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Special Features of Construction Operations Related to Substructure Works to be Carried Out Under Reconstruction
Published in P.A. Konovalov, Bases and Foundations of Buildings under Reconstruction, 2020
In those situations wherein the length of the damaged waterproofing layer does not exceed 1.0–1.5 m, restoration works may be carried out simultaneously throughout the entire section. Here the order of work should be as follows: Two holes 0.8–1.0 m wide and 0.4 m deep are cut below the waterproofing layer from both sides of the wall, extending the entire length of the section (Fig. 78). Next, two-three layers of brick masonry are removed to make a horizontal slot. A levelling coat of colloid cement mortar (1:1 or 1:1.5) is then laid on the bottom layer of the brick masonry. A cementation resin is applied thereafter or silicification done. Urea formaldehyde is often used as the resin and a 10% solution of oxalic acid used as the hardener. Compared to other substances, urea formaldehyde resin has higher insulation properties.
Insulation materials
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Urea formaldehyde foam (UF) was used extensively in the 1980s for cavity wall insulation, but it can shrink after installation, creating fissures that link the outer and inner leaves. Occasionally, in conditions of high exposure, this led to rainwater penetration. After installation, the urea formaldehyde foam emits formaldehyde fumes, which have in certain cases entered buildings, causing occupants to suffer from eye and nose irritation. The problem normally arises only if the inner leaf is permeable and a cavity greater than 100 mm is being filled. Recent advances claim to have reduced formaldehyde emissions, but all installations must be undertaken to the stringent standard BS 5618: 1985. The Health and Safety Executive advises against the use of urea formaldehyde where the inner leaf of the cavity wall is porous or has unsealed connections with the interior. (The thermal conductivity of urea formaldehyde foam is typically 0.038 W/mK.)
Radioactive Waste Management
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Urea-formaldehyde resins are materials used to immobilize liquid and particulate solid wastes. The resin is a cross-linking polymerization product of the reactants urea and formaldehyde, and consists of a mixture of monomethylol urea and dimethylol urea, depending on the ratio of reactants. The reaction between the constituents is initiated by using a weak acid (sodium bisulfate or phosphoric acid) at a pH between 1.0 and 2.0. The cross-linked structure of the resin traps the aqueous waste within the solid resin matrix.
Investigation of poly (styrene-4-vinylbenzyl chloride) as a curing agent for alternative plant proteins
Published in The Journal of Adhesion, 2023
Elena Averina, Johannes Konnerth, Hendrikus W.G. van Herwijnen, Kaichang Li
Due to their environmental friendliness and sustainability, renewable plant proteins are appealing raw materials for a wide range of industrial applications[1]. For example, plant protein-based wood adhesives are potential substitutes for petrochemical-based adhesives such as phenol- and urea-formaldehyde resins in the commercial production of wood-based composite panels such as particleboard and plywood. The raw materials of petrochemical-based adhesives come from finite and non-renewable resources. The production and use of wood-based composite panels bonded with urea-formaldehyde resins release carcinogenic formaldehyde.[2,3] There is a need for the development of formaldehyde-free wood adhesive from renewable materials.
Soy-based, tannin-modified plywood adhesives
Published in The Journal of Adhesion, 2018
Saman Ghahri, Antonio Pizzi, Behbood Mohebby, Ahmad Mirshokraie, Hamid Reza Mansouri
The main impetus for today’s renewed interest in bio-based adhesives is the acute sensitivity of the general public to anything that has to do with the environment and its protection [1]. Synthetic adhesives are widely used to bond wood-based panels. The typical adhesives for this application are oil based. Many of these constitute a high risk due to their environmental and human impacts. Some even use compounds now classed as carcinogenic. For example, urea formaldehyde resins which are widely used as adhesive cause emission of carcinogenic formaldehyde gas. Nowadays, industry has become more willing to use natural-based and environmental-friendly wood adhesives.
Evaluating indoor air quality and energy impacts of ventilation in a net-zero energy house using a coupled model
Published in Science and Technology for the Built Environment, 2018
Lisa Ng, Dustin Poppendieck, W. Stuart Dols, Steven J. Emmerich
Despite source control measures to minimize the use of building products with urea-formaldehyde resin, none of the simulated ventilation rates reduced formaldehyde concentrations below levels associated with a cancer risk of 1 in 1,000,000 (0.08 µg m−3). This is due to many factors, but the primary reason is that, like most locations in the United States (EPA 2017), the average outside concentration of formaldehyde measured at the NZERTF was above this concentration. As will be discussed later, studies of other new homes also found formaldehyde above the level associated with a cancer risk of 1 in 1,000,000.