scholarly journals A new self-healing epoxy with tungsten (VI) chloride catalyst

2007 ◽  
Vol 5 (18) ◽  
pp. 95-103 ◽  
Author(s):  
Jason M Kamphaus ◽  
Joseph D Rule ◽  
Jeffrey S Moore ◽  
Nancy R Sottos ◽  
Scott R White
Keyword(s):  
Cost Effective ◽  
Environmental Stability ◽  
Catalyst Precursor ◽  
Crack Plane ◽  
Self Healing ◽  
Delivery Methods ◽  
Chloride Catalyst ◽  
Healing Agent ◽  
Recovery Protocols ◽  
Commercial Applications

Using self-healing materials in commercial applications requires healing chemistry that is cost-effective, widely available and tolerant of moderate temperature excursions. We investigate the use of tungsten (VI) chloride as a catalyst precursor for the ring-opening metathesis polymerization of exo- dicyclopentadiene ( exo -DCPD) in self-healing applications as a means to achieve these goals. The environmental stability of WCl 6 using three different delivery methods was evaluated and the associated healing performance was assessed following fracture toughness recovery protocols. Both as-received and recrystallized forms of the WCl 6 resulted in nearly complete fracture recovery in self-activated tests, where healing agent is manually injected into the crack plane, at 12 wt% WCl 6 loading. In situ healing using 15 wt% microcapsules of the exo -DCPD produced healing efficiencies of approximately 20%.

scholarly journals Tracking capsule activation and crack healing in a microcapsule-based self-healing polymer

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
S. A. McDonald ◽  
S. B. Coban ◽  
N. R. Sottos ◽  
P. J. Withers
Keyword(s):  
Healing Process ◽  
Polymeric Materials ◽  
Time Lapse ◽  
Repair Process ◽  
Three Dimensions ◽  
Crack Plane ◽  
Self Healing ◽  
Crack Healing ◽  
Healing Agent ◽  
First Time

AbstractStructural polymeric materials incorporating a microencapsulated liquid healing agent demonstrate the ability to autonomously heal cracks. Understanding how an advancing crack interacts with the microcapsules is critical to optimizing performance through tailoring the size, distribution and density of these capsules. For the first time, time-lapse synchrotron X-ray phase contrast computed tomography (CT) has been used to observe in three-dimensions (3D) the dynamic process of crack growth, microcapsule rupture and progressive release of solvent into a crack as it propagates and widens, providing unique insights into the activation and repair process. In this epoxy self-healing material, 150 µm diameter microcapsules within 400 µm of the crack plane are found to rupture and contribute to the healing process, their discharge quantified as a function of crack propagation and distance from the crack plane. Significantly, continued release of solvent takes place to repair the crack as it grows and progressively widens.

Preparation and Performance of Self-Healing Epoxy Composites by Microcapsulated Approach

2014 ◽  
Vol 636 ◽  
pp. 73-77 ◽  
Author(s):  
Xin Hua Yuan ◽  
Qiu Su ◽  
Li Yin Han ◽  
Qian Zhang ◽  
Yan Qiu Chen ◽  
...  
Keyword(s):  
Impact Strength ◽  
Epoxy Matrix ◽  
The Self ◽  
Epoxy Composites ◽  
Fracture Plane ◽  
Crack Plane ◽  
Curing Agent ◽  
Self Healing ◽  
Healing Agent ◽  
The Impact

Microencapsulated E-51 epoxy resin healing agent and phthalic anhydride latent curing agent were incorporated into E-44 epoxy matrix to prepare self-healing epoxy composites. When cracks were initiated or propagated in the composites, the microcapsules would be damaged and the healing agent released. As a result, the crack plane was healed through curing reaction of the released epoxy latent curing agent. In the paper, PUF/E-51 microcapsules were prepared by in-situ polymerization. The mechanical properties of the epoxy composites filled with the self-healing system were evaluated. The impact strength and self-healing efficiency of the composites are measured using a Charpy Impact Tester. Both the virgin and healed impact strength depends strongly on the concentration of microcapsules added into the epoxy matrix. Fracture of the neat epoxy is brittle, exhibiting a mirror fracture surface. Addition of PUF/E-51 microcapsules decreases the impact strength and induces a change in the fracture plane morphology to hackle markings. In the case of 8.0 wt% microcapsules and 3.0 wt% latent hardener, the self-healing epoxy exhibited 81.5% recovery of its original fracture toughness.

Fracture and Fatigue Behavior of a Self-Healing Polymer Composite

2002 ◽  
Vol 735 ◽  
Author(s):  
Eric N. Brown ◽  
Jeffrey S. Moore ◽  
Scott R. White ◽  
Nancy R. Sottos
Keyword(s):  
Fracture Toughness ◽  
Polymer Composite ◽  
Fatigue Behavior ◽  
Crack Propagation Rate ◽  
Polymer Composite Material ◽  
Fracture Mechanisms ◽  
Fatigue Crack Propagation Rate ◽  
Crack Plane ◽  
Self Healing ◽  
Healing Agent

ABSTRACTInspired by biological systems, in which damage triggers an autonomous healing response, a polymer composite material that can heal itself when cracked has been developed. The material consists of an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. This paper investigates issues of fracture and fatigue consequential to the development and optimization of this new class of materials. When damage occurs, the propagating crack ruptures the microcapsules, which releases healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with exposed catalyst, which bonds the crack faces closed. The efficiency of crack healing is defined as the ability of a healed sample to recover fracture toughness. Healing efficiencies of over 90% have been achieved. Embedded microcapsules significantly increase the fracture toughness and reduce the fatigue crack propagation rate of epoxy. Fracture mechanisms for neat epoxy and epoxy with embedded microcapsules are presented.

scholarly journals Stability of graphene-based heterojunction solar cells

RSC Advances ◽  
2015 ◽  
Vol 5 (90) ◽  
pp. 73575-73600 ◽  
Author(s):  
Eric Singh ◽  
Hari Singh Nalwa
Keyword(s):  
Solar Cells ◽  
Environmental Stability ◽  
Light Illumination ◽  
Atmospheric Conditions ◽  
Air Humidity ◽  
Heterojunction Solar Cells ◽  
Commercial Applications

The long-term environmental stability and degradation of graphene-based heterojunction solar cells under different atmospheric conditions such as air, humidity, temperature, and light illumination for commercial applications are discussed.

Review on modification strategies of polyethylene/polypropylene immiscible thermoplastic polymer blends for enhancing their mechanical behavior

2018 ◽  
Vol 51 (4) ◽  
pp. 291-336 ◽  
Author(s):  
Antimo Graziano ◽  
Shaffiq Jaffer ◽  
Mohini Sain
Keyword(s):  
High Performance ◽  
Cost Effective ◽  
Good Method ◽  
Waste Recycling ◽  
Industrial Applications ◽  
Polymer Waste ◽  
Reactive Compatibilization ◽  
Brittle To Ductile Transition ◽  
Commercial Applications ◽  
Effective Product

Blends of polyethylene (PE) and polypropylene (PP) have always been the subject of intense reasearch for encouraging polymer waste recycling while producing new materials for specific applications in a sustainable way. However, being thermodynamically immiscible, these polyolefins form a binary system usually exhibiting lower performances compared with those of the homopolymers. Many studies have been carried out to better understand the PE/PP blend compatibilization for developing a high-performance and cost-effective product. Both nonreactive and reactive compatibilization promote the brittle to ductile transition for a PE/PP blend. However, the final product usually does not meet the requirements for high demanding commercial applications. Therefore, further PE/PP modification with a reinforcing filler, being either synthetic or natural, proved to be a good method for manufacturing high-performance reinforcend polymer blend composites, with superior and tailored properties. This review summarizes the recent progress in compatibilization techniques applied for enhancing the interfacial adhesion between PE and PP. Moreover, future perspectives on better understanding the influence of themodynamics on PE/PP synergy are discussed to introduce more effective compatibilization strategies, which will allow this blend to be used for innovative industrial applications.

scholarly journals Post-Disaster Infrastructure Delivery for Resilience

2021 ◽  
Vol 13 (6) ◽  
pp. 3458
Author(s):  
Mikhail Chester ◽  
Mounir El Asmar ◽  
Samantha Hayes ◽  
Cheryl Desha
Keyword(s):  
Cost Effective ◽  
Project Delivery ◽  
Delivery Methods ◽  
Project Delivery Methods ◽  
Alternative Project Delivery Methods ◽  
Resilient Infrastructure ◽  
Alternative Project Delivery ◽  
Innovative Contracting ◽  
Alternative Delivery ◽  
Post Disaster

As climate change increases the frequency and intensity of disasters and associated infrastructure damage, Alternative Project Delivery Methods are well positioned to enable innovative contracting and partnering methods for designing and delivering adaptation solutions that are more time- and cost-effective. However, where conventional “build-back-as-before” post-disaster reconstruction occurs, communities remain vulnerable to future disasters of similar or greater magnitude. In this conceptual paper, we draw on a variety of literature and emergent practices to present how such alternative delivery methods of reconstruction projects can systematically integrate “build-back-better” and introduce more resilient infrastructure outcomes. Considering existing knowledge regarding infrastructure resilience, post-disaster reconstruction and project delivery methods, we consider the resilience regimes of rebound, robustness, graceful extensibility, and sustained adaptability to present the potential for alternative project delivery methods to improve the agility and flexibility of infrastructure against future climate-related and other hazards. We discuss the criticality of continued pursuit of stakeholder engagement to support further improvements to project delivery methods, enabling new opportunities for engaging with a broader set of stakeholders, and for stakeholders to contribute new knowledge and insights to the design process. We conclude the significant potential for such methods to enable resilient infrastructure outcomes, through prioritizing resilience alongside time and cost. We also present a visual schematic in the form of a framework for enabling post-disaster infrastructure delivery for resilience outcomes, across different scales and timeframes of reconstruction. The findings have immediate implications for agencies managing disaster recovery efforts, offering decision-support for improving the adaptive capacity of infrastructure, the services they deliver, and capacities of the communities that rely on them.

Mechanical responses of microencapsulated self-healing cementitious composites under compressive loading based on a micromechanical damage-healing model

2021 ◽  
pp. 105678952110112
Author(s):  
Kaihang Han ◽  
Jiann-Wen Woody Ju ◽  
Yinghui Zhu ◽  
Hao Zhang ◽  
Tien-Shu Chang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Micromechanical Model ◽  
Cementitious Composites ◽  
Self Healing ◽  
Damage Degree ◽  
Healing Efficiency ◽  
The Matrix ◽  
Healing Agent ◽  
Damage Healing

The cementitious composites with microencapsulated healing agents have become a class of hotspots in the field of construction materials, and they have very broad application prospects and research values. The in-depth study on multi-scale mechanical behaviors of microencapsulated self-healing cementitious composites is critical to quantitatively account for the mechanical response during the damage-healing process. This paper proposes a three-dimensional evolutionary micromechanical model to quantitatively explain the self-healing effects of microencapsulated healing agents on the damage induced by microcracks. By virtue of the proposed 3 D micromechanical model, the evolutionary domains of microcrack growth (DMG) and corresponding compliances of the initial, extended and repaired phases are obtained. Moreover, the elaborate studies are conducted to inspect the effects of various system parameters involving the healing efficiency, fracture toughness and preloading-induced damage degrees on the compliances and stress-strain relations. The results indicate that relatively significant healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will lead to a higher compressive strength and stiffness. However, the specimen will break owing to the nucleated microcracks rather than the repaired kinked microcracks. Further, excessive higher values of healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will not affect the compressive strength of the cementitious composites. Therefore, a stronger matrix is required. To achieve the desired healing effects, the specific parameters of both the matrix and microcapsules should be selected prudently.

Numerical investigation into effect of self-healing composite microcapsules thickness and diameter on their failure strength

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Raj Kumar Pittala ◽  
Satish Ben B. ◽  
Syam Kumar Chokka ◽  
Niranjan Prasad
Keyword(s):  
Matrix Composite ◽  
Polymer Matrix ◽  
Shell Thickness ◽  
Polymer Matrix Composite ◽  
Thickness Effect ◽  
Failure Strength ◽  
Self Healing ◽  
Content Type ◽  
Reinforced Polymer ◽  
Healing Agent

Purpose Microcapsule-embedded autonomic healing materials have the ability to repair microcracks when they come into contact with the crack by releasing the healing agent. The microcapsules with specific shape and thickness effect in releasing healing agent to the cracked surfaces. Thus, the purpose of this paper is to know the load bearing capacity of the self-healing microcapsules and the stresses developed in the material. Design/methodology/approach In the present study, self-healing microcapsule is modelled and integrated with the polymer matrix composite. The aim of the present study is to investigate failure criteria of Poly (methyl methacrylate) microcapsules by varying the shell thickness, capsule diameter and loading conditions. The strength of the capsule is evaluated by keeping the shell thickness as constant and varying the capsule diameter. Uniformly distributed pressure loads were applied on the capsule-reinforced polymer matrix composite to assess the failure strength of capsules and composite. Findings It is observed from the results that the load required to break the capsules is increasing with the increase in capsule diameter. The failure strength of microcapsule with 100 µm diameter and 5 µm thickness is observed as 255 MPa. For an applied load range of 40–160 N/mm2 on the capsules embedded composite, the maximum stress developed in the capsules is observed as 308 MPa. Originality/value Failure strengths of microcapsules and stresses developed in the microcapsule-reinforced polymer composites were evaluated.

Sign in / Sign up

Export Citation Format

Share Document