Abstract: There is provided a photocurable resin composition comprising (A) an urethane acrylate having three or four acrylate groups in the molecule, (B) a radical polymerizable compound different from the above urethane acrylate; and (C) a photopolymerization initiator, the weight ratio of the urethane acrylate (A) to the radical polymerizable compound (B) being 80:20 to 10:90; and a production process thereof. The said photocurable resin composition can provide moldings and stereolithographed objects having excellent dimensional accuracy with a small volume shrinkage factor at the time of photo-curing and excellent heat resistance with a high thermal deformation temperature as well as excellent transparency and mechanical properties such as tensile strength.

Abstract: A method of generating reactive species which includes exposing a wavelength specific photoreactor composition to radiation, in which the wavelength specific photoreactor composition comprises one or more wavelength-specific sensitizers associated with one or more reactive species-generating photoinitiators. Also described are methods of polymerizing unsaturated monomers, methods of curing an unsaturated oligomer/monomer mixture, and methods of laminating.

Abstract: Radiation-curable formulations based on ethylenically unsaturated prepolymers and difunctional esters of ethylenically unsaturated carboxylic acids with diols having a linear alkylene chain of 7 to 14 carbon atoms, a process for coating substrates using these radiation-curable formulations, and their use as automotive topcoats.

Abstract: Described are preferred UV curable coating compositions which are suitable for use as basecoats in the production of lamp reflectors. Also described are reflector devices and methods for making them.

Abstract: Radiation-curable compositions are disclosed which, after cure, are substantially non-yellowing. The compositions are particularly tailored for coating and bundling of optical fibers. A first preferred composition is based on a polyether-type of oligomer diluted with reactive diluents. Isocyanurate structures are included in the composition to raise Tg. A second preferred composition is based on fatty oil comprising (meth)acrylate groups and bisphenol A derivatives comprising (meth)acrylate groups. Photoinitiators can be included to increase cure speed. The formulations do not include material amounts of ingredients which tend to cause yellowing or, in theory, extended conjugation in the cured compositions.

Abstract: A printing sheet having a high gloss and an enhanced ink-setting property has an outermost surface coating layer formed on a substrate sheet from an electron beam-cured resin produced from at least one electron beam-curable unsaturated organic compound selected from (A) unsaturated reaction products obtained by first reacting a long chain alkylene (C15 or more) diol compound having a number average molecular weight of 300 to 10,000, with an aromatic, cycloaliphatic or aliphatic polyisocyanate compound and secondly reacting the first reaction product with a (meth)acrylate of a hydroxyl compound.

Abstract: An ultraviolet curable coating composition for cationic electrodeposition applicable to metal plated materials which composition comprises 100 weight parts of acrylic resin containing 10 to 70% by weight poly-functional acrylate per se having 3 or more acryloyl groups and 90 to 30% by weight of a resin of molecular weight 2,000-30,000 having a cationic electrodeposition property, and 0.1-10 weight parts of 2 or more species of photopolymerization initiators which absorb ultraviolet radiation in a wavelength range of 300-400 nm, as effective ingredients. The coating composition can readily be deposited electrically on metal materials including plated products and plastic materials provided with electrical conductivity and cured by irradiation of ultraviolet radiation within a short period of time to give a dry coating film which is appreciable in adhesiveness to the plated materials and good in appearance.

Abstract: The invention relates to ophthalmic mouldings, especially contact lenses, obtainable by cross-linking a prepolymer that corresponds essentially to formula (1) wherein the variables are as defined in the claims, in the absence or presence of an additional vinyl comonomer.

Abstract: A vibration damped structure, which is excellent in vibration absorption and sound absorption effect, is provided by coating the surface of a structure to be damped with a mixture of molten photopolymerizable resin and a photopolymerization initiator and then subjecting the coated surface to irradiation, whereby a vibration damping coating is formed on said surface.

Abstract: A method of making radiation-curable, fiber optic materials having extended shelf-life and reduced water content which when suitably cured provide reliable and consistent adhesion characteristics to optical glass fibers.

Abstract: A photosensitive resin, process for its use, and printing plates formed thereby are disclosed wherein the photosensitive resin comprises (i) a polyurethane prepolymer which is the reaction product of at least one polyether diol having olefin unsaturation equal to or less than 0.01 meq/gm, at least one diisocyanate, and a hydroxy-functionalized (meth)acrylate, (ii) at least one monomer and (iii) at least one photoinitiator.

Abstract: To provide liquid composition that allows efficient production of easy detachable adhesive solid, and adhesive products which are produced using said composition, wherein said products can be used repeating attaching and detaching and restore adhesiveness by washing when the adhesiveness was lowered. The liquid composition is cured by exposure to UV light to give easy detachable adhesive solid. For example, liquid composition containing oligourethane diacrylate 35.0 wt %, [Compound 2] 59.0 wt %, acetophenone-derived photo-initiator  5.0 wt %, and additives  1.0 wt % is screen-printed in a film with a thickness of 15 &mgr; m on 50% area.

Abstract: Adhesive coating film consisting of a) a radiation-cured coat which comprises from 40 to 90% by weight, preferably from 50 to 60% by weight, of urethane acrylate, from 0 to 20% by weight, preferably from 10 to 15% by weight, of polyether acrylate, from 10 to 50% by weight, preferably from 25 to 40% by weight, of reactive diluent, from 0 to 30% by weight of pigments from 0 to 10% by weight, preferably from 2 to 5% by weight, of a carboxy-functional (meth)acrylic esther [sic], from 0 to 10% by weight of other customary coatings fillers, and in the case of curing with UV radiation, from 0 to 10% by weight, preferably from 3 to 6% by weight, of photoinitiator, and b) which carries on one side an adhesive composition which has free NCO groups in the freshly applied adhesive composition, can be plastified thermally, especially under the intended processing conditions, and has a markedly weak surface tack.

Abstract: A photocurable paint composition for road markings is disclosed, comprising (A) a compound having an ethylenically unsaturated group, (B) a filler, (C) a cationic dye represented by formula (1): D+&Circlesolid;A1−  (1) (wherein D+ represents a cation having an absorption maximum wavelength in the wavelength region of from 400 to 1,200 nm, and A1− represents an optional anion), (D) a quaternary organic borate-type sensitizer represented by formula (2): (wherein R1, R2, R3 and R4 each independently represents an alkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkynyl group, a silyl group, a heterocyclic group or a halogen atom, and Z+ represents an optional cation) and (E) an ultraviolet radical polymerization initiator capable of generating a radical upon absorption of light at a wavelength of 400 nm or less, or additionally comprising (F) glass beads.

Abstract: A light-curable polymer material for making an intraocular lens is a mixture of components consisting of oligourethanemethacrylate, octylmethacrylate, oligocarbonatemetharcrylate, 2,2-dimethoxy-2-phenylacetophenone and 2,4-ditretbutylortoquinone, wherein the aforesaid components are taken in the following weight % ratio: 2,2-dimethoxy-2-phenylacetophenone 0.1-0.7 2,4-ditretbutylortoquinone 0.001-0.006 octylmethacrylate  8-42 oligocarbonatemethacrylate 2-8 oligourethanemethacrylate balance. Also proposed are a method for making an elastic intraocular lens in which the aforesaid compounds are used as the initial components, and an elastic intraocular lens produced by this method.

Abstract: There is provided a photocurable resin composition comprising (A) an urethane acrylate having three or four acrylate groups in the molecule, (B) a radical polymerizable compound different from the above urethane acrylate; and (C) a photopolymerization initiator, the weight ratio of the urethane acrylate (A) to the radical polymerizable compound (B) being 80:20 to 10:90; and a production process thereof. The said photocurable resin composition can provide moldings and stereolithographed objects having excellent dimensional accuracy with a small volume shrinkage factor at the time of photo-curing and excellent heat resistance with a high thermal deformation temperature as well as excellent transparency and mechanical properties such as tensile strength.

Abstract: Thermal transfer articles of the invention comprising a carrier, optionally a release layer, a color layer releasably adhered thereto, and optionally an adherence layer on the bottom side of the color layer. Also graphic imaging compositions and methods for thermal transfer using such articles and compositions and graphic articles made by such methods. The transfer articles 1) exhibit thermoplastic, low cohesive properties during transfer such that good image resolution and transfer is achieved and 2) are radiation crosslinked after transfer such that a durable image is formed.

Abstract: A monomer useful in the formulation of a radiation curable coatable composition comprises (a) polyfunctional isocyanurate having at least three terminal reactive groups reacted with (b) hydroxyalkyl acrylate and (c) tertiary amine alcohol in a molar ratio of a:b:c of about 1:1-2.5:0.5-2, wherein b+c is at least 3 and no greater than the total number of terminal reactive groups of (a). The monomer is included in a radiation curable coatable composition suitable for use as a floor finish and in a floor finishing system comprising the foregoing coatable composition with a primer. A method for the treatment of a substrate using the floor finish and the floor finishing system is also described.

Abstract: A photosensitive resin, process for its use, and printing plates formed thereby are disclosed wherein the photosensitive resin comprises (i) a polyurethane prepolymer which is the reaction product of at least one polyether diol having olefin unsaturation equal to or less than 0.01 meq/gm, at least one diisocyanate, and a hydroxy-functionalized (meth) acrylate, (ii) at least one monomer and (iii) at least one photoinitiator.

Abstract: An optical glass fiber coating composition comprising: (A) a urethane (meth)acrylate polymer, (B) a (meth)acrylate compound represented by the following formula (1), go wherein R1 is a hydrogen or a methyl group (C) a reaction diluent, and (D) a polymerization initiator. The composition has superior storage stability over a long period of time and, at a cured state, exhibits excellent UV resistance, heat resistance, yellowing resistance, and oil resistance.

Abstract: The present invention relates to urethane acrylates, which may be cured with high-energy radiation, in which the urethane acrylates are the reaction product of a) a polyisocyanate component containing 20 to 100 mole %, based on the moles of the polyisocyanate component a), of iminooxadiazine dione group-containing polyisocyanate trimers corresponding to formula A  wherein R1, R2and R3 are the same or different and represent linear or branched, C4-C20 (cyclo)alkyl groups and X is the same or different and represents isocyanate groups or isocyanate group-containing radicals that also contain iminooxadiazine dione, isocyanurate, uretdione, urethane, allophanate, biuret or oxadiazine trione groups, wherein R1, R2 and R3 are attached to a nitrogen atom, with b) an alcohol component containing at least one monobasic, hydroxy-functional, linear or branched C1-C12 alkyl ester of (meth)acrylic acid.

Abstract: Radiation-curable inner and outer primary optical fiber coatings are disclosed having both fast cure speed and reduced rates of yellowing. The compositions comprise particular photoinitiators and UV absorbers which are used in amounts to provide the combination of properties. The UV absorber can have ethylenic unsaturation. Outer primary coatings can be formulated to screen inner primary coatings and have fast cure speed.

Abstract: Disclosed herein is a game ball, such as a golf ball, having an indicia formed from a UV curable ink containing aluminum trihydroxide (ATH) filler. The ATH improves pad transfer of the ink. An ink composition suitable for pad printing, and a method for applying an indicia to a game ball also are disclosed. The UV curable ink has excellent pad transfer properties, and good durability.

Abstract: A liquid curable resin composition exhibiting superior storing stability and suitable for use as a material for optical fiber ribbon matrix, a bundling material, and a material for up-jacketing fibers. The composition contains a first polydimethylsiloxane compound which contains (i) at least two urethane bonds, (ii) an unreactive organic group attached to at least one end of the first polydimethyl-siloxane, and (iii) a (meth)acrylol group attached to at least one end of the first polydimethylsiloxane, and a second polydimethylsiloxane compound which contains (i) at least two urethane bonds and (ii) an unreactive organic group attached to at least one end of the second polydimethylsiloxane, and optionally a third polysiloxane compound which does not contain urethane bonds.

Abstract: A coated optical fiber comprising a drawn glass fiber, and a primary coating and a secondary coating which are formed by photo-curing primary and secondary coating resins simultaneously applied to an outer periphery of the glass fiber, wherein an adhesion force S (g/cm) at an interface between the primary coating resin after curing and the glass fiber is at least {fraction (1/13)} ((g/cm)/° C.) with respect to a glass transition temperature Tg (° C.) of the secondary coating resin after curing.

Abstract: The invention relates to moulded ophthalmic articles, especially contact lenses, which are obtainable by cross-linking a prepolymer which is the copolymerization product of (a) at least one polyalkylene glycol of the formula (1): HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --(CHY.sub.3 --CHY.sub.4 --O).sub.p --H or (1'): HO--[(CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --O--)].sub.q --H, (b) at least one polyhydroxy compound selected from the group consisting of (I) a linear or branched aliphatic polyhydroxy compound of the formula (2): R.sub.1 --(OH--).sub.x or a polyether polyol or polyester polyol derived therefrom, and (ii) a cycloaliphatic polyol selected from the group polyhydroxy-C.sub.5 -C.sub.8 -cycloalkane and unsubstituted mono- or disaccharide, (c) at least one di- or polyisocyanate of the formula (3): R.sub.2 --(NCO).sub.

Abstract: This invention discloses a radiation curable coating composition which is comprised of (1) a crosslinked polymeric resin which is comprised of repeat units which are derived from (a) at least one member selected from the group consisting of acrylate monomers and vinyl aromatic monomers and (b) a crosslinking monomer; (2) an acrylate diluting monomer; and (3) a photocatalyst.

Abstract: New betaketosulfonic derivatives, the process for their preparation, the photopolymerizable systems containing the same and their application as polymerization photoinitiators for inks, and particularly for inks having high content of pigments are described.

Abstract: A resin composition for stereolithography and a process for producing a three-dimensional object using the same. The resin composition comprises (1) a liquid photohardenable resin composition containing at least one of photo-polymerizable compounds and a photosensitive polymerization initiator, and (2) at least one of radiation energy absorbers in an amount of from 0.001 to 1.0% by weight based on the total amount of the liquid photohardenable resin composition (1).

Abstract: A substantially water-free, water-washable, energy-curable composition includes an epoxy oligomer and/or urethane oligomer having at least two ethylenically unsaturated moieties, at least one alkoxylated polyol monomer having at least two ethylenically unsaturated moieties and capable of being copolymerized with the oligomer, and a surface active agent capable of being integrated into the molecular structure of the cured polymer and further capable of rendering the uncured composition dispersible in water. Optionally, the composition can contain a photoinitiator. The composition is self-dispersible in water and is especially suitable for use as a coating material for a printing screen.

Abstract: Disclosed herein is a game ball, such as a golf ball, having an indicia formed from a UV curable ink containing aluminum trihydroxide (ATH) filler. The ATH improves pad transfer of the ink. An ink composition suitable for pad printing, and a method for applying an indicia to a game ball also are disclosed. The UV curable ink has excellent pad transfer properties, and good durability.

Abstract: In a battery in which a metallic battery case for accommodating electricity-generating elements also serves as an electrode, a visible-light or near-infrared-light curing resin is used for providing a coating to insulate an end face and a peripheral edge portion of an opening portion of the battery case or a gap between a positive electrode and a negative electrode. The visible-light or near-infrared-light curing resin excels in a depth-curing characteristic as compared with a conventional ultraviolet curing resin, and cures well even up to a portion such as an insulating seal of a battery where a light-receiving port is light and the light is difficult to reach. Hence, the visible-light or near-infrared-light curing resin is prevented from becoming peeled off and provides a reliable insulting characteristic.

Abstract: A radiation-curable composition for optical fiber coatings comprising about 10 wt. % to about 90 wt. % of at least one radiation-curable oligomer (A), about 10 wt. % to about 90 wt. % of at least one radiation-curable monomer diluent (B), and an effective amount of at least one photoinitiator (C) represented by formula (1): ##STR1## wherein Ar.sup.1 to Ar.sup.3 are aromatic groups which may have one or more substitution groups.

Abstract: A photocuring resin composition for orthodontics is disclosed, comprising:(a) 5.about.50% by weight of a urethane bond-free (meth)acrylate having an average molecular weight of 100.about.300 and having at least one unsaturated double bond;(b) 10.about.60% by weight of a urethane bond-containing (meth)acrylate having an average molecular weight of 300.about.5,000 and having at least one unsaturated double bond;(c) 5.about.30% by weight of a crosslinked polyurethane powder;(d) 10.about.50% by weight of an inorganic filler; and(e) 0.03.about.3% by weight of a photocuring initiator.

Abstract: Radiation-curable preparations comprise at least one polymer which has ethylenically unsaturated double bonds and are used for the coating of mineral moldings.A process for coating mineral moldings, and also mineral moldings which have a coating cured by radiation, are also described.

Abstract: The invention relates to the use of reactive prepolymeric organic compounds, containing structural units having at least one readily abstractable hydrogen with a bond energy of not more than 397 kJ/-mol and having at least one ethylenic double bond, for crosslinking, with or without free-radical initiators, by means of heat, high-energy radiation or heat and high-energy radiation.

Abstract: A curable composition is disclosed that is useful for securing color coded optical fibers in a matrix of an optical fiber cable. The matrix material can be stripped from the individual fibers without removing the color coding associated with the individual fibers. The matrix material is also resistant to solvents used in the stripping process.

Abstract: A bonded body uses an adhesive having high water resistance to realize an adhesive-fixed structure having excellent waterproof properties and exhibiting relatively low changes in properties of the adhesive layer over time. The adhesive-fixed body of the present invention can be obtained by bonding and fixing a body and a glass cover as exterior pairs of a watch with an adhesive layer. The adhesive of the invention can be a curable adhesive containing 100 parts by weight of prepolymer resin having polytetramethylene oxide as a main chain and methacryl groups or acryl groups at both ends of the main chain or in side chains, 50 to 300 parts by weight of at least one selected from acrylic monomers or methacrylic monomers comprising isobornyl acrylate, isobornyl methacrylate or a mixture thereof, and a coupling agent.

Abstract: A method for preparing a film suitable for use as the light-modulating unit of an SPD light valve, which film comprises a cross-linked polymer matrix having droplets of a liquid light valve suspension distributed in the cross-linked polymer matrix. The light valve suspension comprises particles suspended in a liquid suspending medium. The method comprises admixing a UV cross-linkable liquid oligomer or polymer and the liquid light valve suspension, emulsifying the resulting admixture to form an emulsion of the liquid light valve suspension in the UV cross-linkable liquid oligomer or polymer, and cross-linking the UV cross-linkable liquid oligomer or polymer while the mixture is in the form of a thin layer of the emulsion by exposing the layer to UV radiation or to an electron beam, such that the film is not damaged due to such exposing. The oligomer or polymer and the particles are free of deleterious effects on one another.

Abstract: Described is a preferred UV curable coating composition comprising (exclusive of any solvent present): (a) about 5% to 90% by weight of an acrylated aliphatic urethane having a molecular weight of about 500 to 2000 and formed by the reaction of a multifunctional acrylate with a molecular weight of about 190 to 500 and containing at least three polymerizable unsaturated groups per molecule, with an aliphatic urethane based on a polymer of alkyl carbomonocycle diisocyanate with alkanepolyol polyacrylates; (b) about 5% to 30% by weight of a multifunctional acrylate having a molecular weight of about 170 to 1000 and containing at least two polymerizable unsaturated groups per molecule; and (c) a photopolymerization initiator and/or sensitizer. Also described are preferred processes and coated articles involving the preferred coating compositions.

Abstract: The invention relates to a solvent-free radiation curable, optical glass fiber coating composition containing:a) a urethane oligomer having a functional group capable of polymerization in the presence of actinic radiation, with an average functionality of at least about 1.2, having a vinyl addition polymer as backbone.b) a urethane compound having a functional group capable of polymerization in the presence of actinic radiation, with an average functionality of at least about 1, containing an organic moiety having about 5 or more carbon atoms as backbone.c) a reactive diluent.Furthermore, the invention relates to a solvent-free method for producing a solvent-free, radiation curable urethane oligomer composition.

Abstract: Ultraviolet radiation curing of inks on game balls, golf balls and the like is disclosed. Production inks, logo inks and methods for forming production prints and logos on golf balls, game balls and the like are disclosed. To form an ultraviolet radiation curable water-insoluble production ink, at least an adhesion promoting component is added to an ink base.

Abstract: A method of generating reactive species which includes exposing a polymolecular photoreactor to radiation, in which the polymolecular photoreactor comprises a wavelength-specific sensitizer associated with a reactive species-generating photoinitiator. The sensitizer absorbs energy and transfers the absorbed energy to the photoinitiator which in turn, generates reactive species. The wavelength-specific sensitizer is adapted to have an absorption wavelength band generally corresponding to an emission peak of the radiation. The radiation to which the polymolecular photoreactor is exposed generally will have a wavelength of from about 4 to about 1,000 nanometers. Thus, the radiation may be ultraviolet radiation, including near ultraviolet and far or vacuum ultraviolet radiation: visible radiation: and near infrared radiation. Desirably, the radiation will have a wavelength of from about 100 to about 900 nanometers.

Abstract: The present invention relates to an acrylicized polyetherpolyol that consists of an ethoxylated polyol having a molecular weight of from 600 to 1000, preferably from 700 to 900, which is esterified with acrylic acid.

Abstract: An ultraviolet curable clearcoat composition comprising (exclusive of any solvent present): (a) about 30% to about 90% by weight of an acrylated aliphatic urethane having a molecular weight of about 1200 to 2600 and formed by the reaction of a multifunctional acrylate with a molecular weight of between about 110 and about 500 with an aliphatic urethane based on a polyether and having a molecular weight of about 800 to about 2200; (b) about 15% to about 70% by weight of a multifunctional acrylate having a molecular weight of about 170 to about 1000 and containing at least two polymerizable unsaturated groups per molecule; and (c) a photopolymerization initiator and/or sensitizer. Also described are preferred processes and clearcoated articles involving preferred clearcoat compositions.

Abstract: The use of a phosphine oxide photoinitiator enables the effective curing of a polymerizable acrylate formulation despite the incorporation of a high concentration of a fluorescing agent, thereby facilitating, and enhancing the efficiency of, evaluation of the cured deposit utilizing its fluorescent response.

Abstract: Provided is a radiation-curable, glass optical fiber coating composition which when suitably cured exhibits resistance to attack from hydrocarbon gel cable filing material. The composition containsabout 10 to about 90% by weight of a first radiation-curable oligomer;from 0 to about 40% by weight of a reactive diluent;from 0 to about 40% by weight of a photoinitiator;from 0 to about 10% by weight of a pigment; andabout 10 to about 90% by weight of a second radiation-curable oligomer according to the following formula:R.sup.1 -L.sup.1 -C.sup.1 -L.sup.2 -R.sup.2 (1)where:R.sup.1 and R.sup.2, independently, each represent a radiation-curable functional group;L.sup.1 and L.sup.2, independently, each represent an alkyleneoxy chain having from about 2 to about 40 carbon atoms, wherein L.sup.1 and L.sup.2 are linked to C.sup.1 through an oxygen atomC.sup.1 comprises a hydrocarbon having from about 5 to about 40 carbon atoms and containing at least one cyclic group.

Abstract: The invention provides a photocurable resin composition which inhibits the deactivation of a bisacylphosphine oxide-series photopolymerization initiator and is useful for coating optical fibers. The photocurable resin composition comprises (A) a polyurethane (meth)acrylate oligomer, (B) an ethylenically unsaturated compound, (C) a bisacylphosphine oxide-series photopolymerization initiator, and (D) a tertiary amine and no tin component. Incorporation of the component (D) inhibits the decomposition and deactivation of the component (C). The component (A) may contain an aliphatic C.sub.14-40 polyol (hydrogenated dimerdiol, 12-hydroxystearyl alcohol) as a polyol component. This resin composition is used for a primary coating of a glass fiber or an indirect coating of an optical fiber through the primary layer, the coating layer being cured by light irradiation to provide an optical fiber coated with the resin composition.

Abstract: Aqueous coatings for the multi-layer painting of motor vehicles based on one or more binders and optionally crosslinking agents, pigments and/or fillers, paint industry additives and/or solvents, which contain as binder an aqueous dispersion based on polyurethane/polymer hybrid polymers having a numerical average of the molar mass (Mn) of 8000 to 1500000, a ratio by weight of polyurethane to polymer content of 0.05:1 to 50:1, a hydroxyl number of 0 to 150 mg KOH/g, based on solid resin, hydroxyl groups bound to silicon not being included when calculating the OH number, and an acid number of 1.5 to 40 mg KOH/g, based on solid resin, and a content of 0.5 to 150 mmole of silicon per 100 g of solid resin in the form of siloxane bridges (--Si--O--Si--) bound into the polyurethane content and/or in the form of silanol groups bound to the polyurethane content.

Abstract: A curable underfill encapsulant composition, suitable for use in semiconductor packaging, comprises one or more mono- or polyfunctional maleimide compounds, or one or more mono- or polyfunctional vinyl compounds other than maleimide compounds, or a combination of maleimide and vinyl compounds, with a free radical curing agent, and optionally, one or more fillers.