Recent developments in radiation curing in the USA

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Radiation curing activities in the USA continue to focus strongly on the use of both UV and EB for the polymerization of silicone release coatings on paper and film. The high speeds of cure (200 m/minute) achievable at “room temperature” continue to make this the process of choice for the siliconization of both film paper. Some of the process difficulties peculiar to this chemistry will be discussed.The success of the multi-color lithographic printing of web using single station electron curing has resulted in a major market for electron processors. The aesthetic and physical properties of the overprint varnishes used in this application are important and will be discussed. The relatively high costs of both the inks and varnishes will probably limit this application to folding carton use for foodstuffs and high quality products, with UV continuing to dominate in lower speed, less demanding applications.The application of electron initiated graft modification of polymer materials, particularly for biological/medical device application, is showing a good rate of development as is the use of selective treatment of materials for functional modification of packaging films, particularly for gas permeability control. Some examples of these applications will be reviewed.Continued work with “deep” curing or vulcanization of composite structures, particularly in the elastomers field, will be discussed with a brief review of the continuing growth of electron processing in this industry, particularly for tires and roofing products.

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... Compared to ultraviolet (UV) curing, e-beam irradiation has advantages including energy savings, curing time, crosslinking of deeply pigmented dyes, and solvent-free systems (Läuppi, 1990). Nonetheless, the curing process can be combined with UV irradiation, demonstrating e-beam versatility toward combination of polymers that crosslink under e-beam or that require UV (Nablo, 1990). ...
Radiation technology has been applied to develop a plethora of new materials, now in direct commercial use throughout the world. Materials processing and nanomaterials development directly benefit from the use of radiation. Radiation commonly used in metallurgic, ceramic, food, pharmaceutical and electronic industries include electrons, high energy ions in plasmas, neutrons and gamma. These are selected to introduce atomic lattice defects and change mechanical properties, implant ions and atoms to tailor electronic bandgaps in semiconductors and insulators, prepare coatings, create pores for selective filtration membranes, and change synthetic and natural polymer properties in the plastics and wood industries. Radiation also finds applications in the quality control in sheet and packaging material manufacturing, measuring solid and fluid levels in the food industry, and also finds uses in food, pharmaceutical and in the preservation of historical and archeological artifacts as an effective and safe antimicrobial treatment.
... Radiationcurable coating systems comprise mainly of ultra violet (UV), electron beam (EB), infra-red (IR), radio-frequency and microwave cured systems. UV/EB is characterised by bond breakage and subsequent polymerisation resulting from electronic excitation or ionization (Sam, 1990;Garnett, 1995). The majority of radiation curing work is devoted to UV curing (Decker, 1996;Davidson, 1999). ...
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Purpose Urethane Acrylate Oligomer with 100% solids was synthesised and characterised in order to study the application in electron beam curing with varying ratio of Trimethylol propane triacrylate (TMPTA). The purpose of this paper is to study effect of TMPTA addition on the crosslink density and different coating properties. Design/methodology/approach Polyester polyol was synthesised by reacting single diacid, adipic acid (AA), with Pentaerythritol (PENTA) and 1,6‐hexanediol (HD). Further, Urethane acrylate resin was synthesised by using Isophorone diisocyanate (IPDI), hydroxy ethyl acrylate (HEA) and Polyester polyol. The polyester polyol and urethane acrylate oligomer were characterised by 1H NMR, 13C NMR, FTIR and GPC. Further, TMPTA was added as a crosslinker to the urethane acrylate oligomer and cured by electron beam radiation. The cured UA films having varying concentration of TMPTA were employed to evaluate thermal property, contact angle analysis, mechanical and chemical properties. Findings The obtained results showed improvement in their chemical properties, mechanical properties, thermal properties and water contact angle at 20% of TMPTA iconcentration. The TMPTA also reduced the dose required for the curing. Research limitations/implications The resin can be synthesised from different isocyanates as TDI, MDI and HMDI, etc. The study can also be done with different multi or mono functional monomers such as methacrylate, hexanediol diacrylate, ethylene glycol diacrylate, etc. Practical implications The paper provides the better solution to reduce the cost of the electron beam radiation required for the curing. Social implications The method presented in the paper could be very useful for controlling environmental pollution; as the conventional method of curing releases volatile organic compounds (VOC). Originality/value In this paper, urethane acrylate and TMTPA cured with electron beam are shown to offer good coating properties. A high‐solid urethane acrylate coating would find numerous industrial applications in surface coatings.
The goal of this study was to synthesize epoxy acrylate monomers and evaluate these materials for UV and electron-beam curing. An epoxy acrylate resin for UV curing consists of a reactive oligomer, reactive monomer diluents, and a photo-initiator. The physical properties of the cured polymer are mainly determined by the reactive oligomer. The reactive monomer diluents play very important roles not only in modifying the physical properties of the reactant resin, but also improving the processability by decreasing the viscosity. A bisphenol-A type epoxy acrylate and a reactive diluent of glycidyl methacrylate (GMA-MAA)/acrylate (GMA-AA) were synthesized and the structures were confirmed by 1H-NMR and FT-IR analyses. It was found that the viscosity of epoxy acrylate/GMA-AA mixture could be controlled during the synthetic procedure. The radiation curing effect for the electron beam as well as UV was studied comparatively. Also, the reactive diluent with mono-functional group lowers the modulus of elasticity of UV curable epoxy acrylate, while multi-functional reactive diluent increases the modulus of elasticity as well as curing rate.
The effect of multifunctional monomers or oligomers (MFM/O) additives on electron beam (E-beam) radiation induced crosslinking of poly (styrene-block-isoprene/butadiene-. block-styrene) (SIBS) was studied. Ten types of MFM/O were investigated, including trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), triallyl cyanurate (TAC), polybutadiene diacrylate (PB-diacrylate), ethylene glycol dimethylacrylate (EGDMA), butylene glycol dimethacrylate (BGDMA), 1,2-polybutadiene. The effects of MFM/O concentration and E-beam radiation dose on properties of SIBS were studied including tensile strength, elongation-at-break, modulus, gel content, equilibrium swelling and crosslink density. TMPTA significantly improved the tensile modulus and crosslink density of SIBS. SIBS with TMPTMA and TMTPMA with inhibitor showed a 50% increase in tensile strength. The solubility of MFM/O in SIBS was also investigated by a selective swelling method. The MFM/O were found to be soluble in both phases of SIBS. The viscosity of SIBS with methacrylate type MFM/O was stable at 200. °C.
The possibility of the single-use syringes sterilization inside the standard production packs was tested using the accelerator type ILU-6 with the energy up to 2.5 MeV and the electron beam power up to 20 KW. The syringes were placed vertically (along the beam direction), and the irradiation was made from two sides. The dosimetry measurements were provided using the film dosimeters and the special bacterial cultures. The results show that the dose ununiformity inside the volume of the syringes does not exceeds +/-15%. The practical results of these investigations are two installations for the single-use syringes sterilization with the productive rate of 100,000 units per hour. These installations are now under construction. The equipment layout variant and some economical are now of the process are given. The usage of the compact accelerator with the energy up to 5 MeV and the beam power up to 20kW is regarded for the sterilization of the wide scope of the medical devices as another variant.
Ionizing radiation has been found to be widely applicable in modifying the structure and properties of polymers, and can be used to tailor the performance of either bulk materials or surfaces. Fifty years of research in polymer radiation chemistry has led to numerous applications of commercial and economic importance, and work remains active in the application of radiation to practical uses involving polymeric materials. This paper provides a survey of radiation-processing methods of industrial interest, ranging from technologies already commercially well established, through innovations in the active R&D stage which show exceptional promise for future commercial use. Radiation-processing technologies are discussed under the following categories: cross-linking of plastics and rubbers, curing of coatings and inks, heat-shrink products, fiber–matrix composites, chain-scission for processing control, surface modification, grafting, hydrogels, sterilization, natural product enhancement, plastics recycling, ceramic precursors, electronic property materials, ion-track membranes and lithography for microdevice production. In addition to new technological innovations utilizing conventional gamma and e-beam sources, a number of promising new applications make use of novel radiation types which include ion beams (heavy ions, light ions, highly focused microscopic beams and high-intensity pulses), soft X-rays which are focused, coherent X-rays (from a synchrotron) and e-beams which undergo scattering to generate patterns.
The curing of elastomeric materials by electron beam (EB) radiation generates carbon-carbon bonds between molecules without using chemical catalysts, for example, peroxides. Most elastomers, other than butyl rubber, can be cured by this method. Its advantages over other methods of curing include versatility, technical superiority in specific cases, and lower unit cost. Commercial applications are well-developed in the manufacture of wire and cable, rubber tires, and heat-shrink products, among others, and prospective applications are under active development in, e. g. , single-ply membrane roofing material.
Modern electron processors offer high speed (high dose-rate) curing of low viscosity liquid coatings so that surface modification of films becomes practicable. A process has been developed for grafting vinyl monomers to polyolefin film surfaces with the aid of functional silane primers using electron initiated polymerization. A one step process is described using a pre-dried vinylbenzylamine siloxane primer, overcoated with the functional monomer, in this case acrylonitrile. Infrared analysis, tape tests, and gravimetric analysis after washing and flexing have shown the electron initiated cure grafts the primer to the film surface and simultaneously causes the copolymerization of the monomer-primer system.
A method is described for producing a resin-bonded nonwoven fabric. The preparation involves forming a fibrous web annealing it and compressing it to provide fiber to fiber contact. A polymerizable binder is applied to the fibrous web which is then treated by ionizing radiation to produce the material. 9 figures, 3 drawing.
Innovative and Unique Applications of Radiation Cured Silicone Release Coatings Radiation Curing of Elastomers The Radiation Chemistry of Elastomers and its Industrial Applications
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Bickford, R.H. and I. Jachmann (1988). Innovative and Unique Applications of Radiation Cured Silicone Release Coatings, Proc. RadTech '88, April 24-8, New Orleans, LA, 569-575; RadTech Internatlonal, 60 Revere Drive, Suite 500, Northbrook, IL 60062, USA. Bly, J.H. (1983). Radiation Curing of Elastomers, Journal Ind. Irr. Tech. ~, i, 51. Bohm, G.G.A. and J.O. Tveekrem (1982). The Radiation Chemistry of Elastomers and its Industrial Applications, Rubber Chemistry and Technology 55, 576.
Static Dissipative Rigid Plastic Sheets from EB Curing
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Keough, A.H. (1988). Static Dissipative Rigid Plastic Sheets from EB Curing, Proc. RadTech '88, April 24-28, New Orleans, LA, 324; RadTech International, 60 Revere Drive, Suite 500, Northbrook, IL 60062 USA.
Developments in Product Handling for Selfshielded Electron Processing
  • Nablo
Nablo, S.V., M. Fishel and B.S. Quintal (1988). Developments in Product Handling for Selfshielded Electron Processing", RadTech '88, New Orleans, LA, April 24-28 (ESI TR-157).
Engineers Assoc. Pin
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Soc. Mfg. Engineers Assoc. Pin. Proc. of SME, One SME Drive, P.O. Box 930, Dearborn, MI 48121. Tanny G.B. (1984).
Innovative and Unique Applications of Radiation Cured Silicone Release Coatings
  • Bickford
Radiation Curable Epoxysilicone Coatings, ibid
  • R P Eckberg
Tego® Silicone Acrylates RC for Release Coatings
  • Weitemeyer
Electron Beam Cylinder Wipe Intaglio Inks
  • O'Brien