The effect of molecular weight on the rheological and tensile properties of poly(ϵ-caprolactone)

• Published in: International journal of pharmaceutics Vol. 135; no. 1; pp. 103 - 109
• Main Authors: Grosvenor, M.P., Staniforth, J.N.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 17.06.1996; Elsevier
• Subjects: Biological and medical sciences; Film formation; General pharmacology; Medical sciences; Melt viscosity; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Poly(ϵ-caprolactone); Polymer molecular weight; Rheology; Tensile properties; Polymer molecular weight; Film formation; Melt viscosity; Poly(ϵ-caprolactone); Rheology; Tensile properties; Viscosity; Caprolactone copolymer; Pharmaceutical technology; Fluidity; Biodegradability; Ester polymer; Tensile property; Drug adjuvant; Molecular weight property relation; Rheological properties
• ISSN: 0378-5173; 1873-3476
• DOI: 10.1016/0378-5173(95)04404-3

Molecular weight fractions of poly(ε-caprolactone) (PCL) were obtained by catalytic degradation and characterised by theological measurements. Pseudoplastic behaviour was found in the higher molecular weight fractions, the degree of which lessened as the thermal motion of the polymer chains increased. The exponential factor of the viscosity/ molecular weight relationship indicated that the fractions were above the critical molecular weight for viscous flow determined as 15–16 000. Activation energies for viscous flow showed an inverse relationship with molecular weight, the significance of which has been discussed. Melt quenching resulted in lower melt viscosities due to a reduction in melting point by formation of additional amorphous regions. Tensile measurements indicated that PCL was a brittle material with a molecular weight of > 16 900 being required for free film formation. Elongation and tensile strength values increased with molecular weight although remaining low, indicating both the low molecular weight range investigated and the high degree of PCL crystallinity. PCL showed that it had rheological and tensile properties that with modification would make it a potential candidate in the novel technique of powder coating of pharmaceutical compacts.