Propargylated novolac resins (PN) are known polymer binders for fibre‐reinforced plastic production. Unlike common phenolic resins, PNs are able to cure without volatiles, avoiding porosity formation in the final material. Otherwise, PN curing proceeds with a high exothermal effect (up to 1200 J/g), causing overheating that may result in destruction of material and equipment damage. The specific heat release limit was found with a curing kinetic study complemented with mathematical calculations to be 660 J/g for a quick and safe moulding process. A new commercially‐available catalyst for PN curing based on Ni(II) salts is recommended for composite pressing. Use of this catalyst helps to spread exothermal effects and simplify the curing process. It was shown that by varying reaction conditions, it is possible to adjust material properties such as Tg, char yield, curing temperature, and processing time.

No abstract

Novel propargyl that contains phenolic resins via azo-coupling reaction was synthesized. Peculiarities of curing process were investigated by differential scanning calorimetry analysis. Polymerization of resins with azo groups was estimated to be affected by radicals obtained at resin decomposition causing 10°C peak shift to lower temperatures in comparison with resin containing only propargyl group. At the same time, polymerization of triple propargyl bond was shown to not proceed at radical initiation until Cleisen rearrangement and chromene formation. Thermogravimetric analysis revealed increase of thermal stability by 170-190°C and char yield by up to 20% for modified resins in comparison with original novolac resin. Heat deflection temperature estimated by dynamic mechanical analysis was also shown to be increased by at least 110°C for modified resins in comparison with novolac resin. All the synthesized resins are soluble in acetone and used for preparation of unidirectional glass fiberbased composites. Flexural strength and modulus for modified resins-based composites were shown to increase by at least 25% and 10% correspondingly in comparison with novolac-based composite.

No abstract

No abstract