陳海濤,竹筱歆,劉 爽
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水稻秸稈纖維基綠色地膜制造工藝參數(shù)優(yōu)化
陳海濤,竹筱歆,劉 爽
(東北農(nóng)業(yè)大學(xué)工程學(xué)院,哈爾濱 150030)
為改善水稻秸稈纖維基地膜的增溫性,該文研究了將水稻秸稈纖維基地膜由本色的乳白色改性為綠色的工藝參數(shù),闡明了主要影響因子對該染色地膜性能的影響規(guī)律。應(yīng)用五因素五水平正交旋轉(zhuǎn)中心組合的試驗方法,研究以秸稈纖維漿、染料、染料中亮藍(lán)占比、改性劑和濕強劑的質(zhì)量分?jǐn)?shù)對水稻秸稈纖維基地膜的透氣度、上染率、褪色率、干抗張力及濕抗張力等諸多指標(biāo)的影響。結(jié)果表明:當(dāng)選取工藝參數(shù)組合為秸稈纖維漿質(zhì)量分?jǐn)?shù)71%~79%、染料質(zhì)量分?jǐn)?shù)0.44%~0.53%、染料中亮藍(lán)占比90%、改性劑質(zhì)量分?jǐn)?shù)0.6%、濕強劑質(zhì)量分?jǐn)?shù)0.9%時,所得水稻秸稈纖維基綠色地膜的透氣度≤2m/Pa·s、上染率≥80%、褪色率≤8%、干抗張力≥40 N、濕抗張力≥16 N,可滿足水稻秸稈纖維基地膜水、旱田覆蓋栽培有機(綠色)作物技術(shù)要求。
地膜;秸稈;優(yōu)化; 染色;增溫性
農(nóng)用地膜覆蓋栽培技術(shù)以其保墑、保溫、增產(chǎn)的效用優(yōu)勢已成為中國農(nóng)業(yè)生產(chǎn)的主要種植模式。但因其很難在自然條件下進行光熱降解,殘膜會嚴(yán)重影響作物根系生長發(fā)育及土壤水肥運移,最終導(dǎo)致農(nóng)作物減產(chǎn)。從高效、優(yōu)質(zhì)和可持續(xù)發(fā)展的角度出發(fā),以水稻秸稈為主要原料制造的完全降解型環(huán)保纖維地膜,可實現(xiàn)秸稈科學(xué)還田、高值化利用,并能有效減輕農(nóng)田面源污染[1-3]。
然而其增溫性能還有待進一步提升,因纖維地膜為透光度較低的乳白色,白天太陽光中的紅外光較少射入膜內(nèi),降低了植物及土壤的熱量供給;又因纖維具有孔洞結(jié)構(gòu),當(dāng)大氣與膜內(nèi)溫度產(chǎn)生溫差,膜內(nèi)溫度較高時,會從膜內(nèi)向大氣散失熱量,導(dǎo)致地膜保溫性不理想[4-5]。
不同顏色地膜對太陽光線輻射的吸收與反射具有不同選擇性,可使土壤積溫變化不同。目前針對有色地膜在增溫性能方面的研究主要集中于塑料地膜,江蘇省農(nóng)科院汪興漢等[6]研究了波段770~850 nm的紅外光(太陽輻射波段中最熱的光線,亦稱熱線)對幾種有色地膜光熱效應(yīng)的影響,得出綠膜覆蓋對熱線反射率低、透射率高且變化幅度較小,吸收傳導(dǎo)效果最好。甘肅省農(nóng)科院張國平等[7]通過進行綠色全膜壟作實驗,發(fā)現(xiàn)綠色地膜能改善土壤蓄水能力,增加土壤溫度;周麗娜等[8]研究用不同顏色地膜栽種馬鈴薯,得出透明膜>綠色膜>黑色膜的增溫效果,且綠色地膜的秧苗素質(zhì)好、草害輕、增產(chǎn)7.0%~11.8%;閔翠華等[9]發(fā)現(xiàn),綠色地膜栽培的玉米長勢快、生育期短且單穗重高??梢姡G色地膜在促進土壤增溫增產(chǎn)上效果顯著。
有色塑料地膜是將有色母料加入聚乙烯樹脂中制成;而在植物纖維地膜染色方面,國內(nèi)外的研究較匱乏。常規(guī)紙張染色選用直接染料,但因其安全性及穩(wěn)定性差,不宜用于農(nóng)作物。天津制漿造紙重點實驗室曾研究將食用合成色素運用于食品包裝紙染色[10];史曉娟等[11]也在彩色紙漿鮮果托盤的創(chuàng)新研制中運用了食用合成色素。
食用合成色素安全環(huán)保、著色力強且成本低廉,為研究植物纖維基地膜增溫性能,本研究擬通過添加食用合成色素等功能助劑將呈乳白色的原膜改性為綠色[12-13]。研究分析秸稈纖維漿、染料、染料中亮藍(lán)占比、改性劑和濕強劑質(zhì)量分?jǐn)?shù)對顏色改變及纖維孔隙透氣度的影響,探索秸稈纖維基綠色地膜的最佳工藝參數(shù)組合。
試驗材料:秸稈纖維(東農(nóng)425水稻,2016年收獲),未漂硫酸鹽針葉木槳板;功能助劑:亮藍(lán)(食品級)、檸檬黃(食品級)、改性劑(主要成分為殼聚糖)、濕強劑(濃度15%)。
試驗設(shè)備:ZT4-00瓦利打漿機(中通試驗設(shè)備公司),ZJG-100打漿度測定儀、ZCX-A紙頁成型設(shè)備、ZL-3006擺錘式紙張抗張力測量儀器、紙張透氣度測量儀器(月明試驗裝置有限公司),YB502電子秤(精度0.01 g,??惦娮釉O(shè)備有限公司),DGG-9070AD恒溫電熱干燥箱(森信實驗設(shè)備有限公司),6010紫外-可見分光光度計(惠普分析設(shè)備有限公司),DC-P3全自動測色色差儀(興光測色設(shè)備有限公司),電子恒溫水浴箱(虞龍設(shè)備有限公司)。
以木漿纖維為骨架支撐,填充以秸稈纖維漿制造地膜試樣,基于預(yù)試驗結(jié)果選擇定量65 g/m2、打漿度(35±1)°SR。采用五因素五水平正交旋轉(zhuǎn)中心組合試驗方法,選擇影響秸稈纖維基地膜綠色效用的主要因素(相對于絕干漿的質(zhì)量分?jǐn)?shù))秸稈纖維漿、染料、改性劑、濕強劑及染料中亮藍(lán)占比(簡稱亮藍(lán)占比)為影響因子,透氣度、上染率、褪色率、干抗張力、濕抗張力為評價指標(biāo),因素水平編碼表如表1所示,試驗方案如表2。
表1 因素水平編碼表
將抄好的膜片在18℃室溫及30%~40%相對濕度的標(biāo)準(zhǔn)條件下靜置24 h,借鑒GB/T12914-2008“紙與紙板抗張力的測定”測試干、濕抗張力;借鑒 GB/T458-2008“紙與紙板透氣度的測定”進行透氣度換算,如公式(1)所示,每組試驗重復(fù)10次取平均值。
式中為透氣度,m/Pa×s;為一定時間內(nèi)通過膜片的氣體容積,mL;Δ為膜片兩側(cè)壓差,kPa;為測定時間,s。
根據(jù)朗伯-比爾定律[14]推導(dǎo)上染率及褪色率,每組試驗重復(fù)9次取平均值,如公式(2)、(3)所示。
式中0為原液吸光度;1為殘液吸光度;2為去離子水浸泡后溶液吸光度。
通過比較地膜的上染率和褪色率的大小,可以間接反映纖維對染料的吸附程度,也就是針對纖維素的直染性和親和性,應(yīng)用Design-Expert 6.0.10軟件進行數(shù)據(jù)分析[15]。
秸稈與針葉木漿板分別打漿?配漿并添加改性劑?濕法加入染料?加濕強劑?抄膜?烘干成型?性能指標(biāo)測定。
1)打漿。先分別將秸稈及針葉木漿按照GB/T24325 -2009“紙漿瓦利(valley)打漿機法”疏解制備,測出其濃度以備配漿時使用[16-17]。
2)配漿及改性。根據(jù)絕干漿定量,按照試驗方案中木漿與秸稈纖維漿比例進行混合,待漿料充分融合后加入改性劑并攪拌均勻。
3)上染。按方案將檸檬黃及亮藍(lán)進行配比形成染料,濕法加入染料及濕強劑,60 ℃恒溫上染45 min,控制pH值穩(wěn)定在6.0(根據(jù)上染牢固優(yōu)化條件[18-19])。
4)抄膜。參照GB/T24325-2009“紙漿瓦利(valley)打漿機法”進行壓膜、烘干,完成膜片制造。
試驗結(jié)果如表2所示。
表2 試驗方案與結(jié)果
對試驗結(jié)果進行分析,透氣度1、上染率2、褪色率3、干抗張力4、濕抗張力5的二次項模型有意義(<0.000 1),在置信度0.05下進行檢驗,剔除非顯著項,得各目標(biāo)函數(shù)回歸模型如式(4)~(8)所示。
對式(4)~(8)進行方差分析,結(jié)果如表3所示。
表3 回歸模型方差分析
由表4可知,每個指標(biāo)回歸項<0.05,說明回歸方程極顯著;擬合項的>0.05,說明模型擬合好。
2.3.1 透氣度影響規(guī)律
1)透氣度影響規(guī)律見圖1,秸稈纖維漿和染料的質(zhì)量分?jǐn)?shù)對透氣度的影響如圖1a所示。在染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,染料質(zhì)量分?jǐn)?shù)較高時,透氣度隨著秸稈纖維漿質(zhì)量分?jǐn)?shù)的增大而大幅度降低,染料質(zhì)量分?jǐn)?shù)較低時,透氣度隨著秸稈纖維漿質(zhì)量分?jǐn)?shù)的增加呈緩慢降低趨勢。因染料分子中含有大量-COOH、-OH等基團,能結(jié)合纖維素結(jié)構(gòu)上的氨基,形成氫鍵和范德華力作用,從而降低透氣度[20-21];而相較于木漿纖維,秸稈纖維細(xì)小且雜細(xì)胞較多,表面裸露的氨基基團能更均勻的與染料離子吸附成膜[22],所以透氣度呈下降趨勢,染料離子過少時效果不顯著,隨著染料離子增多,透氣度下降明顯。
通過圖1a可知,染料質(zhì)量分?jǐn)?shù)對透氣度的影響程度大于秸稈纖維漿質(zhì)量分?jǐn)?shù),透氣度最小值出現(xiàn)在染料質(zhì)量分?jǐn)?shù)0.9%、秸稈纖維漿質(zhì)量分?jǐn)?shù)90%。
注:圖a中染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%;圖b中秸稈纖維漿70%,染料質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%。
2)染料中亮藍(lán)占比和改性劑質(zhì)量分?jǐn)?shù)對透氣度的影響如圖1b所示。在秸稈纖維漿質(zhì)量分?jǐn)?shù)70%,染料質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,透氣度隨著染料中亮藍(lán)占比的增加而緩慢下降,亮藍(lán)占比90%以上時整體趨于平緩,因為亮藍(lán)的分子式為C37H34N2Na2O9S3,相比檸檬黃C16H10N2Na2O7S2帶有更多的伯氨基碳離子鍵,能吸附氫離子轉(zhuǎn)變成氨基正離子附著在纖維上,從而減小透氣度[23]。透氣度隨著改性劑的增加亦呈整體下降趨勢,當(dāng)改性劑質(zhì)量分?jǐn)?shù)為0.7%以上時趨于平緩,因改性劑的主要成分為殼聚糖,用掃描電鏡掃描木素導(dǎo)管管孔狀態(tài)時發(fā)現(xiàn),導(dǎo)管的管間紋孔上附著著一層膜狀纖維[24],從而降低了透氣度,達到飽和狀態(tài)時,變化趨于平穩(wěn)。
通過圖1b可知,最小值出現(xiàn)在染料中亮藍(lán)占比90%、改性劑質(zhì)量分?jǐn)?shù)0.7%。
2.3.2 上染率影響規(guī)律
1)上染率影響規(guī)律見圖2,改性劑和染料的質(zhì)量分?jǐn)?shù)對上染率的影響如圖2a所示。在秸稈纖維漿質(zhì)量分?jǐn)?shù)70%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,在染料質(zhì)量分?jǐn)?shù)較低時,上染率隨改性劑的增大而大幅度提高,因為改性劑的主要成分殼聚糖是甲殼素的脫乙?;a(chǎn)物,其構(gòu)成的基本單元為氨基葡萄糖,位于葡萄糖C2位置上的-OH被-NH2替代,殼聚糖分子中大量的-NH2成為染料的“基座”,滲透進纖維之間的縫隙里,促進溶解和拼色,從而保證了上色牢固持久,使上染率提高。當(dāng)染料質(zhì)量分?jǐn)?shù)較高時,上染率增幅趨緩,因為隨著染料質(zhì)量分?jǐn)?shù)的增加,水溶性的染料和纖維之間存在吸附與解吸共同作用,纖維逐漸達到飽和狀態(tài),解吸的染料滯留在殘液中,導(dǎo)致上染率漲幅趨緩[25-26]。
通過圖2a可知,改性劑對上染率的影響程度大于染料質(zhì)量分?jǐn)?shù),最大值出現(xiàn)在改性劑質(zhì)量分?jǐn)?shù)0.9%、染料質(zhì)量分?jǐn)?shù)0.1%。
2)秸稈纖維漿和改性劑的質(zhì)量分?jǐn)?shù)對上染率的影響
如圖2b所示。在染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,改性劑質(zhì)量分?jǐn)?shù)與上染率呈正相關(guān),隨著改性劑質(zhì)量分?jǐn)?shù)增多,上染率不斷增加。因為染液滲透進導(dǎo)管內(nèi)部,改性劑中的殼聚糖呈膜狀附著在導(dǎo)管的管間紋孔上[26],封鎖孔道起隔離作用,從而加強纖維固色。秸稈纖維漿質(zhì)量分?jǐn)?shù)與上染率亦呈正相關(guān),隨著秸稈纖維漿質(zhì)量分?jǐn)?shù)的增大,上染率逐漸提升,因為秸稈纖維漿中半纖維體積分?jǐn)?shù)為40%,而針葉木漿的半纖維素體積分?jǐn)?shù)僅為26%,半纖維素分子帶支鏈及自由基較多[27],是微細(xì)纖維與染料間的“填充劑”,秸稈纖維漿的增加致使半纖維素增加,對染料的附著力增加,所以上染率提升。
通過圖2b可知,改性劑對上染率的影響程度大于秸稈纖維漿,最大值出現(xiàn)在改性劑質(zhì)量分?jǐn)?shù)0.9%、秸稈纖維漿質(zhì)量分?jǐn)?shù)90%。
2.3.3 褪色率影響規(guī)律
1)褪色率影響規(guī)律見圖3,秸稈纖維漿和染料的質(zhì)量分?jǐn)?shù)對褪色率的影響圖3a所示。在染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù) 0.9%的條件下,染料質(zhì)量分?jǐn)?shù)較高時,褪色率隨秸稈纖維漿的增加而上升,因為秸稈纖維聚合度較低,約為12左右,且具有如甘露糖基和木糖基的基本單元[27],低聚合度纖維雖然與染料結(jié)合的概率大,但結(jié)合的不牢固且褪色快,致使褪色率上升,而纖維上結(jié)合的染料離子趨于飽和后,殘液中的染料亦導(dǎo)致褪色率上升;隨著染料質(zhì)量分?jǐn)?shù)的下降,褪色率變化幅度趨緩,因為有限的染料能充分與纖維結(jié)合,褪色率較低。
注: 圖a中秸稈纖維漿70%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%;圖b中染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%。
Note: In figure a straw fiber pulp 70%, brilliant blue proportion 80%, wet strength agent 0.9%; in figure b dye addition 0.5%, brilliant blue proportion 80%, wet strength agent 0.9%.
圖2 改性劑和染料以及秸稈纖維漿和改性劑的質(zhì)量分?jǐn)?shù)對上染率的影響
Fig.2 Effects of modifier addition and dye addition , straw fiber pulp and modifier addition on dye-uptake
通過圖3a可知,染料對褪色率的影響程度大于秸稈纖維漿質(zhì)量分?jǐn)?shù),最小值出現(xiàn)在染料質(zhì)量分?jǐn)?shù)0.1%、秸稈纖維漿質(zhì)量分?jǐn)?shù)50%。
2)染料中亮藍(lán)占比和改性劑質(zhì)量分?jǐn)?shù)對褪色率的影響如圖3b所示。在秸稈纖維漿質(zhì)量分?jǐn)?shù)70%、染料質(zhì)量分?jǐn)?shù)0.5%、濕強劑質(zhì)量分?jǐn)?shù)0.9%的基礎(chǔ)上,當(dāng)改性劑質(zhì)量分?jǐn)?shù)較低時,褪色率隨著染料中亮藍(lán)占比的增加,由高水平向低水平緩慢發(fā)展,因為亮藍(lán)比檸檬黃帶有更多的磺酸基(—SO3H),可與纖維素形成穩(wěn)固的離子鍵[28],使改性劑攜帶的染料穩(wěn)健的吸附于纖維的表面,導(dǎo)致褪色率下降。隨著改性劑質(zhì)量分?jǐn)?shù)的增加時,這種變化趨于平緩,因為在染色過程中,大量改性劑能有效的與吸附的染料和游離的染料發(fā)生反應(yīng)[29],亮藍(lán)的影響不再顯著,褪色率變化平緩。
通過圖3b可知,最小值出現(xiàn)在改性劑質(zhì)量分?jǐn)?shù)0.9%、染料中亮藍(lán)占比100%。
注:圖a中染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%;圖b中秸稈纖維漿70%,染料質(zhì)量分?jǐn)?shù)0.5%,濕強劑質(zhì)量分?jǐn)?shù)0.9%。
2.3.4 干抗張力影響規(guī)律
1)干抗張力影響規(guī)律見圖4,秸稈纖維漿和濕強劑的質(zhì)量分?jǐn)?shù)對干抗張力的影響如圖4a所示。在染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,干抗張力與秸稈纖維漿呈負(fù)相關(guān),隨著秸稈纖維漿質(zhì)量分?jǐn)?shù)的減少,干抗張力迅速增大,這是由于地膜膜片的抗張強度與單位面積的長纖維數(shù)量呈正比,隨著秸稈纖維漿質(zhì)量分?jǐn)?shù)減少,木漿纖維隨之增多,長纖維數(shù)量的增加有利于提升纖維之間的編織結(jié)合力;隨著濕強劑質(zhì)量分?jǐn)?shù)的增加,干抗張力呈緩慢增加,因為濕強劑提供的陽離子不斷與纖維表面攜帶的陰離子通過庫侖引力相互吸引[30],所以干抗張力增加。
通過圖4a可知,秸稈纖維漿對干抗張力的影響程度大于濕強劑質(zhì)量分?jǐn)?shù),最大值出現(xiàn)在秸稈纖維漿質(zhì)量分?jǐn)?shù)50%、濕強劑質(zhì)量分?jǐn)?shù)1.3%。
2)秸稈纖維漿和改性劑的質(zhì)量分?jǐn)?shù)對干抗張力的影響如圖4b所示。在染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%的條件下,干抗張力隨著秸稈纖維漿的增加呈現(xiàn)明顯下降趨勢,因為秸稈纖維漿中木素體積分?jǐn)?shù)一般為20%(相對于絕干漿),而針葉木漿木素含量約為30%,木素纖維形狀長、雜細(xì)胞少,未漂木漿中含有的木素酚-OH[27],能與改性劑中殼聚糖所含的-NH2形成離子鍵,從而有效提升干抗張力,所以隨著秸稈纖維漿的增加,降低了干抗張力;隨著改性劑的增加,漿料中殼聚糖的含量逐漸增大,殼聚糖分子中存在著許多氨基的親核基團[31],可以在木素纖維大分子鏈上發(fā)生鍵合,秸稈纖維漿質(zhì)量分?jǐn)?shù)較高時,呈增長趨勢,秸稈纖維漿質(zhì)量分?jǐn)?shù)較低時,改性劑中的殼聚糖先作用于纖維改性,再與木素酚基團結(jié)合,所以干抗張力先小幅度下降,再逐漸提升。
通過圖4b可知,秸稈纖維漿對干抗張力的影響程度大于改性劑質(zhì)量分?jǐn)?shù),最大值出現(xiàn)在秸稈纖維漿50%、改性劑質(zhì)量分?jǐn)?shù)0.9%。
注:圖a中染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%;圖b中染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,濕強劑質(zhì)量分?jǐn)?shù)0.9%。
2.3.5 濕抗張力影響規(guī)律
1)濕抗張力影響規(guī)律見圖5,改性劑和濕強劑質(zhì)量分?jǐn)?shù)對濕抗張力的影響如圖5a所示。在秸稈纖維漿質(zhì)量分?jǐn)?shù)70%,染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%的條件下,隨著改性劑和濕強劑由低水平到高水平的逐漸增大,濕抗張力亦逐漸增大。這是因為改性劑與濕強劑起到相輔相成的作用,改性劑中的殼聚糖呈現(xiàn)出弱的陽電性,濕強劑提供陽離子電荷,纖維分子中原有的-COOH在染液中發(fā)生了電離,所以纖維表面帶負(fù)電荷,它們通過庫侖力彼此吸引,編織在纖維分子長直鏈的四周[32];纖維素分子上的活性基團亦可以與殼聚糖形成鹽式鍵作用,附著于纖維的外表面和內(nèi)部的縫隙中,并能形成一層薄膜,降低液體對地膜纖維的潤濕作用,使?jié)窨箯埩υ黾印?/p>
通過圖5a可知,濕強劑對濕抗張力的影響程度大于改性劑,最大值出現(xiàn)在改性劑質(zhì)量分?jǐn)?shù)0.9%、濕強劑質(zhì)量分?jǐn)?shù)1.3%。
注:圖a中秸稈纖維漿70%,染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%
Note: 80%; 圖b中染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%。
Note: In figure a straw fiber pulp 70%, dye addition 0.5%, brilliant blue proportion; in figure b dye addition 0.5%, brilliant blue proportion 80%, modifier addition0.5%.
圖5 改性劑和濕強劑以及秸稈纖維漿和濕強劑的質(zhì)量分?jǐn)?shù)對濕抗張力的影響
Fig.5 Effects of modifier and wet strength mass fraction, straw fiber pulp and wet strength mass fraction on wet tensile strength
2)秸稈纖維漿和濕強劑質(zhì)量分?jǐn)?shù)對濕抗張力的影響如圖5b所示。在染料質(zhì)量分?jǐn)?shù)0.5%,染料中亮藍(lán)占比80%,改性劑質(zhì)量分?jǐn)?shù)0.5%的條件下,濕抗張力隨濕強劑質(zhì)量分?jǐn)?shù)的增加顯著提升,因為濕強劑的添加不僅保護了原有纖維間的結(jié)合,還能產(chǎn)生亞甲基醚鍵,這種新的抗水結(jié)合鍵限制了漿料的吸濕潤脹[33];濕抗張力亦隨秸稈纖維漿質(zhì)量分?jǐn)?shù)的降低呈上升趨勢。因為纖維遇水H鍵易斷裂,秸稈纖維漿質(zhì)量分?jǐn)?shù)越低,單位膜片面積上木素長纖維越多,H鍵結(jié)合越牢固,所以濕抗張力越大。
通過圖5b可知,濕強劑對濕抗張力的影響程度大于秸稈纖維漿質(zhì)量分?jǐn)?shù),濕強劑質(zhì)量分?jǐn)?shù)1.3%、最大值為秸稈纖維漿質(zhì)量分?jǐn)?shù)50%。
為滿足水稻秸稈纖維基地膜水、旱田覆蓋栽培有機(綠色)作物技術(shù)要求,干抗張力≥40 N、濕抗張力≥16 N,上染率≥80%,褪色率≤8%,透氣度≤2m/Pa·s;并以節(jié)省資源、降低成本為原則,優(yōu)化分析結(jié)果如圖2-11所示。
注:染料中亮藍(lán)占比90%,改性劑質(zhì)量分?jǐn)?shù)0.6%,濕強劑質(zhì)量分?jǐn)?shù)0.9%
由圖6可知,工藝參數(shù)優(yōu)化組合為:當(dāng)染料中亮藍(lán)占比90%、改性劑質(zhì)量分?jǐn)?shù)0.6%、濕強劑質(zhì)量分?jǐn)?shù)0.9%時,秸稈纖維漿質(zhì)量分?jǐn)?shù)71%~79%、染料質(zhì)量分?jǐn)?shù)0.44%~0.53%。
按最優(yōu)工藝結(jié)果完成定量65 g/m2、秸稈纖維漿質(zhì)量分?jǐn)?shù)75%、染料質(zhì)量分?jǐn)?shù)0.5%、染料中亮藍(lán)占比90%、改性劑質(zhì)量分?jǐn)?shù)0.6%、濕強劑質(zhì)量分?jǐn)?shù)0.9%的秸稈纖維基綠色地膜試樣(簡稱綠膜樣片)。測試各項性能指標(biāo)取平均值,并與原質(zhì)秸稈纖維基地膜(簡稱原膜樣片,不添加染料及改性劑)作性能對比如表4所示。
由表4中數(shù)據(jù)可得:綠膜的透氣度為1.9m/Pa×s、干抗張力為44.2 N、濕抗張力為17.9 N、上染率為80.5%、褪色率為7.6%,均達到地膜田間鋪設(shè)實用性能要求,表明優(yōu)化結(jié)果正確可信。對比可得,綠膜的透氣度比原膜降低了43.9%,透氣度的減小利于減少膜內(nèi)熱量散失;綠膜的熱線透射率比原膜提升25.7%~33.3%,有利于土壤及農(nóng)作物增溫。
表4 2種秸稈纖維基地膜性能對比
1)各因素(相對于絕干漿質(zhì)量分?jǐn)?shù))對透氣度影響貢獻率大小排序為:染料、改性劑、染料中亮藍(lán)占比、秸稈纖維漿、濕強劑;對上染率影響貢獻率大小排序為:改性劑、染料、秸稈纖維漿、染料中亮藍(lán)占比、濕強劑;對褪色率影響貢獻率大小排序為:染料、染料中亮藍(lán)占比、秸稈纖維漿、改性劑、濕強劑;對干抗張力影響貢獻率大小排序為:秸稈纖維漿、改性劑、染料、濕強劑、染料中亮藍(lán)占比;對濕抗張力影響貢獻率大小排序為:濕強劑、秸稈纖維漿、改性劑、染料、染料中亮藍(lán)占比。
2)工藝參數(shù)優(yōu)化組合為秸稈纖維漿質(zhì)量分?jǐn)?shù)71%~79%、染料質(zhì)量分?jǐn)?shù)0.44%~0.53%、染料中亮藍(lán)占比90%、改性劑質(zhì)量分?jǐn)?shù)0.6%、濕強劑質(zhì)量分?jǐn)?shù)0.9%,此時,水稻秸稈纖維基綠色地膜透氣度≤2m/Pa×s、上染率≥80%、褪色率≤8%、干抗張力≥40 N、濕抗張力≥16 N,且經(jīng)試驗驗證滿足此條件。按此工藝參數(shù)制造的水稻秸稈纖維基地膜可滿足水、旱田覆蓋栽培有機(綠色)作物技術(shù)要求,增加了熱線透射率、減小了透氣度,進一步改善了增溫、保溫和保墑性能,為水稻秸稈纖維基地膜的推廣應(yīng)用奠定了基礎(chǔ)。
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Optimization of technical parameters for rice straw fiber-based mulch
Chen Haitao, Zhu Xiaoxin, Liu Shuang
(150030,)
The long term use of farmland plastic mulching not only brings us economic benefit, but also brings the hidden danger of pollution. Residual film existing in the soil will affect the growth and development of crop root and the transfer of water-fertilizer, and meanwhile will lead to the crop yield reduction. By using rice straw as the main raw material, the straw fiber mulch can achieve green (organic) cultivation and scientific straw returning to the field, and reduce agricultural non-point source pollution effectively. However, the characteristics of increasing temperature in soil need to be further improved, since the fiber mulch is milky and transmittance is low, into which the infrared in the daytime sunlight less streamed, leading to plants and soil heat reduction. When there exists the difference between atmosphere and intramembranous temperature, the heat will dissipate if the temperature is high in the straw fiber film, which leads to the thermal insulation performance not ideal. In order to improve the deficiency of temperature increasing of straw fiber mulch, and make it have a better practicability to replace the plastic mulching in an all-round way, the technology parameters of staining the milky straw fiber mulch to green were studied, and the solar hot light transmittance was increased and the soil temperature loss was further reduced by adding environmental protection functional additive to decrease the air permeability of the fiber mulch. The five-factor and five-level quadratic regression orthogonal rotation center combined method was applied. Functional additive is added at a constant temperature of 60℃for 45 min in the wet process of dyeing, and mixed thoroughly until it is completely combined, and the pH value of fiber pulp is controlled to be stable at 6.0. Using the wood pulp fibers to build skeleton, and adding rice straw fiber as the main filling material, supplemented by safe and environmental protection synthetic food dyes, such as lemon yellow and brilliant blue dye, the straw fiber pulp, dye addition, brilliant blue proportion, modifier addition and the mass fraction of wet strength agent as influence factors were studied, as well as the air permeability, dye uptake, fading rate, dry tensile strength and wet tensile strength as the performance evaluation indices. The optimal technology parameters of green straw fiber mulch were determined as follows: rice straw fiber pulp addition amount of 71%~79%, dye addition of 0.44%~0.53%, proportion of the brilliant blue of 90%, modifier addition of 0.6%, and the wet strength agent addition of 0.9%. Under such an optimized combination, we come up with a result in the evaluation of the indicators: The air permeability is lower than 2m/Pa·s, the dye uptake is higher than 80%, the fading rate is lower than 8%, the dry tensile strength is more than 40 N and the wet tensile strength is more than 16 N, which can meet the technical requirements of the cultivation of organic (green) crops field through covering the rice straw field mulch, and the hot light transmittance will increase and the air permeability will decrease, which will further improve the performance of heat preservation and moisture conservation.
straw; fibers; optimization; dyeing; temperature-increasing property
陳海濤,竹筱歆,劉 爽. 水稻秸稈纖維基綠色地膜制造工藝參數(shù)優(yōu)化 [J]. 農(nóng)業(yè)工程學(xué)報,2018,34(7):271-279. doi:10.11975/j.issn.1002-6819.2018.07.035 http://www.tcsae.org
Chen Haitao, Zhu Xiaoxin, Liu Shuang. Optimization of technical parameters for rice straw fiber-based mulch[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(7): 271-279. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2018.07.035 http://www.tcsae.org
2017-12-07
2018-03-15
“十二五”科技支撐計劃課題“秸稈基農(nóng)用膜成型工藝與設(shè)備研究”(2012BAD32B02-5)
陳海濤,教授,博士生導(dǎo)師,主要從事生物質(zhì)材料技術(shù)裝備和旱作農(nóng)業(yè)裝備技術(shù)方向的研究。Email:htchen@neau.edu.cn
10.11975/j.issn.1002-6819.2018.07.035
S216
A
1002-6819(2018)-07-0271-09