A Study on the Synthesis, Curing Behavior and Flame Retardance of a Novel Flame Retardant Curing Agent for Epoxy Resin

In this work, a flame retardant curing agent (DOPO-MAC) composed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO and methyl acrylamide (MAC) was synthesized successfully, and the structure of the compound was characterized by FT-IR and 1H-NMR. The non-isothermal kinetics of the epoxy resin/DOPO-MAC system with 1% phosphorus was studied by non-isothermal DSC method. The activation energy of the reaction (Ea), about 46 kJ/mol, was calculated by Kissinger and Ozawa method, indicating that the curing reaction was easy to carry out. The flame retardancy of the epoxy resin system was analyzed by vertical combustion test (UL94) and limiting oxygen index (LOI) test. The results showed that epoxy resin (EP) with 1% phosphorus successfully passed a UL-94 V-0 rating, and the LOI value increased along with the increasing of phosphorus content. It confirmed that DOPO-MAC possessed excellent flame retardance and higher curing reactivity. Moreover, the thermal stability of EP materials was also investigated by TGA. With the DOPO-MAC added, the residual mass of EP materials increased remarkably although the initial decomposition temperature decreased slightly.

Research on Rheology and Micro-properties of Modified Room Temperature Biological Asphalt

In order to explore the rheological property and principles of modified room temperature biological asphalt made with petroleum asphalt, vegetable asphalt, and unsaturated fatty acids as raw materials, waste rubber powder as modifier, and calcium hydroxide powder as curing agent, this paper compared and tested the rheological properties and the original petroleum asphalt by using DSR and BBR, and the micro-properties of the asphalt were studied by using SEM. The PG classification of modified room temperature biological asphalt has been upgraded from PG58-28 of the original petroleum asphalt to PG82-28. Compared with the original petroleum asphalt, the high temperature rheological property of the modified room temperature biological asphalt has been greatly improved. Its low temperature rheological property is equivalent to the original one, but the possibility of cracking is lower. SEM test showed that the components of the modified room temperature biological asphalt are well combined. The calcium hydroxide curing agent reacts with fatty acid and the rubber particles cross link with each other to form a mesh package in the asphalt, which provides strength for the modified temperature biologic asphalt at room temperature.

Investigation On Stabilization/Solidification Characteristics of Lead Contaminated Soil Using Innovative Composite Model of Cement And Soda Residue

The cement solidification/stabilization method of heavy metal contaminated soils has been promoted in engineering practice and applied on a large scale for site remediation, but it still reveals some scientific problems in the current complex and variable global extreme climate. To solve these problems and explore cement-based soil remediation technology, this study used the waste soda residue produced in large quantities in the "ammonia-soda process" as a composite additive, and established an innovative composite model of cement and soda residue by adding different ratios, which was applied to the remediation experiments of lead-contaminated soil. The innovative composite model solidification/stabilization of cement and soda residue for unconfined compressive strength and toxic leaching properties under different soil environmental conditions were investigated. Moreover, curing and leaching mechanisms are discussed, and future industrial practice was evaluated. The results showed that the addition of soda residue improved the early (20 days) unconfined compressive strength (UCS) of the composite curing agent for lead-contaminated soil by an average of 23.1% Mpa. When the percentage of soda residue composite was 40%, the UCS strength was 0.96 Mpa, which reached the maximum. The concentration of Pb2+ in the leachate of the cement-soda residue composite curing agent was greatly reduced (average 3.28 times) compared with that of a single cement in the same situation, with an average leached Pb2+ concentration of 1.87 mg·L-1. This indicates that the addition of alkali residue improved the curing effect. The curing mechanism was divided into four steps, mainly a complex physicochemical reaction between the cement-soda residue composite and soil particles. The leaching mechanism of cement-soda residue to aqueous solution is mainly the consumption of acid ions by alkaline substances. This study will provide scientific data to support potential lead-containing soil in site remediation technologies and future large-scale engineering applications.