Determination of the Fiber Content of Composite Materials by Thermogravimetry - METTLER TOLEDO

Determination of the Fiber Content of Composite Materials by Thermogravimetry

Introduction 

Plastics are frequently filled or reinforced with very different types of material in order to improve their mechanical and thermal properties. Organic fillers and reinforcing materials (e.g. wood flour) increase the toughness of a plastic. The addition of fibers can result in a major increase in stiffness and structural strength. Besides natural organic fibers such as jute and sisal, synthetic inorganic fibers (e.g. glass and carbon fibers) and organic fibers such as aramid are widely used for reinforcement purposes. Aramid fibers consist of poly-p-phenylene terephthalamide and are remarkable because of their high tensile strength and their relatively high decomposition temperature of about 550 °C.

Fiberglass-reinforced thermoplastics are being increasingly used for technical products: they can be processed by injection molding or extrusion and exhibit excellent mechanical properties.

This allows them to be used in very diverse fields (car manufacturing, precision machines, electrical engineering etc.). Some examples of products reinforced with aramid fibers are high pressure flexible hoses, belts and bulletproof jackets.

The quality assurance of such composite materials consists primarily of checking the desired fiber content. This is very easily done using thermogravimetry, as will be shown in the following two examples.

Thermogravimetry (TG) or thermogravimetric analysis (TGA) measures the mass of a sample that is heated at a constant rate (usually linear) in a controlled atmosphere. The examples described here deal with the loss of mass resulting from the pyrolytic decomposition of the plastics under nitrogen.

Example 1: Fiberglass-reinforced polyamide PA 6 Samples of about 11 mg each of PA 6 (without fiberglass) and fiberglass-reinforced PA 6 were examined by TGA under the following experimental conditions:


Conclusions

These examples show that thermogravimetry is an excellent method for the rapid and accurate determination of the resin and fiber content in composite materials. The decomposition temperatures provide additional qualitative information concerning the identity of the components.

Determination of the fiber content of composite materials by thermogravimetry | Thermal Analysis Application No. UC 132 |  Application published in METTLER TOLEDO Thermal Analysis UserCom 13