UV固化粉末涂料的研究与应用

综述了UV光固化粉末涂料与技术以及主体树脂的研究与发展概况,介绍了UV光固化粉末涂料的特性及应用领域。     

Elastic properties of adhesive polymers. II. Polymer films and bond lines by means of nanoindentation

Seven different polymers used frequently as adhesives and/or matrix polymers in wood, wood composites, and natural fiber‐reinforced composites were studied by uniaxial tensile tests and nanoindentation. It was shown that the elastic modulus, the hardness, the creep factor, and the elastic‐, plastic‐, and viscoelastic work of indentation of the seven different polymers is essentially the same regardless whether the polymers were tested in the form of pure films or in situ, i.e., in an adhesive bond line with spruce wood. An excellent correlation was found between the elastic modulus measured by tensile tests and the elastic modulus measured by nanoindentation. In spite of the good correlation, the elastic modulus measured by nanoindentation is significantly higher than the elastic modulus measured by tensile tests. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1234–1239, 2006     

Crosslinked acrylic pressure sensitive adhesives. 3. Effect of adherend on film formation

The reaction of isocyanate in pressure sensitive adhesive (PSA) films adhered on to various adherends having different surface tensions was monitored by depth profiling using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy.In the latter stages of crosslinking reaction, unreacted isocyanate and its derivatives exist more in the bulk of the PSA than in the interfaces between PSA and adherends which are Teflon sheet and PE film having relatively lower surface tensions. In the case of using stainless steel having relatively higher surface tension as adherend, opposite segregation was observed compared to Teflon and PE.From X-ray photoelectron spectroscopy (XPS), it was revealed that N atoms exist more in surface than in bulk when stainless steel is used as adherend. We conclude that polyisocyanates migrate in the PSA film in order to minimize the magnitude of interfacial free energy between the PSA and the adherend, which leads to the change of surface tension of PSA film.     

Reactive Hot Melts on the Basis of Polyester and Polyamide

Hot melts show many advantages over other adhesives, for instance, their lack of solvent and their very short setting time just by cooling. The weak point of hot melts in comparison to thermosetting resins is their limited thermal resistance. There is no doubt that the high performance hot melts on the basis of polyester and polyamide show a better heat performance than the widely-used rubbery hot melts. Nevertheless, it is true that the thermal resistance is limited by the melting point of the hot melt. To improve the heat performance, without losing the favourable hot melt properties, crosslinkable hot melts have been created. For the example, copolyamide/blocked isocyanate blends, it can be shown that crosslinkable hot melts are achievable in a wide range of reactivities. After curing, which takes place during the bonding process, these hot melts withstand temperatures of over 220°C even if the melting point of the initial hot melt was 100°C.     

The Effect of Temperature on the Strength of Adhesively-Bonded Composite-Aluminium Joints

Different materials have different coefficients of thermal expansion, which is a measure of the change in length for a given change in temperature. When different materials are combined structurally, as in a bonded joint, a temperature change leads to stresses being set up. These stresses are present even in an unloaded joint which has been cured at say 150°C and cooled to room temperature. Further stresses result from operations at even lower temperatures.

In addition to temperature-induced stresses, account also has to be taken of changes in adhesive properties. Low temperatures cause the adhesive to become more brittle (reduced strain to failure), while high temperatures cause the adhesive to become more ductile, but make it less strong and more liable to creep.

Theoretical predictions are made of the strength of a series of aluminium/CFRP joints using three different adhesives at 20°C and 55°C. Various failure criteria are used to show good correlation with experimental results.     

Enhanced interfacial adhesion of aramid fiber reinforced rubber composites through bio-inspired surface modification and aramid nanofiber coating

In order to improve the interfacial adhesion between aramid fiber (AF) and rubber matrix, a simple and facile method of aramid nanofiber (ANF) coating is demonstrated in this article. Tannic acid (TA) and polyethyleneimine (PEI) are polymerized in an alkaline solution to form a thin TA/PEI (TP) layer that is deposited on the surface of AF to introduce functional groups such as hydroxyl and amino groups. Then, the ANF coating is utilized to construct nanostructures on the surface of AF to improve the interfacial adhesion between the fiber and the rubber. Through hydrogen bonding and/or π-π stacking between the TP layer and the ANF, the ANF coating is firmly attached to the surface of AF. Compared with the untreated fiber, the interfacial adhesion of AF coated with ANF after 1, 3, 5, 7, 9 deposition cycles is increased by 27.8%, 29.1%, 31.5%, 43.1%, and 30.3%, and the mechanical properties of the fibers remain almost unchanged. This method shows its advantages of simple, facile, and time-effective, which is of great significance for industrial applications.     

Catechol-containing waterborne polyurethane adhesive inspired by mussel proteins

A series of waterborne polyurethane (PDMAPU) containing catechol group were prepared by double-bond random copolymerization of terminated double bond polyurethane prepolymer with modified acrylamido dopamine under thermal initiation. This kind of mussel-like waterborne polyurethane adhesive is inspired by marine mussel, as well as it is environment-friendly and used in bonding of leather. FTIR and ¹H NMR proved the successful introduction of catechol group into polyurethane matrix. Oxidative cross-linking between catechol unit and molecular chain in PDMAPU structure, the thermal stability and crystallization ability of PDMAPU was significantly improved. The increase of the particle size of PDMAPU emulsion showed that the introduction of catechol group changed the microstructure of polyurethane and enhanced the cross-linking degree. The water resistance of polyurethane emulsion was further improved. Compared with PU without catechol group, the peel strength of leather substrate adhered by PDMAPU emulsion increased from 0.42 to 1.93 MPa, which indicated that PDMAPU has better bonding properties with leather. The bidentate hydrogen bond formed with catechol group as the reaction sites is considered to be the key reason for the adhesion of mussel-like polyurethane adhesive to hydrophilic substrates. This work provides an alternative to prepare environment-friendly high performance adhesive for hydrophilic substrates.     

Effects of polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), or rock asphalt on the performance of desulfurized rubber modified asphalt

To improve the performance of desulfurized rubber modified asphalt (DRMA), especially its high-temperature performance, three modifiers (including polyphosphoric acid [PPA], styrene-butadiene-styrene [SBS], and rock asphalt) were selected to modify DRMA respectively. The conventional performance, rheological properties, chemical composition, and thermal decomposition were characterized to analyze the performance and modification mechanism of DRMA and its composites. Test results show that, the addition of PPA, SBS, and rock asphalt can all improve the high temperature of DRMA, among which the desulfurized rubber/rock asphalt compound modified asphalt (DRMA-ROCK) has the best high-temperature performance; however, its construction workability, storage stability, and low-temperature performance are poor. In contrast, desulfurized rubber/PPA compound modified asphalt (DRMA-PPA) not only has better high-temperature performance, but also has excellent low-temperature performance, storage stability, and fatigue performance. Fourier infrared spectroscopy (FTIR) test confirms that the modification process of DRMA by these modifiers is chemical modification, and the characteristic peak indexes obtained from FTIR also prove that DRMA-ROCK has better high-temperature performance but poor construction workability from the microscopic point of view. Furthermore, thermogravimetric analysis-differential scanning calorimetry test shows that the addition of rock asphalt improves the thermal stability of DRMA, while PPA and SBS decrease its thermal stability. From the above results, it can be concluded that DRMA-PPA has excellent comprehensive properties.     

Rapid preparation of hierarchically porous ceramic microspheres based on UV-curing-assisted molding

Ceramic microspheres have attracted significant attention, while the preparation of hierarchically porous ceramic microspheres with high porosity, good sphericity, and controllable size or shape in a short time remains a challenge. Herein, we developed a highly adaptable methodology for the preparation hierarchically porous ceramic microspheres with high porosity and favorable shape in a short time. The UV-curing assisted molding method combined with the Pickering emulsion method was utilized to prepare hierarchically porous ceramic microspheres. Under the irradiation of a UV-curing lamp (395 nm, 50 W), the Pickering emulsion can be cured within as short as 10 s. The microstructures of the three microspheres with different shapes were characterized by scanning electron microscopes (SEM). The as-prepared microspheres had a high sphericity, the interconnectivity of pores was as high as 54 %, and its porosity was as high as 73.4 % ± 3.0 %, while the density was quite low at ∼ 1.02 g/cm³.     

Deformation and Fracture of Micron‐Sized Metal‐Coated Polymer Spheres: An In Situ Study

In situ imaging and analysis of the mechanical behavior of micron‐sized metal‐coated polymer particles under compression is reported. A nanoindentation set‐up mounted in a scanning electron microscope is used to observe the deformation and fracture of 10 μm polymer spheres with Ni, Ni/Au, Au, and Ag coatings. The spheres fracture in one of two metallization‐dependent modes, brittle, and ductile, depending only on the presence of a nickel layer. The metal coating always fractures parallel to the direction of compression. The mechanical properties up to the point of coating fracture are rate‐dependent due to the viscoelastic polymer core. Metal‐coated polymer spheres are an important composite material in electronics packaging, and this study demonstrates a novel method of evaluating the mechanical properties of particles to tailor them for electronic materials.