Characterization of cellulose acetate phthalate (CAP)

Area of Science:

• Polymer science
• Materials science
• Pharmaceutical technology

Background:

• Cellulose acetate phthalate (CAP) is a widely used enteric coating polymer.
• Understanding CAP's characteristics is crucial for its functionality.
• Previous studies focused on free-acid content and substituent composition.

Purpose of the Study:

• To investigate the influence of storage conditions (temperature and humidity) on CAP functionality.
• To characterize molecular mass distribution and substituent patterns of CAP.
• To develop new methods for assessing CAP properties.

Main Methods:

• Fourier transform infrared spectroscopy (FTIR)
• Nuclear magnetic resonance (NMR) spectroscopy
• Thermal analysis (thermogravimetric analysis, differential scanning calorimetry)
• Molecular mass determination (mass-average molecular mass, number-average molecular mass)

Main Results:

• Humidity was found to be a more critical storage parameter than temperature for CAP functionality.
• Mass-average molecular mass of CAP batches ranged around 48 kg/mol with a polydispersity of 1.6.
• NMR successfully determined substituent fractions but not the substitution pattern.
• Glass transition temperature was less sensitive to substituent loss than molecular mass.

Conclusions:

• High humidity significantly degrades CAP functionality, impacting its use as an enteric coating.
• Molecular mass distribution is a key determinant of CAP functionality.
• New analytical methods provide valuable insights into CAP properties and degradation pathways.
• Further research may enable prediction of CAP properties based on substituent content and molecular weight.