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.     

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.

     

接枝氯丁橡胶胶粘剂研究概况

介绍了氯丁橡胶 (CR)二元及多元接枝改性胶粘剂研究进展 ,并对其性能用途及合成工艺作了概述     

可水分散多异氰酸酯技术进展

可水分散多异氰酸酯作为双组分水基胶粘剂和涂料交联剂,具有使用时不会生成甲醛等有害物质的优点。简介制备方法,着重介绍国内外技术进展以及在织物整理、木材加工等方面的用途。     

Improving the properties of water-borne pressure sensitive adhesives by using non-migratory surfactants

The adhesive performance of high solids content water-borne acrylic pressure sensitive adhesives synthesized using polymerizable surfactants (Latemul^®PD-104 and Sipomer^®Pam-200) or a polymerizable stabilizer (Sipomer^®Cops-1) has been studied. The use of a high pH during the polymerization process has a deleterious effect on the final adhesive properties because gel polymer is not formed. Interestingly, at low pH it is found that the surfactant concentration used during the polymerization process has also an effect on the polymer microstructure; the higher the surfactant concentration, the higher the final gel content of the latex. When polymerizable surfactants or a stabilizer are used the peel strength of the final films is considerably improved due to the surfactant incorporation into the polymer backbone and hence reduced surfactant migration to the air-film interface. Work of adhesion and shear adhesion failure temperature (SAFT) are not noticeably affected by surfactant migration but their performance is affected by the surfactant employed.     

The effect of γ-radiation on the mechanical properties of structural adhesive

The modular satellite concept iBOSS (intelligent Building Blocks for On-Orbit Satellite Servicing and Assembly) enables on-orbit servicing and reconfiguration of satellite systems and has the potential to be a game changer in the space industry. Such building blocks have to withstand all environmental loads in space, e.g.: radiation, vacuum and thermal cycling.The present paper investigates the mechanical properties of the two component epoxy adhesive 3M SW9323 under the environmental effect of radiation. This adhesive is part of the building block's primary structure. Furthermore, adhesive bonding is the sole joining technique used in the whole structure. It is therefore critical to know the influence of ionizing radiation on its load-carrying capacity. For this purpose bulk specimens were manufactured and exposed to γ-radiation, generated by a ⁶⁰Co source. Four different doses were achieved by varying the distance to the source and irradiation time. Afterwards the specimen were tested under tensile loading. Using the digital image correlation technique properties like elastic modulus, shear modulus, tensile strength and elongation at break were determined.The results show that the mechanical properties of the bulk specimen of 3M SW9323 are not influenced by γ-radiation up to a dose of 17.6 kGy. This is explained by the phenomena of crosslinking and chain scission which occur simultaneously and cancel each other out. In addition, Fourier-transform infrared spectroscopy (FTIR) was carried out to investigate if one mechanism is predominant. A slight shift in the spectra indicates the supremacy of chain scission.     

In vitro Streptococcus mutans biofilm formation on surfaces of chlorhexidine-containing dentin bonding systems

This in vitro study evaluated the influence of chlorhexidine diacetate (CDA) when blended within dentin bonding systems (DBSs) on Streptococcus mutans (S. mutans) biofilm formation.One commercially available 0.2% wt CDA-containing DBS (Peak Universal Bond) and five experimental 0.2% wt CDA-containing DBS formulations (experimental Adper Scotchbond 1XT plus experimental resins, R₂, R₃, R₄, R₅) were assessed vs their no-CDA containing counterparts. Twenty-eight DBSs disks were prepared for each group (6.4 mm×1.0 mm) and cured for 80 s at 800 mW/cm² in a nitrogen atmosphere. A modified Drip-Flow Reactor was used to grow S. mutans biofilms on specimen surfaces for 24 h and adherent, viable biomass was evaluated using a tetrazolium salt assay (MTT). Two specimens from each of the tested materials were processed with LIVE/DEAD stain and observed using laser confocal microscopy (CLSM) while two disks from each group were examined by using scanning electron microscopy (SEM).MTT assay, CLSM and SEM observations showed that CDA addition decreased, increased or did not change S. mutans biofilm formation. The lowest biofilm formation was obtained with Peak Universal Bond and R₅ (with and without CDA).It may be concluded that the chemical composition of DBSs determines their ability to promote or hamper biofilm formation. Therefore, CDA addition may be helpful in modulating biofilm formation provided that DBS formulation is tuned and optimized.     

Analysis of mixed adhesive joints considering the compaction process

Incorporating a material properties variation along the bondlines has proved to be a useful method for improving adhesive joints performance. In this work, the potential of the technique is analysed for a single lap joint using the mixing adhesives approach. In order to include the compaction process effect in the structural analysis during the joint assembly, a computational fluid-dynamic model capable of integrating different resins along the bondline has been developed. Then, the results obtained from this model are mapped into a finite element model through an application developed for this purpose. Several parametric studies have been carried out comparing different configurations in terms of maximum load capacity of the joints. Finally, one of these joints configurations has been manufactured using a special device developed for assembling these mixed adhesive joints and tested. This banded configuration have shown both numerically and experimentally an ultimate load improvement of over 70%.     

Experimental investigation on environmental degradation of automotive mixed-adhesive joints

In this paper, environmental strength degradation of 180 different adhesive single lap joints (SLJ), including mono-adhesive Araldite 2015, mono-adhesive Araldite AV138, and a mixed-adhesive of Araldite 2015 and Araldite AV138 subjected to moist conditions are experimentally studied. Four different moist conditions, i.e. dry, 75.3, 84.2 RH% and immersion in tap water, have been taken into consideration and the specimens are tested after exposing to these environments at room temperature for 0, 35, 80 and 270 days. The specimens have been tested in two different strain rate, i.e. 1 mm/min and 100 mm/min. The results reveal that although, in a dry environment, mixed-adhesive joints have higher failure loads in comparison to mono-adhesive SLJs, in a moist environment, they have the highest reduction in static failure load with regard to the mono-adhesive ones. Moreover, despite the finally brittle trend in failure load, mixed-adhesives manifest a behavior very similar to ductile mono-adhesives regarding elongation. Analytical predictions of failure load are also consistent with the experimental observations in dry condition.