微波消解-电感耦合等离子体发射光谱法检测异戊橡胶中钛质量分数

用微波消解-电感耦合等离子体发射光谱法(ICP-OES)检测异戊橡胶(IR)中钛质量分数。结果表明,消解体系为硝酸/硫酸/双氧水(体积比为5/1/1),谱线波长为334.940 nm,ICP-OES仪射频功率为1 300 W、雾化气流量为0.55m L·min~(-1)、进样量为1.5 m L·min~(-1)、等离子气体流量为10 L·min~(-1)时,检测的IR钛质量分数相对标准偏差为1.07%,加标回收率为95%~105%。该检测方法快速、准确、灵敏度高,满足IR中钛质量分数的检测要求。     

NdCl_3·nTBP/MgCl_2-Al(i—Bu)_3体系催化剂制备条件对异戊二烯聚合的影响

用NdCl_3nTBP/Mgcl_2—Al(i-Bu)_2体系催化合成聚异戊二烯,研究了催化剂制备条件对聚合的影响。结果表明,催化剂加少量单体陈化,催化活性明显提高。当I_P/Nd=100时,Nd/I_p=2×10~(-5),转化率可达96％,值化效率为2.3×10~4g胶/gNd,提高陈化浓度可降低催化剂用量,向I_p—Al—Nd三元陈化体系中加第四组份—Al_2(i—Bu)_2Cl_2,则催化活性明显提高,分子量降低。本体系提高陈化温度对聚合产物的微观结构无影响,而使分子量分布变窄。随聚合温度的提高,产物的cia—1,4结构含量降低,分子量分布基本不变。     

热塑性弹性体SIS聚合胶液传热系数的关联

ＳＩＳ中异戊二烯段聚合反应的基本特征，通过反应温度（Ｔ）、单体转化率（Ｘ）、胶液粘度（μ）以及冷却介质流量（Ｕ）等参数，采用不同的方法关联胶液传热系数，为工程设计提供放大依据。     

A new organofunctional methoxysilane bilayer system for promoting adhesion of epoxidized rubber to zinc: Part 1: Optimization of practical adhesion

Practical adhesion of rubber to zinc cords is measured for various zinc silanization treatments. Aminopropyltrimethoxysilane (APS) alone or both APS and mercaptopropyltrimethoxysilane (γ-MPS) were used as coupling agents for zinc and epoxidized natural rubber (ENR). It is shown that special chemical and physical conditions are required to provide strong practical adhesion. With APS alone, best results are obtained when the zinc is silanized with 1% APS in isopropanol–water, cured at 110 °C for 1 h in air and vulcanized with ENR (20% epoxy groups) at 170 °C for 15 min. The adherence is further improved by double silanization with γ-MPS (0.5%) and then APS (1%). In both cases, the concentration of silanes, the cure temperature of the silane layers, the ageing and acidity of the silane solutions are the main parameters which must be thoroughly optimized. In the case of double silanization, the highest practical adhesion seems to be correlated with a true γ-MPS/APS bilayer structure which is achieved for a specific application of the γ-MPS. It is suggested that this layer is bound to zinc through its thiol function, and the APS layer (on the γ-MPS layer) is cross-linked to γ-MPS and ENR through silanol and epoxy groups, respectively. When the silanized zinc surface was vulcanized and the rubber then peeled off the zinc surface, XPS analysis of the bare zinc areas indicates a rupture characteristic of an adhesive failure in the case of silanization by APS alone, and a cohesive failure in the case of the double silanization.     

Molecular orientation and structural development in vulcanized polyisoprene rubbers during uniaxial deformation by in situ synchrotron X-ray diffraction

Molecular orientation and strain-induced crystallization of vulcanized natural rubbers (by sulfur and peroxide) and synthetic polyisoprene rubber (by sulfur) during uniaxial deformation at 0 °C were studied by in situ synchrotron wide-angle X-ray diffraction. The high intensity of synchrotron X-rays and new image analysis methods made it possible to estimate the mass fractions of strain-induced crystals and amorphous chains in both oriented and unoriented states. Most of the polymer chains (∼75%) were found to be in the random coil state even at large strains (>5.0). Only about 5% the amorphous chains were oriented, whereas the rest of the chains (∼20%) were in the crystalline phase. Sulfur vulcanized and peroxide vulcanized natural rubbers did not exhibit notable differences in structure and property relationships. In contrast, synthetic polyisoprene rubber showed a different behavior of deformation-induced structural changes, which can be attributed to the difference in cross-link topology. Our results indicated that strain induces a network of microfibrillar crystals in both natural and synthetic polyisoprene rubbers due to the inhomogeneity of cross-link distribution that is responsible for their elastic properties.     

Polyisoprene-nanostructured carbon composite – A soft alternative for pressure sensor application

Latest related research shows natural polyisoprene-nanostructured carbon composite (PNCC) as a promising piezoresistive material for soft pressure sensors. The main advantages of PNCC over conventional sensors are exceptional sensitivity in pressure range from 0.1 to 10 bar and possibility to be embedded into completely soft (hyper-elastic) structures.In this work we have elaborated a completely soft (hyper-elastic) PNCC pressure sensor prototype, made using functional multi-layer approach, when elementary layers of PNCC with different conductive filler concentration are cured together and form a uniform sensor body with integrated soft (hyper-elastic) electrodes. We proposed also a theoretical model to explain the observed positive piezoresistivity and used it for fitting of our experimental results.The prototype system elaborated could be used for counting interface events between sensor and external environmental factor. The achieved result could be a step towards the artificial skin, capable to sense non-destructive interaction with the external influence.     

Synthesis and characterization of (star polystyrene)-block-(polyisoprene)-block-(star polystyrene) copolymers

A (star polystyrene)-block-(linear polyisoprene)-block-(star polystyrene) copolymer, (S)_nI(S)_n, was prepared. The star polystyrene was produced via anionic polymerization of polystyrene macromonomers each containing an unsaturated double bond (vinyl) at the chain end. This vinyl-terminated polystyrene macromonomer (SSTM) was obtained beforehand via the synthesis of a living polystyrene using alkyllithium and the termination with p-chloromethylstyrene (PCMS). The living site in the core of the star polystyrene enabled the construction of the succeeding polyisoprene block resulting in the living (star polystyrene)-block-(linear polyisoprene) copolymer, (S)_nI. This living diblock copolymer was then coupled with 1,2-dibromoethane (DBE) to form the well-defined (S)_nI(S)_n. Compared to a linear polystyrene-block-polyisoprene-block-polystyrene, SIS, with the same molecular weight, (S)_nI(S)_n had a higher T_g and exhibited a lamellae-forming phase separation in conjunction with many dislocation defects. The thermal stability appeared independent of the molecular structure, and the radius of gyration and viscosity of (S)_nI(S)_n were much smaller than SIS.     

卤素化合物对NdCl_3·nTBP／MgCl_2－Al（i－Bu）_3体系催化异戊二烯聚合的影响

考察了以卤素化合物为第三组分对ＮｄＣｌ３·ｎＴＢＰ／ＭｇＣｌ２－Ａｌ（ｉ－Ｂｕ）３体系催化异戊二烯聚合的影响。结果表明，各种卤素化合物的活性顺序为Ａｌ２（ｉ－Ｂｕ）３Ｃｌ３≈ＣｌＣＨ２—ＣＨ＝ＣＨ２＞Ｓｉ（ＣＨ３）２Ｃｌ２＞ＡｌＥｔ２Ｃｌ＞ＴｉＣｌ４；以Ａｌ２（ｉ－Ｂｕ）３Ｃｌ２或ＣｌＣＨ２－ＣＨ＝ＣＨ２作第三组分，采用Ｉｐ－Ａｌ－Ｎｄ三元陈化，Ｃｌ单加或内添加卤素化合物方式，均可以提高催化活性，聚合转化率在Ｃｌ／Ｎｄ值为１－６的范围内基本保持不变。经ＩＲ和１３Ｃ－ＮＭＲ测定表明，除Ｓｔ（ＣＨ３）２Ｃｌ２外，第三组分对聚合物的微观结构影响不大。     

负载型钛催化剂催化异戊二烯溶液聚合动力学

研究了TiCI4/MgCI2-AI(i-Bu)3催化体系在加氢汽油中催化异戊二烯聚合的动力学行为。考察了影响聚合速率的各种因素,测定了催化剂利用率、活性中心浓度、链增长速率常数及增长链平均寿期等动力学参数。在铝－钛摩尔比为20－50的范围内,聚合速率对单体浓度和主催化剂浓度均呈一级关系,而对烷基铝浓度呈零级关系。     

异戊二烯橡胶的乳化与乳液稳定性研究

通过反相乳化和脱除溶剂制备了异戊二烯(PIP)橡胶乳液,研究了乳化剂、油水比、乳化剪切速度和胶体SiO2对异戊橡胶乳化液稳定性的影响。结果表明:油酸钾与Span80复配、油水相重量比为1∶1时,经高速剪切均化后得到相对稳定的PIP乳液。而胶体二氧化硅在PIP乳胶粒表面达到吸附饱和,可进一步提高PIP乳液的稳定性。