Chemiluminescence measurement of gel times for amine-cured epoxy resins

1995 ◽  
Vol 7 (2) ◽  
pp. 219-236 ◽  
Author(s):  
K A Kozielski ◽  
N C Billingham ◽  
G A George ◽  
D C L Greenfield ◽  
J M Barton
Keyword(s):  
Chemical Reactions ◽  
Epoxy Resins ◽  
Physical State ◽  
Glycidyl Ether ◽  
Cross Linking ◽  
Gel Time ◽  
The Matrix ◽  
Effect Of Impurities ◽  
The Cross

The cross-linking reactions of 4,4'-diaminodiphenyl sulphone (DDS) with stoichiometric quantities of glycidyl ether- or tetraglycidyl amine-based epoxy resins were monitored using chemiluminescence (CL) and rheometry. It was found that, when a sample was cured isothermally in air, the CL profile increased to a maximum, then decreased again. The maximum was found to correspond well with the gel time (tgel), as measured by rheometry. This observation is discussed in relation to the chemical reactions occurring within the material and the physical state of the matrix. The effect of impurities in DDS on the gel time of these epoxy resins is reported.

scholarly journals Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

2021 ◽  
Author(s):  
Istebreq A. Saeedi ◽  
Sunny Chaudhary ◽  
Thomas Andritsch ◽  
Alun S. Vaughan
Keyword(s):  
Glass Transition ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Epoxy Resins ◽  
Functional Network ◽  
Cross Linking ◽  
Network Modifier ◽  
Epoxy Resin System ◽  
The Cross ◽  
The Impact

AbstractReactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

scholarly journals Synthesis of epoxy resins derivatives of naphthalene-2,7-diol and their cross-linked products

2019 ◽  
Vol 138 (6) ◽  
pp. 4349-4358 ◽  
Author(s):  
K. Fila ◽  
M. Gargol ◽  
M. Goliszek ◽  
B. Podkościelna
Keyword(s):  
Fourier Transform ◽  
Epoxy Resins ◽  
Attenuated Total Reflectance ◽  
Cross Linking ◽  
Total Reflectance ◽  
Before And After ◽  
Ft Ir ◽  
The Cross ◽  
Derivatives Of ◽  
Epoxy Groups

Abstract The aim of this study was the synthesis of three different epoxy compounds based on naphthalene-2,7-diol (2,7-NAF.EP, 2,7-NAF.WEP, 2,7-NAF.P.EP) and then their cross-linking by triethylenetetramine (TETA). All epoxides were prepared by the reaction of naphthalene-2,7-diol with epichlorohydrin but under different conditions and with other catalysts. The structures of the obtained compounds before and after the cross-linking reactions were confirmed by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR). The ATR/FT-IR spectra of cross-linked compounds show disappearance of the C–O–C bands (about 915 cm−1) derived from the epoxy groups. DSC and TG/DTG measurements indicated that the obtained materials possess good thermal resistance; they are stable up to about 250 °C. The hardness of the cross-linked products was determined using the Shore D method. The highest value of hardness was obtained for the 2,7-NAF.EP-POL. Additionally, the UV–Vis absorption spectra of the obtained polymers were registered and evaluated.

Creep and dynamic mechanical behavior of cross-linked polyvinyl alcohol reinforced with cotton fiber laminate composites

2019 ◽  
Vol 39 (4) ◽  
pp. 326-335 ◽  
Author(s):  
Naman Jain ◽  
Shubhan Ali ◽  
Vinay K. Singh ◽  
Komal Singh ◽  
Nitesh Bisht ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Cotton Fiber ◽  
Water Solubility ◽  
Mechanical Analysis ◽  
Cross Linking ◽  
Laminate Composites ◽  
Dynamic Mechanical ◽  
The Matrix ◽  
The Cross ◽  
Uptake Test

AbstractThe objective of this investigation was to fabricate cross-linked polyvinyl alcohol (PVA) based laminate composites reinforced with biaxial cotton sheets. Cross-linking was done with sulfuric acid, to overcome the water solubility of PVA. A water uptake test was performed to evaluate the effect of cross-linking on the water absorption properties of the composites. Morphology, distribution and bonding between the matrix and reinforcement of the fabricated composites were studied using scanning electron microscopy. Mechanical properties such as the tensile strength (TS), modulus of elasticity and elongation of the fabricated composites material were evaluated. There was about a 56.25% increase in the TS of the cross-linked composite as compared to the neat PVA, and at 64 wt.% of cotton fiber, there was about a 56% increase in the TS as compared to the cross-linked PVA. The thermal degradation analysis of fabricated composites material was carried out by thermogravimetric analysis. The thermal stability increased with increase in cotton fiber wt.%. The viscoelastic properties of the fabricated composites material were determined by dynamic mechanical analysis. The effects of stress (4 MPa, 6 MPa and 8 MPa) and temperature (20°C and 40°C) on creep and recovery behavior of the laminated composites were studied.

scholarly journals Optimization of the Curing and Post-Curing Conditions for the Manufacturing of Partially Bio-Based Epoxy Resins with Improved Toughness

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1354 ◽  
Author(s):  
Diego Lascano ◽  
Luis Quiles-Carrillo ◽  
Sergio Torres-Giner ◽  
Teodomiro Boronat ◽  
Nestor Montanes
Keyword(s):  
Epoxy Resin ◽  
Epoxy Resins ◽  
Polymer Network ◽  
Thermomechanical Properties ◽  
Diglycidyl Ether ◽  
Polymer Chains ◽  
Cross Linking ◽  
Reactive Diluent ◽  
Gel Time ◽  
Curing Conditions

This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ° C and 90 ° C , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ° C   or 150 ° C yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ° C and post-cured at 150 ° C for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure.

scholarly journals A novel fibre-ensemble level constitutive model for exogenous cross-linked collagenous tissues

2016 ◽  
Vol 6 (1) ◽  
pp. 20150090 ◽  
Author(s):  
Michael S. Sacks ◽  
Will Zhang ◽  
Silvia Wognum
Keyword(s):  
Constitutive Model ◽  
Soft Tissues ◽  
Fibrous Tissue ◽  
Collagen Fibre ◽  
Tissue Response ◽  
Loading Path ◽  
Cross Linking ◽  
The Matrix ◽  
The Cross ◽  
Collagenous Tissues

Exogenous cross-linking of soft collagenous tissues is a common method for biomaterial development and medical therapies. To enable improved applications through computational methods, physically realistic constitutive models are required. Yet, despite decades of research, development and clinical use, no such model exists. In this study, we develop the first rigorous full structural model (i.e. explicitly incorporating various features of the collagen fibre architecture) for exogenously cross-linked soft tissues. This was made possible, in-part, with the use of native to cross-linked matched experimental datasets and an extension to the collagenous structural constitutive model so that the uncross-linked collagen fibre responses could be mapped to the cross-linked configuration. This allowed us to separate the effects of cross-linking from kinematic changes induced in the cross-linking process, which in turn allowed the non-fibrous tissue matrix component and the interaction effects to be identified. It was determined that the matrix could be modelled as an isotropic material using a modified Yeoh model. The most novel findings of this study were that: (i) the effective collagen fibre modulus was unaffected by cross-linking and (ii) fibre-ensemble interactions played a large role in stress development, often dominating the total tissue response (depending on the stress component and loading path considered). An important utility of the present model is its ability to separate the effects of exogenous cross-linking on the fibres from changes due to the matrix. Applications of this approach include the utilization in the design of novel chemical treatments to produce specific mechanical responses and the study of fatigue damage in bioprosthetic heart valve biomaterials.

scholarly journals Plugging mechanisms of polymer gel used for hydraulic fracture water shutoff

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 411-422
Author(s):  
Song Zhang ◽  
Falin Wei ◽  
Pingde Liu ◽  
Liming Shao ◽  
Weitao Li
Keyword(s):  
Hydraulic Fracture ◽  
Physical Simulation ◽  
Distribution Patterns ◽  
Cross Linking ◽  
Polymer Gel ◽  
Gel Layer ◽  
The Matrix ◽  
The Cross ◽  
The Difference ◽  
Flow Leak

AbstractThe performance of polymer gel to plug a hydraulic fracture is greatly affected by its distribution patterns and gelling effect. In this study, the migration of a gel plugging agent in a fracture and its plugging after gelling were investigated by physical simulation experiments. In addition, the distribution patterns of the gel plugging agent and its plugging mechanism after gelling were investigated in detail. The results of this study revealed that the migration flowing behavior of the gel solution in a fracture can be divided into three streams: fracture flow, leak off flow, and matrix flow. Such behavior distributed the gel in three different patterns after gelling: gel clusters in the fracture, gel layer on the fracture surface, and dispersed gel lumps in the matrix pores-throats. Because of the leak off flow and the difference in components, the gel solution has apparent disproportional leak off–diffusion of components during its migration in a fracture, with less polymer molecules and loss of more cross-linking agent ions. The leak off of the cross-linking agent significantly deteriorates the gelling strength of the polymer gel, affecting its performance to plug a hydraulic fracture. The results also show that when the normalized concentration of the cross-linking agent ions in a fracture is less than 0.6, gel fails to plug the fracture effectively after gelling. When gelling was carried out by in situ cross-linking, polymer gel provided more satisfactory plugging performance than the gelling via ground pre-cross-linking.

scholarly journals The Use of the ATD Technique to Measure the Gelation Time of Epoxy Resins

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6022
Author(s):  
Jakub Smoleń ◽  
Piotr Olesik ◽  
Paweł Gradoń ◽  
Mateusz Chudy ◽  
Bogusław Mendala ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Epoxy Resins ◽  
Gelation Time ◽  
Graphite Powder ◽  
Cross Linking ◽  
Gel Point ◽  
Curing Process ◽  
Carbon Particles ◽  
The Cross ◽  
The Stability

In this paper, we investigated the thermodynamics of the resin curing process, when it was a part of composition with graphite powder and cut carbon fibers, to precisely determine the time and temperature of gelation. The material for the research is a set of commercial epoxy resins with a gelation time not exceeding 100 min. The curing process was characterized for the neat resins and for resins with 10% by weight of flake graphite and cut carbon fibers. The results recorded in the analysis of temperature derivative (ATD) method unequivocally showed that the largest first derivative registered during the test is the gel point of the resin. The innovative approach to measuring the gelation time of resins facilitates the measurements while ensuring the stability of the curing process compared to the normative tests that introduce mechanical interaction. In addition, it was found during the research that the introduction of 10% by weight of carbon particles in the form of graphite and cut carbon fibers rather shortens the gelation time and lowers the temperature peak due to the effective absorption and storage of heat from the cross-linking system. The inhibiting (or accelerating) action of fillers is probably dependent on chemical activity of the cross-linking system.

The cross-linking and degradation of paraffin chains by high-energy radiation

1954 ◽  
Vol 222 (1148) ◽  
pp. 60-74 ◽  
Keyword(s):  
Melting Point ◽  
Physical State ◽  
Main Chain ◽  
High Energy ◽  
Cross Linking ◽  
Cross Link ◽  
High Energy Radiation ◽  
The Cross ◽  
Solid Liquid ◽  
Α Particles

n -Paraffins from C 7 H 16 to C 36 H 74 and polyethylene polymers (Polythene and Winnothene) have been subjected to atomic pile radiation. For the paraffins there is a decrease in the melting-point, until, for a radiation dose R , they no longer melt at temperatures of 160° C or above. At about this same radiation the paraffin is turned into an insoluble gel. The product Rn ρ, where n is the number of carbons per atom, and ρ the density, is approximately constant from heptane (n = 7) to Polythene (n ~ 2000), although an anomaly may occur for Winnothene (n ~ 250). This indicates that the energy required to form a cross-link is approximately independent of chain length. An analysis of published experiments on methane and butane extends this conclusion down to n = 1. The results obtained by earlier workers when paraffinic gases are bombarded with deuterons and α-particles are explained in terms of the cross-linking phenomenon. Solubility measurements give similar values for Rn ρ in the case of Polythene and Winnothene, and show that for every cross-link formed, on the average about 0·35 C—C bonds in the main chain are fractured. Similar values are obtained for methane and butane. The energy absorbed per C—H bond fracture is about 12 eV, and the energy per cross-link is 24 eV. This corresponds to 0·5 % of carbons becoming cross-linked per unit radiation, independent of the physical state (solid, liquid or gaseous) of the irradiated paraffin. The importance of these results, as far as polymerization theory is concerned, is briefly discussed.

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