熱封(feng)次數越多，熱封(feng)強度(du)越高(gao)，縱向熱封(feng)次數取(qu)決于縱向焊棒的有效長度(du)和袋長之比。
橫向熱(re)(re)封(feng)(feng)(feng)次(ci)數由(you)機臺橫向熱(re)(re)封(feng)(feng)(feng)裝置的(de)(de)組數決(jue)定。良好的(de)(de)熱(re)(re)封(feng)(feng)(feng)，要求熱(re)(re)封(feng)(feng)(feng)次(ci)數至少達(da)到兩次(ci)以上(shang)。相同(tong)結(jie)構和厚度(du)(du)(du)的(de)(de)復(fu)合膜，復(fu)合層(ceng)(ceng)(ceng)間(jian)(jian)剝(bo)離度(du)(du)(du)越高，熱(re)(re)封(feng)(feng)(feng)強度(du)(du)(du)越大；對于復(fu)合剝(bo)離強度(du)(du)(du)低的(de)(de)產品，焊縫破壞(huai)往(wang)往(wang)是焊縫處的(de)(de)復(fu)合膜先層(ceng)(ceng)(ceng)間(jian)(jian)剝(bo)離，致使由(you)內面(mian)熱(re)(re)封(feng)(feng)(feng)層(ceng)(ceng)(ceng)獨立承受破壞(huai)拉力(li)，而面(mian)層(ceng)(ceng)(ceng)材料失去補強作用，致使焊縫的(de)(de)熱(re)(re)封(feng)(feng)(feng)強度(du)(du)(du)由(you)此大為(wei)(wei)降低；若(ruo)復(fu)合層(ceng)(ceng)(ceng)間(jian)(jian)剝(bo)離度(du)(du)(du)強，則不致發生焊邊處層(ceng)(ceng)(ceng)問的(de)(de)剝(bo)離，所測(ce)得的(de)(de)實際熱(re)(re)封(feng)(feng)(feng)強度(du)(du)(du)就人得多；在(zai)熱(re)(re)封(feng)(feng)(feng)內層(ceng)(ceng)(ceng)為(wei)(wei)PE或(huo)OPP時，熱(re)(re)封(feng)(feng)(feng)強度(du)(du)(du)就比同(tong)樣厚度(du)(du)(du)的(de)(de)BOPP好得多。