Mechanical denaturation of high polymers in solutions. XXXIX. Flow‐induced crystallization of high molecular weight syndiotactic‐rich poly(vinyl alcohol)

Yamaura, Kazuo; Daimoh, Motokazu; Tanigami, Tetsuya; Matsuzawa, Shuji

doi:10.1002/app.1988.070360719

J of Applied Polymer Sci

1988

DOI: 10.1002/app.1988.070360719

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Mechanical denaturation of high polymers in solutions. XXXIX. Flow‐induced crystallization of high molecular weight syndiotactic‐rich poly(vinyl alcohol)

Kazuo Yamaura

Motokazu Daimoh

Tetsuya Tanigami

et al.

Abstract: SynopsisThe crystallization of syndiotactic-rich poly(viny1 alcohol) (s-PVA) with a molecular weight of 6.73 X lo5 from aqueous solutions was carried out under Couette flow with or without seed crystals. The crystallization of s-PVA from aqueous solutions occurred below the surface of the solutions even in the presence of seed placed in the solution; whereas, in the case of aqueous s-PVA solutions containing 0.02% octyl alcohol (antifoaming reagent) only the longitudinal growth of seed occurred. The lengths of… Show more

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Cited by 4 publications

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“…4 This result coincide with the result of Yamaura et al . 5 They reported that syndiotacticity-rich PVA gives rise to fibrillation by shear-induced crystallization from aqueous solutions.…”

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confidence: 99%

Realtime Characterization of In Situ Molecular Alignment during the Saponification Process of Polyvinyl Pivalate

Kim

Lyoo

2000

Polym J

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The spontaneous fiber formation process during saponification ofpoly(vinyl pivalate) (PVPi) with syndiotactic diad content 63 to 65% to poly(vinyl alcohol) (PVA) in the presence of water was in situ examined. The variation of the revolution per minute(rpm) of a torque apparatus under a constant torque was measured for the spontaneous fibrillation system, and the actual fibrillation system was visualized in the realtime scale by in-line photographing. The in situ fibrillation mechanism was accounted for by relating the variation of the rpm with proceeding the saponification reaction to the change of solution morphology with saponification. At the constant torque level, the rpm changed with proceeding the saponification reaction in a complicated way. Up to the saponification time 80 s, the rpm was slightly increased with saponification, then decreased to the saponification time 400 s. From the saponification time 400 s, however, the rpm was abruptly increased. Then, the rpm was levelled off after the saponification time 700 s. Comparison of the rotational speed variation with the morphology change revealed that phase separation began from the degree of saponification 72.8%, and a clear fibrillar structure appeared from the degree of saponification 91.6%.

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“…4 This result coincide with the result of Yamaura et al . 5 They reported that syndiotacticity-rich PVA gives rise to fibrillation by shear-induced crystallization from aqueous solutions.…”

mentioning

confidence: 99%

Realtime Characterization of In Situ Molecular Alignment during the Saponification Process of Polyvinyl Pivalate

Kim

Lyoo

2000

Polym J

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Preparation of high modulus poly(vinyl alcohol) by drawing

Yamaura

Tanigami

Hayashi

et al. 1990

J of Applied Polymer Sci

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SynopsisThe preparation of PVA films and fibers with high modulus and high strength was examined. The high drawing was attained when both the drawing just before melting and the relaxation a t room temperature were repeated. The maximum draw ratio was 40 for the films prepared from the gels of high molecular weight (HMW) a-PVA ( D P = 12000)/water/dimethyl sulfoxide (DMSO) system (water/DMSO = 20/80). The degree of crystallinity of the dried gels prepared from the PVA/ethylene glycol (EG) system was high, 40-50%, and independent on the tacticity of PVA. The modulus of the fibers, prepared from the gels of HMW s-PVA ( D P = 15300)/EG system, drawn 15 times to its original length was the highest ( 120 GPa) .

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Properties of mixtures of silk fibroin/syndiotactic‐rich poly(vinyl alcohol)

Yamaura

Kuranuki

Suzuki

et al. 1990

J of Applied Polymer Sci

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SynopsisThe gelation of mixed solutions of silk fibroin (SF) /syndiotactic-rich poly (vinyl alcohol) ( s -PVA), the thermal analysis of dry-gels, and the various properties of blend films were investigated. The rate of gelation of a mixed solution was lower than that of each SF or s-PVA solution of the same concentration. In the DSC thermograph of mixed dry-gel (SF/s-PVA = 2 / 8 ~ 8 / 2 ) 2 endothermic peaks corresponding to SF (at 288-299°C: decomposition) and s-PVA (at 233-241°C: melting) were found. Namely, microphase segregation took place. This was confirmed by optical and electron microscopes. The mechanical properties of blend films did not have additive properties. The degree of swelling in water of blend films was independent on water temperature or methanol treatment. The mechanochemical behaviors were barely observed by the pH exchange between p H 2 and 12 only under lower loads. The addition of SF into s-PVA films promoted the permeation of neutral salts.

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Mechanical denaturation of high polymers in solutions. XXXIX. Flow‐induced crystallization of high molecular weight syndiotactic‐rich poly(vinyl alcohol)

Cited by 4 publications

References 22 publications

Realtime Characterization of In Situ Molecular Alignment during the Saponification Process of Polyvinyl Pivalate

Realtime Characterization of In Situ Molecular Alignment during the Saponification Process of Polyvinyl Pivalate

Preparation of high modulus poly(vinyl alcohol) by drawing

Properties of mixtures of silk fibroin/syndiotactic‐rich poly(vinyl alcohol)

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