• International Journal of Oral Biology
• /
• v.46 no.4
• /
• pp.184-189
• /
• 2021

When luting indirect restorations with dual-cure resin cement (DCRC), excess cement can be easily removed by performing tack cure of DCRC for a few seconds. The purpose of this study was to evaluate whether different tack cure times affect polymerization shrinkage (PS) of the selected DCRC. One dual-cure resin cement (G-CEM LinkAce, GC) was used for measuring PS in light-cure (LC group), self-cure (SC group), and two tack-cure modes. In the first tack-cure subgroup, tack cure was performed for 1, 2, 3, and 5 seconds, followed by light cure after 2 minutes of remnant removal time in each case (TC-LC groups). In the other tack-cure subgroup, tack cure was performed for the same lengths of time, but followed by self-cure in each case (TC-SC groups). PS was measured by a modified bonded disc method for 1,800 seconds. One-way analysis of variance followed by Duncan's post hoc test was used to determine any statistically significant differences among the test groups (α = 0.05). When the DCRC was self-cured after tack cure, PS was significantly lower than when it was only self-cured (p < 0.05); however, tack cure time did not affect PS (p > 0.05). When the DCRC was light-cured, PS was not affected by tack cure or tack cure time (p > 0.05). Therefore, tack cure within 5 seconds did not negatively affect the final PS when the DCRC was light-cured after cement remnant removal.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.1
• /
• pp.29-35
• /
• 2020

The cure characteristics of three kinds of naphthalene type epoxy resins(NET-OH, NET-MA, NET-Epoxy) with a 2-methyl imidazole(2MI) catalyst were investigated for preparing sheet epoxy molding compound(SEMC) for wafer level package(WLP) applications, comparing with diglycidyl ether of bisphenol-A(DGEBA) and 1,6-naphthalenediol diglycidyl ether(NE-16) epoxy resin. The cure kinetics of these systems were analyzed by differential scanning calorimetry with an isothermal approach, and the kinetic parameters of all systems were reported in generalized kinetic equations with diffusion effects. The NET-OH epoxy resin represented an n-th order cure mechanism as like NE-16 and DGEBA epoxy resins, however, the NET-MA and NET-Epoxy resins showed an autocatalytic cure mechanism. The NET-OH and NET-Epoxy resins showed higher cure conversion rates than DGEBA and NE-16 epoxy resins, however, the lowest cure conversion rates can be seen in the NET-MA epoxy resin. Although the NETEpoxy and NET-MA epoxy resins represented higher cure reaction conversions comparing with DGEBA and NE-16 resins, the NET-OH showed the lowest cure reaction conversions. It can be figured out by kinetic parameter analysis that the lowest cure conversion rates of the NET-MA epoxy resin are caused by lower collision frequency factor, and the lowest cure reaction conversions of the NET-OH are due to the earlier network structures formation according to lowest critical cure conversion.

• Composites Research
• /
• v.27 no.3
• /
• pp.90-95
• /
• 2014

Cure shrinkage during cure process of polymer matrix composites develope residual stress that cause some structural deformation, such as spring-in, spring-out and warpage. The carbon/epoxy prepreg used in this study is Hexply M21EV/34%/UD268NFS/IMA-12K supplied by Hexcel corp. Cure shrinkage and degree of cure measured by TMA(thermomechanical analyzer) and DSC(differential scanning calorimetry). Cure shrinkages are measured by TMA within a temperature range of $140{\sim}240^{\circ}C$ in a nitrogen atmosphere, and degree of cure determined by the heat of reaction using dynamic and isothermal DSC runs in argon atmosphere. As a result, the cure shrinkage is increased dramatically in a degree of cure range between 27~80%. the higher the cure temperature, the lower the degree of cure occurring to begin cure shrinkage.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.219-223
• /
• 2001

The on-line cure monitoring during the cure process of composite materials is important for better quality and productivity. The dielectric sensor for cure monitoring consists of base film and electrodes. Because the characteristic of dielectric sensor for the on-line cure monitoring is dependent on the base material, width and number of electrode, etc, the dielectric sensor should be standardized. And the selection of base film material of sensor is very important. In order to prevent the measuring errors generated from the increase of environmental temperature, the base film material should have stable dielectric constant with respect to environmental temperature. In this study, the newly developed dielectric sensor for cure monitoring was designed and the dissipation factor which is function of degree of cure was measured using the sensor. The relationship between the dissipation factor and degree of cure with respect to environmental temperature was investigated.

• 연구논문집
• /
• s.29
• /
• pp.151-162
• /
• 1999

In general, manufacturing processes of thermosetting composites consist of mold filling and resin cure. The important parameters used in modeling and designing mold filling are the permeability of the fibrous preform and the viscosity of the resin. To consolidate a composite, resin cure or chemical reaction plays an essential role. Cure kinetics. Therefore, is necessary to quantify the extent of chemical reaction or degree of cure. It is also important to predict resin viscosity which can change due to chemical reaction during mold filling. There exists a heat transfer between the mold and the composite during mold filling and resin cure. Cure kinetics is also used to predict a temperature profile inside composite. In this study, a new scheme which can determine cure kinetics from dynamic temperature scaning was proposed. The method was applied to epoxy resin system and was verified by comparing measurements and predictions.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.797-803
• /
• 2001

The on-line cure monitoring of fiber reinforced thermosetting resin matrix composite material was performed for the better quality and productivity during manufacturing. Since the dissipation factor measured by dielectrometry method is dependent on the degree of cure and temperature of resin, in this study, a new method to obtain the degree of cure during on-line cure monitoring for glass/polyester composites was developed by employing a combination function of the temperature and the dissipation factor. Two sensor signals from a K-type thermocouple and an interdigitated dielectric sensor were processed during curing process under various cure cycles. The DSC (Differential Scanning Calorimetry) data was also used for the reference of degree of cure.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.233-236
• /
• 2006

A dilatometer was used to investigate the effect of cure conditions and the presence of filler in an epoxy system. These studies showed shrinkage in the cured epoxy when heating it through the glass transition temperature region. The magnitude of the shrinkage, related to stress build up in the epoxy during curing, was influenced by the processing conditions, filler presence and the nature of the mold used to contain the resin. Cure and cyclic cure at a lower temperature, prior to a post cure, decreased the magnitude of observed shrinkage. Cure shrinkage decreased with number of cyclic cure. Post cured samples outside the mold led to less shrinkage compared with sample in the mold. And sample containing kaolin filler showed less shrinkage than unfilled sample.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.2
• /
• pp.320-324
• /
• 2002

Binary cure system is composed of different two cure accelerators, which can cause a synergy effect to delay the scorch time and to increase the cure rate. In this study, binary cure systems between 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)-hexane (DBTH) and benzothiazole sulfenamides were investigated using carbon black-filled natural rubber compounds. N-Cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), and 2-(morpholinothio) benzothiazole (MOR) were employed as benzothiazole sulfenamides. The binary cure systems show scorch safty at high temperature. The binary cure systems have faster cure rate and better reversion resistance than the single cure system of the benzothiazole sulfenamides. DBTH is found to be more effective to decrease the viscosity of a compound than the benzothiazole sulfenamides. Physical properties of the vulcanizates with the binary cure system are better than those of the vulcanizates with the single one.

• Elastomers and Composites
• /
• v.51 no.3
• /
• pp.212-217
• /
• 2016

Influence of poly(ethylene-co-vinyl acetate) (EVA) types and cure systems on cure characteristics of foaming EVA compounds were investigated. Three kind EVAs with different VA contents were employed. Influence of triallyl cyanurate (TAC) and dicumylperoxide (DCP) content on the cure characteristics were examined. The minimum torque ($T_{min}$) and delta torque (${\Delta}T$) decreased as the VA content increased. The ${\Delta}T$ was increased by adding TAC and by increasing the DCP content. For the foaming EVA compounds without TAC, the cure times such as the minimum cure time ($t_{min}$), scorch time ($t_2$), and optimal cure time ($t_{90}$) did not show a specific trend according to the DCP contents. For the foaming EVA compounds containing TAC, the cure times decreased as the DCP content increased. From the experimental results, it was found that efficienct DCP/TAC ratio for improvement of the crosslink density was 1.1~2.0.

• Elastomers and Composites
• /
• v.48 no.2
• /
• pp.161-166
• /
• 2013

Thermal degradation behavior of chlorine cure-site ACM and carboxylic cure-site ACM rubbers was studied by non-isothermal TGA thermal analysis. Carboxylic cure-site ACM rubber exhibited comparatively more thermally stable than chlorine cure-site ACM, showing higher peak temperature, at which maximum reaction rate occurred. Activation energies from Kissinger method were calculated as 118.6 kJ/mol for the chlorine cure-site ACM and 105.5 kJ/mol for the carboxylic cure-site ACM, showing similar values from Flynn-Wall-Ozawa analysis over the conversion range of 0.1~0.2. From the analysis of the reaction order change, both samples seemed thermally decomposed through the multiple reaction mechanism as is the common rubber materials.