摘要:

AbstractThe evolution of hydrogen fluoride from a vinylidene fluoride/hexafluoro‐propene/tetrafluoroethylene elastomer has been studied over the temperature range 200–275 °C in air. The rate of evolution is affected by the diamine curing agent, the carbon black filler and the acid acceptor used and their effects are interrelated. The acid acceptor also influences the crosslink density attained in the curing process. It was found that some metallic hydroxides and carbonates, in whose presence an acceptable level of crosslinking was achieved, were some 50 to 100 times more efficient than the magnesium oxide normally used in reducing the rate of hydrogen fluoride evolu

ISSN:0007-1641    

DOI:10.1002/pi.4980060302

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe composition and setting reaction of cements formed from aluminosilicates and poly(acrylic acid), the ASPA cements, are described. Setting and hardening results from interactions between specially‐formulated, complex, fluorine‐containing calcium aluminosilicate glasses and aqueous solution of poly(acrylic acid) or similar poly(alkenyl carboxylic acids). Protons from the polyacid penetrate the surface of the glass decomposing the negatively charged aluminosilicate network to a siliceous hydrogel and releasing Al3+, Ca2+and F‐ ions. These ions migrate, probably as complexes, such as AlF2+, AlF2+and CaF+, into the polyelectrolyte phase where they cross‐link polyanionic chains, by ionic and possibly chelate binding, causing the cement to gel and set. Overall the reaction may be seen as one where flexible hydrogen bonds, in the liquid, are progressively replaced by more rigid ionic ones, leading to gelation.The set cement is a composite of glass particles sheathed by a silica gel bound by a metal poly anionic matrix. ASPA cements can attain a compressive strength of 200 N/mm2in 24 h and are adhesive under oral conditions to tooth materials. They find a number of applications in conservative and preventive dentistry.Certain naturally‐occurring aluminosilicate minerals react with poly(acrylic acid) to form cement but these are much weaker (not exceeding a compressive strength of 30 N/mm2) and are weakened

ISSN:0007-1641    

DOI:10.1002/pi.4980060303

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractA description is given of the design, construction and application of a 0–2000 rev/min centrifuge for studying liquid‐liquid phase separations in macromolecular systems at temperatures of 0–200 °C. The concentrations in the phase can be measured with the aid of the complete optical schlieren system of the Model‐E Spinco‐Ultracentrifuge.Owing to the low rotational speed, sedimentation‐velocity and sedimentation‐diffusion equilibrium measurements can be carried out also in solutions containing macromolecules of very high mo

ISSN:0007-1641    

DOI:10.1002/pi.4980060304

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060305

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060306

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980060301

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY