Electron beam effects on polymers: Structure–property behavior of radiation‐cured bis‐GMA

Abstract

SynopsisStructure-property relationships were investigated for the diglycidyl methacrylate derivative of bisphenol-A crasslinked by electron beam irradiation. This material, commonly called bis-GMA, is a viscous liquid a t room temperature which crosslinks to form a glassy network. The major parameters which were systematically varied in this study were radiation dosage, dose rate, aging time after irradiation, and post-cure annealing at higher temperatures. Measurements were conducted to quantify the crasslinking reaction and to characterize the physical properties of the resulting networks. Solvent extraction was done to determine the relative degree of network formation through the equilibrium swelling and the gel weight fraction after drying. Another method utilized FTIR to monitor the disappearance of double bonds as the crosslinking reaction proceeded. To characterize the thermal and physical properties, differential scanning calorimetry (DSC) and dynamic mechanical spectroscopy were utilized. Network density was found proportional to the irradiation dosage, with an upper limit reached above some critical dosage. Over the range of dose rate studied, this variable was not found to influence the degree of cure greatly. The croslinking reaction became diffusion limited as vitrification occurred. These phenomena were discussed in terms of the well-known time-temperature-transformation diagram. Free radicals trapped in these reacting networks due to vitrification exhibited a finite lifetime. Post-curing could be achieved by annealing at a temperature above the Tg of the initially cured network, as shown by the increase of the glass transition temperature from both DSC and dynamic mechanical results. INTRODUCTIONCoating processes have gained prominence in industry for large scale application of adhesives or other formulations onto a substrate (e.g., polymeric, paper, metal, etc.). Formulations have historically consisted of polymeric "binders," surfactants, adhesives, and fillers suspended in solvents. Thermal ovens are widely used to evaporate carrier solvents as well as to initiate crosslinking in reactive systems.More recently, solventless coatings have emerged to significance in industry. Development of solventless coatings using radiation crosslinking was expedited during the 1970s to battle rising energy costs and stiffer pollution standards. This momentum has been carried into the 1980s, as more economical radiation sources are becoming available, and, in many cases, radiation crosslinked materials possess certain desirable physical properties. The purpose of the study was to investigate the structure-property relationships present in a diglycidyl methacrylate of bisphenol-A (bis-GMA) crosslinked by electron beam irradiation. Bis-GMA is a thermosetting resin with a viscosity at room temperature near lo4 P. Its chemical structure is shown in Figure 1 . This potential coating ingredient is one of several that we are investigating in terms of its response to EB radiation.Earlier studies were done by Yilgor et...

Influence of electron beam irradiation on the alloy‐to‐resin bond strength

“…This method can change the mechanical properties of polymers (19). Electron beam irradiation is widely used with polymers like polyethylene, polycarbonate, and polysulphone (10–13). Generally, two types of competing reactions occur with electron beam irradiation: chain linkage or breakage (9, 19–21).…”

“…Therefore, a stronger alloy-resin bond is needed.Since the basic investigations of Charlesby and Ross (9), electron beam irradiation has been known to improve the mechanical properties of polymers. It was demonstrated that ionized irradiation of polyethylene introduces chain linkage, which results in an insoluble and more heat-resistant polymer (10, 11).While irradiated polymers of polyethylene, polystyrene, and polycarbonate have been widely used in industrial products such as cars, machine-bodies, and isolators for years (12,13), dentistry has paid little attention to polymer radiation up to now (14). The present study investigated the influence of postcuring using electron beam irradiation on the alloy-to-resin bond strength after thermal cycling to find a procedure that will make the bond more reliable.…”

“…While irradiated polymers of polyethylene, polystyrene, and polycarbonate have been widely used in industrial products such as cars, machine‐bodies, and isolators for years (12, 13), dentistry has paid little attention to polymer radiation up to now (14). The present study investigated the influence of postcuring using electron beam irradiation on the alloy‐to‐resin bond strength after thermal cycling to find a procedure that will make the bond more reliable.…”

Electron beam effects on polymers: V. Symmetric and asymmetric materials based on the controlled distribution of bis‐GMA into crosslinked nitrile rubber films prior to curing by electron beam radiation

“…Dynamic storage and loss moduli (E' and E " ) , as well as tan 6, were determined as a function of temperature using an Autovibron Dynamic Viscoelastometer. These samples were run from -40-200°C to investigate the thermal transition behavior with a scanning rate of 2"Clmin at a frequency of 11 Hz.…”

Synthesis and properties of ultraviolet‐curable resins via a thio–ene (thiol and allyl) addition reaction

“…There are a great number of articles and patents on photocurable resins, including unsaturated polyester, epoxy acrylate, acrylate or methacrylate, and urethane types 1. An ever growing number of resins that polymerize readily under UV radiation, particularly the very reactive multifunctional acrylates1–4 and methacrylates,5–8 began to be commercialized when the many advantages of this new technology9–12 became apparent. Acrylic oligomer curing with UV radiation is increasing in industrial importance, particularly for coatings of wood, paper, plastics, and tin plates for printing ink.…”