Synthesis of Self-Healing Microcapsules via Different Heating Profiles

2010 ◽  
Vol 148-149 ◽  
pp. 1486-1490
Author(s):  
Ting Ting Li ◽  
Rui Wang ◽  
Xing Liu
Keyword(s):  
Shell Thickness ◽  
Urea Formaldehyde ◽  
Self Healing ◽  
Heating Method ◽  
Temperature Resistance ◽  
Healing Efficiency ◽  
Higher Temperature ◽  
The Mean ◽  
Heating Profiles

Self-healing by microcapsules is one of methods to stop and heal crack propagation in time. Microcapsule containing 5-ethylidene-2-norbornene (ENB) core and Melamine-Urea -Formaldehyde (MUF) shell with possibly higher healing efficiency was synthesized via three different heating histories including different heating rate and heating steps, which significantly affect microcapsule surface morphology, thermal stability, and yield, thus the reproducibility. Finally, it is demonstrated that the best quality of microcapsule was obtained from fast-slower heating method with proper outer surface and shell thickness, as well as 285 higher temperature resistance. The mean particle size is about 100m.

Temperature Profile of Microencapsulation for Self-Healing Application

2010 ◽  
Vol 143-144 ◽  
pp. 353-357
Author(s):  
Ting Ting Li ◽  
Xing Liu ◽  
Rui Wang
Keyword(s):  
Temperature Profile ◽  
Shell Thickness ◽  
Urea Formaldehyde ◽  
Life Time ◽  
Self Healing ◽  
Time Service ◽  
Healing Efficiency ◽  
Performance Surface ◽  
The Relationship

Healing agents significantly affect the efficiency of healing microcracks, which produced from life-time service in composites. And microencapsulating 5-ethylidene-2-norbornene (ENB) with Melamine-Urea-Formaldehyde (MUF) shell possessing higher self-healing efficiency is sensitive to the manufacture temperature profile which is difficult to control but crucial to the microcapsule performance and thus the reproducibility. In this paper, we studied the relationship between heating curve (rate, steps and time) and microcapsule performance (surface morphology, thermal stability and shell thickness). It shows that fast-slower heating stage produces the best quality of microcapsule with proper outer and inner surface which can endure 285°C, and the particle size is about 100m with 400-700nm shell thickness.

scholarly journals Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1918 ◽  
Author(s):  
Hyeong-Jun Jeoung ◽  
Kun Won Kim ◽  
Yong Jun Chang ◽  
Yong Chae Jung ◽  
Hyunchul Ku ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
In Situ Polymerization ◽  
Urea Formaldehyde ◽  
Testing Machine ◽  
Optical Microscope ◽  
The Self ◽  
Self Healing ◽  
Grubbs Catalyst ◽  
Healing Efficiency

The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 μm in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs’ catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs’ catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.

scholarly journals Mechanical Properties Assessment of Low-Content Capsule-Based Self-Healing Structural Composites

2020 ◽  
Vol 10 (17) ◽  
pp. 5739
Author(s):  
Xenia Tsilimigkra ◽  
Dimitrios Bekas ◽  
Maria Kosarli ◽  
Stavros Tsantzalis ◽  
Alkiviadis Paipetis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Mechanical Performance ◽  
Urea Formaldehyde ◽  
Healing Process ◽  
Experimental Results ◽  
Self Healing ◽  
Healing Efficiency ◽  
A Minor

Microcapsule-based carbon fiber reinforced composites were manufactured by wet layup, in order to assess their mechanical properties and determine their healing efficiency. Microcapsules at 10%wt. containing bisphenol-A epoxy, encapsulated in a urea formaldehyde (UF) shell, were employed with Scandium (III) Triflate (Sc (OTf)3) as the catalyst. The investigation was deployed with two main directions. The first monitored changes to the mechanical performance due to the presence of the healing agent within the composite. More precisely, a minor decrease in interlaminar fracture toughness (GIIC) (−14%), flexural strength (−12%) and modulus (−4%) compared to the reference material was reported. The second direction evaluated the healing efficiency. The experimental results showed significant recovery in fracture toughness up to 84% after the healing process, while flexural strength and modulus healing rates reached up to 14% and 23%, respectively. The Acoustic Emission technique was used to support the experimental results by the onsite monitoring.

scholarly journals Effect of Using Different Resources of Premix in Diet on Some Egg Quality of Layer Hen

2021 ◽  
Vol 923 (1) ◽  
pp. 012041
Author(s):  
Hayder Mahdi Hamzah ◽  
Abbas Salim Hussein Al-Mnachi
Keyword(s):  
Shell Thickness ◽  
Laying Hens ◽  
Egg Quality ◽  
Relative Weight ◽  
Treatment Groups ◽  
General Average ◽  
The Mean ◽  
Significant Superiority ◽  
Care Company

Abstract A total of 84 laying hens, ISA Brown, 60 weeks age, were used, randomly distributed into four treatment groups with 3 replicates for each treatment. The treatments were distributed as follows: T1: added the premix to diet supplied by Nuscience Company. T2: added the premix to diet supplied by Provimi Company. T3: added the premix to diet supplied by Max Care Company. T4: added the premix to diet supplied by INTRACO Company. The results show that there were no significant differences in the relative weight of the shell, except for the mean, a significant superiority of T2 and T4 compared T3, a significant differences in the shell thickness. There were no significant differences in the relative weight of albumin, and a significant superiority in the general average, where T2 outperformed on T4. There were no significant differences in the yolk index. T3 and T2 were significantly superior to T1.

Recovery of Fracture Toughness on Self-Healing Epoxies Using Ternary Nanomodified Microcapsules: A Parametric Study

2019 ◽  
Vol 827 ◽  
pp. 258-262 ◽  
Author(s):  
Maria Kosarli ◽  
Kyriaki Tsirka ◽  
Stella Chalari ◽  
Antigoni Palantza ◽  
Alkiviadis S. Paipetis
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Parametric Study ◽  
External Surface ◽  
Self Healing ◽  
Healing Efficiency ◽  
Mean Diameter ◽  
Healing Agent ◽  
The Mean ◽  
Scanning Electron

This study is focused on the effect of the nanomodification of the microcapsules healing agent on the healing efficiency. In detail, nanomodified epoxy resin with both carbon nanotubes (CNTs) and carbon black (CB) diluted with a non-toxic solvent was encapsulated into UF capsules. The morphology of the external surface and the mean diameter was investigated via Scanning Electron Microscopy (SEM). In addition, the thermal stability was estimated with Thermogravimetric analysis and healing efficiency was evaluated for the polymer epoxy matrix. A parametric study was performed at various solvent percentages and catalyst percentages. Results indicated an increase of the healing efficiency with nanomodified capsules against of the use of conventional microcapsules.

scholarly journals The effect of feeding magnesium-enriched diets on the quality of the albumen of stored eggs

1977 ◽  
Vol 37 (1) ◽  
pp. 35-44 ◽  
Author(s):  
J. B. Monsey ◽  
D. S. Robinson ◽  
W. S. Miller ◽  
Margaret Ellis
Keyword(s):  
Food Consumption ◽  
Shell Thickness ◽  
Live Weight ◽  
Egg White ◽  
Egg Number ◽  
The Mean ◽  
Egg Shell ◽  
Mean Concentration ◽  
Effect Of Feeding

1. Pullets were given from 1-d-old diets containing 1.6, 4.1, 8.1 and 12.0 g Mg/kg. Only small effects of these diets on live weight, food consumption, egg number, egg weights or egg-shell thickness were observed except at the highest level (12.0 g Mg/kg) which caused diarrhoea and an appreciable lowering of the live weight of growing pullets. A further group was given from point-of-lay a diet containing 9.3 g Mg/kg.2. Eggs laid on 3 consecutive days from each of eighteen hens were collected at intervals of 3 weeks until the birds were 68.5 weeks old. Eggs laid on the 3rd day were used to determine the initial proportion of thick egg-white present and also the concentration of Mg, Ca, Na and K in the thick egg-white. Eggs laid on the 1st and 2nd days were stored at 20° for 20 d to establish the proportion of thick egg-white remaining after storage.3. With the unsupplemented diet the proportion of residual thick egg-white after storage of eggs for 20 d at 20° was 306, 161 and 305 mg/g total egg-white when the hens were 26.5, 53.5 and 68.5 weeks of age respectively. When the diet containing 9.3 g Mg/kg was given, the proportion of thick egg-white after storage remained approximately 400 mg/g throughout the period of the trial.4. The mean Mg concentration in the thick egg-white of eggs laid by hens given unsupplemented diets was 5.77 mm. The addition of extra Mg to the diet increased the content of Mg in the thick egg-white, for example when the diet contained 9.3 g Mg/kg the mean concentration rose to 7.69 mm.

scholarly journals Healing Efficiency of CNTs-Modified-UF Microcapsules That Provide Higher Electrical Conductivity and EMI Shielding Properties

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2753
Author(s):  
Maria Kosarli ◽  
Anastasia Polymerou ◽  
Georgios Foteinidis ◽  
Christos Vazouras ◽  
Alkiviadis S. Paipetis
Keyword(s):  
Thermal Stability ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Electromagnetic Interference ◽  
Urea Formaldehyde ◽  
Conductive Network ◽  
Self Healing ◽  
Shell Wall ◽  
Healing Efficiency ◽  
Emi Se

In this study, the effect of the addition of multi-walled carbon nanotubes (MWCNTs), at three percentages, into the urea-formaldehyde (UF) shell-wall of microcapsules on the healing efficiency is reported. The modified shell-wall created a conductive network in semi-conductive epoxies, which led to an improvement of the electromagnetic interference shielding effectiveness (EMI SE); utilizing the excellent electrical properties of the CNTs. The microcapsule’s mean diameter and shell wall were examined via scanning electron microscopy (SEM). Thermal stability was evaluated via thermogravimetric analysis (TGA). The healing efficiency was assessed in terms of fracture toughness, while the electrical properties were measured using impedance spectroscopy. The measurements of the EMI SE were carried out in the frequency range of 7–9 GHz. The derived results indicated that the incorporation of the CNTs resulted in a decrease in the mean size of the microcapsules, while the thermal stability remained unchanged. In particular, the introduction of 0.5% w/v CNTs did not affect the healing efficiency, while it increased the initial mechanical properties of the epoxy after the incorporation of the self-healing system by 27%. At the same time, it led to the formation of a conductive network, providing electrical conductivity to the epoxies. The experimental results showed that the SE increased on average 5 dB or more after introducing conductive microcapsules.

Optimization of preparation conditions of epoxy-containing nanocapsules

2017 ◽  
Vol 24 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Xiulan Cai ◽  
Datian Fu ◽  
Ailan Qu
Keyword(s):  
Shell Thickness ◽  
Urea Formaldehyde ◽  
Average Diameter ◽  
Agitation Rate ◽  
Self Healing ◽  
Processing Conditions ◽  
Optimum Conditions ◽  
Preparation Conditions ◽  
Scanning Electron

AbstractNanocapsules using epoxy and urea formaldehyde as core and shell materials, respectively, were prepared by in situ polymerization. The effects of processing conditions on the properties of epoxy nanocapsules were systematically investigated based on w(core) and average diameter of nanocapsules through the method of orthographic factorial design, and the optimum processing conditions were concluded. The results indicated that the key influencing factors on w(core) was agitation rate; on average, diameter of nanocapsules was emulsifier. The analysis of mechanical properties and thermal stability indicated that nanocapsules prepared in the optimum conditions are suitable for storage and the optimum content of nanocapsules was 10%. Scanning electron microscopy indicated that nanocapsules were well encapsuled and presented uniform spheres with rough surface. The broken nanocapsule indicated that the shell of the nanocapsule was thin and could coat more epoxy resin. The analysis of finite element method proved that nanocapsules prepared in the optimum conditions with an average of 110 nm shell thickness were suitable for self-healing materials.

A MICROCAPSULE TECHNOLOGY BASED SELF-HEALING SYSTEM FOR CONCRETE STRUCTURES

2013 ◽  
Vol 07 (03) ◽  
pp. 1350014 ◽  
Author(s):  
BIQIN DONG ◽  
NINGXU HAN ◽  
MING ZHANG ◽  
XIANFENG WANG ◽  
HONGZHI CUI ◽  
...  
Keyword(s):  
Urea Formaldehyde ◽  
Concrete Structures ◽  
The Self ◽  
Polymerization Reaction ◽  
Formaldehyde Resin ◽  
Self Healing ◽  
Cementitious Composite ◽  
Healing System ◽  
Healing Efficiency ◽  
Healing Agent

In the study, a novel microcapsule technology based self-healing system for concrete structures has been developed. Through situ-polymerization reaction, the microcapsule is formed by urea formaldehyde resin to pack the epoxy material, which is applied to cementitious composite to achieve self-healing effect. The experimental results revealed that the self-healing efficiency of the composite can be accessed from the recovery of the permeability and strength for the cracked cementitious specimens as the healing agent in the microcapsule acting on the cracks directly. Scanning electronic microscope (SEM/EDX) results show that the epoxy resin is released along with the cracking of the cementitious composite and prevent from cracks continued growth. Further studies show that the self-healing efficiency is affected by the pre-loading of composite, particle size of microcapsule, aging duration of healing agent and so on.

scholarly journals Effect of Microcapsule Content on Diels-Alder Room Temperature Self-Healing Thermosets

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3064
Author(s):  
Sadella C. Santos ◽  
John J. La Scala ◽  
Giuseppe R. Palmese
Keyword(s):  
Urea Formaldehyde ◽  
Average Diameter ◽  
Diels Alder ◽  
Phenyl Acetate ◽  
Self Healing ◽  
Healing System ◽  
Diffusion Analysis ◽  
Healing Efficiency ◽  
Physical And Chemical ◽  
Crack Interface

A furan functionalized epoxy-amine thermoset with an embedded microcapsule healing system that utilizes reversible Diels-Alder healing chemistry was used to investigate the influence of microcapsule loading on healing efficiency. A urea-formaldehyde encapsulation technique was used to create capsules with an average diameter of 150 µm that were filled with a reactive solution of bismaleimide in phenyl acetate. It was found that optimum healing of the thermoset occurred at 10 wt% microcapsule content for the compositions investigated. The diffusion of solvent through the crack interface and within fractured samples was investigated using analytical diffusion models. The decrease in healing efficiency at higher microcapsule loading was attributed partially to solvent-induced plasticization at the interface. The diffusion analysis also showed that the 10% optimum microcapsule concentration occurs for systems with the same interfacial solvent concentration. This suggests that additional physical and chemical phenomena are also responsible for the observed optimum. Such phenomena could include a reduction in surface area available for healing and the saturation of interfacial furan moieties by reaction with increasing amounts of maleimide. Both would result from increased microcapsule loading.

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