جستجوی مقالات مرتبط با کلیدواژه "ویژگی های حرارتی" در نشریات گروه "صنایع چوب و کاغذ"

In this study, the effect of changes in pH and molar ratio on the properties of melamine formaldehyde resin for impregnating decorative paper was investigated. The physical properties of the resin such as free formaldehyde, resin shelf life, and the percentage of resin solids contents were investigated in different conditions Also, the molecular structures of resin were studied using FTIR spectroscopy and thermal analysis of resins through TGA. The results showed that a higher pH improved the characteristics of the resin and melamine coating, while increasing the molar ratio of formaldehyde to melamine weakened the characteristics of the resin and coating. In addition, the results showed that the changes observed in the resin caused by The variables of molar ratio and pH have no significant effect on the thermal properties of the resin.

This study was focused on the preparation of an environmentally friendly nanocellulose based hydrogel in the form of pads. Hydrogels are hydrophilic three dimensional network with crosslinks, swells in water but don’t dissolve. In this research nanofibrillated cellulose and Hydroxyethyl cellulose with different ratio (1:1, 2:1, 3:1) were used to make hydrogel. Also, citric acid which has a significant advantage over other crosslinking agents in terms of toxicity and price, has been used in different amounts of 10% and 20% by weight to crosslink. In order to find optimal hydrogel preparation conditions, FTIR analysis, FESEM, time dependent swelling measurement and evaluating the thermal and rheological properties were performed. Samples with a lower ratio of nanocellulose to hydroxyethyl cellulose were found to be inappropriate due to the loss of their apparent integrity in the swelling measurement. According to FTIR results, cross-linking were performed only in samples with the highest ratio of nanocellulose to hydroxyethyl cellulose in different amounts of citric acid. Therefore, the hydrogel's characteristics were mainly influenced by the ratio of nanocellulose to hydroxyethyl cellulose and the amount of citric acid had less effect on these properties. These two successful final samples showed acceptable properties in other evaluated properties and led to the selection of optimal reactive ratios for the preparation of hydrogels for use in various industries, including the pharmaceutical industry.

In order to eliminate the harm of formaldehyde from panels bonded with UF resin to environment and human health at the source, the low volatile and nontoxic aldehyde of glyoxyal (G) was chosen to react with urea (U) to prepare the wood adhesive of urea-glyoxal (UG) resin a substitute for urea-formaldehyde (UF) resin. The urea-glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Also, the effect of nanoclay on physico-chemical, thermal and mechanical properties of UG resin was investigated. For this purpose, the prepared UG resin was mixed with 1, 2 and 3 wt% nanoclay by mechanically stirring for 5 min at room temperature. The physico-chemical properties (such as SPG, viscosity, solid content and gelation time) and dry shear strength of the prepared resin were measured according to standard methods. Also, the effect of nanoclay on curing temperature of UG resin was analyzed by Differential Scanning Calorimetry (DSC) device. The physico-chemical test results indicated that addition of nanoclay increased SPG, viscosity and solid content of UG resin and decreased gelation time in the prepared resin. Dry shear strength test results showed that increasing nanoclay content from 1 to 3 wt% increased shear strength of UG resin; as the panels containing 3% nanoclay exhibited the highest shear strength value and wood failure percentage. Based on DSC test results, hardening rate as well as enthalpy value of the prepared UG resin was decreased by addition of nanoclay.