干混工艺对PVC搪塑制品中纳米颗粒分布和性能的影响

通过增加室温混合阶段并优化关键工艺参数的方式改进了聚氯乙烯(PVC)搪塑粉料的传统混料工艺,针对粒径60~80nm的活性CaCO_3和粒径100~120nm的金红石型钛白粉等纳米颗粒,对比研究了新混料工艺和传统混料工艺对无机纳米颗粒均匀分散的影响,并定量分析了在室温混合阶段的不同工艺参数下PVC搪塑粉料的流动性和搪塑制品的力学性能及热稳定性。结果表明:优化后的干混工艺不仅有效提高了搪塑表皮中纳米颗粒分散均匀性和搪塑粉料的流动性,而且明显改善了搪塑表皮的断裂伸长率、热稳定性和耐热挥发损失性。     

PVC搪塑粉的热降解特征及其动力学研究

粉末搪塑表皮被广泛应用在各种中高档汽车仪表板上.为了优化设计搪塑粉、提高热加工性能从而促进高档汽车国产化,本文首先利用热重分析和裂解气相色谱/质谱实验探讨搪塑粉的热降解失重特征,分析升温速率、实验气氛和搪塑加工对其热降解行为的影响,继而结合X射线荧光光谱实验对其热降解动力学进行研究.结果表明:搪塑粉的热降解过程可分为3个阶段,PVC和增塑剂的相互作用使其热降解过程更加复杂;随升温速率的增加,热降解失重曲线向高温区偏移;搪塑粉在有氧气氛中更易发生热降解,失重率较大;与搪塑粉相比,搪塑表皮的热稳定性能得到一定程度的提升;第1热降解阶段氮气条件下的热降解活化能和反应级数较小.     

水滑石/钙锌复合热稳定剂对PVC的热稳定作用

本文制备了水滑石/钙锌复合热稳定剂,采用XRD、FT-IR及静态热老化、脱HCl等实验及分析手段,探讨了水滑石对PVC的热稳定机理,研究了水滑石/钙锌复合热稳定剂对PVC的热稳定性能。实验表明,水滑石对PVC热解释放的HCl进行吸附分两个过程,首先层板羟基与HCl反应,然后层间CO32-与Cl-进行交换,可明显改善PVC的热稳定性,使PVC脱HCl的诱导时间提高了1.4倍。     

热稳定剂对PVC抑烟作用及其机理研究

利用烟密度箱、TG、GC-MS等分析技术研究了钙锌、铅盐和有机锡热稳定剂对PVC的抑烟作用及对燃烧过程中主体凝聚相和释放的芳烃化合物的影响,并探讨了钙锌稳定剂的抑烟机理。结果表明:这三类热稳定剂对PVC均有一定的抑烟作用,其中钙锌稳定剂的抑烟作用更为明显。钙锌稳定剂通过燃烧过程中生成的ZnCl2改变PVC热降解历程:一方面抑制分子内环化反应,减少有害芳烃化合物的生成;另一方面能促进分子间交联反应,提高残炭量,起到抑烟作用。     

桐酸基C22三元酸钙盐的制备及其PVC复合热稳定体系优化设计

以桐马酸酐——C22三元酸单甲酯(MEMAA)为原料,采用复分解反应合成了桐酸基C22三元酸钙盐(TOTC),并利用FTIR表征其结构。通过刚果红法和热老化烘箱法考察了亚磷酸三苯酯(TPP)﹑季戊四醇(PER)、β-二酮(DT)对桐酸基C22三元酸钙/硬脂酸锌体系初期着色性及热稳定性的影响,在此基础上通过正交实验完成了桐酸基C22三元酸钙锌复合热稳定剂体系的配方优化设计。结果表明:TOTC、ZnSt2、DT、TPP、PER的质量比为48∶12∶2∶5∶10时,钙锌复合热稳定剂体系热稳定性最佳。在100g PVC/40g DOP体系中加入最佳配方条件下的桐酸基C22三元酸钙锌复合热稳定剂3g,185℃下静态热稳定时间可达50min,热稳定性优于部分国内市售产品,与德国熊牌钙锌复合热稳定剂相当。     

聚氯乙烯搪塑粉塑化成型与温度的相关性

采用HAAKE流变仪和熔体流动速率测定仪,研究了在不同温度下2种聚氯乙烯搪塑粉MT1和MT2的塑化性能和熔体流动速率。结果发现,搪塑粉塑化时最大扭矩和塑化时间与温度呈明显的相关性,在180℃以下,温度越高,搪塑粉塑化扭矩越小,塑化时间越短;在相同温度下,MT2搪塑粉比MT1搪塑粉具有更高的塑化效率和更优异的熔融性能。通过偏光显微镜观察了2种搪塑粉在不同温度的熔融合并过程,展示了搪塑粉在熔融过程中的形貌演变特点,并定量计算了不同温度下2种搪塑粉熔融的相对铺展面积和速率。通过自制的搪塑机和模具制造了2种搪塑表皮,其搪塑成型性能与上述的实验结果能够很好地吻合。该研究有助于搪塑工艺和材料的优化设计。     

2-氨基烟酸镧的合成对聚氯乙烯热稳定性的影响

通过2-氨基烟酸(2-ANA)、硝酸镧和氢氧化钠的复分解反应合成了2-氨基烟酸镧(2-LANA),并研究了其对聚氯乙烯(PVC)热稳定性能的影响。结果表明,2-LANA提高了PVC的热稳定性能,使PVC的静态和动态稳定时间分别延长至27 min和27.45 min。将2-LANA与硬脂酸锌(ZnSt₂)、硬脂酸钙(CaSt₂)、季戊四醇(PE)进行一种或两种以上复配来探究其复配热稳定剂的热稳定性能,当2-LANA∶ZnSt₂∶PE=2∶1∶2时,其静态和动态热稳定时间分别为66 min和64.91 min,并且PVC降解表观活化能(Ea)最高为169.73 kJ/mol,说明其可以使PVC降解反应更难发生;当2-LANA∶Ca/Zn稳定剂∶PE=1∶1∶3时,其抗变色性能、流变性能和力学性能最佳,增强了PVC加工过程的稳定性和延展性。说明2-LANA与其他稳定剂存在明显的协同作用。2-LANA能够吸收PVC降解释放的HCl气体,生成LaCl₃,减弱了HCl对PVC降解的催化作用,能有效地阻止PVC链...     

2-氨基烟酸镧铈对PVC热稳定性的影响

以2-氨基烟酸(2-ANA)、Ce(NO₃)₃、La(NO₃)₃和NaOH为原料,合成出2-氨基烟酸镧铈(2-LCANA),研究2-LCANA及其复配稳定剂对聚氯乙烯(PVC)热稳定性能、流变性能和力学性能的影响。结果表明,2-LCANA及其复配稳定剂提高了PVC的热稳定性能,当m(2-LCANA)∶m(ZnSt₂)∶m(PE)=2∶1∶2时,其热稳定时间为38 min,可以减小在加工过程中的损耗,增强PVC的力学性能,但是随着温度升高2-LCANA要比m(2-LCANA)∶m(ZnSt₂)∶m(PE)=2∶1∶2的复配稳定剂抑制PVC降解反应发生更有效。2-LCANA能够吸收PVC降解释放的HCl气体,生成LaCl₃和CeCl₃,减弱了HCl对PVC降解的催化作用,可以有效地阻止PVC链上C-Cl和与氯相连的C-H断裂,减少共轭双键的生成,减缓PVC变色,延缓了PVC的热降解。     

PVC/TPU共混材料的制备及性能

采用机械共混的方法制备了聚氯乙烯(PVC)/热塑性聚氨酯弹性体(TPU)共混物,进而通过与无机填料的填充复合,成功制备了PVC/TPU/高岭土复合材料,实现了PVC的增强增韧。探讨了TPU、热稳定剂、无机填料等对PVC/TPU共混材料力学性能和耐油耐溶剂性能的影响,分析了共混物的流变性能和热失重情况,并观察了共混物的断面形貌特征。结果表明,PVC/TPU/改性高岭土为80/16/4,邻苯二甲酸二辛酯(DOP)为8份,有机锡热稳定剂为3份时,综合性能大幅度提高:其拉伸强度比PVC提高了1.4倍,断裂伸长率提高了12.6倍,无缺口冲击强度提高了3.97倍,热稳定性和加工性能也得到改善。     

颗粒形态对聚氯乙烯(PVC)塑化性能及热稳定性的影响

本研究分析了部分市售国产电石法PVC树脂和乙烯法PVC树脂颗粒形态的差异,研究了颗粒形态的差异对PVC树脂加工性能和产品品质的影响.研究显示,不同市售PVC树脂的表面形貌较为接近,但粒径分布和孔隙分布则存在差异;粒径越大,PVC制品产生更多的"鱼眼",热稳定性明显降低;孔隙率增加则提高了树脂的塑化性能.     

竹炭和壳聚糖对聚氯乙烯基木塑复合材料界面性能的影响

以杨木粉为填充材料,聚氯乙烯（PVC）为基体材料,添加竹炭和壳聚糖,采用挤出成型制备竹炭和壳聚糖改性木粉/PVC木塑复合材料,采用SEM观察复合材料表面微观形貌,采用综合热分析仪分析复合材料的热稳定性,采用FTIR分析其官能团变化,测试了木粉/PVC木塑复合材料的力学性能。结果表明:复合添加竹炭和壳聚糖可较好地改善木粉和PVC的界面作用力和界面相容性,提高复合材料的力学性能,其拉伸强度、冲击强度、弯曲强度和弯曲模量分别比未添加增加14.6%、28.8%、11.1%和4.85%,且复合材料的微观界面缺陷较少;竹炭可提高复合材料的热稳定性,复合添加竹炭和壳聚糖可增加复合材料中羟基、氨基和亚甲基的数量,减弱碳氯键的结合强度,从而增强复合材料中木粉和PVC的界面结合力。      

Mechanochemical decomposition of PVC by using La2O3 as additive

A polyvinyl chloride (PVC, [CH2CHCl]n) sample was ground with one of the following oxide samples, lanthanum oxide (La2O3) and calcium oxide (CaO), as a reference, to investigate its mechanochemical (MC) decomposition. According to the XRD patterns for the ground products, peaks of lanthanum oxy-chloride, LaOCl which is water insoluble, were observed to appear in the patterns of the mixture samples at a molar ratio of (PVC: La2O3 = 1:2) and (1:4), after 20 min grinding, while the patterns of the ground PVC-CaO mixtures show the formation of CaOHCl, which is water soluble, in the products after 2 h grinding. TG patterns taken for the PVC-La2O3 mixtures ground for different periods of time do not indicate significant weight loss in the range from 200 to 300 degrees C, and this suggests that La2O3 is more effective additive than CaO in the MC decomposition for PVC. FT-IR patterns for organic phases in the ground mixture show the reduction of CCl bindings in the PVC structure. The MC reaction between PVC and La2O3 is accompanied by the formation of C-O single bonds, to form LaOCl, which is insoluble in water at ambient condition. This is the reason why the yield of Cl extracted by the water leaching reaches only less than 50%, while it reaches almost 100% in the yield of Cl from the PVC-CaO mixture ground for 2 h or more.     

Numerical study of flow and heat-transfer characteristics of cryogenic slush fluid in a horizontal circular pipe (SLUSH-3D)

Cryogenic slush fluids, such as slush hydrogen and slush nitrogen, are two-phase, single-component fluids containing solid particles in a liquid. Since their density and refrigerant capacity are greater than those of liquid-state fluids alone, there are high expectations for use of slush fluids as functionally thermal fluids in various applications, such as fuels for spacecraft engines, clean energy fuels to improve the efficiency of transportation and storage, and as refrigerants for high-temperature superconducting equipment. In this research, a three-dimensional numerical simulation code (SLUSH-3D), including the gravity effect based on the thermal non-equilibrium, two-fluid model, was constructed to clarify the flow and heat-transfer characteristics of cryogenic slush fluids in a horizontal circular pipe. The calculated results of slush nitrogen flow performed using the numerical code were compared with the authors’ experimental results obtained using the PIV method. As a result of these comparisons, the numerical code was verified, making it possible to analyze the flow and heat-transfer characteristics of slush nitrogen with sufficient accuracy. The numerical results obtained for the flow and heat-transfer characteristics of slush nitrogen and slush hydrogen clarified the effects of the pipe inlet velocity, solid fraction, solid particle size, and heat flux on the flow pattern, solid-fraction distribution, turbulence energy, pressure drop, and heat-transfer coefficient. Furthermore, it became clear that the difference of the flow and heat-transfer characteristics between slush nitrogen and slush hydrogen were caused to a large extent by their thermo-physical properties, such as the solid–liquid density ratio, liquid viscosity, and latent heat of fusion.     

ZnO/CaCO3复合材料的制备及其在丁苯橡胶硫化中的应用

采用液相沉淀法制备了ZnO/CaCO₃复合粉体,考察了工艺参数对形貌和分散状态的影响,分析了ZnO在CaCO₃表面的组装过程和ZnO的生长方式,测试了复合粉体的硫化活化性能。研究结果表明:当ZnO和CaCO₃质量比为1∶2,沉淀反应物物质的量的配比为1∶1,煅烧温度为300~350℃时,ZnO/CaCO₃复合粉体比表面积可达19.827 m²/g且有着良好的分散状态,CaCO₃表面ZnO的粒径较小(5~10 nm)。在CaCO₃表面上反应生成的羟基磷灰石对Zn²⁺的吸附的作用是将ZnO与CaCO₃成功组装在一起的关键,也是ZnO沿垂直CaCO₃表面方向生长的原因。将复合粉体应用于丁苯橡胶硫化中,硫化时转矩值最高达10.07 dN·m,硫化速率CRI最快为0.247 s^-1。     

Development and characterization of nanostructured-perlite-cementitious surface compounds

The effect of perlite loading on the thermal resistivity, solar reflectance and indirect tensile strength of Nanostructured Cementitious Binder is studied. The main objective of this research is to constitute structural lightweight surface compounds and to improve their thermal resistivity and reflectivity with suitable mechanical performances as a surface compound. Portland White Cement (PWC) was partially substituted by nano clay. An optimum blend of type I PWC, and nano clay was determined based on indirect tensile strength. The perlite dosage was added to the optimum cement-nano clay blend at different ratios (10, 20, 30, 40, 50, 60 and 70%) by weight. Superplasticizer with different ratios was used to study the performance of the 70% perlite mixture. The mixes were prepared using water of consistence. The wet compounds were molded in PVC molds and left for 24 h, then demolded and cured in humid air (20 ± 1 °C & 100% RH) for 28 days. The molds are 50 mm in diameter and 27 mm height. The thermal resistivity and indirect tensile strength of the different compounds were evaluated for the cured samples at 7 and 28 days. It was found that the 2% nano clay improved the indirect tensile strength of the neat PWC. As expected the addition of the perlite has reduced the indirect tensile strength but increased the thermal resistivity of the compound by 250%. The increase of perlite loading has not affected the solar reflectivity of the compound. Sokalan HP 80 polycarboxylate ether superplasticizer was successfully used to recover about 50% of the loss in the indirect tensile strength of the newly formulated Nanostructure Perlite Cementious Surface Compounds (NPCSC) containing 70% perlite loading.     

Effect of stabilizer on fatigue resistance of a polyoxymethylene (acetal) copolymer

Acetal is known for its fatigue resistance, however, it is also susceptible to degradation at high temperatures. Commercial resins therefore contain complex stabilizer systems that, although present in relatively small amounts, provide thermal stability both for processing and subsequent in-service aging. The present study was undertaken to determine how sensitive the fatigue resistance of an acetal copolymer was to changes in stabilizer concentration. Blends containing a series of increasing stabilizer levels were investigated and compared to the commercial material. Fatigue resistance was assessed using accelerated fatigue crack propagation rate measurements for injection molded plaques. Results demonstrate that the fatigue resistance is dependent upon the amount of stabilizer and in fact suggest that a critical level of stabilizer is needed to provide adequate fatigue resistance in the molded part. It is also shown that room temperature aging further aggravates the poor fatigue resistance of samples with low stabilizer levels. Moreover, the results from this study demonstrate that the varying concentrations of heat stabilizer affect even short term mechanical properties such as tensile modulus, strength, and elongation to fail. In addition, fracture toughness tests clearly distinguish the various materials. The short term mechanical tests provide added support that a critical concentration of stabilizer exists.     

Study on the development of a capacitance-type flowmeter for slush hydrogen

Slush hydrogen is a two-phase solid–liquid cryogenic fluid consisting of solid hydrogen particles in liquid hydrogen, various applications for which are anticipated, including fuel for reusable space shuttles. Noting the slight fluctuation in the distribution of solid hydrogen particles in slush hydrogen, i.e., slush hydrogen density, the authors of the current study placed capacitance-type densimeters at two locations along the piped flow to measure the density and to detect density fluctuations. The flow velocity was also calculated from the densimeter distance and delay time when the cross correlation function of the two density signals was at a maximum. This capacitance-type flowmeter has no moving mechanical parts and no probe in the flow stream. This paper reports the development of a prototype slush hydrogen capacitance-type flowmeter, together with the fabrication of required test equipment, and confirmation of flowmeter accuracy.