【作者】 张其斌；

【导师】 郑强； 宋义虎；

【作者基本信息】 浙江大学 ， 材料加工工程， 2008， 博士

【摘要】 废弃塑料对环境造成的“白色污染”日益严重，已经危及人类健康、生存和可持续发展。生物可降解材料的研究、开发和产业化，成为21世纪的重要课题之一。由于来源丰富，小麦蛋白质作为可再生资源制备生物可降解的环境友好材料，成为新兴的备受关注课题。本文以小麦谷朊粉（贮藏蛋白）为主要原料，制备谷朊粉／甘油、谷朊粉／淀粉／甘油、谷朊粉／富谷蛋白组分／甘油、谷朊粉／纤维素／甘油等蛋白质复合物，深入研究了增塑剂含量、模压温度、酸碱性、填料等对增塑小麦蛋白质或小麦蛋白质塑料（复合材料）的流变行为与力学性能的影响，并考察了碱性谷蛋白水性醇溶液的流变行为。采用高温模压法制备了甘油增塑小麦蛋白质塑料。发现，增塑剂甘油显著影响蛋白质塑料的力学性能。随增塑剂含量增高断裂强度与杨氏模量降低，断裂伸长率增大。蛋白质塑料的吸水性主要取决于甘油含量，随增塑剂含量增高吸水平衡时间与平衡吸水率提高。研究了酸、碱对小麦蛋白质塑料的流变行为与单／双轴力学性能的影响。结果表明，常温下，酸、碱均促进蛋白质交联反应，使储能模量（G’）与损耗模量（G″）增大。与碱性试样相比较，酸性试样初期交联速率较高，tanδ随酸含量增大而降低，随碱含量增大而升高；特征松弛时间（τ_c）随酸含量增大而向短时区域移动，随碱含量增大而向长时区域移动，表明加入酸使体系弹性增大为主，加入碱使体系黏性增大为主。此外，还发现酸可略微提高80℃模压体系的杨氏模量（E_U）与断裂强度(σ_br)，而碱可显著提高80℃模压体系E_U与σ_br。加入酸可降低110℃模压体系的交联密度，使E_U与σ_br略有降低，而含量低于1wt％的碱可显著提高使E_U与σ_br;碱含量过大时，蛋白质降解导致E_U与σ_br减小。模压温度从80℃升到110℃，谷朊粉塑料E_U、σ_br与ε_br均所有提高。采用热压法和冷压法制备了谷朊粉／淀粉／甘油塑料。结果表明，G’与G″均随淀粉含量增高而增大。复合体系在升温过程中出现橡胶平台，但淀粉仅起填料作用不发生凝胶化。淀粉的加入却使大应变下拉伸应力显著降低。另一方面，含水量显著影响复合材料的力学性能。过量水分在淀粉粒子与蛋白质网络间起着润滑作用，降低分子间作用力，致使其强度下降。从谷朊粉分离得到富谷蛋白组分。研究了谷朊粉／富谷蛋白组／甘油共混体系的流变行为和力学性能。结果表明，随富谷蛋白组分含量增大，混体系G’、G″与E_B增大，tanδ降低，在低频区域逐渐出现“第二平台”，特征松弛时间（τ_c）缩短，且交联速率和交联密度均显著增大。含醇溶蛋白时，试样先后出现应变软化与应变硬化行为，而不含醇溶蛋白的试样未出现应变软化行为，在应变硬化行为过程中发生破裂。随富谷蛋白组分含量增加，高温模压试样E_U增大，σ_br与ε_br降低，表明醇溶蛋白对小麦蛋白质塑料大变形能力有着决定性作用。采用热压法制备了谷朊粉／甲基纤维素／甘油复合材料料，研究了其流变行为与力学性能。结果表明，随纤维素含量增高，G’、G″、E_U与σ_br增大，tanδ与ε_br降低，玻璃化温度（T_g）升高，而随甲基纤维素含量增高，模压交联材料的G’与G″在低频区逐渐呈现“第二平台”，且tanδ出现峰值，表明纤维素-蛋白质相互作用使纤维素起到物理交联的作用。用碱性乙醇溶液制备了谷蛋白溶液，其流变行为结果表明，48mgml^-1碱性谷蛋白溶液常温下呈现弱非牛顿流体行为，其零切黏度为η₀=0．0237Pa·s，无限剪切黏度η_∞=0．0125Pa·s，剪切变稀指数n=0．931。随浓度降低，溶液牛顿流体特性增强。热处理温度显著影响谷蛋白溶液的稳态流变特性。热处理温度从30℃升高至90℃时，溶液黏度降低，剪切变稀现象减弱。加入Na⁺后，溶液黏度降低，剪切变稀现象减弱。Ca²⁺显著影响谷蛋白溶液的稳态与动态流变特性。Ca²⁺浓度为0．2M时，溶液黏度、屈服应力与低频区域的平台模量最大。更多还原

【Abstract】 The increasing pollution from nondegradable plastic wastes have directly threatened human being’s survival, health and development. Biodegradable materials thus are desired and their study and application grow rapidly in this century. Wheat proteins show the advantage for usage as biodegradable materials because of their abundant resource and good biodegradability.In this dissertation, wheat gluten （storage proteins） is used as matrix to prepare glycerol plasticized gluten bioplastic, and gluten/starch, gluten/glutenin-rich fraction and gluten/methylcellulose biocomposites. Influences of plasticizer content, compression temperature, acid or alkali treatment and filler type and content on rheological behaviors and mechanical properties are investigated. Rheological behaviors of alkaline ethanol soluble glutenin solution are also investigated.Glycerol plasticized wheat gluten bioplastics were prepared through compression molding. The results show that the glycerol content significantly affects the mechanical properties of the bioplastics. Young’s modulus and tensile strength decrease while elongation at break increases with increasing glycerol content. The moisture absorption of the bioplastics strongly depends on the glycerol content.Acid and alkali effects on rheological behaviors and biaxial/uniaxial extensional deformation of wheat gluten bioplastics were studied. The results show that addition of both HCl and NaOH facilitate cross-linking of proteins through thiol-disulfide interchange reaction, resulting in higher dynamic storage modulus （G’） and dynamic loss modulus （G″） at room temperature. At the earlier stage, HCl promotes the crosslinking reaction more than NaOH. Loss factor （tanδ） decreases with increasing HCl content while it increases with increasing NaOH content. The characteristic relaxation time from biaxial deformation decreases with increasing HCl content while it increases with increasing NaOH content, indicating that HCl improves elasticity of composites and NaOH mainly improves viscosity. HCl does not show catalysis function for crosslinking proteins at 80℃and even hinders the crosslinking reaction at 110℃. On the other hand, NaOH generally accelerates the crosslinking reaction during compression-molding thus improves Young’s modulus, tensile strength and strain at break significantly. However, NaOH with a content above 0.5 wt % could cause an adverse effect at molding temperature as high as 110℃. E_U,σ_br andε_br of the bioplastics are significantly increased as increasing molding temperature from 80℃to 100℃.Glycerol plasticized gluten/starch biocomposites were prepared using thermal and cold molding process. For the samples with 10 % moisture, G’ increases while tensile strength and elongation at break decrease with increasing starch content. Temperature scan reveals a "rubber plateau" above 100℃. The plasticized gluten exhibits gel-like behavior at 30℃while it forms a network at 80℃. For the samples with 20 % and 25 % moisture, their tensile strength and elongation at break decrease with increasing starch content, which is ascribed to the dilution and lubrication between starch granule and gluten network by moisture.Glutenin-rich fraction was extracted from wheat gluten using a modified method. Dynamic rheological behaviors and mechanical properties of glycerol plasticized gluten/glutennin-rich fraction biocomposites were studied. The results show that the crosslinking reaction is accelerated with increasing glutenin-rich fration content. The composites exhibited "second plateau" due to the formation of crosslinking network. Samples containing gliadin exhibit strain softening and strain hardening. However, upon removing gliadins, the samples do not exhibit strain softening but fractures during strain hardening. Increasing glutenin-rich fraction content improves Young’s modulus and tensile strength but lowers extensibility, indicating that gliadins are highly important for large deformation properties.Glycerol plasticized wheat gluten/methylcellulose biocomposites were prepared by thermal compression molding at 110℃. The results show that G’, G″, E_U,σ_brr and T_gincrease while tanδandε_br decrease with increasing methylcellulose content. Appearance of "second plateau" in the low frequency region reflects the formation of physical crosslinking between methylcellulose and proteins. Rheological behaviors of glutenins in 50 % （v/v） alcohol / water and 0.1 NaOH solutions were investigated in relation to glutenin concentration, thermal treatment temperature, sodium （Na⁺） and calcium (Ca²⁺) ionic strength. Glutenin solutions of 48 mg ml^-1 behave as weak nonNewton liquids with slight shear thinning, which has a zero shear viscosityη₀=0.0237 Pa·s, infinite shear viscosityη_∞=0.0125 Pa·s and shear thinning index n=0.931. The solutions approach newtonian behavior concentration is decreased. The solutions preheated at 30℃-90℃show low viscosity and weakened shear thinning. Addition of Na⁺ also lowers viscosity and weakens the shear thinning. Addition of Ca²⁺ has an obvious effect on rheological behavior of gliutenin solutions. The solution with 0.2 M Ca²⁺ shows the highest viscosity, yielding stress and low-frequency plateau modulus.更多还原