Linking Nanoscale Chemical Changes to Bulk Material Properties in IEPM Polymer Composites Subject to Impact Dynamics

Attard, Thomas L.; He, Long

doi:10.1021/acsami.9b04741

Cited by 4 publications

(20 citation statements)

References 53 publications

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“…The role of aliphatic-based polyurea moieties is critical in the design of x-IEPM via epoxy surface treatment: in their reactive form, polyurea functional groups are introduced to a curing epoxy network, generating a three-part reaction of (epoxide) + (amine epoxy hardener) + (isocyanate) that produces new epoxy-urea chemical bonds. [17,30] This comprises the IEPM; see the boundary that separates epoxy from polyurea in Figure 1b. The role of epoxy is also critical, contributing to the IDA modification chemistry and serving as the structural (coupling) link between CF/E and IEPM that introduces the loss modulus property to C-IEPM.…”

Section: Methodsmentioning

confidence: 99%

“…[17] Attard [39] described the IEPM chemical structure and exchange reactions of the (-NCO) functional group with (-NH 2 ) group from epoxy, resulting in a 1,4 addition carbonyl-stable isocyanate-accepting epoxy modification, [39] shown in Figure 2. The results may be applied across multiple-scales to integrate various attributes into several largescale systems, including ballistic-resistant shields (military structures), [30] coastal bridges subject to large surge and lateral wave forces (hurricane resistance), [31] residential storm rooms (tornado resistance), [40] impact resistant and energy efficient tilt-up wall constructions (commercial warehouses), [41] moisture-resistant systems (flood control), [27] and carbon-fiber systems combine mechanical performance and reduced carbon fiber consumption to lower cost and the carbon-footprint.…”

Section: Methodsmentioning

confidence: 99%

“…[27,30] In IEPM-t c = 0 (width: 30 to 50 µm), [30] the significant presence of polyetheramine (-NH 2 ) and epoxide groups (due to fast diffusivity of epoxy species) conduces a large number of reactions with isocyanate groups to produce a high-quality IEPM. In Figure 5b, IEPM-0.5 (width: 20 to 30 µm) [30] shows less physical "topography," or jaggedness, as more etheramine groups react with epoxide, decreasing epoxy diffusivity, in Figure 5c where IEPM width ≤ 2 µm. [30] When no chemical reaction occurs at the epoxy-polyurea boundary (IEPM-24), see Figure 5d, the interface is prone to fracturing even during the microtome process (sample preparation).…”

Section: Surface Morphology and Microstructure Characterization Of Iepmmentioning

confidence: 99%

“…The consequent introduction of "internal damage barriers" [29] isolated microscopic damage to the concrete and CF/E structures, rendering individual cracks harmless. Attard and He [30] later uncovered the IDA reaction, identifying the unique chemical bond structures that described the IEPM.…”

mentioning

confidence: 99%

“…[33][34][35] To compare, C-IEPM sans IDA modification, meaning that polyurea is topically applied to cured epoxy after 24 h (t c = 24), results in a poorly bonded IEPM composed of a physical mixture of weak, secondary bonds, e.g., intermolecular bonds due to van der Waal forces or hydrogen bonds. [30,[36][37][38] The output is a conventional fiber consumptive and expensive CF/E with minimal energy transferability and standard environmental benefits.…”

mentioning

confidence: 99%

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Bulk Energy Transferability Linked to Critical N–H Modes of an Interfacial Nanoscale Surface Modification via Unique Isophorone Diisocyanate Amine Exchange Reaction

Attard¹

2021

Macro Chemistry & Physics

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Although carbon dioxide concentrations are at a record high [3] -one ton of manufactured carbon fiber emits twenty tons of CO 2 [4,5] -lighter structural components can drastically lower CO 2 consumption. This includes carbon-fiber-constructed automobiles and aircraft that are 30% and 20% lighter that can reduce CO 2 emissions by 50 tons and 1400 tons over a ten-year lifecycle. And while carbon-fiber technologies generally reduce CO 2 emissions by 20%, [6] life-cycle analysis studies further highlight its environmental benefit via productionwaste reduction efforts and recycling [7] of discarded fiber and matrix (epoxy).To further distinguish the performanceenvironmental benefit, this study examines integration of bulk energy transferability into CF/E via modification of the surface epoxy to overcome its inherent performance limitations and to reduce fiber production, CO 2 emissions, cost, and waste. Furthermore, the novel surface modification may be utilized in general FRP systems, where the global composites market is expected to reach $131.6 billion by 2024. [8] Paucity of energy transferability remains a lofty design parameter in brittle FRPs that have low fracture toughness and material damping. [9] This is often over-compensated by aggrandizing fiber quantity, which amplifies cost and predisposes FRPs, including CF/E, to unexpected failure and potentially greater CO 2 emissions. However, due to their versatility, FRPs continue to be researched in various exposures, [10,11] specifically CF/E in extreme conditions. This includes the use of coatings to complement composite performance, where, for example, polyurea-coated composites dissipated blast-induced energy proportional to the polyurea thickness. [12,13] In blast-designed wall panels, polyurea fails to efficiently transfer the incoming energy, resulting in support shear failure. Although polyurea is characteristically weak (12-17 MPa), [14] it also made its way into projectile impact studies as a laminate coating for aluminum plates [15,16] but with minimal relevant success. Inherently, polyurea has a low loss modulus [17] that is similar to that of pure epoxy (in CF/E). In order to effectuate relevant damping in polyurea-coated composites, the polyurea thickness should be considerably large, making pure polyurea a cost-ineffective solution for enhancing FRP performance. [18] A surface-modified carbon-fiber reinforced epoxy (CF/E) via a unique isophorone diisocyanate amine (IDA) reaction produces a new interfacial epoxy-polyurea "matrix" (IEPM) that elicits excellent mechanical energy transferability in brittle CF/E. The chemical bonding property in the IEPM molecule is produced via moieties of an epoxy mixture and N-H-concentrated urea molecules, where IDA thermodynamics are controlled via a curing parameter, t c (in hours). Nano-scale properties of the IDA reaction, confirmed via fourier-transform infrared spectroscopy and chemical mapping of molecules comprising the IEPM structure, are linked to bulk mechanical energy transferability, specifically l...

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Section: Methodsmentioning

confidence: 99%