熱(re)封次(ci)數越多(duo)，熱(re)封強度越高，縱向熱(re)封次(ci)數取決于(yu)縱向焊棒的有(you)效長度和袋長之比。
橫向(xiang)熱(re)(re)封(feng)(feng)次數由機臺橫向(xiang)熱(re)(re)封(feng)(feng)裝置的組(zu)數決定。良(liang)好的熱(re)(re)封(feng)(feng)，要求熱(re)(re)封(feng)(feng)次數至少達到兩次以上。相同結(jie)構和厚(hou)度(du)(du)的復合膜(mo)，復合層(ceng)間(jian)(jian)剝離(li)度(du)(du)越高(gao)，熱(re)(re)封(feng)(feng)強度(du)(du)越大(da)；對于(yu)復合剝離(li)強度(du)(du)低(di)的產品，焊(han)縫破(po)(po)壞往往是焊(han)縫處(chu)的復合膜(mo)先層(ceng)間(jian)(jian)剝離(li)，致(zhi)(zhi)使(shi)由內面熱(re)(re)封(feng)(feng)層(ceng)獨立(li)承(cheng)受破(po)(po)壞拉力，而面層(ceng)材料失去補強作(zuo)用，致(zhi)(zhi)使(shi)焊(han)縫的熱(re)(re)封(feng)(feng)強度(du)(du)由此(ci)大(da)為(wei)降低(di)；若(ruo)復合層(ceng)間(jian)(jian)剝離(li)度(du)(du)強，則不致(zhi)(zhi)發生焊(han)邊處(chu)層(ceng)問的剝離(li)，所測得(de)的實際熱(re)(re)封(feng)(feng)強度(du)(du)就人得(de)多(duo)；在熱(re)(re)封(feng)(feng)內層(ceng)為(wei)PE或OPP時，熱(re)(re)封(feng)(feng)強度(du)(du)就比同樣厚(hou)度(du)(du)的BOPP好得(de)多(duo)。