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塑料薄膜的表面性能及其处理

2021-12-08 13:39:55 ob欧宝体育(中国 )官方网站入口 浏览次数 721

塑料薄(bo)(bo)(bo)膜(mo)(mo)在包(bao)(bao)装(zhuang)(zhuang)领域的应(ying)用*为广泛。塑料薄(bo)(bo)(bo)膜(mo)(mo)可用于食品(pin)(pin)包(bao)(bao)装(zhuang)(zhuang)、电器产品(pin)(pin)包(bao)(bao)装(zhuang)(zhuang)、日用品(pin)(pin)包(bao)(bao)装(zhuang)(zhuang)、服装(zhuang)(zhuang)包(bao)(bao)装(zhuang)(zhuang)等(deng)等(deng)。它(ta)们有(you)一(yi)个共同点,就是对塑料薄(bo)(bo)(bo)膜(mo)(mo)都要(yao)进行彩色印刷,而作为食品(pin)(pin)包(bao)(bao)装(zhuang)(zhuang)还要(yao)进行多层复合(he)或(huo)真空镀铝(lv)(lv)等(deng)工(gong)艺操作。因此,要(yao)求塑料薄(bo)(bo)(bo)膜(mo)(mo)表面自由能要(yao)高、湿张力要(yao)大,以有(you)利于印刷油墨、粘合(he)剂或(huo)镀铝(lv)(lv)层与塑料薄(bo)(bo)(bo)膜(mo)(mo)的牢(lao)固粘合(he);在塑料薄(bo)(bo)(bo)膜(mo)(mo)生产卷取和高速包(bao)(bao)装(zhuang)(zhuang)过(guo)程中,则要(yao)求薄(bo)(bo)(bo)膜(mo)(mo)表面有(you)一(yi)定的摩擦性能防(fang)(fang)止(zhi)薄(bo)(bo)(bo)膜(mo)(mo)粘连或(huo)打滑;在用于电器、电子产品(pin)(pin)等(deng)包(bao)(bao)装(zhuang)(zhuang)时,则要(yao)求薄(bo)(bo)(bo)膜(mo)(mo)具有(you)一(yi)定的防(fang)(fang)静电性能等(deng)等(deng)。

塑料薄膜的表面张力

塑料薄(bo)(bo)膜(mo)(mo)的表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)张(zhang)力(li)(li)取决于(yu)塑料薄(bo)(bo)膜(mo)(mo)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)自由能(neng)(neng)大小,而薄(bo)(bo)膜(mo)(mo)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)能(neng)(neng)又(you)取决于(yu)薄(bo)(bo)膜(mo)(mo)材料本身(shen)的分子结(jie)构。多数塑料薄(bo)(bo)膜(mo)(mo)如聚烯(xi)烃薄(bo)(bo)膜(mo)(mo)(LDPE、HDPE、LLDPE、PP)属(shu)非极(ji)性聚合(he)物(wu),其(qi)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)自由能(neng)(neng)小,表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)湿(shi)(shi)张(zhang)力(li)(li)较(jiao)低,一般为30达(da)因/厘(li)米左(zuo)右。理论(lun)上讲,若物(wu)体的表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)张(zhang)力(li)(li)低于(yu)33达(da)因/厘(li)米,普通的油墨或粘合(he)剂(ji)就无(wu)法(fa)附着牢固,因此必须对其(qi)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)处理。聚酯类(PET、PBT、PEN、PETG)是(shi)属(shu)于(yu)极(ji)性高(gao)分子,其(qi)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)自由能(neng)(neng)较(jiao)高(gao),表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)湿(shi)(shi)张(zhang)力(li)(li)在40达(da)因/厘(li)米以上。但是(shi)对于(yu)高(gao)速彩(cai)色印(yin)刷或为增加真空镀铝层与(yu)BOPET薄(bo)(bo)膜(mo)(mo)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)之间(jian)的结(jie)合(he)力(li)(li),也还需要对BOPET薄(bo)(bo)膜(mo)(mo)进行表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)处理,以进一步提高(gao)其(qi)表(biao)(biao)(biao)(biao)(biao)面(mian)(mian)(mian)湿(shi)(shi)张(zhang)力(li)(li)。

塑(su)料薄膜表面处(chu)(chu)理的(de)方法(fa)有:电(dian)(dian)晕处(chu)(chu)理法(fa)、化学处(chu)(chu)理法(fa)、机(ji)械打毛法(fa)、涂层法(fa)等,其中*常采用的(de)是(shi)电(dian)(dian)晕处(chu)(chu)理法(fa)。

电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)法的(de)(de)(de)基本原理(li)(li)(li)是:通过在(zai)(zai)金属电(dian)(dian)(dian)(dian)(dian)(dian)极(ji)与(yu)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)辊(gun)(一(yi)般(ban)为耐高(gao)温(wen)、耐臭(chou)氧(yang)、高(gao)绝缘的(de)(de)(de)硅橡胶(jiao)(jiao)辊(gun))之间施(shi)加(jia)(jia)高(gao)频(pin)、高(gao)压(ya)(ya)电(dian)(dian)(dian)(dian)(dian)(dian)源(yuan),使(shi)之产(chan)(chan)生(sheng)放电(dian)(dian)(dian)(dian)(dian)(dian),于是使(shi)空气电(dian)(dian)(dian)(dian)(dian)(dian)离并(bing)(bing)形成(cheng)大量臭(chou)氧(yang)。同(tong)时,高(gao)能(neng)量电(dian)(dian)(dian)(dian)(dian)(dian)火花冲(chong)击(ji)薄(bo)膜(mo)(mo)(mo)(mo)表面(mian)。在(zai)(zai)它们(men)的(de)(de)(de)共同(tong)作用下,使(shi)塑(su)(su)(su)料(liao)薄(bo)膜(mo)(mo)(mo)(mo)表面(mian)产(chan)(chan)生(sheng)活(huo)化(hua)、表面(mian)能(neng)增加(jia)(jia)。通过电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)可使(shi)聚烯烃薄(bo)膜(mo)(mo)(mo)(mo)的(de)(de)(de)湿张(zhang)(zhang)力(li)提(ti)高(gao)到38达因/厘米(mi);可使(shi)聚酯薄(bo)膜(mo)(mo)(mo)(mo)的(de)(de)(de)表面(mian)湿张(zhang)(zhang)力(li)达到52-56达因/厘米(mi)以上。电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)塑(su)(su)(su)料(liao)薄(bo)膜(mo)(mo)(mo)(mo)表面(mian)湿张(zhang)(zhang)力(li)的(de)(de)(de)大小与(yu)施(shi)加(jia)(jia)于电(dian)(dian)(dian)(dian)(dian)(dian)极(ji)上的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)高(gao)低、电(dian)(dian)(dian)(dian)(dian)(dian)极(ji)与(yu)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)辊(gun)之间的(de)(de)(de)距离等因素有(you)关。当(dang)然,电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)应当(dang)适度,并(bing)(bing)非(fei)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)强度越高(gao)越好。这(zhei)里(li)值得注意的(de)(de)(de)是塑(su)(su)(su)料(liao)薄(bo)膜(mo)(mo)(mo)(mo)与(yu)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)辊(gun)之间应避免(mian)夹入(ru)(ru)(ru)空气,否(fou)则有(you)可能(neng)使(shi)薄(bo)膜(mo)(mo)(mo)(mo)的(de)(de)(de)反(fan)面(mian)也被电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)了。反(fan)面(mian)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)造成(cheng)的(de)(de)(de)后果是:1有(you)可能(neng)产(chan)(chan)生(sheng)油墨印刷的(de)(de)(de)反(fan)粘现象;2在(zai)(zai)镀铝时会发(fa)生(sheng)镀铝层(ceng)转移(yi),在(zai)(zai)涂胶(jiao)(jiao)时会发(fa)生(sheng)涂胶(jiao)(jiao)层(ceng)转移(yi)。防止薄(bo)膜(mo)(mo)(mo)(mo)反(fan)面(mian)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)的(de)(de)(de)主要(yao)措(cuo)施(shi)是要(yao)调节好电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)处(chu)(chu)理(li)(li)(li)辊(gun)前的(de)(de)(de)橡胶(jiao)(jiao)压(ya)(ya)紧辊(gun)的(de)(de)(de)压(ya)(ya)力(li),压(ya)(ya)紧辊(gun)两端压(ya)(ya)力(li)既要(yao)一(yi)致且压(ya)(ya)力(li)大小又要(yao)合适。另外,电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)辊(gun)和压(ya)(ya)紧辊(gun)必须(xu)进(jin)行(xing)严(yan)格(ge)的(de)(de)(de)动(dong)静平(ping)衡试验(yan),径向跳动(dong)要(yao)求小于0.05毫米(mi),目的(de)(de)(de)是保(bao)证塑(su)(su)(su)料(liao)薄(bo)膜(mo)(mo)(mo)(mo)平(ping)整地进(jin)入(ru)(ru)(ru)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)辊(gun)、防止夹入(ru)(ru)(ru)空气,从(cong)而避免(mian)发(fa)生(sheng)反(fan)面(mian)电(dian)(dian)(dian)(dian)(dian)(dian)晕(yun)(yun)(yun)的(de)(de)(de)现象。