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PVFM負壓滲水材料的研制探究

時間:2016-03-19 來源:未知 作者:學術堂 本文字數:5005字

本篇論文目錄導航:

  【題目】PVFM負壓滲水材料的研制探究
  【第一章】PVFM負壓滲水材料制備與性能分析緒論
  【第二章】PVFM材料與方法
  【第三章】原料配比對PVFM負壓滲水性能的影響
  【第四章】不同反應條件對PVFM負壓滲水性能的影響
  【第五章】不同助劑對PVFM負壓滲水性能的影響
  【第六章】物理規格對PVFM負壓滲水性能的影響
  【總結/參考文獻】制備PVFM負壓滲水材料的可行性研究總結與參考文獻

摘 要

  負壓灌溉是一種根據作物對水分的需要適時灌水的節水灌溉方式。負壓灌溉系統中通常有儲水水源、控壓閥、負壓連接管、灌水器四個部分組成,其中灌水器處于水土界面,是直接與土壤和作物根系接觸的部分,對整套裝置的高效運行起著至關重要的作用。前人對于負壓灌溉的研究較少,對于負壓灌水器的探索方面也步履緩慢,其研究領域主要集中在無機陶土陶瓷類材料,但是他們易碎、韌性差、價格較高,不適合大面積推廣。

  查閱文獻資料發現,高分子材料中有一類微孔發泡材料,按照孔隙是否連通分為開孔型和閉孔型,而我們需要的負壓滲水器材料應當是微米級別的、開孔的微孔結構。若孔徑太小,滲水速率會降低,孔徑過大毛管吸力作用小,無法達到較高的發泡點值。經過篩選發現一種親水性高的微孔泡沫塑料——聚乙烯醇縮甲醛泡沫塑料(PVFM),它是由聚乙烯醇(PVA)與甲醛縮醛化而成,其柔韌性高、有可調的微孔結構、較好的滲透水性能。本試驗在此基礎上進一步將 PVFM 進行改良,對自行設計制備出的 PVFM 進行孔徑分布、發泡點、拉伸強度、硬度、在土壤中累積入滲量、滲水速率、濕潤峰運移等指標的測試,以研究不同配比、反應條件、助劑、規格對所制 PVFM負壓滲水性能的影響,闡明其制備成負壓滲水材料的可行性。經過研究分析,本文得到以下主要結論:

  (1)原料配比對 PVFM 的性能有影響。當水比例為 8.75 時表觀密度最小、吸水倍率最大。9 種不同配比的 PVFM 樣品發泡點值在 26.7~73.3kPa 之間變化,且在水比例 7.50 或者甲醛比例0.75 時會達到較高水平。在-5kPa 與-10kPa 下,水比例≥7.50 的 PVFM 樣品,滲水速率相對較快。PVA:水:甲醛為 1:7.50:0.75 的 5 號 PVFM 樣品的平均孔徑小,發泡點值為 65.3kPa,飽和導水率可達 7.45×10-4cm?s-1,理論上可以作為高性能負壓滲水材料在負壓灌溉中使用。

  (2)反應條件對 PVFM 的性能有影響。反應溫度 55℃、反應時間≥10h 時,表觀密度、吸水倍率、孔隙率均有較高表現,并且三者分別在攪拌機轉速 2000r?min-1、1500r?min-1、1000r?min-1時達到最高;反應溫度 55℃時,或者反應時間≥10h,或攪拌機轉速≤1500 r?min-1,發泡點值及對土壤的供水速率較高;綜合對比分析,反應溫度 55℃、反應時間 10h、攪拌機轉速為 1500 r?min-1的樣品,發泡點與負壓下的累積入滲量同時達到較高水平,物理性能也較好,因此確定為制備負壓滲水材料的最佳反應條件。

  (3)不同助劑的加入對 PVFM 各性能有不同程度的影響。助劑的加入使吸水倍率下降,使發泡點、表觀密度、孔隙率升高,使 PVFM 的機械性能、累積入滲量有不同程度的升高或降低。

  綜合看來,硅油與高嶺土混合加入使表觀密度和孔隙率有較大提高,對于硬度、拉伸強度、斷裂伸長率也有增強,尤其對發泡點值提升最明顯,對入滲量的增強上則表現一般,總體表現優于其他助劑。

  (4)滲水器規格對 PVFM 滲水器的負壓滲水性能有影響。空心 PVFM 滲水器的負壓滲水性能優于實心,實心 PVFM 滲水器的累積入滲量與其長度負相關。15×3cm 空心 PVFM 滲水器的負壓滲水性能優于陶瓷頭,不同負壓下,其相同時間內單位面積累積入滲量均高于陶瓷頭,土壤水分運移也要快,且能控制比陶瓷頭更大的土壤水分空間。在低吸力階段 15×3cm 空心 PVFM 滲水器所確定的土壤水吸力隨土壤含水量的變化關系與陶瓷頭幾乎一致,可以代替陶瓷頭進行土壤水分特征曲線的測定。在適宜常見作物生長的-5~-10kPa 范圍內,15×3cm 空心 PVFM 滲水器比陶瓷頭更易滿足作物對水分的需求。

  關鍵詞:聚乙烯醇縮甲醛(PVFM),微孔材料,制備,負壓滲水性能,負壓灌溉

Abstract

  Negative pressure irrigation is a water-saving irrigation mode for timely irrigation, according to thewater needs of the crop. Negative pressure irrigation system usually consists of water storage, waterpressure control valve, negative pressure connection pipe, and emitter. Emitter is at the water-soilinterface, which directly contacts with the soil and crop root. It plays a vital role in efficient operation ofthe entire device. The former researches on the negative pressure irrigation are less, the exploration forthe emitter is slow. Their researches are mainly focused on inorganic clay or ceramic materials, whichare fragile, poor toughness, higher prices, not suitable for large area promotion.

  Through cross boards researching, there is a kind of microcellular foam materials of polymermaterials. It can be divided into the open cell foam and closed cell foam according to the connectivity ofthe pores. However, the micron level and open pores are what we need. If the pore size is too small,seepage rate would be slow. If the pore size is too large, the capillary attaction would be so small thatcould not reach a higher bubble point. A kind of hydrophilicity microcellular foam plastics -- polyvinylformal foam (PVFM) was found after screening. It was made by acetalation of polyvinyl alcohol (PVA)and formaldehyde, had soft, high toughness, adjustable pore structure, and good water permeabilityperformance. In this research, PVFM was improved on this basis. Pore size distribution, bubble point,tensile strength, hardness, accumulate in the soil infiltration capacity, infiltrationrate, wetting fronttransportation were tested, so that the effects of reaction conditions, additives, specifications for PVFMcould be studied, then expounded the feasibility of making PVFM into negative permeability materials .

  The main conclusions of the paper are following:

  (1)The performance of PVFM could be affected by the ratio of raw materials. Apparent densityreached a minimum and water absorbency reached a maximum when H2O ratio was 8.75. Bubble pointwas largely different between, maximum of 73.3 kPa when the ratio was 1:7.50:0.50 and minimum of26.7 kPa when the ratio was 1:8.75:0.50. Generally, the bubble point could reach a high level at H2Oratio of 7.50 or formaldehyde ratio of 0.75. Under -5kPa and -10kPa, water exudation rate was higherwhen H2O ratio was larger than 7.50. In theory, the PVFM with PVA: H2O: formaldehyde ratio of1:7.50:0.75, whose mean pore size was small, bubble point was 65.3kPa, saturated hydraulicconductivity was 7.45×10-4cm?s-1, could be used as a novel negative pressure seepage material innegative pressure irrigation.

  (2)PVFM performance could be affected by the reaction conditions. Apparent density, waterabsorbency, porosity had a higher performance, When the reaction temperature was 55℃, reaction timewas no less than 10h, and mixer speed was at 2000r?min-1,1500r?min-1, 1000r?min-1respectively. Bubblepoint and the rate of soil water reached a high level when the reaction temperature was 55℃, or reactiontime was no less than 10h, or mixer speed was no more than 1500 r.min-1.In summary, bubble point andcumulative infiltration would reach a high level when the reaction temperature was 55℃, reaction timewas 10h, mixer speed was1500 r?min-1,while physical performance was also excellent under these condition. So this condition could be the best reaction condition for preparing PVFM.

  (3)Different additives had different effects on the performance of PVFM. On the one hand, theabsorption rate showed a decreasing trend and the bubble point, apparent density and the porosityshowed an increasing trend. On the other hand, mechanical properties and cumulative infiltration ofPVFM showed a decreasing or increasing trend in different extent. Taken together, silicone oil andkaolin together could enhance obviously the apparent density and porosity. At the same time, they couldalso improve the hardness, tensile strength and break elongation, especially bubble point. However, itwas not obvious that silicone oil and kaolin improved infiltration. In general, performance of silicone oiland kaolin was better than that of other additives.

  (4)The performance of PVFM cups could be affected by physically specifications. Negativepressure seepage capacity of hollow PVFM was better than the solid. Increasing the length of solidPVFM has a negative influence on the cumulative infiltration. Negative pressure seepage capacity of15×3cm hollow PVFM were more excellence than Ceramic cup. Under various negative pressures, thecumulative infiltration per unit area of hollow PVFM cup were higher, and soil water transported muchfaster in the same time. A broader soil moisture space can be controlled by hollow PVFM cup than byCeramic cup. The moisture characteristic curve determined with PVFM cup was similar to Ceramichead. So, hollow PVFM could be used to determine soil water characteristic curve. 15×3cm hollowPVFM could more easily satisfy the crop demand for water under -5~-10kPa which was suitable forcrop growth.

  Key words: Poly vinyl formal (PVFM); Microcellular materials; Preparation; Negative permeability;Negative pressure irrigation

  目 錄

  第一章 緒論
      1.1 研究背景及意義
      1.2 負壓滲水器概述
          1.2.1 負壓滲水器材料的基本特點
          1.2.2 負壓滲水器的作用原理
          1.2.3 負壓滲水材料的研究進展
      1.3 高分子材料簡介
          1.3.1 微孔發泡高分子材料概念及特性
          1.3.2 微孔發泡高分子材料研究進展
      1.4 PVFM 材料簡介及研究進展
          1.4.1 PVFM 簡介
          1.4.2 PVFM 研究進展
          1.4.3 PVFM 制備的影響因素
      1.5 研究契機
      1.6 研究目標
      1.7 研究內容
      1.8 技術路線
  第二章 材料與方法
      2.1 PVFM 材料的制備
          2.1.1 試劑與儀器
          2.1.2 樣品制備
          2.1.3 測試與表征
      2.2 對滲水器供水性能的測試——土柱實驗
          2.2.1 供試土壤
          2.2.2 不同負壓下累積入滲量、滲水速率、土壤含水量的測定
          2.2.3 不同負壓下濕潤峰的觀測
  第三章 原料配比對 PVFM 負壓滲水性能的影響
      3.1 試驗設計
      3.2 結果與分析
          3.2.1 配比對 PVFM 樣品外觀質量的影響
          3.2.2 配比對 PVFM 樣品基本物理性能的影響
          3.2.3 配比對 PVFM 樣品孔隙結構的影響
      3.3 討論
      3.4 小結
  第四章 不同反應條件對 PVFM 負壓滲水性能的影響
      4.1 試驗設計
      4.2 結果分析
          4.2.1 不同反應條件對表觀密度、吸水倍率、孔隙率的影響
          4.2.2 不同反應條件對發泡點及供水速率的影響
          4.2.3 不同反應條件下四種 PVFM 樣品性能的比較
      4.3 討論
      4.4 小結
  第五章 不同助劑對 PVFM 負壓滲水性能的影響
      5.1 試驗設計
      5.2 結果分析
          5.2.1 不同助劑對 PVFM 基本物理性能的影響
          5.2.2 不同助劑對 PVFM 機械性能的影響
          5.2.3 不同助劑對 PVFM 負壓滲水性能的影響
      5.3 討論
      5.4 小結
  第六章 物理規格對 PVFM 負壓滲水性能的影響
      6.1 試驗設計
          6.1.1 參與實驗的滲水器規格
          6.1.2 觀測項目
      6.2 結果分析
          6.2.1 一維條件下 PVFM 滲水器與陶瓷頭滲水性能的比較
          6.2.2 三維條件下較優 PVFM 與陶瓷頭在不同負壓下的濕潤峰運移狀況
      6.3 討論
      6.4 小結
  第七章 全文總結與展望
      7.1 全文主要結論
      7.2 創新點
      7.3 展望
  參考文獻
  附 錄
  致 謝

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