涂裝線噴粉噴漆(qi)后掉粉現象(xiang)的原(yuan)因及處(chu)理

　　一般涂裝線廠家的回答是，影響粉末顆粒接受電荷和保持電荷的主要因素是粉末的介電常數，粉末介電常數越低，顆粒越容易帶電，但電荷的損失也就越容易，這體現在粉末對工件的吸力不強，稍微受振動脫落的粉末。對于靜電噴涂粉末涂料，應盡量具有較高的介電常數，這樣會使粉末吸附性能大大提高。

　　由(you)靜電(dian)(dian)(dian)(dian)可知，帶電(dian)(dian)(dian)(dian)隔(ge)離(li)導體(ti)表面(mian)電(dian)(dian)(dian)(dian)荷的(de)分布與(yu)表面(mian)曲率半(ban)徑有關(guan)。大(da)曲率(即(ji)表面(mian)尖點(dian))處的(de)電(dian)(dian)(dian)(dian)荷密度(du)高(gao)(gao)，附近空(kong)(kong)間的(de)電(dian)(dian)(dian)(dian)場(chang)強度(du)也高(gao)(gao)。當(dang)電(dian)(dian)(dian)(dian)場(chang)強度(du)達到(dao)(dao)足以電(dian)(dian)(dian)(dian)離(li)周圍(wei)氣(qi)體(ti)時(shi)，導體(ti)的(de)上端就會(hui)(hui)放電(dian)(dian)(dian)(dian)。在(zai)負(fu)極(ji)高(gao)(gao)壓放電(dian)(dian)(dian)(dian)的(de)情(qing)況(kuang)下(xia)，離(li)開導體(ti)的(de)電(dian)(dian)(dian)(dian)子(zi)(zi)(zi)會(hui)(hui)受(shou)到(dao)(dao)強電(dian)(dian)(dian)(dian)場(chang)的(de)加速(su)(su)，使其與(yu)空(kong)(kong)氣(qi)分子(zi)(zi)(zi)碰(peng)撞，電(dian)(dian)(dian)(dian)離(li)產生正(zheng)離(li)子(zi)(zi)(zi)和電(dian)(dian)(dian)(dian)子(zi)(zi)(zi)。然(ran)后，新的(de)電(dian)(dian)(dian)(dian)子(zi)(zi)(zi)相互加速(su)(su)，導致(zhi)空(kong)(kong)氣(qi)分子(zi)(zi)(zi)經歷“電(dian)(dian)(dian)(dian)子(zi)(zi)(zi)雪崩”過程。電(dian)(dian)(dian)(dian)子(zi)(zi)(zi)的(de)質量很小，當(dang)它沖出電(dian)(dian)(dian)(dian)離(li)區(qu)時(shi)，很快就會(hui)(hui)被(bei)一(yi)個(ge)重(zhong)得多的(de)氣(qi)體(ti)分子(zi)(zi)(zi)吸引，變(bian)成一(yi)個(ge)自由(you)的(de)負(fu)離(li)子(zi)(zi)(zi)。這種(zhong)負(fu)離(li)子(zi)(zi)(zi)在(zai)電(dian)(dian)(dian)(dian)場(chang)力的(de)作用下(xia)跑向正(zheng)極(ji)，在(zai)電(dian)(dian)(dian)(dian)離(li)層(ceng)(ceng)產生一(yi)層(ceng)(ceng)暈(yun)光，即(ji)暈(yun)光放電(dian)(dian)(dian)(dian)，當(dang)粉末(mo)通過電(dian)(dian)(dian)(dian)暈(yun)外圍(wei)時(shi)，就會(hui)(hui)被(bei)跑向正(zheng)極(ji)的(de)負(fu)離(li)子(zi)(zi)(zi)碰(peng)撞而(er)帶電(dian)(dian)(dian)(dian)。

　　工業粉(fen)(fen)末(mo)(mo)(mo)涂料多(duo)為結構復雜的(de)(de)(de)(de)聚合(he)物絕(jue)緣體(ti)。只有(you)當粉(fen)(fen)末(mo)(mo)(mo)表面有(you)合(he)適的(de)(de)(de)(de)位(wei)置接受電(dian)(dian)荷時，負離子(zi)(zi)才能吸附(fu)到(dao)粉(fen)(fen)末(mo)(mo)(mo)表面的(de)(de)(de)(de)這一(yi)部分。對于陰離子(zi)(zi)，該(gai)位(wei)點可能是粉(fen)(fen)末(mo)(mo)(mo)組(zu)合(he)物中(zhong)帶正(zheng)電(dian)(dian)的(de)(de)(de)(de)雜質或組(zu)合(he)物中(zhong)潛在的(de)(de)(de)(de)坑，也可能是純機械的(de)(de)(de)(de)。但無論(lun)哪種吸附(fu)機理，離子(zi)(zi)都不(bu)容(rong)易沉積(ji)在每個粒(li)子(zi)(zi)上。粉(fen)(fen)末(mo)(mo)(mo)顆粒(li)的(de)(de)(de)(de)表面電(dian)(dian)阻(zu)很(hen)高，電(dian)(dian)荷不(bu)會因導電(dian)(dian)而重新分布(bu)，所以表面電(dian)(dian)荷分布(bu)不(bu)均勻。

　　自動流水線設備廠家認為，由于電暈放電，粉末涂層顆粒在電極附近帶負電荷。當粉末顆粒剛離開炮口時，由壓縮空氣輸送力吹出靠近工件(正)，受電場力引導，使涂層牢固地吸附在工件上。通常只需要幾秒鐘就可以達到50-100μm的涂層厚度。當粉末層達到一定厚度時，表面儲存一層厚厚的負電荷屏蔽層，使負電荷粒子被排斥回去，涂層不再增厚。涂裝過程現在已經完成。