Sealing temperature has a direct effect on the heat seal strength. The melting temperature of a variety of materials, directly determine the composite minimum heat seal temperature. In the production process, due to heat stress, bag-making speed and the thickness of the substrate, and many other effects used heat sealing temperatures tend to be higher than the melting temperature of sealing material. Heat sealing with less stress, hot temperature higher speed faster, composite membrane surface in thicker materials requiring higher the sealing temperature. Heat seal temperature if below the softening point of sealing material, regardless of how to increase the pressure or extended heat sealing time is unlikely to make heat seal layer true seals. But if the heat seal temperature is too high, and extremely easy to damage sealing material welding melt, producing "undercut" phenomenon, greatly reduce the heat seal strength and sealing bag impact resistance.