Effects of Initial Phenol-formaldehyde (PF) Reaction Products on the Curing Properties of PF Resin

Differential scanning calorimetry(DSC) was used to study the effects of varying NaOH concentrations on the thermochemical curing properties of 2,4-dimethylol phenol (2,4-DMP), and 2,6-dimethylol phenol(2,6-DMP). Analysis of the DSC curves showed significant differences in the thermochemical curing behavior of these compounds with increasing NaOH:DMP molar ratios, in terms of the peak shape, position of the reaction peaks, (T _p), along the temperature scale and energy of activation, E. The curves consisted of either a single, two or three exothermic peaks which indicated the occurrence of multiple reactions. One of these peaks was observed for the entire range of NaOH molar ratios, and is attributed to the self-condensation reaction. For the 2,4-DMP, NaOH had the effect of lowering the T _p of curing from 212°C in the uncatalyzed state to135°C between 0.15–0.75 molar ratios. The lowest value of E, however, was 111 kJ mole⁻¹, only through 0.45–0.60 molar ratios and this combined with the above, points to this concentration range as the optimum NaOH level. Similarly, the T _p of curing for the 2,6-DMP was lowered from 211°C in the uncatalyzed state, to a minimum of 116°C at the NaOH:2,6-DMP molar ratio of 0.45. At this ratio, Ealso had the lowest value of 117 kJ mole⁻¹ and this suggests that 0.45 molar ratio is the optimum NaOH level. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fracture mechanics at work in a steelmaking and engineering environment

An overview of fracture mechanics within the Research Division of a large international steel and engineering company is given. Fracture mechanics principles have been utilized to assess materials performance, structural integrity and component design. Examples are given of the applicability of these principles to steel making support activities and product usage in order to demonstrate the range and value of applications for fracture mechanics.     

Thermal Behaviour of Phenol-Formaldehyde (PF) Compounds

The self-condensation reactions of 2- and 4-mono-methylol phenols (2-MMP and 4-MMP), in the presence of varying concentrations of NaOH, have been studied by differential scanning calorimetry (DSC). The reaction exotherms were analysed to derive the activation energy, E_a, and the heat of reaction, H_T, for the condensation reactions. In the case of 2-MMP an increase in NaOH:2-MMP molar ratio caused an increased in E_a and a decrease in H_T up to a molar ratio of 0.6:1. However, for 4-MMP, an increase in NaOH concentration caused an increase in E_a up to a molar ratio of 0.3:1 beyond which there appeared to be no further effect. The presence of NaOH had no effect on H_T for this compound. The results suggest that in the range of NaOH concentration used the effect of NaOH was substantially greater on 2-MMP compared to 4-MMP. This revised version was published online in August 2006 with corrections to the Cover Date.