Thermoforming Technique Research Articles

The Impact of Adding Chitosan Nanoparticles on Biofilm Formation, Cytotoxicity, and Certain Physical and Mechanical Aspects of Directly Printed Orthodontic Clear Aligners.

Aligner treatment is associated with bacterial colonization, leading to enamel demineralization. Chitosan nanoparticles have been demonstrated to have antibacterial properties. This in vitro study aims to determine the effect of adding chitosan nanoparticles to directly 3D-printed clear aligner resin with regard to antibiofilm activity, cytotoxicity, degree of conversion, accuracy, deflection force, and tensile strength. Different concentrations (2%, 3%, and 5% w/w) of chitosan nanoparticles were mixed with the clear resin, and the samples were then 3D printed. Additionally, the thermoforming technique for aligner manufacturing was utilized. The obtained specimens were evaluated for antibiofilm activity against Streptococcus mutans bacteria and cytotoxicity against L929 and 3T3 cell lines. Additionally, Fourier transform infrared spectroscopy via attenuated total reflection analysis was used to assess the degree of conversion. Geomagic Control X software was utilized to analyze the accuracy. In addition, the deflection force and tensile strength were evaluated. The results indicated a notable reduction in bacterial colonies when the resin was incorporated with 3 and 5% chitosan nanoparticles. No significant changes in the cytotoxicity or accuracy were detected. In conclusion, integrating biocompatible chitosan nanoparticles into the resin can add an antibiofilm element to an aligner without compromising the material's certain biological, mechanical, and physical qualities at specific concentrations.

MatriGrid® Based Biological Morphologies: Tools for 3D Cell Culturing.

Recent trends in 3D cell culturing has placed organotypic tissue models at another level. Now, not only is the microenvironment at the cynosure of this research, but rather, microscopic geometrical parameters are also decisive for mimicking a tissue model. Over the years, technologies such as micromachining, 3D printing, and hydrogels are making the foundation of this field. However, mimicking the topography of a particular tissue-relevant substrate can be achieved relatively simply with so-called template or morphology transfer techniques. Over the last 15 years, in one such research venture, we have been investigating a micro thermoforming technique as a facile tool for generating bioinspired topographies. We call them MatriGrid®s. In this research account, we summarize our learning outcome from this technique in terms of the influence of 3D micro morphologies on different cell cultures that we have tested in our laboratory. An integral part of this research is the evolution of unavoidable aspects such as possible label-free sensing and fluidic automatization. The development in the research field is also documented in this account.

A review on stamp forming of continuous fibre-reinforced thermoplastics

Continuous fibre-reinforced thermoplastics (FRTPs) are replacing metals in certain applications in the aerospace industry due to their superior properties e.g., high strength-to-weight ratio and good fatigue resistance. Adopting these lightweight materials in vehicles is a solution for improving vehicle efficiency across the transport industry. Among various manufacturing techniques for FRTP parts, stamp forming is one of the most advantageous when small structures and mass production are targeted. However, a significant barrier for this technique is the quality control of manufacturing. The current paper reviews the development of stamp forming technology, benefits of using such technology and the typical quality issues in stamp forming of FRTP parts. First, advantages of stamp forming, compared to other thermoforming techniques, are discussed, followed by a review of the historical development of the process. Second, deformation mechanisms of FRTPs during stamp forming are examined, with particular focuses on the frictional behaviour and testing thereof. Third, the main defects associated with stamp forming are considered, alongside suggestions towards reducing their presence. Finally, an extensive survey of the effect of process parameters on the mechanical properties of formed parts is included, with generally expected trends highlighted and methodologies for finding optimum conditions presented. Based on the thorough review of state-of-the-art stamp forming, future trends and research gaps to be tackled for widening the applicability of FRTP stamp forming are suggested.

Anisotropy in conventional and uniaxially thermoformed auxetic polymer foams

Auxetic (negative Poisson's ratio) open cell polymeric foams have been traditionally produced using thermoforming techniques coupled with the volumetric compression of conventional (pristine) off-the-shelf foams. The anisotropy of the pristine foam plays however a strong role on the performance of thermoformed auxetic foams, and this is the subject studied in this work. Micro computed tomography (μ-CT) scans indeed show that the cell structures of the pristine foam exhibit an elongated convex polyhedron shape, with more ribs oriented along the foam rising direction d 1 . The modulus along d 1 can be up to 70% larger than the one along the transverse directions, and the Poisson's ratios in different planes are also noticeable different, ranging from 0.2 to 0.85. Three types of auxetic foams uniaxially thermoformed along the three orthogonal directions of the conventional porous material are here developed, and all show different mechanical performances due to the anisotropy of the conventional baseline foam. The auxetic foams show significant auxetic behavior along the thermoforming direction only when thermoformed along the transverse directions of the pristine foam (d 2 or d 3 ) and loaded along the foam rising direction (d 1 ); in that case, the negative Poisson's ratio reach values as low as −1. In other cases, the auxetic performance is not evident, and the Poisson's ratio is close to 0. Finite Element models of the pristine and auxetic foams have been also here developed based on the 3D models from μ-CT, and the stiffness-strain curved derived from those coincide well with the experimental results. The simulated deformation mechanisms of the cell structures inside different foams help to explain the anisotropic performance of the foams and the differences between compressive and tensile properties.

Examination of thermoforming techniques to secure mouthguard thickness of the labial and buccal sides with a single sheet: An in vitro study.

Mouthguards must have an appropriate thickness to prevent oral trauma during sports. The aim of this study was to establish a thermoforming technique to secure the labial and buccal thicknesses of the mouthguard with a single sheet. Mouthguards were thermoformed using 4.0-mm thick sheets manufactured by extrusion molding, a plaster model, and a vacuum forming machine. Two sheet installation conditions were compared: the sheet extrusion direction was either parallel (P) or vertical (V) to the model's centerline. In each extrusion direction, two forming conditions were compared: (1) the sheet was formed when it sagged 15-mm below the sheet frame at the top of the post (control group; C-P, C-V); and (2) the sheet frame was lowered 50-mm below the ordinary level and heated, the frame was lowered when it sagged 15-mm, and the model was moved forward 20-mm before formation (experimental group; E-P, E-V). Difference in thickness (incisal edge, labial surface, cusp, and buccal surface) due to sheet extrusion direction and forming conditions were analyzed by two-way ANOVA and the Bonferroni method. At all measurement sites, a significant difference in thickness depending on the sheet extrusion direction was observed in the experimental group (p<.01), but not in the control group. Difference in thickness depending on the forming condition was observed at all measurement sites, and the thickness was in the order C-P, C-V<E-P<E-V. Thicknesses of E-P and E-V were 3.01±0.03mm and 3.25±0.02mm on the labial surface, and 2.81±0.02mm and 3.02±0.02mm on the buccal surface. It was possible to obtain 3mm or more thickness on the labial and buccal sides with a single sheet by adjusting the sheet extrusion direction and the heating method of the sheet, and by applying the thermoforming method where the model is moved forward just before formation.

Effect of yarn singeing and commingling on the mechanical properties of jute/polypropylene composites

AbstractLightweight and inexpensive natural fiber‐reinforced composites are gaining market share due to their environment‐friendly and sustainable nature. Among these, thermoplastic composites are preferred due to their recycling ability. However, their fabrication is a difficult task due to the higher viscosity of thermoplastic matrices. In the present study, we present the comparison of mechanical properties of jute/polypropylene composite samples fabricated using the conventional thermoforming technique with those fabricated using the commingled yarn technique. The effect of singeing of jute yarn on its mechanical properties as well on the weaving efficiency of jute fabric as reinforcement for composites was also studied for the first time. Mechanical properties, that is, tensile, flexural, and instrumented Charpy impact properties, were tested using standard testing methods. It was found that singeing improves mechanical properties of jute yarn as well as its performance during weaving. Furthermore, the yarn commingling not only simplifies/shorten the composite fabrication process but also improves the mechanical properties of the developed composites significantly in comparison to conventional thermoforming technique.

Quasi-Static and High Strain Rate Uniaxial Compressive Response of Recycled Polycarbonate from Industrial Waste

This work evaluates the mechanical and dynamic behavior of recycled polycarbonate (rPC) from industrial waste. This study aims to verify whether the recycled process adopted for polycarbonate promotes both mechanical and dynamic properties values under compressive stress, similar to those found for virgin polycarbonate. The mechanical recycling of the rPC was carried out using the thermoforming technique in a thermal press. Two tests were carried out to evaluate the dynamic response of rPC. The quasi-static compression test was performed on a universal machine. The dynamic in a split Hopkinson pressure bar was performed with three different strain rates. The results showed that the mechanical and primary recycling adopted in this work promoted values of yield stress in compression (77 MPa) and dynamic (up to 118 MPa), close to or superior to those reported so far in the literature.

The effect of using modern technologies to enhance aesthetic Values of the surface texture of the fabric in draping

The current research aims to use the technique of thermoforming fabrics to present a new method for creating new formulations on mannequins by using some newly designed fabrics that represent a new image in changing the general shape of the cloth, in terms of texture, surface of the cloth and its use. This came to produce designs of an aesthetic form characterized by sophistication, consistent with the requirements of the modern era and fashion, and this technology depends on the interaction of textile fibers with heat of various degrees using the air heat gun. The research problem is crystallized in the following questions: To what extent can the proposed designs be implemented using the technology of thermal fabric scissors in ready-to-wear factories? What is the benefit of the fabric thermoforming technique in the decoration of the executed pieces? What is the possibility of making use of synthetic fabrics in creating suggested designs for women? How satisfied are the professionals with the proposed designs? The importance of the research is due to the fact that it is a new addition to the field of shaping on mannequin by using a heat source on the cloth as the use of completely different fabrics after giving different effects to the fabrics under study using modern techniques represented in the use of thermal scissors as well as to highlight the aesthetic appearance of the surface and texture of the fabric in the design method on The mannequin is also a new idea for other research through the use of thermal scissors to express the texture of the cloth and give it specific decorations. The study aimed to identify the materials that can be used in making designs on mannequins as well as measuring the acceptance of specialists to change the texture and surface of the cloth and employ the aesthetic and plastic properties of the fabrics under study in the draping.

Thermoforming technique for suppressing reduction in mouthguard thickness: Part 2 Effect of model height and model moving distance.

Wearing a mouthguard reduces the risk of sports-related injuries, but the material and thickness of the mouthguard have a substantial impact on its effectiveness and safety. The aim of this study was to establish a thermoforming technique in which the model position is moved just before formation to suppress the reduction in thickness. The aim of this study was to assess the effects of model height and model moving distance on mouthguard thickness. Ethylene-vinyl acetate sheets of 4.0mm thick and a vacuum forming machine were used. Three hard plaster models were trimmed so that the height of the anterior teeth was 25mm, 30mm and 35mm. Model position (MP) was 40mm from the front of the forming unit. The sheet was softened until it sagged 15mm, after which the sheet frame was lowered to cover the model. The model was then pushed from behind to move it forward, and the vacuum was switched on. The model was moved at distances of 20mm, 25mm or 30mm whereas a control model was not moved. Thickness after formation was measured with a specialized caliper. Differences in mouthguard thickness due to model height and moving distance were analysed by two-way ANOVA and Bonferroni's multiple comparison tests. Sheet thickness decreased as the model height increased. Each MP condition was significantly thicker than the control in each model. There was no significant difference among MP conditions except for the buccal surface. Moving the model forward by 20mm or more just before formation is useful to secure the labial thickness of the mouthguard. This thermoforming technique increased the thickness by 1.5 times or more compared with the normal forming method, regardless of model height.

Thermoforming Technique for Suppressing Reduction in Mouthguard Thickness

Wearing a mouthguard reduces the risk of sports-related injuries, but the material and thickness of the mouthguard has a substantial impact on its effectiveness and safety. The aim of this study was to establish a thermoforming technique in which the model position is moved just before formation to suppress the reduction in thickness. Mouthguards were vacuum formed using ethylene-vinyl-acetate sheets with a thickness of 2.0, 3.0, and 4.0 mm. The working model was trimmed to the height of 25-mm at the maxillary central incisor and 20-mm at first molar. The model was placed with its anterior rim positioned 40-mm from the front of the forming table. Two forming methods were compared: 1) the sheet was formed when it sagged 15-mm at the top of the post under normal conditions (control); and 2) the sheet frame at the top of the post was lowered and the model was covered when the sheet sagged 15-mm, the rear side of the model was pushed forward 20-mm, and the mouthguard was formed (MP; model position). Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper accurate to 0.1-mm. The difference in the reduction in thickness depending on the forming methods and sheet thicknesses were analyzed by two-way ANOVA and Bonferroni’s multiple comparison tests. Reduction in thickness was greater for thicker sheets, and the reduction in thickness for the MP was less than that for the control. The reduction in labial for the MP was an exception; the reduction in thickness was only about half that of the control. The thermoforming technique of moving the model forward just before vacuum formation was effective for suppressing the mouthguard thickness reduction, which in thickness of the labial side can be reduced to about half of the normal forming method.

Thermoforming technique for maintaining the thickness of single-layer mouthguard during pressure formation.

Using mouthguards can reduce the risk of injury when playing sports, but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of moving the model position just before formation in the pressure forming technique to maintain the thickness of a single-layer mouthguard. A 4.0-mm-thick ethylene vinyl acetate (EVA) mouthguard sheet (diameter: 125mm) and a pressure forming machine were used. The working model was placed with its anterior rim positioned 40mm from the front of the forming table. The sheets were placed in the forming table with the sheet extrusion direction either vertical (V) or parallel (P) to the model's centerline. Two molding methods were compared: (a) The sheet was formed when it sagged 15mm (control) and (b) the sheet was covered on the model when it sagged 15mm, next the model was pushed forward 20mm, and the sheet was then formed (MP). Mouthguard thickness was measured for the labial surface, palatal surface, cusp, and buccal surface using a specialized caliper. Thickness differences according to molding methods and sheet extrusion directions were analyzed by two-way ANOVA. The thicknesses of the labial surface, cusp, and buccal surface were significantly larger in MP than in the control (P<0.01). In particular, the thickness differences caused by the molding method were large on the labial and buccal surfaces: For the control, the thicknesses were 1.9±0.03 and 2.1±0.02mm, whereas for MP, they were 3.2±0.03 and 2.9±0.03mm, respectively. The molding method of moving the model forward just before formation was useful as a thermoforming technique for maintaining the thickness of single-layer mouthguards during pressure forming with 4.0-mm-thick EVA sheet. This method produced labial and buccal thicknesses of 3.2±0.03 and 2.9±0.03mm.

Thermoforming method to effectively maintain mouthguard thickness: Effect of moving the model position just before vacuum formation.

Mouthguards can reduce the risk of sports-related injuries but the sheet material and thickness have a large effect on their efficacy and safety. The aim of this study was to investigate the effect of the thermoforming technique that moves the model position just before vacuum formation. Ethylene vinyl acetate sheets of 4.0-mm thickness and a vacuum forming machine were used. The working model was placed with its anterior rim positioned 40mm from the front of the forming table. Three forming conditions were compared: (a) The sheet was formed when it sagged 15mm at the top of the post under normal conditions (control); (b) the sheet frame was lowered to and heated at 50mm from the level of ordinary use, and the sheet was formed when it sagged 15mm (LH); and (c) the sheet frame at the top of the post was lowered and covered on the model when it sagged 15mm. Subsequently, the rear side of the model was pushed to move it forward 20mm, and it was then formed (MP). Sheet thickness after fabrication was determined for the incisal edge, labial surface, and buccal surface using a specialized caliper accurate to 0.1mm. Thickness differences among forming conditions were analyzed by one-way ANOVA and Bonferroni's multiple comparison tests. A significant difference was observed for all measurement points, and the thickness after formation increased in the order of control, LH, and MP. Particularly on the labial surface, MP was able to yield about 1.7 times the thickness (about 3.1mm) of the control. The forming method of moving the model forward just before vacuum formation was effective for suppressing the mouthguard thickness reduction, which is capable of securing the labial thickness at 3mm or more with a single layer.

Effects of fabric structure on the formability characteristics of thermoplastic composites under various process conditions

Thermoplastic composites are broadly utilized for structural and automotive applications due to their higher specific strength and modulus, higher strain to failure, recyclability, and unlimited shelf life. This study investigates the effects of fabric structure on the forming behaviour of glass fabric reinforced polypropylene composites during the sheet forming of a doubly curved shape. Stamp forming, a novel thermoforming technique, is mostly used for hemispherical forming of thermoplastic composites. The study also investigates the influence of process parameters such as die temperature, blank temperature, and blank holder force on sheet formability. Forming ratio, thickness distribution, material draw-in, and punch force were used for the evaluation of the formability of composites. Conventional and novel plain weave glass fabric reinforced polypropylene composite laminates were fabricated using the film stacking technique. Thermo-stamp forming experiments were conducted on the basis of the Taguchi’s L9 orthogonal array. Experimental results revealed better forming characteristics by the novel glass fabric reinforced composite than for the conventional glass fabric reinforced composite. Production of defect-free components under high die temperature, low blank holder force, and medium blank temperature process condition was observed.

The case of interim denture applying for thermoforming technique

Patients who get tooth loss would also lost their esthetic, stability and functional aspect suddenly. They have to get provisional restoration immediately. This case reports a satisfied result that thermoforming technique is good for patients to get injury from unexpected tooth loss.

2.5D Smart Objects Using Thermoplastic Stretchable Interconnects

This contribution describes the technology used to produce thermoplastically deformable electronics, based on flexible circuit board technology, to achieve low-cost 2.5D free-form rigid smart objects. These one-time deformable circuits employ a modified version of the previously developed meander-based “polymer-last” technology for dynamically stretchable elastic circuits. This is readily achieved by substituting the dynamically stretchable elastomeric materials (e.g. silicone) with thermoplastic polymers (e.g. polycarbonate). Afterwards the circuit is given its final form using widely available thermoforming techniques, such as vacuum forming, where the material is heated above its glass transition temperature and drawn against a forming tool by a strong vacuum. After cooling down the thermoplastic retains its shape without inducing large internal stresses. The presented method allows for the production of these circuits on a flat substrate, using standard printed circuit board production equipment, with deformation only taking place afterwards; eliminating the need for large investments and reducing the cost of fabrication. Potential advantages over competitive methods are reductions in weight and material usage, decrease of mechanical complexity; lower tooling cost, increased resilience, and a higher degree of manufacturer independence due to adhering to standard industrial practices. This is realized by starting production from a flexible circuit board, manufactured by an industrial supplier using polyimide flexible copper clad laminate, which is attached to a temporary reusable carrier board through means of a silicone based high-temperature pressure sensitive adhesive. Through selective laser structuring the meander and island outlines of the flexible circuit are defined, without causing damage to the carrier board or pressure sensitive adhesive. After removing the residual material the circuit is assembled using high-temperature lead-free solder, made possible by the temporary carrier keeping the circuit in place at these elevated temperatures. The circuit is then transferred into a thermoplastic laminate, which is deformed into its final shape. After demonstrating the need for stretchable electronics for this application, this contribution describes the method used to design, fabricate, and test the first one-time deformable circuits manufactured using the presented technology. Using the initial set of observations a series of preliminary design rules is established, both for the circuit and choice of materials. The feasibility of this manufacturing method was then demonstrated through a small scale production run using lab scale equipment, where a large quantity of high power LEDs was integrated into a one-time deformable device made out of polystyrene and thermoplastic polyurethane. These devices were then tested by exposing them to real world conditions for several days.

An Electrochemical Investigation of the Impact of Microfabrication Techniques on Polymer-Based Microelectrode Neural Interfaces

The electrochemical (EC) properties of microelectrodes on flexible polymer substrates can vary as a result of microfabrication and postfabrication processes. These in turn may impact the chronic recording performance of such electrodes. In this paper, electrochemical techniques were utilized for the preparation and nonbiological evaluation of microfabricated flexible neural probes consisting of platinum electrode recording sites supported and insulated by Parylene C. The polymer substrate mitigates the mechanical mismatch between neural tissue and the probe. In addition, the thermoplastic nature of the polymer enables the probe to be shaped postfabrication using a thermoforming technique to impart a unique 3-D structure that further promotes tissue integration and supports the use of bioactive coatings. The EC techniques provided a simple means to clean electrode surfaces (80.2% decrease in 1-kHz impedance), identify functional devices, and evaluate their EC properties prior to implant. Both electrochemical impedance spectroscopy and cyclic voltammetry measurements were performed on electrode sites following fabrication, cleaning, mechanical manipulation for assembly, thermoforming, and sterilization. The results reveal in some cases changes in EC properties. Although changes following thermoforming did not impact the ability to acquire electrophysiological recordings, further investigation with additional tools is required to elucidate the exact nature of the structural and EC changes resulting in the observed increase in impedance and reduction in electrode surface area following thermoforming.

A Robust Experimental Methodology for Polymer Bubble Inflation

In thermoforming technique thermoplastic sheets are heated up well above their glass transition temperature and formed to the required shape by using an appropriate mold. Characterization of thermoplastic materials for thermoforming can be accomplished by employing polymer bubble inflation and rheology tests instead of undertaking expensive biaxial tensile testing. Polymer bubble inflation technique is very sensitive to process condition variations, so a robust experimental methodology is essential. Design and development of one such experimental system was undertaken by carrying out a variety of preliminary tests. This paper presents the experimental methodology developed for polymer bubble inflation. The developed experimental system demonstrates highly repeatable polymer bubble inflations. Bubble inflations were conducted at different temperatures and different diameter circular clamping using acrylonitrile butadiene styrene (ABS) thermoplastic. Polymer sheet initial sag due to heating and its influence on bubble inflation have been captured by using the experimental system.

2132 テキスタイルコンポジットチューブの口広げ加工(S27-1 複合材の加工,S27 複合材料の加工と評価)

Flaring process is studied as one of thermoforming techniques for FRTP braided composite tubes in this study. The composite tubes are fabricated from cowoven braid by internal pressure bonding method, which consists of carbon braid and polyamide resin. The experimental results show that the flaring process is available as one of the thermoforming for braided composite tubes.

A new, simple method of making a spacer in interstitial brachytherapy for mobile tongue cancer

Objectives. This article demonstrates a new method of making a spacer that increases the distance between the mandible and implanted radioactive sources in interstitial brachytherapy for patients with mobile tongue cancer. Study design. Fifty-three patients with mobile tongue cancer underwent interstitial brachytherapy with spacers made by this new technique. Results. Our spacer is not difficult to create or to use. The spacer was made from a plastic splint by using thermoforming techniques and quick self-curing resin, which did not need waxing, wiring, or casting. The surface of the spacer, which comes in contact with the tongue, is smooth because it is covered with tissue-conditioning material. There were no complaints of pain from the patients. Osteoradionecrosis of the mandible developed in only 1 (1.9%) of these patients. Conclusions. This spacer is simple to make and prevented osteoradionecrosis. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:519-21)

Spherical Shape Thermoforming of Textile Thermoplastic Composite Tube.

This paper deals with deformation characteristics of textile composite tubes in spherical shape thermoforming process. The composite tubes are made of cowoven braid, which consists of polyamide resin and carbon braid with thin thickness and high fiber volume fraction, and are fabricated by internal pressure bonding method. Spherical shape closed dies of two different sizes are used in the experiment. The specimen is deformed at a temperature that makes the specimen soft enough to be deformed. Several combinations of internal pressure and axial displacement, which are controlled by a personal computer, are applied to the specimen during forming. An expression to predict a required axial displacement for the forming was derived from geometric deformation model of a braid. A spherical shape part being about two times as large as original tube diameter is obtained under suitable forming conditions. Calculated axial displacements agree with experimental results. It is proved that the derived equation is valid to predict required axial displacements for spherical shape forming. Experimental results reveal that this forming process has a potential as one of thermoforming techniques for the composite tubes.