Thermoplastic starch and glutaraldehyde modified thermoplastic starch foams prepared using supercritical carbon dioxide fluid as a blowing agent

Supercritical carbon dioxide (scCO₂) processed thermoplastic starch (scCO₂^aTPS), cellulose nanofiber (CNF) modified scCO₂^aTPS (scCO₂^aTPS₁₀₀CNF_0.02) and glutaraldehyde (GA) modified scCO₂^aTPS₁₀₀CNF_0.02 (scCO₂^aTPS₁₀₀CNF_0.02GA_x) foams were prepared for the first time using scCO₂ as a blowing agent during their foaming processes. The expansion ratio, cell density, moisture resistance, and compressive strength (σ_c) retention properties of each foam series were considerably improved with increasing scCO₂ pressure during the foaming processes. The expansion ratios and cell densities of each scCO₂^aTPS₁₀₀CNF_0.02GA_x foam series were increased considerably to a maximum value, as the GA content approached an optimum value. The optimal scCO₂¹¹TPS₁₀₀CNF_0.02GA_1.6 foam material exhibited a high expansion ratio and cell density at approximately 50 and approximately 8 × 10⁸ cells/cm³, respectively. Compared with corresponding aged scCO₂^aTPS and scCO₂^aTPS₁₀₀CNF_0.02 foam specimens, considerably better moisture resistance and σ_c retention properties were observed for scCO₂^aTPS₁₀₀CNF_0.02GA_x foam specimens, when they were modified with the corresponding optimum GA content. The moisture resistance and σ_c retention for optimal prepared scCO₂⁷TPS₁₀₀CNF_0.02GA_0.4, scCO₂⁹TPS₁₀₀CNF_0.02GA_0.8 and scCO₂¹¹TPS₁₀₀CNF_0.02GA_1.6 foam materials improved further with increasing scCO₂ pressure. Possible reasons accounting for the highly expansion ratio, moisture resistance, and σ_c retention properties for scCO₂^aTPS₁₀₀CNF_0.02GA_x foams are presented.     

Hydrogel‐coated polyurethane/urea shape memory polymer foams

Shape memory polymers (SMPs) are a class of responsive polymers that have attracted attention in designing biomedical devices because of their potential to improve minimally invasive surgeries. Use of porous SMPs in vascular grafts has been proposed because porosity aids in transfer of fluids through the graft and growth of vascular tissue. However, porosity also allows blood to leak through grafts so preclotting the materials is necessary. Here hydrogels have been synthesized from acrylic acid and N‐hydroxyethyl acrylamide and coated around a porous SMP produced from lactose functionalized polyurea‐urethanes. The biocompatibility of the polymers used to prepare the cross‐linked shape memory material is demonstrated using an in vitro cell assay. As expected, the hydrogel coating enhanced fluid uptake abilities without hindering the shape memory properties. These results indicate that hydrogels can be used in porous SMP materials without inhibiting the shape recovery of the material. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1389–1395     

Anisotropic cellular structures from semi-crystalline polymer templates

We report an investigation to determine the effect of an anisotropic semi-crystalline template on the resulting cell morphology of microcellular polymeric foams generated in these materials. Poly(ethylene terephthalate) (PET)-polystyrene (PS) composite foams are prepared by using supercritical carbon dioxide (scCO₂) not only as a foaming agent but also as a transport medium of styrene and initiator into a biaxially-oriented PET templating film. The composite foam so obtained demonstrates a highly interpenetrating network verified by a single Tg of 98°C. Substrate orientation is observed not to dictate the cell formation; however highly anisotropic swelling and a shape-templating phenomenon is observed, with the most significant dimension change in the thickness of the film. Introducing confinement in the direction of maximum dimension change is found to introduce a highly anisotropic lamellar cell architecture.     

Graphene foam–based electrochemical capacitors

Electrochemical capacitors (ECs) are a promising technology for energy storage, and future development of sustainable electrode materials is critical to developing these devices. The recent progress and earnest motivation to develop high specific energy capacitors commercially for the emerging market and electronics industry, coupled with the significance and popularity of graphene foam (GF)–based electrode materials in the preparation of functional capacitors have been crucially explored in this review. The review outlines the current disposition and headways in GF-based ECs' technology. Besides, owing to its three-dimensional interconnected hierarchical form alongside the physicochemical distinctions, GF has been regarded as one to curtail some bottlenecks regarding graphene dispersion/restacking in nanocomposite materials. Some of the various techniques to synthesizing high-grade GF that can enable higher energy density of ECs, as well as some key material's features of GF that enhance various performances of the material's composite have also been reviewed.     

热塑性聚氨酯微孔发泡材料的表观密度与其力学性能的关系

用高压CO2流体通过升温发泡法制备了一系列不同表观密度的热塑性聚氨酯(TPU)微孔发泡材料,探究了TPU发泡材料的表观密度与其力学性能的关系.微孔发泡材料的泡孔结构和表皮结构由扫描电子显微镜表征;不同表观密度材料的力学性能利用万能材料试验机和旋转流变仪表征.研究发现:TPU微孔发泡材料的表观密度主要是由材料皮层厚度占比和泡孔层密度决定的,皮层厚度占比越小和泡孔面积占有率越高,泡沫的表观密度越小;微孔发泡材料在线性应变区的压缩模量E与材料表观密度ρ的关系为:E∝ρ1.7,符合泡沫材料压缩模量与表观密度呈指数关系的基本结论;循环压缩实验中,随微孔发泡材料表观密度减小,损耗百分比增大,残余应变减小;流变实验中,微孔发泡材料的模量随表观密度变化没有明显的变化,阻尼因子tanδ随泡沫表观密度变化不呈单一的规律性.同时,阐明了微孔发泡材料的压缩模量E和损耗百分比随表观密度变化的机理.     

多孔泡沫铜和硫脲协同作用构筑无枝晶锂负极

锂金属作为下一代储能电池的理想负极材料一直受到极大的关注,然而锂枝晶的不可控生长和负极副反应带来的低库伦效率问题严重限制了锂金属电池的发展。这里,我们提出了一种多孔泡沫铜和硫脲协同作用的策略,利用硫脲分子的超填充作用实现锂金属在多孔泡沫铜表面的均匀沉积。在电解液中添加0.02 mol·L^-1硫脲作为电解质添加剂,采用多孔泡沫铜的Li||Cu半电池在循环300圈以后,库伦效率仍保持在98%以上。此外,在5C的高倍率条件下,Li||Li FePO4全电池循环300圈以后仍有94%的容量保持率。本工作为锂金属负极保护提供了一种新的策略并且该策略也可以扩展到其他金属负极保护中,非常有利于下一代高能量密度储能电池的开发。     

氮掺杂泡沫碳电催化剂的制备及氧还原性能

利用水解乙烯基咪唑鎓硝酸盐([Hvim]NO3)作为发泡剂和一次氮源,在碳化过程中实现材料自发泡。创造性地引入二次氮源三聚氰胺(C3H6N6),通过调控一次、二次氮源比例和碳化温度,制备得到氮掺杂泡沫碳材料(HxMy-T,其中x∶y为一次和二次氮源的质量比,T对应不同的碳化温度)。该方法提升了催化剂的氮掺杂含量,构建了更多有利于氧还原反应(ORR)的活性氮位点。电镜结果显示,催化剂H1M1-1000呈现出典型的泡沫碳孔洞结构和丰富的层状褶皱结构;X射线光电子能谱测试结果表明,该样品具有较高的活性氮含量(原子分数6.77%),吡啶氮和石墨氮的原子分数分别高达22.23%和55.59%;电化学测试结果表明,该样品在碱性环境中的半波电位为0.834 V(vs RHE),与商业Pt/C相当,且具有优于商业Pt/C的抗甲醇性能和稳定性。     

煤基碳泡沫/聚氨酯相变复合材料的制备及储热性能

以煤基碳泡沫(CCF)作为骨架材料来封装改性固-固相变材料聚氨酯(PU),并实现其功能化应用。使用场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线粉末衍射仪(PXRD)、傅里叶变换红外(FT-IR)光谱仪、热重分析仪(TGA)、差示扫描量热(DSC)分析仪、热导测试仪对所得到的复合材料(PU@CCF)进行结构和特性表征。结果显示,聚乙二醇(PEG-6000)与异氰酸酯(HDI)反应制备聚氨酯的最优摩尔比例为1:2,煤基碳泡沫可以很好地阻止聚氨酯从复合材料中泄露出来。相较于聚乙二醇,复合材料的导热率上升了54%,经过200次热循环,复合材料保持了良好的稳定性,而且其相变主体材料PU的过冷度降低了10℃以上。基于碳泡沫骨架良好的导电性,加载高于0.8V的低电压就可实现聚氨酯电热相变储能,在1.1V电压驱动下,其电热转换效率可达75%。该工作是目前报道的最低电压下可实现电热相变转换的复合功能材料,为实现低成本相变复合材料的制备与功能化提供重要参考。     

封闭水浴溶样-载碳泡塑吸附-电感耦合等离子体发射光谱法测定矿石中金含量

采用聚碳酸酯溶样瓶进行封闭水浴溶样,溶液加入NH_4HF_2和酒石酸配合其它干扰金属阳离子,加入载碳泡塑振荡吸附金,使用电感耦合等离子体发射光谱仪(ICP-OES)直接测定.方法检出限为0.005 09μg/g,测定上限为150.0μg/g,相对标准偏差(RSD)低于5.77%,消除了Ag、Sb和Fe等阳离子干扰,通过对不同含量金矿石标准物质的测定,取得了较高的准确度,可满足金矿石分析要求.