熱(re)封次數越(yue)多，熱(re)封強度越(yue)高，縱向熱(re)封次數取決于縱向焊棒(bang)的(de)有效長度和袋長之(zhi)比。
橫向熱(re)封(feng)(feng)次數由機臺橫向熱(re)封(feng)(feng)裝置的組數決(jue)定。良好的熱(re)封(feng)(feng)，要求熱(re)封(feng)(feng)次數至少(shao)達到兩次以上(shang)。相同結構和厚度(du)(du)的復合膜，復合層(ceng)間(jian)剝(bo)(bo)(bo)離(li)度(du)(du)越高，熱(re)封(feng)(feng)強(qiang)(qiang)度(du)(du)越大(da)；對于復合剝(bo)(bo)(bo)離(li)強(qiang)(qiang)度(du)(du)低(di)(di)的產(chan)品，焊縫破壞(huai)往(wang)往(wang)是焊縫處的復合膜先(xian)層(ceng)間(jian)剝(bo)(bo)(bo)離(li)，致使(shi)由內面(mian)熱(re)封(feng)(feng)層(ceng)獨立(li)承受破壞(huai)拉力(li)，而面(mian)層(ceng)材料失(shi)去補(bu)強(qiang)(qiang)作(zuo)用，致使(shi)焊縫的熱(re)封(feng)(feng)強(qiang)(qiang)度(du)(du)由此大(da)為降低(di)(di)；若復合層(ceng)間(jian)剝(bo)(bo)(bo)離(li)度(du)(du)強(qiang)(qiang)，則不(bu)致發生焊邊處層(ceng)問的剝(bo)(bo)(bo)離(li)，所測得(de)的實際熱(re)封(feng)(feng)強(qiang)(qiang)度(du)(du)就(jiu)人得(de)多(duo)；在熱(re)封(feng)(feng)內層(ceng)為PE或OPP時(shi)，熱(re)封(feng)(feng)強(qiang)(qiang)度(du)(du)就(jiu)比同樣厚度(du)(du)的BOPP好得(de)多(duo)。