Aspects on bond strength in sheet structures from TMP and CTMP – a review

High yield pulps (HYP), manufactured in mechanical and chemimechanical pulping processes, are mainly used in graphic papers and paper grades where a high bulk is preferable, like in paperboards. Moreover, packaging papers with very high demands on both dry and wet strength could be manufactured from HYP in a near future. Preferred bonds between fibre components (long fibres, shortened fibres and fines) in the various paper grades are quite different. In the review, plausible effects of mechanical interlocking, intermolecular interactions (“physical bonding”), hydrogen bonds, intermixing of polymers, additives and possible specific interactions in the formation of strong bonds in sheet structures from HYP are discussed. A required condition for high bond strength in sheets from HYP furnishes is that fibre components are forced into sufficiently close contact. This is to a great extent impeded if the fibre walls are too stiff. Consequently, the current review focuses on both how fibre fractions should preferably be developed for different end uses and how suitable bonds might be achieved in different paper grades. The ideal type of bonds is certainly different depending on the demands on the final paper quality.

Experimental study of an innovative driven and grouted soil nail (x-Nail)

This paper describes an experimental investigation of a newly developed driven and grouted soil nail (x-Nail), which combines the capabilities of a purely frictional driven nail and a compaction-grouted nail. The innovative design allows the x-Nail to be driven into the ground with a latex balloon attached that is used subsequently for compaction grouting. A grout bulb is thus formed at the driven end of the nail to improve its pull-out resistance. For compaction grouting, a special type of additive-mixed cement grout was used in this investigation because of its zero bleeding and high bond strength. A series of pullout model tests was conducted to examine the performance of the x-Nail compared to a purely frictional soil nail. It was found that more than 90% of the pullout force of the x-Nail was resisted by the expanded grout bulb and the end bearing resistance of the grout bulb increased with the increment of the injected grout volumes. The experimental results revealed that the pullout force of the x-Nail increased approximately 1800%, 1550%, 1200% and 900% compared to the purely frictional soil nail for the injected grout volumes of about 350 ml, 270 ml, 220 ml, and 170 ml, respectively.

Research on the Properties of High-strength Gypsum Based Tile Adhesive in Interior Decoration

In this paper, a new early strength tile adhesive is prepared by using α- high strength gypsum and its properties are discussed. The research methods refer to relevant Chinese standards. The results show that the tensile bond strength of the adhesive can reach 0.6 MPa in one day and 1.5 MPa in 7 days, which is close to 80% of 28-day strength. It is indicating that the adhesive has high bond strength, rapid strength development, and high dimensional stability. It effectively solves the problems that the traditional cement-based tile adhesive is prone to hollowing, falling off, and cracking. Additionally, no interface treatment is required during the using process of this gypsum-based adhesive.

Cold Spray Deposition of Pure Titanium Coating Onto High Strength Substrate With Ultra-High Bond Strength

Cold spray (CS) is a relatively new spray coating technology which has opened up a new avenue for deposition of bulk coatings with a thickness in the millimeter range. The unique bonding mechanism of the CS process facilitates deposition of commercially pure titanium (CP-Ti) on a wide range of substrates including high strength alloys. In this paper we present a multi-stage bond coat deposition process using a mixture of ultra-hard ceramic beads and CP-Ti prior to the top CP-Ti coating deposition to produce a coating layer with promising bond strength. In addition, three combinations of the carrier gas temperature (450, 540, and 550 °C), and pressure (2.5 and 3.8 MPa) were considered for maximizing bond strength. The relationship between bond strength and surface roughness was also examined. The shear test results indicated a significant high bond strength of approximately 195 MPa for the gas pressure of 3.8 MPa and temperature of 450 °C owing to the newly introduced bond coat deposition method. The relatively high bond strength is explained by the beneficial effect of multi-stage bond coat prior to the deposition of the bond coat. The results also indicated a tradeoff between bond strength and obtained surface roughness.

Influence of the laser-based surface modification on the bond strength for friction press joining of aluminum and polyethylene

Friction press joining is an innovative joining process for the production of plastic-metal joints without additives, in an overlap configuration. In order to achieve a high bond strength, the metallic joining partner is pretreated with laser radiation. Subsequently, heat is induced by friction and pressure during the joining process, causing the thermoplastic material to melt and adhere to the metallic joining partner. In this work, the temperature distribution during the process in the composite is analyzed and characterized. It was found that the occurring temperatures and temperature differences are not only dependent on the rotational speed, but also on the feed rate. It is also shown that the friction surface temperature can be used as an indirect control variable for a model-based, closed-loop control. Based on these findings, various surface modifications for the metallic joining partner were investigated and analyzed with regard to the maximum strength of the joint. It was observed that the highest tensile shear strength can be achieved with a quasi-chaotic nano structure. In addition, the joining compound was characterized by a thin section, facilitating the identification of specific zones in the joint. These investigations show the high potential for friction press joining of plastics and metals, and form the basis for a model-based control of the joining zone temperature.

A Tough, Water-Resistant, High Bond Strength Adhesive Derived from Soybean Meal and Flexible Hyper-Branched Aminated Starch

Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD’s flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites.

Strength Development Characteristic of Cementless Mortar for Repair of Concrete

Repair materials for concrete structures are often required to exhibit high bond strength at a concrete substrate, and it typically consists of ordinary Portland cement (OPC) incorporating expensive admixtures at a low water-to-binder ratio. Meanwhile, cementless mortar employs alkali-activation of cementless and pozzolanic precursors such as ground granulated blast-furnace slag (GGBFS) and fly ash (FA). The final product develops strength relatively faster than OPC, and its strength can be flexibly talyored by controlling the type and dosage of the activator. The present study investigates the strength development characteristic of cementles mortar for use in repair of concrete structures. Independent variables include mix proportions and curing conditions, which were chosen to optimize the performance of the cementless mortar.