Study of rosin softening point through thermal treatment for a better understanding of maritime pine exudation

The temperature of pine rosin softening point was studied to better understand the phenomenon of resin exudation on the surface of pine boards. This problem may decrease strongly the aesthetical performance of wood used outside and is an important concern for the industry. To perform a reliable measurement of rosin properties with a small amount of sample, differential scanning calorimetry (DSC) and thermo mechanical analysis (TMA) techniques were investigated and the results compared. DSC curves on industrial rosin and acetone rosin extractives from maritime pine show a behavior similar to a glass transition in polymers. TMA measurements carried out on the same industrial rosin showed that the softening point is in the midpoint of the transition phase observed by DSC. The softening point temperature is about 45 °C for industrial rosin and about 50 °C for rosin extractives from maritime pine boards. These values are significantly lower than those usually found on other rosins measured by the ASTM E28-14 standard using the ring-and-ball method. When using heat treatment, it was observed for the first time that the thermal history of the sample can change its softening point temperature. With these results, it could be possible to develop a new strategy to reduce rosin exudation for exterior wood siding.     

Fabrication of superhydrophobic,antibacterial, and ultraviolet-blocking cotton fabric

Inspired by the superhydrophobic behavior of lotus leaf, a simple coating method was developed which could facilitate bionic creation of superhydrophobic surfaces on cotton textiles with a new functional properties. Silver nanoparticles (AgNPs) with a high deposition density were formed on the surface of cotton fabric through an alkali pre-activation followed by in situ reduction of silver nitrate. The Ag-coated fabric was then reacted with octyltriethoxysilane (OTES) to form a low surface energy layer on the fiber surface. The fabrics were characterized by ultraviolet-visible reflectance spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and X-ray diffractometry. Hydrophobicity properties were assessed by contact angle (CA) goniometry and shedding angle (SHA) technique. Antibacterial activity was measured against Staphylococcus aureus and Escherichia coli bacteria, and UV-blocking ability was measured using the AATCC method. SEM images showed the formation of AgNPs which were distributed uniformly on the fibers’ surface with a high coating density. Superhydrophobicity property of the treated fabric was confirmed with the CA of 156° and SHA of 8°. High antibacterial activity was observed without the reduction of inhibition size after coating with the OTES. The fabric also showed excellent UV-blocking with the ultraviolet protection factor of 266.01.     

Magnetic Wood-based Superhydrophobic Aerogel for Efficient Oil-Water Separation

The fabrication of directionally driven oil-water separation materials has great significance for the removal of oil spills and organic pollutants. In this study, an oil-water separation aerogel capable of directionally adsorbing oil was designed using an anisotropic wood aerogel with a layered structure and a top-down fabrication strategy. Specifically, a magnetic wood-based superhydrophobic aerogel (methyltrimethoxysilane (MTMS)/Fe₃O₄ wood aerogel) was developed through the in situ co-precipitation of Fe₃O₄ nanoparticles and chemical vapor deposition. Owing to its highly porous structure, lipophilicity, hydrophobicity (water contact angle of 160°), and high compressibility, the MTMS/Fe₃O₄ wood aerogel exhibits excellent oil-water separation performance and compression cycle stability. Additionally, the Fe₃O₄ endows the material with excellent magnetic and photothermal conversion capabilities. These excellent properties make MTMS/Fe₃O₄ wood aerogel a promising recyclable and sustainable oil-water separation material.     

In-treatment cooling during thermal modification of wood in soy oil medium: soy oil uptake, wettability, water uptake and swelling properties

Thermal modification of wood is a process which has gained wider acceptability as an alternative to chemical treatment in wood preservation. In order to maximize the benefits of this technique several options have been adopted including the use of soy oil in transferring the heat to the wood. Available information on thermal treatment in general and the oil method in particular show that there is need for further investigations on the possibilities of improving the available options in order to evolve new techniques. Thermal treatment of ponderosa pine (Pinus ponderosa P Laws ex C Laws) and black spruce (Picea mariana (Mill) BSP) in soy bean oil was carried out at 220 °C for 2 hours followed by cooling inside the hot oil 180 °C and 135 °C. The surface wettability, (contact angle), amount of oil uptake, water absorption and thickness swelling were determined thereafter. The oil uptake ranged from 88 to 93.3% in the permeable ponderosa pine sapwood and from 6.1 to 11.3% in the refractory black spruce with the uptake increasing with cooling time but decreasing with increasing depth of wood in both species. Thermal modification in soybean oil increased the wettability of the surface to water (reduced contact angle). However, there were no significant changes to the surface energies due to in-treatment cooling, as determined by contact angles of water, glycerol, ethylene glycol, and formamide. There were reductions in the hydrophilic behaviour and swelling of wood as a result of the thermal treatment; in-oil cooling resulted in greater hydrophobicity and dimensional stability in the wood. In both species, there were greater reductions in water uptake and swelling with increasing cooling time.     

超疏水聚酯滤布的性能及其在油水分离中的应用

为改善纳米二氧化硅的分散性,提升其与聚酯滤布的结合力,采用巯丙基三甲氧硅烷对纳米二氧化硅进行表面修饰,并通过浸渍-涂覆的方法将修饰后的二氧化硅负载在聚酯滤布表面,得到超疏水滤布。通过场发射扫描电镜、光电子能谱仪、傅里叶变换红外光谱仪及特征X射线能谱仪等对滤布进行了微观形貌、结构、元素及价态等方面的分析。结果表明:滤布表面均匀负载的低表面能硅树脂及其在滤布表面构建的微纳米多级凸起结构赋予滤布超疏水性,接触角高达156°;该滤布耐溶剂性能优良,在不同有机溶剂中浸泡72 h后,接触角仅下降1°~4°,滤布兼具高强度、超疏水/超亲油的特性。     

Migration of titanium dioxide from PET/TiO2 composite film for polymer-laminated steel

PET/TiO₂ composite film is the most widely used film for polymer-laminated steel, and the migration of TiO₂ is very important for the safety evaluation of its packaged food. Microwave digestion, wet digestion and dry ashing were used for pretreatment of composite film to determine the content of TiO₂ in composite film. Migration tests were carried out at 40°C, 60°C and 80°C 4% using acetic acid and 50% ethanol as the acid and ester food simulants. The migration amount of TiO₂ was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). With increasing temperature and time, the migration of TiO₂ increased. In 4% acetic acid, the migration amount of TiO₂ at 40°C for 10 days was 1.88 mg kg^?1 and the migration amount at 80°C for 8 h was 3.32 mg kg^?1, indicating that the effect of temperature on migration was more obvious. Under the same conditions, the migration amount of TiO₂ in 4% acetic acid was greater than in 50% ethanol. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC) were used to analyse the crystal structure, morphology, chemical groups and thermal properties of the film before and after the migration tests. The results showed that filmTiO₂ had a stable rutile type crystal structure and it was almost uniformly distributed. PET and TiO₂ were combined with strong chemical bonds. After TiO₂ migration, the crystallinity and the glass transition temperature (Tg) of the film decreased, but the change of melting temperature (Tm) was not obvious.     

Evaluation of the content of TiO2 nanoparticles in the coatings of chewing gums

Titanium dioxide is a metal oxide used as a white pigment in many food categories, including confectionery. Due to differences in the mass fraction of nanoparticles contained in TiO₂, the estimated intakes of TiO₂ nanoparticles differ by a factor of 10 in the literature. To resolve this problem, a better estimation of the mass of nanoparticles present in food products is needed. In this study, we focused our efforts on chewing gum, which is one of the food products contributing most to the intake of TiO₂. The coatings of four kinds of chewing gum, where the presence of TiO₂ was confirmed by Raman spectroscopy, were extracted in aqueous phases. The extracts were analysed by transmission electron microscopy (TEM), X-ray diffraction, Fourier Transform Raman spectroscopy, and inductively coupled plasma atomic emission spectroscopy (ICP-AES) to establish their chemical composition, crystallinity and size distribution. The coatings of the four chewing gums differ chemically from each other, and more specifically the amount of TiO₂ varies from one coating to another. TiO₂ particles constitute the entire coating of some chewing gums, whereas for others, TiO₂ particles are embedded in an organic matrix and/or mixed with minerals like calcium carbonate, talc, or magnesium silicate. We found 1.1 ± 0.3 to 17.3 ± 0.9 mg TiO₂ particles per piece of chewing gum, with a mean diameter of 135 ± 42 nm. TiO₂ nanoparticles account for 19 ± 4% of all particles, which represents a mass fraction of 4.2 ± 0.1% on average. The intake of nanoparticles is thus highly dependent on the kind of chewing gum, with an estimated range extending from 0.04 ± 0.01 to 0.81 ± 0.04 mg of nano-TiO₂ per piece of chewing gum. These data should serve to refine the exposure scenario.     

Effect of oil type, temperature and time on moisture properties of hot oil-treated wood

This paper focuses on the moisture properties of wood treated in palm oil-, soy oil- and slack wax for different processing times and temperatures. Also, the relative importance of oil uptake and thermal modification on the wood moisture properties is investigated. Slack wax was better than palm oil or soy oil in improving the moisture performance of thermally treated wood, and treatment at 220 °C was superior to treatment at 200 °C, with 4 h being generally better than 2 h treatment. Water absorption in samples treated with wax at 100 °C or 160 °C was similar to that in samples treated at high temperatures while improved anti-shrink efficiencies (ASE) and lower hygroscopicities occurred only for the high temperature treatments. Chloroform extracted samples treated at high temperature with palm oil or soy oil had relatively similar hygroscopicity and ASE properties compared to unextracted samples, but had greatly increased water absorption properties. These results confirm that chemical reactions in wood resulting from the heat treatment account for the main improvements of wood properties in reduced hygroscopicity and improved dimensional stability, while the oil absorbed by wood reduces the rate of water absorption.     

Effect of grain orientation and surface wetting on vertical density profiles of thermally compressed fir and spruce

The effects of grain orientation and surface wetting on wood densification by compression in a hot press were evaluated for two commercial Canadian wood species, balsam fir (Abies balsamea) and black spruce Picea mariana. The vertical density profiles (VDP) of wood densified at 180 °C could be engineered to achieve different properties depending on press closing rate, wood permeability and annual ring orientation. The lower permeability of spruce caused it to split frequently during hot pressing. For balsam fir, at a press closing time of 2 min, the compressed wood with an original grain angle of 0° (radial compression) shows widened high density bands due to collapse of low density earlywood adjacent to the dense latewood. All grain orientations show higher density areas close to the wood surfaces similar to those of wood-based composites. However, when wood was preheated without pressure for 5 min followed by a press closing time of 2 min, water migrated to and plasticized the board centre causing it to be densified while the surface density remained low. Wood surface plasticizing with water or urea solution causes some localized surface densification, but the effect was not great.     

The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C

Heat-treatment changes the chemical and physical properties of wood. Wood polymers are degraded, dimensional stability is enhanced, equilibrium moisture content is lowered, colour darkens and biological durability is increased. The properties of heat-treated wood have been researched considerably, but the differences between sapwood and heartwood have not been reported separately. In this research, water absorption differences between sapwood and heartwood of Scots pine and Norway spruce heat-treated at temperatures 170 °C, 190 °C, 210 °C and 230 °C were investigated. The results were compared to industrially kiln-dried reference samples. Water absorption was determined with a floating test based on the EN 927-5 standard. The heartwood of both wood species absorbed less water than sapwood. Heat-treatment evidently decreased the water absorption of spruce and pine heartwood. The higher the heat-treating temperature, the lower the amount of absorbed moisture. However, a very interesting exception was pine sapwood, whose water absorption actually increased with heat-treatment after the three lowest heat-treatment temperatures compared to the reference material. Water absorption did not decrease until the heat-treatment temperature was 230 °C.     

Determining the curing parameters of furfuryl alcohol for wood modification by nanoindentation

Wood furfurylation is a very promising modification process, which can greatly improve several important properties of wood simultaneously. The polymerization degree of furfuryl alcohol (FA) in wood significantly influences the performances of modified wood. However, it is normally time-consuming and expensive to determine the curing parameters of a new FA solution formula for a target wood species, as the process requires lots of lab-scale experiments. To address this challenge, nanoindentation was used to determine the hardness and elastic modulus of FA resin which are cured with different catalyst content, curing time and curing temperature, assuming that these mechanical properties should closely relate to the polymerization degree of cured FA (resin). Single-factor experiments were designed to obtain preliminary curing parameters. Three key curing parameters were selected, namely the catalyst content of maleic anhydride (1.5, 3, 5 %), curing time (2, 3, 4, 5, 6 h) and curing temperature (95, 105, 115, 125 °C). The proposed set of curing parameters based on the nanoindentation results are 3 % maleic anhydride, 3 h curing time and 105 °C curing temperature. This set of parameters was slightly modified and then used as the starting process parameters for Masson pine modification, which resulted in greatly improved wood properties. Therefore, the method proposed in this study offers an effective and time-saving means of developing new processes of wood furfurylation.     

Liquid chromatography-negative ion electrospray mass spectrometry detection of maleic anhydride-modified wood rosin for assessing quality of commercial citrus fruit coatings

Abstract Differently from Europe (EU), in United States (US) is allowed the use of citrus coating formulations containing pentaerythritol-ester of maleic anhydride-modified wood rosin, imputed of allergenic effects. To control the waxes used in the European citrus coating operations, a reliable LC/PDA/ESI–MS method for the simultaneous detection of abietic acid (AA) and maleopimaric acid (MPA) was developed. AA is the main resin acid, while MPA is the major product of the modification of rosin with maleic anhydride. Because of the lack of commercial standard, the MPA was synthesized in our laboratory heating AA and maleic anhydride together at 190 °C. The method was successfully applied to 190 samples of coated citrus fruits and 19 commercial waxes collected in the Italian market. The results demonstrated that about 7.5% of the investigated citrus samples contained both AA and MPA, evidencing the illicit employ of unpermitted waxes in citrus coatings. All the analyzed waxes resulted instead regular. The proposed method could be routinely applied in the control laboratories to assess quality of European citrus fruit, preserving the consumers from the commercial illicit and from potential toxicological consequences.     

Facial preparation of superhydrophobic and superoleophilic textiles by depositing nano-SiO2 for oil–water separation

In this study, a facile one-step dip-coating approach was reported for the fabrication of superhydrophobic and superoleophilic cotton fabrics for oil–water separation. By depositing the hydrophobic nano-SiO₂ on the micro-scale cotton fabric surface, the combination of the nano-SiO₂ and the micro-roughness cotton fabric created a micro/nano-binary surface roughness and presents superhydrophobicity and superoleophilicity. SEM, EDS, and TGA result shows that the treated cotton fabric was completely covered by the nano-SiO₂ particles when the nano-SiO₂ particles was about only 3.6 wt% of the pristine cotton fabric. The separation efficiency of the fabricated superhydrophobic and superoleophilic fabric was calculated up to 98.3 wt%. The one-step production technique described here is realizable for industrial use, relatively mild processing conditions, and large-scale fabrication.     

Moisture adsorption behaviour of esterified rubber wood (Hevea brasiliensis)

) esterified with acetic anhydride, maleic anhydride and phthalic anhydride was studied for moisture adsorption behaviour. FTIR spectroscopic technique was used to analyse the chemical changes in the wood through the correspondent reactions. Spectra indicated increasing intensity of the C=O and C-O stretching bands, and reduction in O-H stretching vibrations that reflects formation of less hygroscopic ester bonds with hydroxyl groups of cell wall polymers. Moisture adsorption isotherms show low equilibrium moisture content in esterified wood at all relative humidity values as compared to a control. The adsorption data was analysed by applying Hailwood-Horrobin theory which separated the adsorbed water into hydrated water and dissolved water corresponding to mono-layer and multi-layer adsorption. Curve for M_h and M_s were similar in pattern for esterified wood and control with different magnitude. Low M_h and M_s in esterified wood indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride treatment was found most effective in reducing hygroscopicity of wood.     

Inactivation of Foodborne Pathogens by NiO/TiO2 Composite Nanofibers: A Novel Biomaterial System

This study presents the fabrication and characterization of novel NiO/TiO₂ composite nanofibers and their antibacterial activity. The utilized NiO/TiO₂ composite nanofibers were prepared by electrospinning of a sol–gel composed of nickel nitrate hexahydrate, titanium isopropoxide and poly(vinyl acetate). The obtained electrospun nanofiberous mat was vacuum dried at 80 °C and then calcined at 600 °C in air for 2 h. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis and transmission electron microscopy. The antibacterial activity was tested against four common foodborne pathogenic bacteria viz., Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae by minimum inhibitory concentration (MIC) method taking five different concentrations (5–45 μg/ml). Our investigation reveals that the lowest concentration of NiO/TiO₂ composite solution inhibiting the growth of tested strains was found to be 5 μg/ml. TEM analysis demonstrated that the exposure of the selected microbial strains to the composite nanofibers led to disruption of cell membranes and depressed the activity of some membranous enzymes, which caused bacteria to die eventually. Furthermore, the results illustrate that the combination of NiO and TiO₂ can be synergistic and resulted in superior antimicrobial activity of NiO/TiO₂ composite nanofibers. To sum up, novel NiO/TiO₂ composite nanofibers that possess large surface-to-volume ratio with excellent antimicrobial activity were fabricated that can be used to inhibit the microbial growth associated with food stuff.     

Chemical investigations on boiling process waters in face veneer production

Boiling processes in veneer industry generate large amounts of process water replete with dissolved wood extractives. In the present study the chemical composition of boiling waters from 18 industrially treated wood species were investigated. Contamination levels of the boiling waters varied within a wide range depending on the different extractive contents of the processed wood species and operational conditions. Boiling wood species with high extractives content, heated over several days at temperatures above 80 °C, generate highly loaded waste waters with chemical oxygen demands (CODs) of up to 7000  mg l^-1. The determination of the elemental composition, using optical emission spectrometry (ICP-OES), showed iron contents of up to 10 mg l^-1. Phenolic compounds were in a range of 40 to 900 mg l^-1. Flavonoid compounds and phenolic acids were identified in the boiling waters by liquid chromatography (RP-HPLC-UV). The results confirm the need for water treatment facilities to establish a recycling process and to avoid discolourations of the wood by accumulated wood extractives.     

Modification of wool fabric treated with tetrabutyl titanate by hydrothermal method

Nanometer-sized TiO₂ particles prepared by hydrothermal precipitation method were first immobilized on the surface of wool fiber using tetrabutyl titanate, and then dyed with C.I. Reactive Blue 69. Scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and thermal gravimetric analyses were used to characterize the morphology, crystalline phase, chemical structure, and thermal stability of TiO₂-loaded fiber. The properties of diffuse reflectance spectrum, whiteness, dye exhaustion rate, fixation rate, K/S value, and color fastness for wool fabrics before and after treatment were also measured. The investigation indicated that when wool fabric was treated with tetrabutyl titanate aqueous solution at 120°C for 5?h, pure anatase TiO₂ particles aggregated by nanocrystalline grains of 10?nm or so were synthesized, and were grafted onto fiber surface by chemical reaction. When compared with the untreated wool fabric, the onset decomposition temperature of the TiO₂-loaded fabric increased. The capability of TiO₂-loaded fabric against ultraviolet radiation was enhanced. The fabric whiteness, exhaustion rate, fixation rate, and K/S value decreased to some extent because of the existence of the TiO₂ particles. The color fastnesses to dry and wet rubbing had no change. The K/S value of TiO₂-loaded fabric increased after being brushed. The color fastness to artificial light was also improved.     

Reducing the set-recovery of surface densified solid Scots pine wood by hydrothermal post-treatment

The mechanical properties of wood surface are of particular interest in applications where mainly the surface is exposed to use, such as flooring boards. Wood surface densification aims to improve these properties by compressing only the first few millimeters beneath the surface. Scots pine (Pinus sylvestris L.) sapwood was surface densified to three degrees of compression at 150 °C using a specially designed heated press. Half of the specimens were hydrothermally post-treated at 200 °C. To study the influence of the degree of compression and hydrothermal post-treatment on the set-recovery, specimens were subjected to water soaking-drying-cycles. The surface densification process resulted in a minor mass loss regardless of the degree of compression, whilst the hydrothermal post-treatment led to an average mass loss of 3.8 % in surface densified specimens and of 4.1 % in control un-densified specimens. Furthermore, considerable fixation of compressive deformation was obtained by hydrothermal post-treatment at 200 °C.     

Synthesis and hydrophobic evaluation of the electro-spun nano-TiO2/PET fibrous bats after treatment with an alkaline solution and fluorocarbon material

Superhydrophobicity of a substrate is the result of a low surface energy and proper surface roughness. In the present research, the potential roughening effect of using nano-TiO₂ (NT) in a PET electro-spinning solution followed by an alkaline modification of the synthesized bats was investigated to create appropriate surface roughness while a low surface energy was achieved in owing to a layer of fluorocarbon coating. The results were evaluated via employing FTIR, SEM, digital microscopy, 3 M water repellency, water contact angle, and sliding angle. The best result of hydrophobicity was achieved by the alkaline modified-fluorocarbon coated NT (5.5%)/PET fibrous bat with the 3 M water repellency of 10, contact angle of more than 150° (155.9 ± 0.1°), and sliding angle of less than 10° (6.1 ± 1.9°) due to a multiscale surface roughness obtained by the fibrous bat structure itself, and roughening effect of the NT as well as alkaline solution surface etching.     

The wettability and bonding performance of densified VTC beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) bonded with phenol–formaldehyde adhesive and liquefied wood

The influence of viscoelastic thermal compression (VTC) on surface wettability and bonding performance of wood was evaluated. Low quality beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) were densified with the VTC process to different degrees of densification. Control and densified strips were bonded with phenol–formaldehyde (PF) adhesive and liquefied wood (LW). Shear strength of bonded assemblies was determined after 1 week of conditioning at 20 °C and relative humidity of 65 %. Wettability was determined on the basis of the contact angle of water, PF adhesive, and LW using the Wilhelmy method. Results showed that densification of beech and spruce wood did not significantly affect the shear strength of specimens bonded with PF adhesive. In beech assemblies bonded with LW shear strength decreased significantly with increased density, whereas in bonded spruce specimens decrease of shear strength was not significant. It was found that degree of densification and bonding process used in the study were not appropriately chosen for spruce wood specimens, since major deformations after the bonding process occurred. Wettability changed significantly after densification. Contact angle of water and LW increased after densification, whereas contact angle of PF showed inverse trend and decreased after VTC process. Furthermore, the degree of densification had a minor effect on the wettability.