Synthesis and Deblocking Investigations of Phenol Blocked Aliphatic Isocyanates and Their Application in the Development of Epoxy-Polyurethane Films

Phenol blocked hexamethylenediisocyanate adducts and polyisocyanates were synthesized and their structure was validated by FTIR, 1H & 13C NMR spectroscopy, TGA, DSC and CO2 evolution techniques were used to evaluate the deblocking temperature of blocked isocyanates. Gel time studies of blocked isocyanates with terathane polyol and solubility study of blocked isocyanates with different polyols were conducted to demonstrate the structure-property correlation. Epoxy-polyurethane films were produced utilizing the blocked isocyanates reported in this work with epoxy resin and their structure was verified by ATR Spectroscopy. TGA, DSC, shore A hardness, tensile strength and flexural strength analysis were used to investigate the thermal and mechanical characteristics of these films. The findings of deblocking temperature and gel time revealed that unsubstituted phenol blocked isocyanates and polyisocyanates deblock at lower temperatures and cure for a shorter time period than substituted phenol blocked isocyanates. Thermal and mechanical characteristics of epoxy-polyurethane films based on blocked polyisocyanates are satisfactory.

THE SOY FLOUR AS AN EXTENDER FOR UF AND MUF ADHESIVES IN BIRCH PLYWOOD PRODUCTION

Formaldehyde emission still remains a major disadvantage of widely applied formaldehyde-containing amino resins such as UF (urea-formaldehyde) resin and MUF (melamine-urea-formaldehyde) resin. The compositions of adhesives for plywood manufacturing have to contain a proper extenders in order to adjust their viscosity. Thus, the aim of the study was to investigate the effect of protein-rich soy flour (SF) as the extender for adhesives. The composition of flours and their ability to absorb the formaldehyde were determined. Properties of liquid resins such as gel time, viscosity, pH and solid content were investigated. The possible chemical interaction between the extenders and resins were assessed with the use of FTIR spectroscopy. Plywood panels manufactured using UF and MUF adhesives with the soy flour introduced as the extender in various concentrations were tested in terms of shear strength and formaldehyde release. Studies have shown that soy flour has a favorable composition and formaldehyde-scavenging ability. The addition of SF affected resins properties such as viscosity and gel time but showed no influence on their pH and solid content. FTIR analysis has not explained the chemical interaction between resin and extender. The application of soy flour in the concentration of 15% for UF resin and 10% for MUF resin allowed to produce plywood characterized by improved bonding quality and decreased formaldehyde emission.

Evaluation of chestnut shell and coffee waste with phenol-formaldehyde resin for plywood filler

A casca da castanha e resíduos de café moído foram avaliados como material de enchimento para produção de adesivo para compensados. Uma resina de fenol-formaldeído (FF) foi formulada em laboratório para fabricação de compensados. As propriedades da resina FF foram sólidos não voláteis, tempo de gelatinização (gel time),viscosidade, etc. A resina FF sintetizada em laboratório foi misturada com extensor, carga e NaOH. Os compensados foram feitos de maneira uniforme com a mistura de resina FF e testados quanto à resistência ao cisalhamento, módulo de ruptura (MOR) e inchamento em espessura, de acordo com as normas coreanas KS F 3101 e KS F 3114. Todos os compensados fabricados com cada tipo de carga apresentaram boas propriedades de resistência física e mecânica. Os resultados dos testes de desempenho indicaram que a casca da castanha e os resíduos de café moído são adequados como carga para produção de adesivo para fabricação de compensados.

Vacuum Infusion Simulation for Radome Manufacturing Using Woven Flax Fibre and Glass Fibre

The vacuum infusion method is emerging to produce composite parts, especially thin wall structure aircraft radome. Ansys Fluent is used in the optimization phase for mould filling analysis on aircraft radome part. The permeability fibre is referring to the physical property of the fibre reinforcement to allow fluids to permeate it, thus it is correlated with the viscosity of the resin used. In this work, flax fibre, glass fibre and low viscosity epoxy resin are used to determine the permeability value of flax fibre, glass fibre and hybrid without using a flow medium. In-plane experiment on reinforcement fibre permeability is conducted and all reinforcement fibre have similar fibre architecture and weight. The development of a digital model from a top partial aircraft radome is obtained through a 3D scanner and CATIA. Ansys Fluent is used to optimize the location of the injection line and air vent for the epoxy. The Ansys Fluent analysis model is validated through the in-plane experiment filling time result for a flat model. Based on the simulation analysis, the location of the injection line is placed at the perimeter and the air vent at the centre. The filling time from the simulation for the flax fibre and hybrid fibre was estimated around 10 to 11 minutes. However, the filling time for glass fibre is approximate 2 hours which is longer than epoxy gel time. Furthermore, this method can be used in mould filing scenarios of thin wall structure within gel time of the resin.

A Comparison among Lignin Modification Methods on the Properties of Lignin–Phenol–Formaldehyde Resin as Wood Adhesive

The research aim of this work is to determine the influence of lignin modification methods on lignin–phenol–formaldehyde (LPF) adhesive properties. Thus, glyoxal (G), phenol (P), ionic liquid (IL), and maleic anhydride (MA) were used to modify lignin. The modified lignins were used for phenol substitution (50 wt%) in phenol–formaldehyde adhesives. The prepared resins were then used for the preparation of wood particleboard. These LPF resins were characterized physicochemically, namely by using standard methods to determine gel time, solids content, density, and viscosity, thus the physicochemical properties of the LPF resins synthesized. The panels dimensional stability, formaldehyde emission, bending modulus, bending strength, and internal bond (IB) strength were also measured. MA-modified lignin showed by differential scanning calorimetry (DSC) the lowest temperature of curing than the resins with non-modified lignin and modified with IL, phenolared lignin, and glyoxal. LPF resins with lignin treated with maleic anhydride presented a shorter gel time, higher viscosity, and solids content than the resins with other lignin modifications. Equally, the particleboard panels prepared with LPF resins with maleic anhydride or with ionic liquid had the lowest formaldehyde emission and the highest mechanical strength among all the synthesized resins. The dimensional stability of all panels bonded with modified lignin LPF resins presented no difference of any significance.

Consistency Under Applied Pressure Test CAPT - A Novel Method for Evaluating Pressure Effect on the Gel Time of Thermosetting Resin

Thermosetting resin is gaining more acceptances in Plug and Abandonment due to its excellent mechanical properties after set and ability for placement in locations cement cannot reach. A thorough understanding of its curing behavior such as gel time is essential to ensure safe placement and a good seal. This paper investigates the pressure-sensitive gelation behavior of polymer resin under in-situ conditions, and the pressure effect on the gel time of thermosetting resin was evaluated. An innovative assessment methodology named CAPT (Consistency under Applied Pressure Test) was created to assess the curing process of thermoset resins in a pressurized consistometer. A series of resin samples were tested at temperatures ranging from ambient to 120°C with applied pressures up to 10,000 psi. The consistency was initially used to indicate the gel structure development of the resin while it was gelling. Based on the consistency data, the relationship between applied pressure and gel time of resins was studied and a new approach of modeling the curing process with the influence factor of pressure was proposed. The primary observation was the confirmation that the gelation process of thermosetting resin under applied pressure was faster than that under atmospheric pressure. However, the gel time had big variations. The pressure sensitivity mainly depended on the initiators and it was only partly dependent on the temperature. There was a threshold value for the pressure effect on the gel time. Below the threshold, the gel time only decreased by around 5%. Above the threshold, the pressure effect was much larger where the gel time decreased by 20% - 30%. This could be mainly attributed to the thermodynamic effect caused by pressure accelerating the polymerization process, resulting in a shorter gel time. Meanwhile, these results help explain why the curing behavior of thermosetting resin placed underground where high pressure is encountered often differs from the laboratory-predicted performance. Besides indicating the relative strength development, consistency analysis could also be used to assess the pressure effect on the gelation process of a resin sample in down-hole operations with applied pressures. Thus, CAPT would be more suitable than a conventional reactivity test to propose a new approach of modeling the gel time of thermosetting resin systems with the influence factor of pressure. CAPT is a novel method to accurately evaluate the curing process of thermosetting resin and indicate its relative strength development. This helps engineers reach a good balance between designing proper operations and preserving mechanical properties in the plug and abandonment process.

Engineering Gelation Kinetics in Living Silk Hydrogels by Differential Dynamic Microscopy Microrheology and Machine Learning

Microbes embedded in hydrogels comprise one form of living material. Discovering formulations that balance potentially competing mechanical and biological properties in living hydrogels, for example gel time of the hydrogel formulation and viability of the embedded organisms, can be challenging. In this work, a pipeline is developed to automate characterization of the gel time of hydrogel formulations. Using this pipeline, living materials comprised of enzymatically crosslinked silk and embedded E. coli, formulated from within a 4D parameter space, are engineered to gel within a pre-selected timeframe. Gelation time is estimated using a novel adaptation of microrheology analysis using differential dynamic microscopy (DDM). In order to expedite the discovery of gelation regime boundaries, Bayesian machine learning models are deployed with optimal decision-making under uncertainty. The rate of learning is observed to vary between AI-assisted planning and human planning, with the fastest rate occurring during AI-assisted planning following a round of human planning. For a subset of formulations gelling within a targeted timeframe of 5-15 minutes, fluorophore production within the embedded cells is substantially similar across treatments, evidencing that gel time can be tuned independent of other material properties, at least over a finite range, while maintaining biological activity.

Adesivos de lignina Kraft de Eucalyptus spp.

: O aumento na produção de celulose na última década acarretou aumento da geração de licor negro, cujo principal componente é a lignina Kraft. A estrutura da lignina Kraft de eucalipto, tipo siringil, é a menos reativa ao formaldeído, devido à presença de grupos metil ligados aos carbonos 3 e 5 das unidades de fenilpropano. Apesar disto, ainda é considerada o substituto mais promissor para os compostos fenólicos não renováveis. Objetivou-se sintetizar adesivos lignina-fenol-formaldeído, caracterizar suas propriedades e avaliar a resistência ao cisalhamento na linha de cola. Para isso, utilizou-se lignina Kraft de eucalipto para sintetizar 4 adesivos (T2, T3, T4 e T5) com substituição de 25, 50, 75 e 100 % do fenol, respectivamente. Ademais, foi sintetizado adesivo testemunha, sem substituição do fenol. Foram observadas variações significativas de gel time entre todos os tratamentos, com maior valor em T1; os valores de pH diminuiram à medida que a lignina Kraft foi adicionada aos adesivos, com o maior valor obtido para T1; os valores de teor de sólidos também foram estatisticamente diferentes entre si; na viscosidade todos os tratamentos foram estatisticamente diferentes entre-se, com aumento no valor desta propriedade conforme incrementou-se a quantidade de lignina; No teste de cisalhamento, nas condições seca e úmida, T5 e T4 apresentaram os maiores valores de resistência. Concluiu-se que os adesivos T4 e T5 possuem maior potencial para aplicação industrial.

Study of Experimental Investigations in the Presence of Ceramic Waste Powder

The paper aims to evaluate the gel time and exotherm temperature properties of the curing of unsaturated polyester resin at various amounts of Methyl ethyl ketone peroxide, cobalt octoate and porcelain powder. The gel time of samples are determined using the simple method, while the exotherm temperature are evaluated using the thermocouple. The variation of these properties is discussed theoretically and experimentally.