Skip to main content
Login | Suomeksi | På svenska | In English

Browsing by Subject "grinding"

Sort by: Order: Results:

  • Pietarinen, Teemu (2012)
    Solid materials can exist in two major forms: in crystalline or amorphous form. Amorphous form is defined as no long term order existing in solid structure in molecular scale. Amorphous materials have different physicochemical properties compared crystalline forms of same substance. Amorphous materials doesn't have sharp melting point as crystalline materials. When heated above so called glass transition temperature amorphous materials become rubbery (plasticization) and when cooled below they become glassy (hard and brittle). Amorphous forms can also have different dissolution properties which makes them useful in formulation of poorly soluble drugs. Amorphous forms are less stable compared to crystalline form. That's due amount of free energy stored in it's structures. Amorphous materials can be manufactured in many ways including quench cooling, hot-melt-extrusion, spray drying and lyophilisation (freeze drying). In experimental section effect of grinding method in properties of amorphous indomethacin was studied. Amorphous indomethacin was prepared by quenching of melt in liquid nitrogen. Properties of amorphous indomethacin was studied by x-ray powder diffraction and differential scanning calorimetry. Measurements were performed in different time stamps varied form 0 to 92 days. Measured properties were crystalline content, glass transition temperature, change in heath capacity, heat of crystallization, heat of melting and melting points of crystallized forms. Calorimetry data was recorded only from totally amorphous samples. It can be seen in results that different patches are not comparable statistically but when comparing room temperature ground and liquid nitrogen ground samples to each other differences can be found in every set. Difference is observed in initial time of crystallization (time when crystallinity can be measured first time) and in thermodynamical properties such as change in heat capacity, glass transition temperature and heat of melting. Solid dispersions of indomethacin and xylitol were prepared in 3 different compositions (5%, 10% and 20% xylitol in indomethacin). XRPD and DSC data were measured at different time stamps (aged 1 to 63 days). 5% and 10% dispersions found to be stabile and being amorphous in all time stamps. 20% dispersion was already partly crystallized at 63 days (especially liquid nitrogen ground sample).