Identification of Polymer Blends by Glass Transition Measurements

The use of polymer blends for industrial applications has become more prevalent over the past few decades. A considerable amount of research has been recently conducted to obtain new polymeric materials with enhanced attributes for specific applications or a better combination of different properties.

Online PR News – 21-July-2010 – – When developing suitable polymer blends it is important to consider a number of different research, development and quality control issues. One of the most important issues is blend compatibility. Compatible polymer blends can avoid undesirable physical and chemical effects such as:
• premature aging
• cracking and tearing
• abrasion
• break down or disintegration
• impermeability to natural elements
• chemical attack
Differential scanning calorimetry (DSC) is a valuable thermal analysis technique which provides testing laboratories with important information on the glass transition of polymer blends. Measuring the glass transition of the desired polymer blends can quickly and easily determine their compatibility.

Analyzing Compatible Polymer

The examples described below show how the DSC 1 was used to measure the glass transition of two different polymer blends.
The samples were first cooled from 120°C to -140°C at 5K/min and then measured by heating from -140°C to 100°C at 10 K/min in a nitrogen atmosphere at 50ml/min to determine the temperature at which the glass transition occurs. The DSC curves were then evaluated using the STARe software to investigate the compatibility of the blends.
The glass transition in Figure 1 is relatively broad and extends over a temperature range of 60K between -110°C and -50°C. The occurrence of just one glass transition in the polymer blend shows the polymer components are compatible.
The DSC curve displayed in Figure 2 shows that two glass transitions are present. The glass transition of NR occurs at -58.8°C, while the glass transition of SBR occurs at -44.1°C indicating that the polymers used in the polymer blend are incompatible.
The above DSC results show that only one glass transition is observed with compatible polymer blends. Incompatible polymer blends demonstrate that the polymer phases are separated as each polymer phase exhibits its own glass transition. The DSC curves can provide testing laboratories with valuable information on the glass transition of polymers when determining the compatibility of polymeric blends. The DSC 1 is an excellent tool which delivers fast and accurate results
over a wide temperature range. It also has the added benefit of an optional sample robot, which enables fully automated
measurements to be carried out.