Control of microvoids in resol phenolic resin using unsaturated polyester

Abstract

A major drawback of cured phenol formaldehyde resin is the presence of microvoids, resulting from the liberation of condensation byproducts. In an attempt to rectify this, phenolic resol resin was blended with unsaturated polyester (UP). UPs with various maleic anhydride (MA) to phthalic anhydride (PA) ratios were synthesized and later mixed with resol resin in various proportions. The best MA/PA ratio was found out by determining the specific gravity, acetone-soluble matter, and volatile content of the cast blend, cured under a satisfactory time-temperature schedule. The influence of acid value of the UP and the most desirable UP content were also investigated on the basis of the quality of the modified phenolic samples. The structural changes in the modified resin were studied using FTIR spectroscopy. Scanning electron micrographs (SEM) of the fractured surfaces were obtained to ascertain the extent of microvoids in the modified resin. Both thermogravimetric analysis results and SEM micrographs confirm the effectiveness of UP in reducing the microvoids in the cast resol resin. The tensile and impact strengths of the samples also reflect the superior quality of the resol phenolic resins that have been modified by UP.

Study on the preparation and mechanical properties of injection‐moulded wood‐based plastics

“…First, BM was an efficient method for breaking the three‐dimensional network structure of lignin and for increasing the accessibility of wood meal, thereby ensuring that agents can penetrate into the inner space of the wood meal to break the hydrogen bonds to achieve flowability rather than reacting at the fiber surface and, leaving a large number of hydrogen bonds in the cellulose. Second, PA is an excellent esterification reagent with a benzene ring, the presence of which could result in steric‐effects that prevent the formation of hydrogen bonds, and virtually no byproducts . Finally, although NMI may cause the degradation of wood meal, it is a perfect solvent, base, and catalyst .…”

“…Second, PA is an excellent esterification reagent with a benzene ring, the presence of which could result in steric-effects that prevent the formation of hydrogen bonds, and virtually no byproducts. 25 Finally, although NMI may cause the degradation of wood meal, it is a perfect solvent, base, and catalyst. 23 Those three factors ensure that an injection-mouldable wood-plastic can be achieved under mild conditions using a simple process, even without a high degree of esterification.…”

Unsaturated Polyesters and Vinyl Esters

“…Paramerwaran et al [157] studied the efficiency of UPR as a modifier of phenolic resole systems in order to control the formation of micro-voids that are formed by entrapment of condensation products and adversely affect the mechanical properties of the cured resin.…”

Nonisothermal curing of a solid resole phenolic resin

“…Phenolic resins are widely used thermosetting polymers because of their excellent flame retardance, temperature resistance, mechanical strength, electrical insulation, dimensional stability, and relatively low manufacturing cost 1–6. Their primary applications are in construction materials, electronics, aerospace, molded parts, insulating varnishes, laminated sheets, industrial coatings, fiber bonding, wood products, and automotive industries 7–9.…”

“…Their primary applications are in construction materials, electronics, aerospace, molded parts, insulating varnishes, laminated sheets, industrial coatings, fiber bonding, wood products, and automotive industries 7–9. Phenolic resins generally fall into two main classes, resole and novolac, in terms of their molecular structures and synthesis conditions 1, 10, 11. For example, resole phenolic resins are conventionally prepared by the reaction of excessive formaldehyde with phenol under alkaline conditions to produce a soluble and fusible prepolymer (resole) with many hydroxymethyl (CH 2 OH) functionalities located at the phenol nucleus of the backbone.…”