Accuracy in locating glass transitions: aging and gamma sterilization of vulcanized thermoplastic elastomers

Brostow, Witold; Deshpande, Sameer K.; Pietkiewicz, Dorota; Wisner, Steven R.

doi:10.1515/epoly.2009.9.1.1304

Cited by 9 publications

(8 citation statements)

References 27 publications

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“…As discussed in Ref. [29], the midpoint of the fall of G provides well the location of the glass transition temperature T g . Above T g the situation is inverted.…”

Section: Dynamic Mechanical Analysis (Dma)mentioning

confidence: 77%

Vulcanization Characteristics and Dynamic Mechanical Behavior of Natural Rubber Reinforced with Silane Modified Silica

Chonkaew¹,

Minghvanish²,

Kungliean³

et al. 2011

J. Nanosci. Nanotech.

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Two silane coupling agents were used for hydrolysis-condensation reaction modification of nanosilica surfaces. The surface characteristics were analyzed using Fourier transform infrared spectroscopy (FTIR). The vulcanization kinetics of natural rubber (NR) + silica composites was studied and compared to behavior of the neat NR using differential scanning calorimetry (DSC) in the dynamic scan mode. Dynamic mechanical analysis (DMA) was performed to evaluate the effects of the surface modification. Activation energy E(a) values for the reaction are obtained. The presence of silica, modified or otherwise, inhibits the vulcanization reaction of NR. The neat silica containing system has the lowest cure rate index and the highest activation energy for the vulcanization reaction. The coupling agent with longer chains causes more swelling and moves the glass transition temperature T(g) downwards. Below the glass transition region, silica causes a lowering of the dynamic storage modulus G', a result of hindering the cure reaction. Above the glass transition, silica-again modified or otherwise-provides the expected reinforcement effect.

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“…As discussed in Ref. [29], the midpoint of the fall of G provides well the location of the glass transition temperature T g . Above T g the situation is inverted.…”

Section: Dynamic Mechanical Analysis (Dma)mentioning

confidence: 77%

Vulcanization Characteristics and Dynamic Mechanical Behavior of Natural Rubber Reinforced with Silane Modified Silica

Chonkaew¹,

Minghvanish²,

Kungliean³

et al. 2011

J. Nanosci. Nanotech.

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“…[17,39] Decreasing the temperature below T g reduces the free volume. In principle, brittleness and crack propagation at lower temperature could result in enhanced time-dependent deformation, [39,40] but we consider it more likely that the slight increase in creep depth at ¡10 C on nylon 6 and non-exfoliated nanocomposite is a consequence of being on the shoulder of the b relaxation peak of nylon 6. Low-temperature DMA data on other nylon 6Àclay nanocomposites reported in [9] show that it is centred around ¡50 C and that tan d begins to rise again when the temperature decreases below »15 C. For nylon/EC-5, the creep depth was reduced over the range of 27 C to ¡10 C, which may imply that the shoulder of the b relaxation peak does not extend quite as far as ¡10 C in the near-surface region of the exfoliated nanocomposite, which could be explained by the improved molecular-level constraints due to the small size and high surface area of the clay platelets, together with the short inter-particle distance which prevents free rotation of the matrix molecular chains.…”

Section: Mechanical Properties At Sub-ambient Temperaturesmentioning

confidence: 99%

Investigation of the nanomechanical properties of nylon 6 and nylon 6/clay nanocomposites at sub-ambient temperatures

Chen

Beake

Bell

et al. 2016

Journal of Experimental Nanoscience

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The nanomechanical properties of nylon 6, nylon 6/exfoliated clay and nylon 6/non-exfoliated clay nanocomposites have been investigated from room temperature to ¡10 C in a controlled environment with humidity less than 1% RH. The hardness, elastic modulus and creep resistance of nylon 6 were improved in the nanocomposites across the temperature range. However, the effective reinforcement of the clay depended on the temperature due to the change between the glassy and transition states in the nylon. The exfoliated clay nanocomposite showed the greater improvements than in the non-exfoliated clay nanocomposite at all testing temperatures due to the improved constraint of the polymer chains by the clay platelets in the exfoliated structure. The surface mechanical properties of nylon 6 and the nanocomposites were also found to be highly sensitive to the moisture level during the tests; increasing the humidity in the room temperature tests resulted in a dramatic decrease in hardness and stiffness due to plasticisation by water molecules. The kinetics of the re-humidification process on nylon 6 were studied by monitoring the change in nanoindentation response. Analysis of the indentation creep revealed a significant change in the strain rate sensitivity when the humidity of the near-surface region probed by nanoindentation was in the vicinity of the glass transition.

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“…we show the storage modulus E ' versus temperature diagrams for some copolymers obtained by bulk polymerization. We recall that E ' descent is one of the methods of locating the glass transition temperature T g , while that temperature is actually representative of a region of temperatures…”

Section: Resultsmentioning

confidence: 99%

Porous crosslinked copolymers of octadecyl acrylate with acrylic acid as sorbers for crude petroleum spills

Atta

Brostow

Lobland

et al. 2013

Polymer International

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Bulk and suspension polymerization were used to prepare octadecyl acrylate/acrylic acid (ODA/AA) copolymers. AA content ranged from 0 to 90 mol%. Divinyl benzene was used as a crosslinker at several concentrations (1, 4 and 10 wt%). Isopropyl alcohol or dioctyl phthalate and methyl benzoate were used as the reaction solvents in the presence of poly(vinyl alcohol) as a dispersing agent and 2,2-azobis isobutyronitrile as the initiator. The polymers so prepared were coated onto poly(ethylene terephthalate) nonwoven (NWPET) fibers. The effects of copolymerization, feed composition, crosslinker concentration and reaction medium or solvent on morphology including porosity and the dynamic mechanical and swelling properties of the crosslinked polymers were determined. Swelling tests were performed in toluene and in 10% crude petroleum diluted with toluene. Bulk polymerization does not result in the formation of a continuous liquid absorbing material while suspension polymerization enables sorbers to be obtained with desired properties. Coating ODA/AA copolymers onto NWPET increases liquid absorption.

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Accuracy in locating glass transitions: aging and gamma sterilization of vulcanized thermoplastic elastomers

Cited by 9 publications

References 27 publications

Vulcanization Characteristics and Dynamic Mechanical Behavior of Natural Rubber Reinforced with Silane Modified Silica

Vulcanization Characteristics and Dynamic Mechanical Behavior of Natural Rubber Reinforced with Silane Modified Silica

Investigation of the nanomechanical properties of nylon 6 and nylon 6/clay nanocomposites at sub-ambient temperatures

Porous crosslinked copolymers of octadecyl acrylate with acrylic acid as sorbers for crude petroleum spills

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