Characterization of Chemical Properties and Flow Parameters of Powdered Phenol-Formaldehyde Resins
Keywords:
Phenol-formaldehyde, molecular weight, flow measurementAbstract
A range of powdered phenol-formaldehyde resins was studied to examine the relationships between chemical structures and cure and flow parameters. Nine commercially available powdered waferboard/oriented strandboard resins and six laboratory-synthesized resins were chemically characterized by gel permeation chromatography and proton magnetic resonance spectroscopy. The flow properties of the resins were determined using thermal mechanical analysis and other empirical techniques. Those resins containing greater proportions of low molecular weight species tended to exhibit greater total flow than higher molecular weight resins, with most of this flow occurring at lower temperatures. For similar molecular weight distributions, resins containing fewer methylol groups exhibited more flow. A liquid resin sample converted to a powder by spray-drying showed a higher degree of condensation than the same resin converted by freeze-drying. A resin sample that had been stored for over seven years exhibited a major shift to higher molecular weight values and greatly reduced flow compared to a fresh sample of the same resin.References
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