Silicone Rubber Mold Research Articles

A Cost-Effective Approach to Creating Large Silicone Rubber Molds Using Advanced Rigid Polyurethane Foam.

In practical applications, polyurethane (PU) foam must be rigid to meet the demands of various industries and provide comfort and protection in everyday life. PU foam components are extensively used in structural foam, thermal insulation, decorative panels, packaging, imitation wood, and floral foam, as well as in models and prototypes. Conventional technology for producing PU foam parts often leads to defects such as deformation, short shots, entrapped air, warpage, flash, micro-bubbles, weld lines, and voids. Therefore, the development of rigid PU foam parts has become a crucial research focus in the industry. This study proposes an innovative manufacturing process for producing rigid PU foam parts using silicone rubber molds (SRMs). The deformation of the silicone rubber mold can be predicted based on its wall thickness, following a trend equation with a correlation coefficient of 0.9951. The volume of the PU foam part can also be predicted by the weight of the PU foaming agent, as indicated by a trend equation with a correlation coefficient of 0.9824. The optimal weight ratio of the foaming agent to water, yielding the highest surface hardness, was found to be 5:1. The surface hardness of the PU foam part can also be predicted based on the weight of the water used, according to a proposed prediction equation with a correlation coefficient of 0.7517. The average surface hardness of the fabricated PU foam part has a Shore O hardness value of approximately 75. Foam parts made with 1.5 g of water added to 15 g of a foaming agent have the fewest internal pores, resulting in the densest interior. PU foam parts exhibit excellent mechanical properties when 3 g of water is added to the PU foaming agent, as evidenced by their surface hardness and compressive strength. Using rigid PU foam parts as a backing material in the proposed method can reduce rapid tool production costs by about 62%. Finally, an innovative manufacturing process for creating large SRMs using rigid PU foam parts as backing material is demonstrated.

Development of a Silicone Rubber Mold with an Innovative Waterfall Cooling Channel.

A conformal cooling channel (CCC) follows the mold core or cavity profile to carry out uniform cooling in the cooling stage. However, the significant pressure drop along the cooling channels is a distinct disadvantage of the CCC. In this study, an innovative waterfall cooling channel (WCC) was proposed and implemented. The WCC cools the injected products via surface contact, replacing the conventional line contact to cool the injected products. The WCC was optimized using numerical simulation software. Silicone rubber molds with two kinds of cooling channels were designed and implemented. The cooling time of the molded part was evaluated using a low-pressure wax injection molding machine. The experimental results of the cooling time of the molded part were compared with the simulation results from numerical simulation software. The results showed that the optimal mesh element count was about 1,550,000 with a mesh size of 1 mm. The simulation software predicted the filling time of the water cup injection-molded product to be approximately 2.008 s. The cooling efficiency for a silicone rubber mold with a WCC is better than that of the silicone rubber mold with a CCC since the core and cavity cooling efficiency is close to 50%. The pressure drop of the WCC is smaller than that of the CCC, which reduces the pressure drop by about 56%. Taking a water cup with a mouth diameter of 70 mm, a height of 60 mm, and a thickness of 2 mm as an example, the experimental results confirmed that the use of the WCC can save the cooling time of the product by about 265 s compared with the CCC. This shows how a WCC can increase cooling efficiency by approximately 17.47%.

COMPARISON OF FLEXURAL PROPERTIES OF PINEWOOD WITH FEA SIMULATION FOR MARINE APPLICATION

Pine wood sourced from pellet packaging, being abundant, holds potential for utilization in creating bio composites, particularly as activated carbon for laminated coatings in structural applications. However, there is a current lack of research identifying its specific properties as a coating material for Fiber Reinforced Polymer (FRP) composites. Fiber Reinforced Polymer (FRP) composites provide a highly adaptable solution for reinforcing and revitalizing existing structures in challenging marine conditions. This study delves into investigating the flexural characteristics of FRP pine wood composites, comparing the findings with Finite Element Analysis (FEA) results. Furthermore, the activated carbon derived from pine wood exhibits potential for resisting barnacle attachment when immersed in saltwater. For the flexural analysis, samples were produced using a silicone rubber mold, incorporating varying weight percentages (wt.%) of activated FRP pine wood, ranging from 2 wt.% to 10 wt.%. The outcomes of the study reveal that the introduction of activated carbon from pine wood leads to an enhancement in ultimate strength, reaching a maximum of 2700 MPa. Nonetheless, the results also indicate a reduction in material strength as the proportion of activated carbon pine wood is increased.

Rapid tooling of composite aluminium filled epoxy mould for injection moulding of polypropylene parts with small protruded features

Abstract Rapid tooling evolved from rapid prototyping is a novel method for developing prototype tooling rapidly using various additive manufacturing techniques. Traditional injection moulding is unsuitable for low-volume production because of the high initial cost. This study is focused on a rapid tooling approach for producing an injection mould insert for the low-volume production of plastic components. A plastic injection mould insert is designed, developed using composite aluminium filled epoxy with minute protruded features and tested on a vertical injection moulding machine as a rapid tool for low-volume production of plastic components. The composite aluminium filled epoxy (CAFE) mould insert is prepared using a wax master from silicon rubber mould prepared using a stereolithography master. Experiments are performed to determine the optimum mixing ratio of epoxy: aluminium powder for making the composite aluminium filled epoxy injection mould. The mould insert prepared was tested for the injection of polypropylene components on a vertical injection moulding machine and analyzed for dimensional accuracy. The analysis of dimensional accuracy and viability of minute features on the injected parts shows promising results for up to 30 injected parts. The injection of parts after 30 pieces resulted in increasing mould erosion and pitting, causing mould damage at the 36th injection shot. The experimental finding supports the feasibility of using the composite aluminium filled epoxy injection mould for low-volume production of the parts; however, the surface finish is inferior. The life of the mould is expected to give better results with a higher surface finish. It is also exposed that using mould release agents improves the life of the composite aluminium-filled epoxy injection mould.

Optimization of removal process parameters of polyvinyl butyral cooling channel in rapid silicone rubber molds using the Taguchi method

Optimization of removal process parameters of polyvinyl butyral cooling channel in rapid silicone rubber molds using the Taguchi method

Influence of home bleaching regimen on microhardness and flexural strength of two contemporary composite resins - an in vitro evaluation.

This study was to compare and evaluate the effect of home bleaching on the microhardness and flexural strength of microhybrid and nanohybrid composite resins. The study samples were prepared using a custom-made silicon rubber mold. For microhardness evaluation, 40 disc-shaped specimens (4mm*2mm) were prepared and divided into 4 groups: GROUP A (n=10): microhybrid (GC Solaire X, GC Corporation) control group, GROUP B (n=10) nanohybrid (Tetric N Ceram, Ivoclar Vivadent) control group, GROUP C (n=10): microhybrid bleaching group, GROUP D (n=10) nanohybrid bleaching group. For flexural strength evaluation, 40 bar shaped specimens (25mm*2mm*2mm) were prepared. They were divided into 4 groups, GROUP 1 (n=10): microhybrid control group, GROUP 2 (n=10) nanohybrid control group, GROUP 3 (n=10): microhybrid bleaching group, GROUP 4(n=10) nanohybrid bleaching group. All the control groups were placed in artificial saliva and bleaching groups were exposed to home bleaching agent for 14 days according to manufacturer's instructions. The microhardness and flexural strength were evaluated for the respective specimens after 14 days and the data were statistically analyzed. Home bleaching regimen decreased microhardness of both microhybrid and nanohybrid composites whereas there was no significant effect on the flexural strength. Nanohybrid composites showed greater microhardness values before and after bleaching. Bleaching agents, irrespective of their concentration can decrease the microhardness of the composite resin samples, which raises a concern about replacement of these restorations due to the effects on physical and mechanical properties.

PMMA Cranioplasty Making by Using Open-Source CAD Software, PLA Printers, and Silicone Rubber Molds: Technical Note with Two Illustrative Cases.

We read with great interest Malikov et al's case report/technical note entitled “PMMA cranioplasty making by using open-source CAD software, PLA printers, and silicone rubber molds: technical note with two illustrative cases.”[1] We were the first in the literature to begin an ultra-low-cost patient-specific polymethyl methacrylate (PMMA) cranioplasty implant service in Pakistan, that too in a public sector hospital, and we have already published our technical note and limited case series with 1-year follow-up.[2] Since then, our technique has been adopted by our colleagues at neighboring centers, and we have amassed an experience of over 50 cases, and many of our patients are in long-term follow-up. At the national level, the lowest cost offered by commercial companies for a patient-specific PMMA implant exceeded US$ 1,000 and US$ 10,000 for titanium and polyetheretherketone (PEEK) hemicraniectomy implants, respectively. The vast majority of the Pakistani population are poor and underprivileged, and the trauma cohort who require this operation are actually those who could never meet these costs in their lifetime. Free-hand PMMA cranioplasty was utilized in virtually all cases nationally. After beginning our initial service, the total cost to manufacture an implant in consumables was US$ 40. The printer we used was a locally assembled Chinese Prusa i3 clone. Thus, production cost was exponentially cheaper than commercial rates, and in our experience, our clinical and aesthetic outcomes are the same, if not better. Naturally, when one intends to offer a service for the patient benefit rather than profit, affordability is one of the most important parameters, especially in the impoverished developing world. We would be delighted to know the exact specification of the printer used by Malikov et al, the cost of disposables and printing of each implant, and the context of this cost in their patient's socioeconomic demographic/health care system, and whether commercial options were as extortionate for their general public as it was for ours.

Porto Primavera Ichnofossil Geosite, Brazil: Geoconservation Measures in a Protected Area

Porto Primavera geosite comprises aeolian sandstones with tetrapod trace fossil cropping out at the Porto Primavera Hydroelectric Power Plant, São Paulo State, Brazil. The Upper Cretaceous Rio Paraná Formation, which contains these tracks, is composed of medium–fine quartzarenites well- sorted and supermature, with typically large tabular/trough cross-bedding. They accumulated in complexes of large barchanoid dunes, moved by winds to the south-west. The Porto Primavera association consists of tracks of theropod dinosaurs and small mammals preserved in concave epirelief. These rare records in aeolian desert environments from the Late Cretaceous of Brazil indicate that even the interior Caiuá desert was occupied by organisms. The study focused on the characterization of the ichnofossils, assessing their susceptibility to degradation by natural and anthropogenic processes, and proposing measures to manage the geosite. Because the risk of degradation of the geosite is high, it is proposed that prior to their removal the slabs should be replaced with synthetic resin replicas made using silicone rubber moulds. The sense of disconnection between the objects and their natural geological context could be addressed by depositing the objects near the geosite in the Museum of Regional Memory. The geosite is indicated as a new holostratotype to the Rio Paraná Formation.

Comment on ‘optimum structural design of CFRP isogrid cylindrical shell using genetic algorithm’

We comment on the paper published by Sakata et al., in J. Adv. Compos. Mater., 2018, 27, 35–51, which was in continuation of the previous work by Sakata and Ben in J. Adv. Compos. Mater., 2012, 21, 445–457. Although the experimental section in both works were identical, the reported numerical values of the linear buckling loads differed. In addition, all the specimens were manufactured using an identical process by employing silicone rubber mold and filament winding technique, and outer skin layers and stiffeners consisted of a fixed number of plies. Nonetheless, different shell thicknesses and stiffeners cross-sectional areas were reported for the specimens. Since the buckling behavior of cylindrical shells is highly sensitive to their thickness, the difference in the reported numerical linear buckling loads of the mentioned studies could be due to different thickness values used as inputs for their numerical analyses. In order to address this subject, the present study aimed to provide complete and comprehensive data on the buckling behavior of unstiffened and grid-stiffened cylindrical shells with the same material properties and geometrical dimensions but various thicknesses. The presented results can be used as a benchmark for future studies.

Toward Efficient Wound Management: Bioinspired Microfluidic and Microneedle Patch.

Microneedle (MN) patches hold demonstrated prospects in intelligent wound management. Herein, inspired by the highly folded structure of insect wings, a three-dimensional (3D) origami MN patch with superfine miniature needle structures, microfluidic channels, and multiple functions wasreported to detect biomarkers, release drugs controllably and monitor motions to facilitate wound healing. By simply replicating the pre-stretched silicone rubber (Ecoflex) molds patterned by a laser engraving machine, the superfine structure MN patch with microfluidic channels wasobtained from the restored molds. The bioinspired origami structure endows the MN patch with a high degree of functional integration, including microfluidic channels and electrocircuits. The microfluidic channels combined with the pH value and glucose concentration indicators enable the patch with the capability of biomarker sensing detection. Porous structures, a temperature-responsive hydrogel, and a photothermal-sensitive agent are utilized to form a controllable drug release system on the MN patch. Meanwhile, MXene electrocircuits wereprinted on the MN patch for motion sensing. In addition, the ability of the MN patch to accelerate wound healing wasdemonstrated by a mouse model experiment with full-thickness skin wounds. These results indicate that the multifunctional 3D origami MN patch is a valuable intelligent strategy for wound management.

The Effect Of Potassium Permanganate On Betung Bamboo (Dendrocalamus Asper) Epoxy Fiber Compositesusing Hand Lay Up Method

The application of natural fiber composites in the modern world is often overlooked due to the rise of new synthetic fibers. The BetungBamboo is one type of natural fiber that has been used for many generations in the Indonesian archipelago. The fiber can be used to produce composites, however the choice of matrix and fiber treatment has an effect on determining the strength properties of the composite. In this study using epoxy resin as a matrix and Betung Bamboo fiber as a filler. Permanganate treatment of Betung bamboo fiber was conducted using KMnO4 solution. With variations in KMnO4 concentrations of 3%, 5%, and 7% for 15 minutes of immersion. The fabrication was carried out by hand lay-up method with silicone rubber molds. Tensile tests are then carried out to determine the tensile strength of the composite. Digital microscopy was observed to see the fracture pattern of the composite. The initial hypothesis of this study was the treatment of KMnO4 solution which aims to improve the interfacial properties of strength and resistance of Betung bamboo fiber and matrix, so that the mechanical properties of the composite are stronger. The highest tensile strength was at 5% KMnO4 content of 33.55 MPa and the lowest was at the specimen without KMnO4 content of 28.06 MPa. The highest strain was on specimens without KMnO4 content with 2.645% and the lowest on 7% KMnO4 content with 1.513%. The highest elastic modulus value was at 7% KMnO4 content of 20.84 MPa and the lowest was for specimens without KMnO4 content of 10.6 MPa. In the tensile test specimen without KMnO4 content, there are pullout fracture patterns, and in the tensile test specimen with 5% KMnO4 content there are indications of overload fracture pattern.

Methodological analysis of composites Green Polyurethane Resin reinforced with jute fabric

Currently, the scientific community is focusing to develop news materials that shall be environmentally friendly; this mindset is growing and leading to a huge increase in new papers on that effort. The main idea in our research field is to discover new eco-friendly composites that can replace some synthetic originated or non-renewable sources. For this, the castor oil based polyurethane matrix represents an ecologically correct option for the use of polymeric matrices. Moreover, the use of natural fibers instead of synthetic ones makes an even greener composite. This research sought to analyze vegetable polyurethane resin from castor oil as matrix reinforced by jute fabric. The fabric apparent density was determined by Archimedes method, obtaining a value of 2.4 g/cm3. Subsequently, samples of the composite were made in open silicone rubber mold for the charpy impact test and compared with specimens made in a closed metallic mold under pressure. The composites received 0–6 layers of jute fabric. As a result, the better impact resistance was with open mold reached a notch resistance of 226.34 J/m for 2-layer composites. In addition, the values of 3–6 layers in open mold were significantly better than those of closed molds, varying from 20 % up to 174 % better. The pressing step in a closed mold is not necessary; consequently, we saved money and time to manufacture this type of composites, for these purposes.

PMMA Cranioplasty Making by Using Open Source CAD Softwares, PLA Printers and Silicone Rubber Molds: Technical Note with 2 Illustrative Cases

In this technical report, we talk about the design and producing of PMMA implants, which we successfully applied in two patients using silicone molds, and retrospective review of these patients at the 1 and 6 months intervals. By using open source CAD softwares, 3D printers and the patient's thin sliced computed tomography (CT) data, we designed and produced the implant template and used it to make silicone rubber mоlds for intraoperative PMMA casting with good results. As a negative of the implant we created a silicon mold, which can be autoclaved.

Properties of kenaf/textile waste fibre hybridisation in a carbon nanotubes modified matrix

AbstractTextile waste is part of the solid waste that should be disposed of due to environmental concerns. Thus, the textile waste composite was proposed as one solution to minimise this problem. However, the properties of the composite produced is one of the issues to tackle to produce high‐quality composite materials. Fibre hybridisation and nanofiller addition have been proved to enhance the properties of polymer composites. Therefore, hybridising textile waste with kenaf fibres was expected to improve the composite‘s mechanical properties as kenaf fibres have been extensively accepted due to their flexural and tensile strength capabilities. While incorporating carbon nanotubes should enhance the properties of a matrix system. This research aims to analyse the effect of fibre hybridisation and matrix modification on the mechanical properties of kenaf/textile waste composites. The specimens were fabricated using a casting method in a silicon rubber mould. The results show that the hybrid composite had improved tensile, compressive, and impact strength up to 28.57 %, 39.15 %, and 16.33 %, respectively, compared to textile waste composites. Meanwhile, incorporating 1.0 wt. % carbon nanotubes in hybrid composite specimens improved the compressive modulus and impact strength by 108 % and 48.95 % compared to hybrid textile waste composites.

Asphalt Binder Testing at Low Temperature: Three-Point Bending Beam Test in Dynamic Shear Rheometer

A novel Three-Point Bending Beam Test (3-PBT) using a Dynamic Shear Rheometer (DSR) with linear drive motor is introduced for testing asphalt binder at low temperature conditions. This 3-PBT in DSR can be used as surrogate for Bending Beam Rheometer (BBR) tests. Advantages in comparison to BBR are that (i) 3-PBT works without harmful cooling medium ethanol, (ii) the amount of asphalt binder for testing is significantly lower (using material equivalent of 10% of BBR tests), (iii) a silicone rubber mold is used for specimen preparation instead of standard aluminum mold for BBR tests, which makes handling easier, and (iv) the loading protocol is more practical without applying contact load manually. The novel 3-PBT in DSR is presented with respect to preparation, installation, and conditioning of specimens, as well as to the loading protocol. Tests were conducted at temperatures of −10, −16, and −20°C. For the purpose of comparison to BBR tests, and of identifying most suitable testing conditions from alternative setups, a test series was run including 9 different asphalt binders. As to BBR tests, two different cooling media were used, i.e., ethanol and air. Finally, all test results obtained from DSR and BBR tests were analyzed in view of precision and correlation. DSR results correlated well with BBR results, while precision of 3-PBT in DSR was found to be satisfying.

Study on Aqueous Humour Hydrodynamics of Glaucoma Condition Using 3D Printed Model and Particle Image Velocimetry (PIV)

This study aims to explore the knowledge on fluid flow properties of the aqueous humour (AH), specifically on the anterior segment (AS) of the human eye for a medical condition called Glaucoma. The research objectives are to study on fluid flow characteristics of velocity and pressure of the AH on the AS of the eye using enlarged 3D printed model and computational analysis, and also to analyse the suitability of the 3D generated anterior AS in fluid flow analysis application on particle image velocimetry (PIV). Using polyvinyl alcohol (PVA) as a water-soluble 3D printing filament, a 3D model of the AS of the human eye was generated with SolidWorks 2018 and printed using Creality Ender 3. This printed model serves as the pattern for silicon rubber mould production using vacuum casting process. Analysis of AH flow hydrodynamics are conducted with computational analysis using ANSYS Workbench 19.2. Key findings support that use of PVA material suite the creation of specific shapes and patterns for 3D modelling applications alike, and silicon rubber moulding creates a non-reactive and long-lasting mould for PIV applications. Computational analysis findings support the use of the generated model for PIV applications. Overall, the study successfully supports the use of 3D printed model for PIV application and future work that can be induced include direct experimentation of the mould with PIV.

Characterizations of Polymer Gears Fabricated by Differential Pressure Vacuum Casting and Fused Deposition Modeling.

In recent years, polymer gears have gradually become more widely employed in medium or heavy-duty conditions based on weight reduction in transmission systems because of low costs and low noise compared to metal gears. In the current industry, proposing a cost-effective approach to the manufacture of polymer gears is an important research issue. This paper investigates the wear performance of polymer gears fabricated with eight different kinds of materials using differential pressure vacuum casting and additive manufacturing techniques. It was found that both additive manufacturing and differential pressure vacuum casting seem to be an effective and cost-effective method for low-volume production of polymer gears for industrial applications. The gate number of one is the optimal design to manufacture a silicone rubber mold for differential pressure vacuum casting since the weld line of the polymer is only one. Polyurethane resin, 10 wt.% glass fiber-reinforced polylatic acid (PLA), or 10 wt.% carbon fiber-reinforced PLA are suggested for manufacturing gears for small quantity demand based on the deformation and abrasion weight percentage under process conditions of 3000 rpm for 120 min; epoxy resin is not suitable for making gears because part of the teeth will be broken during abrasion testing.

Personalized and Programmable Microneedle Dressing for Promoting Wound Healing.

Microneedle (MN) dressings, with the ability of transdermal drug delivery, have played an essential role in the field of wound healing. However, patients may still feel uncomfortable when sensitive unhealing wounds are pieced by strong needles. Here, inspired by the structure of mosquito mouthparts, which possess a fixation part and a liquid-transferring part, we present a novel MN wound dressing with superfine needle tips, personalized pattern design, programmable needle length, and multiple mechanical strengths for intelligent and painless drug delivery. By simply stretching the silicone rubber (Ecoflex) molds before engraving, superfine MNs can be formed in the restored molds. Meanwhile, by utilizing intelligent image recognition, precise treatment for irregular wounds is achieved. Notably, combined with temperature-responsive N-isopropylacrylamide (NIPAM) hydrogel and inverse opal (IO) photonic crystals (PCs), a controllable drug release system has been achieved on MN dressings. Moreover, the performance of the MN dressing in facilitating wound recovery has been demonstrated by full-thickness skin wounds of a mouse model. These results indicate that novel personalized and programmable MN wound dressings are of considerable value in the field of wound management.

Effects of cooling channel layout on the cooling performance of rapid injection mold

Conformal cooling channels (CCCs) are a cooling passageway which follows the profile of the mold cavity or core to perform uniform cooling process effectively in the injection molding process. The production cost is closely related to productivity. To further improve productivity, the injection mold was equipped with CCCs to shorten the cooling time of the injection molded part. To investigate the relationship between the cooling channel layout and cooling efficiency of the CCCs, silicone rubber molds (SRMs) with different layouts of cooling systems were designed and constructed in this study. Simulation software was utilized to study the cooling performance. To verify the results of the simulation, SRM with different cooling systems were fabricated for low-pressure wax injection molding. It was found that the cooling time of the injection molded part is indeed affected by the total surface area of the heat exchange between the coolant and the SRM. The cooling system with four inlets and four outlets seems to be the optimum layout of the SRM in the case study in terms of the difficulty of mold making, total surface area of the heat exchange between the coolant and the SRM, and total cooling flow length of each segment. The saving in the cooling time about 2796 s and improvement of cooling efficiency about 76% can be obtained when the SRM with four inlets and four outlets was used for injection molding. The findings in this study can be used as a reference to design CCCs of injection mold built with AM technology.

Improving Cooling Performance of Injection Molding Tool with Conformal Cooling Channel by Adding Hybrid Fillers.

Silicone rubber mold (SRM) is capable of reducing the cost and time in a new product development phase and has many applications for the pilot runs. Unfortunately, the SRM after injection molding has a poor cooling efficiency due to its low thermal conductivity. To improve the cooling efficiency, the thermal conductivity of the SRM was improved by adding fillers into the SRM. An optimal recipe for fabricating a high cooling efficiency low-pressure injection mold with conformal cooling channel fabricated by fused deposition modeling technology was proposed and implemented. This study proposes a recipe combining 52.6 wt.% aluminum powder, 5.3 wt.% graphite powder, and 42.1 wt.% liquid silicon rubber can be used to make SRM with excellent cooling efficiency. The price–performance ratio of this SRM made by the proposed recipe is around 55. The thermal conductivity of the SRM made by the proposed recipe can be increased by up to 77.6% compared with convention SRM. In addition, the actual cooling time of the injection molded product can be shortened up to 69.1% compared with the conventional SRM. The actual cooling time obtained by the experiment is in good agreement with the simulation results with the relative error rate about 20%.