Process and control today | Choosing the optimal thermal fluid for plastic molding

Plastic can be used to make products for almost any industry, from packaging to aerospace. Manufacturers can use different methods to make and shape these products, but there will always be one constant – heat. If the heating solution is not efficient, productivity and quality suffer. Here, Clive Jones, managing director of thermal fluid specialist Global Heat Transfer, explains the benefits of using heat transfer fluids in plastic molding applications and examines the factors to consider when choosing a thermal fluid.

Electric heaters are commonly used in a variety of plastics manufacturing applications such as injection molding, extrusion molding, or rotational molding. These tubular heaters provide quick and accurate heating to increase the efficiency of melting materials.

While electric heaters are a popular method of heating plastics, they do not always provide the user with enough precision to ensure product quality. Alternatively, thermal liquids offer advantages over this heating technology, as they are even more precise in order to guarantee product quality. Engineers can use thermal fluids to heat a range of equipment in molding processes such as reservoirs, molding machines, and extruders to precise temperatures by circulating heat transfer fluids at a controlled rate.

Choose a liquid

Adapting the thermal fluid to the system and the operating temperature of the application can help extend the life of the fluid. For example, molding processes require heat transfer oil with a wide temperature range to ensure effective heat transfer and maximum efficiency throughout production.

The chemical composition of the liquid also affects its suitability for the application. For example, Globaltherm® Syntec is a superior synthetic heat transfer fluid designed for liquid phase heat transfer. It has low vapor pressure, high conductivity and oxidation stability to better resist thermal degradation at higher temperatures. Alternatively, Globaltherm® HF is an energy-efficient oil that was developed for heating and cooling processes with only one liquid. It contains a resilient blend of additives to ensure trouble-free operation when properly managed, and has one of the highest flash points in the industry at 276 ° C for efficient heat transfer at very high temperatures.

Extension of the service life of liquids

Selecting a heat transfer fluid with a broad operating temperature so that it can be used for multiple processes can reduce operating costs, but only if the fluid is properly maintained. If the thermal fluid is left unattended for a long time, the degradation can go unnoticed until it affects production. The breakdown process can lead to the formation of carbon, a natural insulator, that builds up in the system. This can lead to a lack of flow or the formation of hotspots, which can prevent the system from reaching and maintaining the required temperatures – leading to quality problems with plastic products. At this point, manufacturers must take a live, hot circulating sample and analyze the condition of the liquid during operation. Fluid analysis can show that production needs to be stopped in order to drain, flush, and refill the system, resulting in costly downtime.

Regular thermal fluid analyzes can slow down the degradation process and reduce the risk of inexplicable productivity losses. Quarterly liquid sampling from hot and circulating heat transfer systems gives manufacturers an accurate representation of the condition of the liquid. By tracking the analysis of each sample to look for trends, manufacturers can understand what is happening in the system and take action before the deterioration affects production.

According to the World Economic Forum, the global plastics industry produced 311 million tons of plastic in 2014, and that number is likely to have doubled by 2034. This expansive industry relies on heat to effectively melt, shape, and prepare plastics. Selecting the optimal heat transfer fluid for the required operating temperatures and measures to extend the life of the fluid can help manufacturers make effective use of this resource.

For information on selecting the correct heat transfer oil for plastic molding applications, contact Global Heat Transfer at or call 01785 760 555.

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