Epoxidized phenolic novolac: A novel modifier for unsaturated polyester resin

Abstract

Unsaturated polyester resins (UPRs) are used widely in the fiber-reinforced plastics (FRPs) industry. These resins have the disadvantages of brittleness and poor resistance to crack propagation. In this study, hybrid polymer networks (HPNs) based on UPR and epoxidized phenolic novolacs (EPNs) were prepared by reactive blending. A HPN is composed of a backbone polymer containing two types of reactive groups that can take part in crosslinking reactions via different mechanisms. EPNs were prepared by glycidylation of novolacs using epichlorohydrin. The novolacs had varying phenol: formaldehyde ratios. Blends of unsaturated polyester with EPN were then prepared. The physical properties of the cured blends were compared with those of the control resin. EPN shows good miscibility and compatibility with the resin and improves the toughness and impact resistance substantially. Considerable enhancement of tensile strength is also noticed at about 5% by weight of epoxidized novolac resin. TGA, DMA, and DSC were used to study the thermal properties of the toughened resin and the fracture behavior was studied using SEM. The blends are also found to have better thermal stability. Blending with EPN can be a useful and cost-effective technique for modification of UPR.

Preparation of Furfuryl Alcohol‐Functionalized Carbon Nanotube and Epoxidized Novolac Resin Composites with High Char Yield

“…ENR was obtained by the reaction between ECH and NR . For this purpose, 21.4 g NR and 32.0 g ECH were added into a flask and agitated at 80°C for 2 h. After addition of 32 g NaOH (40% in water) during 6 h at 100°C and stirring for an additional 1 h, temperature was decreased to 25°C.…”

Post-functionalization of novolac resins by introducing thermo-crosslinkable –OCFCF2 groups as the side chains: a new strategy for production of thermosetting polymers without releasing volatiles

“…11,12 However, releasing volatiles is a major obstacle which limits the application of the resins. 5,12,14 It is noted that directly thermo-crosslinkable novolac resins have been also developed, and the resins containing cyanate ester groups (-OCN) have garnered significant interest from both academia and industry. 5 For this purpose, curing agents such as hexamethylenetetramine (HMTA) are often used, as curing with HMTA yields volatile by-products including formaldehyde, ammonia and water.…”

Toughening modification of unsaturated polyester resin using HDI trimer

“…So the chemical modification methods by reactive blending of UPR and hybrid polymer networks gradually developed to be the attractive routes [5][6][7] . The hybrid polymer networks based on polyurethane prepolymers and unsaturated polyester, or based on unsaturated polyester resin and epoxidized phenolic novolacs via reactive blending have been investigated [8] . Another approach was introduced rubber segments in the UP main chain by the reaction between isocynate-terminated liquid rubbers or polyisocyanate and hydroxyl-terminated unsaturated polyester [9,10] .…”