4(%3)3 - Ecole nationale supÃ©rieure de chimie de Montpellier

More documents

Recommendations

Info

particular property. They do not provide information about the extent of recovery of other properties ofthe material during the healing process unless explained separately. The healing efficiencies can becalculated either after healing of a single microscopic crack or after a material has been broken and theparts then separated and rejoined prior to the healing efficiency measurement 15 . Further factors likehealing rate, number of times the material can be healed at the location and the extent of recovery ofpristine properties should also be considered.1.3 AUTONOMOUS SELF-HEALING POLYMERIC SYSTEMSThese polymeric systems, as defined in the previous section are characterized by their ability toundergo healing process initiated by the fracture itself. Such materials sometimes also referred asextrinsic self-healing materials rely on two quite comprehensively developed approaches namely:encapsulation and mechanoresponsive and will be discussed in this section.1.3.1 EncapsulationThe encapsulation approach refers to the embedding of a self-repair fluid filled fibers or capsulesor vesicles within the polymer matrix. In case of damage, the fluid holding reservoir would break therebyreleasing the fluid in the damage plane thus healing the material autonomously. These materials closelymimic healing mechanism observed in nature (Figure-1.1) however unlike biological counterparts; it ismuch simpler and accelerated. This approach primarily has been used for thermoset polymers and theircomposites though applicability has been established for protective coatings and even for packagingfilms 17 .Figure– 1.5: Hollow fiber based repair systems, a) Different configurations considered, b) Scanning ElectronMicroscopy image of a resin filled fiber 18 .5
The first work based on this approach, reported way back in early 90s consisted of concretereinforced with fibers filled with cyanoacrylate 19 and methylmethacrylate 20 adhesives. The idea was laterreplicated to polymeric system by embedding a two part epoxy crosslinking adhesive filled glass pipettesin a thermoset polymer matrix 21 . The technique was further investigated with different kind of hollowfibers and it was postulated that glass fibers were best suited for controlled fracture providing effectivehealing and also thicker composites were better in performance for healing studies 22 . In another work 18by Bleay et al., a two part system was investigated consisting either both epoxy resin & hardenercontained in adjacent fibers or one of them (hardener) dispersed over in microencapsulated form whilethe resin was contained in the fiber embedded within the polymer matrix (Figure – 1.5). Although it wasa onetime repair system however it validated the idea of controlled release of healing agent into apolymer matrix to stop the propagation of a crack, repair it and recover the mechanical properties.An alternative novel approach was developed by White et al. in 2001, where healing agent wasencapsulated in urea-formaldehyde microcapsules and embedded in a polymer matrix 23 . Upon crackintrusion, the healing agent would seep into the crack plane from ruptured capsules through capillaryaction where its polymerization takes place, triggered by contact with an embedded catalyst and thusleading to healing of the system (Figure– 1.6a).Figure– 1.6: The autonomic healing concept based on a microencapsulated healing agent embedded in a structuralcomposite matrix containing a catalyst capable of polymerizing the healing agent, a) Cracks forms in the matrixwherever damage occurs thus releasing the healing agent into the crack plane through capillary action which6
Page 1: THESISPRESENTED ATNATIONAL GRADUATE
Page 4 and 5: As the human civilization progress
Page 6 and 7: CHAPTER - 1 SELF-HEALING POLYMERIC
Page 8: 8.1.5 Atomic Force Microscopy …
Page 11 and 12: Synthetic engineering materials in
Page 13: esponse to a specific external stim
Page 17 and 18: een prepared from urea-formaldehyde
Page 19 and 20: monomer systems. The addition of EN
Page 21 and 22: Figure - 1.10: Self-healing process
Page 23 and 24: was required to reach healing effic
Page 25 and 26: In addition to above works, some ot
Page 27 and 28: that have been identified to be tak
Page 29 and 30: part of the chapter, these material
Page 31 and 32: Figure - 1.17: Self-healing of the
Page 33 and 34: commercialized under tradenames; Nu
Page 35 and 36: joined together at temperature high
Page 37 and 38: Inspired by these findings, the fir
Page 39 and 40: temperature greater than 80 o C in
Page 41 and 42: Figure - 1.27: Sulfur chemistry bas
Page 43 and 44: A different kind of sulfur chemistr
Page 45 and 46: Figure - 1.29: Dynamic covalent che
Page 47 and 48: cracks. The recovered droplets afte
Page 49 and 50: 23 White, S. R. et al. Autonomic he
Page 51 and 52: 65 Taber, D. F. & Frankowski, K. J.
Page 53 and 54: 107 Kushner, A. M., Vossler, J. D.,
Page 55: 148 Park, J. S., Kim, H. S. & Hahn,
Page 58 and 59: The value of subscripts “n”,
Page 60 and 61: The formation of spherical micelles
Page 62 and 63: the micelle assembly showed the pre
Page 64 and 65:
gain onto the electrodes by buildin
Page 66 and 67:
The resistance R can be further exp
Page 68 and 69:
empty-tower velocity U only depends
Page 70 and 71:
This apparent morphological switchi
Page 72 and 73:
In a further qualitative analysis,
Page 74 and 75:
noteworthy and though its feasibili
Page 76 and 77:
Furthermore within this range, lowe
Page 78 and 79:
Figure - 2.22: Scanning Electron Mi
Page 80 and 81:
While the resistance measurements g
Page 82 and 83:
In conclusion, a self-healing membr
Page 84 and 85:
23 Giacomelli, F. C., Riegel, I. C.
Page 86 and 87:
micelles enabled the membrane to se
Page 88 and 89:
The second class is represented by
Page 90 and 91:
To avoid the probable clogging of t
Page 92 and 93:
181614SP2 - iNumber of Particles121
Page 94 and 95:
1000900800y = 3E+06xR² = 0,9911y =
Page 96 and 97:
very high value of 1.5 g.l -1 . Thi
Page 98 and 99:
Since the only change in the membra
Page 100 and 101:
100Retention (%)8060400,100,20,40,6
Page 102 and 103:
Page 104 and 105:
(Figure - 3.20). A cursory look at
Page 106 and 107:
When compared to poly(styrene) NPs,
Page 108 and 109:
Page 110 and 111:
REFERENCES1 Metzler, R. & Klafter,
Page 112 and 113:
46 Bemporad, D., Luttmann, C. & Ess
Page 114 and 115:
In this chapter, preparation of 3D
Page 116 and 117:
obtain complex macromolecular archi
Page 118 and 119:
The polymerization was conducted at
Page 120 and 121:
proceeds, lesser monomer is availab
Page 122 and 123:
mg/ml),the micelles’ hydrodynamic
Page 124 and 125:
Figure - 4.15: The monolayer and mu
Page 126 and 127:
monolayer of micelles and topmost l
Page 128 and 129:
The presence of the dispersed micel
Page 130 and 131:
Heating the multilayer micelle asse
Page 132 and 133:
stable zipping of the micelles. Mul
Page 134 and 135:
24 Moad, G., Rizzardo, E. & Thang,
Page 136 and 137:
The concept of nano-gel based self-
Page 138 and 139:
Figure - 5.4: Size distribution of
Page 140 and 141:
In a typical process, the two compo
Page 142 and 143:
Figure - 5.10: 1HNMR spectra obtain
Page 144 and 145:
The 1 HNMR spectrum obtained for th
Page 146 and 147:
REFERENCES1 White, S. R. et al. Aut
Page 148 and 149:
healing ability shown by the membra
Page 150 and 151:
7. PERSPECTIVESBeing the first such
Page 153 and 154:
8. MATERIALS & METHODSThis chapter
Page 155 and 156:
8.1.3 PEG Filtration MeasurementsTh
Page 157 and 158:
addition of TEOS due to formation o
Page 159 and 160:
solution was ultrasonicated for 15
Page 161 and 162:
Triethylamine (TEA) (Sigma-Aldrich
Page 163 and 164:
To prepare the monolayer assembly o
Page 165 and 166:
was added followed by addition of 0
Page 168 and 169:
ELABORATION OF SELF-HEALING POLYMER
Page 170 and 171:
ELABORATION DES MEMBRANES POLYMERES
show all

4(%3)3 - Ecole nationale supÃ©rieure de chimie de Montpellier

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?