乳化剂对正十八烷微/纳胶囊形貌和性能的影响

通过原位聚合法制备了以正十八烷为囊芯、蜜胺树脂为囊壁的相变材料微胶囊和纳胶囊.采用扫描电子显微镜,差示扫描量热仪,热重分析仪分别观测了胶囊表面形貌、粒径分布、相变性能及热稳定性能等.实验结果表明,当采用十二烷基硫酸钠为乳化剂时,所得微胶囊结构完好,粒径分布均匀,平均粒径约为65μm,囊芯含量高达87%(wt).微胶囊过冷度仅为2.6℃.当采用苯乙烯-马来酸酐共聚物钠盐为乳化剂时,制得纳胶囊的平均粒径约为840nm,囊芯含量为45%(wt),且囊芯过冷度高达18.9℃.     

相变材料微胶囊的制备及提纯

采用原位聚合法合成了以正十八烷为囊芯、三聚氰胺-甲醛树脂为囊壁的相变材料微胶囊,并通过密度法对微胶囊样品进行了提纯。通过扫描电子显微镜、差示扫描量热仪对纯化前后胶囊分析发现,微胶囊形貌明显变好,热效率也显著提高。     

纳米SiO_2和石墨改性相变储热微胶囊的研究

以固体石蜡为相变芯材,三聚氰胺-尿素-甲醛共缩聚树脂为囊壁,采用原位聚合法制备了微胶囊型相变储热材料;并针对该相变材料热导率低及亲水性差缺点,用石墨和纳米SiO2对芯材和微胶囊进行了导热性和表面性能的改性研究。采用光学显微镜(OM)、红外光谱仪(FTIR)、差示扫描量热仪(DSC)、热重分析仪(TGA)等对产品的表面形态、化学结构、热性能等进行了测试和表征。结果表明:石蜡微胶囊化后能保持原有的储热特性,相变焓为47.5J/g;球状微胶囊平均粒径为45μm,表面粗糙,石蜡包封率达80%;纳米SiO2改性后微胶囊亲水性、耐热性能、机械强度均增强;石墨改性后导热性提高。     

细乳液界面聚合模板法制备双壁相变材料纳米胶囊

通过细乳液界面聚合法制备出了以正十八烷为囊芯,聚脲为壁材的纳胶囊,再以此聚脲壁材为模板,使苯乙烯与交联剂二乙烯基苯在内表面共聚形成双层壁材相变材料纳胶囊.采用扫描电子显微镜,差示扫描量热仪,热重分析仪,粒度分析,红外光谱等手段分别考察了纳胶囊的表面形态、相变性能、热稳定性能、粒径分布及胶囊结构等.实验结果表明,超声乳化...     

悬浮聚合法制备相变材料微/纳胶囊

采用悬浮聚合法合成了以正十八烷为囊芯、苯乙烯-新戊二醇二丙烯酸酯共聚物为囊壁的相变材料微/纳胶囊,并通过扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、热重分析仪(TGA)等对其形貌、结构、热性能、热稳定性等进行了分析。结果表明,相变材料微/纳胶囊形貌完整、分散性好;相变材料微胶囊热稳定良好,其失重起始温度较囊芯材料提高了近40℃;相变材料微/纳胶囊在降温过程中有不同程度的过冷结晶现象。     

十八烷@脲醛树脂相变储能微胶囊的制备及表征

通过原位聚合法,制备以脲醛树脂为囊壁,十八烷为囊芯的相变储能微胶囊,并通过红外光谱、扫描电子显微镜、粒径分析仪和差示扫描量热仪分别表征了其组成、结构形貌、粒径大小和热能存储性能。结果表明:脲醛树脂能够成功包覆十八烷,所制备的微胶囊具有良好的外观形貌和均一的粒径分布,平均粒径在3.4μm左右;且所制备微胶囊熔融热焓(ΔH_m)和结晶热焓(ΔH_c)分别高达89.82kJ/kg和91.54kJ/kg,具有优异的相变储热能力。     

芯材制备条件对聚脲石蜡相变微胶囊性能的影响

采用吐温-80(Tween-80)和司班-80(Span-80)复配乳化剂,通过芯材表面修饰法制备以聚脲为壁材,石蜡为芯材的石蜡相变微胶囊材料。采用差示扫描量热仪、激光粒径分布仪和扫面电子显微镜对石蜡相变微胶囊进行了形貌表征和性能分析。通过对石蜡相变微胶囊芯材制备的单因素试验,对聚脲石蜡相变微胶囊的性能进行了研究。实验结果表明,复配乳化剂的使用能使芯材乳液的稳定性增加,而复合乳化剂用量、搅拌速率和乳化时间的延长有利于芯材乳液的稳定性的增加;芯材制备过程中,搅拌分散转速、搅拌分散时间及搅拌降温速率对石蜡相变微胶囊的性能有重要影响。     

乳化剂对聚脲树脂相变微胶囊性能的影响

分别采用苯乙烯-马来酸酐共聚物钠盐(SMA钠盐)、辛基酚聚氧乙烯醚(OP-10)和阿拉伯树胶3种不同的乳化剂,通过界面聚合法制备了以正十八烷为囊芯、聚脲树脂为囊壁的相变材料微胶囊。采用扫描电镜、差示量热、热重和粒径统计分析软件对微胶囊的表观形貌、储热性能、热稳定性能和粒径分布进行了研究。结果表明:与乳化剂SMA钠盐和阿拉伯树胶相比,以OP-10为乳化剂制备的相变微胶囊粒径最小,分布均匀,且具有良好的抗渗透性能。乳化剂的用量对胶囊的性能有重要的影响,当乳化剂OP-10的浓度为8%时,所得微胶囊的粒径分布集中,平均粒径约为2μm,副产物较少。与正十八烷相比,相变微胶囊的初始热失重温度明显提高,所制备的微胶囊具有良好的热稳定性。     

纳米SiO_2改性相变储热微胶囊的制备及性能研究

以亲水型纳米SiO2粒子改性的三聚氰胺一甲醛树脂作为微胶囊壁材,以相变材料正十二醇为芯材,采用原.位聚合法,制备了纳米SiO2改性的相变储热微胶囊,研究了纳米SiO2粒子对微胶囊性能的影响,采用FTIR、DSC和SEM等方法进行了表征.结果表明,当壁材中加入适量的纳米SiO2时,纳米粒子在壁材里面分布均匀,微胶囊的相变焓提高,破损率降低,且纳米SiO2不会破坏预聚体的缩聚反应.当壁材中纳米SiO2质量分数为1%时,制备的微胶囊相变焓达148.7J/g,微胶囊破损率为23.1%.     

复合相变材料微胶囊的制备及表征

以十八烷和硬脂酸丁酯为复合相变材料,苯乙烯和甲基丙烯酸的聚合物为壁材,通过微乳液聚合法制备了芯/芯比分别为4∶6、5∶5和6∶4的相变材料微胶囊,并通过SEM、DSC、TG和FT-IR等手段对制备的微胶囊进行了结构性能表征。     

Effect of interface debonding on the thermal conductivity of microencapsulated-paraffin filled epoxy matrix composites

Microcapsules containing phase change materials (microPCMs) can be filled in polymeric matrix forming smart temperature-controlling composites. The aim of this study was to investigate the effect of interface debonding on the thermal conductivity of microPCMs containing paraffin/epoxy composites. The shell thickness and average size of microPCMs were controlled by regulating the core/shell ratios and emulsion stirring rates. Test results indicated that the thermal conductivity (K_e) of all composites decreased after a thermal shock treatment. SEM and thermography measurements were applied to observe the interface behaviors of composites after a violent thermal treatment process. It was proved that the interface debonding was generated because of the mismatch of expansion coefficient between shell and epoxy. A modeling analysis of the relative thermal conductivity (K_r) indicated that the effective approach to decrease the debonding is to enhance the molecule tangling degree between shell and matrix.     

硬脂酸填充碳纳米管相变胶囊材料的热性质研究

采用真空浸渗法,成功地将硬脂酸填充到碳纳米管(CNTs)空管内,得到CNTs/硬脂酸纳米相变胶囊材料。差示扫描量热分析表明,硬脂酸填充CNTs后,熔点下降了2.85℃,硬脂酸在CNTs内的体积填充度为31.9%。采用分子动力学方法深入研究硬脂酸在CNTs受限空间内的热性质。结果表明,在CNTs的纳米受限空间作用下,硬脂酸分子在CNTs内呈有序的环状分布,与CNTs的管壁距离保存在0.37nm。与纯硬脂酸相比,CNTs/硬脂酸的熔点降低,自扩散系数增加,导热系数比空CNTs下降32%~41%,为纯硬脂酸的117~159倍。     

PbTiO3纳米晶的制备及表征

以硬脂酸、乙酸铅和钛酸丁酯为原料用硬脂酸凝胶法合成ＰｂＴｉＯ３纳米晶原粉，利用改进的烧结设备，同时采用Ｎ２气氛下预烧，通过调节Ｎ２和Ｏ２的流量控制烧结气氛，得到粒径重复性好的ＰｂＴｉＯ３纳米晶，用差热分析，热重分析和Ｘ－射线衍射对合成过程进行了研究，用透射电镜考查纳米晶的粒度和形貌，用５ＤＸ－红外光谱仪对ＰｂＴｉＯ３纳米晶的红外透射谱进行了测试分析。     

机械化学法一步合成表面改性氧化锌纳米粉体

以醋酸锌、氢氧化钠、硬脂酸为原料,采用机械化学法,一步制备出具有表面亲油性能的氧化锌粉体。借助XRD、FTIR、TEM、纳米粒度测试等方法对粉体进行了表征,研究了硬脂酸对氧化锌粉体表面改性的机理。结果表明,硬脂酸中的羧基与氧化锌颗粒表面的羟基发生了酯化反应,并在表面形成有机膜,氧化锌粉末由亲水性转化为亲油性。当球磨时间为50 min、硬脂酸加入量为氧化锌质量的4.5%时,可以得到平均粒度为90 nm的亲油性氧化锌粉体。     

硬脂酸/SiO2纳米微胶囊复合相变材料的制备及储热性能的研究

采用分步合成法将硬脂酸填充到SiO2空球内,制备硬脂酸/SiO微胶囊复合相变材料,并采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和差示扫描量热法(DSC)等分析测试手段对复合材料的结构和储热性能进行了表征.结果表明,该纳米微胶囊复合相变材料具有直径约220nm的规则形貌和良好的储热性能.此外,热的传导和抑制过冷...     

An experimental investigation of modified and unmodified flax fibres with XPS, ToF-SIMS and ATR-FTIR

Natural fibres are envisaged today as potential candidates for replacing glass fibres in composite materials. Although natural fibres have a number of advantages over glass fibres, the strong polar character of their surface is a limiting factor as, compatibility with strongly apolar thermoplastic matrices is very low. Such problems of incompatibility may be overcome with fibre pre-treatments, which can enhance compatibility although having a negative impact on the economics of using such materials. In this study two fibre pre-treatment methods, acetylation and stearic acid treatments, have been applied on flax fibres. The effect of these two pre-treatments has been examined by use of XPS, ToF-SIMS and FTIR spectroscopic methods. It was found that the fibre surface before treatment is very different to what may have been expected for cellulose materials. There is an appreciable coverage of the flax fibre surface with hydrocarbon compounds, possibly waxy substances, but no aromatic compounds were detected. All three spectroscopic methods revealed that the fibre surface chemistry has been altered after the treatments, and especially for acetylation it was found that ester bonds are present on the fibre surface after treatment. For the stearic acid treatment the situation still remains less conclusive. Finally, ToF-SIMS experiments revealed that the coverage of the fibre surface with acetyl groups and stearic acid is highly heterogeneous.     

功能型LED CeO_2/苯基硅橡胶封装材料

采用表面覆盖改性技术,利用硬脂酸改性纳米CeO_2,将改性后的纳米m-CeO_2与苯基含氢硅树脂(PH)通过化学接枝制得m-CeO_2-PH接枝物,通过氢化硅烷化法,以接枝物为交联剂,在铂催化剂作用下制备了一种发光二极管(LED)封装用透明m-CeO_2/苯基硅橡胶材料。结果表明:经硬脂酸改性后m-CeO_2表面产生硬脂酸盐,增加了界面的相容性,提高了纳米CeO_2在聚合物中的分散。通过化学方法将m-CeO_2接枝到PH体系中,与苯基乙烯基硅树脂(PV)按化学计量比在催化剂作用下高温固化合成了一种功能型m-CeO_2/苯基硅橡胶材料。研究表明:当m-CeO_2质量分数为0.02%时,m-CeO_2/苯基硅橡胶材料的透光率仍可达到85%以上。同时,耐紫外老化性能和力学性能有明显提高。苯基硅橡胶材料中引入质量分数为0.02%的m-CeO_2,当分解温度到达600℃时,m-CeO_2/苯基硅橡胶材料的热失重比例比纯苯基硅橡胶减少了8%,m-CeO_2/苯基硅橡胶材料的放热量明显低于纯苯基硅橡胶,这对于封装有很大优越性。     

纳米晶Ba1—xPbxTiO3的合成与表征

以醋酸铅，硬脂酸钡和钛酸丁酯为原料，用硬脂酸凝胶法（ＳＡＧ）合成了粒度均匀，粒径１０－２０ｎｍ的Ｂａ１－ｘＰｂｘＴｉＯ３纳米晶粉末，利用红外光谱（ＩＲ），热重（ＴＧ）和差热分析（ＤＴＡ）研究了纳米晶粉末的合成过程。用ＴＥＭ，ＸＲＤ观察和研究纳米晶的形貌及晶体结构，并用发射光谱测定样品的纯度。     

月桂酸-硬脂酸/SiO2复合相变材料的实验研究

相变蓄热技术能够收集太阳能等低品位热源形成稳定的“能量池”,为建筑保温蓄热或末端能量利用提供稳定的热源。本文选取月桂酸和硬脂酸作为基本有机相变材料,采用步冷曲线法测量并绘制了两种材料的二元平衡相图,得到二者最小共熔点混合质量比例是月桂酸为70%,硬脂酸为30%,此时混酸的相变温度为31.2℃,相变潜热为264.3 kJ/kg;为增强相变材料的热稳定性和导热性能,预防或缓解在熔解-凝固热循环中出现的蠕流分层现象,以质量比为70%月桂酸和30%硬脂酸形成的混酸为基本材料,添加具有三维网络结构的SiO2硅溶胶进行复合材料的调制和测试,结果表明,当SiO2在复合材料中所占质量比例为35%时,混酸完全被四面体状的SiO2所包覆固定,形成稳固的相变主体。多次循环实验显示,复合相变材料的相变温度为30.8℃,相变潜热值为104.1 kJ/kg,虽然相变潜热值有所降低,但热稳定性大大增强。     

Preparation and Thermodynamic Properties of Camphene/Stearic Acid Composites as Phase-Change Materials in Buildings

In this study, a series of shape-stabilized phase-change materials (PCMs) of camphene/stearic acid (CS) were prepared and their thermal properties were measured by differential scanning calorimetry. The results indicated that the mixture consisting of 60 mass% camphene and 40 mass% stearic acid is the most favorable as a PCM, in terms of the phase-change temperature and latent heat. Thereafter, the CS was absorbed in fly ash, pyroclastic, barite, and marble powder, which acts as a supporting material, to prepare four kinds of composite-based PCMs. DSC, FT-IR, and scanning electron microscopy measurements were made to investigate the structures and properties of the PCMs. DSC results showed that the latent heats of melting and freezing of the composite PCMs were sharply decreased. Morphology and structural characterization revealed that, in form-stable PCMs, the dispersion of the supporting materials in the camphene/stearic acid matrix is homogeneous and there is no chemical interaction between the CS and composites. The composite PCMs showed excellent thermal stabilities and reliabilities, when their phase-change temperatures were concerned. These indicate that the prepared composite-based PCMs are suitable for thermal energy storage because of their applicable temperature range, thermal reliability, and chemical stability.