Dynamic Mechanical Properties of a Visible Light Curable Urethane Dimethacrylate Based Dental Resin

Abstract

ABSTRACT:The purpose of this study was to evaluate dynamic mechanical properties of urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) based dental resin. Dynamic mechanical properties of a visible light (λ = 400-500 nm) curable UDMA/TEGDMA (70:30 in wt%) resin were investigated for specimens uncured, light-cured for 40 s, and heated to 175• C subsequent to the irradiation for 40 s. Differential scanning calorimetry (DSC)was also employed as a complementary technique. For the light-cured specimen, two abrupt drops in the log storage modulus (E ) and two peaks in the tan δ vs. temperature curve corresponding to the glass transition were observed. The storage modulus was slightly increased with increasing temperature between the two modulus drops. The DSC experiment showed that the light-cured specimen contains residual living groups trapped by the fast reaction, which lead to further reaction during post-cure heat treatment. This further thermal reaction is considered to be responsible for the modulus increase. After heating to 175• C above the DSC exothermic peak, most of the residual groups in the light-cured specimen were found to be reacted, showing a single decrease in modulus and a single peak in the tan δ curve, and no exotherm in the DSC curve. With the aid of DSC data, the further thermal cure reaction with increasing temperature may occur within the glass transition region. The occurrence of the thermal reaction gives rise to the inaccuracy in determining the glass transition temperature (T g ). KEY WORDS Dynamic Mechanical Analysis (DMA) / DSC / UDMA / Storage Modulus / Tan δ / Glass Transition / It is well known that the dynamic mechanical analysis (DMA) is a very powerful technique for studying not only solid and viscoelastic liquids but also reactive materials undergoing changes in low molecular weight monomer to high molecular weight network. 1 The DMA technique is to impart the controlled mechanical oscillation to a solid or viscoelastic liquid, and to measure in-phase and out-of-phase response of the specimen. One calculates the storage modulus (E ) from the in-phase and the loss modulus (E ) from the out-of-phase response, which represent the energy stored and dissipated, respectively. Tan δ, where δ is the phase angle between the stress and strain in the oscillatory experiment, is given by the ratio of energy dissipated to energy stored per cycle (E /E ).From the analysis of the dynamic mechanical parameters, useful information on material properties can be obtained such as bulk properties directly related to material performance and primary and secondary transitions not easily identified by other methods. Typically, the information concerning polymeric systems from DMA includes quantitative modulus, glass transitions, rate and extent of polymerization, quantification of gelation, degree of cross-linking, and changes in polymer chain mobility. Among the dynamic mechanical properties in dental polymeric materials, the E as a parameter of materials stiffness and the gla...

Effect of the structure of silane‐coupling agent on dynamic mechanical properties of dental resin‐nanocomposites

“…In the corresponding tan δ versus temperature curve two separate and distinct peaks were observed assigned to two T g s. The trend of two apparent T g values have also been observed in room‐temperature‐cured vinyl ester resins19, 20 and has attributed to additional cure of the sample when the temperature is being scanned in the DMA. Two T g s were also observed in the tan δ curve of UDMA/TEGDMA resin,21 a Bis‐GMA resin,22 a UDMA resin,23 and in two commercial light‐cured resin composites24, 25; in all these cases the two T g s were attributed to the additional thermal cure occurring in the middle of the first glass transition.…”

Evaluation of the light polymerization efficiency of copolymers used in dental formulations by differential scanning calorimetry

“…Indeed, heating increases the segmental mobility of the network and promotes the reaction between the present radicals and the surrounding unreacted functional groups 16. Other studies have shown that, according to differential scanning calorimetry (DSC) analysis, a dimethacrylate sample under a nitrogen atmosphere immediately after photopolymerization exhibits an exothermic reaction effect, whereas heating these samples after 1 night under an air‐free atmosphere has no detectable exothermic effect 17, 18…”

Σύνθεση Και Μελέτη Ιδιοτήτων Οδοντιατρικών Νανοσύνθετων Υλικών Πολυμεθακρυλικής Μήτρας

“…Η περιοχή μείωσης του logE΄ στο θερμοκρασιακό εύρος 85 -175 o C Στην καμπύλη της μεταβολής του μέτρου απωλειών, Ε΄΄, με τη θερμοκρασία για όλα τα υλικά, εμφανίζονται δύο ευρείες κορυφές. Η πρώτη κορυφή είναι το αποτέλεσμα της διαδικασίας χαλάρωσης του φωτοσκληρυμένου σύνθετου υλικού, ενώ η δεύτερη κορυφή συνιστά τη διαδικασία χαλάρωσης του υλικού που προέκυψε από την επιπρόσθετη θερμική σκλήρυνση του φωτοσκληρυμένου υλικού.Στην καμπύλη της μεταβολής της tanδ ως προς τη θερμοκρασία, σε όλα τα υλικά, δυο ξεχωριστές και σαφής κορυφές παρατηρηθήκαν (Σχήμα 7.14.γ) 69,132,[170][171][172][173][174]. Κάθε κορυφή αντιστοιχεί σε καθεμιά από τις απότομες πτώσεις της καμπύλης του Ε΄ με τη θερμοκρασία, που αντιπροσωπεύουν τις δύο περιοχές της υαλώδους μετάβασης.…”