Industrial bag making machines are core processing equipment for customized packaging bags, covering diversified product specifications and serving a wide range of industries including food packaging, chemical raw material packaging, daily necessities and industrial packaging. In the actual production and processing process, heat sealing temperature is one of the most critical parameter indicators that directly determine the sealing quality, aesthetics and service life of finished bags. Many manufacturers have questions about the accurate heat sealing temperature setting of bag making machines. This article will sort out and analyze the key knowledge of bag machine heat sealing temperature in detail.

Most common industrial packaging bags on the market are made of PVC composite materials, and professional PVC bag making machines rely on precise heat sealing temperature control to complete the film bonding and sealing process. The core purpose of heat sealing temperature regulation is to heat the plastic film sealing layer to a stable viscous flow state, so that the film layers can be closely bonded after hot pressing and cooling, forming a firm sealing structure. In actual production, the heat sealing temperature cannot be set uniformly. Enterprises need to adjust parameters comprehensively according to the inherent characteristics of packaging materials, plastic film thickness, hot pressing cycle frequency of the sealing part and the actual size of the heat sealing area.

There is a flexible adjustment rule for production parameters: for the same sealing position of the packaging bag, if the equipment is set with multiple hot pressing cycles, the heat sealing temperature can be appropriately reduced to avoid excessive heating damage to the film; when the heat sealing area of the bag body increases synchronously, the heat sealing temperature needs to be moderately optimized and adjusted to ensure the uniformity of the sealing heating effect.

Different from crystalline plastic materials with fixed melting points, PVC materials used for packaging bags are typical amorphous polymers. They do not have a single fixed melting point, but present a continuous melting and softening temperature range. This temperature range is the key interval for PVC film to transition from solid state to molten viscous flow state. Among them, the minimum value of the temperature range is the viscous flow temperature of PVC materials, which is the starting point for film bonding and forming; the maximum value is the thermal decomposition temperature of PVC. The temperature difference between the two values directly determines the difficulty of bag making and heat sealing operation and the stability of finished product quality.

In the formal operation of the PVC bag making machine, the matching relationship between heat sealing temperature and sealing strength is the core of quality control. Within the reasonable temperature interval, the heat sealing strength of the packaging bag will be continuously improved with the increase of temperature, and the sealing will be tighter and more stable. However, the sealing strength has a fixed upper limit. After the temperature rises to the critical value of the material, the sealing performance will no longer be optimized even if the temperature is increased again.

It is worth noting that excessive heat sealing temperature is the main cause of defective packaging products. Ultra-high temperature will destroy the molecular structure of the plastic film at the sealing edge, resulting in sealing cracking, edge burning and other problems, which not only reduces the sealing fastness of the finished bag, but also greatly weakens the bag’s tensile resistance and impact resistance, easily causing leakage and damage during product transportation and storage. Therefore, the standard processing principle of bag making machines is to set the heat sealing temperature higher than the material’s viscous flow melting temperature, while strictly controlling the upper limit to avoid thermal decomposition of PVC materials, so as to ensure high-quality and high-yield production of packaging bags.