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Determination of Melting Point of PEG 1500 by Capillary Method (CAT#: STEM-PPA-0044-YJL)

Introduction

Polyethylenglycols (PEGs) are water-soluble polymers with general formula HOCH2(CH2OCH2)nCH2OH where n is the degree of polymerization and represents the number of oxyethylene groups in the polymer. PEGs with molar mass up to 600 Da are liquid at ambient temperature, while those with molar mass higher than 1000 Da are solid.
PEGs are widely used in the mechanical as well as in the pharmaceutical and cosmetic industries. Due to suitable physico-chemical properties, PEGs are used as lubricant fluid in compressors as well as absorbents in gas cleaning. Their good biocompatibility is exploited for preparing cosmetic and pharmaceutical products.




Principle

Melting point is a characteristic property of solid crystalline substance. It is the temperature at which the solid phase changes to the liquid phase. This phenomenon occurs when the substance is heated.
The melting point measurement is usually performed in thin glass capillary tubes with an internal diameter of 1 mm and a wall thickness of 0.1 – 0.2 mm. A finely-ground sample is placed in the capillary tube to a filling level of 2 – 3 mm and introduced in a heated stand (liquid bath or metal block) in close proximity to a high accuracy thermometer. The temperature in the heating stand is ramped at a user-programmable fixed rate. The melting process is visually inspected to determine the melting point of the sample.

Applications

Chemical industry; Cosmetic/pharmaceutical industry

Procedure

1. Seal capillary.
2. Fill the sample.
3. Install the instrument.
4. Determine the melting point.

Materials

• Sample Type: crystalline compounds
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