Engineering | Open Access Articles | Digital Commons Network™

Thermal Degradation Of Segmented Polyurethanes, William Macknight, Zoran S. Petrovic, Zoltan Zavargo, Joseph H. Flynn

William MacKnight

Thermal degradation of polyurethane samples was studied by a thermogravimetric method. The effect of soft-segment length and soft-segment concentration on activation energy of the degradation process was measured. Three methods of calculation gave activation energies at different stages of the very complex weight loss process. It was shown that at initial stages of the weight loss the process was dominated by hard-segment degradation. Activation energy of the whole process calculated by the Ozawa-Flynn method did not offer clear insight into the structure-stability relationship of polyurethanes. The second method showed that activation energy of the initial stage of degradation increased with …

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Thermal, Dielectric, And Mechanical Relaxation In Poly(Benzimidazole)/Poly(Etherimide) Blends, William Macknight, Kuiming Liang, Gyorgy Banhegyi, F. E. Karasz

William MacKnight

Thermal, dielectric, and mechanical relaxation measurements on miscible blends of poly-

benzimidazole(PBI)and a polyetherimide (PEI, Ultem 1000)prepared by solution casting

from dimethylacetamide (DMAc) reveal a number of structurally related features. Annealing

below the glass transition temperature induces an enthalpy relaxation process typical of

single-phase glasses of nonequilibrium structure. Dielectric relaxation experiments on

samples annealed at ambient conditions reveal two relaxation processes below 400°C.At

lower temperatures (50-2OO0C), the desorption of water is observed. Above 200°C in the

first run, a composition-dependent relaxation is seen at the highest frequencies ( 100 kHz)

while a relaxation approximately independent of composition appears in the …

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Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor

William MacKnight

A novel liquid-crystalline polyurethane (LCPU) was synthesized by the condensation of

2,4-toluenediisocyanate and 4,4'-bis(6-hydroxyhexoxy)biphenyl. Solution polymerization in dimethylformamide

produced intrinsic viscosities in the range 0.30-0.57 dL/g. Differential scanning calorimetry shows a crystalline

melting transition that is highly dependent on molecular weight and thermal history and a clearing transition

that is virtually independent of both. Parallel-plate rheometry results are consistent with the presence of

a liquid-crystalline phase, coexisting with a small amount of three-dimensional crystallinity, between 152 and

166 °C. Dynamic mechanical measurements reveal an unusually high elastic modulus of 180 MPa in the plateau

Thermal Degradation Of Segmented Polyurethanes, William Macknight, Zoran S. Petrovic, Zoltan Zavargo, Joseph H. Flynn

William MacKnight

Thermal, Dielectric, And Mechanical Relaxation In Poly(Benzimidazole)/Poly(Etherimide) Blends, William Macknight, Kuiming Liang, Gyorgy Banhegyi, F. E. Karasz

William MacKnight

Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor

William MacKnight

Thermal And Mechanical Properties Of Linear Segmented Polyurethanes With Butadiene Soft Segments, William Macknight, C. M. Brunette, S. L. Hsu, M. Rossman, N. S. Schneider

William MacKnight

Mechanical And Thermal Properties Of Aromatic Copolyesters Containing Rigid Binaphthyl Units, William Macknight, J. Manusz, R. W. Lenz

William MacKnight

Thermal, Dynamic Mechanical, And Dielectric Properties Of Hydrogenated, Sulfonated Polypentenamers, William Macknight, D. Rahrig

William MacKnight

Thermal And Dynamic Mechanical Properties Of Sulfonated Polypentenamers, William Macknight, D. Rahrig

William MacKnight

Properties Of Polyethylene Modified With Phosphonate Side Groups. I. Thermal And Mechanical Properties.Pdf, William Macknight, R. A. Weiss, R. W. Lenz

William MacKnight

The Hydrogenation Of A Polypentenamer And Thermal Properties Of The Resulting Products, William Macknight, K. Sanui, R. W. Lenz

William MacKnight

Mechanical And Thermal Properties Of Phosphorylated Polyethylene, William Macknight, P. J. Phillips

William MacKnight