Low temperature cure of vinyl ester resins

Abstract

Vinyl ester resins are well known for their versatility as a composite matrix. With the development of a promising room temperature molding technology, vacuum‐assisted resin transfer molding, e.g. Seemann Composite Resin Infusion Molding Process (SCRIMP), the processability of vinyl ester resins at low temperatures has attracted considerable attention from the composite industry. The objective of this paper is to provide a better understanding of the reaction kinetics of this resin system at low temperatures. In this study, a differential scanning calorimeter (DSC) coupled with a Fourier transform infrared (FTIR) spectrometer was employed to measure the reaction profile of a vinyl ester resin with different promoter and styrene contents. A kinetic model based on the free radical co‐polymerization mechanism was developed for simulating the reaction rates and conversions of styrene vinyl and vinyl ester vinylene groups. The model parameters were determined from several FTIR experiments under isothermal conditions. This model, in conjunction with heat transfer analysis, was able to successfully predict the temperature profiles during curing in two SCRIMP molding cases based on groove type resin distribution system.

Processing and properties of SiC/vinyl ester nanocomposites

“…The scanning calorimetry traces appear to be composed of at least two exothermic peaks and so are suggestive of two reaction processes. The first peak is due the copolymerization of the styrene with the vinyl ester vinylene groups, while the second peak (or shoulder) is caused by styrene homopolymerization or grafting reaction of styrene along vinyl ester chains [13].…”

Thermal curing behavior of MWCNT modified vinyl ester‐polyester resin suspensions prepared with 3‐roll milling technique

“…These findings are very consistent with those in other similar studies reported in the literature. 19,20 However, as depicted in Figures 8 and 9, it was observed that the individual fractional conversion rates of styrene and VE were altered dependent on the amine functional groups over the surfaces of CNTs. The final conversion of styrene exceeded the final conversion of VE double bonds in the resin suspensions with MWCNT-NH 2 .…”

“…Please note that only neat VE resin was used as matrix material to ease the interpretation of data because, in the case of a complex mixture of polymers, it would be hard to differentiate which bands come from which molecules. [16][17][18][19] As VE resin contains styrene, CNTs were blended with VE resin via mechanical stirring to avoid evaporation of styrene. The FTIR spectra of MWCNTs and MWCNT-NH 2 were also taken to correlate the data obtained for their corresponding nanocomposites.…”

“…The main emphasis with DSC is on gathering data to develop empirical models like the autocatalytic kinetic model, which are system specific and thus not representative for all styrene/VE or UP systems. [15][16][17][18][19][20][21] At this stage, researches focused further their attention on Fourier infrared spectroscopy (FTIR) spectrometry, which offers the potential to differentiate the rate of isothermal reactions dependent on the spectral changes of different functional groups. [8][9][10] FTIR allows depletion of the reactive species in a sample to be monitored in a separate manner, provided that their absorption peaks are noticeable from the product peaks of interest.…”

“…Note that the peaks at 945 cm À1 and 910 cm À1 correspond to out of plane bending of carbon-hydrogen bonds in the vinyl group of the VE monomer and wagging of CH 2 in the vinyl group of the styrene monomer, respectively. 19,20 Aromatic carbon-hydrogen bonds at 830 cm À1 in VE and 700 cm À1 in styrene were used to correct for the thickness changes in the sample during reaction. Eqs 6 and 7 were then employed to compute normalized fractional conversion of VE and styrene double bonds, respectively.…”