本文選題：熱塑性淀粉 + 明膠��； 參考：《湖北工業(yè)大學(xué)》2017年碩士論文

【摘要】：淀粉是種來源廣泛價格低廉的天然高分子,具有較高的結(jié)晶度(20%~45%),淀粉分子之間氫鍵作用強,限制了分子鏈的運動,因此淀粉不具備熱塑性加工的性能。通過添加小分子的增塑劑,升溫和混煉的外界物理因素下,可制備熱塑性淀粉材料。但是,熱塑性淀粉存在著阻隔性能和機械性能不足,限制其單獨作為材料使用。本試驗以馬鈴薯淀粉為原料,丙三醇(甘油),碳酰胺(尿素)為增塑劑、明膠為黏合劑,卡拉膠為增強劑,制備熱塑性淀粉(Thermoplastic Starch,TPS)。借助于掃描電子顯微鏡觀察,旋轉(zhuǎn)流變儀分析熱塑性淀粉及其共混物的凝聚態(tài)結(jié)構(gòu)和影響因素。研究了增塑劑活性基團的不同對熱塑性淀粉塑化性能、機械性能、流變性能、熱力學(xué)性能、微觀結(jié)構(gòu)和熱穩(wěn)定性的影響。用親水性膠體對制備的熱塑性淀粉進行熱塑共混改性,通過添加明膠、卡拉膠改善熱塑性淀粉性能。結(jié)果表明天然淀粉通過溫度、剪切力與小分子增塑劑的共同作用,使得顆粒結(jié)構(gòu)逐漸消失,最終塑化成類似于塑料的均質(zhì)結(jié)構(gòu)。增塑劑對淀粉熱塑化作用取決于增塑劑分子結(jié)構(gòu),增塑劑的活性基團和分子量的大小。隨著增塑劑用量愈多,增強淀粉熱塑化的作用愈顯著,增塑后熱塑性淀粉的拉伸強度降低,斷裂伸長率增加,結(jié)晶結(jié)構(gòu)被破壞。甘油組分與尿素組分有不同的吸水過程和平衡吸水率,表現(xiàn)出吸水溶脹的現(xiàn)象,而尿素組分的吸水過程始終是吸水而溶解。綜合性能考慮選用20 wt%甘油增塑淀粉制備熱塑性淀粉,此時材料的拉伸強度為8.2 MPa,斷裂伸長率為25.6%。明膠與TPS共混有利于改善韌性,同時也會增大的密煉機塑化時的平衡轉(zhuǎn)矩。共混物力學(xué)性能與明膠含量有關(guān),總的來說,因二者相容性較好,共混物性能得到優(yōu)化,加入明膠將增加TPS平衡吸水率和吸水速度,吸水率可達627.1%。隨著卡拉膠含量的增加,卡拉膠分子可以與淀粉形成更多的氫鍵,其結(jié)果使材料的拉伸強度得到提高,并且導(dǎo)致斷裂伸長率逐漸變小。明膠和卡拉膠的鏈段之間可以通過局部的靜電交互作用互相搭接形成一定的網(wǎng)絡(luò)結(jié)構(gòu)。當(dāng)共混體系以80:20:10質(zhì)量分數(shù)比例共混時,拉伸強度達到26.62 MPa,斷裂伸長率可達73.47%。二者以復(fù)配使用能較好改善熱塑性淀粉的力學(xué)性能,熱穩(wěn)定性及加工性能。
[Abstract]:Starch is a kind of natural polymer with a wide range of low price and high crystallinity. The hydrogen bond between starch molecules is strong which limits the movement of molecular chain. Therefore starch does not have the properties of thermoplastic processing. Thermoplastic starch materials can be prepared by adding small molecular plasticizer, heating and mixing physical factors. However, the barrier and mechanical properties of thermoplastic starch are insufficient, so it is limited to be used as material alone. In this study, thermoplastic starch was prepared from potato starch, glycerol (glycerol, carbamide) as plasticizer, gelatin as binder and carrageenan as reinforcing agent. The condensed matter structure and influencing factors of thermoplastic starch and its blends were analyzed by means of scanning electron microscope and rotary rheometer. The effects of different active groups of plasticizer on the plasticizing properties, mechanical properties, rheological properties, thermodynamic properties, microstructure and thermal stability of thermoplastic starch were studied. Thermoplastic starch was modified by hydrophilic colloid. The properties of thermoplastic starch were improved by adding gelatin and carrageenan. The results showed that the particle structure of natural starch gradually disappeared through the interaction of temperature, shear force and small molecular plasticizer, and finally plasticized into a homogenous structure similar to plastics. The effect of plasticizer on starch thermoplasticization depends on the molecular structure of plasticizer, the active group and molecular weight of plasticizer. As the amount of plasticizer increased, the effect of enhancing thermal plasticization of starch was more obvious. The tensile strength of thermoplastic starch decreased, the elongation at break increased and the crystalline structure was destroyed. Glycerol and urea have different water absorption processes and equilibrium water absorption, showing the phenomenon of water absorption swelling, while the water absorption process of urea component is always water absorption and dissolution. The thermoplastic starch was prepared with 20 wt% glycerol plasticized starch. The tensile strength of the material was 8.2 MPA and the elongation at break was 25.6 MPA. The blending of gelatin and TPS can improve the toughness and increase the equilibrium torque of the mixer when it is plasticized. The mechanical properties of the blends are related to the content of gelatin. On the whole, the blending properties of the blends are optimized because of their good compatibility. The addition of gelatin can increase the equilibrium water absorption rate and water absorption rate of TPS, and the water absorption rate can reach 627.1%. With the increase of carrageenan content, carrageenan molecules can form more hydrogen bonds with starch, which results in higher tensile strength and smaller elongation at break. The chains of gelatin and carrageenan can be overlapped with each other by local electrostatic interaction to form a certain network structure. When the blending system was blended at 80:20:10 mass fraction, the tensile strength was 26.62 MPA and the elongation at break reached 73.47 MPA. The mechanical properties, thermal stability and processing properties of thermoplastic starch can be improved by the combination of the two methods.
【學(xué)位授予單位】：湖北工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O636.12

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本文編號：1889401