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.

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.

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 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.

scholarly journals ANALYSIS OF ROUTING PROTOCOLS IN FLYING WIRELESS NETWORKS

2019 ◽  
Vol 01 (03) ◽  
pp. 148-160
Author(s):  
Krishnaraj Natarajan
Keyword(s):  
Wireless Networks ◽  
Energy Consumption ◽  
Wireless Network ◽  
Routing Protocol ◽  
Routing Protocols ◽  
Life Time ◽  
Self Healing ◽  
Centralized Control ◽  
Network Life Time

The wireless network that are formed on the fly, without relying on the previous infrastructure, including the autonomous devices that lie nearby are called the flying wireless networks. Despite of the networks, self-configuring and self-healing nature, it incurs many challenges due to its mobile nature, limited battery span and the lack of the centralized control, so these wireless network requires a perfect routing protocol addressing the challenges and improving the performance of the network, so the paper presents the survey on the various routing protocols that enhances the performance of the flying wireless network. The survey is further continued with the analysis of the routing protocols to evince the capability of the same on the grounds of network life time, energy consumption and the quality of service.

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.

The Relationship Between Interoception and Metacognition

2016 ◽  
Vol 30 (2) ◽  
pp. 76-86 ◽  
Author(s):  
Judith Meessen ◽  
Verena Mainz ◽  
Siegfried Gauggel ◽  
Eftychia Volz-Sidiropoulou ◽  
Stefan Sütterlin ◽  
...  
Keyword(s):  
Memory Performance ◽  
Memory Task ◽  
Demographic Characteristics ◽  
Metacognitive Awareness ◽  
Interoceptive Awareness ◽  
Future Research ◽  
Heartbeat Perception ◽  
Interoceptive Accuracy ◽  
The Relationship

Abstract. Recently, Garfinkel and Critchley (2013) proposed to distinguish between three facets of interoception: interoceptive sensibility, interoceptive accuracy, and interoceptive awareness. This pilot study investigated how these facets interrelate to each other and whether interoceptive awareness is related to the metacognitive awareness of memory performance. A sample of 24 healthy students completed a heartbeat perception task (HPT) and a memory task. Judgments of confidence were requested for each task. Participants filled in questionnaires assessing interoceptive sensibility, depression, anxiety, and socio-demographic characteristics. The three facets of interoception were found to be uncorrelated and interoceptive awareness was not related to metacognitive awareness of memory performance. Whereas memory performance was significantly related to metamemory awareness, interoceptive accuracy (HPT) and interoceptive awareness were not correlated. Results suggest that future research on interoception should assess all facets of interoception in order to capture the multifaceted quality of the construct.

The relationship between optimism, personal control and quality of life of patients with COPD

2002 ◽  
Author(s):  
R. Arnold ◽  
A. V. Ranchor ◽  
N. H. T. ten Hacken ◽  
G. H. Koeter ◽  
V. Otten ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Personal Control ◽  
The Relationship
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