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本文研究了添加甘油对疏水改性木薯淀粉膜力学性能及阻隔性能的影响,甘油的添加降低了疏水改性淀粉膜的玻璃转化温度、储能模量及水蒸气透过量。当温度低于临界温度上限时,疏水改性淀粉将会出现固态及液态两种形式。热的淀粉溶液中加入适量的甘油可以抑制淀粉微粒的沉淀。与羟丙基淀粉相比,疏水改性淀粉中添加不同量的甘油并涂覆于基材表面,对基材的阻隔性、水蒸气透过量、接触角及可勃吸水值均有一定影响。从表面施胶基材的可勃吸水值和水蒸气透过量的变化上可以看出,淀粉的成膜性对基材的性能有非常重要的影响。良好的成膜性可以改善基材的阻气、阻湿性,而对基材表面润湿性的影响不大。随着甘油含量的逐渐增加,基材的水蒸气透过量不断减少;但仍无法得到较好的阻湿性能。本文中所用的疏水改性淀粉具有较好的氧气阻隔性能和接触角,因此,表面施胶后的基材具有较好的疏水特性。同时在实验条件下研究了淀粉沉淀对基材性能的影响,利用淀粉沉淀对基材表面进行施胶后即使淀粉成膜性较差,也可以得到较低的水蒸气透过量和较高的接触角。通过增加疏水改性淀粉中甘油的含量,表面施胶基材的可勃吸水值可以得到显著改善。
In this paper, the effects of glycerol addition on the mechanical properties and barrier properties of hydrophobically modified tapioca starch films were studied. The addition of glycerol reduced the glass transition temperature, storage modulus and water vapor transmission rate of hydrophobic modified starch films. When the temperature is lower than the upper limit of the critical temperature, hydrophobic modified starch will appear in both solid and liquid forms. Hot starch solution by adding an appropriate amount of glycerol can inhibit the precipitation of starch particles. Compared with hydroxypropyl starch, adding different amount of glycerin to the hydrophobically modified starch and applying it on the surface of the substrate will affect the barrier properties of the substrate, the amount of water vapor transmission, the contact angle and the water absorption value. It can be seen from the change of the water absorbency and the water vapor permeability of the surface sizing substrate that the filming property of the starch has a very important influence on the properties of the substrate. Good film-forming properties can improve the substrate gas barrier, moisture resistance, and the substrate surface wetting little effect. With the gradual increase of glycerol content, the water vapor transmission rate of the substrate decreased continuously; however, better moisture retention capacity could not be obtained. Hydrophobically modified starch as used herein has good oxygen barrier properties and contact angle, so the surface sizing of the substrate has better hydrophobic properties. At the same time, the influence of starch precipitation on the properties of the substrate was studied under the experimental conditions. Even if the starch film-forming ability is poor after the substrate surface is sizing with starch precipitation, the water vapor transmission rate and the higher contact angle. By increasing the amount of glycerol in the hydrophobically modified starch, the surface waterblown substrate can have a significant improvement in its waterbobble value.