摘要:

AbstractThe molecular weight averages of narrow and broad distribution commercial polyethylene oxide have been estimated by controlled precipitation from iso‐octane/benzene solutions by cooling from 333 to 273 K. Estimates of the distributions, which compared favourably with those determined by gel permeation chromatography (gpc), were obtained from a calibration procedure between the temperature of initial onset of precipitation and the viscosity average molecular weight.The chief advantages of this procedure were that it enabled molecular weight characteristics to be determined rapidly and with small amounts of materials when g.p.c. was not readily available. The method is used to assess various fractionation procedure

ISSN:0007-1641    

DOI:10.1002/pi.4980090102

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe glass transition temperatures (Tgs) of a series of poly N‐(n‐alkyl) maleimides covering only the even members with side chains ranging in length from ethyl to n‐octadecyl have been studied from room temperature to above Tg. Tgs and thermal quantities have been determined from the specific volume‐temperature relations only for the higher (n=8, 10, 12, 14, 16 and 18, where n = no of CH2) members of the series. However for the lower ones (n = 2, 4, 6, 8 and 10) Tgs have been detected from heat capacity‐temperature traces of differential scanning calorimetry diagrams by extrapolation to zero rate of heating. Accurate consistency was found in the values (n = 8 and 10) determined by both experimental methods.TgS of these polymers continuously decrease as the number of methylene groups in the side chain is increased, and they have been correlated with the size of the n‐alkyl group in the side chain. The results are in accord with a previously studied series concerning the effect of a long side chain on the Tgof a comb‐like polymer in the amorphous state.Tgs of poly N‐(n‐alkyl) maleimides encompassing a wide range of methylene group content (n = 2, 4, 6, 8, 10 and 12) have been examined according to the Gordon‐Taylor‐Wood extrapolation with the objective of ascertaining the Tgof polyethylene (PE). Our approach of ignoring higher members of the homologous series in this extrapolation appears to be old and well known and it has been variously ascribed to different authors. Extrapolation of Tgvalues to 100% amorphous PE gives a Tgof 200/pm 10 °K in complete agreement with recent predictions made by Boyer from different sources of data.The Simha‐Boyer free volume quantity Δa. Tgdecreases slowly with the methylene group content in the longer terms (n = 8, 10, 12, 14, 16 and 18) of the series presumably because of a reduction in the polarity or an in‐chain crankshaft loss mechanism which generates free volume in the glassy state, as stated by Boyer.Tgs do not correlate very well with the contributions of the atomic groups to the cohesive energy density (c.e.d.) so it can be concluded that c.e.d. is not the only factor determining Tg. However, a somewhat improved relationship might be obtained by taking into account the steric hindrance effect according t

ISSN:0007-1641    

DOI:10.1002/pi.4980090103

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractPhillips type Friedel—Crafts resins have been synthesised from biphenylVby reaction with dichloromethylbenzene III, Mark I resins, without the specific addition of catalysts. Mark II resins have been prepared from biphenyl andp‐xylylene glycol dimethyl etherIV, using stannic chloride as the Friedel‐Crafts catalyst. The structures of these two polymers are similar but have differences of detail. The structures have been established by using methods including elemental analysis, molecular weight determinations and infra‐red and n.m.r. spectra.Thermal degradation was studied using differential thermal analysis (d.t.a.) and stepwise and isothermal degradation procedures. The amount and composition of the volatile fraction were determined by mass spectroscopy. The fraction consisted of benzene, toluene and xylene together with traces of methane and, from the Mark II resin, methanol. The volatile product was a small fraction of the sample. The residue was the major part and was analysed by determination of its molecular weight and ultra‐violet and n.m.r. spectra. It was concluded that during thermal degradation the main reaction was intramolecular scission. Subsequent reactions led to the formation of substituted 9‐phenylfluorene units. These polymers had high thermal stability and degradation processes were very slow below

ISSN:0007-1641    

DOI:10.1002/pi.4980090104

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe homopolymerisation of 2‐furaldehyde, 5‐methyl‐2‐furaldehyde and 2‐furyl methyl ketone and their cationic copolymerisation (BF3. Et2) with olefins were investigated. All attempts to obtain homopolymers failed because of thermodynamic restrictions. 2‐Furaldehyde and α‐methylstyrene gave an alternating copolymer of low degree of polymerisation, 2‐methyl‐2‐furaldehyde and α‐methylstyrene gave copolymers rich in 5‐methyl‐2‐furaldehyde, indicating a penultimate effect in the growth mechanism. The use of less basic comonomers (cyclopentadiene, styrene, isoprene, etc.) resulted in inhibition or strong retardation of the polymerisation. The use of more basic comonomers (acenaphthy‐lene,N‐vinylcarbazole) resulted in their homopolymerisation. Furyl methyl ketone inhibited the polymerisation of all comonomers tried. A complex between BF3. Et2O and 2‐furaldehyde was isolated and characterised. A general mechanism is offered to exp

ISSN:0007-1641    

DOI:10.1002/pi.4980090105

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe environmental behaviour of carbon fibre composites is being investigated. Water pick‐up data obtained during these studies are analysed in an attempt to develop an understanding of the absorption mechanism.There is evidence which indicates that voids and defects in the composite have a marked effect on the absorption process and may assume greater significance than the diffusion process through the resin.Comments are made as to the possibility of the reversible behaviour of the composites on drying out being associated with hydrogen bonding phenomena. The need to know the size and location of voids is also stresse

ISSN:0007-1641    

DOI:10.1002/pi.4980090106

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIn fires, flexible polyurethane foams can decompose to give smokes which are subsequently degraded with the generation of hydrogen cyanide. In order to understand the general nature of this hazard it is first necessary to obtain information about the decomposition mechanism of the polyurethane foams and the structures of the intermediate smokes. The complexity of this problem has required the use of suitable model compounds.The preparation is described of (i) the four bis‐carbamates based on pure tolylene 2, 4‐diisocyanate and pure tolylene 2,6‐di‐isocyanate, each in combination with 2‐ethoxyethanol and with triethylene glycol monomethyl ether, and (ii) a urethane‐carbodi‐imide‐urethane and a urethane‐urea‐urethane based on pure tolylene 2,6‐di‐isocyanate and 2‐ethoxyethanol. All were decomposed by heating under nitrogen at temperatures near 300°C. The two di‐2‐ethoxyethyl bis‐carbamates (laandIIa) gave volatile monoisocyanate‐monourethanes and 2‐ethoxyethanol. The two di‐2‐[2‐(2‐methoxyethoxy)ethoxy] ethyl bis‐carbamates (IbandIIb) gave corresponding products and residue which contained carbodi‐imide functions. The urethane‐carbodi‐imide‐urethane (Va) gave a volatile urethane‐carbodi‐imide‐isocyanate (Via) and 2‐ethoxyethanol. The urethane‐urea‐urethane (VIIIa) decomposed through isocyanate‐ and carbodi‐imide‐containing materials to a volatile polymeric urea, which was obtained as a smoke and appeared to be virtually identical with the smoke obtained in earlier work from a commercial polyurethane. These results suggest that poly‐urethanes based on tolylene di‐isocyanate and polyether polyols decompose, when heated under nitrogen at 300°C, by cleavage of urethane groups to regenerate isocyanate groups and liberate alcohols. The isocyanato groups may react either with other isocyanato groups to give carbodi‐imides, which are then rapidly hydrated to ureas, or with water to give amines, which react with other isocyanato groups again to give ureas. Whether these processes occur separately or to

ISSN:0007-1641    

DOI:10.1002/pi.4980090107

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe magnitude of the thermal stresses generated among the polymeric constituents in highly grafted ABS‐samples during cooling down from the melt can be calculated by means of the ‘double emulsion model’. The effect of these stresses on the location of the rubber maximum in the loss modulusvstemperature plot can be derived from literature data regarding the pressure dependence of mechanical relaxation times.The results are in good agreement with those of torsion pendulum tests on a series of ABS‐samples prepared by blending a grafted rubber with various amounts of SAN‐resin. A continuous shift of the rubber loss peak to lower temperatures with decreasing rubber content is observed.Samples of low rubber content show a split damping peak at low temperatures. The area under the extra peak can be reversibly enlarged or reduced by varying the rate of cooling of the sample in the high temperature region, which indicates that real fracturing of graft molecules cannot be held responsible for this splitting of the peak.Especially at low rubber contents it has been found that the relative increase in rigidity with decreasing temperature is smaller in ABS‐resins than in the pure SAN‐copolymer. This decrease in relative modulus can also be correlated with the absolute value of the thermally induced hydros

ISSN:0007-1641    

DOI:10.1002/pi.4980090108

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe weight‐average molecular weight of a fraction of magnesium alginate was found by light‐scattering to be identical within experimental error to that of the corresponding fraction of sodium alginate. The difference in the charge density of sodium and magnesium alginate had no detectable effect on their measured radii of gyration at ionic strength 0.1, but had a great effect on the second virial coefficient of the solutions.The Orfino‐Flory theory was used to calculate expansion factors, α, from the second virial coefficients, assuming that these were composed of two terms, one due to polymer‐solvent interaction and one due to electrostatic interactions. A comparison with α‐values obtained from viscosity data at different ionic strengths suggested that alginate is soluble in water because of electrostatic stabilisation and not because of a favourable polymer‐wate

ISSN:0007-1641    

DOI:10.1002/pi.4980090109

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe possibilities and limitations of gel chromatography of non‐modified cellulose on inorganic supports in the complex solvent cadoxen are shown. The GPC fractionation in this system is possible but the evaluation of the analytical data would be rather complicated. The general problems of application of mixed eluents in gel chromatography are discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980090110

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe thermal degradation of polyepichlorhydrin and of the copolymer of epichlorhydrin with ethylene oxide, both in the uncompounded and compounded form, has been studied in air and inert atmosphere by thermogravimetry. A detailed examination has also been made of the evolution of hydrogen chloride from the homopolymer as a function of temperature and compounding formulation, specific attention being given to the efficiency of the acid acceptor. It is concluded that with suitable formulationohydrogen chloride evolution should not be a problem at temperatures at least up to 175°C

ISSN:0007-1641    

DOI:10.1002/pi.4980090111

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY