Investigation of hydroxyl-terminated polybutadiene propellant breaking characteristics and mechanism impacted by submerged cavitation water jet

A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.

SYNTHESIS OF HYDROXYL-TERMINATED POLYBUTADIENE POSSESSING HIGH CONTENT OF 1,4-UNITS VIA ANIONIC POLYMERIZATION

The hydroxyl-terminated polybutadiene （HTPB） possessing high content of 1,4-units was synthesized by anionic polymerization of butadiene, using alkyllithium containing silicon-protected hydroxyl group as initiator and cyclohexane as solvent. The polymers were characterized by GPC, IR and 1H-NMR. The mechanical properties of cured films were also evaluated. The results show that the content of 1,4-units for HTPBs made by anionic polymerization reaches up to 90%. The molecular weight distribution is very narrow （〈 1.05）. The functionality of hydroxyl groups approaches 2. Compared with free radical HTPB, the elongation at break of anionic HTPB films increased by 70%, while the tensile strength remained nearly unchanged. This new HTPB can be very useful in solid propellant.

Anti-corrosive, weatherproof and self-healing polyurethane developed from hydrogenated hydroxyl-terminated polybutadiene toward surface-protective applications

Self-healing polyurethane(PU)faces aging deterioration due to active dynamic bonds,which remain a challenging predicament for practical use.In this work,a novel strategy is developed to address this predicament by leveraging the hydrophobicity and gas barrier of hydrogenated hydroxyl-terminated polybutadiene(HHPB).The dynamic oxime-carbamate bonds derived from 2,4-pentanedione dioxime(PDO)enable the elastomer to exhibit surface self-repairability upon applied mild heat and achieve~99.5%mechanical self-healing efficiency.The mechanical properties remained nearly intact after 30-d exposure to thermal oxidation,xenon lamp,acids,bases,and salts.Gas permeability,positron annihilation lifetime spectroscopy(PALS),and contact angle measurements reveal the pivotal role of gas barrier,free volume,and hydrophobicity in blocking undesirable molecules and ions which effectively protects the elastomer from deterioration.HHPB-PU also exhibits excellent adhesion to steel substrate.The shear strength achieves(3.02±0.42)MPa after heating at 80°C for 4 h,and(3.06±0.2)MPa after heating at 130°C for 0.5 h.Regarding its outstanding anti-corrosive and weatherproof performances,this self-healable elastomer is a promising candidate in surface-protective applications.

Degradation of Disposal Hydroxyl-Terminated Polybutadiene Composite Solid Propellant

With the greatly increasing amount of discarded hydroxyl-terminated polybutadiene(HTPB)propellant year by year,it is of high significance to study the safe,efficient and environmental processing method of disposal HTPB propellant.In this paper,the decomposition agents are formulated for degrading the waste composite solid propellant.It is found that the following formulations of butanone 25%-55%,xylene 30%-75%,deionized water 40%-45%have effective influence on the degradation of the waste composite solid propellant.The proper degradation time is found to be about 7-8 h.With the help of infrared spectrum analysis,scanning electron microscope imaging,thermogravimetric analysis and solvent viscosity test,it was proved that after degradation reaction on the propellant sometimes,a large number of irregular fractures occurred in bulk resulting from effective degradation.The characterization of the propellant after degradation showed that the hardness of the propellant decreased,the viscosity increased,and a large number of holes and cracks appeared on the surface.The results showed that the formulated degradation agent and degradation condition perform good degradation effects on HTPB solid propellant.

MORPHOLOGY OF POLYBUTADIENE “SHISH KEBABS”

Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been studied in detail.The higher the molecular weight the faster the sample crystallizes.

CURE CHARACTERISTICS OF HYDROXYL TERMINATED POLYBUTADIENE PREPOLYMER WITH BLOCKED TOLUENE DIISOCYANATE-Ⅱ

Cure characteristics of hydroxyl terminated polybutadiene (HTPB) prepolymer with avariety of blocked toluene diisocyanate (TDI) in the presence of triethylamine (TEA) andchloroacetic acid catalyst are reported. Phenol, thiophenol, p-chloropheno1, p-nitrophenol,p-cresol, resorcinol, naphthols, caprolactam and butylated-hydroxytoluene were used as blockingagents. Viscosity measurements have been carried out using a mixture of HTPB and blocked TDIin cyclohexanone in the presence of the catalysts at 50℃ and 60℃ using Haake rotational vis-cometer. Viscosity measurements have also been carried out with 50% solids such as ammonium sulphate along with HTPB and TDI adduct.

SYNTHESIS OF POLYBUTADIENE MACROINITIATOR AND POLYBUTADIENE/POLYACRYLAMIDE BLOCK COPOLYMERS

An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamide (AAm) in benzene to form polybutadiene/polyacrylamide (PBD/PAAm) block copolymers. High conversion of AAm was obtained over a wide range of monomer/macroinitiator ratios. The PBD/PAAm block copolymers were found to have excellent solvent resistance.

Citrus oils as chain transfer agents in the cross-metathesis degradation of polybutadiene in block copolymers using Ru-alkylidene catalysts

The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agents (CTAs) using Rualkylidene catalysts (PCy3)2(Cl)2Ru = CHPh (I) and (1,3-diphenyl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II) was studied. Terpene-terminated butadiene oligomers and polystyrene blocks were obtained as products of the degradation of SB-1 and SB-2. Catalysts I and II showed high activity in the degradation of SB copolymers to produce the low molecular weight products (Mn = 276 - 335 g·mol-1) and yields ranging from 91% - 95%. The cross-metathesis degradation of copolymers in organic solvents and in citrus oils (mandarin, orange and lemon oils) proceeded with similar efficiency and resulted in the same molecular weight butadiene oligomers. According to GS/MS (EI) analysis, the main products of the degradation of SB-1 copolymer with d-limonene were limonene-terminated oligomers of series Am (m = 1 - 4).

A NEW POLYBUTADIENE

High active catalyst systems for polymerization of butadiene may be obtained by combining MoCl,ORand proper aluminum alkyl.The conversion of 80% of butadiene can be achieved with 5x10-5 mole ofMoCl4OCH17per mole of butadiene at 70℃ in hydrogenated gasoline.The polydispersity of the polymersin the range of 1.5—2.0 is carried out with the temperature of polymerization at 30—70℃.For the purpose ofregulating molecular weight and chain structure of the polymers allyl halides is satisfactory,among othersallyl iodide is the best.With increase of amount of allyl iodide,the molecular wieght of the polymers de-crease,the 1,2-units increase and the regularity of chain structure of the polymers rises.Some of the physicalproperties of the polymers are as follows:the content of 1,2-units,88——97%;limiting viscosity number,1.8——6.2（in 30℃,toluene）;glass temperature,-27——10℃:tensile yield strength,6.5——8.5（kg/cm2）;ultimate tensile strength,12——25（kg/cm2）and elongation at break,1700—2900%.

Synthesis and Characterization of Hydroxyl-terminated Block Fluorinated Copolyether(FPO-PTHF-FPO)

We introduced fluorine into hydroxyl-terminated block copolyether so as to prepare polyurethane adhesive with better performance.Fluorine-containing epoxy compounds(FO)was synthesized by one-step method from 2,2,3,3-tetrafluoro-1-propanol(TFP)and epichlorohydrin(ECH).Then,a novel hydroxyl-terminated block fluorinated copolyether(FPO-PTHF-FPO)was prepared by cationic ring-opening polymerization of fluorinated epoxy compound(FO)with polytetrahydrofuran(PTHF)as the macromolecular initiator and boron trifluoride diethyl ether(BF_(3)·OEt_(2))as the catalyst.The structure and properties of hydroxyl-terminated block fluorinated copolyether were characterized by FTIR,^(1)HNMR,GPC,DSC,TGA,and viscosity-temperature curve analysis.In comparison with polytetrahydrofuran(PTHF),hydroxyl-terminated block fluorinated copolyether(FPO-PTHF-FPO)has lower viscosity and only one lower glass transition temperature(-66.6℃)on DSC curve.In addition,hydroxyl-terminated block fluorinated copolyether(FPO-PTHF-FPO)begins to decompose at 187.2℃and is completely decomposed until 431.6℃,which indicates that it has a good thermal stability.

Blends of Polypropylene and Syndiotactic 1,2-Polybutadiene:Morphology,Crystallization Behaviors and Mechanical Properties

Morphologies,crystallization behavior and mechanical properties of polypropylene（PP）/syndiotactic 1,2-polybutadiene（s-1,2 PB）blends were investigated.Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5μm when the s-1,2 PB content increases from 5%to 20%（mass fraction）in the blends,and the phase structure tends to become co-continuous as s-1,2 PB content further increases.Crystallization temperature（Tc）of PP component in the blends is fluctuated with the variation of s-1,2 PB content in the blends.Compatibilization,to some extent,between the two components is inferred from the examination of both morphology and crystallization behavior.Improvement of impact strength of PP toughened by s-1,2 PB becomes significant only in the case of s-1,2 PB content above 20%（mass fraction）.

Synthesis of multifunctional additives for solid propellants:Structure,properties and mechanism

To simplify the composite propellant formulation and address the current issue of the single-functionality present in existing additives,the multi-cyano,amine-based polybutadiene(AEHTPB-CN)was prepared based on AEHTPB by adopting appropriate synthesis strategies.By replacing 10% of HTPB binder in the propellant formulation,it can effectively enhance the interfacial bond strength between the propellant binder matrix and solid fillers(AP(ammonium perchlorate)and RDX(cyclotrimethylene-trinitramine)),the mechanical properties of the HTPB/AP/RDX/Al propellant were superior to blank control propellant with an improvement of 35.4% in tensile strength,62.0% enhancement in elongation at break,and reduce the propellant burn rate by 10.7% with any energy loss.The function mechanism of AEHTPB-CN was systematically elucidated through experiments and computer simulation techniques.The results show that the tertiary amine group in AEHTPB-CN can react with AP to form ammonium ionic bonds,and the hydroxyl and cyano groups can form hydrogen bonding interactions with AP,which enables AEHTPB-CN to be firmly adsorbed on the AP surface through chemical and physical interactions.For RDX,the interfacial bonding effect of AEHTPB-CN is attributed to their ability to form C-H···N≡C weak hydrogen bonding interaction between the cyano group and RDX methylene group.

可逆交联聚丁二烯网络的技术进展

简介了聚丁二烯的种类、优异性能及重要性,简述了聚丁二烯使用过程中硫化交联制备的含有不可逆交联网络带来的难以回收和资源浪费的问题,设计合成基于可逆交联键的聚丁二烯网络对于发展高弹性、高强度、可回收和其它功能的先进材料具有重要意义。构筑可逆交联聚丁二烯的关键是在聚丁二烯分子链上引入官能基团,再通过官能基团之间的反应或相互作用构筑可逆交联聚丁二烯网络。根据官能基团在聚丁二烯分子链的位置不同,介绍了基于链端官能化聚丁二烯的可逆交联网络、基于链中官能化聚丁二烯的可逆交联网络和基于链端和链中双重官能化聚丁二烯的可逆交联网络这3种聚丁二烯网络的制备方法和性能。最后提出,引入更多的可逆交联键以及功能基团,拓宽其应用领域是未来的重点研发方向。

端丙烯酸酯基聚丁二烯的合成与表征

为了发展新型固化粘合剂,以端羟基聚丁二烯(HTPB)和丙烯酰氯为原料,经过酰化反应制备出端丙烯酸酯基聚丁二烯(ATPB),通过红外光谱、核磁共振氢谱和凝胶渗透色谱对ATPB的结构进行了表征,采用锥板黏度计研究了其黏度,DSC测定了其玻璃化转变温度,考察了ATPB与含能材料的相容性。结果表明,酰化反应后,HTPB的端羟基吸收峰完全消失,出现了丙烯酸酯基团的特征峰,聚丁二烯分子链未发生断裂,获得了目标化合物;ATPB的玻璃化转变温度为-83.61℃,25℃时黏度为10.10Pa·s;ATPB与高氯酸铵(AP)、黑索今(RDX)相容性好,预期在复合推进剂中具有良好的应用前景。

无机填料复合比例对复合薄膜性能的影响

本工作基于导热复合薄膜性能的研究,提供了一种新型导热复合薄膜的制备方法。通过将不同添加量的氮化硼(BN)和二氧化硅(SiO_(2)_(2))加入到聚丁二烯树脂(PB)中,结合涂覆工艺制备了高导热BN/SiO_(2),填充的复合薄膜材料。系统研究了不同添加量BN对BN/SiO_(2),填充的复合薄膜材料的微观形貌、导热性能、介电性能、抗剥性能和热膨胀系数的影响。结果表明:随着BN含量的增大,复合薄膜表面缺陷逐渐增加,介电常数略有下降,介电损耗略有升高,抗剥强度也下降,X-Y-Z轴的热膨胀系数也都逐渐增大。最终,当BN/SiO_(2),添加质量比例为10:30时(BN添加量为10%),BN/SiO_(2),填充的复合薄膜材料的综合性能表现最佳,导热系数为0.75W^(-1)K^(-1),介电常数为3.20,介电损耗因子为3.12*10^(-3),抗剥强度为2.2Nm^(-1),和适宜的热膨胀系数。有望为新型高导热复合薄膜材料的开发提供一种新的实用型思路。

基于硫化工艺优化制备的汽车悬架橡胶衬套性能比较研究

为增强汽车橡胶衬套的粘接性能,在硫化工艺的基础上,以不同天然橡胶和顺丁橡胶配比制备橡胶材料,并研究不同骨架金属表面处理方式对橡胶衬套粘接性能的影响。试验结果表明,当天然橡胶与顺丁橡胶配比为90∶10时最佳。此时,橡胶衬套材料的硬度、拉伸强度和断裂伸长率分别是71 HA、24.8 MPa、525%,且在老化试验后的拉伸强度降低12.1%,具备良好的硬度、拉伸性能和耐老化性能,均达到汽车橡胶衬套材料的标准要求。在汽车橡胶衬套骨架金属镀膜处理后的橡胶衬套粘接效果最佳,最大破坏力为23.42 kN,约为未处理方式的4倍。

用巯基-烯点击法制备1,2-聚丁二烯包覆的白炭黑及其对丁苯橡胶的增强

采用巯基-烯点击法制备出1,2-聚丁二烯包覆的疏水性白炭黑(Silica-PBs)。红外光谱和X射线电子能谱分析表明,Silica-PBs表面被1,2-聚丁二烯所包覆,并且还有多余的乙烯基。将Silica-PBs与丁苯橡胶(SBR)共混制备的硫化胶相比于使用硅烷偶联剂改性制得的硫化胶具有更优异的综合性能。通过橡胶加工分析仪和电子显微镜分析均可以发现,Silica-PBs在SBR中具有更好的分散状态。Silica-PBs可以在填料与橡胶分子链之间形成一条“缓冲带”,为填料在橡胶分子链滑移时提供一定的缓冲作用。动态力学性能测试结果显示,Silica-PBs相比于传统白炭黑提高SBR/Silica-PBs复合材料的动态力学性能8%以上,可以作为一种理想的绿色轮胎用填料。

基于端羟基聚丁二烯液体橡胶制备功能性嵌段聚合物的研究进展

端羟基液体丁二烯橡胶(HTPB)的活性端羟基在适当条件下可制备成大分子引发剂,将具有特定功能的聚合物通过嵌段共聚改性的方法连接在HTPB的两端,形成结构多样、功能丰富的嵌段聚合物。本文综述了近年来利用HTPB制备的嵌段聚合物在火箭推进剂性能改进、刺激响应性聚合物、可拉伸半导体材料和两亲性聚合物等方面的研究进展,并对利用HTPB制备新型嵌段聚合物的未来进行了展望。

低顺式聚丁二烯橡胶门尼黏度标准物质的定值

标准物质的研制一般经过均匀性检验、稳定性检验、定值和不确定度评定等重要环节,而标准物质的定值关系到标准物质标准值是否准确可靠,因此标准物质的定值工作显得尤为重要。低顺式聚丁二烯橡胶门尼黏度标准物质的定值采用8家行业权威实验室联合定值,采用狄克逊(Dixon)法检验组间、组内是否存在可疑值;夏皮罗-威尔克Shapiro-Wilk法(W检验)检验定值数据是否正态分布;柯克伦(Cochran)法检验定值数据是否等精度。通过定值数据的统计分析,在p=0.99的置信概率时,定值数据均处于等精度、正态分布、无可疑值。定值数据的总平均值33.5为低顺式聚丁二烯橡胶门尼黏度标准物质的标准值。

聚丁二烯基柔性聚氨酯丙烯酸酯的合成及性能研究

为了提高紫外光固化材料对柔性电子器件的适用性,以具有独特长碳链结构的端羟基聚丁二烯(HTPB)作为二醇,与2种不同结构的二异氰酸酯(甲苯二异氰酸酯、六亚甲基二异氰酸酯)及丙烯酸羟乙酯合成了6种聚丁二烯基聚氨酯丙烯酸酯(PUA)。探究了HTPB的相对分子质量和二异氰酸酯的类型对PUA力学性能和光聚合动力学的影响。结果表明:由最高相对分子质量的端羟基聚丁二烯与甲苯二异氰酸酯及丙烯酸羟乙酯合成的芳香族聚氨酯丙烯酸酯表现出更高的韧性和拉伸强度。此外,与具有类似结构的商用芳香族高柔韧性聚氨酯丙烯酸酯相比,力学性能、光固化效率、耐高低温性能、疏水性以及表观性能等都更为优异,在柔性电子器件用光固化涂层材料领域具有广阔的应用前景。