Mechanical Properties of New Composite Wood-Plastic Formworks with Aluminum Alloy Frame

Formwork engineering plays a crucial role in cost, efficiency, quality, and schedule in civil engineering. Currently, wood-plastic formwork, which has favorable mechanical properties such as wood and excellent stability, formability, ease of demolding, and time-saving as plastic, is earning its increasing reputation in construction. This work focuses on mechanical properties of two types of new composite wood-plastic formworks with aluminum alloy frame used for construction, that is, single-span simply supported and three-span continuous formworks. Experimental investigation shows that the two types of wood-plastic formworks demonstrate favorable performance, and the deflections and stresses are within the allowable range, thereby satisfying the structural bearing requirements. Numerical analyses confirm that the results of the refined and general finite element models are consistent with the experimental results, but the former has a higher accuracy. When the requirement of accuracy is not too strict, the general model is preferred, given the modeling convenience and high efficiency. On the basis of experimental and numerical investigations, practical simplified formulas are proposed to facilitate rapid calculation and evaluation considering transverse deflection and inconsistency of two materials. Therefore, the results in this work can provide a theoretical basis for developing and applying the new formworks.

Impact of melamine and its derivatives on the properties of poly(vinyl acetate)-based composite wood adhesive

A fire retardant composite adhesive for bonding wood and wood-based elements has been developed and characterized. To obtain the enhanced fire-proof properties of the wood adhesive dispersion based on the poly(vinyl acetate) (PVAc), ceramic fillers (17.5 wt% total)—alumina, silica, kaolin and glass fibers were applied. Moreover, fire retardants such as melamine, melamine phosphate and melamine polyphosphate (up to 7 wt%) were also used. Thermal analysis (TG-DSC), strength tests, rheology, pH and flammability measurements (PCFC) were performed. The best properties of the adhesive were achieved for ceramic additives supported by melamine phosphate. A slight improvement of shear strength, shift of the last decomposition step of PVAc (residue degradation) towards higher temperatures by about 50 °C, reduction in mass loss from 100 wt% to less than 70 wt% and about 30–40% improvement of flammability parameters such as heat release capacity, total heat release or peak heat release rate were found compared to the pure poly(vinyl acetate) adhesive.

Micro-Fibrillated Cellulose in Adhesive Systems for the Production of Wood-Based Panels

Micro-Fibrillated Cellulose (MFC) is a new type of bio-based additive, coming from wood cellulose. It can compete and substitute oil derived chemicals in several application fields. In the present work, the use of micro-fibrillated cellulose, in waterborne adhesive systems applied in the manufacture of composite wood-based panels was evaluated. Research was conducted to test the potential of improving the performance of wood-based panel types such as particleboard, waferboard or randomly-oriented strand board and plywood, by the application of MFC and the substitution of conventional and non-renewable chemical compounds. The approaches followed to introduce MFC into the adhesive systems were three, i.e., MFC 2% suspension added during the adhesive resin synthesis, MFC 10% paste admixed with the already prepared adhesive resin and MFC 2% suspension admixed with the already prepared resin. It was found that MFC improves not only the performance of the final wood panel products but also the behaviour of the applied adhesive polymer colloids (e.g., rheology improvement), especially when admixed with the already prepared resins. Moreover, it was proven that when MFC is introduced into the adhesive resin system, there is a possibility of decreasing the resin consumption, by maintaining the board performance. MFC’s robustness to pH, shear and temperature makes it a highly interesting new additive for adhesive producers. In addition, its natural origin can give adhesive producers the opportunity to move over to more environmentally friendly product solutions.

Ways to solve the problem of reducing the toxicity of composite wood materials based on urea-, phenol-formaldehyde oligomers

Composite wood materials in the form of chipboards based on urea-formaldehyde resins (grades KF-MT-15, KF-NFP, etc.) are widely used in furniture production. However, one of the main shortcomings of chipboards is their toxicity associated with the release of a gas harmful to humans – formaldehyde. Its maximum permissible concentration in the air of a residential building should not exceed 0,01 mg per m3 of air. The paper shows one of the solutions to the problem of reducing the toxicity of chipboards

Engineering the Properties of Eco-Friendly Medium Density Fibreboards Bonded with Lignosulfonate Adhesive

Free formaldehyde emissions from wood-based panels, especially in indoor applications, pose serious risks to human health at certain concentrations. Prolonged exposure to formaldehyde can cause adverse health effects including eye, nose and throat irritation, other respiratory symptoms and cancer. As a consequence, new formaldehyde emission limits for composite wood products were established in Europe, USA and Japan. This, together with the stricter environmental legislation are the main driving factors for shifting the scientific and industrial interest from the traditional formaldehyde-based synthetic resins to the new bio-based adhesives for production of eco-friendly wood-based panels. The lignin-based products are one of the most prospective ecological alternatives to the traditional formaldehyde resins. The main interest in lignin is due to its phenolic structure with several favourable properties for the formulation of wood adhesives such as high hydrophobicity and low polydispersity. The present article is aimed at studying the possibilities for using lignosulfonate as an adhesive for the production of eco-friendly MDF. Regression models describing the impact of lignosulfonate concentration and hot pressing temperature on the exploitation properties of MDF panels were developed. The individual and combined impact of both factors was analysed in order to determine the optimal exploitation properties of the panels.

Accelerated Thermal Aging of Bio-Based Composite Wood Panels

Bio-based adhesives and resins are sought as alternatives to synthetics in order to fabricate all-biobased composite wood panels (CWPs), which provide environmentally friendly building products for indoor use. Very little information exists as to how these bio-based CWPs would perform long-term in non-temperature controlled structures such as warehouses and storage units where extreme temperatures occur depending on the season. In this study, novel all-bio-based CWPs were fabricated using a matrix of 50% distiller’s dried grains with solubles (DDGS) and 50% soybean flour ProsanteTM (PRO) mixed with wood particles. Bio-based CWPs were subjected to accelerated thermal aging for a 10-year period resembling outdoor temperatures in Peoria, IL USA. Four seasonal periods (Winter, Spring, Summer, and Fall) were simulated varying from −26–40 °C and 36–76% relative humidity (RH). The bio-based adhesive employed consisted of 50% distiller’s dried grains with solubles (DDGS) and 50% soybean flour ProsanteTM (PRO). CWPs consisted of 15 or 50% DDGS/PRO with 85% or 50% pine wood. CWPs were evaluated for 5, 7.5, and 10-years for their physical, flexural, dimensional stability, surface roughness, FTIR, TGA, and spectral properties. The changes in the CWP properties were notable during the initial 5 years, and later aged samples showed less change.

Working capability of composite wood-rubcon (rubber concrete) reinforced bridge beams under static loads

The results of experimental studies of the performance of bent composite wood-rubcon reinforced bridge beams under static loads are presented and the bearing capacity of composite wood-rubcon reinforced bridge beams is determined. A method for calculating wood-rubcon reinforced composite bridge beams is proposed.