Molecular composites from sulfonated poly(<i>p</i>‐phenylene terephthalamide)

Dai, Y. K.; Chu, Evan Y.; Xu, Zhiyang; Pearce, E. M.; Okamoto, Y.; Kwei, T. K.

doi:10.1002/pola.1994.080320223

Cited by 12 publications

(6 citation statements)

References 21 publications

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“…PPTA polyanion was used to initiate the anionic polymerization of acrylamide, thereby forming a composite of PPTA anion and nylon‐3 that possessed good strength and stiffness 8. In another study, the addition of the sulfonic acid (SO 3 H) group to the phenylene ring of the PPTA molecule led to solubility in some solvents 9. On blending with poly(vinylpyridine), proton transfer occurred from the SO 3 H group to the nitrogen atom of the pyridine group.…”

Section: Introductionmentioning

confidence: 99%

Ionic poly(p‐phenylene terephthalamide)s: Preparation and characterization

Chen

Sauer

Hara

2001

J Polym Sci B Polym Phys

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The preparation and characterization of two types of ionic poly(p-phenylene terephthalamide) (PPTA) is described. A sufficient number of ionic groups were added to render modified PPTA soluble in dimethylsulfoxide (DMSO). In one type, a hydrogen atom of the amide group was replaced by an ionic propanesulfonate group. In the other type, one of the hydrogen atoms on the phenylene ring was replaced by an ionic sulfonate group. The ionic PPTAs in DMSO showed an upturn in viscosity at very low concentrations that was characteristic of the polyelectrolyte behavior. Fourier transform infrared spectra of these samples were also studied. When the ionic group was attached at the end of the short propane side chain, the intensity of both the free and hydrogen-bonded NOH stretching mode was reduced compared with that of PPTA. Depending on the location of the ionic group, there were some changes in the intensity and wave number of the asymmetric and symmetric vibrations of the ionic SO 3 Ϫ group and the stretching mode of the carbonyl group. In both ionic PPTAs, there was an upward shift in the frequency of the symmetric vibrations of the sulfonate ion when the counterion, having been monovalent, became divalent.

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Section: Introductionmentioning

confidence: 99%

Ionic poly(p‐phenylene terephthalamide)s: Preparation and characterization

Chen

Sauer

Hara

2001

J Polym Sci B Polym Phys

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“…One promising approach to producing a true molecular composite is to make rod and coil components thermodynamically miscible by introducing attractive interactions, such as hydrogen bonds (16)(17)(18), between them. This method has proven useful for enhancing miscibility in flexible-flexible blends.…”

Section: Parker Et Al Molecular Composites Via Ionic Interactions 55mentioning

confidence: 99%

Molecular Composites via Ionic Interactions and Their Deformation—Fracture Properties

Parker

Chen

Tsou

et al. 1996

ACS Symposium Series

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Molecular composites have been made from three types of ionic PPTA's and various polar polymers (PVP, S-AN, PVC, PEO), in which a good dispersion of rod molecules is achieved via ionic (ion-dipole) interactions. Optical/thermal testing and morphological observations by electron microscopes have indicated good dispersionof the rigid-rod PPTA molecules. Molecular composites based on amorphous matrix polymers are all transparent and show no phase separation upon heating; therefore, they are melt-processable. The deformation mode of the matrix polymer is modified significantly with the addition of rod molecules: e.g., while crazing is the only deformation mechanism of PVP and S-AN (30% AN), the addition of ionic PPTA molecules into these amorphous polymers induces shear deformation. This is due to interactions between rod and coil molecules at the molecular (or microscopic) level, unlike the situation in conventional fiber composites, in which interactions between fiber and matrix polymer occur only at the interface during load transfer. The observed deformation modes suggest that fracture properties of these molecular composites should be enhanced. Mechanical tests made on three different composite systems do show enhanced ductility (toughness) in addition to increased stiffness/strength for the molecular composites, having either an amorphous or semicrystalline polymer matrix.Conventional fibers for advanced composites, such as carbon fiber and Kevlar fiber, are aggregates of fibrils and microfibrils, and therefore they contain many inherent defects that can initiate cracks and lead to premature failure of the composite. The idea of "molecular (level) composites" is based on the fact that an individual rigid-rod molecule, such as a poly(p-phenylene terephthalamide) (PPTA) molecule, has no defect; therefore, the theoretical strength due to covalent bonds in the Corresponding author 0097-6156/96/0632-0054$15.00/0

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“…8,9 A case in which strong polar interactions between reinforcement and matrix has been reported is the (conventional) short-cut fiber composite system of poly(p-phenyleneterephthalamide)/poly(methyl methacrylate), [13][14][15] PPTA/PMMA. The interaction between the amide groups of PPTA and the polar carboxyl groups of PMMA was advanced in refs 13-15 as the cause of a new R′ relaxation process, which occurred after the main R relaxation of the matrix.…”

Section: Introductionmentioning

confidence: 99%

“…An enhanced reinforcing efficiency should obtain both due to micromechanical reasons (the high aspect ratio due to the reduction to a molecular size of the fiber diameter) and as a consequence of the increased fraction of tie molecules, 2 which results in the case of having, instead of a macroscopic fiber, the same amount of reinforcing agent in the form of finely dispersed microfibrils. The dispersion of the rod-like molecules itself can be achieved either by blending solutions of both polymers, 2,[6][7][8][9] by graft copolymerization, 2,[10][11][12] or, more recently, by in situ rod formation techniques. 5 Ideally, reinforcement should be at a maximum in the case of a homogeneous dispersion of the microfibrils in the matrix, but this situation is practically never achieved because of the high aggregation tendency 12 of the rod-like molecules: hydrogen bonding of the molecules themselves and a low entropy of mixing of the system rigid rod/flexible matrix coils cause the composite to phase separate.…”

Section: Introductionmentioning

confidence: 99%

“…Several ways to counterbalance the incompatibility of coils and rods have been attempted; one of them is the enhancement of interactions (hydrogen bonding) between the rod-like molecules and the matrix molecules in order to favour the free energy of mixing. 8,9 A case in which strong polar interactions between reinforcement and matrix has been reported is the (conventional) short-cut fiber composite system of poly(p-phenyleneterephthalamide)/poly(methyl methacrylate), [13][14][15] PPTA/PMMA. The interaction between the amide groups of PPTA and the polar carboxyl groups of PMMA was advanced in refs [13][14][15] as the cause of a new R′ relaxation process, which occurred after the main R relaxation of the matrix.…”

Section: Introductionmentioning

confidence: 99%

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PMMA/PPTA Microcomposites

et al. 1997

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Polymer composites of several concentrations of poly(methyl methacrylate) and poly(pphenyleneterephthalamide) microfibrils have been prepared by blending a solution of the matrix polymer and a suspension of microfibrils obtained from a solution of commercial Kevlar fiber in H2SO4. Scanning electron microscopy shows that a continuous network of fibrils with dimensions in the range 30-70 nm builds up starting at very low PPTA concentrations and that these fibrils tend to form larger globular aggregates at higher PPTA concentrations. The high connectivity of the network is reflected in the good reinforcing effect as shown by the values of the dynamic-mechanical storage modulus. Increased interaction between the constituent phases as the fiber content grows is revealed by an increase of the calorimetric glass transition temperature and by thermogravimetric analysis, as well as by the growth of the slope of the Arrhenius plot of the main relaxation. The induced modifications of the matrix polymer's dynamic-mechanical spectrum are discussed with the help of predictions of a modified block model. A consistent interpretation of the temperature shifts of the glass transition and the main dynamic-mechanical dispersion can be gained on this basis. The numerical values of the model parameters that fit the experimental behavior correlate well with the buildup of structure revealed in the micrographs.

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Molecular composites from sulfonated poly(p‐phenylene terephthalamide)

Cited by 12 publications

References 21 publications

Ionic poly(p‐phenylene terephthalamide)s: Preparation and characterization

Ionic poly(p‐phenylene terephthalamide)s: Preparation and characterization

Molecular Composites via Ionic Interactions and Their Deformation—Fracture Properties

PMMA/PPTA Microcomposites

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