Biological damage function models for durability assessments of?wood and wood-based products in building envelopes

A durability assessment system that links an advanced computer model for structural and hygrothermal analysis with damage functions is currently being developed. The computational system has different modules that calculate the different structural and hygrothermal responses of wall systems. Outputs of these modules are input to the module of damage function models to calculate damage, performance and service-life of building envelopes. Details of biological damage functions implemented in the damage function module of IRC??s durability assessment system are presented. The biological damage functions trace deterioration in wood materials subjected to hygrothermal loads that favor fungal growth. The developments of the models are based on recent biological experimental data from the literature. Equations to calculate various parameters in the model are presented and the application of the developed models is demonstrated using air leakage of warm and humid indoor air in a typical wood-frame construction in Ottawa.     

Characterization of a formaldehyde-free cornstarch-tannin wood adhesive for interior plywood

This study investigated the physical properties (rheological and thermogravimetric analysis) of cornstarch-tannin adhesives and the mechanical properties (dry tensile strength and 3-point bending strength) of plywood made using cornstarch-tannin adhesives. This adhesive was evaluated for its utility in interior plywood manufacture. The optimum cure temperature and cure time of cornstarch-tannin adhesives were 170°C and 4?min, respectively. Plywood bonded with formaldehyde-free cornstarch-tannin adhesive exhibited excellent mechanical properties comparable to commercially available phenol-formaldehyde plywood adhesives. It was found that cornstarch-tannin panels which do not contain formaldehyde and with an emission equal to that of heated but unbound wood can be obtained by the use of hexamethylenetetramine (hexamine) as hardener. The work has indicated that an environmentally friendly wood adhesive can be prepared from a natural renewable resource (cornstarch and wattle tannin) for bonding interior-type plywood.     

Development and optimization of a new formaldehyde-free cornstarch and tannin wood adhesive

The development and optimization of a new, environment-friendly adhesive made from abundant and renewable cornstarch and tannin is described in this study. At present, the production of wood composites mainly relies on petrochemical- and formaldehyde-based adhesives such as phenol-formaldehyde (PF) resins and urea-formaldehyde (UF) resins. Formaldehyde-free cornstarch plus tannin adhesives were evaluated for mechanical and physical properties (shear strength, rheological characterisation and thermogravimetric analysis). First, optimized conditions for the preparation of cornstarch-sodium hydroxide wood adhesives were determined. The parameters studied were the following: total solids content of the adhesives, sodium hydroxide concentration and sodium hydroxide/cornstarch volume ratio. The highest shear strength results appeared to be 0.5 sodium hydroxide/cornstarch volume ratio when using concentrations of cornstarch (65% p/v H₂O) and sodium hydroxide (33% p/v H₂O). The optimum cure temperature was 170 °C and the cure time 4 min. The addition of two types of tannin-based adhesives, Mimosa and Quebracho, with hexamethylenetetramine (hexamine) hardener to the cornstarch-sodium hydroxide formulation improved the shear strength and decreased the viscosity of adhesives.     

The influence of material properties on the amount of twist of spruce wood during kiln drying

The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20°/m in the case of boards close to the pith, and decreased to less than 4°/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage.     

Barrier and tensile properties of whey protein–candelilla wax film/sheet

Barrier and tensile properties were compared for whey protein isolate- (WPI-) based solution-cast films, extruded sheets and extruded sheets subsequently thinned into films by compression. Solution-cast films were made from mixtures of WPI and glycerol (GLY) in water. Sheets were made by feeding WPI, GLY, and water to a twin-screw co-rotating extruder. In each case, candelilla wax (CAN) was added at 0, 5 or 7.5 g CAN/100 g dry mix to determine the effect on the barrier and tensile properties. Compressed extruded films were made by thinning extruded sheets using a Carver Press equipped with heated platens. Water vapor permeability (WVP), oxygen permeability (OP) and tensile properties were measured. Scanning electron microscopy (SEM) images were also taken.     

Improved oxidative barrier properties of emulsions stabilized by silica–polymer microparticles for enhanced stability of encapsulants

The materials encapsulated within oil-in-water emulsions are prone to oxidation due to the permeation of oxidative species across the oil–water interface and into the lipid phase. Thus, the oxidative barrier properties of the interfacial layer are pivotal in reducing oxidation within emulsified oils. To enhance these barrier properties, we explored an approach of stabilizing emulsions using ‘silica–polymer microparticles’. We hypothesize that these microparticles will enhance the barrier properties of emulsion interfaces by mechanisms such as higher interfacial thickness and quenching of oxidative species before they permeate into the emulsions. Silica–ε-polylysine (Si–EPL) microparticles were synthesized by electrostatic aggregation of anionic silica nanoparticles and cationic ε-polylysine in the aqueous phase. Formation of Si–EPL microparticles was validated using particle size, ζ-potential and scanning electron microscopy measurements. These microparticles were subsequently used for emulsion stabilization. Emulsions stabilized by silica nanoparticles alone were used as control. Oxidative barrier properties were determined by measuring the rate of permeation of peroxyl radicals from the aqueous to the oil phase of the emulsion using fluorescence based methods. The rate of permeation of peroxyl radicals was significantly lower in emulsions stabilized by Si–EPL microparticles compared to that stabilized by silica nanoparticles. One of the mechanisms responsible for the observed effect was enhanced quenching of peroxyl radical by Si–EPL microparticles before they can permeate inside the oil phase. To further validate the results, stability of a model bioactive compound, retinol, encapsulated in these emulsions was compared. Consistent with peroxyl radical permeation measurements, emulsion stabilized by Si–EPL microparticles significantly improved the oxidative stability of retinol compared to that stabilized by silica nanoparticles alone. Thus, by engineering the physical properties of the interfacial layers, the oxidation of the encapsulants in emulsions can be controlled.     

Influence of ι-carrageenan, pectin, and gelatin on the physicochemical properties and stability of milk protein-stabilized emulsions

This study evaluated the stability of bilayer emulsions as a function of secondary layer composition and pH. Primary emulsions were formulated with 5% soybean oil, 1% protein from nonfat dry milk (NDM) powder as emulsifier and ι-carrageenan (ι-carr), low-methoxyl pectin (LMp), high-methoxyl pectin (HMp), or gelatin as secondary layers. ζ-Potential values increased for each emulsion as the pH decreased, with ι-carr emulsions being consistently more negatively charged than primary emulsions and significantly more stable. ζ-Potential values were not always correlated to emulsion stability. Gelatin secondary emulsions at pH 3 and HMp secondary emulsions at pH 7 were unstable due to the presence of depletion flocculation. In addition, LMp secondary emulsions stability at pH 7 might be due to calcium bridging, which increased the emulsion's viscosity. Overall, the stability of NDM emulsions was improved when ι-carr and LMp were used as secondary layers at pH 7 and 5, and when ι-carr and HMp were used as secondary layers at pH 3. Increased stability of these systems can be attributed to a second homogenization step used to formulate the secondary emulsions and to the presence of Ca(+2) in the NDM. Results from this research show that the stability of bilayer emulsions is driven by the presence of depletion flocculation, droplet charge, droplet size and distribution and viscosity. PRACTICAL APPLICATION: The use of everyday ingredients (nonfat dry milk powder, gelatin, pectin, and carrageenan), which are understood and accepted by the average consumer, creates label-friendly products that are the wave of the future. Stable emulsions can be formed using these ingredients at various pH. Understanding the stability and how the pH impacts the physicochemical characteristics and stability of these emulsions will enable manufactures to use ordinary ingredients to create healthier products (for example, low-fat dressings, sauces, dips, and beverages).     

Influence of different β-glucans on the physical and rheological properties of egg yolk stabilized oil-in-water emulsions

The objective of this study was to obtain additional information on the influence of different β-glucan preparations, i.e. curdlan (CL), barley (BG), oat (OG), and yeast (YG) β-glucans, on the physical and rheological properties of egg yolk stabilized oil-in-water emulsions containing 20% oil. The emulsion without β-glucan (REF) was also prepared as a reference. Addition of CL and OG increased emulsion oil droplet sizes, whereas BG and YG showed no effect. Emulsion microstructures revealed that β-glucans induced flocculation of the oil droplet in the following order: CL > BG ≈ OG > YG. Dynamic oscillatory shear tests indicated that all emulsions exhibited weak gel-like characteristics which were enhanced by β-glucans addition as evidenced by an increase in G′ and a decrease in tan δ values. Flow tests showed that β-glucans enhanced thixotropy and yield stress of the emulsions. Stability tests demonstrated that β-glucans addition improved creaming stability of the emulsions during storage possibly due to an increase in viscosity of the continuous phase and/or a formation of a three-dimensional droplet network. CL exhibited the most pronounced effects on the aforementioned properties of emulsions compared to the other β-glucans tested. YG gave emulsion with higher viscoelastic properties and yield stress but lower stability than those made with BG or OG, indicating complex relationship between rheology and stability of these emulsion systems.     

Degradation of β-carotene in amorphous polymer matrices. Effect of water sorption properties and physical state

BACKGROUND: The use of encapsulation in amorphous matrices of carbohydrate and/or polymer formed during dehydration processes to enhance the stability and retention of labile compounds is increasing in the food and pharmaceutical industries. Efforts to improve encapsulating properties have been made using mixtures of carbohydrates with proteins or gums in different proportions. The objective of the present work was to study the stability of encapsulated β‐carotene and its degradation kinetics in maltodextrin/gum arabic and maltodextrin/gelatin matrices in relation to the physical properties and state of the dehydrated matrix. RESULTS: The degradation of β‐carotene followed a first‐order kinetic model of fractional retention for all encapsulating matrices. The Guggenheim–Anderson–de Boer (GAB) model was adequate to describe the sorption isotherms of the studied systems. β‐Carotene losses were observed mainly at relative humidities (RHs) above the glass transition temperatures (T_g) of the corresponding systems, where the matrices were fully plasticised and collapsed (75 and 92% RH). At these high RHs the best β‐carotene retention was obtained in the system containing gum arabic. CONCLUSION: The results showed that pigment degradation was determined by the physical state of the matrix, related to the degree of collapse. They represent a contribution to the knowledge of physical factors that affect the retention kinetics of labile biomolecules encapsulated in dehydrated matrices. Copyright © 2011 Society of Chemical Industry     

Influence of compounding conditions,treatment of wood particles with fire-retardants and artificial weathering on properties of wood-polymer composites for façade applications

European Journal of Wood and Wood Products - Various fire-retardants (FR) for the pre-treatment of wood flour, for example, ammonium polyphosphate and different formulations based on phosphorus-...     

Evaluation and improvement of thermo-physiological comfort properties of firefighters’ protective clothing containing super absorbent materials

In this research, super absorbent materials were incorporated into the internal layer of the firefighters’ protective clothing with the aim of increasing absorption of sweat to improve the thermo-physiological comfort properties. The performance properties were evaluated following the standard test methods (ISO 6942:2002 and ISO 9151: 1995(E)) and the thermo-physiological comfort-related properties were evaluated by measuring the transport properties such as air permeability, water sorption and evaporation, thermal resistance and water vapour resistance of the fabric assemblies with super absorbent materials. The results indicated that it is possible to improve the comfort properties of the protective clothing by the incorporation of super absorbent materials into the internal layer. The use of super absorbent materials is likely to help in the absorption of sweat in higher amount and keeping the skin and internal microclimate dry, which in turn improves the comfort level. The performance properties of all the combinations satisfied the requirements for firefighter’s clothing as mentioned in AS/NZS 4967-2009.     

Polyborate ions’ influence on the durability of wood treated with non-toxic protein borate preservatives

¹¹B NMR spectra of the reaction products present in solutions of boric acid and protein such as albumin were done to determine the boron species present in protein borate wood preservatives. At acid pHs only the undissociated H₃BO₃ at 20 ppm occurs, while at alkaline pH the signals of the charged and uncharged boron atoms at 16 ppm and 12.6–13.7 ppm of the three ionic species [B(OH)₄]^–, [B₃O₃(OH)₄]^–, [B₃O₃(OH)₅]^2– occur. A third much smaller intensity signal at 1.7–1.8 ppm due to the reaction of a polyborate compound with the protein is also present. Application of heat causes a relative increase in the proportion of the latter two signals indicating both an increase of charged structures in solution and of the proportion of boron ions having reacted with the protein, the higher temperature having increased its solubility. This is compared and related to the effectiveness of albumin borate at different pHs and in relation to the different extent of leaching of boron species in both laboratory and field trial experiments. Both laboratory and field trials are reported. This is also related to previous findings as regards the effectiveness of proteins of different isoelectric point when used in protein borates wood preservatives, and to the influence of pH on the performance of these wood preservatives.

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Einfluß der Polyborationen auf die Dauerhaftigkeit von Holz nach Behandlung mit nicht-toxischen Proteinboraten

Zusammenfassung ¹¹B NMR-Spektren der Reaktionsprodukte in Lösungen von Borsäure und Albumin wurden angewendet, um die erwünschten Komponenten in Holzschutzmittel auf Proteinborat-Basis zu bestimmen. Im sauren Bereich liegt nur undissozierte Borsäure vor (bei 20 ppm). Im Alkalischen erscheinen die Signale der geladenen und ungeladenen Boratome bei 16 ppm und 12,6–13,7 ppm, die als komplexe Ionen der Form [B(OH)₄]^–, [B₃O₃(OH)₄]^–, [B₃O₃(OH)₅]^2– vorliegen. Ein drittes Signal mit viel geringerer Intensität bei 1,7–1,8 ppm weist auf ein Reaktionsprodukt einer Polyboratkomponente mit Protein hin. Nach Erhitzen steigt die relative Intensität der beiden letzteren Signale an, d.h. sowohl der Anteil der geladenen Strukturen in der Lösung als auch der Borionen, die mit Protein reagiert haben, ist gestiegen. Dies ist auf die höhere Löslichkeit bei höherer Temperatur zurückzuführen. Diese Ergebnisse werden in Beziehung gesetzt zu der Effektivität der Albuminborate bei unterschiedlichen pH-Werten sowie zum unterschiedlichen Ausmaß der Auslaugung von Borionen im Labor- und Feldversuchen. Ergebnisse beider Versuche werden mitgeteilt. Weiterhin werden Beziehungen hergestellt zu früheren Befunden zur Effektivität von Proteinen mit unterschiedlichen isoelektrischen Punkten als Holzschutzmittel, sowie zum Einfluß des pH-Wertes auf die Leistungsfähigkeit dieser Holzschutzmittel.

     

Stabilization of emulsions and foams using barley β-glucan

Barley β-glucan (BBG) is receiving increasing attention as a food hydrocolloid. Stability of foams and emulsions was assessed using whey protein concentrate (WPC) as an emulsifier and foaming agent, and BBG gum extracted at pilot plant or laboratory scale as a stabilizer. WPC had a significant lowering effect (P⩽0.05) on surface tension of water and water–oil interfacial tension, while the effect of β-glucan was time dependent. Differential scanning calorimetry (DSC) showed that BBG formed a gelled network, responsible for stabilizing, that melts at 58–62°C. Reversible gels of BBG melt around 63°C. Emulsion (50% o/w) droplet size decreased several fold when prepared with BBG gum and phase separation was substantially decreased. Foam volume and 50% drainage were significantly (P⩽0.05) improved upon addition of β-glucan. Sugar significantly enhanced foam stability only when used together with β-glucan. BBG shows potential as a stabilizer in foam- and emulsion-type food products.     

Effect of chitosan molecular weight on the stability and rheological properties of β-carotene emulsions stabilized by soybean soluble polysaccharides

In this study, β-carotene emulsions were prepared using a two-stage homogenization process and adsorption of chitosan to anionic droplets coated with soybean soluble polysaccharides (SSPS). Effects of the molecular weights of chitosan on the stability and rheological properties of β-carotene emulsions were investigated. Results demonstrated that the ζ-potential, particle size and rheological properties of emulsions were greatly dependent on the chitosan molecular weight. It was found that the particle size of SSPS-stabilized emulsions increased with the rise of chitosan molecular weight at higher chitosan concentrations (>0.2 wt%). Chitosan molecular weight had a significant impact on the heat and light stability of β-carotene in emulsions. SSPS-stabilized emulsion with the adsorption of medium molecular weight-chitosan (MM-chitosan) was more stable than those with the adsorption of low and high molecular weight-chitosan (LM-chitosan and HM-chitosan). Dynamic oscillatory shear tests indicated that the viscoelasticity could be enhanced by the adsorption of higher molecular weight of chitosan onto the SSPS-coated droplet surfaces.     

Enzymatic scouring and bleaching of cotton terry fabrics – opportunity of the improvement on some physicochemical and mechanical properties of the fabrics

In the present study, an attempt was made to treat cotton terry fabrics with alkaline pectinase enzyme and observe the effects on the properties including the degree of whiteness, water absorbency, pill formation, weight loss after abrasion, tenacity at maximum load, degree of polymerization (DP), and hand feeling of the fabric. The enzymatic treatment of cotton terry fabrics had a positive influence on some of their properties. The degree of damage of cotton terry fabrics after 20 washings in a domestic washing machine was determined by analyzing the tenacity at maximum load, weight loss after abrasion, fabric hand feeling, and the DP. Enzymatic-scoured fabrics had a higher resistance to abrasion, a lower decrease in the DP, and a higher rating of the fabric hand feeling compared with alkaline-scoured fabrics. Enzymatic processing was accompanied by a significant lower demand of energy and water. Consequently, at these processes arises the lowest amount of effluents and the produced wastewater is biodegradable. This study attempted to introduce enzymatic scouring (ES) and bleaching with peracetic acid (PAA) of the cotton terry fabrics.     

Correlation between acoustic and physical–mechanical properties of insulating composite boards made from sunflower stalk and wood chips

Physical and mechanical properties of low-density insulating particleboards (0.45 g/cm³) made from wood chips and waste sunflower stalk (SFS) were studied, and correlations with the acoustic properties were determined. Two types of layered boards were manufactured, one with SFS in the central section, and the other with SFS on the surface layers; the layered boards were then compared with two kinds of homogeneous boards made from 100 % SFS and wood chips. Two types of resin were used, urea–formaldehyde (UF) and isocyanate; the press time was 5 and 7 min. Results showed that higher compression ratio in boards containing sunflower stalk resulted in significant improvement of physical–mechanical properties. Interaction between different layers of wood chips and sunflower stalk caused no clear trend in the acoustic properties of the layered boards with none of the resins; however, significant difference was found in the homogeneous boards produced with UF and isocyanate resins. High significant correlations were found between modulus of rupture and elasticity and thickness swelling (24 h) versus six acoustic properties. It can therefore be concluded that acoustic properties, as non-destructive tests, can be used to estimate some of the physical–mechanical properties of new insulating particleboards with different density and compositions.     

Stabilization of multilayered emulsions by sodium caseinate and κ-carrageenan

The influence of the κ-carrageenan concentration and pH on the properties of oil-in-water multilayered emulsions was studied. Multilayered emulsions were prepared by the mixture of a primary emulsion stabilized by 0.5% (w/v) sodium caseinate (Na-CN) with κ-carrageenan solutions with different concentrations (0.05–1% w/v). The emulsions were evaluated at pH 7 and 3.5. At pH 7, there was little adsorption of κ-carrageenan onto the droplet surface and a depletion flocculation was observed when the polysaccharide concentration exceeded 0.5% (w/v). At pH 3.5, a mixed κ-carrageenan–Na-CN second layer was formed around the protein-covered droplets and the emulsions showed bridging flocculation at lower polysaccharide concentrations (0.05–0.25% w/v). Stable emulsions could be formed with the highest κ-carrageenan concentration (1% w/v) at both pH values (7.0 and 3.5). Thus, stable emulsions were successfully produced using protein–polysaccharide interfacial complexes, and the oil droplet diameter, zeta potential and rheological properties of these emulsions were not affected by changes in the pH.     

Effect of industrial wood particle size on mechanical properties of?wood-polyvinyl chloride composites

Wood-polyvinyl chloride (PVC) composites were prepared using industrial wood particles used for manufacturing three-layer particleboards. The effect of particle size (0.25–0.5, 0.5–1, 1–2, and 2–4?mm) on the mechanical properties of the composites was investigated. The effect of cross-section size (4×10, 6×15 and 8×20?mm²) of composite pieces made by an injection moulding method was also studied. Both the particle size and specimen cross-section area significantly influenced these properties. The tensile and flexural properties as well as the impact strength in general increased with increasing particle size, and decreased with increasing cross-section size.