氧化镧对硅烷交联PE—LLD热性能的影响

通过热失重分析、示差扫描量热分析、氧化诱导期和维卡软化点测定等手段研究了稀土化合物氧化镧（La2O3）对硅烷交联线性低密度聚乙烯（PE—SXLLD）热性能的影响。研究结果发现，添加La2O3可极大地提高PE—SXLLD的热氧分解温度，但对其热裂解分解温度却没有影响，其作用机理可能是La2O3的存在减缓了氧分子在PE—SXLLD交联结构中的扩散运动，从而延缓了PE—SXLLD交联结构的链断裂反应。     

稀土氧化物对LLDPE热氧稳定性的影响

通过热失重分析不同稀土氧化物对LLDPE热氧分解行为的影响,并采用氧化诱导期、转矩流变分析方法研究了稀土氧化镧对LLDPE热氧分解行为的影响机理.结果表明:LLDPE的热氧分解温度在添加Eu2O3、Gd2O3、La2O3、Nd2O3、Sm2O3、Yb4O7、Pr6O11、Y2O3、Dy2O3得到提高,CeO2则对LLDPE的起始分解温度没有影响,而加入TbO2、Er2O3、Ho2O3则使LLDPE的起始分解温度降低.稀土氧化物对LLDPE的热氧稳定的影响可能与稀土元素与氧的配位作用有关,部分稀土氧化物可能通过与氧的配位作用而减缓了氧分子在LLDPE热氧化形成的交联结构中的扩散速度,从而提高了LLDPE热氧稳定性.     

化合物对乙丙弹性体/IFR体系阻燃性能和热降解行为的影响

采用氧指数测定仪、扫描电子显微镜、热重分析仪和红外光谱研究了化合物氧化镧（La2O3）和4A分子筛（4A）对膨胀阻燃茂金属乙丙弹性体（MEP/IFR）体系的阻燃性能和热降解行为的影响。结果表明,用化合物替代1 %的膨胀阻燃剂（IFR）后,能在一定程度上提高复合材料的极限氧指数值,其中4A分子筛的效果较好,达到28.6 %;添加化合物后,残炭的致密程度提高;2种化合物都能改善复合材料在高温下的热稳定性和残炭率,并能在残炭中形成了更多的聚芳烃和P—O—C、P—O—P的交联结构。     

Eu_2O_3/LDPE复合材料热性能及热氧分解动力学

通过热失重法、差示扫描量热法研究了氧化铕(Eu2O3)对低密度聚乙烯(LDPE)热氧分解行为的影响及复合材料的热分解动力学。结果表明:在添加Eu2O3后,LDPE在空气气氛下的热稳定性得到了提高;Eu2O3/LDPE复合材料的热氧分解反应为一级反应;Eu2O3的加入使得LDPE热氧分解表观活化能增大;添加Eu2O3并不会影响LDPE的氧化诱导期,说明Eu2O3对LDPE的热氧稳定机理与抗氧剂不同。     

氧化铕/高密度聚乙烯复合物热性能研究

本文通过热失重方法、差示扫描量热法研究了氧化铕对HDPE热氧分解行为的影响及复合物的热动力学。研究表明:添加氧化铕后,HDPE在空气气氛下的5%失重温度可大幅提高;热分解动力学分析表明,Eu2O3/HDPE复合物热分解反应为一级反应,氧化铕的加入使得HDPE热氧分解的表观活化能增大。添加氧化铕并不会影响HDPE的主链的无规断链反应,说明氧化铕对HDPE的热氧稳定作用与氧有关。     

La2O3/己二酸锌/聚甲基丙烯酸钙对PVC/ACS热稳定性的影响

为提高聚氯乙烯(PVC)/丙烯腈-氯化聚乙烯-苯乙烯共聚物(ACS)复合材料的加工热稳定性,制备了一种新型复合热稳定剂——氧化镧(La2O3)/己二酸锌/聚甲基丙烯酸钙对复合材料改性。用刚果红法研究了复合稳定剂对PVC/ACS热稳定性能的影响;用转矩流变仪、动态力学分析仪、冲击和拉伸试验机测定了不同m(Zn)/m(Ca)时添加La2O3对PVC/ACS试样的塑化行为、耐热性、动态力学和力学性能的影响。结果表明:m(Zn)/m(Ca)一定,添加La2O3后,复合材料的热稳定时间延长,玻璃化转变温度、力学性能均有所提高。当La2O3/己二酸锌/聚甲基丙烯酸钙的质量比为10∶6∶9时热稳定时间最长,达215 min。     

氧化镧和短玻纤填充对ABS热性能与机械性能的影响

研究通过开炼机辊压加工的方法将短玻纤(Glass-Fiber,GF)和氧化镧(La2O3)与原料ABS树脂共混,通过热性能和物理机械性能的测试表征研究了短玻纤所形成的搭接结构对ABS树脂性能的影响。测试结果表明:GF添加量升高,其50%热失重温度(T50%)较纯ABS最大会有8℃的提高,拉伸强度和冲击强度均呈逐步下降的趋势。在ABS/GF共混物中加入La2O3后其热性能和物理性能均有所下降。采用扫描电镜分析了GF在ABS中的分散情况,证明了GF的搭接方式和相容性对力学性能影响较大。     

铝硼硅酸盐硼挥发抑制的初步研究

通过热分析手段研究氧化镧对铝硼硅酸盐玻璃熔制过程中硼挥发量的影响。TG测试结果表明,随着玻璃配合料中氧化镧质量分数的增加,硼挥发量逐渐降低。当La2O3与B2O3摩尔比超过0.2时,这种趋势变化不明显。同时通过XRD分析出了不同热处理机制下,氧化镧和硼酸的混合物的产物在650,℃时,除了La2O3和H3BO3之外,还有新相LaBO3生成;800,℃时,产物为La（BO2）3。与碱土金属硼酸盐相比,La（BO2）3和LaBO3具有更低的饱和蒸汽压,这是硼的挥发量降低的根本原因。     

氢氧化铝对乙烯-丙烯酸丁酯共聚物力学与阻燃性能及热降解行为的影响

采用极限氧指数、热重分析（TG）和差示扫描景热分析（DSC）等技术和手段研究了乙烯-丙烯酸丁酯共聚物（EBA）／氢氧化铝（ATH）复合材料的阻燃性能和热降解行为，探讨了ATH的添加量对EBA力学性能和熔体流动速率的影响。实验数据表明，ATH的引入能恶化材料的力学性能和加工性能；但可提高材料的阻燃性能，当ATH的添加量为60％时，阻燃材料的极限氧指数可达33．1％。ATH提高了EBA在高温下的热稳定性，降低了EBA的热降解速率，扩大了热失熏温度范围。ATH以吸热方式在凝缩相和气相中发挥阻燃作用；此外，ATH分解形成的活性Al2O3对EBA还具有成炭催化作用，在一定程度上显示出了ATH的凝缩相阻燃作用。     

La2O3助剂对Ni/γ-Al2O3/堇青石结构化催化剂催化加氢合成间苯二胺性能的影响

研究助剂La2O3对Ni/γ-Al2O3/堇青石结构化催化剂结构与性能的影响。采用悬浮液涂层法、活性组分浸渍法制备不同La2O3助剂含量的Ni/γ-Al2O3/堇青石结构化催化剂。通过BET、XRD、TPR、XPS对催化剂进行表征,发现不添加La2O3助剂时活性组分以NiAl2O4形式存在,添加La2O3助剂后则以NiAl2O4和NiO两种形式存在,易还原NiO的生成提高了催化剂的活性。添加La2O3助剂还能使催化剂的比表面积降低和孔尺寸增大,活性评价表明助剂La2O3存在适宜添加量,即La含量为3%。同时发现助剂La2O3对选择性的影响大于活性,La2O3具有结构助剂的特点。     

Softening temperature of glassy polymers as affected by residual stresses

Heat deflection temperature and Vicat softening point of polystyrene and polymethylmethacrylate with various thermal histories were measured. Surface residual stresses were characterized by liquid crazing. Residual stress profiles across the sample thickness were also measured. It is suggested that the softening behavior of glassy polymers is affected by the state of the residual stresses in addition to the traditionally accepted free volume approach.     

氧化镧对LDPE热氧化分解行为的影响

通过热失重方法研究了氧化镧对低密度聚乙烯(LDPE)热氧分解行为的影响。结果表明:添加氧化镧后,LDPE在空气气氛下起始热氧分解温度可大幅提高;在LDPE失重率小于0.3时,氧化镧的加入使得LDPE热氧降解的表观活化能增大;而添加氧化镧并不影响LDPE主链的无规断链反应,因此氧化镧对LDPE的热氧稳定作用与氧有关。     

La_(0.8)Sr_(0.2)MnO_3的燃烧法制备及对HMX热分解的影响(英文)

Perovskite-type La0.8Sr0.2MnO3 was prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scaning electron micrograph (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of La0.8Sr0.2MnO3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by thermal gravity-differential scanning calorimetry (TG-DSC) techniques. The experimental results show that La0.8Sr0.2MnO3 is an effective catalyst for HMX thermal decomposition. The surface-adsorbed species such as H2O, OH&;#61485; and adsorbed oxygen (Oad) could result in an advance in the onset temperature of HMX thermal decompo-sition. The mixture system of Mn3+ and Mn4+ ions and lattice oxygen could play key roles for the increase of the decomposition heat of HMX because these exothermic reactions could be catalyzed by La0.8Sr0.2MnO3 between CO and NOx (from the thermal decom-position of HMX) and the oxidation reaction of CO. According to the previous researches and our results, perovskite-type La0.8Sr0.2MnO3 may be used as a novel catalyst or modifier for nitrate ester plasticized polyether (NEPE) propellant.     

Effects of butyl acrylate modified polypropylene on structural and thermal properties of foamed polypropylene

In this work, the melt strength of PP matrix was reinforced by crosslinking‐modified PP (CM‐PP) which was yielded by peroxide‐initiated crosslinking of linear PP with butyl acrylate (BA). The nano‐silica aerogel (nano‐SiO₂) worked as a nucleating agent for foaming. The effects of CM‐PP with the various contents of BA on the foaming behavior and thermal property of PP were studied by measurements of density, thermal conductivity, Vicat softening temperature and SEM. The results showed that the foamed PP got the best properties when the crosslinking PP modified with the weight ratio of butyl acrylate was 10 wt %. The density of the obtained foamed PP with uniform closed cells was as low as 0.23 g/cm³, the thermal conductivity was 0.044 W/(m K), and the Vicat softening temperature was 120 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44340.     

Properties of Poly(vinylchloride) Blended with an Emulsion Copolymer of N-p-Tolylmaleimide,Methyl Methacrylate,and Acrylonitrile

Abstract

Copolymers of N-p-tolylmaleimide, methyl methacrylate, and acrylonitrile were synthesized by the semibatch emulsion polymerization method and used for blending with poly(vinylchloride) (PVC) to improve its heat resistance. The thermal properties of the blends with different terpolymer content were investigated by differential scanning calorimeter (DSC), thermogravimatric analysis (TGA), and Vicat softening point tester (T _Vicat). The results showed that the glass transition temperature (T _g ), Vicat softening point, and thermal decomposition temperature of the blends increased with increasing terpolymer content. The tensile strength increased with an increase in the copolymer content. The results of the rheological behavior showed that the apparent viscosity ? _α decreased with increasing shear rate and increased with the copolymer content.     

Thermal stability in air of acrylonitrile-grafted polyethylene by electron beam prior irradiation

Studies were made of the thermal softening and degradation behavior in air of low- and high-density polyethylene (PE) grafted with acrylonitrile (AN) by electron beam prior irradiation in nitrogen. It was found that both LDPE and HDPE were made to exhibit higher softening points by grafting and that this tendency increased with increasing percent graft. The starting temperatures of the thermal degradation and thermogravimetric curves were also found to shift to higher temperatures. On the other hand, in marked contrast to the thermal softening and degradation behavior of grafted PE in air, its behavior in nitrogen showed substantial dependance on oxidative degradation, suggesting that the oxidation of PE was inhibited by polyacrylonitrile (PAN), which forms graft chains. It was considered that the oxidation-inhibiting mechanism of PAN produced in the amorphous regions prevents oxygen from dissolving and diffusing into the amorphous phase, thus inhibiting the oxidative degradation of PE, and that, when heated, PAN undergoes nitrile oligomerization and the nitrile oligomer end radicals act to trap those radicals which participate in PE oxidative degradation.     

Al2 O3对硼硅酸盐玻璃结构和性能的影响

硼硅酸盐玻璃具有优良的抗热冲击性能和优异的光学性能。主要探讨了Al2 O3对硼硅酸盐玻璃的结构和性能的影响。通过红外光谱测试分析了Al2 O3含量不同时玻璃的结构变化,测试了玻璃的热膨胀系数,转变温度、膨胀软化温度、粘度和化学稳定性。研究结果表明：Al2 O3的加入使得玻璃结构中[ BO4]减少,[ BO3]相应增加,从而使得玻璃结构疏松。玻璃的热膨胀系数增大,Tg 和膨胀软化点Td 降低,化学稳定性减弱;但玻璃的软化点Tf 在Al2 O3含量小于3%时,随Al2 O3含量增加有降低趋势,大于3%时随Al2 O3含量增加有增大的趋势。玻璃的高温粘度随Al2 O3的加入增大,但低温粘度减小。     

氧化物添加对Bi_2O_3–B_2O_3–ZnO低熔点玻璃结构与性能的影响

采用常规的熔体冷却法制备了以Bi2O3–B2O3–ZnO为基体,外加氧化物（SiO2、GeO2、TeO2和Sb2O5）的玻璃试样,对比研究了氧化物对玻璃结构、转变温度、软化温度、析晶温度、热膨胀系数、抗弯强度和化学稳定性的影响规律。结果表明：在基体中加入SiO2,对降低玻璃的热膨胀系数最有效;加入TeO2,对降低玻璃的转变温度和软化温度最有效;加入Sb2O5,不仅能降低玻璃的转变温度和软化温度,使ΔT最大,而且能改善铋酸盐玻璃在封接过程中易析晶的问题,热膨胀系数较低,抗弯强度最大,化学稳定性最好。通过利用Fourier红外光谱、X射线衍射和热分析研究了玻璃结构的变化。     

PVC/环氧树脂F51共混物性能的研究(二)

以554/504为固化剂,研究了不同固化时间下,F51用量对PVC/F51共混物的微观形貌、力学性能和维卡软化温度的影响。结果表明:①少量的F51在PVC基体中分散比较均匀,F51用量较多时会出现团聚现象;②少量的F51有利于提高PVC/F51共混物的力学性能和维卡软化温度,用量以2～6份为宜;③随着固化时间的延长,PVC/F51共混物的力学性能和维卡软化温度均提高;④固化剂554可进一步提高PVC/F51共混物的拉伸强度和弯曲强度,但会降低缺口冲击强度和维卡软化温度。     

Synthesis and characterization of terpolymer of N‐cyclohexylmaleimide,methyl methacrylate,and acrylonitrile

Terpolymers of N‐cyclohexylmaleimide, methylmethacrylate, and acrylonitrile (AN) at different AN feed content were synthesized by suspension polymerization. The thermal properties of the terpolymers such as glass transition temperature (T_g) and Vicat softening temperature (T_Vicat) were determined by torsion braid analysis and Vicat softening temperature tester, respectively. The value of T_g and T_Vicat decreased with increasing AN feed content. Thermogravimetric analyses were carried out with the results that the incorporated AN units enhanced the thermal stability of the resulting polymers and a second degradation step appeared with the addition of AN. The mechanical properties (tensile strength and impact strength) of the terpolymers were also detected and the results show that the tensile strength and impact strength of terpolymers increase with increasing AN feed content. The rheological results illustrated that the terpolymers showed rheological behavior similar to that of pseudoplastic liquid. The apparent shear viscosity decreased with the increasing of AN feed content. The flow power index n increased with increasing AN feed content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 792–796, 2007