熱封次數(shu)越多(duo)，熱封強度越高(gao)，縱向(xiang)熱封次數(shu)取決于縱向(xiang)焊(han)棒的有效(xiao)長度和袋長之(zhi)比。
橫(heng)向(xiang)(xiang)熱(re)(re)(re)封(feng)(feng)次數(shu)由機(ji)臺橫(heng)向(xiang)(xiang)熱(re)(re)(re)封(feng)(feng)裝置的組數(shu)決定。良(liang)好的熱(re)(re)(re)封(feng)(feng)，要(yao)求熱(re)(re)(re)封(feng)(feng)次數(shu)至少(shao)達(da)到兩次以(yi)上。相同結(jie)構(gou)和厚度(du)(du)(du)(du)的復(fu)(fu)合(he)膜，復(fu)(fu)合(he)層(ceng)(ceng)間剝(bo)(bo)(bo)離度(du)(du)(du)(du)越(yue)高，熱(re)(re)(re)封(feng)(feng)強度(du)(du)(du)(du)越(yue)大；對于(yu)復(fu)(fu)合(he)剝(bo)(bo)(bo)離強度(du)(du)(du)(du)低的產品，焊縫破壞往(wang)往(wang)是焊縫處的復(fu)(fu)合(he)膜先層(ceng)(ceng)間剝(bo)(bo)(bo)離，致使(shi)由內面熱(re)(re)(re)封(feng)(feng)層(ceng)(ceng)獨(du)立(li)承(cheng)受破壞拉力，而面層(ceng)(ceng)材料失(shi)去補(bu)強作用(yong)，致使(shi)焊縫的熱(re)(re)(re)封(feng)(feng)強度(du)(du)(du)(du)由此大為降低；若復(fu)(fu)合(he)層(ceng)(ceng)間剝(bo)(bo)(bo)離度(du)(du)(du)(du)強，則不致發生焊邊處層(ceng)(ceng)問的剝(bo)(bo)(bo)離，所測得的實(shi)際(ji)熱(re)(re)(re)封(feng)(feng)強度(du)(du)(du)(du)就人得多(duo)；在熱(re)(re)(re)封(feng)(feng)內層(ceng)(ceng)為PE或OPP時，熱(re)(re)(re)封(feng)(feng)強度(du)(du)(du)(du)就比(bi)同樣厚度(du)(du)(du)(du)的BOPP好得多(duo)。