ISSN:
0098-1273
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Crystals of fractionated trans-1,4-polyisoprene (TPI) were grown from amyl acetate solution at two weight fractions, 5.7 × 10-4 and 0.011; for the lower concentration a precooling followed by heating and then crystallization at temperatures in the 10-32°C range was used, while for the higher concentration this method and direct crystallization at a temperature TC in the 0-32°C range were employed. The precooling method yielded samples crystallized in the α form, while direct crystallization led to formation of β-TPI at low TC and α at higher TC. The value for the DSC endotherm, characteristic of α-form melting, increased with increasing TC, with a shift to lower values with increasing concentration for precooled samples. A β to α transformation was found to occur for synthetic unfractionated TPI when swollen with amyl acetate at 35°C for 17h. Swelling in n-butyl acetate for one day at 25°C or 17 h at 35°C also led to this transformation. From experimental results 74°C is chosen as the temperature at which the α and β forms coexist in the bulk, and this is used to calculate the enthalpy of fusion of β-TPI, yielding a value of 8.6 kJ mol-1.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1982.180200916
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