M N / m ~and failure occurs in the steel rod when a rod anchored into concrete with 517

is subjected to very high tensile forces. U p to this point slipping is slight. T h e tensile strength is 25 M N / m ~. flexural strength 45 MN/mL elasticity modulus 3 0 G N / m ~, and Martens heat distortion temperature 60°C. T h e product will cure rapidly even at low temperatures. At 50°C it will cure in 16-24 hours, while at 25°C it will cure in 4-8 hours. Pot life at 50°C is 30 minutes. Cost is 60p per l h Lamacrest Lid, Crown Works. Cold Bath Road, Harrogate, Yorkshire, UK

New concrete hardening agent British Solvent Oils Ltd .(Bristol), a member of the BOC Group, has introduced a new dustproofing and hardening agent for concrete floors to the UK market. Known as Extrahard, the product is colourless and nontoxic. When applied to calcium compounds it reacts with them to form a dense and hard surface with greatly increased resistance to abrasion. Extrahard should be applied by brush to dry, grease-free concrete surfaces. T w o coats are necessary for maximum effect, allowing 24 hours between coats. When the hardening agent has completely dried out. the floor surface can be painted. T h e material can be used on old concrete floors to elimina.te excessive dusting, or on newly laid floors to give an extra hard surface to tamped concrete or smooth paving floors. One gallon of Extrahard is sufficient to cover approximately 30yd 2 (25 m') of smooth paving or 20yd ~ (17 m ') of tamped concrete. It can be supplied in five and 45 gallon drums. British Solvent Oils Limited, Victoria Works, Mount Street, Accrington, Lancs BB5 0PW, UK

Low density glass microballoons New glass microballoons, called Eccospheres FTL-200, have been developed by the Dielectric Materials Division of Emerson g: Cuming Inc, Massachusetts, USA. A very low density is achieved by reducing the wall thickness to 1.5 ptm and increasing the size of the individual microba!loon to an average diameter of about 1001~m. This results in a true particle density of 0.209g/cm 3 and a bulk density of 0.130 g / c m 3. In spite of the thin wall, sufficient strength is maintained in the microballoons for use in electronic/electrical applications as a loading material to reduce the density and dielectric constant of encapsulating resins. For example, with a hydrostatic pressure of 345 k N / m ~ only 3"7% of the microballoons collapse, Using these micro-

I COMPOSITES news[

Microphotograph of Eccospheres FTL200 at a magnification of 200 times balloons the dielectric constan,t of an epoxide casting resin could be reduced to approximately 2.0 at 1 MHz. At the same time the density of the loaded resin would be only about 0"6 g / c m 3. Eccospheres FTL-200 are priced at about $10.00 per pound. Emerson 8c Cuming (UK) Ltd, Colville Road, Acton, London W3, UK

Epoxy screeds now available in decorative patterns Epoxy screeds such as Quentscreed are made by mixing epoxy resins and hardeners with aggregates such as silica sand and calcined bauxite and trowelling to thicknesses of 4.5 to 6 ram. They can be coloured by adding pigments b u t the decorative appeal of such materials is limited. Consequently, materials of this type have been used mainly in industrial locations, primarily for their good abrasion and chemical resistance, with decoration of secondary importance. Attempts to use naturally-occurring aggregates have not been satisfactory as these materials lack colour uniformity, chemical resistance, colour fastness and suitable particle size, etc. T o overcome this problem Quentsplass Limited, Wetberby, Yorkshire, have utilized flint aggregates coloured by organic coatings. Aggrega,tes of different particle size are then blended together to obtain adequate packing and the high compressive strengths associated with Quentsereed. Also, by mixing different coloured aggregates, attractive tweed-like mixtures are obtained. These aggregate mixtures are then mixed with Quentscreed natural matrix and applied in the usual manner. Such screeds have the slightly open texture which is satisfactory in most industrial locations. However, in the Quentscreed tweed systems the surface is usually grouted with a mat.t glaze coat which enhances the appearance and improves the wear resistance of the surface.

T h e Quentscreed tweed systems are recommended in areas where it is desired to combine the excellent mechanical properties and chemical resistance of a lightweight screed with good decorative appearance. T h u s in many factory areas i,t is possible to improve the appearance of an epoxy screed at only a slight additional cost. T h e systems also considerably enlarge the potential for Quentscreed for areas such as shops, offices, hospitals, etc. Particular interest is being expressed in the use of ,the material for shopping precincts, pedestrian bridges and walkways, etc. T h e r e are three colours available - blue tweed, green tweed and brown tweed. Quentsplass Limited, T h o r p Arch T r a d i n g Estate, Wetherby, Yorkshire LS23 7BZ, UK

More sandwich moulding licensees Non-exclusive licences for wich moulding technology granted to two Japanese prominent in the plastics

ICI sandhave been companies moulding

field. These companies are France Bed Co Ltd o f Tokyo, a leading furniture manufacturer with i,ts own moulding facilities, and Yoshikawa Plastics Co I.td of Osaka. ICI now has 13 sandwich moulding licensees. Negotiations are in progress with a number of other poten,tial licensees in many parts of the world. ICI, Millbank, London SW1P 4QG, UK

Fire and timber A 20-page booklet, 'Fire and timber in modern building design', by L. A. Ashton, has been published by the T i m b e r Research and Development Association. It surveys present fire knowledge on the use of wood in building, investigates combustibiIity ,and ignitability in relation to timber. Tests fo~: surface spread of flame and fire retardant trea'~ments are discussed. T h e booklet is ava41able free to persons in the UK; a postage and packing charge of 20p is payable by overseas applican,ts. T i m b e r Research and Development Association, T h e Building Centre, Store Street, London WC1, UK

TRAINING COURSES IN GLASSFIBRE Strand Glass Co., Ltd., Britain's largest stock•st of resins and glassfibre, is now running a series of one day courses on the uses and application of glassfibre, at their Brentford Middx I~eadquarters. Held every weekday from 9 am to about 5 pm the syllabus includes : *Moulding, sheathing and repairing in glassfibre *Casting applications *Use of flexible moulds *Polyurethanefoam and its applications*and a filmshow. Emphasis is laid upon the practical participation of the course members. No charge is made for the course nor isthereanyobligationto purchase Strand Glass Materials. A light lunch will be provided. FILL IN AND RETURN THE COUPONTODAYPLACESARE LIMITED. i

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( COMPOSITES news[ New metal inserts for plastics A special patented cold-forging process for metal inserts for plastics components has been developed by Black g~ Luff Limited. T h e new range, suitable for a wide variety of plastics fittings and components, includes straight and grooved oins and

threaded inserts up to ¼ in (6.4 ram) diameter in aluminium, copper, brass or steel. A major development in the production process is the design and manufacture of the fixing head which ensures a firm key into the plastic components. T h e special cold-forging technique produces a 'rose head' pastern on the end of the insert. When incorporated into plastics this ensures maximum stability so that the insert cannot rotate or be moved vertically under normal load. T h e cold-forging manufacturing technique offers major economies over 'turned part' processes normally used for the production of this type of component, usually involving further work to produce a fixing head. Black 8e Luff Ltd, Birmingham Faotory Centre, Pershore Road South, Kings Norton, Birmingham 30, UK

Swedish Faircrete agreement

,4 selection o[ metal inserts tor plastics components incorporating the patented "rose head" which provides secure fixing

An agreement to manufacture the new decorative concrete Faircrete in Sweden has been reached between Laing Construction Systems SA and AB Strangbetong, leading precast concrete manufacturers based in Stockholm.

Faircrete has been developed by the Laing Group to give preffabricated elements decorative effects applied by hand or machine without the need for expensive moulding. T h e address of AB Strangbetong is Mejerivagen 4, Box 9205, 10273 Stockholm 9, Sweden

Glass-reinforced coating for roofs A new glass-reinforce d coating, suitable for repairing roofs where cracking has occurred, is available from Consolidated Paint ~ Varnish (Canada) Limited. The coating called Goodyear FLEX-A-ROOF can be applied by brush or spray without heating or any other special treatment. It has a tensile strength of about 1.TMN/m ' compared with an almost zero strength for roof coatings not containing glass. In addition, the reinforced coating possesses greater flexibility and resistance to cracking. Goodyear FLEX-A-ROOF is priced at £2"19 per gallon and 2 to 3 gallons will cover 100 square feet on most surfaces. Consolidated Paint g: Varnish (Canada) Ltd, PO Box 396, Montreal North 459, Quebec, Canada

LoughboroughUniversityof Technology September12-15 The biggest, brightest and most comprehensive exhibition yet held of non-destructive testing equipment and services. NDT is an essential engineering tool in the search for better product quality, improved product performance and

greater product reliability - all of which mean increased profitability and enhanced commercial prestige for the manufacturer far-sighted enough to incorporate NDT in his production schedules. You will find the best and most up-to-date NDT equipment on show at Loughborough, with senior engineers on hand to advise you on the best and most cost-effective way to apply NDT techniques to your inspection problems.

NDT 72 is being held from September 12 to 15th at Loughborough University of Technology, Loughborough, UK. Admission is free. It is being held in conjunction with the Ninth Annual Conference of the Non-Destructive Testing Society of Great Britain, Registration forms for the Conference can be obtained from: The Secretary, Maitland House, Warrior Square, Southend-on-Sea, Essex SS1 2JY, England.

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COMPOSITESMay 1972