Long Chopped Glass Fiber Reinforced Low-Density Unsaturated Polyester Resin under Different Initiation

Abstract

Long chopped glass fiber reinforced low-density unsaturated polyester resin (LCGFR-LDUPR) composite materials with light weight and excellent mechanical properties were prepared. It was proved that long chopped glass fiber, which was in length of 15.0 mm and chopped from ER4800-T718 plied yarn, was suitable for the preparation of LCGFR-LDUPR composite samples. With the coexistence of 1.50 parts per hundred of resin (phr) of methyl ethyl ketone peroxide (MEKP-II) and 0.05 phr of cobalt naphthenate, optimal preparation parameters were obtained, which were 20.00 phr of long chopped glass fiber, 2.50 phr of NH4HCO3, at a curing temperature of 58.0 °C. The lowest dosage of activated radicals produced by MEKP-II and cobalt naphthenate enabled the lower curing exothermic enthalpy and the slowest crosslinking for unsaturated polyester resin to carry out, resulting in a higher curing degree of resin. It was conducive to the formation, diffusion, and distribution of bubbles in uniform size, and also for the constitution of ideal three-dimensional framework of long glass fibers in the cured sample, which resulted in the LCGFR-LDUPR composite sample presenting the apparent density (ρ) of 0.68 ± 0.02 g/cm3, the compression strength (P) of 35.36 ± 0.38 MPa, and the highest specific compressive strength (Ps) of 52.00 ± 0.74 MPa/g·cm3. The work carried out an ideal three-dimensional framework of long chopped glass fiber in the reinforcement to low-density unsaturated polyester resin composite samples. It also presented the proper initiator/accelerator system of the lower curing exothermic enthalpy and the slowest crosslinking for unsaturated polyester resin.

Low-Density Unsaturated Polyester Resin with the Presence of Dual-Initiator

“…Furthermore, four factors, such as the curing temperature (factor A), the content of initiator x (factor B), the content of initiator y (factor C), and the content of the foaming agent NH 4 HCO 3 (factor D), were selected as four factors in the orthogonal experiment. Usually, the content of the foaming agent NH 4 HCO 3 was 1.00 phr to 3.00 phr [ 10 , 11 ]. As for the dual-initiator system of CYHP/MEKP, it could be determined that the curing temperature (factor A) range was 60.0 °C to 68.0 °C in intervals of 2.0 °C, the content of CYHP (factor B) or MEKP (factor C) was both 1.00 phr to 2.00 phr in intervals of 0.25 phr, and the addition of NH 4 HCO 3 (factor D) was 1.00 phr to 3.00 phr in intervals of 0.50 phr.…”

“…Values of A, B, and T were respectively obtained from the results of gel time experiments. The addition of the foaming agent NH 4 HCO 3 was no more than 3.00 phr (per hundred of resin, phr) [ 10 , 11 ]. In the process of sample manufacture, the mold was coated with the release agent PMR-EZ and then heated at a rising rate of 5 °C/min from ambient temperature to a certain temperature, which is listed in the followed orthogonal experiment of preparation of LDUPR samples.…”

“…According to GB/T 24148.2-2009(ISO 3672-2:2000) [30], LDUPR samples were prepared by a formulation of (part of weight): 100 parts resin: A part initiator x: B part initiator y: C part NH 4 HCO 3 at a treating temperature of T • C. Values of A, B, and T were respectively obtained from the results of gel time experiments. The addition of the foaming agent NH 4 HCO 3 was no more than 3.00 phr (per hundred of resin, phr) [10,11]. In the process of sample manufacture, the mold was coated with the release agent PMR-EZ and then heated at a rising rate of 5 • C/min from ambient temperature to a certain temperature, which is listed in the followed orthogonal experiment of preparation of LDUPR samples.…”

“…The cross-linking mechanism of UPR with radicals was considered to be initiated by thermal initiation or redox initiation [ 7 , 8 , 9 ]. Fu et al found that a methyl ethyl ketone peroxide (MEKP)/cobalt naphthenate system showed characteristics of lower curing exothermic and slow crosslinking for LDUPR [ 10 ]. Zhang et al improved the specific compressive strength ( P s ) of LDUPR, utilizing the synergistic action of methyl ethyl ketone peroxide (MEKP-II) and cobalt naphthenate [ 11 ].…”

Fast-Setting Permeable Alkyd/Polyester Composites: Moulding Sands

“…Alkyd resins and (unsaturated) polyester resins are typically crosslinked by polyisocyanates (PI). In order to achieve an adequate rate of crosslinking, various catalysts are used: organic compounds of cobalt, zinc, lead and other metals [18][19][20][21] or peroxides [36][37][38][39]. The moulding composite materials with these types of polymeric matrix usually contain up to 1.5% of the binder, of which PIs constitute ~20 to 30%.…”