EPDM对CL-20的包覆及表征

以CL-20为主体炸药、EPDM为黏结剂,采用水悬浮法制备了CL-20基PBX炸药,用SEM、XRD和FT-IR对产物进行了表征,并测试了其撞击感度和热安定性。结果表明,该包覆工艺可使EPDM成功地包覆在CL-20表面,在包覆过程中CL-20晶型没有发生变化。与原料CL-20相比,包覆样品的撞击感度明显降低,特性落高由15.9cm提高到40.7cm,热安定性更好。

EPDM/MMA-St-An悬浮接枝共聚合反应行为与AEMS冲击性能的研究

以三元乙丙橡胶(EPDM)与共单体(M)甲基丙烯酸甲酯(MMA)、苯乙烯(St)和丙烯腈(AN)为原料,以悬浮接枝共聚合法合成了接枝共聚物EPDM-g-MAS,用其与SAN树脂共混制备了耐老化黄变性能优异的高抗冲塑料AEMS。研究了EPDM/M悬浮接枝共聚合的反应条件对单体转化率(CR)、接枝率(GR)、接枝效率(GE)以及AEMS冲击性能的影响。结果发现,EPDM/M悬浮接枝体系具有较高的CR、GR和GE,在适宜的聚合条件下,CR、GR和GE分别最高可达95.7%、75.3%和94.3%。接枝产物EPDM-g-MAS对SAN树脂具有显著的增韧作用。当EPDM/AEMS质量百分率为15%,AEMS的悬臂梁缺口冲击强度高达29.5kJ/m2。SEM分析表明,当EPDM含量低时,AEMS的增韧机理为裂纹支化及终止机理,当EPDM含量高时为裂纹终止与轻度剪切屈服机理。TG和热氧老化试验分析表明,AEMS比AES有更好的热稳定性和耐热氧老化黄变性能。

含不同金属离子的EPDM磺酸盐离聚物的研究

合成了含不同金属离子Na^+、Mg^(2+)、Zn^(2+)和Al^(3+)的四种乙丙三元共聚物(EPDM)磺酸盐离聚物,红外光谱和氧瓶燃烧法测定了磺酸基的存在和含量。动态力学结果表明,离聚物中碳酸盐基团可能以多重离子对形式聚集;热重法指出,EPDM磺酸盐的热稳定性为钠盐>锌盐>镁盐>铝盐。考察了它们在二甲苯-正己醇混合溶剂中,比浓粘度随浓度、温度变化的规律,初步分析了各种金属盐的差异及其原因。

EPDM硫化橡胶的热稳定性研究

对ＥＰＤＭ的过氧化物硫化、硫黄硫化和含硫化合物硫化以及两种不同硫化体系并用的硫化胶热稳定性进行比较，优选热稳定性较好的硫化体系用于产品的制造。采用过氧化二异丙苯（ＤＣＰ）硫化的硫化胶虽具有极好的热稳定性，但其耐撕裂性能较差，且价格较高。因此可考虑采用ＤＣＰ的并用硫化体系。当ＤＣＰ用量为５份，硫黄用量不超过１份时，硫化胶具有较好的热稳定性。

喷雾干燥法制备ε-CL-20/EPDM复合炸药及其性能表征

以ε-CL-20(六硝基六氮杂异伍兹烷)为主体炸药,三元乙丙橡胶(EPDM)为胶粘剂,采用喷雾干燥法制备了ε-CL-20基PBX(聚合物粘接炸药)。研究结果表明:通过喷雾干燥法可使EPDM成功包覆在CL-20晶体表面,制得的包覆产物为ε-CL-20/EPDM复合炸药;与细化CL-20相比,ε-CL-20/EPDM的撞击感度明显降低,包覆样品的特性落高(H50)值从25.12 cm升至41.36 cm,表观活化能由182.58 k J/mol增至230.24 k J/mol,热爆炸临界温度由244.18℃增至245.60℃,说明ε-CL-20/EPDM复合炸药的热稳定性更好。

CSM对EPDM硫化胶耐热氧稳定性的影响

用热空气老化试验、差示扫描量热法和热重分析法研究添加少量氯磺化聚乙烯（ＣＳＭ）的ＥＰＤＭ硫化胶的热氧稳定性。结果表明：添加ＣＳＭ的ＥＰＤＭ硫化胶第一分解阶段的活化能低于未添加ＣＳＭ硫化胶的，而第二分解阶段的活化能却高于未添加ＣＳＭ硫化胶的。这说明，添加ＣＳＭ能提高ＥＰＤＭ硫化胶耐长期热氧老化性能。

PP／EPDM共混物热氧稳定性研究

通过热氧加速老化的方法研究了不同的EPDM含量和抗氧剂对聚丙烯和三元乙丙橡胶共混物(PP/EPDM)热氧稳定性的影响。通过对老化前后试样的力学性能变化分析,热失重(TG)分析和扫描电镜(SEM)分析,结果表明:在热氧加速老化的初期,PP/EPDM共混物的拉伸强度随着时间的增长呈逐渐上升的趋势;在老化中期,共混物的拉伸强度变化不大;在老化后期,共混物的拉伸强度逐渐下降。在整个老化过程中,断裂伸长率都呈逐渐下降的趋势。而随着EPDM含量的增加,相应共混物的拉伸强度和断裂伸长率的下降减缓;相应共混物的分解温度得到较大的提高;抗氧剂的加入,能进一步提高共混物的热氧稳定性。

TBC对EPDM/PP阻燃化的影响

用氧指数(LOI)测定、力学性能测定、热失重分析(TGA)方法研究了TBC对三元乙丙橡胶(EPDM)/聚丙烯(PP)阻燃耐热性和力学性能的影响。结果表明,使用TBC,EPDM/PP的阻燃效果较好,TBC主要发挥气相阻燃作用。5%TBC的加入增加了共混体系的拉伸强度和断裂伸长率;但随着TBC用量的继续增加,拉伸强度和断裂伸长率都有所降低。加入TBC后,共混物的起始失重温度明显降低,但对EPDM/PP的热稳定性没有多大的影响,不影响EPDM/PP的正常使用。

悬浮法EPDM-g-MS/PS的冲击和耐候性能的研究

以三元乙丙橡胶(EPDM)、甲基丙烯酸甲酯(MMA)和苯乙烯(St)为原料,采用悬浮接枝共聚法合成了EPDM接枝MMA-St共聚物(EPDM-g-MS),再与聚苯乙烯(PS)树脂共混制备了EPDM-g-MS/PS(MES)高抗冲塑料。研究了接枝体系的单体配比(fMMA)和接枝产物所含MMA-St共聚物的共组成质量比(FMMA)对MES的缺口冲击强度的影响,以及MES的相结构与增韧机理、热稳定性和耐候性,并与苯乙烯-丁二烯-苯乙烯共聚物(SBS)/PS的性能进行了比较。结果表明:当fMMA为15%、FMMA为29.1%时,EPDM-g-MS对PS的增韧效果最好;当MES所含EPDM质量分数为30%时,其缺口冲击强度高达45.1 kJ/m2;在MES的微观结构中,橡胶相EPDM以具有包藏结构的分散相存在,MES的增韧机理为裂纹分支终止兼有轻度基体剪切屈服;而在SBS/PS中,橡胶相(聚1,4-丁二烯嵌段)以网络状连续相存在,其增韧机理为基体剪切屈服。MES的热稳定性和耐气候老化黄变性能显著高于SBS/PS。

EPDM/EG复合材料的阻燃性能和热稳定性

以可膨胀石墨为阻燃剂,制备三元乙丙橡胶/可膨胀石墨复合材料。采用极限氧指数、垂直燃烧、锥形量热和热重分析等测试手段,研究可膨胀石墨含量对复合材料阻燃性能和热稳定性的影响。结果表明,可膨胀石墨能够显著提升三元乙丙橡胶的阻燃性能和火安全性;当其添加量为40份时,复合材料阻燃性能最佳;可膨胀石墨对材料的热稳定性具有一定的贡献。

POSS改性EPDM耐烧蚀复合材料的制备及性能

由于高性能推进剂的广泛应用,导致固体火箭发动机燃烧室内的燃烧温度与工作压强不断升高,因此研制出性能更加优异的隔热层迫在眉睫。以三元乙丙橡胶(EPDM)为基体,气相纳米SiO2为补强填料,首次引入八甲基丙烯酰氧基丙基POSS(MA-POSS),经由过氧化物引发双键之间的自由基聚合反应,制备了POSS改性EPDM耐烧蚀复合材料。研究了MA-POSS与气相纳米SiO2的添加量对隔热材料的交联度、力学性能、热稳定性、耐烧蚀性能的影响。在POSS与气相纳米SiO2协同作用下,改性后的材料各项性能均有所提升。结果表明,当气相纳米SiO2含量为40份、MA-POSS为5份时,凝胶含量高达92.61%,拉伸强度为12.02 MPa;MA-POSS含量为3份时,复合材料的线性烧蚀率和质量烧蚀率最低,分别为0.296 mm/s和0.100 g/s。

Curing Mechanism of Condensed Polynuclear Aromatic Resin and Thermal Stability of Cured Resin

In order to improve the thermal stability of condensed polynuclear aromatic(COPNA) resin synthesized from vacuum residue, 1,4-benzenedimethanol was added to cure COPNA resin. The curing mechanism was investigated by proton nuclear magnetic resonance spectrometry, solid carbon-13 nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. Microstructures of the uncured and the cured COPNA resins were studied by scanning electron microscopy and X-ray diffractometry. The thermal stability of COPNA resins before and after curing was tested by thermogravimetric analysis. The element composition of the cured COPNA resin heated at different temperatures was analyzed by an element analyzer. The results showed that the uncured COPNA resin reacted with the cross-linking agent during the curing process, and the curing mechanism was confirmed to be the electrophilic substitution reaction. Compared with the uncured COPNA resin, the cured COPNA resin had a smooth surface, well-ordered and streamlined sheet structure with more crystalline solids, better molecular arrangement and orientation. The weight loss process of the uncured and cured COPNA resins was divided into three stages. Carbon residue of the cured COPNA resin was 41.65% at 600 ℃, which was much higher than 25.02% of the uncured COPNA resin, which indicated that the cured COPNA resin had higher thermal stability.

Thermal stability and curing kinetics of polycarbosilane fibers

Thermal stability and curing kinetics of polycarbosilane (PCS) fibers were studied by thermogravimetry (TG), Fourier transform infrared spectroscopy(FT-IR). Curing is an essential step in the preparation of SiC fibers and the properties of SiC fibers are affected greatly by curing conditions. TG measurement performed in air shows that mass gain starts at approximately 200℃ and PCS fibers are sensitive to oxygen. Curing with oxygen, which results in crosslinking on the surface, enabled PCS fibers to retain its shape during high-temperature pyrolysis. The curing of PCS fibers is oxidation of Si─H and Si─CH3, then Si─O─Si and Si─O─C bonds are formed. This is a first order reaction, with activation energy of 79.27 kJ/mol, and the pre-exponential factor is calculated as 3.07×106. The kinetics model was obtained and the experimental data of PCS fibers show good agreement with the kinetics model.

Preparation, Curing Reactivity and Thermal Properties of Titanium-doped Silicone Resins

Novel titanium-doped silicone resins were synthesized from low-cost silane monomers and tetrabutyl titanate as raw materials and hydrochloric acid as catalyst, with titanium element as dopant into principal chain of Si-O-Si. The resins were characterized by means of FTIR, IH NMR and 13C NMR spectra, their thermal properties and curing properties were investigated and their corresponding films were determined. The results show that the thermal stability and storage stability of the resins were influenced by the types of silane monomers containing dif- ferent carbon atomicities of organic group. The thermal stability of the titanium-doped silicone resin with a molar ratio of silane monomer B（n-propyl triethoxysilane） to silane monomer C（n-octyl triethoxysilane） being 1：1 is superior to that of the resin with a molar ratio of silane monomer B to silane monomer C being 1：3. However, the storage stability of the former is inferior to that of the latter. This work also showed that the synthesized titanium-doped silicone resins have the highest thermal stability up to 450--500℃ with an atomicity molar ratio of 1：4 of titanium to silicon in the reactants. But the best storage stability of the resin prepared from the reactants with an atomicity molar ratio of 1：6[n（Ti）：n（Si）] was obtained. The effect of the type and content of curing agent on the curing properties of the resin was also studied. Moreover, thermal mechanism and curing mechanism were proposed in this work.

SYNERGISTIC EFFECTS OF LAYERED DOUBLE HYDROXIDE WITH PHOSPHORUS-NITROGEN INTUMESCENT FLAME RETARDANT IN PP/EPDM/IFR/LDH NANOCOMPOSITES

Synergistic effects of layered double hydroxide （LDH） with intumescent flame retardanct （IFR） of phosphorusnitrogen （NP） compound in the polypropylene/ethylene-propylene-diene/IFR/LDH （PP/EPDM/IFR/LDH） nanocomposites and related properties were studied by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, limiting oxygen index （LOI）, UL-94 test, cone calorimeter test （CCT） and thermo-gravimetric analysis （TGA）. The XRD and TEM results show that the intercalated and/or exfoliated nanocomposites can be obtained by direct melt-intercalation of PP/EPDM into modified LDH and that LDH can promote the IFR additive NP to disperse more homogeneously in the polymer matrix. The SEM results provide positive evidence that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples during burning. The LOI and UL-94 rating tests show that the synergetic effects of LDH with NP can effectively increase the flame retardant properties of the PP/EPDM/NP/LDH samples. The data from the CCT and TGA tests indicate that the PP/EPDM/NP/LDH samples apparently decrease the HRR and MLR values and thus enhance the flame retardant properties and have better thermal stability than the PP/EPDM/LDH and PP/EPDM/NP samples.

Improvement of Mechanical and Thermal Properties of Polymeric Material

Aim of present work is to replace asbestos in thermal insulation by another percentage of non-toxic fillers such as silica. Different formulations of fillers were prepared and added to Nordel (Trade name assigned for ethylene, propylene and 1, 4-hexadiene elastomers). The physical and mechanical properties (after and before aging), and thermal properties of the prepared samples were investigated. The objective was to choose a new formulation with properties that resemble as closely as possible those of the originally used in thermal insulation. After measuring the properties of tensile strength, elongation, hardness, specific gravity, compression set, rebound resilience, thermal conductivity, and initial and final decomposition temperatures, the sample that had values very close to those of the originally used in thermal insulation was chosen and recommended to be used. From comparison it was found that EPDM rubber with 50% silica gave the optimum properties closest to the originally used.

Study of catalytic effect of ammonium molybdate on the bisphthalonitrile resins curing reaction with aromatic amine

A kind of catalyst, ammonium molybdate was developed in this paper to promote the curing reaction of bisphthalonitrile resins with aromatic amine as curing agent, and the catalytic effect was studied by differential scanning calorimetry （DSC）, rheometric measurements and thermogravimetric analysis （TGA）. The results indicated that the catalyst could improve the curing rate and increase the curing degree, which could be regulated by the content of the catalyst used in the reaction.

SYNTHESIS,CHARACTERIZATION OF DIAMIDE-DIIMIDE-DIAMINES BASED ON L-CYSTEINE AMINO ACID AND THEIR EFFECT ON THE THERMAL PROPERTIES OF DIGLYCIDYL ETHER OF BISPHENOL-A(DGEBA)

The curing behavior of diglycidyl ether of bisphenol-A(DGEBA) with aromatic diamide-diimide-diamines having aryl ether,sulfone and methylene linkages was studied by differential scanning calorimetry(DSC).Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine(S) in a mixture of acetic acid and pyridine(3:2 V/V) followed by activation with thionyl chloride(SOCl_2) and then condensation with excess of diamines.Structural characterization...

Sawdust Short Fiber Reinforced Epoxidized Natural Rubber: Insight on Its Mechanical, Physical, and Thermal Aspects

In this work,Epoxidized natural rubber/sawdust short fiber(ENR-50/SD)composites at different fiber content(5,10,15 and 20 phr)and size(fine size at 60–100μm and coarse size at 10–20 mm)were prepared using two-roll mill and electrical-hydraulic hot press machine respectively.Curing characteristics,water uptake,tensile,morphological,physical,and thermal properties of the composites were investigated.Results indicated that the scorch time and cure time became shorter whereas torque improved as SD content increase.Though the decline of tensile strength and elongation at break values,modulus,hardness and crosslinking density have shown enhancements with the increasing of SD content.The water uptake percentage of all samples has shown an increasing as SD content increase.However,the low SD content,particularly fine size have presented lower water uptake.The temperature of weight%loss(5 and 50 wt%loss)of 5 phr SD(low content)have recorded higher temperature compared to 20 phr SD(high content)in the rubber composites,which indicated higher thermal stability.The fine size of SD has recorded better overall properties than SD coarse size at same loading in the rubber composites.

Modification of Operational Characteristics of Cold Curing Silicon Rubber

Technological aspects of modifying the operational characteristics of cold cured silicate rubbers have been developed. The effect of chromium oxide on the resistance of cold-curing silicone compounds to thermal aging, as well as on the physic mechanical properties and dielectric characteristics has been studied. The various content of ultrafine chromium oxide in cold-cured silicone compositions has been investigated, it’s optimal content in an amount of 2 - 5 mass at 100 mass, including low molecular weight rubber. Chromium oxide has been proven to improve the thermal stability of cold-cured silicone compositions. The manufacturing technology and component composition of the composition with high performance.