Background Composites are combinations of two or more materials present as separate phases and combined to form desired structures so as to take advantage of certain desirable properties of each component.

Typically composites are made up of the continuous polymeric matrix phase in which are embedded the discontinuous reinforcing element such as (a) a three dimensional distribution of randomly oriented reinforcing elements (b) as two dimensional distribution of randomly oriented elements such as a chopped fibre mat (c) an ordered two-dimensional structure which is of high symmetry in the plane of the structure such as an impregnated cloth (d) an array of parallel fibres or parallel rows of fibres.

Fibre, reinforced resins are used in a number of applications such as boat building, car-body manufacture and wind turbine systems to name a few typical examples. The current systems involve building up a thick structure by a series of sequential steps involving a coating of resin, followed by fibre (or the reverse order), the process being repeated until the required thickness is achieved and curing this composition thermally or catalytically at room temperature, after each layer is prepared or at the conclusion of completing all layers.

An alternative method involves preparing prepregs which are partly cured and are superimposed while tacky and further cured to cause the tacky surfaces to adhere to one another.

One problem with the current"prepeg"manufacture is that it is limited in the range of resins currently used. Also, the polymerisation process needs to be

carefully controlled at elevated temperature and stopped prior to complete polymerisation. Other method such as catalytically polymerised at room temperature for four times up to 20 minutes is also inconvenient and expensive.

In the former thermal process the temperature in the prepreg must be reduced quickly to room temperature for stability purposes and storage prior to use. This reduction in temperature can lead to difficulty with reproducibility in polymer properties of the"prepreg". The other disadvantage of this current system is that the range of resins available is limited and they possess limited properties.

For example, the styrene/polyester containing fibre glass are reasonably big volume, however the odour of the styrene can be an environmental problem and the rate of polymerisation of the mixture is slow until the exotherm commences at elevated temperature where the process need to be carefully controlled otherwise the uniformity of the finished polymer is impaired and the properties correspondingly affected.

Epoxy resins are often used in compositions and adhere well to many fibres.

They tend however to be more brittle, absorb moisture and are more tedious to process. Polyamides are also used but are also difficult to process requiring extended high temperature curing. Thermoplastic PEEK (polyether ether ketone) matrix has also been used but is considerably more expensive then epoxy and polyester resin.

Summary of the Invention Accordingly we provide a method for preparing a fibre reinforced composite comprising: (a) providing (i) an array of reinforcing elements such as fibres; and (ii) a radiation polymerisable polymeric matrix composition comprising a donor/acceptor component for forming a charge transfer complex; (b) combining the array of reinforcing elements and polymeric matrix to provide a continuous polymeric matrix containing the array of reinforcing elements ; and

(c) irradiating the matrix with a source of radiation selected from ultraviolet light, electron beam and gamma radiation to activate the charge transfer complex and at least partly cure the polymeric matrix.

The donor/acceptor component for forming the charge transfer complex is selected from the group consisting of: (i) a bifunctional component having an electron donor group and an electron withdrawing group and a polymerisable unsaturated group; and (ii) a mixture of (a) at least one unsaturated compound having an electron donor group and a polymerisable unsaturated moiety; and (b) at least one unsaturated compound having an electron acceptor group and a polymerisable unsaturated group.

The polymer matrix composition may further comprise additional components such as those selected from the group consisting of monomer, oligomer, binder pigment and filler.

In a further aspect the invention provides a method of forming a composite comprising a laminate of prepregs the method comprising: (a) combining a fibre array with a radiation polymerisable polymer matrix comprising a donor/acceptor component to form a charge transfer complex and optionally a Lewis acid; ; (b) applying radiation selected from ultraviolet radiation, electron beam and gamma radiation to activate the charge transfer complex and partially cure the matrix composition to provide a solid prepreg having a tacky surface; and (c) stacking two or more prepregs having a tacky surface to provide contact between respective tacky surfaces of the prepregs; and (d) thermally curing the prepregs preferably under vacuum to provide adhesion between adjacent prepregs.

Detailed Description of the Invention The polymeric matrix of the composite comprises a donor acceptor component for forming a charge transfer complex. The polymeric matrix may and typically will include further components selected from monomers, oligomers, binders, pigments and additional fillers.

It is preferred that the donor/acceptor component constitute at least 5% by weight and preferably at least 10% by weight of the polymer matrix composition.

The composites prepared by the process of the invention are typically in the form of sheets of at least 1mm in thickness. Most preferably the composites comprise prepregs of thickness in the range of from 1 to 20 mm and preferably 1 to 10 mm. It will be understood however, that by lamination a multiplicity of prepregs may achieve considerable thickness. The thickness which can be achieved will also depend on the type of energy used, the presence of any catalysts or initiator and the dose of energy per unit area used in the curing process.

Prior to the present invention composites of this type were formed virtually exclusively by thermal curing process and it was generally thought that composites of this type would not be efficiently cured by radiation. We have found that the use of donor/acceptor complexes makes this possible. Further we have found that when donor/acceptor complexes are cured in combination with Lewis acid catalysts the rate of cure is accelerated to such an extent that radiation curing is not only feasible but is cost competitive and superior to thermal curing in many respects.

The Lewis acids acts as accelerator in the presence of the charge transfer complex. The composition can therefore be cured more rapidly than is possible in the corresponding composition without the Lewis acid. Further in many cases the invention allows compositions containing charge transfer complexes which could only be cured with difficulty and hence are not commercially useful, to be used in an efficient curing system.

Lewis acids may be classified as hard, soft or borderline Lewis acid using the Pearson classification of Lewis acids. Lewis acids also include protic acids such as mineral and organic acids.

The preferred Lewis acids are borderline and hard Lewis acids. Borderline Lewis acids are particularly preferred.

Examples of Lewis acids are shown in the following table : Hard Borderline Soft H+ Li+ Na+ K+ Be2+ Fe2+ Co2+ Ni2+ Cu+ Ag+ Au+ Tl+ Hg+ Mg2+ Ca2+ Sr2+ MN2+ Cu2+ Zn2+ Pb2+ Pd2+ Cd2+ Pl2+ Hg2+ Al3+ Sc3+ Ga3+ In3+ La3+ Sn2+ Sb3+ SO2 CH3Hg+ Pt4+ Te4+ Tl3+ N3+ C13+ Gd3+ Lu3+ Cr3+ Ir3+ Bi3+ Rh3+ Tl (CH3) 3 BH3 Ga (CH3) 3 Co3+ Fe3+ As3+ CH3Sn3+ NO+ Ru2+ Os2+ GaCl3 Gal3 InCl3 Si4+ Ti4+ Zr4+ Th4+ U4+ B (CH3) 3 GaH3 RS+ RSe+ RTe+ Pu4+ Ce3+ Hf4+ Sn4+ R3C+ C6H5+ I+ Br+ HO+ RO+ UO2+ V02+ wo4+ MnO3+ 12 Brs ! CN etc. (CH3) 2Sn2+ Be (CH3) 2 BF3 Trinitrobenzene etc. B (OR) 3 AI (CH3) 3 AIC13 Chloranil, Quinones etc. AIH3 RPO2+ SO3 RCO+ Tetracyanoethylene etc. 17+ 15+ C17+ Cr6+ C02 NC+ O Cl Br I N RO R02 HX (hydrogen bonding M° (metal atoms) Bulk molecules) metals CH2 carbenes

The Lewis acid may be a protic acid. Examples of protic Lewis acids include : hydrogen halides such as HCI, HF and HBr particularly HCI ; sulphuric acid; sulphonic acids such as p-toluenesulphonic acid; phosphonic acids, substituted phosphonic acids, phosphoric acid, nitric acid, phenols, substituted phenols, aromatic carboxylic acids, substituted aromatic carboxylic acids, hydroxy substituted aromatic carboxylic acids, carboxylic acids such as optionally substituted Ci to C8 carboxylic acids and mixtures of two or more thereof.

The preferred salt type Lewis acids are selected from borderline Lewis acids and magnesium. The most preferred Lewis acids of this type are halides of

zinc, tin, antimony, iron, copper, magnesium, manganese and cobalt and the like.

The preferred are SbCI3, SbC12, SnCl2. SnCl4, FeCl2, CuC12, FeS04 and ZnCts.

Any level of salt up to 100% by weight of resin can be used in this work, however 1% by weight of resin is preferred. This level may also be determined by solubility considerations of the salt. With UV work, the salts can be used in conjunction with photoinitiator (PI) to give an accelerating effect or else they can be used alone.

The preferred carboxylic acids such as Ci to C8 carboxylic acid, are Ci to C8 unsaturated carboxylic acids. The most preferred examples of carboxylic acids include formic acid, acetic acids, acrylic acid, methacrylic acid, itaconic, oxalic acid and icosic acid and citric acid. Polycarboxylic acids such as citric acid, oxalic acid, succinic acid, maleic acid and EDTA may also be used.

The Lewis acid may need only be used in catalytic amounts in some cases.

Typically the amount of Lewis acid will be less than 0.5 mole per mole of mole of double bonds in the charge transfer complex. More preferably the molar ratio of Lewis acid is in the range of from 0.0005 to 0.1 and even more preferably 0.005 to 0.05 based on a number of moles of double bonds in the charge transfer complex.

In one aspect the donor/acceptor component is an unsaturated compound that contains both the electron donor group and the electron withdrawing group.

Preferably the charge transfer complex is obtained from at least one unsaturated compound that has an electron donor group and at least another unsaturated compound that has an electron withdrawing group. The compounds employed to provide the charge transfer complex can be ethylenically unsaturated or acetylenically unsaturated. When the complex is formed from two or more compounds, typically, the double bond molar ratio of the electron donating compound to the electron withdrawing compound is about 0.5 to about 2, and more typically about 0.8 to about 1.2 and preferably about 1 to 1.

In a preferred embodiment of the invention, the polymer matrix compositions does not spontaneously polymerise under ambient conditions. The strength of both the donor and acceptor groups and their interaction with the Lewis acid are less than required to spontaneously polymerise. Instead they polymerise under the influence of the necessary ultraviolet light or ionising radiation. Alternatively where compositions are more labile they may be formed immediately prior to application and irradiation. For example the Lewis acid may be combined with the other components immediately prior to irradiation to provide an increased rate of cure.

The charge transfer complex formed from the donor/acceptor is capable of absorbing light having a wave-length that is longer than the longest wavelength in the spectrum of light absorbed by the individual donor and withdrawing groups used to form said complex. The ultraviolet light is thus absorbed by the charge transfer complex rather than by individual groups or components forming said complex. This difference in absorptivity is sufficient to permit the polymerisation of said complex to proceed by absorbing light.

In the terms of commercial utilisation, the complex typically absorbs light which has a wavelength that is about 10 nanometers longer than the shortest wavelength in the spectrum of light absorbed by the individual donor and withdrawing groups or components. This facilitates tailoring the spectral output from the ultraviolet light source to assure the desired polymerisation.

The complex should, on initial exposure to UV, lead to radicals which can initiate free radical polymerisation. In addition to UV, the polymerisation can also be achieved by the use of ionising radiation such as gamma rays or electrons from an electron beam machine. This process can be achieved to workable radiation doses and in air.

The electron withdrawing and electron donating compounds can be represented by the following formula : (A) n-R and (D) n-R, respectively;

wherein"n"is an integer preferably from 1 to 4, "R"is the structural part of the backbone. "A"is the structural fragment imparting acceptor properties to the double bond.

This is selected from the groups outlined in the Jonsson et al (US Patent 5,446, 073) and consists of maleic diesters, maleic amide half esters, maleic diamides, maleimides, maleic acid half esters, maleic acid half amides, fumaric acid diesters and monoesters, fumaric diamides, fumaric acid monoesters, fumaric acid monoamides, exomethylene derivatives, itaconic acid derivatives, nitrile derivatives of preceding base resins and the corresponding nitrile and imide derivatives of the previous base resins particularly maleic acid and fumaric acid.

Typical compounds having an electron acceptor group and a polymerisable unsaturated group are maleic anhydride, maleamide, N-methyl maleamide, N- ethyl maleamide, N-phenyl maleamide, dimethyl maleat, diethyl maleat, diethyl and dimethyl fumarate, adamantane fumarate and fumaric dinitrile.

Analogous maleimide, N-methyl maleimide, N-ethyl maleimide, phenyl maleimide and their derivatives can also be used.

When Lewis acids are present, monomers with weak electron acceptor groups can be more effectively utilized. Examples of such monomers include monomers with either pendant carbonyl or cyano groups. These can be used as acceptors since in the presence of the Lewis acid, these monomers complex and increase the difference in polarity with donor monomers. Such additional acceptor monomers include acrylonitrile and derivatives, acrylic acid and derivatives, acrylamide and derivatives, acrylates and methacrylates and derivatives, especially the lower molecular weight compounds like methyl acrylate and methylmethacrylate also methyl vinyl ketone and derivatives.

Polyfunctional compounds, that is polyunsaturated compounds including those with 2,3, 4 and even more unsaturated groups, can like wise be employed and in fact are to be preferred. The examples include polyethylenically unsaturated

polyesters, for example polyesters from fumaric or maleic acids and anhydrides thereof.

"D"is the structural fragment imparting donor properties to the double bond. Examples of component D are provided in the Jonsson et al US Patent 5,446, 073 and includes vinyl ethers, alkenyl ethers, substituted cyclopentanes, substituted cyclohexanes, substituted furanes or thiophenes, substituted pyrans and thiopyrans, ring substituted styrenes, substituted alkenyl benzenes, substituted alkenyl cyclopentanes and cyclohexenes. In the styrene systems, substituents in the ortho-and para-positions are preferred. Unsaturated vinyl esters like vinyl acetate and its derivatives can also be used.

In addition, polyfunctional, that is, polyunsaturated compounds including those with two, three, four or even more unsaturated groups can likewise be employed.

With respect to the ethers, mono-vinyl ethers and d-vinyl ethers are especially preferred. Examples of mono-vinyl ethers include alkylvinyl ethers typically having a chain length of 1 to 22 carbon atoms. Di-vinyl ethers include d-vinyl ethers of polyols having for example 2 to 6 hydroxyl groups including ethylene glycol, propylene glycol, butylene glycol, 3-methyl propane triol and pentaerythritol, diethyleneglycol and oligomers of ethyleneglycol such as triethyleneglycol.

Examples of some specific electron donating materials are monobutyl 4- vinylbutoxy carbonate, monophenyl-4-vinylbutoxy carbonate, ethyl vinyl diethylene glycol, p-methoxy styrene, 3, 4-dimethoxypropenylbenzene, N- propenylcarbazole, monobutyl-4-propenylbutoxycarbonate, monophenyl 4- propenylbutoxycarbonate, isoeugenol and 4-propenylanisole. Vinyl acetate is also active especially with monomers like maleic anhydride and the maleates. N-vinyl pyrollidone, vinyl pyridines, vinyl carbazole, and styrene can also be used in certain applications as donors also vinyl formamide (VFA).

Typical bifunctional compounds containing both acceptor or withdrawing groups and a donor group can be used and are listed in the Jonsson et al patent. Examples of suitable bifunctional compounds include those made from condensing maleic anhydride with 4-hydroxybutyl vinyl ether and the like.

A further limitation of the donor/acceptor composition disclosed in Jonsson is the relative expense of many donor/acceptor components relative to the UV curable monomers currently used in industry. Among the less expensive acceptor components is maleic anhydride (MA) which can be combined with a donor, which may be a vinyl ether such as triethylene glycol d-vinyl ether (DVE- 3), to provide a cured film.

A further preferred aspect of the invention is the use of unsaturated polyesters as a predominant component in the polymer matrix composition. One of the most preferred polyesters is defined later and is a Nuplex Australia P/L product.

In the present invention such polymers, like the Nuplex polyester when dissolved in monomers, even styrene, have been shown to cure very slowly with UV and are currently commercially viable only with difficulty. When the CT complexes are added to the polyester as additives, the resulting resin mixture cures well especially with excimer sources. Polystyrene can also be used to replace the polyester in these formulations.

Under certain circumstances with conventional UV systems, photoinitiators (PI) may be needed, however many UV sources can achieve cure without Pi.

Without these CT additives the polyester system is unsuitable for UV commercial curing. This separate aspect of the invention thus involves the use of the CT complexes already discussed as additives to accelerate the polyester cure. The addition of Lewis acids in these systems accelerate the process considerably. If Pi (photoinitiator) is needed, the types of Pis used are defined later in this application. Lewis acids may also accelerate their effectiveness.

The activating effect of the Lewis acid catalyst is such that it enables donor acceptor complexes to be used which would not otherwise be of practical use

due to their slow rate of polymerisation or the energy required for activation.

Oligomers such as vinyl ether capped oligomers and malonate capped oligomers may be used. In general, vinyl ether functionalised compounds of relevance include those derived from urethanes, phenols, esters, ethers, siloxane, carbonates and aliphatic or aromatic hydrocarbons. Specific examples of vinyl ether capped oligomers include the"Vectomer 1312"brand of vinyl ether capped urethane oligomer available from Allied Signal, U. S. A.

The invention generally allows composites to be formed using the current commercial lamp systems with donor/acceptor charge transfer complexes described above, otherwise the addition and installation of more efficient lamps becomes very expensive and limits the application of the process. Newly developed excimer sources such as the Fusion V. I. P. system will cure most of the systems discussed. These V. I. P. systems are expensive and their ready availability is required, however there are currently few V. I. P. commercial facilities on stream. The present CT system in the Jonsson et al patent possesses a number of limitations in practical use even with the V. I. P. lamp system. Thus MA, although the cheapest of available donors, suffers from the disadvantage of solubility when used with the less expensive donors like DVE- 3. This problem causes the MA to crystallise out of solution when the DA mixture is at temperatures of 25°C or lower, i. e. common room temperature.

Thus storage and transit become a problem under these conditions and the mixture to be used must be reheated carefully before application to redissolve the MA. This heating operation can give rise to significant dangers since the CT complex is very temperature sensitive and can exothermically explode if the heating is not performed carefully. This heating operation would be difficult in commercial environments. MA has another disadvantage in this work due to its volatility and odour, which is unacceptable for certain applications at the level of MA used. The problem is not confined to the DVE-3 complex. The other ethers behave in a similar manner and are more expensive than DVE-3.

Of the available acceptors other than maleates, the maleimides are the most reactive such as the alkyl derivatives such as N-hexyl maleimide. The problem with the maleimides is their toxicity and thus extreme caution must be exercised

in commercial situations with such materials. Their use is not therefore favoured industrially.

A problem also exists with the most economically available donors such as DVE-3. These materials have very low viscosity which can render the final coating formulations unsatisfactory for many commercial applications since the coatings can either run off or be absorbed by the substrate. We have found that the viscosities of such formulations are desirably increased significantly before they are suitable for industrial use.

The donor/acceptor component preferably has a relatively low molecular weight, typically of no more than 5000 and more preferably of no more than about 1100 and has a high proportion of unsaturation to readily form donor acceptor charge transfer complexes.

The composition of the invention may additionally include a binder polymer which may have a significantly higher molecular weight and low level of residual unsaturation. For example when used the molecular weight of a binder polymer is typically higher than 1100, preferably greater than 2000 or a highly viscous material and most preferably greater than 5000. A binder polymer is typically a solid or a highly viscous material at room temperature though in use in the composition of the invention it will typically be dissolved in the other components. A binder polymer preferably will not readily complex with donors such as triethylene glycol divinyl ether (DVE-3) or acceptor to provide a cured film on its own in the absence of a donor/acceptor complex.

Suitable donor/acceptor complexes for use in the present invention are disclosed in US Patent No. 5446073 by Jonsson et al. In the absence of Lewis acid catalysts or binders their use generally requires newly developed excimer sources which are not commonly used in current industrial UV curing systems.

The preferred matrix compositions of the invention which contain Lewis acids particularly allow rapid cure and yet allow their use to be controlled to provide

useful industrial application in many cases allowing UV curing in the absence of photoinitiators and yet are relatively inexpensive.

Binder polymers may be used to improve the cure speed particularly of MA/DVE-3 and similar complexes and to improve the stability of the complexes prior to cure. A further advantage of such binder polymers is that they reduce significantly the odour of MA/DVE-3 complex and related complexes.

The weight ratio of donor/acceptor complex to said binder polymer is typically in the range of 1: 99 to 95: 5 with from 30: 70 to 70: 30 being preferred and 60: 40 to 40: 60 being most preferred.

In a further preferred embodiment the acceptor comprises a mixture of maleic anhydride and an ester selected from the group consisting of the mono-and di- methyl and ethyl maleic esters. While the weight ratio of ester to MA can be up to 99: 1 we have found that the best rate of cure is provided if the ratio of ester to MA is less than 75: 25 and more preferably 75: 25 to 25: 75. Most preferably a diester is used and the ratio of diester to MA is in the range of 60: 40 to 40: 60.

The use of the binder polymer may also give stability to compositions such as maleic anhydride and increases viscosity of composition. A particular advantage is the improved solubility of the acceptor component particularly maleic anhydride and the donor particular ethers including vinyl ethers such as triethylene glycoldivinylether (DVE-3). The presence of the binder also leads to improved complex stability at a range of temperatures especially room temperature at which most applications occur.

The preferred binder polymers are selected from unsaturated polyesters, vinyl ethers, polystyrene polyarylamides, polyvinyl acetate, polyvinyl pyrrolidones, acrylonitrile butadiene styrene, cellulose derivatives and mixtures thereof.

Polyesters and polyvinyl ethers are preferred and most preferred are alkyd polyesters prepared from copolymers of a polyol such as alkylen glycol or polyalkylene glycol and anhydride such as maleic anhydride phthalic anhydride

or mixtures thereof. One specific example of the preferred polyester alkyd is available from Orica Ltd, Australia and is prepared from propylene glycol, phthalic anhydride and maleic anhydride. Particularly preferred polymers are vinyl ether capped oligomers and malonate capped oligomers as discussed hereinbefore. The oligomer portion may be a urethane oligomer. An example of the preferred vinyl ether polymer is Vectomer 1312 brand vinyl ether polymer of Allied Signal, U. S. A.

In the above examples, photoinitiators (PI's) are usually not needed with the appropriate UV processing conditions, however, if used, the Pi's and Lewis acid when combined have a synergistic effect in some compositions i. e. inclusive of the two entities, PI and Lewis acid, can accelerate the polymerisation further than when each is used alone.

Binder polymers may be used to improve the cure speed particularly of MA/DVE-3 and similar complexes and to improve the stability of the complexes prior to cure. A further advantage of such binder polymers is that they reduce significantly the odour of MA/DVE-3 complex and related complexes.

The weight ratio of donor/acceptor complex to said binder polymer is typically in the range of 1: 99 to 95: 5 with from 30: 70 to 70: 30 being preferred and 60: 40 to 40: 60 being most preferred.

In a further preferred embodiment the acceptor comprises a mixture of maleic anhydride and an ester selected from the group consisting of the mono-and di- methyl and ethyl maleic esters. While the weight ratio of ester to MA can be up to 99: 1 we have found that the best rate of cure is provided if the ratio of ester to MA is less than 75: 25 and more preferably 75: 25 to 25: 75. Most preferably a diester is used and the ratio of diester to MA is in the range of 60: 40 to 40: 60.

The use of the binder polymer may also give stability to compositions such as maleic anhydride and increases viscosity of composition. A particular advantage is the improved solubility of the acceptor component particularly maleic anhydride and the donor particular ethers including vinyl ethers such as

triethylene glycoldivinylether (DVE-3). The presence of the binder also leads to improved complex stability at a range of temperatures especially room temperature at which most applications occur.

The preferred binder polymers are selected from unsaturated polyesters, vinyl ethers, polystyrene polyarylamides, polyvinyl acetate, polyvinyl pyrrolidones, acrylonitrile butadiene styrene, cellulose derivatives and mixtures thereof.

Polyesters and polyvinyl ethers are preferred and most preferred are alkyd polyesters prepared from copolymers of a polyol such as alkylen glycol or polyalkylene glyol and anhydride such as maleic anhydride phthalic anhydride or mixture thereof. One specific example of the preferred polyester alkyd is available from Orica Ltd Australia and is prepared from propylene glycol, phthalic anhydride and maleic anhydride. Particularly preferred polymers are vinyl ether capped oligomers and malonate capped oligomers as discussed hereinbefore. The oligomer position may be a urethane oligomer. An example of the preferred vinyl ether polymer is Vectomer 1312 brand vinyl ether polymer of Allied Signal, USA.

If photoinitiators are used, for example, in highly pigmented filled or very thick systems, suitable examples of photoinitiators may include benzoin ethers such as a, a- dimethoxy-2-phenylacetophenone (DMPA); a, a-diethoxy acetophenone; a-hydroxy-a a-dialkyl acetophenones such as a-hydroxy-a, a-dimethyl acetophenone and 1-benzoylcyclohexanol ; acyl phosphine oxides such as 2,4, 6-trimethylbenzolyl diphenyl phosphine oxide and bis- (2, 6- dimethoxybenzoyl)-2, 4. 4-trimethylphenylphosphine ; cyclic photoinitiators such as cyclic benzoic methyl esters and benzil ketals ; cyclic benzils ; intermolecular hydrogen abstraction photoinitiators such as benzophenone, Michlers ketone, thioxanthones, benzil and quinones; and 3 ketocoumarins. Typical of such photoinitiators are the Ciba Geigy range of Irgacure 819,1800, 1700 and the like, also Darocure 1173.

In the case of clear polymer matrix or related systems a photoinitiator may not be necessary or may be used in minor amounts of up to 2% or higher if desired.

Pigmented systems may use a photoinitiator with the amount required depending on the level of pigmentation. Amounts of Pi may be up to 6% or higher by weight and are typical for the most difficult of pigmented systems such carbon filled or heavily pigmented composites and the like.

The photoinitiator component may also be used in combination with an amine coinitiator particularly a tertiary amine coinitiator. This is particularly preferred in the case of the intermolecular hydrogen abstraction photoinitiators such as benzophenone or the meleimides. The amine is generally triethanolamine or an unsaturated tertiary amine such as dimethylaminoacrylate, diethylaminoethylacrylate or the like.

The composite of the invention includes an array of reinforcing elements preferably fibres. The fibres may be inorganic or organic and are preferably of length at least ten times their width and preferably at least 10 mm. The fibres can be sources from naturally occurring materials like wool, wood, cellulosic fibres, carbon, glass (vitreous silica, E glass, S glass), rice husks, jute, hemp, coir and the like and synthetics such as the polyolefins, polystyrene, the polyacrylates and methacrylates like methyl methacrylate (Perspex) polyacrylonitrile, rayon aramide, nylon, and the like, even textile fibres may be used.

Examples of cellulose-based fibre arrays include softwoods, hardwoods, leaf (hard) fibers such as abaca, cantala, caroa, henequen, istle (generic), Mauritius, phormium, bowstring hemp, sisal, Bast; soft fibers such as China jute ; flax, hemp, jute, kenaf, ramie, roselle, sunn and Cardillo ; Seed-hair fibers such as a cotton and kopok; Miscellaneous fibers such as broom root (roots); coir (coconut husk fiber), crin vegetal (palm leaf segments), piassava (palm leaf base fiber); viscose (cord) and softwood kraft.

The array of fibre may be randomly oriented, aligned, in a plurality of layers, woven, non-woven fabric or as matt.

For illustration purposes here, glass fibres in matt form (600g/M2 and 1100g/M2 biaxial fibre glass cloth) supplied by FMS Pty. Ltd. , Seven Hills, Sydney, are used to illustrate the invention.

Laminates can be fabricated in different forms. A number of possible methods may be used including : (i) wet lay up, (ii) solvent prepreging and (iii) resin transfer moulding (RTM).

As long as the fibre is embedded in the resin, any relevant application technique can be used (See Dostal, C. A. , (Ed), Composites, Engineering Handbook, Vol 1, ASTM International, Ohio (1987). In the wet lay-up technique, the matt fibre fabric is placed on a sheet of low density polyethylene (typically 0.05 mm) or polyester film (0.13 mm, X-130 PPC transparency film, Folex Film Systems, Switzerland) or on an appropriate tray. The resin mixture containing all components is now poured onto the fabric and manually spread throughout the fabric. If the resin is too viscous, it is preheated before pouring onto the fabric.

For the solvent method, generally (but not necessarily) a number of layers of glass fabric can be placed in the tray and the resin, predissolved in an appropriate solvent is then spread throughout the fabric. The solvent is allowed to evaporate either at room temperature or elevated temperature.

In the methods described above, the impregnated fabric, in a horizontal configuration, is then passed under an appropriate radiation source to achieve the required degree of cure at the line speed used. The end product from these processes can be under cured or tacky whilst for others it will be fully cured depending on the specifications of the final product. In an alternate process, instead of treating the fabric layers singly, a plurality of proposed composites can be stacked after impregnation (i. e. 2 to 20 sheets) before irradiations. Any ratio of resin to fibre array can be used depending on the end application, however for most work 1 to 10 parts by weight of resin to one part by weight of fibre, more preferably 1 to 3 parts of resin to one part by weight of glass matt is preferred.

Composites used may also be filled with filler and pigment to give colour to the product and also reduce the glass. Composites may also be coated by the UV and ionising radiation processes described in earlier patents.

The invention may utilise the"prepreg"method of manufacture where a thickness, of preferably 1-10 mm of fibre reinforced resin is prepared in sheet form, the sheets being only partly cured to a tacky surface state. These sheets are then either used as is if the thickness is satisfactory for the purpose involved or superimposed on each other to give the required thickness. These sheets are then either heated preferably with the application of vacuum to remove bubbles to achieve final cure or alternatively allowed to cure at room temperature catalytically (up to 20 mins. depending on RT).

As a further modification to the process, a hybrid system involving a catalyst (usually methyl ethyl ketone peroxide) can be used with a photoinitiator. Any ratio of photoinitiator to peroxide can be used with concentrations of combined photoinitiator and catalyst being up to 20% by weight of resin with 1-5% preferred. The radiation sources used in the current work can be UV or ionising radical sources such as cobalt-60, Cs137, Sr90 and electron beam machines. typical UV sources are: (i) a Fusion UV facility of 300 Watts/cm operating at a line speed typically of 16m/min. Such lamps deliver a peak intensity of 1.7W/cm corresponding to a dose of 460 mJ/cm; (ii) Fusion VIP Excimer Source operating typically at 16 m/min and delivering a peak intensity of 5.0 W/cm; and (iii) a conventional 100 W/cm mercury lamp typically at 20 m/min with due conditions slightly lower than lamp in system (i). Line speeds can be any value depending on the cure required.

In addition to UV, ionising radiation sources like cobalt-60 or electron beam (EB) can be used. Doses from 1 Gy up to 500k Gy may be needed to cure the ionising radiation with the preferred being from 5 Gy to 60k Gy. Dose rates of

from 0.1 Gy/hr up to 4 x 10 k Gy/hr may be needed with the preferred from 10 k Gy/hr to 2 x 10 k Gy/hr.

The radiation polymerisable matrix is generally a liquid and radiation is applied to cause curing to provide a solid structure. In the case of preparing formation curing is incomplete so that the surface remains tacky but to prepreg are of sufficient integrity to allow easy handling. Prepregs or composites may generally be formed at ambient temperature and although they may be heated to 50°C or more this is not generally required. The prepregs may be laminated by heating to a temperature over 50°C, preferably over 80°C. A thermal polymerisation initiator may be present in the matrix composition to facilitate thermal curing of the laminate. The thermal polymerisation initiator may be selected to provide a thermal polymerisation temperature greater than the ambient temperature or the temperature at which radiation polymerisation takes place. Typically the thermal initiator will be activated at a temperature over 70°C.

The composition used in the method of the invention may include a thermal polymerisation inhibitor such as di-t-butyl-p-cresol, hydroquinone, benzoquinone or their derivatives and the like. Di-t-butyl-p-cresol is preferred. The amount of thermal polymerisation inhibitor is typically up to 10 parts by weight relative to 100 parts by weight of the matrix component.

The composition may contain an ultraviolet light stabiliser which may be a UV absorber or a hindered amine light stabiliser (HALS). Examples of UV absorbers include the benzotriaziols and hydroxybenzophenones. The most preferred UV stabilisers are the HALS such as bis (1,2, 2,6, 6-pentamethyl-4- piperidyl) sebacate which is available from Ciba as TINUVIN 292 and a poly [6- 1, -1,3, 3-tetramethylbutyl) imino-1,3, 5-triazin-2, 4-diyl] [2,2, 6, 6-tetramethyl-4- piperidyl) imino] hexamethylene [2,2, 6, 6-tetramethyl-4-piperidyl) imino] available from Ciba under the brand name TINUVIN 770. The amount of UV stabiliser that is effective will depend on the specific compounds chosen but typically up to 20 parts by weight relative to 100 parts by weight of resin component will be sufficient.

The UV stabiliser may be used simply to provide UV protection to the coating applied in accordance with the invention in which case up to 10 parts by weight will generally be adequate and in the case of HALS 0.05 to 5 parts is preferred.

In some embodiments however it may be desirable to use a high concentration of stabiliser particularly where UV protection is also to be provided to the composite.

If flame retardency is desired the composition used in the process of the invention may include one or more flame retarding additives. Preferred examples of such additives may be selected from the following : a:"FYROL 76"* (with and without free radical catalyst such as tertiary butyl hydroperoxide, cumene peroxide or ammonium persulphate) ; b:"FYROL 51"* c:"FYROL 6"*and/or"FYROL 66"*with and without catalyst ; PRODUCTS OF AKZO CHEMICALS LTD.; d:"PE-100"and"W-2" (EASTERN COLOR CHEMICALS P/L) of the USA; e:"PROBAN"*with and without catalyst such as ammonia or an amine; *an ALRIGHT AND WILSON Aust. PTY LTD. PRODUCT; f:"PYROVATEX"*with and without catalyst ; *a CIBA GEIGY Aust. PTY LTD. PRODUCT; g :"PYROSET"*"TPO"and"TKOW"with and without catalyst ; *PRODUCTS OF CYANAMID Aust. PTY. LTD.; h: simple phosphates such as mono, di, and triammonium ortho phosphates and their alkali metal equivalents ; i: alkali metal and ammonium sulphamates ; j: alkali metal and ammonium range of poly phosphates; k: ammonium sulphates; I : alkali metal and ammonium chromates and dichromates; m: alkali metal carbonates; n: alkali metal tungstate; o: boric acid and borax; p: organo phosphorus or organo boron compounds; and mixtures of two or more of the above.

The preferred amount for each system may be determined by experiment.

When the additives are used with the resin, the finished product may be fire retarded in accordance with Australian Standard AS1530 Parts 2 and 3.

Particularly preferred fire retarding additives are Fyrol 76, Fyrol 51, PE-100 and W-2 and mixtures thereof. The other flame retardants in"a"to"p"are best used for specific applications and as with all the above retarding additions, their conditions of use are determined by the equivalent level of phosphorus present in the finish. When the Fyrols or PE-100 or W-2 are used, the amounts are 1 to 50% based on the mass of resin solids with 2 to 20% preferred. Generally, the equivalent proportion of elemental phosphorus (and boron if used in combination) in the combination to a level of 4.0% P is needed to achieve the required flame retardency. However, significantly less may be needed depending on the substrate material. For example some materials may need only 2.0% P. In such cases the exact levels of phosphorus containing compound required are determined exactly by experiment. Thus the range covered from 0.02 to 15% of elemental phosphorus based on the mass of the substrate material to be treated may be used, with 0.2 to 4.0% P being the preferred range to achieve flame retardency. Flame retardants are particularly useful where the coating is to be applied to a textile or natural or synthetic fibre.

The invention will now be described with reference to the following examples. It is to be understood that the examples are provided by way of illustration of the invention and that they are in now way limiting to the scope of the invention.

Example 1 This example demonstrates the use of the invention in preparation of a composite glass fibre reinforced prepreg of 10 mm thickness.

A polymer matrix was prepared by mixing maleic anhydride (acceptor): DVE- 3 (donor) : polyester in a weight ratio of 1: 2: 2. The polyester used was a polyester alkyd prepared from propylene glycol, phthalic anhydride and maleic anhydride and supplied by Nuplex Australia. The composite was formed by a

wet fay-up technique in which the glass fibre matt (600g/m2 supplied by FMS Pty Ltd, Seven Hills, Sydney), was used in an amount of 10% by weight of composite. The glass fibre was placed on polyethylene film mould and the polymer matrix composition poured onto the glass matt and spread on the glass fibre array.

The composition was irradiated with ultraviolet light of UV intensity of 104 watts per cm2 and a dose of 0. 2 joules per cm2 using a F300 lamp and a"D"bulb at a speed of 16 metres per minute. The resulting product was cured to solid flexible state with a tacky surface and is useful as a prepreg for manufacture of composites by thermally curing a plurality of sheets with abutting tacky surface.

By repeating the above method with addition of 0.1% by weight IRGAGURE 184 photoinitiator (Ciba) the composite was fully cured. Alternatively, in the absence of Pi the line speed could be reduced to 4 metres per minute to produce a tacky surface.

Example 2 The method of Example 1 was repeated using a polymer matrix which was a mixture of methylmaleimide (acceptor): DVE-3 (doner): polyester in a weight ratio of 3: 4: 4. Results were similar to observed for example 1 except that cure was slower with a tacky surface (suitable for prepreg use) remaining when a line speed of 8 metres per minute is used. Full cure is observed at this speed with the addition of 0. 1% w/w IRGAGURE 184.

Example 3 The examples demonstrate the accelerating effect of combining photoinitiators with Lewis acids, if needed. The invention may be used to coat a range of materials including polymeric materials, cementitious, metallic and cellulosic materials. The compositions of the invention may also be used to form composites by including fibrous components such as natural, polymeric or material fibres. Fibrous material may be incorporated into the composition or the substrate may be overlayed with fibrous material such as fibreglass before application and curing of the composition of the invention to form a composite. Composites of this type are useful in forming complex shapes such as in boat

building. The composition of the invention are particularly useful in coating polystyrene and one embodiment are used to coat a polystyrene shaped article.

In one specific embodiment, coatings of the invention are plied to a pallet of the type used for support and transport of goods. The pallet may be formed of polystyrene or other suitable material optionally using a fibrous reinforcement before application and curing of the coating composition.

Examples of the above concepts are shown in Tables 1-3. This example shows the acceleration effect of Lewis acids compared with Pi in gelling of typical CT complex formulations in bulk. This information is important in the use of the technique for composite work and IPN processes. The examples examined the results of relatively thin coatings but the relative effects demonstrate the significant advantage of curing Lewis acids to accelerate cure. In composites the thickness of the matrix will increase the difference provided by Lewis acids.

Examples of the use of a Lewis protic acid are also given. The Lewis acids used to accelerate these reactions are Lewis acids such as SbCts, SbCI5, Zinc12, Fers, FeCl3, SnCI2, SnC4, CuCI2, MgCl2, MnCl2, CoCl2, CoCl3, and the like.

Theoretically any anion is capable of being used, the halogens are preferred with the chlorides being most preferred because of suitable solubility properties and the like. In UV work they can be used with photoinitiators (PI) to give an accelerating effect or they can be used alone. No PI's are needed with ionising radiation work. Currently SbCI3, SbCI5, FeCI2, FeCI3 and SnC4 give the best performance. Lewis protic acids can also be used as shown by the HCI example. Non-protic Lewis acids are preferred for cellulose and related fibre arrays due to possible attack on the substrate by protic acids.

Three predominant applications of the Lewis acid effect are as follows : 1. Polymerisation of charge transfer complex (CT) in bulk 2. Grafting of CT to substrates like cellulose and the like including synthetics such as the polyolefins, polystyrene and the like and improving binding in the composite 3. Curing of CT complexes.

Polymerisation in Bulk The results in Table 1 show typical CT complexes and the UV dose required to gel with and without Lewis acid such as SbCts. A comparison with a typical PI like 1% Irgacure 819 is shown in the Table 1. These types of bulk conditions are usually formed in composite work and act as a guide for radiation conditions with film composites.

Polymerisation and Graft Table 2 shows typical results for polymerisation when Pi and SbCI3 are combined in UV system. An enhancement in rate is noted when compared to the analogous system in Table 1. If a substrate such as cellulose is included in the CT solution, grafting occurs i. e. grafting is achieved at lower doses in the presence of SbCts.

Use of ionising Radiation Table 3 shows the effect of inclusion of Lewis acid when ionising radiation is used as source. Again in the presence of Lewis acid lower levels of radiation are needed to achieve gelling.

Curing In the presence of Lewis acid the UV dose to cure CT complexes like MA/DVE- 3 is reduced to at least one quarter. In some systems it is envisaged that the radiation dose may be able to be reduced by a factor of 10 or more. In many cases curing is too slow for commercial utilisation without the Lewis acid.

The important feature of the work with ionising radiation is that cobalt-60 can now be used as curing source because the doses to cure are so low e. g. 25 Gy in Table 3 with some CT complexes.

Any levels of Lewis acid can be theoretically used for this work, however, 1 % w/w is a preferred economic level.

If radiation doses higher than shown in Table 3 with Suc13 are required to cure, that the system is less attractive for cobalt-60 work although with very large sources it may be possible although economically not generally attractive.

The present system is also suitable for electron beam (EB) cure with the doses shown in Table 3.

Table 1 Effect of SbCl3 and PI on Accelerating Polymerisation of CT Complexes with UV Radiation MA/DVE-3 Complex Additives Used UV Dose (J) Physical State 1 % PI 2. 4 Gel No Additive 132 Gel 1% SbCl3 Instantaneous* Gel * On exposure to UV MMA/DVE-3 Complex Additives Used UV dose (J) Physical State 1% Pl 108 Viscous Gel No Additive 147 Viscous Gel 1% SbCl3 108 Viscous Gel

Ethyl Maleimide/DVE-3 Complex Additives Used UV dose (J) Physical State 1% Pi 19 Off White Gel No Additive 108 Off White Gel 1% SbCl3 37 Off White Gel Phenyl Maleimide/DVE-3 Complex Additives Used UV dose (J) Physical State. 1% Pl 24 Yellow Gel No Additive 254 Liquid 1% SbCl3 60 Yellow Gel DMMA/DVE-3 Complex Additives Used UV dose (J) Physical State No Additive 54 Clear Gel 0.1% HCI (ION) 31 Clear Gel

Conditions of work reported for the above results : # Room Temperature maintained at 20°C UV lamp dose rate was 1.02 x 10-2 Joules/Sec. Samples were positioned 30 cm from 90W medium pressure Hg arc lamps . Monomer complexes were prepared by mole ratio of 1: 1 w Irgacure 819 PI was used Monomers used were prepared as 90% v/v in acetone 1% SbCl3 was made up as a 1M Acetone solution and was added at 10% v/v in acetone Table 2 Additive Effects of Lewis Acid and PI On Accelerating UV Polymerisation of CT Complexes Concurrent Grafting Yields on Cellulose (Whatman 41 Papers) Monomer % Composition Graft UV Dose Physical State (J) * MMA/DVE-3 + PI + SbCl3 10 24 Highly Viscous Gel MA/Vinyl Acetate + PI + 466 10 Yellow White Gel SbCl3 Mono-Butyl Maleate + PI + 234 5 Gel SbCl3 Bis (2-Ethylhexyl) maleate + 225 12 Gel Pi + SbCI3 * Dose to gel, samples removed just prior to gel Conditions of Work reported for the above results: w Solutions prepared in acetone grafting with 10% v/v of PI + SbCI3 Monomer concentrations prepared were 90% v/v

Mole ratio used was 1: 1 Room Temperature 22°C 1% of Irgacure 819 Pl 1 M solutions of SbCI3 prepared in acetone and used neat solvent The 10% v/v used was composed of 5% of the PI and 5% of the 1 M SbCI3 in acetone Dose rate 1.02 x 10.2 Joules/sec. ; Samples were positioned 30 cm from 90W medium pressure Hg arc lamp.

Table 3 Effect of Lewis Acid on Accelerating Polymerisation of CT Complexes Initiated by lonising Radiation Complex SbCI3* Irradiation Observation Dose (Gy) 1) 90% MA/DVE-3 1: 1 in Acetone 10% NIL 763 Light Gel 2) 90% MA/DVE-3 1: 1 in 10% Acetone 1% 254 Gel, Cracking 3) DMMA/DVE-3 1 : 1 1% 254 Gel 4) 97% MA/DVE-3 1: 1 in Acetone 3% 1% 25 Gel 5) 90% MA/DVE-3 1 : 1 with 10% VA 1% 25 Gel * SbCl3 1 molar in Acetone ** All complexes 1: 1 molar ; Dose Rate = 7.63 kGy/hr in Cobolt-60 source ***Samples 3,4, 5 without SbCI3 required doses at least four times that of samples with SbCI3 MA= Maleic anhydride DVE-3 = Triethyleneglycol divinyl ether DMMAS = Dimethyl maleate VA = Vinyl acetate The present UV resin systems can be pigmented for composite applications if desired. The UV conditions required to UV cure paints are a guide to the composite application and demonstrate how inclusion of Lewis acid can improve the UV curing performance of the pigmented polymers. Under some circumstances, for a white pigmented system, and using a 600 Watts/inch excimer source no PI is needed to achieve cure at line speeds up to 10 metres/min for the paint. With lines of lower performance, such as mercury, are systems which are the norm in conventional commercial UV processing; Pl's are generally needed to initiate cure as shown in Table 4 where no Lewis acids are included. Inclusion of Lewis acid in systems such as the excimer above, faster line speeds can be achieved by up to a factor of 10 or more. When appropriate Lewis acids are included for the systems in Table 4, the amount of PI required to cure can be reduced, in some instances by up to a factor of 10 or more.

Table 4 PIGMENTED POLYMERS Photoinitiator Levels for Paint without Lewis Acid Preferred PIGMENT LEVELS Range Pl% 11% Red + 89% (MA: DVE-3): PE (1: 1: 2) 0.0-2. 0 3.8% Black+96. 2% (MA: DVE-3: PE (1: 1: 2) 0.0-4. 5 9% Yellow + 91% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5 10% White + 90% (MA: DVE-3): PE (1 : 1 : 2) 0.0-0. 3 9% Blue + 91% (MA: DVE-3): PE (1: 1: 2) 0. 0-0. 3 11% Red + 89% resin consisting of MA: DVE-3: PE 1: 1: 2 by weight Remaining pigments same formula Preferred + 20% UR240* Range PI% 11% Red + 89% (MA: DVE-3) : PE (1 : 1 : 2) 0. 0-2. 0 3. 8% Black + 96.2% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5 3. 8% Blk/Blu + 96.2% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 0 9% Yellow + 91% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 0 9% Blue + 91% (MA : DVE-3) : PE (1: 1: 2) 0. 0-3. 0 1 Paint formulations are 80% as per formula + 20% UR240 Resin Preferred +20% Filler for Matt Finish Range Pl% 11% Red + 89% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5 3.8% Black + 96.2% (MA: DVE-3): PE (1: 1.2) 0.0-4. 5 3.8% Blk/Blu + 96.2% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5 9% Yellow + 91% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5 9% Blue + 91% (MA: DVE-3): PE (1: 1: 2) 0.0-4. 5

Formulations are 80% of"Gloss"+ 20% Filler for matt finish DVE-3 = Triethylene glycol divinyl etner UR240 = aromatic urethane from Balling P/L Running Condition as in Table 5 Mt = Polyester from nupiex r/L MA = Maleic anhydride

The effect of inclusion of Lewis acid in polymer matrix is shown in Tables 1-3, the inclusion of pigment increases the doses to gel slightly (5-25%). In very lightly pigmented systems, there is almost no change to this curing dose data in the tables 1-3. These results will of course also depend on the thickness of the composite.

A typical Lewis acid effect is shown in the following example where PE is a polyester polymer which does not effect the curing chemistry of the CT complex. Again it is convenient for demonstration purposes to show the Lewis acid effect as a high gloss coating system.

High Gloss Coating DVE-3 20g DEMA 10g PE. 15g Irgacure 819 : 0. 5g After coating, sample is cured under a 300 Watt/inch mercury arc lamp at 20 metres/min. If Fusion 300 Watt/inch lamp with"D"bulb or an excimer source of 600 Watts/inch is used, no PI is required to cure at 20 metres/min. Inclusion of Lewis acid (such as SbCI, 1% w/w) leads to no Pi to cure at 20 metres/min with a 300 Watt/inch mercury arch lamp. Inclusion of the Lewis acid with the excimer source leads to curing at significantly higher line speeds.

Application of lonising Radiation Sources The above examples listed have utilised UV and excimer sources with and without Pl. If these sources are replaced by ionising radiation sources such as EB (low energy electron beam from ESI or RPC or the equivalent) or Cobalt-60 (or equivalent spent fuel element facility) the formulations can be cured without any Pi being present. The technique is particularly useful with Co-60 type sources. here, with the formulations like those for the high gloss above, curing can be achieved at a dose of up to 0.2 kGy without Pi at any dose rate in air.

Under nitrogen even lower doses may be used. Higher doses than 0.2kGy may be used if needed under specific circumstances even up to 5kGy. For all the formulations in this patent, both clear and pigmented, all can be cured at doses

up to 0.2kGy at any dose rate without Pi and at even lower doses with nitrogen atmosphere. Inclusion of Pi leads to lower doses than 0.2kGy to cure however the cured formulation is then contaminated with PI fragments. Under some circumstances and in some applications the presence of these impurities can be tolerated and curing in the presence of the Pi can lower the radiation dose to cure to doses up to 0. 1 kGy. Inclusion of Lewis acid in these ionising radiation runs leads to enhancement in cure even at very low dosage. For example, it is possible to achieve cure with dose levels lower than. 01 kGy. Inclusion of Pi can lower this dose even further