Thermo-mechanical and adhesion properties of polymers and composites as affected by nature of epoxy isocyanate binders

The differential scanning calorimetry method was used to study kinetics of cyclo-polymerization of epoxy resins with di- and polyisocyanates of different nature. To reduce a temperature interval in which the reaction between epoxy novolac resin and isophoronodiisocyanate progresses, efficient catalysts — the complexes of zinc dichloride with imidazole and tributylphosphate — were proposed. Highly heat-resistant polymers and composites were obtained due to cyclic oxazolidones and isocyanurates contained in their structure. Adhesion capacity of epoxy isocyanate compositions to aluminium and its alloys was studied as well.

Improvement of the Mechanical Properties of Thermosetting-Binding-System-Based Composites by Means of Kneading Procedure Modification and Composite Formulation

By understanding the effects of the physical properties of individual input materials (e.g., binding system) on the physical and thermal properties of a composite material, the latter can be engineered in advance according to the desired properties and application. Often, a need to replace a specific component in a composite material arises, due to various reasons such as high raw material prices, product price reduction, environmental issues, improvement of properties, and others. In this study, we focused on the substitution of a phenolic novolac resin binding system and the reduction of compounding process temperature in combination with material throughput and screw speed variation of a phenolic-novolac-resin-based composite material, manufactured by kneading process using a co-kneader single screw extruder. Modifications were carried out in the interest of reducing production process cost and positive environmental effect due to reduction of energy consumption in the compounding process. We achieved great success in improvement of mechanical properties with all four substituted phenolic molding compounds (PMCs), while the decrease in thermal stability was the lowest for PMCs prepared at higher screw speeds and material throughput. The results indicated that higher screw speeds produce the best combination of mechanical and thermal properties of PMCs.

Production of Novolac Resin after Partial Substitution of Phenol from Bio-Oil

HighlightsBio-oil was used to produce novolac resin.Bio-oil interacted with phenol and altered the reaction rate and equilibrium.Comparable performance was observed with a low amount of substitution.Abstract. Commercially produced bio-oil with a high content of pyrolytic lignin was substituted for phenol in novolac phenol-formaldehyde (PF) resin production. The reaction progress was tracked, and products were analyzed. Bio-oil substitution resulted in lower conversion rates for both formaldehyde and phenol. Substitution higher than 10 mol% increased the ortho to para ratio and enhanced thermal decomposition of resin by providing an oxidative environment, while 10 and 20 mol% of substitution did not reduce the shear strength of the novolac resin. When mixed with hexamethylenetetramine (HMTA), the bio-oil substituted resins precipitated quickly around char particles, which allowed more resin application on the wood bonding surface. Further investigation found that bio-oil substitution (higher than 10 mol%) might have changed the reaction equilibrium and promoted reverse reactions releasing formaldehyde. Overall, less than 20 mol% phenol substitution by bio-oil with a high content of pyrolytic lignin can be effective in producing novolac resin. Keywords: Bio-oil, Formaldehyde, Lignocellulosic biomass, Novolac, Phenol, Pyrolysis.