Latent Thermal Catalyst Research Articles

열잠재성 촉매에 의한 에폭시/폴리우레탄 블랜드계의 경화거동, 유변학적 및 기계적 물성에 관한 연구

본 연구에서는 잠재성 양이온 개시제 (N-benzyl pyrazinium hexafluoroantiminate, BPH)를 이용한 에폭시/폴리우레탄 블랜드계의 혼합조성에 따른 경화거동과 유변학적 특성 그리고 기계적 물성 변화에 대하여 연구하였다. 블랜드계의 반응성은 DSC를 이용하여 반응 온도에 따른 전환률을 구하여 측정하였으며, 유변학적 특성은 레오미터를 이용한 등온 실험을 통하여 측정하였고, 가교 활성화에너지(Ec)는 겔화 시간과 경화 온도를 이용하여 Arrhenius 방정식으로 구하였다. 한편, 경화된 시편의 기계적 물성은 충격강도 실험을 통하여 측정하였다. 실험결과, 블랜드계의 열잠재성 촉매로 사용된 BPH는 어떤 공개시제 없이도 우수한 촉매 특성을 나타내었다. 본 블랜드계의 가교 활성화에너지 및 충격강도는 PU가 30 wt% 첨가되었을 때 최대를 나타내었는데, 이는 EP와 PU간의 수소결합으로 인한 치밀한 가교밀도의 증가 때문이라고 사료된다. In this work, the cure kinetics and rheological and mechanical properties of diglycidylether of bispheonol A (DGEBA, EP)/polyurethane (PU) blends were investigated. The 1 wt% N-benzylpyrazinium hexafluoroantiminate (BPH) was used as a latent thermal catalyst. Latent properties were performed by measurement of the conversion as a function of reaction temperature using DSC. And the rheological properties of the blend systems were investigated under isothermal conditions using a rheometer. Crosslinking activating energies (Ec) were also determined from the Arrhenius equation based on gel time and curing temperature. The impact strengths were measured as mechanical properties of the casting specimens. The BPH in the blend systems could be an excellent latent thermal catalyst without any co-initiator. The rheological results showed that Ec was highest when PU content was 30 wt% which was in good agreement with the impact strengths. This was probably due to the intermolecular hydrogen bonding between the hydroxyl group in PU and EP, resulting in increasing the crosslinking density.

Thermal and mechanical properties of diglycidylether of bisphenol A/ trimethylolpropane triglycidylether epoxy blends cured with benzylpyrazinium salts

AbstractThe effect of blend composition on thermal stability and mechanical properties of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends cured with benzylpyrazinium salts (N‐benzylpyrazinium hexafluoroantimonate, BPH) as a thermal latent catalyst was investigated. The thermal stability, characterized by the initial decomposition temperature, temperature of maximum rate of weight loss, integral procedural decomposition temperature, and activation energy for decomposition, increase in DGEBA‐rich compositions. This could be due to the long repeat unit and stable aromatic ring in the DGEBA. The mechanical properties are also discussed in terms of the fracture toughness (KIC), flexural and impact tests for the blend composition studied. The addition of TMP into DGEBA gives systematic improvements in fracture toughness, which results from the increase in aliphatic and flexible chain segments of TMP.© 2002 Society of Chemical Industry

Cure behavior of epoxy resins with different kinds of onium salts as latent thermal catalysts

Cure behavior of epoxy resins with different kinds of onium salts as latent thermal catalysts

Cure behavior of epoxy resins with different kinds of onium salts as latent thermal catalysts

AbstractTwo latent thermal catalysts, Dimethyl phenacylsulfonium hexafluoroantimonate, (Benzyl‐S), and triphenyl benzyl phosphonuim hexafluoroantimonate, (Benzyl‐P), were synthesized. Both these synthesized catalysts fulfill requirements for a rapid cure at a moderately elevated temperature in curing the epoxy resins of neat 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexane‐carboxylate, (EPC), neat 2,2‐bis(4‐glycidyloxyphenyl)propane, (EPA), and their hybrid resin. The cure behavior of these resins cured individually with the synthesized catalysts was studied through correlation of the in situ FTIR (Fourier transform infrared) spectroscopy and DSC (differential scanning calorimetry) dynamic scanning results. Catalyst Benzyl‐S is more effective than Benzyl‐P. Resin EPC is significantly more sensitive to the latent thermal catalysts than the EPA resin. Activated chain‐end (ACE) and activated monomer (AM) mechanisms are basically adopted. Isomerization occurs in the neat EPA cure system, and transesterification takes place in all systems containing EPC species in the latter curing stage. Most importantly, ester linkages CO in the hybrid systems have been destroyed at some time during the curing process, but some reformed at the latter curing stage. It is most likely that the CO linkage in the EPC segments was attacked by the activated chain‐end of the epoxide group of EPA species to form a five‐membered cyclic acetal. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3539–3551, 2001

Viscoelastic behavior of anhydride‐cured epoxy system initiated by thermal latent catalyst

AbstractThe thermal latency and viscoelastic behavior during the cure of a new catalytic (N‐benzylpyrazinium hexafluoroantimonate) anhydride‐cured epoxy system were studied with differential scanning calorimetry and a rheometer under isothermal conditions. The gelation time was obtained from the evaluation of the storage modulus, loss modulus, and damping factor. The temperature dependence on the reaction time was described by the Arrhenius expression, and the crosslinking activation energy was determined from the Arrhenius plot based on the gelation time and reaction temperature. The gelation time and crosslinking activation energy characterized from rheological behaviors increased with increasing anhydride composition and showed a maximum value with a mixing ratio of 0.65, which was due to the compact crosslinking network without a side reaction in the ratio. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 646–653, 2001

Near-infrared spectroscopic studies on the cure behaviors of the CAE/DGEBA blend system initiated by a thermal latent catalyst

The latent properties and cure behaviors of an epoxy blend system based on cycloaliphatic epoxy (CAE) and diglycidyl ether of bisphenol A (DGEBA) epoxy containing N-benzylpyrazinium hexafluoroantimonate (BPH) as a thermal latent initiator were investigated with near-infrared (N-IR) spectroscopy. The assignments of the latent properties and cure kinetics were performed by the measurements of the N-IR reflectance for epoxide and hydroxyl functional groups at different temperatures and compositions. As a result, this system showed more than one type of reaction, and BPH was an excellent thermal latent catalyst without any coinitiator. The cure behaviors were identified by the changes in the absorption intensity of the hydroxyl groups at 7100 cm−1 with different composition ratios. Moreover, characteristic N-IR band assignments were used to evaluate the reactive kinetics and were shown to be an appropriate method for studying the cure behaviors of the CAE/DGEBA blend system containing a thermal latent catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 326–331, 2001

Relationship between viscoelastic properties and gelation in the epoxy/phenol-novolac blend system with N-benzylpyrazinium salt as a latent thermal catalyst

A study of viscoelastic properties and gelation in epoxy/phenol-novolac blend system initiated with 1 wt % of N-benzylpyrazinium hexafluoroantimonate (BPH) as a latent cationic thermal initiator was performed by analysis of rheological properties using a rheometer. Latent behavior was investigated by measuring the conversion as a function of curing temperature using traditional curing agents, such as ethylene diamine (EDA) and nadic methyl anhydride (NMA) in comparison to BPH. In the relationship between viscoelastic properties and gelation of epoxy/phenol-novolac blend system, the time of modulus crossover was dependent on high frequency and cure temperature. The activation energy (Ec) for crosslinking from rheometric analysis increased within the composition range of 20–40 wt % phenol-novolac resin. The 40 wt % phenol-novolac (N40) to epoxy resin showed the highest value in the blend system, due to the three-dimensional crosslinking that can take place between hydroxyl groups within the phenol resin or epoxides within the epoxy resin involving polyaddition of the initiator with BPH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2299–2308, 2001

Studies on epoxy resins cured by cationic latent thermal catalysts: The effect of the catalysts on the thermal, rheological, and mechanical properties

Studies on epoxy resins cured by cationic latent thermal catalysts: The effect of the catalysts on the thermal, rheological, and mechanical properties

Isothermal cure kinetics of epoxy/phenol‐novolac resin blend system initiated by cationic latent thermal catalyst

Isothermal cure kinetics of epoxy/phenol‐novolac resin blend system initiated by cationic latent thermal catalyst

Studies on epoxy resins cured by cationic latent thermal catalysts: The effect of the catalysts on the thermal, rheological, and mechanical properties

To investigate the effect of catalysts on the thermal, rheological, and mechanical properties of an epoxy system, a resin based on diglycidyl ether of bisphenol-A (DGEBA) was cured by two cationic latent thermal catalysts, N-benzylpyrazinium hexafluoroantimonate (BPH) and N-benzylquinoxalinium hexafluoroantimonate (BQH). Differential scanning calorimetry was used for the thermal characterization of the epoxy systems. Near-infrared spectroscopy was employed to examine the cure reaction between the DGEBA and the latent thermal catalysts used. The rheological properties of the blend systems were investigated under an isothermal condition with a rheometer. To characterize the mechanical properties of the systems, flexure, fracture toughness (KIC), and impact tests were performed. The phase morphology was studied with scanning electron microscopy of the fractured surfaces of mechanical test samples. The conversion and cure activation energy of the DGEBA/BQH system were higher than those of the DGEBA/BPH system. The crosslinking activation energy showed a result similar to that obtained from the cure kinetics of the blend systems. The flexure strength, KIC, and impact properties of the DGEBA/BQH system were also superior to those of the DGEBA/BPH system. This was a result of the substituted benzene group of the BQH catalyst, which increased the crosslink density and structural stability of the epoxy system studied. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 187–195, 2001

Isothermal cure kinetics of epoxy/phenol-novolac resin blend system initiated by cationic latent thermal catalyst

The investigation of the cure kinetics of a diglycidyl ether of bisphenol A (DGEBA)/phenol-novolac blend system with different phenolic contents initiated by a cationic latent thermal catalyst [N-benzylpyrazinium hexafluoroantimonate (BPH)] was performed by means of the analysis of isothermal experiments using a differential scanning calorimetry (DSC). Latent properties were investigated by measuring the conversion as a function of curing temperature using a dynamic DSC method. The results indicated that the BPH in this system for cure is a significant thermal latent initiator and has good latent thermal properties. The cure reaction of the blend system using BPH as a curing agent was strongly dependent on the cure temperature and proceeded through an autocatalytic kinetic mechanism that was accelerated by the hydroxyl group produced through the reaction between DGEBA and BPH. At a specific conversion region, once vitrification took place, the cure reaction of the epoxy/phenol-novolac/BPH blend system was controlled by a diffusion-control cure reaction rather than by an autocatalytic reaction. The kinetic constants k1 and k2 and the cure activation energies E1 and E2 obtained by the Arrhenius temperature dependence equation of the epoxy/phenol-novolac/BPH blend system were mainly discussed as increasing the content of the phenol-novolac resin to the epoxy neat resin. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2945–2956, 2000

Cure behavior of diglycidylether of bisphenol A/trimethylolpropane triglycidylether epoxy blends initiated by thermal latent catalyst

Cure behaviors of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends initiated by 1 wt % N-benzylpyrazinium hexafluoroantimonate (BPH) as a cationic latent catalyst were investigated using DSC and rheometer. This system showed more than one type of reaction and BPH could be excellent thermal latent catalyst without any co-initiator. The cure activation energy (Ea) obtained from Kissinger method using dynamic DSC data was higher in DGEBA/TMP mixtures than in pure DGEBA. Rheological properties of the blend system were investigated under isothermal condition using a rheometer. The gel time was obtained from the analysis of storage modulus (G′), loss modulus (G″) and damping factor (tanδ). The crosslinking activation energy (Ec) was also determined from the Arrhenius equation based on the gel time and curing temperature. As a result, the crosslinking activation energy showed a similar behavior with that obtained from Kissinger method. And the gel time decreased with increasing TMP content, which could be resulted from increasing the activated sites by trifunctional epoxide groups and decreasing the viscosity of DGEBA/TMP epoxy blend in the presence of TMP. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2114–2123, 2000

Development and application of latent hydrosilylation catalyst [6]: control of activity of platinum catalyst by isocyanide derivatives on the crosslinking of silicone resin via hydrosilylation

Quite effective nature of isocyanides to control the curing reaction of silicone resin via the Pt-catalyzed hydrosilylation process is described. In the presence of the isocuanides, the curing reaction of the silicone resin by H 2PtCl 6 did not occur at ambient temperature, while the lack of the isocyanide systems conducts the smooth curing, indicating that the present systems serve as a thermal latent catalyst for silicone resin. The curing temperature was controllable by the character and the concentration of the isocyanides employed.

Monomer-Isomerization Polymerization of 3-Methyl-3-(phthalimidomethyl)oxetane with Two Different Ring-Opening Courses

The cationic polymerization of 3-methyl-3-(phthalimidomethyl)oxetane (1) afforded two kinds of polymers. One was a polyacetal, i.e., poly{oxy(8,9-benzo-4-methyl-7-oxo-2,6-oxazabicycio[4,3]nona-8-ene-1,4-diyl)methylene (3), produced at 50 °C and below, and the other was a polyether, i.e., poly[oxy-(2-methyl-2-phthalimidomethyltrimethylene)] (4), produced at 80 °C and above. This new polymerization with the two ring-opening courses was accompanied by the monomer-isomerization process of 1 to give 5,6-benzo-1-methyl-8,11,3-dioxazatricyclo[5.2.2.0 3,7 ]undeca-5-en-4-on (2). The cyclic acetal 2, therefore, functioned as the real monomer, and either single or double ring-opening polymerization took place to give 3 or 4, respectively, depending on the reaction temperature. The strain of 2 for ring-opening is discussed on the basis of the result of X-ray structure analysis. The single ring-opening process of 2 was an equilibrium polymerization having the standard enthalpy and entropy changes in dichloromethane equal to -15.8 kJ mol -1 and -46.0 J mol -1 K -1 , respectively, and the ceiling temperature (T c ) equal to 70.1 °C for 1 mol L -1 solution. The critical temperature, where the structure of the product polymer changed, was related to a T c calculated for the conditions employed (59. 1 °C for polymerization in 0.83 mol L -1 dichloromethane solution). Therefore, 3 was successfully transformed to 4 with a thermal latent catalyst at a higher temperature than the T c through the ring-closure depolymerization of 3 to 2 followed by the repolymerization of 2 in the double ring-opening manner. When 1 was polymerized in a temperature step-down mode, a block copolymer with the 3-4 sequence was prepared from the single monomer. Moreover, 1 was copolymerized with a nonisomerizable oxetane, accompanying the monomer isomerization of 1.

An allylic pyridinium salt: Radical promoted latent thermal catalyst for cationic polymerization

An allylic pyridinium salt: Radical promoted latent thermal catalyst for cationic polymerization

Thermal cationic curing with benzylammonium salts — 2

Various cationic initiators of the benzylammonium SbF 6 type were synthesized from substituted benzyl chlorides and pyridine or N,N-dimethylaniline followed by exchange of the counter anion with SbF 6. These benzylammonium SbF 6 salts acted as latent thermal initiators in the cationic polymerization of glycidyl phenyl ether. A cationic curing system, consisting of an initiator, a polymer containing oxirane moiety and 3,4-epoxy cyclohexylmethyl 3,4-epoxy cyclohexyl carboxylate, was examined as a film forming mechanism. Furthermore, properties of the coating solutions and those films were evaluated. It was found that α,α-dimethylbenzyl pyridinium SbF 6 was a superior latent thermal catalyst for cationic curing and that 3,4-epoxy cyclohexylmethyl 3,4-epoxy cyclohexyl carboxylate was effective in high-solids coatings.

A New Grafting Method by Use of Polymeric Sulfonium Salt. Grafting of Bicyclo Ortho Ester onto Polystyrene

Abstract Polymer containing sulfonium salt structure, which was obtained by the polymerization of p-vinylbenzyl tetramethylenesulfonium hexafluoroantimonate, was found to behave as a polymeric thermal latent catalyst for the polymerization of bicyclo ortho ester and lead to the grafted polymer.

Polymerization of spiroorthocarbonates by sulfonium salts, as latent thermal catalysts

Polymerisation en masse a 120°C et en solution en copolymere alterne qui contient des groupes ether et carbonate