香蕉皮浆改性聚乙烯醇薄膜制备及对蛋糕包装保鲜的研究

选择无毒、无腐蚀性且环境友好的亲水性高分子材料聚乙烯醇(PVA)作为成膜基材,在香蕉皮浆中加入纯PVA制成改性薄膜,常温下研究不同质量分数的香蕉皮浆改性薄膜的性能以及对无任何添加剂蛋糕的保鲜效果。实验选用了6个不同质量分数的香蕉皮浆改性薄膜和双层薄膜(改性PVA薄膜外层加上纯PVA外膜)对蛋糕进行包装,每隔2d对蛋糕进行观察,对蛋糕的质量变化以及菌落总数进行测定,并分析其变质情况。结果表明,香蕉皮浆质量分数为2%时,改性PVA薄膜拉伸强度最大;当香蕉皮浆质量分数为3%时,吸水性降低,热封强度最大,其抗菌保鲜效果最优,其次是香蕉皮浆质量分数为2%;而双层薄膜保鲜的效果比单层薄膜好,但是放置时间越长,蛋糕会越干、硬,品质下降严重。     

聚乙烯醇/淀粉薄膜的力学性能及结晶行为

通过熔融共混挤出的方法,制备了聚乙烯醇(PVA)/淀粉薄膜,研究了淀粉加入量对PVA/淀粉薄膜力学性能的影响。采用差示扫描量热法研究了PVA薄膜和PVA/淀粉薄膜的结晶行为及非等温结晶动力学。结果表明:随着淀粉含量的增加.PVM淀粉薄膜的拉伸强度和断裂伸长率下降。在淀粉质量分数为25%时,薄膜的拉伸强度为17.05 MPa.断裂伸长率为425.00%.仍能达到包装薄膜对力学性能的要求。PVA/淀粉薄膜熔融温度和结晶温度均随着淀粉加入量的增加向低温方向移动;在相同的冷却速率下,共混薄膜的结晶速率低于PVA薄膜,同时结晶度也下降.导致力学性能下降。     

淀粉/PVA降解塑料耐水性能的研究

实现了淀粉/PVA塑料的热塑性加工,并用正交法研究了PVA、甘油、柠檬酸、水和硼砂用量对淀粉/PVA塑料的耐水性能和力学性能的影响。结果表明:甘油、柠檬酸和水可有效改善淀粉/PVA塑料的加工性能;适量的柠檬酸和甘油可以提高淀粉/PVA塑料的耐水性能;硼砂可以交联淀粉和PVA,并提高淀粉/PVA塑料的耐水性能;增加PVA的用量也可明显提高淀粉塑料的耐水性能。当淀粉与PVA质量比为50/50时,淀粉与PVA的相容性最好。     

偏光片变色机理浅析

研究了太阳照射后液晶显示器（LCD）偏光片的变色现象,采用智能型氙灯老化试验机、广角/小角X射线散射结构分析仪（WAXS）、X?射线能量色散谱仪（EDS）和分光光度计等对偏光片的光学性能、耐候性能及表面元素等进行了测试和表征,并探讨了其变色机理。结果表明,105 ℃×1 h的高温测试后,聚乙烯醇（PVA）膜素子中I₃^-紫外吸收峰强度增加1倍;120 ℃×120 h测试后,I₃^-紫外吸收峰强度增加2倍,PVA?I₅^-吸收峰强度减弱,PVA?I₃^-吸收峰强度增加;碘系偏光片变色机理为PVA?I₅^-向PVA?I₃^-转化,随着I₃^-含量增加偏光片颜色逐步变成棕色;变色的碘系偏光片在高温高湿处理后可以恢复到原来的颜色,PVA?I₅^-与PVA?I₃^-之间在偏光片中可以互相转换;偏光片受太阳辐射变色问题与偏光片抗紫外性能及耐高温性能有关;通过优化偏光片原料与制造工艺以提高其中紫外吸收剂含量可以提升其抗紫外性能;增加偏光片中PVA?I₅^-含量以提升其耐高温性能可以解决太阳照射下碘系偏光片变色问题。     

PVA/石榴皮粉复合薄膜的制备及性能研究

以聚乙烯醇(PVA)为基材、石榴皮粉为填充材料,采用溶液共混的方法制备了不同石榴皮粉含量的PVA/石榴皮粉复合薄膜。通过扫描电子显微镜(SEM)、红外光谱、紫外可见光谱、力学性能测试、水蒸气透过率测试、热重差热分析等手段考察了石榴皮粉含量对PVA复合薄膜性能的影响。结果表明:石榴皮粉与PVA相容性良好,与纯PVA薄膜相比,PVA/石榴皮粉复合薄膜的热稳定性显著增强,并表现出优异的紫外光阻隔性能,同时,随着石榴皮粉含量的增加,复合薄膜的水蒸气透过率提高,脆性增大。     

海藻酸钠/聚乙烯醇溶液的性能及静电纺丝

将质量分数为2%的海藻酸钠(SA)与质量分数为8%的聚乙烯醇(PVA)按一定体积比混合后进 行静电纺丝,研究了SA与PVA溶液的相容性及SA/PVA共混溶液性能.结果表明:SA与PVA溶液相容;随着PVA含量的增加,SA/PVA共混溶液的粘度、表面张力、电导率则降低,共混溶液的可纺性提高;静电纺丝得到的SA/PVA超细...     

聚乙烯醇/磺酸化碳纳米管复合纤维的制备与性能研究

采用湿法纺丝法制备了聚乙烯醇/磺酸化多壁碳纳米管(PVA/s-MWCNTs)复合纤维,并对复合纤维的结构与性能进行了表征。结果表明:当纤维中s-MWCNTs质量分数为5%时,s-MWCNTs均匀地分散在PVA基体中,当s-MWCNTs质量分数增加到8%时,纤维中出现少许s-MWCNTs团聚体;随着s-MWCNTs含量的增加,复合纤维的结晶度逐渐降低,PVA微晶取向度先增大后减小,纤维的模量和断裂强度均先增大后减小,电导率逐渐增加;当s-MWCNTs质量分数为5%时,纤维力学性能较好,其断裂强度和模量分别为0.83GPa和15 GPa,而s-MWCNTs质量分数为8%时,纤维电学性能较好,其电导率为0.65 S/m。     

不同黏结剂体系对水基流延成型Y2O3稳定ZrO2的影响

分别采用聚乙烯醇(potyvinyl alcohol,PVA)、乳胶B1070和PVA B1070复合黏结剂体系,水系流延成型法制备固体氧化物燃料电池(solid oxidefuel cell,SOFC)电解质8%(摩尔分数)Y2O3稳定的ZrO2(8YSZ)薄膜.研究了不同黏结剂对流延工艺以及对流延坯片的影响.结果表明:不同黏结剂加入后浆料的黏度和剪切变稀程度随PVA加入量的增加而增大.相反,浆料的黏度和剪切变稀程度随B1070加入量的增大而减小.发现使用不同黏结剂对流延坯片的生坯密度和干燥收缩具有重要的影响.8YSZ坯片的烧结密度随着生坯密度增大而增大,以300(质量分数,下同)PVA 70?070为复合黏结剂,8YSZ与黏合剂的质量比为0.93,流延成型的坯体在1 400℃保温2 h烧结能获得相对密度达98.5%的SOFC电解质8YSZ薄膜.     

PVA/nano-SiO2原位聚合薄膜性能的研究

采用溶胶-凝胶与原位聚合技术,制备了不同纳米二氧化硅（nano-SiO₂）含量的聚乙烯醇/二氧化硅（PVA/SiO₂）杂化薄膜。研究了纳米颗粒的引入对PVA/SiO₂薄膜热学和力学性能的影响。结果表明:SiO₂含量较低时只降低PVA/SiO₂结晶度,而含量较高时结晶度和结晶尺寸均降低;SiO₂的加入拓宽了PVA的玻璃化转变温度（T_g）范围,提高了PVA的热稳定性;PVA/SiO₂的拉伸强度、拉伸模量得到增强,而断裂伸长率则呈下降趋势。SiO₂质量分数为5%时,PVA/SiO₂薄膜的综合性能最佳。     

表面活性剂对聚乙烯醇基薄膜透光性及机理的影响

针对聚乙烯醇（PVA）与表面活性剂能组成复配体系,制备了聚乙烯醇基亲水性薄膜材料,研究了表面活性剂的掺量对聚乙烯醇基薄膜的微观结构、孔隙度、透光性能、PVA结晶度及晶粒尺寸的影响。采用紫外分光光度计考察了各薄膜的透光性;采用扫描电子显微镜观察了聚乙烯醇/表面活性剂的横截面微观结构;采用X射线衍射仪考察了不同表面活性剂的添加量对复合薄膜的晶相组成及PVA晶粒尺寸的影响,结果表明当表面活性剂添加量在6%~10%（质量分数,下同）时,阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）明显地降低聚乙烯醇的结晶度,而阴离子表面活性剂十二烷基苯磺酸钠（SDBS）则没有此效果;CTAB的加入使聚乙烯醇/CTAB体系中PVA晶粒尺寸增大,SDBS的加入使聚乙烯醇/SDBS体系中PVA晶粒尺寸减小。最后对聚乙烯醇与表面活性剂相互作用机理示意图进行了预测。     

柠檬酸交联可食用红薯淀粉膜的制备和性能

本文采用浇铸法制备了柠檬酸交联红薯淀粉膜,并对膜的机械性能、吸水性、水溶性、抗甲酸溶解性等进行了测试。结果发现交联后的淀粉膜的拉伸力显著提高、吸水性增强、水溶性降低、抗甲酸溶解性增强。膜的机械性能的改善与柠檬酸的浓度、交联温度、交联时间有关,实验发现,当柠檬酸的浓度为淀粉浓度的5％,165℃处理5分钟时,膜的拉伸力比未...     

Heterogeneous method of chitosan film preparation: Effect of multifunctional acid on film properties

The heterogeneous crosslinking method was applied to chitosan films with citric acid to observe and understand the effect of a multifunctional acid at a low concentration on film properties. Neat and neutralized chitosan films and films containing 15% (w/w) citric acid (denoted as CA films) were characterized by mechanical, water vapor permeability (WVP), and thermogravimetric analysis tests. The CA films displayed a higher tensile strength by 10%, lower WVP by 30%, and higher thermal stability, compared to neutralized films. The crystalline structure converted back from tendon to Type II after the addition of citric acid, as determined by X-ray diffraction. Neat films displayed a lower water contact angle (72°) compared to neutralized and CA films (78°–79°). The heterogeneous method was also applied to incorporate a plasticizer into a neutralized film to potentially observe the glass transition using dynamic mechanical analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48648.     

柠檬酸及其盐在金属防护中的应用研究现状

综述了柠檬酸及其盐作为缓蚀剂,电镀和化学镀镀液添加剂及其在金属防护膜中的应用状况.认为柠檬酸与其他缓蚀剂的缓蚀协同性研究是柠檬酸型缓蚀剂开发的重点,柠檬酸型配位剂是替代氰化物等有毒镀液添加剂的理想选择,在稀土等无铬转化膜中添加柠檬酸盐是改进稀土转化膜耐蚀性研究的一个方向.     

PVC用三元复合羧酸镧热稳定剂的制备及性能研究

以月桂酸、十四烷二酸、柠檬酸和硝酸镧为原料,制备了一种复合羧酸镧热稳定剂,采用刚果红法及转矩流变仪法对PVC进行了静态和动态热稳定性测试,并通过红外光谱和紫外光谱分析了复合羧酸镧及组成成分对PVC的热稳定机理。结果表明,复合羧酸镧对PVC具有较好的热稳定性,且与辅助热稳定剂有较好的协同效应。红外光谱分析表明,复合热稳定剂在与PVC共同受热的过程中,镧离子的配位作用是减缓PVC热降解的主要因素,同时还伴有羧酸盐吸收HCl的作用。紫外光谱分析表明,月桂酸镧的前期热稳定性较好,而十四烷二酸镧和柠檬酸镧的长期热稳定性较好。     

Effects of β-carotene on light stability of soybean oil

β-Carotene was added to soybean salad oils to study its effect in inhibiting flavor deterioration due to light exposure. Flavor evaluations indicated that (a) when oils treated with citric acid were exposed to light (7535 lux) for 8 to 16 hr, oils containing 5 to 10 ppm β-carotene showed improved flavor stability compared to oils containing 0 to 1 ppm β-carotene; and (b) when oils were not treated with citric acid, only oils containing 20 ppm β-carotene were more stable to light. Capillary gas chromatographic analysis showed that the addition of 1 to 20 ppm of β-carotene significantly decreased formation of 2-heptenal and 2,4-decadienal in the absence or presence of citric acid. Determination of peroxide values showed the same trends as gas chromatographic analyses of volatiles. In the presence of 15 and 20 ppm β-carotene, some off-flavors, as well as poor ratings for color quality, were reported by panelists. Therefore, flavor deterioration initiated by light can be inhibited effectively in soybean oil, without affecting color quality, by addition of β-carotene at concentrations from 5 to 10 ppm to oils treated with citric acid.     

亚胺化对聚酰亚胺热学性能的影响

用均苯四甲酸二酐(PMDA)与4,4’-二氨基二苯醚(ODA)为单体,聚合得到一定表观黏度的聚酰胺酸(PAA)。通过调节温度和时间两个变量,并采用红外光谱仪、高温综合热分析试着分别对PAA凝胶膜热亚胺化过程以及热学稳定性进行了研究,结果表明:亚胺化程度随时间的增加而增大,亚胺化程度随着亚胺化温度的提高同样增大;通过热重分析仪对聚酰亚胺薄膜热学性能进行了研究,随着薄膜亚胺化程度的增大,薄膜的热稳定性提高。     

Effect of fuel type on structural and physicochemical properties of solution combustion synthesized CoCr2O4 ceramic pigment nanoparticles

Due to importance and wide applications, CoCr₂O₄ ceramic pigment nanoparticles were synthesized via low-temperature solution combustion route by different fuels including ethylenediamine/oxalic acid, ethylenediamine/citric acid, oxalic acid/citric acid and ethylenediamine/oxalic acid/citric acid. Physicochemical properties of the synthesized samples were determined by different techniques such as fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX) and color/optical properties were evaluated based on CIELAB system by spectrophotometer. Moreover, thermodynamic considerations of combustion reactions for CoCr₂O₄ nanopigments formation in terms of calculated adiabatic flame temperature and enthalpy of combustion reaction were studied. The Comparison of results and data showed that cobalt chromite pigment nanoparticles synthesized by using ethylenediamine/citric acid and ethylenediamine/oxalic acid/citric acid fuels exhibited higher purity, smaller crystallite size and lower degree agglomeration.     

柠檬酸工业废水处理现状

我国是世界上最大的柠檬酸生产和出口国,但柠檬酸生产工艺的固有特点,使其生产过程中产生大量高浓度废水,成为环境的严重污染源,而目前由于投资、技术、运行成本等原因,该行业三废基本处于任意排放状态,严重污染周围环境,因此,废水治理已成为我国柠檬酸行业的当务之急。作者分析了柠檬酸废水的来源及水质特性,综述了生物法、光合细菌法、乳状液膜法等方法在柠檬酸废水处理中的应用,并介绍了中和废水的回用技术。     

在苹果酸体系中化学镀镍磷的研究

介绍了在柠檬酸、醋酸及苹果酸体系中，对比研究化学镀镍磷工艺的过程。通过研究化学镀镍磷过程中的各个影响因素，如镍离子浓度、还原剂的浓度、配合剂的添加量、温度、ｐＨ值等，对镀层的沉积速度、镀层的含磷量、镀液的稳定性的影响，以便找出最佳的镀覆工艺条件，为其实际应用提供依据。     

Electron‐beam irradiation of low‐density polyethylene in the presence of phenolic stabilizer,carboxylic acid stabilizer,or both

The effects of Irganox 1010 and citric acid as antioxidants and modifiers of the network structure and mechanical and thermal properties of low‐density polyethylene (LDPE) during electron‐beam crosslinking with different irradiation doses (up to 120 kGy) were investigated. The results showed that the addition of these stabilizers had a retarding effect on the gel fraction of LDPE within the investigated range of electron‐beam‐irradiation doses. However, a noticeable effect on the gel fraction was found for the LDPE formulations compounded with citric acid alone or with its mixture with Irganox 1010 (in an equal ratio), as illustrated by a study of the gel‐fraction/dose relationships. Tensile testing measurements showed that the addition of both stabilizers caused a slight reduction in the stress at break and an increase in the strain at break. On the other hand, the thermal properties of the LDPE batches crosslinked with electron‐beam irradiation were greatly improved as a result of the compounding with these stabilizers, as shown by thermogravimetric analysis studies. In this respect, the temperatures at different weight losses, the temperatures of the maximum rate of thermal decomposition, and the activation energies indicated that compounding with citric acid was more effective for stabilization against thermal decomposition than compounding with Irganox alone or a mixture. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1275–1286, 2005