Facultad Regional San Francisco

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Author: search.filters.author.Taverna, María E.Subject: search.filters.subject.laminates

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    Synthesis and mechanical characterization of high pressure laminates modified with Kraft lignin
    (255th ACS National Meeting Exposition New Orleans, 2018-04) Estenoz, Diana; Taverna, María E.; Nicolau, Verónica V.
    Phenol-formaldehyde resins (PF) are thermosetting polymers used as adhesives for plywoods and other structural wood products including high pressure laminates (HPLs). HPLs are composite materials comprised of a paper-based decorative surface and a substrate impregnated with PF resin. PF adhesives are synthesized using two reagents made from petrochemicals: phenol and formaldehyde. The substitution of such substances by natural products including lignin, tannin, and furfural among others has been increased in the last 20 years due to environmental and economic benefits [1]. Lignin is an inexpensive, abundant and non-toxic by-product from pulp production, used as replacement of P, due to its similar structure to PF resins. In this work, the industrial synthesis and characterization of three resol-type phenol-formaldehyde resins modified with 10, 20 and 30 wt% of Kraft lignin from hardwood were studied. The Kraft lignin was activated by hydroxymethylation in all cases. The resols characterization involved industrial measurements of free formaldehyde, viscosity, total solids and density. The resins were used for the industrial impregnation of Kraft-type paper and the production of laboratory laminates. The mechanical and thermal properties of the laminates were measured. Mechanical measurements included tensile, flexural, impact and interlaminar tests. Thermogravimetric and dynamic mechanical analysis were used for the thermal characterization. In addition, the aging of materials in water was studied. No significant differences in mechanical and thermal properties between traditional and modified materials were found with replacement up to 20 wt% of phenol. Modified laminates exhibited better water resistance due to the lignin hydrophobicity. For practical applications, this study suggests that resols modified with 20 wt% of Kraft lignin could be used for the production of HPLs, while resols modified with 30 wt% of lignin for postformable laminates. Industrial tests were carried out at Centro S.A, San Francisco, Córdoba.
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    Technical lignins modified by hydroxymethylation for the production of decorative laminates: Synthesis, characterization and mathematical modelling
    (2017-03) Nicolau, Verónica V.; Taverna, María E.; Estenoz, Diana
    Technical lignins are natural and renewable poly-phenolic polymers obtained mainly as a subproduct from the pulp industry. It presents a complex structure that depends on the wood type and the pulping process adopted to separate cellulose. Nowadays, lignins are used as a partial replacement of phenol (P) -non renewable resource, expensive and toxic- in the formulation of phenolic resins (PF). However, lignins must be chemically-modified in order to increase their reactivity toward formaldehyde (F). In the literature there is a lot of information about the use of PF resins modified with lignins (LPF) as adhesives for the production of particleboard. However, the use of LPF resols for paper impregnation to obtained laminates has been scarcely studied. A decorative laminate comprises a decorative surface and a substrate of papers. In this work, technical lignins (sodium lignosulfonate and kraft lignin) were activated by hidroxymethylation and used to replace P in PF resins. The resins obtained were employed to produce decorative laminates. The work involved: i) the modification of sodium lignosulfonate and kraft lignin from hardwood, by hydroxymethylation at different temperatures (40, 50 and 70 ºC) and pH (9 y12); ii) the characterization of the hydroxymethylation by spectroscopic and volumetric analysis; iii) the development of a mathematical modeling of hydroxymetilation of sodium lgnosulfonate and the estimation of kinetic constants of reactions; iv) the synthesis of industrial traditional and modified PF resins by replacement of 10, 20 and 30%w/w of P, v) the production of laminates and their characterization including dynamic mechanical analysis used to compare conditions of curing and the determination of tensile modulus, bending strenght, biaxial flexural impact strenght and Mode- I Interlaminar Fracture Toughness in both processing directions to evaluate the mechanical performance. In this work, the optimal conditions of hydroxymethylation were 50 ºC and pH<10. Simulated results from mathematical model were in accordance with experimental measurements. All resins (traditional and modified) had similar properties. The best conditions of curing used to obtained laminates were 70 kg/cm2 and 150ºC. The higher content of lignins in the PF resins decreased the crosslinking of laminates obtained. Finally, modified laminates exhibited mechanical properties comparable with those of traditional laminates, indicating a negligible depreciation of them. Industrial tests were carried out at Centro S.A, San Francisco, Córdoba.
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    Effect of Kraft Lignin from Hardwood on Viscoelastic, Thermal, Mechanical and Aging Performance of High Pressure Laminates.
    (Waste and Biomass Valorization, 2017-07-10) Taverna, María E.; Tassara, Oriana; Morán, Juan; Nicolau, Verónica V.; Estenoz, Diana; Frontini, Patricia
    In this work, the synthesis and characterization of phenol-formaldehyde resols modified with 10, 20 and 30 wt% of Kraft lignin (a waste from pulp industry) from hardwood were studied. In all cases, the Kraft lignin was activated by hydroxymethylation. The resols characterization involved industrial measurements of free formaldehyde, viscosity, total solids and density. The resins were used for the industrial impregnation of Kraft-type paper and the production of laboratory laminates. The mechanical and thermal properties of the laminates were determined. Mechanical measurements included tensile, flexural, impact and interlaminar tests. Thermogravimetric and dynamic mechanical analysis were used for the thermal characterization. In addition, the aging of materials in water was studied. No significant differences in mechanical and thermal properties between traditional and modified materials were found with replacement up to 20 wt% of phenol. Modified laminates exhibited better water resistance due to the lignin hydrophobicity. This work was carried out in collaboration with Centro S.A., San Francisco, Córdoba, Argentina, a high pressure-laminates industry.