阴极电泳涂料的进展

电泳涂料的合成及其应用是涂料行业中的一个突破性进展。目前几乎所有的汽车工业用底漆及其它行业用的防腐底漆都采用电泳涂料,而其中的百分之九十以上是阴极电泳涂料。本文将详细论述阴极电泳涂料所用树脂的种类及其性能。     

Compatibilising action of random and triblock copolymers of poly(styrene-butadiene) in polystyrene/polybutadiene blends: A study by electron microscopy, solid state NMR spectroscopy and mechanical measurements

Scanning electron microscopy, solid-state proton NMR spectroscopy and static mechanical analysis have been performed in order to evaluate the compatibilising action of random copolymers of polystyrene and polybutadiene and triblock copolymers of poly(styrene-butadiene-styrene) in incompatible polystyrene/polybutadiene (PS/PB) blends. Scanning electron microscopic examination of the cryofractured and etched surfaces showed high degree of compatibilising action of the triblock copolymers as evidenced by the very sharp decrease of the domain size of the dispersed phase followed by an increase at higher concentrations. This is a clear indication of interfacial saturation. These results were in agreement with the theoretical predictions of Noolandi and Hong. The random copolymer was not effective in compatibilising the system. Solid-state proton NMR experiments were performed on the uncompatibilised and compatibilised blends. The proton spin-lattice relaxation times in the laboratory frame, T₁(H), and in the rotating frame, T_1ρ(H), and spin-spin relaxation times, T₂(H), were carefully measured for the systems. Significant changes were observed for the systems compatibilised with triblock copolymers due to the preferential localisation of the copolymers at the PS/PB interface. However, the random copolymer did not have any compositional drift and is not an effective interface modifier in agreement with microscopy study. The static mechanical properties of the blends have also been analysed. The addition of triblock copolymers increased the mechanical properties of the blends. Finally, attempts have been made to correlate the NMR results with the microstructure and mechanical properties of the blends.     

单官能度端伯,仲羟基聚丁二烯的研制

本文较详细地研究以ｎ－ＢｕＬｉ为引发剂，丁二烯为单体，抽余油为溶剂，四氢呋喃为１，２－结构调节剂，环氧乙烷和环氧丙烷为羟基化试剂，单官能度端伯、仲羟基聚丁二烯的合成。实验表明，丁羟胶的分子量为２０００～８０００可调；１，２－结构含量可控制在２５％以下，也可随意提高至４０％以上；分子量分布＜１．１，平均官能度接近１。此外，对所得样品采用ＶＰＯ、ＧＰＣ、ＩＲ、Ｈ’－ＮＭＲ等仪器和化学方法进行表征。     

Experimental cloud points for polybutadiene + light solvent and polyethylene + light solvent systems at high pressure

The hydrogenation of unsaturated heavy compounds is conventionally carried out in the presence of two fluid phases, because the immiscibility in the binary subsystem ‘hydrogen + heavy substrate’ cannot be overcome by adding a standard solvent. Using a supercritical or quasicritical solvent allows the hydrogen and the unsaturated heavy substrate to dissolve into a single phase. To select the operating conditions of a supercritical reactor, it is necessary to determine the phase boundaries of the subsystems ‘solvent + hydrogen’ and ‘solvent + heavy compound’. In this work, we measured cloud points for binary systems made of polybutadiene (PB) or polyethylene (PE) and a light solvent, i.e., propane or dimethyl ether (DME) or diethyl ether (DEE). The temperature range studied was from 50 to 160 °C for ‘PB + DME’ and ‘PB + Propane’ and from 100 to 190 °C for ‘PB + DEE’ and ‘PE + DEE’. We found that in PB-containing binary systems, at the ranges of conditions of the experiments, the minimum pressure required to guarantee homogeneity, at any temperature, is below 200 bar for DEE, below 300 bar for DME and in the order of 500 bar when using propane as solvent. Our data for ‘PE + DEE’ indicate the need for a minimum pressure of about 240 bar to keep the system within a single phase. The results from this work and from the literature suggest that the use of binary solvent mixtures may be convenient to carry out the supercritical hydrogenation of PB.     

Ni(naph)_2-Al(i-Bu)_3-BF_3·OEt_2-ROH体系催化丁二烯聚合的动力学研究

本文探讨了ROH增溶BF_3·OE_2的机理,研究了Ni(naph)_2—Al(i-Bu)_3-BF_3·OEt_2-ROH催化丁二烯聚合反应的动力学行为,考察了温度、催化剂浓度对聚合反应的影响:并且确立了聚合反应的动力学方程为: -d[Bd]/dt =kp·[C~*]·[Bd]=kpf[Ni]_0[Bd]并求得聚合反应的表观活化能Ea=20.6kcal/mol等其它动力学参数。     

Analysis of deuterium NMR spectra of probe chains diffusing in a stretched polybutadiene network

Polybutadiene network was swollen with short perdeuterated network-like chains (PBD). Deuterium NMR spectra of these probe chains are measured as the rubber matrix is uniaxially elongated. Due to the presence of two kinds of deuterons (methylene and ethylene) and two possible configurations of monomer units (cis and trans) in PBD chains, composite NMR spectra are observed and analysed. They evidence for different orientational behaviour of cis and trans units. ‘Rod-like’ motional behaviour of the trans units leads to higher degree of orientational order than for the cis units.     

Effect of film thickness on auto-oxidation in cobalt-catalyzed 1,4-polybutadiene films

Oxygen mass uptake was measured in 1,4-polybutadiene (PB) films undergoing cobalt-catalyzed oxidation in air. Films thicker than approximately 50 μm showed an increase in oxygen uptake per unit polymer mass as film thickness increased, while oxygen uptake per unit film area remained independent of thickness, suggesting that oxidation was heterogeneous and proceeded essentially as an oxidized front penetrating into the film from the surfaces exposed to oxygen. In contrast, oxidation in films thinner than about 28 μm proceeds homogeneously, with oxygen uptake per unit mass being essentially independent of thickness. In oxidized samples, oxygen and nitrogen permeability decreased by more than two orders of magnitude relative to permeability values in unoxidized samples. In thicker films, a two-phase model, based upon high levels of oxidation in a thin skin at the surface of PB and relatively low levels of oxidation in the core of the films, was used to describe gas permeability data and estimate the oxygen and nitrogen permeability in fully oxidized PB.     

Mechanical properties of polybutadiene reinforced with octadecylamine modified graphene oxide

Octadecylamine-modified graphene-oxide (OMGO) polybutadiene nanocomposites with different OMGO loadings were prepared by solution mixing. The dispersion of OMGO in chloroform is greatly improved compared to GO. Toughness and elongation of PBD–OMGO nanocomposites increase by 332% and 191% respectively compared with pure PBD. However, Young's modulus of PBD–OMGO nanocomposite decreases by 10% at 2-wt% loading. Graphene sheet crumpling accounts for the increased toughness, the absence of modulus reinforcement and the absence of a Payne effect for PBD–OMGO. The oxidation susceptibility of PBD is greatly reduced after the addition of OMGO, which is particularly desirable in the tire industry.     

The melting process and the rigid amorphous fraction of cis-1,4-polybutadiene

A thorough analysis of the melting behavior of cis-1,4-polybutadiene (cis-PBD) is detailed in this contribution. Isothermal crystallization at −26 °C, followed by cooling, provides a three-phase structure composed of a mobile amorphous fraction equal to 0.41₃, a crystallinity of 0.27₇, and a rigid amorphous fraction of 0.31₀. Similar to many other polymers, cis-PBD displays multiple melting after isothermal crystallization, and up to three main endotherms can be evidenced by calorimetry, in dependence of the scanning rate. The results of conventional and temperature-modulated calorimetry analyses presented in this contribution suggest a link between multiple melting and devitrification of the rigid amorphous fraction in cis-PBD. The small endotherm located a few degrees above the crystallization temperature appears to be caused by concurrent partial mobilization of both the crystal and the rigid amorphous portions. Additional partial mobilization of rigid amorphous segments seems to take place at around −11 °C, and it is only above this temperature that large reorganization of the crystal phase becomes possible, allowing partial melting and recrystallization/annealing/crystal perfection.     

铁体系催化丁二烯聚合动力学研究——(Ⅱ)聚合度与链转移

本文研究了 Fe(naph)_2-Al(i-Bu)_3—氯化物体系催化丁二烯聚合时的链转移反应。得出只向单体和氯化物链转移的结论,并导出了此体系所特有的聚合度表达式。估算出向单体转移的活化能较低,为41.4KJ/Mol(AlEt_2Cl),12.5KJ/Mol(C_3H_5Cl)。用所得活性链平均寿命τ值的变化,解释了链转移值随温度的升高而加剧。