Morphological and mechanical study of nanostructured epoxy systems modified with amphiphilic poly(ethylene oxide-b-propylene oxide-b-ethylene oxide)triblock copolymer

Thermosetting systems based on DGEBA epoxy resin and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer were prepared and investigated. Different mixtures were obtained by using different contents of EPE block copolymer in order to study the influence of the modifier on the properties of the final materials. All thermosetting systems were prepared without using any solvent and were cured at ambient temperature, taking into account the lower critical solution temperature (LCST) behavior of the block copolymer. DSC results indicated that the addition of block copolymer affected to the curing reaction time and to the glass transition temperature of the mixtures and also the miscibility of EPE triblock copolymer in the epoxy resin was proved. The morphologies studied by AFM and TEM showed clear nanostructuration up to 25 wt % EPE content. The addition of 5 and 15 wt % of EPE block copolymer led to a considerable improvement in the toughness of the materials. When EPE block copolymer was added to the epoxy resin, the surface became more hydrophilic and the UV–vis transmittance decreased slightly maintaining a high level of transparency.     

Nano-phase structures and mechanical properties of epoxy/acryl triblock copolymer alloys

Phase structures and mechanical properties of epoxy/acryl triblock copolymer alloys using several curing agents were studied. PMMA-b-PnBA-b-PMMA triblock copolymers synthesized by living anionic polymerization were applied as the toughening modifiers for the epoxy resins. An aromatic amine, an acid anhydride and an anionic polymerization catalyst as curing agents resulted in macro-phase separation in the epoxy/triblock copolymer blends during the cure process. However, a phenol novolac as the curing agent created nano-phase structures in the epoxy blends. The size of the spherical phases or cylindrical phases was about 40 nm in diameter, and the main component in the nano-phases was the PnBA of the triblock copolymer. The fracture toughness of the epoxy/triblock copolymer alloys with the nano-cylindrical phases reached 2530 J/m². The fracture toughness was more than twenty fold relative to the unmodified epoxy resin, and was equivalent to the toughness of polycarbonates.     

Effect of crosslink density on fracture behavior of model epoxies containing block copolymer nanoparticles

Model diglycidyl ether of bisphenol-A based epoxy resins containing well-dispersed 15 nm block copolymer (BCP) nanoparticles were prepared to study the effect of matrix crosslink density on their fracture behavior. The crosslink density of the model epoxies was varied via the controlled epoxy thermoset technology and estimated experimentally. As expected, it was found that the fracture toughness of the BCP-toughened epoxy is strongly influenced by the crosslink density of the epoxy matrix, with higher toughenability for lower crosslink density epoxies. Key operative toughening mechanisms of the above model BCP-toughened epoxies were found to be nanoparticle cavitation-induced matrix shear banding for the low crosslink density epoxies. The toughening effect from BCP nanoparticles was also compared with core-shell rubber-toughened epoxies having different levels of crosslink density. The usefulness of the present findings for designing toughened thermosetting materials with desirable properties is discussed.     

Erosion resistance and toughening mechanism of AlBO and BNw whiskers modified thermal barrier coatings

In order to improve the erosion resistance and toughness of thermal barrier coatings, YSZ coatings, 20 vol%-AlBOw whisker modified YSZ coatings and 20 vol%-BNw whisker modified YSZ coatings were prepared by plasma spraying. The cross-section structure, morphology, composition and phase composition of coatings and powders were analyzed by SEM, EDS and XRD. The erosion resistance of three coatings was tested by self-made erosion tester. The crack growth resistance of coatings was tested and calculated by Vickers hardness tester. The results show that the density of the coating is improved by adding AlBOw and BNw. The whisker inhibits the crack propagation through the mechanisms of crack deflection, whisker pull-out and whisker bridging. The addition of whisker improves the erosion resistance of YSZ coating by 8.17% and 13.94%, which can effectively improve the service life of thermal barrier coating.     

纳米碳酸钙改性苯乙烯-丁二烯-苯乙烯嵌段共聚物的力学性能

在高速剪切乳化釜中用纳米碳酸钙填充改性苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS),考察了混合时间、混合温度及纳米碳酸钙的用量对改性SBS力学性能的影响,并研究了由改性SBS制备的热塑性橡胶(TPR)鞋用料的性能。结果表明,纳米碳酸钙与SBS的最佳混合温度为50℃,混合时间为60min,纳米碳酸钙质量分数为5%;由纳米碳酸钙改性SBS生产的TPR鞋用粒料的耐磨性和加工性能得到改善。     

Crystallization and coalescence of block copolymer micelles in semicrystalline block copolymer/amorphous homopolymer blends

Crystallization of two oxyethylene/oxybutylene block copolymers (E₇₆B₃₈ and E₁₅₅B₇₆) from micelles in block copolymer/amorphous homopolymer blends was studied by differential scanning calorimetry (DSC) and time-resolved small angle X-ray scattering (SAXS). Unlike the simultaneous crystallization and formation of superstructure in crystallization from an ordered structure, crystallization of block copolymer from micelles can be divided into two steps. The core of the micelles firstly crystallizes individually, with first-order crystallization kinetics and homogeneous nucleation mechanism. The SAXS revealed that crystallization-induced deformation occurs for the micelles, which strongly depends on microstructure of the block copolymers. For the shorter block copolymer E₇₆B₃₈, larger deformation induced by crystallization was observed, leading to coalescence of the micelles after crystallization, while for the longer block copolymer E₁₅₅B₇₆ the micelles show little deformation and the morphology of micelle is retained after crystallization.     

Effect of composition of added random copolymer on the phase behavior of block copolymer

Blends of styrene-butadiene diblock copolymer (S-B, 52 wt% styrene content) and styrene-butadiene random copolymer (SBR) of various styrene compositions were studied by small-angle X-ray scattering, light scattering, and transmission electron microscopy. The composition of random copolymer plays an important role in the solubilization of SBR in S-B. The order-disorder transition temperature, T_ODT, decreases linearly with the addition of SBR. T_ODT decreases as the symmetry in SBR composition increases and shows the highest value in the case of homopolymers. Asymmetric butadiene-rich SBR dissolves mostly into PB microdomain of S-B to increase lamella microdomain spacing, D, and its addition makes the overall microdomains of S and B in the mixture more asymmetrical. Symmetric SBR is localized into the interface of S-B microdomain to reduce unfavorable S-B contact at the interface. The phase diagram for S-B containing asymmetric SBR shows a succession of mixed mesophases of different morphologies from lamellae and cylinder to disordered liquid phases, whereas the phase diagram containing symmetric SBR shows two homogeneous phases and one region of two-phase coexistence, where macroscopically separated phases coexist together.     

Novel isocyanate-free self-curable cathodically depositable epoxy coatings: Influence of epoxy groups on coating properties

Novel self-curable cathodically depositable coatings were developed from glycidyl functional epoxy ester-acrylic graft co-polymer (EEAG) without using any external crosslinking agents. The EEAG-amine adducts (EEAGAs) were prepared by reacting EEAG with varying amount of diethanolamine (DEoA) which are neutralized with acid and dispersed in deionised water to give stable dispersion for cathodic electrodeposition (CED) coatings. The dispersions were cathodically electrodeposited on phosphated steel panels and thermally cured to give uniform coating. The coatings were evaluated for different mechanical, chemical and corrosion resistance properties. The coatings were evaluated for their thermal properties using thermo gravimetric analysis (TGA). The final properties of the coatings were found to be affected by the amount of amine reacted with epoxy. The coating films showed good overall performance properties for their use in coating industry.     

Two-dimensional block copolymer photonic crystals

A high molecular weight polystyrene-block-polyisoprene copolymer was synthesized by anionic polymerization of styrene and isoprene monomers. Polystyrene cylindrical domains in a hexagonal lattice with relatively large periodicity and controlled orientation have been produced through roll casting of the polystyrene-block-polyisoprene copolymer with a total molecular weight of 1.0×10⁶ g/mol. The large periodicity and effective processing lead to reflectivity of about 70% in the visible regime, and generate a two-dimensional photonic crystal with a partial band gap.     

Metallo-supramolecular complexes mediated thermoplastic elastomeric block copolymer

Orthogonal multi-phase strategy has been applied to generate a novel type of thermoplastic elastomeric block copolymer which was obtained via anionic polymerization. Functional terpyridine groups which can potentially form metallo-supramolecular complexes with a variety of metal ions has been introduced to the polystyrene-b-polyisoprene (PS-PI) living chain ends through the termination reaction in an optimized condition. Iron(II), cobalt(II) and zinc(II) metal ions have been used to form metal-ligand complexes with the terpyridine end groups, which can phase separate from the polymer matrix to form hybrid clusters. The formation of metallo-supramolecular hybrid clusters have dramatic effects on the micro-phase separated structures of the PS-PI diblock copolymer, which have been characterized by transmission electron microscopy, small-angle X-ray scattering and atomic force microscopy. This type of hybrid material containing hard PS nanophase and metal-ligand clusters exhibit distinct mechanic properties such as increased modulus, higher yield strength and improved toughness, which is further discussed in light of nature of the metal-ligand bonds and the liability of the clusters. The utilization of metallo-supramolecular complex and its high tunability is potential to fabricate new types of supramolecular nanocomposite materials.     

Influence of block lengths and symmetries of block copolymers on phase behavior of polymer A/polymer B/block copolymer ternary blends

Monte Carlo simulations were used to investigate the compatibilizing effects of diblock copolymers in A/B/A-B diblock copolymer ternary blends and triblock copolymers in A/B/triblock copolymer ternary blends, respectively. The volume fraction of homopolymer A was 19% and was the dispersed phase. The simulation results show that diblock copolymers with longer A-blocks are more efficient as compatibilizers, and symmetric triblock copolymers with a shorter middle block length are easily able to bridge each other through the association of the end blocks. This kind of triblock copolymers have relatively high ability to retard phase separation as compatibilizers.     

Toughening of carbon fiber/epoxy composite by inserting polysulfone film to form morphology spectrum

Fracture toughness of the polysulfone(PSf) film modified epoxy composite having a morphology spectrum was investigated. The epoxy resin was based on diglycidyl ether of bisphenol-A (DGEBA type) and diaminodiphenylsulfone (DDS). 1K carbon fabric was used as reinforceing material. The morphology spectrum which has gradual change of the morphological feature resulting from the concentration gradient of PSf in the composite can be obtained by inserting the PSf film in carbon fiber reinforced epoxy prepreg before cure. The relative rate of the dissolution and diffusion of the PSf in the epoxy determine the concentration gradient of the PSf. As the concentration of the PSf increases, the morphology changes from sea-island to nodular structure. The fracture toughness of the composite with 20 wt% PSf film was 2.7 times higher than that of the unmodified composite. This result was ascribed to the plastic deformation of the continuous PSf rich phase in the semi-IPN having morphology spectrum.     

聚氨酯改性环氧富锌防腐涂料的制备

通过正交实验法,以涂膜的吸水率为依据,确定了制备聚氨酯改性环氧共聚物时,聚氨酯的最佳用量,适当的反应时间和反应温度,固化剂的最佳添加量;并通过浸泡腐蚀失重法,确定了锌粉的最佳含量。对涂膜进行了红外光谱、极化曲线和扫描电镜分析,对比检测了未改性环氧富锌防腐涂料、聚氨酯改性环氧富锌防腐涂料的各方面性能。结果表明,聚氨酯改性环氧富锌防腐涂料具有较高的机械强度、低吸水率、良好的附着力和耐化学腐蚀性能。     

氟硅改性无溶剂环氧涂料的制备与性能

采用甲基丙烯酸十三氟辛酯（TFM）改性氨基硅油（AS）制备氟化氨基硅油（FAS）,并用其改性环氧树脂（EP）探究氨基硅油及氟化氨基硅油添加量对环氧涂层性能的影响。本文通过红外光谱对改性结果进行表征,通过柔韧性测试、画圈附着力测试、铅笔硬度测试、耐冲击测试、热失重测试、接触角测试、紫外加速老化实验和Tafel极化曲线测试,分别评价涂层的柔韧性、附着力、硬度、耐冲击性、耐热性、疏水性、耐候性和防腐性能,通过扫描电镜对涂层断面进行分析,并通过EDS对涂层进行表面元素分析。结果表明,氟添加量为15%制备氟化氨基硅油改性环氧树脂时,氟硅改性EP涂层相对于未改性EP涂层,硬度由2H提升至3H,附着力由2级提升至1级,柔韧性由1mm提升至0.5mm,耐冲击由45cm提升至50cm,热稳定性增强,接触角由70.5°提升至123°,耐紫外老化（432h）由3级提升至1级,E_corr由-0.6187V正移至-0.1720V,I_corr由1.9858×10^-8A/cm²减小至3.7125×10^-10A/cm²。适量氟化氨基硅油的引入,显著提升了环氧涂层的机械性能、耐候性能和防腐性能。     

Fracture behaviours of in situ silica nanoparticle-filled epoxy at different temperatures

Fracture behaviours of nanosilica filled bisphenol-F epoxy resin were systematically investigated at ambient and higher temperatures (23 °C and 80 °C). Formed by a special sol-gel technique, the silica nanoparticles dispersed almost homogenously in the epoxy resin up to 15 vol.%. Stiffness, strength and toughness of epoxy are improved simultaneously. Moreover, enhancement on fracture toughness was much remarkable than that of stiffness. The fracture surfaces taken from different test conditions were observed for exploring the fracture mechanisms. A strong particle-matrix adhesion was found by fractography analysis. The radius of the local plastic deformation zone calculated by Irwin model was relative to the increment in fracture energy at both test temperatures. This result suggested that the local plastic deformation likely played a key role in toughening of epoxy.     

Theoretical study on morphology of ABCD 4-miktoarm star block copolymer

A real-space implementation of the self-consistent field theory (SCFT) has been used to study the morphologies of ABCD 4-miktoarm star block copolymers. For the sake of numerical tractability, the morphologies and the phase diagrams of ABCD 4-miktoarm star block copolymers are investigated in two dimensions (2D) by varying the volume fractions of the blocks and the interaction parameters. Many interesting and complex morphologies occur and compared with ABCD linear block copolymers; ABCD 4-miktoarm star block copolymers have more regular disciplines. We found that systems with similar components have similar morphologies and at the weaker segregation, the minority components always cannot separate from the other blocks and they easily dissolve to form one phase with other block(s), but with the increase of the segregation degree (large ), the ordered phases can be well separated. With the help of our computational prediction, experimental researchers can work more purposefully and efficiently.     

Study on nano-CaCO3 modified epoxy powder coatings

Powder coatings are widely used for their environmental and economical advantages. In this work nano-CaCO₃ modified powder coatings were prepared using epoxy resin/nano-CaCO₃ composites obtained through in situ and inclusion polymerization and the nano-CaCO₃ can be well dispersed in the resultant coatings by this preparation method. Their tensile property, cupping property and neutral salt spray corrosion resistance were distinctly improved. The mechanism of property improvement was discussed.     

Non-reactive and reactive block copolymers for toughening of UV-cured epoxy coating

Reactive and non-reactive diblock copolymers based on polyethylene oxide (PEO) and a poly(glycidyl methacrylate) (PGMA, reactive) or polystyrene (non-reactive) block, respectively, are prepared via ATRP and those are incorporated into a cycloaliphatic epoxy matrix. Crosslinking of the matrix is then performed by cationic UV curing, producing modified thermosets. ¹H NMR and SEC measurements are carried out and used to analyze the composition, the molar mass and dispersity of the prepared block copolymers. The viscoelastic properties and morphology of the modified epoxy are determined using DMTA and FESEM, respectively. The addition of 4 and 8 wt% of the reactive PEO-b-PGMA block copolymer into epoxy resin has only minor effects on the glass transition temperature, T_g. The reactive homopolymer PGMA significantly increases and the non-reactive block copolymer PEO-b-PS slightly decreases the glass transition temperature of the epoxy matrix. The non-reactive block copolymer PEO-b-PS causes a little decrease in T_g values. The measurement of the critical stress factor, K_IC, shows that the fracture toughness of the composite materials is enhanced by inclusion of the non-reactive block copolymer. In contrary, the reactive block copolymer has negative effect on the fracture toughness especially in case of short PEO block. FESEM micrographs studies on the fracture surfaces sustain the microphase separation and the increase in surface roughness in the toughened samples, indicating more energy was dissipated.     

Design and stabilization of block copolymer micelles via phenol-pyridine hydrogen-bonding interactions

A new approach for the preparation of block copolymer micelles in non-selective solvent is introduced. Phenol-pyridine hydrogen-bonding interactions are used for the first time to prepare core-shell micelles in non-selective solvents using block copolymers and bifunctional low-molecular-weight hydrogen-bonding crosslinkers. Poly(styrene-b-4-vinylphenol)/Bis-pyridyl ethane and poly(styrene-b-4-vinylpyridine)/Bisphenol A were investigated as micelle formation due to phenol-pyridine hydrogen bond crosslinking. The influence of several factors such as temperature, concentration, solvent and pH in micellization-demicellization process was analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and atomic force microscopy (AFM). This method opens new possibilities to the generation of block copolymer micelles in non-selective solvents.     

Time-resolved GISAXS and cryo-microscopy characterization of block copolymer membrane formation

Time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) and cryo-microscopy were used for the first time to understand the pore evolution by copolymer assembly, leading to the formation of isoporous membranes with exceptional porosity and regularity. The formation of copolymer micelle strings in solution (in DMF/DOX/THF and DMF/DOX) was confirmed by cryo field emission scanning electron microscopy (cryo-FESEM) with a distance of 72 nm between centers of micelles placed in different strings. SAXS measurement of block copolymer solutions in DMF/DOX indicated hexagonal assembly with micelle-to-micelle distance of 84–87 nm for 14–20 wt% copolymer solutions. GISAXS in-plane peaks were detected, revealing order close to hexagonal. The d-spacing corresponding to the first peak in this case was 100–130 nm (lattice constant 115–150 nm) for 17 wt% copolymer solutions evaporating up to 100 s. Time-resolved cryo-FESEM showed the formation of incipient pores on the film surface after 4 s copolymer solution casting with distances between void centers of 125 nm.