Amount Of Residual Monomer Research Articles

Preparation and Visible Light Polymerization of Triethyleneglycol Acrylate Methacrylate

Triethyleneglycol acrylate methacrylate (A-M) was prepared by reaction of triethyleneglycol with methacryloyl chloride and then with acryloyl chloride, to create a new monomer with both excellent photopolymerization ability and mechanical properties of the wet photocured polymer. The visible light polymerization ability of A-M was compared with the corresponding dimethacrylate (M-M), the diacrylate (A-A) having a triethyleneglycol chain, and an equimolar mixture of M-M and A-A with attention to the amounts of residual monomers and pendant C=C double bonds in the polymers. The polymerization rate of A-M was the lowest. When irradiation was extended, the amount of residual A-M became comparable to M-M and the concentration of pendant C=C double bonds in poly (A-M) became lower than that in poly (M-M). The polymerization rate of A-A was faster than that of M-M in homophotopolymerization. M-M was incorporated into polymer chain preferentially in the equimolar mixture of M-M and A-A and the concentration of A-A became higher in residual monomers.

Ｂｉｓ‐ＧＭＡ系光重合型コンポジットレジンの水中における摩擦摩耗

Recently, Bis-GMA-Tri-EDMA based composite resins have been widly used as a restoration material for tooth. However, it has been pointed out that the mechanical properties of these resins, such as elastic modulus and frictional wear, are obviously inferior to those of metal materials. Therefore, the author examined the relationship between the amount of residual monomer, which deteriorates the mechanical property of the cured material, and the frictional wear of its material.All specimen were immersed into distilled water (37°C) for a constant period after polymerization, according to the experimental conditions, and each measurement was also carried out in water at a temperature of 23±0.5°C. The amount of residual monomer in the cured resins decreased markedly with a time after the polymerization manipulation and attained the minimum value of the residual monomer at a week after that.On the other hand, the surface hardness of cured resins increased considerably as the time proceeds, and an adequate negative correlation was estimated between the amount of residual monomer and surface hardness of the cured resin (r=-0.96). In addition, a significant correlation was also estimated between the amount of residual monomer and the magnitude of the frictional wear loss of the cured resin (γ=0.87). It was seen that the frictional wear loss diminished significantly according to the decrease of residual monomer and to the increase of filler content to the resin.

光重合型硬質レジンの重合性に関する研究 ＩＩＩ オペークレジンの接着強さへの影響について

New light-curable adhesive opaque resins were prepared using 4-methacryloxyethyl trimellitate anhydride (4-META), triethylene glycol dimethacrylate (TEGDMA), di (methacryloxyethyl) trimethylhexamethylene diurethane (UDMA) and titanium dioxide. The purpose of this study was to investigate the relation between the conversion of opaque resins and the bond strengths. Amounts of residual monomers in the bulk-photo-polymerized resins with various compositions were determined by high-performance liquid chromatography. Shear bond strengths of light-cured opaque resins joined to surface-treated Au-Ag-Pd alloy were measured with various primers, components and curing conditions. Photo-polymerized resins which contained mehyl methacrylate (MMA) showed lower conversion compared with bifunctional methacrylate resins. Favorable shear bond strengths were obtained from TEGDMA/UDMA based opaque resins. The opaque resins without MMA bonded strongly to heated and 4-META primed Au-Ag-Pd alloy and 22-23 M Pa strengths were maintained after 20,000 thermocycles. The results revealed that the conversion of MMA with photo-initiater system was lower than that of bifunctional methacrylate, which affected bond strength of opaque resins.

Polymerization of multifunctional methacrylates and acrylates

The cross-linking reaction of 15 dimethacrylates, one trimethacrylate and five diacrylates was studied by means of differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to investigate the relationship between the polymerization characteristics and the chemical structure of these monomers. The amount of pendant double bonds (Dp) and the efficiency of cross-linking (Ec) were calculated from both the extent of polymerization (Ep) and the amount of residual monomer (Rm) obtained by DSC and HPLC analyses, respectively. The Ep and Ec values of various monomers increased with an increase in the number of chain members between the functional groups, while Rm and Dp values decreased. The dimethacrylates consisting of aliphatic chains polymerized more readily than those containing aromatic units. High Ep was obtained in the aliphatic dimethacrylates and diacrylates with more than eight chain members and the aromatic dimethacrylates with more than 20 chain members among the monomers examined. These results depend presumably on the flexibility of the functional groups in the polymer network. With most dimethacrylates and diacrylates, high Ep was also observed in thermal scanning polymerization compared to isothermal polymerization at 90 degrees C. The diacrylates showed a high rate of polymerization compared to the corresponding dimethacrylates.

Clinical Studies on the Heat Curing Methods of Acrylic Resin Dentures

Much, so far, has been reported on the amount of residual monomer in heat curing acrylic resin denture bases, which has supposedly undesirable influence on oral mucosa or on the physical properties of a denture base after curing. These reports, however, mostly have dealt with standardized models and few reported on the basis of casts clinically applicable. Further, in these reports, the methods of conducting examinations usually very in each student: ie. the methods of mixing and curing of monomer and polymer. Most of such models have simplified features, which, unfortunately, makes it impossible to make investigation of the difference in the heat emitted from resin, and also of the influence of different heat thus emitted, on the amount of residual monomer.The present author examined the mixing methods of monomer and polymer by the use of generally employed eduntlos practice casts, which had been completed-from the arrangement of artificial teeth to flasking. This process was for the purpose of obtaining the same condition of the casts which had undergone identical process from mixing to filling of dough-stage resin. The amount of residual monomer and heat inside an acrylic resin denture base was measured on each cast by different curing methods and the following results were obtained:1. The distribution of polymer size was examined among three kinds of resin-Acron, L-resin, and Hircoe-and a fact was obtained that the area of their distribution was less than 130μ. Acron had its most distributed area in from 60μ to less than 70μ, L-resin in from 20μ to less than 50μ, and Hircoe in from 50μ to less than 60μ.2. After surveying monomer and polymer mixing methods of the three cases above mentioned, a tendency was observed that, in order to mix polymer more efficiently, mixing time should be 60 seconds rather than 30 seconds, and that in case of employing vibrators the amount of mixed polymer increased in proportion to the degree of vibration.3. Most efficient mixing ratio of polymer and monomer (P/L ratio) varied from 2:1 to 2.5:1 in Acron and L-resin, and from 2.5: 1 to 3:1 in Hircoe.4. Time duration necessary for reaching dough-like stage was about 20 minutes for Acron, about 15 minutes for L-resin, and about 8 minutes for Hircoe. Time duration after reaching dough-like stage was longest in L-resin, and next came Acron, Hircoe being shortest.5. The author examined the changes in temperature of resin in curing process. With the flask submerged in the water 70°C or 60°C, the temperature of upper and lower dentume bases of the three kinds of resin tended to rise, first at the labial side of anterior area, next the buccal side of posterior area, and then at the lingual side of posterior area showed rise in temperature.6. In the curing process of the upper and lower denture bases of the three kinds of resin, the elapsed time for the temperature inside the flask to reach curing temperature 70°C or 60°C-tended to be shortest in the labial side of anterior area, next the buccal side of posterior are, and then the lingual side of posterior area reached the temperature necessary for curing.7. He next measured the residual monomer in the denture bases which had been completed according to two curing methods, one method being to submerge flask in the water 70°C in temperature for 90 minutes and then into boiling water for 30 minutes (70°C Curing Method hence), and the other to submerge flask in the water 60°C in temperature for 9 hours and then into boiling water for 30 minutes (60°C Curing Method hence). By 70°C Curing Method the amount of residual monomer showed in Acron to be between 0.44 and 0.46%, in L-resin between 0.35 and 0.36%, in Hircoe 0.73 and 0.86%; by 60°C Curing Method, the amount was in Acron between 0.26 and 0.30%, in L-resin between 0.23 and 0.27%, in Hircoe between 0.52 and 0.60%.

Electron Spin Resonance Studies of Photodegradation in Poly(Methylmethacrylate)

The strength of the ESR spectrum produced in poly(methylmethacrylate), PMMA, by exposure of the polymer to ultraviolet light (2537 Å) has been measured as a function of exposure time. The signal strength initially increases and then saturates under continued exposure. It decays when the light is removed. While the time needed to produce saturation depends inversely upon the light intensity it is only slightly affected by changes up to an order of magnitude in the decay rate. It is also observed that, for similar samples, the maximum ESR signal strength obtained is independent of the light intensity. This dynamic behavior strongly suggests that: (1) the ESR spectrum arises from radicals which are produced by the light from a limited number of centers already present in the polymer, and (2) the saturation mainly occurs due to exhaustion of these centers rather than some dynamic equilibrium between the creation and destruction of radicals. Additional experiments were performed in order to identify these centers. In these investigations it was found that the intensity of the ESR signal following irradiation decreases when the amount of residual monomer is descreased. Furthermore, when the monomer of poly (ethyl-α-chloroacrylate), PEαClA, is added to a sample of PMMA which has been purified to remove its own monomer and this sample irradiated, the resulting ESR signal is the one normally associated with photodegradation in PEαClA. These results indicate that the residual monomer molecules are the centers which are converted by the radiation into the free radicals which produce the ESR signal. While no attempt was made to obtain the exact form of the radicals, these results could be consistent with previous suggestions that the ESR spectrum arises from radicals which have the form of the propagating polymer radical.

Synthesis and polymerization of p-tent-butylphenyl methacrylate

1. Previously-undescribed p-tert-butylphenyl methacrylate was synthesized and characterized. 2. It was shown that the mass polymerization of this ester at 60–120° with benzoyl peroxide as initiator proceeds to the extent of 89–90%. 3. It was suggested that the large amount of residual monomer in the final product is to be explained by the presence of a branched substituent in the benzene nucleus and the consequent steric hindrance.