熱封(feng)次數(shu)越多，熱封(feng)強度越高，縱向(xiang)熱封(feng)次數(shu)取(qu)決于縱向(xiang)焊棒的有(you)效長度和袋長之(zhi)比(bi)。
橫向熱(re)(re)封(feng)(feng)次數(shu)由(you)機臺橫向熱(re)(re)封(feng)(feng)裝置的(de)組數(shu)決(jue)定。良好(hao)的(de)熱(re)(re)封(feng)(feng)，要(yao)求熱(re)(re)封(feng)(feng)次數(shu)至少達(da)到兩次以上。相同結構(gou)和厚度(du)(du)的(de)復(fu)合(he)膜(mo)，復(fu)合(he)層(ceng)(ceng)間(jian)(jian)剝離度(du)(du)越高，熱(re)(re)封(feng)(feng)強(qiang)度(du)(du)越大；對于(yu)復(fu)合(he)剝離強(qiang)度(du)(du)低(di)的(de)產(chan)品，焊縫(feng)破(po)壞往(wang)往(wang)是(shi)焊縫(feng)處的(de)復(fu)合(he)膜(mo)先(xian)層(ceng)(ceng)間(jian)(jian)剝離，致使由(you)內面熱(re)(re)封(feng)(feng)層(ceng)(ceng)獨立承受破(po)壞拉力，而面層(ceng)(ceng)材料失去補(bu)強(qiang)作(zuo)用，致使焊縫(feng)的(de)熱(re)(re)封(feng)(feng)強(qiang)度(du)(du)由(you)此大為降(jiang)低(di)；若復(fu)合(he)層(ceng)(ceng)間(jian)(jian)剝離度(du)(du)強(qiang)，則不致發生焊邊(bian)處層(ceng)(ceng)問(wen)的(de)剝離，所測得的(de)實際熱(re)(re)封(feng)(feng)強(qiang)度(du)(du)就人得多(duo)；在熱(re)(re)封(feng)(feng)內層(ceng)(ceng)為PE或OPP時，熱(re)(re)封(feng)(feng)強(qiang)度(du)(du)就比(bi)同樣厚度(du)(du)的(de)BOPP好(hao)得多(duo)。