熱(re)封(feng)(feng)次數(shu)越多，熱(re)封(feng)(feng)強度(du)越高，縱向熱(re)封(feng)(feng)次數(shu)取決于縱向焊(han)棒(bang)的有效長(chang)度(du)和(he)袋長(chang)之比。
橫向熱(re)(re)封(feng)次數(shu)由機臺(tai)橫向熱(re)(re)封(feng)裝置的組數(shu)決定。良好的熱(re)(re)封(feng)，要求熱(re)(re)封(feng)次數(shu)至少達(da)到兩次以上。相(xiang)同(tong)結(jie)構和厚(hou)度(du)的復合(he)膜，復合(he)層(ceng)間(jian)剝(bo)(bo)離度(du)越(yue)高，熱(re)(re)封(feng)強(qiang)(qiang)(qiang)(qiang)度(du)越(yue)大；對于復合(he)剝(bo)(bo)離強(qiang)(qiang)(qiang)(qiang)度(du)低(di)的產品，焊(han)縫破壞(huai)往(wang)往(wang)是(shi)焊(han)縫處的復合(he)膜先層(ceng)間(jian)剝(bo)(bo)離，致使(shi)由內面(mian)熱(re)(re)封(feng)層(ceng)獨立承(cheng)受破壞(huai)拉力，而(er)面(mian)層(ceng)材料失去補(bu)強(qiang)(qiang)(qiang)(qiang)作用，致使(shi)焊(han)縫的熱(re)(re)封(feng)強(qiang)(qiang)(qiang)(qiang)度(du)由此大為降(jiang)低(di)；若復合(he)層(ceng)間(jian)剝(bo)(bo)離度(du)強(qiang)(qiang)(qiang)(qiang)，則(ze)不致發生焊(han)邊(bian)處層(ceng)問的剝(bo)(bo)離，所測得(de)(de)的實(shi)際(ji)熱(re)(re)封(feng)強(qiang)(qiang)(qiang)(qiang)度(du)就人得(de)(de)多(duo)(duo)；在熱(re)(re)封(feng)內層(ceng)為PE或OPP時(shi)，熱(re)(re)封(feng)強(qiang)(qiang)(qiang)(qiang)度(du)就比同(tong)樣厚(hou)度(du)的BOPP好得(de)(de)多(duo)(duo)。