有机改性二氧化硅纳米胶囊化相变材料研究

胶囊化相变材料(PCMs)在炸药件隔热防护、电子器件控温等具有潜在应用价值,但现有无机壁材胶囊化PCM s存在粒径大、易破裂及与有机聚合物相容性差等局限。本研究利用不同有机硅烷前驱体在细乳液中的界面水解-缩聚方法,合成了一系列有机改性二氧化硅包覆正十八烷相变纳米胶囊。分别采用傅里叶变换红外光谱(FT-IR)、X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、差示扫描量热(DSC)和水接触角(WCA)等手段对其化学结构、结晶结构、形貌、相变特性和壁材疏水性进行了表征。结果表明,通过改变有机硅烷前驱体的体积比,得到了球形和碗状两种形貌的相变纳米胶囊,尺寸为200~693 nm,熔融焓为93.2~107.5 J·g~(-1),胶囊壁材的水接触角为67°~155°,可实现亲水-疏水-超疏水性表面性质调控。并且有机改性二氧化硅纳米胶囊化PCMs在超声作用下不易破碎,显示力学性能得到了改善。     

不同乳化剂作用下三聚氰胺-甲醛@正十八烷微胶囊相变复合材料微观形貌和热性能

采用原位聚合法,通过改变非离子/阴离子乳化剂组合制备了一系列以正十八烷(OD)为芯材、三聚氰胺(M)-甲醛树脂(F)为壁材的微胶囊相变储能材料,并借助FTIR、SEM、DSC和激光粒度分析仪等手段系统研究了乳化剂复配对M-F@OD微胶囊相变材料微观形貌和相变潜热的影响。结果表明,不同乳化剂组合及掺量对M-F@OD微胶囊相变材料的形貌和性能产生显著影响,当采用非离子和阴离子复合乳化剂时,M-F@OD微胶囊相变材料团聚现象得到明显改善,粒径分布更加均匀,颗粒尺寸进一步细化,粒径大小范围为0.1~1μm,储热能力明显提高,相变潜热达到70.86J/g。     

Thermal properties of combat uniforms treated with microencapsulated octadecane and change in clothing microclimate via thermal manikin

This study examined how the heat storage property and the heat release property of three different PCM (Phase Change Material) treatment concentrations of combat uniform fabrics affected microclimate inside clothing after the octadecane-treated fabrics were made into garments. Three combat uniforms were constructed with fabrics treated by three different octadecane concentrations (0, 8, and 16%) at the same curing temperature of 113.6 °C. The thermal properties of the octadecane-treated fabrics were acquired by using DSC (Differential Scanning Calorimeter) analysis. Also, water vapor and air permeability were measured before the thermal comfort of the octadecane-treated combat uniforms was evaluated. And then, a thermal manikin was used to measure skin temperature, skin humidity, and microclimate temperature, while the chamber was set at various environmental temperatures (0, 0–35, 35, and 35–0 °C). And, to analyze the differences among skin temperature, skin humidity, and microclimate temperature of the garments according to the three different octadecane concentrations, ANOVA and a post hoc test were conducted. As a result, heat of fusion and heat of crystallization (ΔH_f and ΔH_c) were observed to increase as the octadecane concentration increased. The 8% octadecane-treated fabrics had 3.56 J/g of ΔH_f, 3.80 J/g of ΔH_c, and the 16% octadecane-treated fabrics had 7.46 J/g of ΔH_f, 7.44 J/g of ΔH_c. Also, the more octadecane was added, the less water vapor and air permeability had the fabrics because many open spaces were covered due to the microcapsules after octadecane treatment. It might influence on clothing microclimate. However, the 8% octadecane-treated garment (G1) exhibited less differential skin temperature and humidity and clothing microclimate temperature than the 16% octadecane-treated garment (G2) even though the octadecane concentration was lower. It means that the 8% octadecane-treated garment exhibited better thermal performance than the 16% octadecane-treated garment. This is because the higher octadecane concentration caused the fabric to become stiffer, thereby causing the still air layer to decrease the thermal insulation efficiency and the octadecane treatment was not affected. It differed from the result of the thermal properties (ΔH_f and ΔH_c) of the octadecane-treated fabrics. The reason for this result is that when the thermal manikin wore the octadecane-treated garments, various factors had effects on thermal properties such as environmental aspects, physiological aspects, and clothing aspects.     

不同乳化剂种类和浓度对正十八烷 @ 碳酸钙 相变微胶囊的性能影响

采用自组装法成功制备了以正十八烷为芯材,碳酸钙(CaCO_3)为壁材的相变微胶囊复合材料。用傅里叶变换红外光谱(FTIR)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了相变胶囊的化学组成和形貌,差示扫描量热仪(DSC)、热重分析仪(TG)和导热系数仪(TCM)对其热性能进行了表征。制备过程中,乳化剂的种类与浓度影响CaCO_3壳的相貌,微胶囊包封率、热稳定性以及热导率等性质。当乳化剂为十二烷基苯磺酸钠(SDBS)时,形成的CaCO_3壳为球霰石相;乳化剂为十二烷基硫酸钠(SDS)时,球霰石和方解石相均生成。DSC和TG结果表明,与SDS作为乳化剂制备的微胶囊相比, SDBS制备的微胶囊包封率更高,但热稳定性有一定下降。制备得到的正十八烷@CaCO_3相变微胶囊热导率比正十八烷的热导率最高可增加497.3%。当SDBS的摩尔浓度为0.75 mol/L时,制得的相变微胶囊材料的包封率可达到35.5%,热导率可提高290.7%。综上, SDBS更适合作为乳化剂用来制备用于热能存储的正十八烷@CaCO_3相变微胶囊。     

十八酸对正十八烷微胶囊的过冷行为及性能的影响

为了抑制正十八烷相变材料微胶囊的过冷行为,利用原位聚合法制备了添加十八酸的以正十八烷为芯材、氨基树脂为壁材的相变材料微胶囊,并利用傅里叶红外光谱仪(FTIR)、冷场扫描电镜(SEM)、差示扫描量热仪(DSC)、热重分析(TG)和X-射线衍射仪(XRD)等手段对微胶囊的结构、形貌、热性能及结晶性能等进行表征。结果表明:十八酸的添加使正十八烷微胶囊表面光洁度变差,过冷现象明显减弱;当十八酸的加入质量为芯材的4.2%时,过冷度从22.6℃降至10.0℃,异相成核结晶峰占比ΔHcα/ΔHc和包覆率分别达到75.2%和57.0%,且不影响微胶囊的耐热性能。这表明十八酸是正十八烷微胶囊较理想的过冷抑制剂。     

相变材料纳米胶囊的制备与性能

以正十八烷和环己烷为囊芯．三聚氰胺-甲醛树脂为囊壁材料。原位聚合法合成了平均粒径为0．77um的相变材料纳米胶囊。并在120℃～180℃对其进行热处理30min。通过SEM、DSC、DTA和TG等手段对纳米胶囊的性能进行分析发现。pH值对纳米胶囊乳液的稳定性影响很大．并影响到纳米胶囊的外观；环己烷的加入对未经热处理的纳米胶囊的表面形貌没有影响，但对结晶成核有很大影响；热处理温度影响纳米胶囊的热稳定性。在120℃～160℃处理温度范围内．热稳定性随热处理温度升高而升高．热处理温度超过160℃后。继续提高热处理温度．热稳定性降低．其中160℃热处理获得的纳米胶囊的耐热温度在200℃以上。     

基于RKPM的n-octadecane熔化过程光热特性数值模拟与验证

建立求解一维半透明材料相变过程的辐射导热耦合计算方法,了解正十八烷(n-octadecane)在辐射源作用下的相变熔化过程,获得材料内部温度分布,验证数值方法准确性。基于无网格RKMP方法,采用修正等效热容法处理相变潜热的吸收与释放,利用梯度折射率的方法处理变折射率介质内的辐射传输问题。实验测量了n-octadecane在红外辐照加热条件下的熔化过程温度响应特性。结果表明数值模拟值和实验值在温度水平和时间特性两方面都符合良好,验证了计算方法具有良好的精度。     

氟化相变微胶囊的制备与表征

采用悬浮聚合法合成了以聚苯乙烯 (PS)、聚 4-氟苯乙烯 (P4FS) 和聚 2,3,4,5,6-五氟苯乙烯 (PPFS) 为壳材, 正 十八烷 (OD) 为芯材的新型相变微胶囊材料 (PS@OD、P4FS@OD 和 PPFS@OD)。对微胶囊的疏油疏水性能和热物 性进行了表征。结果表明, P4FS@OD 和 PPFS@OD 微胶囊的油接触角和水接触角均高于 PS@OD 微胶囊且分别为 82.1^?/87.3^? 和 138.5^?/146.7^?, 其平均相变焓相比 PS@OD 微胶囊分别提升了 48.6% 和 101.9%, 达到 (125.6±1.6) J/g 和 (170.6±2.2) J/g。其中 PPFS@OD 微胶囊的平均粒径最小且为 (460±13) nm。综上, 引入含氟壳材使得相变微胶 囊具有良好储热性能和疏油疏水性能, 在清洁材料、储能、恒温建筑等方面有广阔的应用前景。     

正十八烷/泡沫相变复合材料蓄热实验研究

通过实验对相变复合材料的相变过程进行研究,将相变材料正十八烷(C18)分别填充到泡沫铜和泡沫碳中来提高相变材料的导热性能,采用差示扫描量热法(DSC)分析了正十八烷相变材料的热物性。利用相变蓄热装置对三种不同材料(C18、C18/泡沫碳、C18/泡沫铜)进行蓄放热对比实验,记录温度测试数据,分析这三种不同材料的温控性能与蓄热能力,并与正十八烷的结果对比。结果表明:泡沫材料的填充大幅提高相变材料的温控性能,使蓄热装置温度分布更均匀。     

白蚁防治剂毒死蜱乳油中有效成分毒死蜱的气相色谱分析

本论述了白蚁防治剂毒死蜱乳油中有效成分的气相色谱分析方法,测定了乳油中有效成分毒死蜱的定量校正因子。回收率实验结果表明本法适用于毒死蜱乳油中毒死蜱的定量分析。