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Scanning electron micrographs of unwelded (first row) and welded interface after peeling tests (second row) of TMP, CTMP, UKP and BKP papers, assembled by ultrasonic compression with a compressive stress of 5 MPa
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Paper-based packaging materials are generally assembled using adhesives formulated with oil-based polymers. These adhesives make the recyclability of the materials more complex and may be the source of material contamination by mineral oil. In view of developing an adhesive-free process, the potential of ultrasonic compression was investigated in t...
Citations
... At present, ultrasonic metal welding mainly includes four series: ultrasonic metal spot welding, wire harness welding, metal sealing and cutting, and metal roll welding [82][83][84][85]. It is widely used in automotive interior parts, electronics, electrical appliances, motors, refrigeration equipment, hardware products, batteries, solar energy, transportation equipment, toys, and other industries [51,54,86,87]. ...
... At present, ultrasonic metal welding mainly includes four series: ultrasonic metal spot welding, wire harness welding, metal sealing and cutting, and metal roll welding [82][83][84][85]. It is widely used in automotive interior parts, electronics, electrical appliances, motors, refrigeration equipment, hardware products, batteries, solar energy, transportation equipment, toys, and other industries [51,54,86,87]. ...
The lightweight alloy sheet materials have been widely used in industries such as automobiles, aviation, and aerospace. However, there are huge challenges in the structural joining process. Likewise, industries are probing new technologies and are rapidly adapting to more complex light alloy materials. The ultrasonic metal welding is a reliable solid-phase joining technology, which has incomparable development prospects in the high-strength joining of lightweight alloy sheet materials. This article summarizes the research progress of ultrasonic welding of aluminum alloy, magnesium alloy, and titanium alloy thin plates in recent years. The key features of this review article are the ultrasonic welding process, advantages, applications, and limitations. It introduces the welding process parameters to explore the breakthroughs for straightforward direction. Furthermore, to strengthen the phenomena, the current state of the ultrasonic welding of lightweight alloys and their future perspectives are also reflected.
... In this context, the main concern of the present study is to investigate on the ultrasonic (US) welding as a potential processing method to assemble papers coated with PVOH and grafted by chromatogeny. US welding has recently emerged as a possible solution to manufacture bio-based materials (Regazzi et al. 2019a;Teil et al. 2021) and to assemble papers and paperboards (Regazzi et al. 2019b;Monot et al. 2021;Charlier et al. 2021). US welding is a processing method which consist in applying high-frequency acoustic vibrations (20-40 kHz) under pressure (Tolunay et al. 1983;Benatar et al. 1989). ...
... More recently, Teil et al. and Regazzi et al. manufactured and characterized biocomposites made of native starch granules and wood fibers and obtained by ultrasonic compression molding (Regazzi et al. 2019a;Teil et al. 2021). Only a few recent studies, done by the same team of authors, discuss the use US welding to assemble paper-like materials (Regazzi et al. 2019b;Monot et al. 2021;Charlier et al. 2021). While working with 100% lignocellulosic papers, Regazzi et al. showed that papers can be welded only for high lignin and hemicelluloses contents in the paper pulp (Regazzi et al. 2019b). ...
... Only a few recent studies, done by the same team of authors, discuss the use US welding to assemble paper-like materials (Regazzi et al. 2019b;Monot et al. 2021;Charlier et al. 2021). While working with 100% lignocellulosic papers, Regazzi et al. showed that papers can be welded only for high lignin and hemicelluloses contents in the paper pulp (Regazzi et al. 2019b). Structural analyses have suggested that the establishment of adhesion originates from a thermoplastic mechanism. ...
Chromatogeny grafting is an efficient method to hydrophobize lignocellulosic materials. Grafted papers are good candidates to replace plastic products in several applications requiring water barrier properties such as food packaging. However, chromatogeny grafting tends to reduce the sealability which is currently limiting the development of these materials. In this context, this study aims to investigate on the ultrasonic welding as a processing method to assemble papers coated with poly(vinyl alcohol) and grafted by chromatogeny. To reach such a goal, grafted and non-grafted papers, presenting different poly(vinyl alcohol) coating weight, have been welded under controlled conditions and peeled to evaluate the strength of welded joints. Results indicate that grafted-papers can be assembled by ultrasonic welding. However, it requires more severe processing conditions and the resulting peeling strength is lower than for non-grafted papers. Nevertheless, mechanical performances are quite satisfying in regard of the requirements of most packaging applications. Chromatogeny grafting modifies the adhesion mechanisms involved in the formation of the welded joints. Joint strength also increases with the poly(vinyl alcohol) coating weight which can be used as an adjusting parameter to optimize the adhesion. Overall, ultrasonic welding has proven its efficiency to assemble chromatogeny grafted-papers which is promising regarding the development of paper-based water barrier packaging solutions.
... To this day, only one research paper on the ultrasonic welding of paper-like materials has been reported so far [22]. It showed that raw papers can be welded only for high lignin and hemicelluloses contents in the paper pulp. ...
... The latter could be defined by the amount of power per volume unit received by the welding interface. Previous works done on the vibrational welding of wood [15] and on the ultrasonic welding of papers [22] have shown that welded joints display higher densities than the initial material. In the case of papers, this densification tends to reduce the thickness at the welding joint. ...
Ultrasonic welding is a serious candidate in the development of methods to assemble papers and paperboards without using additional substances. However, the ultrasonic welding of papers remains a technological challenge considering the low weldability of lignocellulosic materials. This study aims to investigate on the ultrasonic welding process applied to papers in order to identify the processing conditions which favor the formation of strong welded joints. To reach such purpose, an experimental strategy was developed by combining the characterization of welded materials and the monitoring of process parameters. Experimentations were performed using a reference paper displaying a good weldability to specifically highlight the contribution of process parameters. Results indicate that the process is highly sensitive to vibration amplitude, power supplied by the high frequency generator, and sample thickness. Power seems to be a reliable indicator of the severity of the process. A strong decrease in the strength of the welded joints is observed when working with low thicknesses. It seems that the layers coated on top of papers are the main part of the material contributing in the development of adhesion at the welding joint. Overall, instrumenting the device has led to a better understanding of the ultrasonic welding of papers.
... The localized increase in temperature melts the thermoplastic polymer, which results in the welding of the two parts. The potential of ultrasonic welding for bonding 100 % lignocellulosic papers has been recently investigated (Regazzi et al. 2019). For papers containing high lignins and hemicelluloses contents (50% in total), the adhesion strength generated by welding is almost equivalent to the one obtained by gluing. ...
... The conversion from thermoelectric voltage to temperature was obtained from the NIST ITS-90 thermocouple database. While thermocouples can concentrate the ultrasonic energy and therefore provide misleading readings (Villegas 2015), these points have been addressed previously, and a temperature monitoring procedure was established (Regazzi et al. 2019). Considering the measured temperature range and the repeatability of the results obtained with this set-up, this method provides relevant qualitative information on the heating process during the US welding of FBBs. ...
... It is worth noting that the FBB was significantly densified in the welding zone as it was observed in previous studies on the ultrasonic welding 100 % lignocellulosic paperlike materials (Regazzi et al. 2019) or the vibrational welding of wood (Ganne-Chédeville et al. 2006). ...
Today's environmental concerns are pressuring industries to substitute paper-based materials in place of plastics in many sectors including packaging. However, assembling papers and paperboards using environmentally friendly solutions remains a technological challenge. In this context, ultrasonic (US) welding is an alternative to adhesives. In this work, the potential of US welding to assemble folding boxboards was investigated. Folding boxboards are commonly coated to enhance printability. This coating is generally composed of mineral pigments (85 to 90%) and polymer binders (10 to 12%). This study evaluated whether the presence of the coating layer allows the assembly of paperboards by US welding. Results indicated that welding coated folding boxboards is possible provided that coating weight and binder content are high enough. The mechanical performances of the welded boards met the requirements of most packaging applications. Adhesion in the welded joint resulted from a combination of thermoplastic (melting and flowing of the binder) and thermoset (degradation reactions) effects. However, it was not possible to assemble coated folding boxboards without degrading the welding zone. While the materials and process need to be optimized, this work represents a big step forward toward the adhesive-free assembling of paper-based materials.
... The aim of UCM is to induce the welding of granules and fibers by local heating under the effect of viscous dissipation and/or inter-particle friction [16][17][18]35]. This technique consists in simultaneously applying a constant average compression stress of 15 MPa and a forced 20 kHz vibration of 60 μm amplitude on the top of the sample during 0.70 s. ...
... This technique consists in simultaneously applying a constant average compression stress of 15 MPa and a forced 20 kHz vibration of 60 μm amplitude on the top of the sample during 0.70 s. During that time, the temperature of the sample should not increase over 200°C, as measured by the authors during the ultrasonic welding of lignocellulosic materials [35]. Once again, this temperature was below the degradation temperatures of the constituents of the composite materials. ...
Novel biocomposites were fabricated using preforms of unmodified starch powder and wood pulp fibers. Stacks
of preforms were consolidated using thermo-compression (TCM) and ultrasonic compression moldings (UCM).
The characterization of the microstructure of the biocomposites showed that TCM enabled a better preservation
of the crystallinity of starch granules during their welding than UCM. However, UCM allowed a significant gain
in processing time. For the best set of forming and material parameters, the composites exhibited an elastoplastic
response with strain hardening. Their Young's modulus, flexural strength and strain at ultimate stress reached up
to approx. 6 GPa, 70 MPa, and 8%, respectively. The best properties were associated to the partial preservation
of the native crystallinity of starch and lowered porosity. Bleached and fibrillated fibers with a large aspect ratio
also contributed to the enhancement of composite properties. These effects were explained by a better starchfiber
interface and the presence of a network of connected fibers within the composites.
With the growing emphasis on minimization of global plastic waste, flexible fibre‐based packaging has gained significant interest over the past few years. Heat‐sealing technology is commonly applied for vertical form‐fill‐seal machine to provide tight closure of packages for maintaining food quality and shelf life. Several different seal bar geometries and adequate heat‐seal parameters are required to improve the seal tightness of the packages. This study aims to compare the heat sealability of thermoplastic film (OPP/PE) and paper‐based materials in vertical form‐fill‐seal machine using various seal bar profiles. The investigation includes seal strength measurement, understanding the causes of leak formation, seal tightness and inspection of the seal using scanning electron microscopy. Results reveal that OPP/PE material has exceptional seal strength and leakproof ability compared with paper‐based materials. However, it has limited operating window because the material shrinks and coarsens at approximately 140°C. Sealing temperature and dwell time are found to be the major factors affecting the seal strength of paper‐based material. Results reveal the PE‐coated papers exhibit nearly twice the seal strength compared with the dispersion‐coated paper. It was difficult to achieve good hot‐tack values with dispersion‐coated paper. During testing, all the paper‐based materials experience delamination and fibre tear, and its severity increases with the increasing material grammage. As plateau temperature is reached, the fibre delamination remains relatively constant. The serrated geometry of seal bar design plays a significant role in providing a satisfactory airtight seal, particularly around the pouch's layer jump. However, flat seal bar designs are not recommended for gas tight applications for paper‐based materials.
In recent days, ultrasonic welding processes are playing an extraordinary role in all industrial applications. Metals and non metals were processed under USW with different melting points. Thin wires of foils are easily welded through this process. High quality of welded joints can be achieved through USW without protective gas shield. The different process factors such as amplitude of vibrations, welding mode, down speed, pressure of trigger, weld time and clasp time were considered to determine the strength and quality of the joints. The varieties of joint designs were possible with definite features. The different ranges of frequencies have been applied in between the interface of the work piece. The plastic deformation of the metal occurred due to incorporation of vibrational energy and localized melting of the metal along the joint to be welded. The welded joints were quickly completed without any drying process which is suitable to soft and hard materials. The joint quality depends on the ultrasonic vibrations. The work piece to be joined were detained together under pressure and applied to ultrasonic vibrations (range between 20 and 40 kHz). This review paper deals about the ultrasonic welding characteristics, interface of welding joints, performance and welding factors for different materials.
