物(wu)料(liao)凍(dong)幹(gan)時(shi)的(de)共晶點和共(gong)溶點

物(wu)料(liao)的共(gong)晶點(或(huo)共(gong)晶溫度) 是(shi)指(zhi)物(wu)料(liao)中(zhong)的(de)水(shui)分全部(bu)凍(dong)結(jie)時(shi)的(de)溫度。為(wei)保(bao)證物(wu)料(liao)*凍(dong)結(jie) ,預(yu)凍(dong)溫(wen)度要比(bi)物(wu)料(liao)的共(gong)晶點低(di) 5～10 ℃。若預(yu)凍(dong)溫(wen)度過低(di) ,會(hui)增加(jia)能耗和生(sheng)產成(cheng)本(ben);若(ruo)預凍(dong)溫(wen)度高於(yu)共(gong)晶點 ,則不(bu)能保(bao)證物(wu)料(liao)中(zhong)的(de)水(shui)分*凍(dong)結(jie) ,物(wu)料(liao)內(nei)部(bu)水分將不(bu)能*以冰的(de)形(xing)式(shi)升華 ,導致(zhi)物(wu)料(liao)在(zai)幹(gan)燥過程(cheng)中(zhong)發(fa)生收(shou)縮和失(shi)形等。另外(wai)未凍(dong)結(jie)的(de)水(shui)分中(zhong)所(suo)含(han)溶質 ,在(zai)幹(gan)燥過程(cheng)中(zhong)可(ke)能隨(sui)內(nei)部(bu)水分向物(wu)料(liao)表面(mian)遷移(yi) ,出現凍(dong)幹(gan)制(zhi)品(pin)表面硬化(hua)現象(xiang)[。物(wu)料(liao)的共(gong)熔點(dian)(或(huo)共(gong)熔(rong)溫度) 是(shi)指(zhi)*凍(dong)結(jie)的(de)物(wu)料(liao) ,當溫(wen)度升至某(mou)壹(yi)值(zhi)時(shi) ,物(wu)料(liao)內(nei)部(bu)的冰晶開始熔(rong)化(hua)時(shi)的(de)溫度。幹燥(zao)時(shi)加(jia)熱(re)溫度不(bu)能高於(yu)物(wu)料(liao)的共(gong)熔點(dian) ,否則在(zai)物(wu)料(liao)內(nei)部(bu)將會(hui)產生(sheng)氣(qi)泡(pao)或(huo)充(chong)氣(qi)膨脹 ,出(chu)現融化(hua)和幹(gan)縮現象(xiang) ,影響凍(dong)幹(gan)制(zhi)品(pin)的質量(liang)。故準(zhun)確(que)地測(ce)定(ding)物(wu)料(liao)的共(gong)晶點與(yu)共熔(rong)點 ,對冷(leng)凍(dong)幹(gan)燥(zao)工(gong)藝方(fang)案的制(zhi)定(ding)和凍(dong)幹(gan)過(guo)程(cheng)的(de)優(you)化(hua)控(kong)制(zhi)具有重要的(de)意(yi)義。同壹(yi)物(wu)料(liao)在(zai)降(jiang)溫和升溫過程(cheng)中(zhong)電阻突(tu)然(ran)增(zeng)大(da)或(huo)減(jian)小的溫(wen)度區(qu)域(yu)不(bu)同 ,曲線的轉(zhuan)折點(dian)也(ye)不(bu)同 ,即(ji)同壹(yi)物(wu)料(liao)的共(gong)晶點與(yu)共熔(rong)點不(bu)同。對所測物(wu)料(liao)而(er)言 ,其共(gong)晶溫度比共(gong)熔(rong)溫度偏(pian)低。在(zai)做凍(dong)幹(gan)時(shi)凍(dong)幹(gan)輔料(liao)的篩選需測定(ding)共晶點、共(gong)熔點(dian)、玻璃(li)態(tai)轉(zhuan)換及(ji)塌陷溫度。包括不(bu)加(jia)輔料(liao)、加(jia)不(bu)同輔料(liao)及(ji)不(bu)同用量(liang)輔料(liao)等。

Pilot10-15S中(zhong)試(shi)真空冷(leng)凍(dong)幹(gan)燥(zao)機(ji)，應用於(yu)科研、生物(wu)基因工程(cheng)、新(xin)型材料(liao)、大健(jian)康(kang)、食品型(xing)。適合幹(gan)燥(zao)水(shui)溶性溶液(ye)、懸濁液(ye)或(huo)糊(hu)狀物(wu)質(zhi)，其共(gong)晶點溫(wen)度高於(yu)-30℃。