仇慧麗 楊群 崔進 裴劉軍 胡庚昊



摘要:防水透濕膜是一種兼具耐水滲透性和水汽透過性的功能膜材料,其與纖維面料復合,可制備具有獨特防護性和兼顧透氣、透濕于一體的舒適型功能性紡織品。目前,用于可穿戴紡織品的人體-環境交互領域的濕熱傳輸膜材料主要有聚四氟乙烯疏水膜、聚氨酯親水膜和靜電紡絲纖維膜。本文對這3種防水透濕膜的結構、制備方法、防水透濕機理及應用性等進行綜述,總結防水透濕膜的研究進展及其在紡織上的應用趨勢,并對未來智能防水透濕薄膜的研發重點做出展望。
關鍵詞:防水透濕性;功能膜材料;智能織物;靜電紡絲纖維膜;防護性
中圖分類號:TB34,TQ028
文獻標志碼:A
文章編號:1009-265X(2023)02-0244-12
防水透濕織物,是全球紡織業多年以來一直追求的兼顧防水、透氣、透濕于一體的紡織品。雖然防水性、透濕性這兩個看似矛盾的性能起初難以兼具于一塊織物上,但隨著研究的深入及技術的發展,具有獨特防護性和兼顧透氣、透濕于一體的功能性紡織品問世,并取得突破進展,而隨環境溫濕度變化而自動調節人體微氣候的智能防水透濕材料也正處于全面發展階段[1-2],應運而生的防水透濕膜材料也引起了廣泛關注。
防水透濕膜是一種兼具耐水滲透性和濕氣透過性的功能膜材料,其與纖維面料復合,可制造具有獨特防護性和舒適性的功能紡織品。目前,用于可穿戴紡織品的人體-環境交互領域的濕熱傳輸膜材料,主要有聚四氟乙烯(PTFE)疏水性微孔膜、聚氨酯親水性無孔膜和靜電紡絲纖維膜[3-4]。由于水分子在固體中的傳輸比在孔道中要慢,因此,PTFE疏水性微孔膜的防水透濕性主要源于其孔徑的調控。當孔徑小于雨滴尺寸但大于水蒸氣分子時,具有較好的防水透濕性,但由于膜材料疏水,會導致水滴在孔道中聚集堵塞。聚氨酯親水性膜則是通過吸濕-轉移-釋放過程將水汽分子排到外部的,因其無孔結構而具有較高的耐水壓,但透氣性和透濕性相對較差,使穿著者產生不適感[5]。靜電紡絲纖維膜因纖維直徑小、孔隙率高,從而可有效提高其透氣透濕性,但其防水性、機械性能與透氣透濕性的兼顧需統籌考慮,且目前離大規模產業化應用還有一段距離[6-7]。因此,本文主要從目前用于紡織品防水透濕功能的角度出發,介紹幾種膜材料的結構、制備方法、防水透濕機理及應用,并對未來智能防水透濕薄膜的研發重點進行展望。
1聚四氟乙烯防水透濕膜
1.1聚四氟乙烯分子結構
聚四氟乙烯(PTFE)是一種高結晶的聚合物,其分子鏈是由氟和碳兩種元素通過共價鍵結合而成。由于負電荷的作用,相鄰氟原子之間相互排斥,從而分子鏈在空間上呈螺旋構象,并形成一個緊密“氟代”保護層[8],如圖1所示。由于PTFE分子間的堆砌密度大,各種試劑難以深入分子鏈中間,外加氟原子本身極高的化學惰性,PTFE幾乎能夠抵抗所有的強酸、強堿及有機溶劑,呈現出無可比擬的化學穩定性[9]。此外,由于PTFE分子結構為四個氟原子包覆著一個碳原子,氟原子的化學惰性使PTFE呈現出較好的疏水性以及較小的吸水率和滲透性[10]。因此,可制備具有防水、防污性的功能型防護服,一度在紡織工業領域有著廣泛的應用[11]。
1.2聚四氟乙烯防水透濕膜的在紡織上應用進展
美國人Gore于1962年研制出了一種具有微孔結構的PTFE防水透濕性薄膜,采用層壓復合技術將其與紡織面料相結合,制備出具有優良的防水透濕性紡織品,并將其商業命名為Gore-Tex,于1976年推向市場[12]。此階段的制備工藝主要是將PTFE的細粉加熱熔融后形成薄膜,再進行快速拉伸,隨后冷卻形成厚度約25 μm、孔隙率為82%的網狀微細多孔結構,其孔徑大小大約是水滴(平均直徑約為100 μm)的兩萬分之一,但又比水蒸氣分子(平均直徑約為0.4 nm)大700倍[13]。因此,其防水透濕便是基于膜的孔徑小于雨滴尺寸但大于水蒸氣分子尺寸,水滴不通過而防水,水汽分子能通過而透濕[14],如圖2所示。采用黏合劑將所得PTFE微孔薄膜與織物復合,可得到透濕量約5 kg/(m2·d),耐靜水壓力大于9.8 kPa的防水透濕織物,并且此防水透濕織物兼具耐化學試劑腐蝕、耐熱、拒水、拒油、抗靜電性等性能[15]。
此外,以PTFE為原料,經紡絲或制成薄膜后切割或原纖化等方式制得PTFE纖維。其強度高,延伸性好,化學穩定、耐腐蝕等性能優于其他合成纖維[16]。由于PTFE微納米纖維因直徑較細,尺度效應十分顯著,展現出優異的性能。而且,纖維的細化增加了纖維膜表面的粗糙度,疏水性進一步提高[17]。雖然PFTE膜材料具有如此優異的防水性能,但其制備工藝復雜,生產條件嚴苛,需要特殊的制膜設備和原料,且工藝技術要求非常高[18],從而極大地制約了它的進一步的應用。此外,在制造過程通常會涉及全氟辛磺酸(PFOA)和全氟辛磺酸鹽(PFOS)兩種具有高生物積累、環境持久性和長距離遷移的物質[19-21],近年來,這些具有長全氟烷基鏈(-CnF2n+1,n≥8)的含氟聚合物許多國家已禁止其廣泛應用。
通過開發兼具高防護性和舒適性的環保型防水透濕膜材料是擴大其應用需解決的主要問題。雖然一些長全氟烷基鏈的含氟聚合物具有極低的表面能,展示出出色的防水和防油性[22-25],但隨著其禁止廣泛使用,開發兼具高防護性和舒適性的環保型含氟類防水透濕膜材料是擴大含氟類材料應用的主要途徑,因此,設計具有短氟化的環保防水透濕材料已成為不可抗拒的趨勢[26-28]。研究發現,聚偏氟乙烯(PVDF)的拒水性略低于PTFE,但其在制備工藝和成膜性能優于PTFE,且不存在釋放PFOA、PFOS的風險。因此,劉延波等[29]以PVDF和聚偏氟乙烯六氟丙烯(PVDF-HFP)為原料制備了PVDF/PVDF-HFP復合納米纖維薄膜,并對其防水透濕性進行研究,發現該復合薄膜具有良好的防水和透濕性。周穎等[30]以聚氨酯(PU)和PVDF進行復合,制備PU/PVDF復合防水膜,并通過層壓工藝將其應用于織物,對比了復合膜和整理織物的防水透濕性能,結果表明,PU/PVDF復合防水膜具有較高的防水透濕性能,但是通過層壓工藝與織物復合后,防水性能有所下降。
隨著研究的進一步深入,以及綠色環保型功能助劑的開發,不少無氟防水整理劑和纖維膜由于價格優勢和工藝優勢,逐漸受到重視。Gu等[6]將聚氨酯-聚(ε-己內酯)纖維浸漬到聚二甲基硅氧烷溶液中,所得膜具有中等防水透氣性能(耐水壓為73.6 kPa,水蒸氣透過率為9.03 kg/(m2·d)。Sheng等[5]采用氨基-硅油和SiO2納米粒子對聚丙烯腈纖維膜進行改性以制備防水透濕膜,所得纖維膜表現出相似的防水性(耐水壓為74.3 kPa)和良好的透濕性(11.4 kg/(m2·d)。Zhao等[7]通過逐步的浸鍍和熱固化技術來制造無氟、高效和可生物降解的防水透濕膜,含有長烴鏈的超支化聚合物涂層提供了具有高疏水性的電紡絲醋酸纖維素(CA)纖維基質,封閉的異氰酸酯交聯劑涂層確保了碳氫化合物段在CA表面的強附著,所得到的膜的耐滲水壓為102.9 kPa,透氣性為12.3 kg/(m2·d),抗拉強度為16.0 MPa。
可持續發展刺激著生態環保產品的持續開發,防水透濕面料的風格也在不斷變化。在紡織服裝的應用中,無氟類產品在慢慢取代含氟性產品,聚氨酯、三羧酸等親水性產品也被證明是普遍且有效地適用于的紡織產品的,不僅突出了材料的設計和制備,而且提供了環保和高性能的防水透濕膜。
2聚氨酯防水透濕膜
2.1聚氨酯分子結構
聚氨酯是一種在預定溫度范圍內感知和響應外部熱刺激的功能材料,其具有相分離的為分段式結構,即熱可逆相(軟段)和固定相(硬段),如圖3所示。主要是聚氨酯分子在制備時,大分子二元醇(或二元胺)和異氰酸酯連接形成長鏈結構,因分子鏈長,表現出柔性,所以形成整個大分子鏈中的軟段結構;小分子多元醇和異氰酸酯連接形成短鏈結構,因分子鏈短,從而呈現剛性,形成大分子鏈結構中的硬段結構。軟段部分通常與剛性的硬段交替存在于聚氨酯分子鏈中,以共價鍵“尾—尾”連接[31]。由于聚氨酯硬段間的相互作用,所以它具有良好的機械性能。聚氨酯良好的回彈性得益于分子鏈的相對運動,分子鏈的運動性能很大程度取決于軟段的化學性質和鏈段長度,軟段越是呈無定形狀態,其柔順性就越好。
2.2聚氨酯防水透濕膜在紡織上的應用進展
根據自由體積理論,膜材料中可用的自由體積孔的大小和形狀控制著氣體擴散的速度和其滲透性[32]。在材料內部有大量的親水性自由體積分子,這種親水性分子可以吸收人體散發的水蒸氣分子,水分子形式的水蒸氣再與聚氨酯材料中的親水性軟段以氫鍵結合,在紡織品內外部溫濕壓力差下,通過吸濕-轉移-釋放過程將水分子排到外部,如圖4所示。
Kim等[33]發現,以異佛爾酮二異氰酸酯(IPDI)和聚酯型多元醇(PTAd)/聚醚多元醇(PPG)制備聚氨酯,其中PTAd含量越高,聚氨酯的力學性能越好,分子鏈的運動性越強。Yen等[34]研究了聚己內酯(PCL)、聚乙二醇(PEG)、PCL/PEG等不同軟鏈段共混和三嵌段PCL-PEG-PCL對聚氨酯性能的影響。由于構象和分子間氫鍵的作用[35],單酯型聚氨酯的性能最好,其次是PCL-PEG-PCL型聚氨酯。在這些體系中,聚醚聚氨酯的水蒸氣滲透率最高。由于聚氨酯軟硬鏈段之間的相分離,聚乙二醇含量越高,水蒸氣滲透率也越高。Yen等[36]提出了通過修改PCL-PEG-PCL三嵌段聚氨酯多元醇的軟段組成,增加軟鏈段中的乙二醇的比例,可以獲得更高的水蒸氣滲透率、更低的機械性能和更明顯的宏觀相分離。此外,隨著2, 2-雙(羥基甲基)丙酸(DMPA)和NCO-to-OH比例的增加,水蒸氣滲透率也增加[37]。Jeong等[38]發現PEG和DMPA形成的聚氨酯具有較低的機械性能,并且可以從較低的玻璃化溫度值(Tg)中獲得較高的水蒸氣滲透率。Cho等[39]則發現隨著聚氨酯硬段百分比的增加,或使用濃縮的聚氨酯溶液,水蒸氣滲透率降低。
基于以上研究,Lin等[40]利用聚乙二醇/聚酯多元醇PBA體系制備的聚氨酯薄膜比采用單純的PBA體系制備的聚氨酯薄膜具有更好的水蒸氣滲透性能。且當溫度低于18 ℃時,聚氨酯膜的水蒸氣滲透率較低,直到溫度高于18 ℃,水蒸氣滲透率開始明顯上升。聚氨酯膜的水蒸氣滲透率會隨著硬段比、溫度及異氰酸酯指數的增加而增加,但隨著溫度下降到Tg以下而降低。為了更好地監測水蒸氣透過率,Zhou等[41]制備了一種具有功能門的分段聚氨酯膜,并將其應用于水蒸氣滲透。當溫度從-10 ℃變化到10 ℃時,該聚合物中自由體積孔的平均半徑從0.23 nm變化到0.467 nm。因此,隨著對此膜的感知和回應外部熱刺激功能的改進,聚氨酯膜的自由體積孔洞尺寸增大,對熱刺激的敏感性增強,其水蒸氣滲透率顯著增加。因此,聚氨酯無孔膜因無孔結構而具有較高的耐水壓,但其透氣性和透濕性相對較差,使穿著者產生不適感。
為提高紡織服裝的舒適性,許多研究致力于智能濕熱管理材料,即:紡織服裝更加強調對周圍復雜多變環境的全天候適應能力,隨著環境溫度、濕度的變化自動調整自身水分、熱量的傳導,使人體表面始終保持最佳狀態,達到全天候舒適的狀態。隨環境溫度和濕度的變化能動態調節濕熱的材料中,美國Baughman團隊[42-43]曾提出對纖維加捻可以發熱,解捻可獲得一定程度的降溫,這種“扭熱制冷”是基于螺旋收縮過程中螺旋內部捻度降低導致能量的變化,但該變化在于溫度的改變,且屬于高溫形變,不適用于紡織服裝對濕熱的智能調控。東華大學王宏志教授團隊和佐治亞理工大學Elsa Reichmanis教授團隊[44]提出了基于納米通道機理的全氟磺酸樹脂的氣體響應致動材料,在體表濕熱發生變化時,利用水分蒸發可向外卷曲打開孔道,進而對體表濕熱進行調節,提高人體體表舒適感,這為智能濕熱管理材料的設計和制備提供了新的思路,但全氟磺酸鈉與纖維和織物的結合仍是一個問題。
由于在大多數情況下,熱可逆相的相變溫度(結晶熔融轉變溫度或玻璃轉變溫度)可作為可控水蒸氣滲透性的開關溫度[45]。當人體體溫上升時,它不存在微孔,所以該膜材料的防水及其排汗透濕性能比常規的防水透濕膜更好。一類研究較為深入的智能透濕材料是形狀記憶聚氨酯(溫敏性聚氨酯)防水透濕膜。在轉變溫度范圍內,形狀記憶聚氨酯具有相應的相態轉變過程和溫度。當溫度高于臨界轉變溫度時,聚合物的自由體積孔隙尺寸會明顯增大,使水蒸氣通過聚合物薄膜的通道增大,提高水蒸氣的透過率[45]。
由于形狀記憶聚氨酯的溫敏透濕機理和水分子的傳輸分別基于分子鏈運動引起的相變過程和溶解-擴散機制[40]。基于此理論,對聚氨酯軟、硬段分子結構、分子量進行設計,使其自由體積和孔隙尺寸在一定的溫度變化范圍內發生急劇的改變,從而可智能化地控制聚氨酯膜的透氣性和透濕性,如圖5所示[46]。但有研究發現,雖然其透濕量在12~45 ℃內隨溫度的升高,可從455 g/(m2·d)增加到2625 g/(m2·d)(增加4.77倍),但由于過膜阻力大,該過程經歷了近33 ℃的升溫變化,在環境溫度和濕度快速變化時難以滿足實際使用要求[47]。課題組在前期研究中也遇到類似問題,使用傳統膜結構不能有效解決。在智能防水透濕膜研究領域中,高過膜阻力導致的低通量和響應靈敏度不足的問題仍是研究者需面對的挑戰。
為降低溫敏性聚氨酯膜的水蒸氣過膜阻力,提高透濕通量,課題組[48]以不同濃度的N, N-二甲基甲酰胺(DMF)和水為凝固浴,采用濕法成膜的方法制備了多級孔聚氨酯膜,并重點研究了在凝固浴中加入氯化鈉(NaCl)對多級聚氨酯膜結構和性能的影響。研究發現,NaCl的含量對大孔的影響比較大,隨著凝固浴中NaCl的含量加大,大孔孔徑逐漸減小,且位置從皮膜向底膜過渡;而DMF用量的增加,會減緩鑄膜液中的DMF向凝固浴中擴散的速度,影響DMF與凝固浴中H2O的雙向擴散速度,從而影響膜中小孔的分布狀態。而透濕性數據與膜結構表明孔的結構和尺度不同,濕熱過膜阻力不一樣,最終影響濕熱過膜通量。Zhou等[41]在通過原位納米混合工藝將納米TiO2顆粒引入形狀記憶聚氨酯基體,制備了一種新型溫敏性聚氨酯/TiO2納米復合膜,并用于可控水蒸氣滲透。與純溫敏性聚氨酯膜相比,溫敏性聚氨酯/TiO2納米復合膜具有良好的組織結構和相變溫度(Ts),且能有效提高膜的水蒸氣透過率。特別是當溫度高于Ts時,如在50~60 ℃范圍內,溫敏性聚氨酯/TiO2納米復合膜的水蒸氣透過率值提高了114%。而當TiO2質量分數為5.0%時,納米復合膜的水蒸氣透過率能提高145%,且表現出更高的水蒸氣透過率變化和對熱刺激更敏感的性能。
當形狀記憶聚氨酯被用于戶外服裝時,需要考慮一些重要因素,如可控的水蒸氣滲透性、高機械性能和高熱、化學穩定性等。在過去的幾年里,為了改善高分子材料的機械和熱性能,國內外學者不斷地通過各種途徑對聚氨酯進行改性,以達到既有防水又有透濕功能的目的,也采用不同的工藝改變聚氨酯膜的結構,以適應環境溫度和濕度的變化,以快速調控體表微氣候。
3靜電紡絲防水透濕膜
靜電紡絲技術是一種方便、有效的制備微/納米纖維的途徑,其制備的纖維膜易于功能化改性,可用于制備防護性高、舒適性好的高性能防水透濕膜,近年來發展迅速。它的技術關鍵是在高壓靜電力的作用下,聚合物溶液或熔體會帶電并變形,在噴嘴的末端形成一個錐形的懸浮液滴,當液滴表面的靜電斥力超過它的表面張力時,液滴的表面會產生一個高速的射流,然后通過電場力拉伸、溶劑揮發,聚合物會固化形成纖維[49]。
3.1靜電紡絲防水透濕膜的結構
靜電紡絲制成的納米纖維膜,纖維直徑小,孔隙率高,孔道連通性好、多孔結構可控、易于表面改性、輕且柔等特點,適合于制造具有優異防水透濕性能的微孔膜,在功能性紡織服裝面料、屏蔽材料等領域展現出巨大的市場潛力[50-51]。目前,已經有各種防水透濕纖維膜被開發,如聚氨酯纖維膜[52]、聚丙烯腈纖維膜[24]、聚丙烯纖維膜[53-54]等。辛東坡等[55]采用靜電紡絲技術,將聚丙烯腈(PAN)聚合物制成納米纖維薄膜,并對其防水透濕性進行了研究,實驗結果表明PAN纖維膜具有較好的透濕性。Miao等[56]采用簡單、可控的靜電紡絲技術和堿處理,展示了一種基于聚氨酯/聚氨酯-聚丙烯腈/聚丙烯腈的三層纖維膜的功能性吸濕排汗織物,如圖6所示,其具有優越的防水滲透性和定向吸濕排汗特性。在轉移層誘導的遞進潤濕性下,所制備的纖維膜表現出優越的抗靜水壓和較高的單向遷移指數R,均遠高于雙層的聚氨酯/聚丙烯腈纖維膜。該研究表明,以聚氨酯膜作為內層,可使水滲透,同時不沿表面擴散,而聚氨酯-聚丙烯腈纖維膜作為中間轉移層,可促使水汽從內層滲透到外層,并能阻止其反向滲透,從而促進了水的運輸和蒸發。
3.2靜電防水透濕膜在紡織上的應用進展
2007年,韓國首爾國立大學的Kang等[57]首次將靜電紡絲技術引入到紡織服裝領域,其將聚氨酯(PU)直接電紡在襯底織物上制成多功能織物,并與涂布聚氨酯樹脂的織物進行比較,發現,在PU紡絲溶液在質量分數為12%、電壓為13 kV、接收距離為10 cm的制備條件下,所得到的靜電紡絲纖維能夠有效地覆蓋面料,在相同厚度下,靜電紡絲纖維織物的重量比樹脂涂層織物輕,透氣性能好,透濕率高,可達9.1 kg/(m2·d),但其耐水壓極低(3.6 kPa),必須進行改進,才能適應市場需求。東華大學的Ge等[58]通過引入含有全氟烷烴段(—C8F17)的合成氟化聚氨酯摻雜改性方法制備出聚氨酯/含氟聚氨酯(PU/FPU)靜電防水透濕膜,氟聚氨酯的引入大幅度地提高了纖維膜的耐水性,其耐水壓增加到39.3 kPa,提高了約10倍,同時該材料具有較好的透濕性,水蒸氣透過率仍高達9.2 kg/(m2·d)。隨后,Zhang等[59]通過將氯化鋰引入聚氨酯氟化聚氨酯溶液,降低纖維膜的孔徑,制備的纖維膜具有良好的防水性和透濕性,靜水壓力達到82.1 kPa,水蒸氣透過率為10.9 kg/(m2·d)。然而,此類防水透濕纖維膜材料所使用的是長鏈氟碳聚合物(Rfn,n≥8),因此,開發環保的氟化聚合物來取代傳統的氟化物是材料科學家的重點。
目前,防水性能優異且環保的氟化聚合物是含有4個全氟原子(Rfn,n=4)的水性含氟化學品,可通過整理使織物或膜材料具有優異的防水性。然而,該產品的缺點是疏水涂層的不均勻性和耐久性差,以及處理工藝復雜[27]。于是,在纖維中摻入環保的氟化聚合物(Rfn,n=4)制備防水透氣膜具有重要意義,但也極具挑戰性。Zhao等[60]通過靜電紡絲技術合成了一種具有雙端短鏈全氟丁基(—C4F9)鏈的新型氟化聚氨酯彈性體,并將其摻雜進聚氨酯纖維基體中,通過靜電紡絲制得復合纖維膜,該纖維膜具有強大而持久的疏水性。此外,加入硝酸銀可大大降低其最大孔徑,從而顯著提高了其防水性,靜水壓力高達102.8 kPa,水蒸氣透過率為12.9 kg/(m2·d),且具有較高的力學性能(9.8 MPa)。
受自然界的啟發,在結構或性質進行的仿生制備超疏水人工表面的仿生技術取得了很大的進展。Muthiah等[61]和Lin等[62]通過引入環境友好型的有機硅疏水劑和疏水性的二氧化硅(SiO2)納米顆粒,通過靜電紡絲制備了仿生超疏水纖維膜,其表現出納米突起和眾多凹槽組合的結構,達到類似荷葉的超疏水結構,大大提升了其防水性和耐水壓。通過靜電紡絲制備出具有多孔微球和納米纖維的復合結構的荷葉狀超疏水表面,多孔微球在其超疏水性中起著主導作用,與此同時納米纖維將單個的微球連接在一起,增強了復合材料薄膜的防水性能[63]。同樣,根據Murray定律可知,自然界中的動植物體所具有的網絡狀等級結構,例如葉子的葉脈、植物的根莖系統、人體的血管系統等,可以確保生命體在新陳代謝與物質能量傳遞過程中所受阻力最小、運輸效率最高[64]。Wang等[65]通過靜電紡絲技術構筑了仿生樹狀多級分叉網絡結構,并利用纖維的毛細管效應成功制備了單向導濕性纖維薄膜,如圖7所示。這種仿生樹狀多級分叉網絡結構由大孔-微米孔-亞微米孔的多級連通孔道組成,具有類似于植物蒸騰作用的多級網絡狀結構,遵循Murray定律最大化物質輸運原則,具有快速定向導濕性,水分蒸發速率高達0.67 g/h。
除此之外,靜電紡絲可以開發具有潤濕性好、孔徑小、比表面積大等特點的纖維膜。可通過設計制備多層梯度孔結構的纖維膜,實現漸潤性,這就是Janus潤濕性和潤濕性梯度的結合[66-68]。只不過,早期關于通過電紡纖維膜定向輸送水汽的研究主要在控制每一層厚度和潤濕性的雙層結構上[69],導致在提高輸水能力和防止反向滲透的協同作用下取得的成效有限,阻礙了水分從體表向環境轉移過程中的實際應用。
通過對靜電紡絲纖維膜的表面和內部的改性,以提高防水透濕膜的相關性能。Xu等[70]采用靜電紡絲法和二步刮刀涂層方法結合制備PAN/PU/TiO2薄膜,該復合薄膜具有94.3°的前進接觸角,不能滿足防水要求。然后,采用2-羥基-4-正辛氧基二苯甲酮與氟化丙烯酸共聚物進行改性,可獲得了多功能超疏水膜。Sheng等[28]利用后處理技術,采用聚二甲基硅氧烷和疏水性的二氧化硅(SiO2)納米顆粒對聚丙烯腈(PAN)納米纖維膜進行涂層改性,聚二甲基硅氧烷在PAN纖維膜表面形成疏水功能層的同時還構筑了黏合結構,從而有效地改善了纖維的機械性能和透濕性,整理后的纖維膜具有較好的防水性(耐水壓為74.3 kPa)和透濕性(透濕量為11.4 kg/(m2·d))。但隨著改性劑用量的繼續增加,纖維膜的透濕量出現降低的趨勢,可能是因為改性劑用量的增加,纖維膜的孔隙率下降所致。通過后整理想進一步提升纖維膜材料的透濕性仍存在一定的局限性。
因此,可以通過功能性吸濕紡織品的結構設計,獲得防水透濕維膜能夠自發地將汗液從皮膚表面帶走,為人體提供一個極其干燥和舒適的體表環境。
4結語
防水透濕膜是一種兼具耐水滲透性和濕氣透過性的功能膜材料,其是制造具有獨特防護性和兼顧防水、透氣、透濕于一體的功能性紡織品的關鍵材料之一。在全球公共安全應急產業被廣泛關注的大背景下,安全防護用紡織材料在快速發展,也面臨著良好的市場機遇,但同時,日益復雜的社會生產、生活環境也對其提出了更高要求。用于可穿戴紡織品的人體-環境交互領域的含氟性疏水性膜、聚氨酯親水膜和靜電紡絲纖維膜的結構、制備方法、防水透濕機理及其應用性各不相同,也有著各自的優缺點。如何將防護阻隔性與透氣透濕性這一矛盾性能有機統一,提升安全防護紡織材料的舒適性問題是勢必要攻克的難關。通過對防水透濕纖維膜結構設計與水蒸氣傳遞的機理相結合,使防水透濕織物越來越趨向于智能化、舒適化和環保化,從而以高性能纖維,產業用紡織品,智能化織物能夠在各種環境中時刻調節體表最佳溫度和濕度,這必將使人們的未來生活更加健康、美好。
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Research progress and application of waterproof and moisture permeable membranes on textiles
QIU Huili1a,YANG Qun1a,1b, CUI Jin2, PEI Liujun1a,1b, HU Genghao1a
(1a.School of Textiles and Fashion; 1b.Shanghai Engineering Research Center for Clean Production of Textile Chemistry, Shanghai
University of Engineering Science, Shanghai 201620, China; 2. Shanghai Evershine Co., Ltd, Shanghai 201600, China)
Abstract:
Waterproof and moisture permeable membranes are a kind of functional membrane material with both water permeability and water vapor permeability. Combined with fiber fabric, they can prepare functional textiles with unique protective properties, waterproofness, breathabilityand moisture permeability. Currently, the moisture and heat transfer membranes used in human-environment interaction of wearable textiles mainly include polytetrafluoroethylene (PTFE) hydrophobic membranes, polyurethane hydrophilic membranes and electrospun fiber membranes. At present, protective materials have become an urgent need to improve the comfort and wearability of long-term use while improving the barrier property. Functional and intelligently breathable and moisture permeable materials have also been studied, accelerating their application in medical, garment and military protective materials.
Since water molecules transport more slowly in solids than in pores, the waterproof and moisture permeability of the PTFE hydrophobic microporous membrane mainly comes from the regulation of its pore size. When the pore size is smaller than the raindrop but larger than the water vapor molecule, it has better waterproof and moisture permeability, but because the PTFE is hydrophobic, it will lead to the accumulation of water droplets in the pore channel blockage. The polyurethane hydrophilic membrane discharge water vapor molecules to the outside via the absorption-transfer-release process, which has high water pressure resistance due to its non-porous structure, so the permeability and moisture permeability are relatively poor, and the wearers will feel uncomfortable. Electrospinning, as a convenient and effective route to prepare micro/nanofiber membranes, has been developed rapidly in recent years. The electrospun fiber membrane is considered to be an effective material to prepare waterproof and breathable membranes because of its small pore size, high porosity, controllable porous structure and ease of surface modification. Until now, a variety of strategies such as biaxial stretching, formwork methods, and melt blowing have been used to produce microporous, waterproof and breathable membranes. However, due to the limitations of raw materials and processes, these methods are still difficult to industrialize in large quantities.
Although the research on the physical, chemical preparation and processing of waterproof and moisture permeable membranes has accumulated a lot of valuable results, the actual daily wearing environment is very complex, especially when switching between indoor and outdoor scenes, such as entering and exiting air-conditioned rooms in summer. The waterproof and moisture permeable fabric with undiversified "winter warmness" or "summer coolness" cannot adapt to the complex scene and even cause the medical staff to get cold and sick. Its poor adaptability greatly limits the practical application. Consequently, it is urgent to design and develop a smart textile with thermal/moisture dissipation in hot weather while offer a warm and humid microclimate in cold weather, which may accelerate the development and research on medical protective clothing and other related medical textiles.
Keywords:
waterproofing and moisture permeability; functional membranes; intelligent fabric; electrospun fiber membrane; protective property
收稿日期:20220805
網絡出版日期:20221104
基金項目:上海工程技術大學產學研項目((19)FZ-015);浙江省紗線材料成形與復合加工技術研究重點實驗室項目(MTC-2020-23)
作者簡介:仇慧麗(1998—),女,河南安陽人,碩士研究生,主要從事功能與智能材料設計與應用方面的研究。
通信作者:楊群,E-mail:yangqun@sues.edu.cn