Heat seating measurement by an innovative technique

To obtain a proper heat seal is an important requirement in packaging, since seal failure is a more frequent cause of product deterioration than the package itself. Different kinds of seal, such as peelable or non-peelable, can be obtained by changing the conditions under which a material is sealed. Therefore, identifying these conditions is very important. A new technique, the method for measuring temperature of melting surface (MTMS), was used to predict the strongest peelable seal on various packaging commercial films. The temperature of the seal interface was measured using a thermocouple. The time-temperature profile, which was obtained by means of a thermocouple, was electronically processed so as to obtain the derivatives of the profile. The inflection point, also called the fusion point, was located on these profiles. This inflection point is associated with the physical change of the state of the material being sealed. The inflection point analysis was done using two different methods: (a) the MTMS method, based on the second derivative of temperature data with time; (b) 'Table Curve' software, based on nonlinear regression. This technique was successfully used to evaluate widely used packaging films such as LDPE, HDPE, LLDPE and CPP. The inflection point for these films was identified and the seal strength was verified using a universal testing machine. This method appears to be applicable to design the strongest peelable heat seals for many packaging materials. It also seems to have promise as a method of process measurement and validation for heat seal processes. Copyright (c) 2006 John Wiley & Sons, Ltd.