Authors:Jiang Jinxue, Yang Yonglin, Li Cheng, and Li Jianzhang
properties. It is well known that the curingbehavior of resin determines the properties of wood-based panels. Therefore, knowledge about the effect of FR chemicals on adhesive resins is important for efficient use of adhesive and FR to achieve good bonding
Authors:Qing Guo, Yan Huang, Yu-Ying Zhang, Li-Rong Zhu, and Bao-Long Zhang
. Therefore, we designed and synthesized a homologous series of novel curing agents (LCECA n ) with different number of methylene units ( n = 2, 4, 6). The curingbehaviors of diglycidyl ether of bisphenol-A epoxy (E-51)/LCECA n and 4,4′-bis(2,3-epoxypropoxy
Authors:Qun Zhou, Donghwan Cho, Bong Song, and Hyun-Joong Kim
In this study, polycardanol, which was synthesized by enzymatic oxidative polymerization of thermally treated cashew nut shell
liquid (CNSL) using fungal peroxidase, was partially or fully cured using methyl ethyl ketone peroxide (MEKP) as initiator
and cobalt naphthenate (Co-Naph) as accelerator. The curing behavior of polycardanol was extensively investigated in terms
of curing temperature, curing time, concentration of initiator and accelerator, and the monomer-to-polymer conversion of polycardanol
by means of differential scanning calorimetry (DSC). The curing behavior significantly depends on the thermal condition given
and it was monitored with the change of the exotherms as a function of temperature. The optimal conditions for fully curing
polycardanol are 1 wt% MEKP, 0.2 wt% Co-Naph, curing time 120 min, and curing temperature 200 °C. This study suggests that
a polycardanol with high monomer-to-polymer conversion would be useful for processing a polycardanol matrix composite under
the optimal conditions of curing.
properties, such as greater thermal stability, toughness, and lower thermal-expansion coefficient because of the formation of many LC domains in the cured networks. Over the past few decades, various LCTS have been synthesized, and their curingbehaviors
Authors:K. Siimer, T. Kaljuvee, P. Christjanson, and T. Pehk
Summary The curing behaviour of commercial UF and MUF resins, stored at room temperature nearly up to gelation, is studied by simultaneous TG-DTA technique and structural changes of resins are also followed during aging. On the basis of 13C NMR spectra, the main chemical reaction during UF resin storage is the formation of methylenes and dimethylene ethers linked to secondary amino groups. Aging of resins results in a decrease of cure rate which is related to lower concentration of active functional groups and decrease in molecular mobility. On DTA curve, the resin with higher content of methylol groups reveals the curing exotherm earlier. With decreasing methylol content during storage, the peak maximum of exotherm is shifted to higher temperature value. Advanced polycondensation and sedimentation processes during storage produce partly locked in macromolecule structure water, and the water evaporation endotherm on DTA curve shifts to considerably higher temperature. The aged MUF resins are chemically less changed than UF resins and the aging process mainly involves noncovalent network formation due to complex molecular structure.
The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict
the gel time tg and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures
and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained
by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation
time tgand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite
decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent
activation energy of the cure reaction after gelation point. There is no special curing process required for the formation
of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.
Bismaleimide resin (Compimide 353) was modified with the liquid elastomer carboxyl-terminated acrylonitrile butadiene (CTBN).
The prereaction synthesis and curing of the CTBN-bismaleimide resin is discussed. The structure of the modified resin was
identified by IR and NMR spectroscopy. The basic curing mechanism is also discussed. DSC and TG were used to study the curing
behaviour and kinetic parameters, viz. the order of reaction, energy of activation and preexponential factor. Adhesive properties
such as lap shear strength and peel strength at room temperature and elevated temperature were evaluated and are discussed.
Authors:K. Siimer, T. Kaljuvee, P. Christjanson, T. Pehk, and I. Saks
Thermal behaviour of cure-accelerated phenol-formaldehyde (PF) resins was studied using the addition of commercial mixture
of water soluble oil shale alkylresorcinols (AR) to PF resin, 5-MR being as model compound. The acceleration effect of AR
is based on the promotion of condensation of resin methylol groups and subsequent reaction of released formaldehyde with AR.
Commercial PF resins SFŽ-3013VL and SFŽ-3014 from the Estonian factory VKG Resins have been used. The chemical structure of
resins was characterised by 13C NMR spectroscopy. TG-DTA analysis was carried out using labsysTM instrument Setaram. By TG-DTA measurements, the shift of exothermic and endothermic peaks and the changes of mass loss rate
in the ranges of 1.5–10 g AR/100 g PF resin were studied. The effect of AR on the curing behaviour of PF resins was also followed
by gel time.
Testing of the plywood when using PF resin with 5 mass% of AR shows that the press time could be reduced by about 15%.
The curing behaviour of bismethacryloxy derivative of diglycidyl ether of bisphenol A (vinyl ester resin) containing styrene as the reactive diluent (40% w/w) was studied using gel point determination method and DSC. Seven samples of styrene/α-methylstyrene in the ratio 40∶0, 35∶5, 30∶10, 25∶15, 20∶20, 15∶25 and 0∶40 were studied. Delayed curing was observed in samples containing increasing proportions of α-methylstyrene. The energy of activation decreased from 869 kJ mol−1 to 333 kJ mol−1 as the concentration of α-methylstyrene increased in the formulations. However, no difference in thermal stability was observed by replacement of styrene by α-methylstyrene. It was concluded that in vinyl ester resin samples 10–15% α-methylstyrene and 30-25% styrene can be used as reactive diluent.
are important for the above-mentioned practical applications [ 8 ]. The curingbehavior and thermal properties of LCERs are dependent on the structure of the aromatic mesogenic group and the length of the flexible spacer, which decouples the reactive