Efeito da variação do ph e da temperatura de síntese no desempenho de adesivos à base de creosoto vegetal desmetilado-formaldeído

Santos, Crístian Bacelar; Pimenta, Alexandre Santos; Vital, Benedito Rocha; Barbosa, Luiz Cláudio de Almeida

doi:10.1590/s0100-67622003000400016

Cited by 4 publications

(2 citation statements)

References 5 publications

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“…No entanto, Santos et al (2003) estudando adesivos produzidos a partir de creosoto desmetilado, observou que, com a desmetilação os valores de resistência das lâminas foram inferiores aquelas coladas com adesivo sintetizado em laboratório (fenol-formaldeído), o que demonstra que a desmetilação é um processo ainda passível de estudo e com grande potencial quando feito na lignina para fins de produção de adesivo, como comprovado nesse trabalho.…”

Section: Tratamentosunclassified

Potencial da desmetilação da lignina na produção de adesivo para colagem de lâminas de madeira

Freitas

Jesus

Vital

et al. 2019

RCM

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RESUMO A lignina, maior fonte natural de polímero aromático fenólico, apresenta grande potencial para ser utilizado na síntese de novos adesivos, desde que sua reatividade seja alterada com a modificação de sua estrutura química. Diante disso, o objetivo do trabalho foi analisar a resistência ao cisalhamento na linha de cola da madeira de Eucalyptus sp., a partir da utilização de adesivos produzidos com lignina Kraft desmetilada com ácido clorídrico e fenolada. Foram utilizados seis tipos de adesivos, o comercial fenol-formaldeído, o sintetizado no Laboratório de Painéis e Energia da Madeira, o adesivo de lignina fenolada e três adesivos preparados com lignina desmetilada com ácido clorídrico no volume de 40 ml, 60 ml e 80 ml. Os adesivos foram caracterizados e utilizados para a colagem de lâminas, que foram submetidas ao teste de resistência ao cisalhamento por tração. Foi observado que os corpos-de-prova colados com o adesivo de lignina desmetilada (HCl-60ml) atingiram valores de resistência (5,18 MPa) superiores aos demais tratamentos. Dessa forma, os adesivos compostos com lignina desmetilada com ácido clorídrico e fenolada apresentam potencial de uso na fabricação de adesivos para colagem de lâminas de madeira. Palavras-chave: reatividade; biopolímero; estrutura química. Potential of lignin demethylation in the production of adhesive for bonding of wood veneersABSTRACT Lignin, most natural source of phenolic aromatic polymer, has a great potential to be used in the synthesis of new adhesives, since their reactivity is changed with the modification of its chemical structure. Thus, the objective of this study was to analyze the shear strength in the glue line of Eucalyptus sp., from the use of adhesives produced with lignin Kraft demethylated with hydrochloric acid and phenolated. Were used six types of adhesives, phenol-formaldehyde commercial, synthesized in panels Laboratory of Wood Energy, phenolated lignin adhesive and three prepared adhesives with demethylated lignin with hydrochloric acid in volume of 40 ml, 60 ml and 80 ml. The adhesives were characterized and used for bonding blades, which were subjected to tensile shear resistance test. It was observed that the specimens bonded with the demethylated lignin adhesive (HCl 60ml) reached resistance values (5,18MPa) higher than the other treatments. Thus, the adhesive compounds with lignin demethylated with hydrochloric acid and phenolated have a potential use in the manufacture of adhesives for bonding wood veneers.

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Section: Tratamentosunclassified

Potencial da desmetilação da lignina na produção de adesivo para colagem de lâminas de madeira

Freitas

Jesus

Vital

et al. 2019

RCM

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“…The author indicated that it was unlikely that pH altered the wood substrate sufficiently to influence the quality of bonding. Santos et al17 examined the effects of pH and synthesis temperature on the performance of thermosetting adhesive formulations based on demethylated wood creosote‐formaldehyde when used in bonding Araucaria angustifolia sheets. The pH's of the adhesive formulations were 12.00, 12.25, 12.50, 12.75, 13.00, 13.25, and 13.50.…”

Section: Introductionmentioning

confidence: 99%

Impact of curing condition on pH and alkalinity/acidity of structural wood adhesives

Zhang

Wang

Casilla

et al. 2010

J of Applied Polymer Sci

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Nine formulations were selected for evaluating the effect of different curing methods on pH and alkalinity or acidity of various structural wood adhesives. These included four phenol-formaldehyde (PF) resins with high pH, one phenol-resorcinol-formaldehyde (PRF) resin with intermediate pH, two melamine-urea-formaldehyde (MUF) resins, and two melamine-formaldehyde (MF) resins with low pH. The four curing methods used in the study were: (1) curing at 102-105 C for 1 h (based on CSA O112.6-1977), (2) four-hour curing at 66 C followed by 1-hour curing at 150 C (based on ASTM D1583-01), (3) curing at room temperature overnight (based on ASTM D 1583-01), and (4) cured adhesive squeezed out from glue lines of bonded shear block samples. The effect of the different methods on pH and alkalinity/acidity of the cured adhesive depended strongly on the individual adhesives. For the PF, the alkalinity was different for the different formulations in the liquid form, while in the cured form, the difference in the alkalinity depended on the curing method used. The MF and the MUF were the adhesives most affected by the method used. In particular, the MUF showed much higher cured film pH values when cured by method 2 compared to the other three methods, while both the cured MF and MUF exhibited quite variable acidity values when cured with the different methods. The PRF showed reasonably uniform cured film pH but varying acidity values when cured with the different methods.

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Evaluation of block shear properties of selected extreme‐pH structural adhesives by short‐term exposure test

Zhang¹,

Wang²,

Casilla³

et al. 2010

J of Applied Polymer Sci

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Nine structural adhesives with varying pH were selected to examine the effect of adhesive pH on wood-adhesive bond quality. The adhesives evaluated included four highly alkaline phenol-formaldehyde, one intermediate pH phenol-resorcinol-formaldehyde, two acidic melamine-urea-formaldehyde, and two acidic melamine-formaldehyde resins. Block shear specimens were prepared using Douglas-fir and black spruce wood. The adhesive performance was evaluated by measuring the shear properties (strength and wood failure) of the specimens tested at the dry and vacuum-pressure-redry (VPD) conditions. Adhesive pH, test condition, and wood species showed significant effects on shear properties. The different adhesives performed differently at the dry and VPD conditions. The high-pH adhesives (phenol-formaldehyde and phenol-resorcinol-formaldehyde) showed similar high wood failures at both test conditions and performed better than the low-pH adhesives (melamine-formaldehyde and melamine-urea-formaldehyde), especially after the VPD conditioning. The low-pH adhesives showed high wood failure at the dry condition, but wood failure decreased significantly after VPD conditioning for both species, indicating that the low-pH adhesives were less durable than the high-pH adhesives. High-pH adhesives did not have a negative impact on the strength of the bonded specimens.

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Efeito da variação do ph e da temperatura de síntese no desempenho de adesivos à base de creosoto vegetal desmetilado-formaldeído

Cited by 4 publications

References 5 publications

Potencial da desmetilação da lignina na produção de adesivo para colagem de lâminas de madeira

Potencial da desmetilação da lignina na produção de adesivo para colagem de lâminas de madeira

Impact of curing condition on pH and alkalinity/acidity of structural wood adhesives

Evaluation of block shear properties of selected extreme‐pH structural adhesives by short‐term exposure test

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