熱封次數越多，熱封強度(du)越高，縱向熱封次數取決于縱向焊(han)棒的有效長度(du)和袋(dai)長之比。
橫向熱(re)(re)封(feng)(feng)(feng)次(ci)數由機(ji)臺橫向熱(re)(re)封(feng)(feng)(feng)裝置的組(zu)數決定。良好的熱(re)(re)封(feng)(feng)(feng)，要求熱(re)(re)封(feng)(feng)(feng)次(ci)數至少達到兩(liang)次(ci)以上。相同結構和厚(hou)度的復合膜(mo)，復合層(ceng)間(jian)剝(bo)離(li)(li)度越高，熱(re)(re)封(feng)(feng)(feng)強(qiang)(qiang)(qiang)度越大；對于(yu)復合剝(bo)離(li)(li)強(qiang)(qiang)(qiang)度低(di)的產(chan)品，焊(han)(han)縫破壞往(wang)往(wang)是焊(han)(han)縫處的復合膜(mo)先層(ceng)間(jian)剝(bo)離(li)(li)，致(zhi)使由內(nei)面(mian)熱(re)(re)封(feng)(feng)(feng)層(ceng)獨立承受(shou)破壞拉力，而(er)面(mian)層(ceng)材料失(shi)去補強(qiang)(qiang)(qiang)作(zuo)用，致(zhi)使焊(han)(han)縫的熱(re)(re)封(feng)(feng)(feng)強(qiang)(qiang)(qiang)度由此(ci)大為降(jiang)低(di)；若復合層(ceng)間(jian)剝(bo)離(li)(li)度強(qiang)(qiang)(qiang)，則不致(zhi)發生焊(han)(han)邊處層(ceng)問的剝(bo)離(li)(li)，所測得的實(shi)際熱(re)(re)封(feng)(feng)(feng)強(qiang)(qiang)(qiang)度就人得多；在熱(re)(re)封(feng)(feng)(feng)內(nei)層(ceng)為PE或OPP時(shi)，熱(re)(re)封(feng)(feng)(feng)強(qiang)(qiang)(qiang)度就比同樣厚(hou)度的BOPP好得多。