Thermoforming Method Research Articles

Polymer Composite Thermoforming: Ultrasonic-Assisted Optimization for Enhanced Adhesive Performance in Automotive Interior Components.

Dual-component epoxy resins are widely used for bonding different materials in automotive interior processing. However, due to the complexity and variability of automotive interior parts, uneven temperature distribution on curved surfaces during the thermoforming process can lead to uneven thermal stress distribution, damaging the interior components. This study focuses on addressing the damage issues caused by uneven thermal stress distribution during the thermoforming of automotive interior components. By monitoring the temperature and strain on the adhesive surface of the interior components during processing, using sensors and combining the readings with a finite element simulation, damage to the adhesive during processing was simulated. Based on this, a segmented thermoforming method for the model surface was employed, but it was found that this method did not significantly reduce the level of damage to the adhesive during application. Building upon the segmented simulation, significant results were achieved by applying temperature modulation at a certain frequency to adjust the damage of the interior components during processing. The techniques used in this study successfully reduced the unevenness of the adhesive surface temperature, improved the performance of the adhesive during application through segmented optimization and the application of ultrasound-assisted techniques, and markedly reduced the manufacturing process's energy consumption.

Robust, waterproof, and degradable cellulose-based polyimine vitrimer for plastic replacement

The increasing application of non-degradable petroleum-based plastics has resulted in serious environmental pollution. Renewable and degradable cellulose-based materials are attractive candidates to replace petroleum-based plastics. However, the strong hydrogen bond (H-bond) interactions of cellulose result in its poor plastic formability such as thermoforming. Herein, a novel and effective thermoforming method of cellulose was developed by modifying cellulose into cellulose-based polyimine vitrimer (Cel-PI) via introducing dynamic imine bonds between cellulose molecular chains using Schiff-base reaction. The presence of dynamic imine bonds enables the heat-induced dynamic exchange and stress relaxation behavior of Cel-PI networks, making the excellent thermo-processability of Cel-PI. The as-synthesized Cel-PI powders can be easily thermoformed into Cel-PI film via heat-pressing approach without adding any plasticizers. The resulting Cel-PI film exhibits high Young’s modulus (2.9 GPa), high strength (46.3 MPa), good self-healing ability, excellent waterproof capability and organic solvent stability, and high thermal stability. Moreover, it can be chemically degraded, biodegraded, and recycled. Therefore, Cel-PI represents a promising and sustainable petroleum-based plastic replacement.

Effect of nano-serpentine and nano-La2O3 on the frictional properties of PTFE composites in seawater environment

PurposeThis paper aims to investigate the tribological properties of polytetrafluoroethylene (PTFE) composites modified by nano-serpentine and nano-lanthanum oxide in a seawater environment.Design/methodology/approachIn this paper, seven PTFE composites were prepared by unified design method and vacuum thermoforming method, and their hardness, water absorption and tribological properties were measured under seawater environment. The modification effects and thermal stability of the materials were analyzed by Fourier transform infrared spectroscopy, thermal gravimetry and differential scanning calorimetry. This paper analyzed the wear mechanism of PTFE composites by scanning electron microscopy and energy spectroscopy.FindingsThe results showed that the hardness of the PTFE composites were all improved, but the water absorption was increased with the increase of additives. The modification of nano-serpentine was successful and the thermal stability of PTFE composites was better. The lowest coefficient and minimum wear rate are 0.0267 and 8.67 × 10−5 · mm3 · (N · m)−1 respectively, which is 34.9% and 76% less than the pure PTFE.Originality/valueThe analysis showed that the wear mechanism of PTFE composites was abrasive wear and a small amount of adhesive wear, and when the additive content was appropriate, it easily formed a transfer film on the surface mating parts.

Simulation Analysis of Polyphenylene Sulfide Composite for Two-Folded Clip Panel by Using Aniform Software

Out of autoclave composite manufacturing is a process that achieves same quality as an autoclave process but through different method and one of them is thermoforming process in which, it can save the process cost and time. Recently, the fabrication process to fabricate thermoplastic composites by using thermoforming method becoming more popular among the thermoplastic research area. The simulation process is applied to enable the prediction of defects as well as to study the behavior of the process at early stage using simulation analysis to avoid trial and error during fabrication. To simulate the simulation, there are several factors and parameters need to be considered so that the defects could be avoided due to the excellent and poor formability will be linked between the fabricated samples in Aniform and the manufactured products. In this study, Two-Folded Clip panel mold type has been chosen to simulate the fabrication process. The results show the tensioner of AUY-50 is the best tensioner to be used in this research due to the significant of the result of press formed laminate quality with no voids appeared.

Effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame.

Mouthguard thickness is important to prevent oral and facial trauma during sports. The aim of this study was to establish an effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame. Mouthguards were thermoformed using 4.0-mm-thick ethylene vinyl acetate sheets and a vacuum forming machine. Each sheet was pinched at the top and bottom and stabilized by a circular frame. Two heating conditions were compared: (1) condition N, where the sheet was formed when it sagged 10mm below the level of the sheet frame at the top of the post, and (2) condition L, where the sheet frame was lowered 50mm below the ordinary level and heated, and the sheet was formed when it sagged 10mm. In each heating method, two forming conditions were compared: (1) when the sheet softened, the sheet frame was lowered and formed (condition C; N-C, L-C), and (2) after the sheet frame was lowered, the model was moved forward 20mm and then formed (condition MP; N-MP, L-MP). Six mouthguards were fabricated for each condition. Thickness differences due to heating conditions and forming conditions were analyzed by the two-way ANOVA and Bonferroni's multiple comparison test. At the incisal edge and at the labial and buccal surfaces, significant differences were observed among all conditions, and the thicknesses were in the order N-C < L-C < N-MP <L-MP. At the cusp, significant differences were not observed depending on the heating conditions. The thermoforming method with a circular sheet using a circular frame did not maintain a sufficient thickness only by the method of moving the model position just before formation. However, the results suggest that a single-layer mouthguard with a labial thickness of 3mm or more could be fabricated by applying the method of lowering the sheet frame and heating the sheet.

Development of Thermoplastic Composite Reinforced Ultra-High-Performance Concrete Panels for Impact Resistance.

In order to improve flexural and impact performance, thin panels of steel fiber-reinforced ultra-high performance concrete (UHPC) were further reinforced with external layers of continuous fiber-reinforced thermoplastic (CFRTP) composites. CFRTP sheets were bonded to 305 × 305 × 12 mm UHPC panels using two different techniques. First, unidirectional E-glass fiber-reinforced tapes of polyethylene terephthalate glycol-modified (PETG) were arranged in layers and fused to the UHPC panels through thermoforming. Second, E-glass fiber woven fabrics were placed on the panel faces and bonded by vacuum infusion with a methyl methacrylate (MAA) polymer. Specimens were cut into four 150 mm square panels for quasi-static and low-velocity impact testing in which loads were applied at the panel centers. Under quasi-static loading, both types of thermoplastic composite reinforcements led to a 150–180% increase in both peak load capacity and toughness. Impact performance was measured in terms of both residual deformation and change in specimen compliance, and CFRTP additions were reduced both by 80% to 95%, indicating an increase in damage resistance. While both reinforcement fabrication techniques provided added performance, the thermoforming method was preferable due to its simplicity and fewer specialized tool requirements.

Mechanical behaviour of 3D printed vs thermoformed clear dental aligner materials under non-linear compressive loading using FEM

Clear dental aligners are commonly manufactured using thermoplastic materials such as Duran and Durasoft. Using conventional thermoforming methods there are inherent disadvantages including time consumption and poor geometrical accuracies that often occur. The use of digital technologies and 3D printing techniques for producing dental aligners is often preferred where possible. Innovation in 3D printing has resulted in bio-compatible materials becoming more readily available, including Formlabs Dental LT Clear resin, which is a 3D printable and Class IIa bio-compatible material. In this paper, we investigate the difference between thermoplastic materials such as Scheu-Dental Duran and Durasoft and 3D printed Dental LT using Finite Element Analysis (FEA)/Finite Element Modelling (FEM) in a dental aligner case based on an analysis of von Mises stress distribution at molars, incisors and canines for a total of 33161 nodes using Finite Element Analysis (FEA). Maximum von Mises stress distribution at all of the sections under the action of non-linear compressive forces equivalent to human biting force (up to 600 N) were discovered to vary within a range of 0.2–7.7% for Dental LT resin. The Duran and Durasoft cases were comparable, thereby widening the scope for the use of Dental LT in various dentistry applications, including clear aligners.

Mouthguard Thermoforming Method to Decrease Palatal Thickness While Maintaining Labial and Buccal Thickness

Wearing a mouthguard reduces the risk of sports-related injuries, but a more comfortable design is required in order to increase the wearing rate. The aim of this study was to investigate a thermoforming method that decreases palatal thickness while maintaining labial and buccal thickness. Mouthguards were fabricated from an ethylene-vinyl acetate sheet (thickness: 4.0 mm) by using a vacuum forming machine. Four working models were prepared: 1) the anterior height was 25-mm and the posterior height was 20-mm (model A), 2) model A with the palate trimmed (model B), 3) heights 5 mm greater than model A (model C), and 4) model C with the palate trimmed (model D). The two forming conditions were as follows: 1) The sheet was formed when it sagged 15 mm below the level of the sheet frame at the top of the post under ordinary use (control); 2) The sheet frame at the top of the post was lowered and the sheet covered the model when it sagged by 15 mm. The rear side of the model was pushed to move the model forward 20 mm, and then the sheet was formed (MP). Differences in mouthguard thickness due to forming conditions and model forms were analyzed by two-way analysis of variance and Bonferroni’s multiple comparison tests. Difference in forming conditions was similar for all model forms; for the MP, the thickness of the incisal edge, labial surface, cusp and buccal surface were greater, and the palatal surface was thinner than the control. On the labial and buccal surface, the thickness difference due to the model form was observed only for the MP, and models A and B were thicker than models C and D. The palatal thickness tended to be thin in the models with the trimmed palate. This study suggested that the labial and buccal thickness of the mouthguard can be maintained, and the palatal thickness can be decreased by using the model with the palate trimmed with the forming method in which the model position is moved forward immediately before the vacuum formation.

Hot rolling behavior of graphene/Cu composites

Hot rolling is one of the most important thermoforming methods for metal matrix composites. However, to date, there are limited studies devoted to the research on the hot rolling behavior of graphene/metal composites. In this work, the influence of hot rolling on the evolution of microstructures, textures, and tensile properties of the graphene/Cu composites was systemically investigated. Firstly, this is done by comparing hot-rolled composites with different temperatures at 400 °C, 500 °C and 600 °C after 80% reduction. Interestingly, it was found that the graphene in the composite could be significantly exfoliated when rolling at 500 °C. Further texture analysis indicated that a strong component of shear deformation texture {001}<110> was formed. The exfoliation of the graphene can be explained by the presence of shear deformation and related mechanism was discussed. The composites with different rolling reductions (rolling at 500 °C) specifically revealed that the evolution of graphene gradually underwent three processes: 1. Aligned along rolling direction; 2. Broken into small pieces; 3. Exfoliated into thinned graphene. As a result, a high strength and good ductility composite can be realized. These findings provide new insights toward scalable and efficient fabricating of the graphene/metal composites with high performance.

Thermoformed fluoropolymer tubing for in-line mixing

We present a thermoforming method to make in-line micromixer in commercial fluoropolymer tubing.

Preparation, tribological properties and biocompatibility of fluorinated graphene/ultrahigh molecular weight polyethylene composite materials

Fluorinated graphene (FG)/ultra-high molecular weight polyethylene (UHMWPE) composites were successfully prepared by ultrasonic dispersion and liquid thermoforming method. The mechanical and tribological properties of pure UHMWPE and FG/UHMWPE composites were investigated using micro-hardness tester and high-speed reciprocating friction tester. The results showed that: adding FG could not only increase the micro-hardness of the composites, but also decrease the wear volume of the composite significantly. The friction coefficients of the composites were also reduced with the increasing of FG content. In addition, the MC3T3-E1 cells adhered and grew well on the surface of the FG/UHMWPE composites as observed by SEM and fluorescence microscope, indicating the addition of FG did not affect the morphology and activity of the cells. The FG/UHMWPE composites exhibited excellent mechanical properties, tribological properties and biocompatibility, which could be used as the potential artificial joint replacement material.

A Study of RTE Structural Packaging Design

Packaging plays an important role in decreasing the environmental impact and, simultaneously, improving well-being and safety of people. Due to a lack of time, ready-to-eat meal (RTE) offers more convenience choice to consumers than buying all ingredients and cooking at home. Thermoforming containers for RTE meals provides many packaging benefits such as protection and preservation, shelf life expansion, good appearance for display at point of purchase, convenience during transport and usage. However, thermoforming trays are made of plastic materials and are disposable packaging. This research project focuses on three parts: the study of the relationship between RTE food attributes and the structural packaging characteristics, the analysis of existing thermoforming structural design, and the synthesis of a new approach which takes the environmental impact into account for RTE packaging structures. The purposes of this research are (1) to investigate the technical design problems for these package’s structural characteristics by a thermoforming method, (2) to quantify the food packaging characteristics in relation to product attributes by using the perceptual mapping, as well as (3) to formulate a design guideline for the structural packaging characteristics which incorporates with the criterion of the environmental concern.

Thermoplastic elastomers for microfluidics: Towards a high-throughput fabrication method of multilayered microfluidic devices

Multilayer soft lithography of polydimethylsiloxane (PDMS) is a well-known method for the fabrication of complex fluidic functions. With advantages and drawbacks, this technique allows fabrication of valves, pumps and micro-mixers. However, the process is inadequate for industrial applications. Here, we report a rapid prototyping technique for the fabrication of multilayer microfluidic devices, using a different and promising class of polymers. Using styrenic thermoplastic elastomers (TPE), we demonstrate a rapid technique for the fabrication and assembly of pneumatically driven valves in a multilayer microfluidic device made completely from thermoplastics. This material solution is transparent, biocompatible and as flexible as PDMS, and has high throughput thermoforming processing characteristics. We established a proof of principle for valving and mixing with three different grades of TPE using an SU-8 master mold. Specific viscoelastic properties of each grade allow us to report enhanced bonding capabilities from room temperature bonding to free pressure thermally assisted bonding. In terms of microfabrication, beyond classically embossing means, we demonstrate a high-throughput thermoforming method, where TPE molding experiments have been carried out without applied pressure and vacuum assistance within an overall cycle time of 180 s. The quality of the obtained thermoplastic systems show robust behavior and an opening/closing frequency of 5 Hz.

Shape retention in porcine and rabbit nasal septal cartilage using saline bath immersion and Nd:YAG laser irradiation

The process of altering the shape of cartilage using heat has been referred to as thermoforming, and presents certain clinical benefits in reconstructive surgical procedures within the head and neck. Thermoforming allows cartilage in the upper airway and face to be reshaped without the use of classic surgical maneuvers such as carving, morselizing, or suturing. The goal of this study was to determine the dependence of cartilage shape change on both temperature and laser dosimetry using two thermoforming methods: saline bath immersion and laser irradiation. Ex-vivo rabbit and porcine nasal septal cartilages were mechanically deformed and reshaped using the two thermoforming methods. With saline bath immersion using rabbit cartilage, each specimen was deformed by securing it to a small copper tube (outer diameter 8 mm) using dental bands. For porcine cartilage immersed in a saline bath, each sample was mechanically deformed between two pieces of wire mesh attached to a semicircular acrylic block. With both porcine and rabbit cartilage, the specimen and apparatus were then immersed in a hot saline bath for time intervals varying from 20 and 320 seconds and at constant temperatures between 62 and 74 degrees C. In laser reshaping, the cartilage specimens were mechanically deformed on a jig and consecutively irradiated with an Nd:YAG laser (lambda = 1.32 microm) in several spots for 6-16 seconds and irradiances of 10.2-40.7 W/cm2 per spot. After either saline bath heating or irradiation, cartilage specimens were immersed in room temperature saline for 15 minutes, then upon removal from the jig the length between the ends of each specimen was measured in order to calculate the resulting bend angle. The transition zone for cartilage reshaping was defined as where a significant increase in bend angle was observed between consecutive times of immersion/irradiation at the same temperature/irradiance. For the saline bath experiments, the transition zone was observed between 59-68 degrees C and 62-68 degrees C for porcine and rabbit cartilage, respectively. Similar transition zones occurred with laser irradiation below irradiances of 20.4 W/cm2 for both porcine and rabbit cartilage. In addition, the dosimetry pairs in the transition zones produce peak temperatures below the thresholds determined from the saline bath immersion studies. The critical transition temperature region was determined by the sharp increase in bend angle at consecutive times of immersion at the same temperature. This range was determined to be 59-68 degrees C and 62-68 degrees C for porcine and rabbit cartilage, respectively. Similar transition zones for dosimetry occurred below 20.4 W/cm2 during cartilage irradiation in both species.

Oxygen barrier properties of thermoformed trays manufactured with different drawing methods and drawing depths

AbstractA comparison was made of oxygen barrier properties and wall thickness distribution of different thermoformed trays. The thermoformed trays were manufactured with three drawing depths and two different thermoforming methods; with and without plug‐assist. Four different polymer combinations were evaluated. The oxygen transmission rate (OTR) [cm3/(package/day)] was measured at three conditions (23°C/50% relative humidity (RH) with 0% RH inside, 6°C/80% RH with 0% RH inside, and 6°C/80% RH with 100% RH inside. Wall thickness was measured at five different positions in the trays. In general, temperature had more influence on the oxygen transmission rate (OTR) than the humidity. The OTR in the packages increased with increasing drawing depth, but the increase was not linear. Other effects besides thinning, such as orientation, may have influenced the OTR, since the relationship between OTR, given as cm3/(m2/day), and the drawing depth was not linear. Plug‐assisted thermoforming only had an effect on the OTR in trays with 70 mm drawing depth made of 600 µm thick laminate of PP/PE, which was probably due to exceeding the maximum drawing depth of this material. There was no correlation between the OTR value in the packages and the wall thickness in either of the positions, but a quite high correlation between the drawing depth and the relative wall thickness in all measured positions was observed. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Stamp Thermo-Hydroforming: A New Method for Processing Fiber-Reinforced Thermoplastic Composite Sheets

The stamp thermo-hydroforming process involves supporting the thermoplastic sheet with a bed of heated viscous fluid that applies a hydrostatic pressure across the part throughout the forming process. This hydrostatic pressure produces a through-thickness compressive stress that delays the onset of delamination, reduces the formation of wrinkles due to frictional traction forces, and results in better-formed parts. The overall goal of this research is to verify, through experimentation and numerical modeling, that the stamp thermo-hydroforming process provides a suitable alternative to conventional thermoforming methods, such as bag molding and stamp forming, as a means for processing glass-mat fiber-reinforced thermoplastic materials. The goal of this paper is to solely address whether the use of a counteracting pressure can be beneficial during the forming of fiber-reinforced thermoplastic sheets more specifically; this paper addresses the experimental setup that was developed and built to conduct small-scale stamp thermo-hydroforming experiments with a hemispherical punch, and discusses some results obtained using this setup. Experiments were performed on a random oriented continuous glass-mat fiber-reinforced polypropylene with hydrostatic pressure applied locally on the top surface of the composite sheet, as it was being stretched by a hemispherical punch. An increase of up to 10% in draw depth was achieved by applying local hydrostatic pressures up to 207 kPa (30 psi). In addition to the draw depth improvements, the application of the counteracting hydrostatic pressure also delayed the onset of delamination.

Thermoforming of liquid crystalline polymer sheets

AbstractLiquid crystalline polymer (LCP) extruded sheets were further processed by the conventional thermoforming method. The available processing temperature range was defined through the structural, thermal, and elevated temperature mechanical characterization of the extruded sheet. This temperature range was found for LCP to be quite narrow, in the proximity of the crystal‐mesophase transition. The structural changes imposed on the LCP sheet during forming and its thermal stability were investigated using wide angle X‐ray diffraction, mainly for the determination of the chain orientation distribution, DSC, and dynamic mechanical analysis. Thermoforming onto a symmetrical male mold was found to enhance the orientation in the extrusion machine direction and even change the preferred orientation in the extrusion transverse direction to orientation along the thermoforming direction. Annealing at the thermoforming temperature range results in a more ordered and thermally stable structure accompanied by just a slight orientation loss.

Investigating the Thermoformability of Uhmw-Polyethylene

The formability of UHMW-polyethylene is examined by combining the concept of uniaxial testing at various temperatures at constant rate or constant load with a standardizable thermoforming method that employs molds with variable geometry. Preliminary results analyze and define processing parameters such as: heating time, vacuum pressure, and draw ratio, among others. Finished material properties of the resultant thermoformed parts are presented.