The tribological, mechanical, and thermal properties of an epoxy crosslinking network incorporated with 3C‐SiC nanoparticles, serving as a metal‐free friction material were investigated by molecular dynamics simulations. The considered models encompass pure epoxy materials with 35%, 50%, 65%, and 80% crosslinking degrees, as well as 3C‐SiC/epoxy composite materials at the same crosslinking levels. Glass transition temperature (
In order to better understand the design rules of epoxy–phenol thermosets we will report on the chemistry and (thermo)mechanical properties of cured epoxy–phenol thermoset films.
- NSF-PAR ID:
- 10367442
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Applied Polymer Science
- Volume:
- 138
- Issue:
- 39
- ISSN:
- 0021-8995
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract T g) of the eight models was analyzed, and the result shows augmenting crosslinking density and addition of 3C‐SiC nanofillers improveT gof all models. Fractional free volume of each model was quantified to reflect the features of epoxy materials and influence the properties at the atomic scale. Frictional force, normal force, and coefficient of friction (COF) were calculated to elucidate the tribological performance of the epoxy‐based materials. The introduction of 3C‐SiC nanofillers reduces COF. With nanofillers, higher crosslinking degree brings lower COF except 80% crosslinking degree, while without nanofillers, higher COFs are obtained with 35% and 80% crosslinking degrees. 3C‐SiC/epoxy composite with heightened crosslinking degree demonstrates superior Young's modulus, elevated tensile stress, and relatively smaller strain. Thermal conductivity analysis highlights the positive impact of both increased crosslinking density and incorporation of 3C‐SiC nanofillers on heat transfer. Temperature elevation further enhances thermal conductivity. -
more » « less
Abstract The effects of annealing a glassy polymer at temperatures well below
T gon the dynamic linear viscoelastic properties were investigated. The polymer was an epoxy thermoset with aT gof 182°C. Specimens were annealed from 2 h to up to 600 h at temperatures from −100°C (T g−282°C) up toT g. At annealing temperatures just belowT g, there was no effect of annealing, and annealing at −100°C (T g−282°C) showed no difference between 2 and 6 h annealing, although annealing effects might be seen at longer times. At temperatures between −50°C (T g−232°C) and 170°C (T g−12°C) the storage isotherms increased with annealing while the loss isotherms decreased. In addition, the heat capacity as measured via DSC after annealing at 50°C (T g−132°C) and 100°C (T g−82°C) exhibited endothermic peaks approximately 40°C above the annealing temperature. This study clearly shows that a material deep in the glassy state is not frozen, but undergoes continuing evolution. The nature of deep glass aging is different than physical aging in theT gregion, where deep in the glass the relaxation spectrum changes magnitude and shape but does not shift along the log frequency axis in contrast to physical aging in theT gregion. -
Thermoset networks are chemically cross-linked materials that exhibit high heat resistance and mechanical strength; however, the permanently cross-linked system makes end-of-life degradation difficult. Thermosets that are inherently degradable and made from renewably derived starting materials are an underexplored area in sustainable polymer chemistry. Here, we report the synthesis of novel sugar- and terpene-based monomers as the enes in thiol–ene network formation. The resulting networks showed varied mechanical properties depending on the thiol used during cross-linking, ranging from strain-at-breaks of 12 to 200%. Networks with carveol or an isosorbide-based thiol incorporated showed plastic deformation under tensile stress testing, while geraniol-containing networks demonstrated linear stress–strain behavior. The storage modulus at the rubbery plateau was highly dependent on the thiol cross-linker, showing an order of magnitude difference between commercial PETMP, DTT, and synthesized Iso2MC. Thermal degradation temperatures were low for the networks, primarily below 200 °C, and the Tg values ranged from −17 to 31 °C. Networks were rapidly degraded under basic conditions, showing complete degradation after 2 days for nearly all synthesized thermosets. This library demonstrates the range of thermal and mechanical properties that can be targeted using monomers from sugars and terpenes and expands the field of renewably derived and degradable thermoset network materials.more » « less
-
more » « less
Abstract The sensitized photooxidation of
ortho ‐prenyl phenol is described with evidence that solvent aproticity favors the formation of a dihydrobenzofuran [2‐(prop‐1‐en‐2‐yl)‐2,3‐dihydrobenzofuran], a moiety commonly found in natural products. Benzene solvent increased the total quenching rate constant (k T) of singlet oxygen with prenyl phenol by ~10‐fold compared to methanol. A mechanism is proposed with preferential addition of singlet oxygen to prenyl site due to hydrogen bonding with the phenol OH group, which causes a divergence away from the singlet oxygen ‘ene’ reaction toward the dihydrobenzofuran as the major product. The reaction is a mixed photooxidized system since an epoxide arises by a type I sensitized photooxidation. -
more » « less
ABSTRACT A new series of six imidazolium‐based ionenes containing aromatic amide linkages has been developed. These ionene‐polyamides are all constitutional isomers varying in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) along the polymer backbone. The physical properties as well as the gas separation behaviors of the corresponding membranes have been extensively studied. These ionene‐polyamide membranes show excellent thermal and mechanical stabilities, together with self‐healing and shape memory characteristics. Most importantly, [TC‐API(
p )‐Xy][Tf2N] and [IC‐API(m )‐Xy][Tf2N] membranes (TC, terephthaloyl chloride; API, 1‐(3‐aminopropyl)imidazole; Xy, xylyl; Tf2N, bis(trifluoromethylsulfonyl) imide; IC, isophthaloyl chloride), where the amide and xylyl linkages are attached at para and meta positions, exhibit superior selectivity for CO2/CH4and CO2/N2gas pairs. We also demonstrate the transport properties and diverse applicability of our newly developed ionene‐polyamides, particularly [TC‐API(p )‐Xy][Tf2N], for various industrial applications. © 2019 Society of Chemical Industry
