摘要:

AbstractThe following is an extended abstract of a paper presented at the conference on Liquid Crystalline Polymers in Leeds, 1980, summarising the principles of the synthesis of thermotropic liquid crystalline polymers, their structure dependant phase behaviour and their orientation in electric and magnetic fields.

ISSN:0007-1641    

DOI:10.1002/pi.4980130202

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractInvestigations on dilute and concentrated solutions of several rodlike polymers are described. The former includes absolute and intensity fluctuation light scattering, exclusion chromatography and viscometry. The latter includes rheological properties of isotropic and anisotropic solutions. The discussion includes data for four rodlike polymers, each soluble only in strong sulphonic acids. The role of electrostic interactions and molecular association on the properties measured is considered. The similarities and differences of the rheological behaviour with that typically found with flexible chain polymers are pointed out.

ISSN:0007-1641    

DOI:10.1002/pi.4980130203

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA new series of aromatic‐aliphatic polyesters of general structure:R1= terphenyl, biphenyl, stilbeneR2= (CH2)n;  CH2C(Me)2CH2;CH2;C(Et)2CH2; (CH2CH2O)nCH2CH2 has been synthesised. The existence of thermotrpic liquid crystalline phases has been shown by polarised light microscopy. The texture observations have suggested the existence of nematic,SAor/andSCphases depending on the chemical structure. The temperature of transition between the phases and, as a consequence, the range of mesomorphism are highly dependent upon the chemical structure. The clearing point is high, even for the longest aliphatic group, while the m

ISSN:0007-1641    

DOI:10.1002/pi.4980130204

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980130205

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe hydration of chemical species formed in the cement‐forming reaction has been studied by measuring the evaporable, and non‐evaporable water contents of a glassionomer cement at various stages in its history. Hydration is accompanied by increase in strength and, as loose water is removed from the matrix, a decrease in plasticity. Hydration is attributed to ionisation of the polymeric carboxylic acid and transfer of metal ions from the glass to the polyelectrol

ISSN:0007-1641    

DOI:10.1002/pi.4980130206

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractXanthan gum, the extracellular polysaccharide fromXanthomonas comperstris, provides aqueous solutions with properties that are extremely useful in a large number of industrial applications, both food and non‐food. These properties, a consequence of xanthan gum's particular molecular shape, are: high at‐rest or low‐shear viscosity even at low gum concentrations, yield value, high pseudoplasticity, increased viscosity in the presence of added salt depending on gum concentration, stable viscosity over a wide range of temperature and pH in the presence of added salt, synergistic increase in viscosity in the presence of guar gum and locust bean gum, thermoreversible gelation with locust bean gum at appropriate gum concentratins, and gelation with di‐and trivalent metal ions and borates under specific conditions. Xanthan gum is thus an excellent stabiliser for a wide variety of suspensions, emulsions, and foams and is highly effective over a range of temperature, pH and ionic strength. In addition, its pseudoplasticity allows the formulation of products which require not only high at‐rest viscosity but also low viscosity under highshear application c

ISSN:0007-1641    

DOI:10.1002/pi.4980130207

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA parametric study of the molecular weight distribution and its moments has been made on the irreversible condensation polymerisation of ARB type monomers which do not obey the equal reactivity hypothesis. The reactions are simulated for a continuous‐flow stirred‐tank reactor with distributed residence times, the mean residence time being the operating variable. Two different kinetic schemes have been proposed which represent the limiting cases of the actual situations (models I and II) which are usually encountered and the effect of segration in a CSTR has been studied. The molecular weight distributions, number average chain lengths and the polydispersity indices have been computed. Results are found to lie intermediate between batch reactors and homogeneous, continuous‐flow stirred tank reactors. Plots between the poly dispersity index and the monomer conversion with the reactivity ratio,R, and the number average chain length as parameters indicate that results are far more sensitive to variations inRfor model II than for mo

ISSN:0007-1641    

DOI:10.1002/pi.4980130208

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA microfiltration technique for cleaning polymer latices is evaluated. The modified millipore microfiltration cell employed is described and optimum operating conditions given: the cell consists of a 47 mm diameter millipore filter supported on a stainless steel mesh and contained within a PTFE body. Double distilled water is pumped through the cell, removing impurities from the latex. The latex particles are retained by the filter: pore blockage is prevented by PTFE coated magnetic stirrer bar. The nature and location (water or polymer phases) of the major impurities encountered with polystyrene latices are identified. The efficiency with which microfiltration removes these impurities is compared with dialysis and ion exchange. Monomer, low molecular weight oligomer, benzaldehyde, and surface active agent are completely removed. However, electrolytic material associated with the polymer phase is not completely removed by this technique. Microfiltration may also be used to concentrate a latex and separate latex particles of different sizes.

ISSN:0007-1641    

DOI:10.1002/pi.4980130209

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980130210

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980130211

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY