Effects of inhibitors and retarders on low temperature free radical crosslinking polymerization between styrene and vinyl ester resin

Abstract

Many composite manufacturing methods are room temperature processes, which require the resins to be cured at low temperatures. Examples are Seemann Composite Resin Infusion Molding Process (SCRIMP)—a vacuum assisted resin transfer molding (VARTM) process, hand lay‐up and spray‐up. Vinyl ester resins have been widely used in this type of processes because of their versatility as a composite matrix. Low temperature polymerization between styrene and vinyl ester tends to be complex because of the presence of different curing agents. This paper reports on (1) the effects of a promoter (cobalt naphthenate) on the initiatin at low temperatures, and (2) the effects fo a retarder (2,4‐pentanedione) and an inhibitor (1,4‐benzoquinone) on the pot life, gel time, and cure kinetics. A differntial scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer were used to investigate the reaction kinetics of vinyl ester resins. The influence of the retarders and inhibitors on the rheological changes of the resin during curing was also studied using a Rheometris Dynamic Analyzer (RDA).

Mechanical characterization and chemical resistances of cured unsaturated polyester resins modified with vinyl ester resins based on recycled poly(ethylene terephthalate)

“…22 When the temperature rise is sufficiently high, the thermal decomposition of uncatalyzed initiators or even the self-initiation of the monomers may take place, which accelerates the curing reaction of UP resins. 23 Although the temperature rise can enhance the curing reaction and increase the final conversion, a fully cured polymeric composite part is still difficult to achieve when processed at room temperature stability of molded composites. Therefore, a major concern for fabricators is how to control the curing process, achieving a high final resin conversion with low residual volatile chemical content in low-temperature composite manufacturing processes.…”

Influence of tribological test on the global conversion of natural composites

“…This potential affection is based on that the curing process is a heterogeneous, highly exothermic free radical copolymerization [15,22] where three reactions occur at the same time: vinyl ester homo-polymerization, styrene (or any other unsaturated vinyl monomer as mentioned before) homo-polymerization and vinyl ester-styrene copolymerization [3,8,13,17] . The crosslinking reaction undergoes in differential form because the vinyl ester double bonds at the beginning of the reaction, reacts faster than the ones of the styrene, but in the final part is the opposite.…”

“…Also are used diacylperoxides, peresteres, diaryl peroxides, dialkyl peroxides, hydroperoxydes such as cumene hydroperoxyde [3] cumyl hydroperoxyde [5] , for high temperature curing the most common initiator is benzoyl peroxyde (BPO) [1,12,15,19] , but t-butyl proxy-benzoate [22] is used as well sometimes. An activator does the decomposition in free radicals of the initiators.…”

“…Polymers such as unsaturated polyester resins, epoxy resins and vinyl ester resins have been used as matrix for composite materials in an uncountable amount of technical applications [1][2][3][4][5][6][7][8][9][10][11] . The most popular of them due to the low cost, reasonable good properties and simplicity for processing are the unsaturated polyester resins, but when better mechanical or chemical resistance properties are required, the epoxy resins are preferred.…”

“…At high temperature curing these hardeners may be used alone or at room temperature curing is required the use of a redox initiation system [3] of promoter (initiator, hardener) and activator (accelerator), these are systems of the peroxide, cobalt salts and/or ternary amines [28] , not always with the three components. The vinyl ester resins may also be cured via photo-polymerization [8] using an appropriate photoinitiator [21] .…”