Liquid Resin Research Articles

A novel dry processing technique to construct a high-performance superfine diamond grinding wheel with thermal and material characterizations

A novel dry process that prepared in mixing with a pore-forming agent employs a single batch process in production of grinding wheels with the advantage without using resin liquid as an additive binder. The agglomeration of a pore-forming agent can be avoided due to no dressing agent mixing with the superfine diamond abrasives and binders. Bulk mass production can still ensure to fulfill the excellent homogeneity in mixing cross the entire grinding wheel. Therefore, an uneven mixing caused by mixing errors and human factors can be minimized. The grinding wheel can reach an ultrahigh porosity (~82 %) at a lower sintering temperature of 620 °C. Low-temperature sintering can effectively reduce the carbon footprint. A thermogravimetric-differential scanning calorimeter (TG-DSC) was used to determine the thermal properties of superfine frits. Further characterization of ultrafine binders by an optical non-contact dilatometry is utilized to set-up a protocol sintering plan of grinding wheels. Microstructure from scanning electron microscope (SEM) measurement on grinding wheel presents a uniform large pore structure which offers a benefit to wafer surface removal and less scorching during grinding. Atomic force microscopy (AFM), laser scanning digital microscope (LSCM) and SEM results revealed that the ground silicon (Si) wafer had a low surface roughness (~6 nm), without deep scratches, and with a low damaged layer (~0.7 μm) respectively. The wear test on grinding wheels demonstrates it is very cost effective to use a dry processing wheel. This work provides a new method for grinding Si wafers with a new type of wheel being developed by a novel dry superfine diamond grinding technique in a manufacturing process. It is realized that the use of a dry grinding process can save part of chemical polishing process (CMP) and effectively reduces the polishing time.

Thermal analysis and shrinkage characterization of the photopolymers for DLP additive manufacturing processes

This paper proposes an experimental investigation of a commercial photopolymer resin followed by material modelling and manufacturing system characterization. We focus on the effect of the degree of cure and temperature on the material properties of the photopolymer materials. UV curing properties of the liquid resin are assessed with the thickness measurement by optical tomography. Besides, the specific heat capacity is determined for the almost completely cured and uncured samples with DSC measurements. Photo-DSC experiments are performed to investigate the curing reaction and modelling of the evolution of the degree of cure depending on the light intensity and temperature. In addition, chemical shrinkage behaviour is captured as function of the degree of cure by the high-precision balance set-up. As a result of our experimental studies, model equations are proposed to describe the material behaviour.

The effects of binder type combined with graphite content and the presence of aluminum on the characteristics of MgO–C bricks

In this paper, a systematic study regarding the combined effects of critical variations in MgO–C brick compositions, such as the graphite content (varied in 8 and 12 wt%) and the presence of aluminium (2 wt%), are analysed together with the use of a solid soft-binder (or ecobinder) mixed with a liquid phenolic resin. The bricks have controlled compositions and were manufactured in-plant using the current procedure for commercial-product bricks; the obtained results are compared with those from bricks with the same composition but bonded with the resin alone. The presence of aluminium produces opposite effects in the physical characteristics, such as the bricks' particle size distribution and pore volume when the mixed system or just the resin is employed as the binder. As expected, the resin-based bricks possess greater stiffness and mechanical strength (at RT) than those bonded with the addition of the soft-binder. However, contrary to our expectations, the presence of the soft-binder does not improve oxidation resistance at 1400 °C. On the other hand, the impact of the graphite content on the mechanical behaviour (at RT) is higher than the presence of aluminium for any of the binder type (resin alone or mixed with the ecobinder), but the contrary is observed for the brick's oxidation resistance.

Instant flow distribution network optimization in liquid composite molding using deep reinforcement learning

Carbon fibre reinforced plastic (CFRP) manufacturing cycle time is a major driver of production rate and cost for aerospace manufacturers. In vacuum assisted resin transfer molding (VARTM) where liquid thermoset resin is infused into dry carbon reinforcement under vacuum pressure, the design of a resin distribution network to minimize fill time while ensuring the preform is completely full of resin is critical to achieving acceptable quality and cycle time. Complex resin distribution networks in aerospace composites increase the need for quick, optimized virtual design feedback. Framing the problem flow media placement in terms of reinforcement learning, we train a deep neural network agent using a 3D Finite Element based process model of resin flow in dry carbon preforms. Our agent learns to place flow media on thin laminates in order to avoid resin starvation and reduce total infusion time. Due to the knowledge the agent has gained during training on a variety of thin laminate geometries, when presented with a new thin laminate geometry it is able to propose a good flow media layout in less than a second. On a realistic aerospace part with a complex 12-dimensional flow media network, we demonstrate our method reduces fill time by 32% when compared to an expert designed placement, while maintaining the same fill quality.

High-performance medical-grade resin radically reinforced with cellulose nanofibers for 3D printing

The effect of Cellulose NanoFiber (CNF) addition to a medical-grade resin in Stereolithography (SLA) Additive Manufacturing (AM) technology is reported, aiming to elaborate an easily processable, highly stiff bio-compound. CNFs were shear stir blended at various weight ratios with liquid resin. The fabricated nanocomposite materials were introduced in an SLA 3D printer for specimens manufacturing. The mechanical performance was studied according to international standards. Charpy Toughness and Vickers microhardness were calculated for all tested materials. A microscopic and surface analysis was conducted on fractured tensile specimens by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), respectively. The thermal and thermomechanical properties were investigated by Thermogravimetric Analysis (TGA), Differential Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA). Significant reinforcement of the medical-grade nanocomposites is reported, with the highest values calculated to be at 1.0 wt% concentration (more than 100% at the tensile strength), while brittleness and rigidity were increased.

Tensile strength of reinforced laminates after oblique ballistic impact: An experimental study

The present study endeavoured to examine the tensile strength of the laminates, which were made of carbon/Kevlar hybrid reinforced fibre with carbon nanotubes (CNTs) post oblique impacts. Although a number of experimental investigations on tensile properties of CNTs have been already performed, the coupling effects of CNTs and oblique impacts on tensile strength have yet to be reported. Due to the superior elastic modulus, the advanced nano-fillers were chosen as reinforcement of the carbon/Kevlar hybrid fibre. The inter-ply woven fabric possess high strength and excellent toughness due to the carbon and Kevlar fibre respectively and therefore well suited for ballistic impact applications. In spite of the fact that the effects of direct impact is most detrimental and widely reported, the effect of nano-fillers on the tensile integrity of oblique impacted specimens are of primary interest as most impact events are random in nature. CNTs with 0.1–1.5% loading ratios are dispersed into the epoxy resin and intra-ply Carbon Kevlar hybrid fabrics composite plates are fabricated via hand layup process. A loading of minimum 0.1% to maximum 1.5% CNTs were dispersed into liquid epoxy resin. The reinforced epoxy resin was applied to carbon/Kevlar fabric composite by layup process. Inclusion of CNT revealed depreciating mechanical properties in terms of tensile toughness; however, the inclusion demonstrated a potential reinforcement in a high modulus/strength in composite laminate’s specimens. Findings indicated that 0.7% of CNT had maximum tensile toughness values; whereas, the highest values of Young modulus were followed by tensile strength at 1.5% CNT. Moreover, compared with other factors, the impact load had a great influence on its specimens’ strength, and the effects of angled targets on the impact load of the specimens as well as CNTs' value were mostly obvious. Consequently, this investigation may be considered as a practical basis for designing and optimising of CNT contents and possible angle degrees and analysing tensile behaviour after the impact events.

Manufacturing and Characterization of Interply Hybrid Polymeric Biocomposite Material Reinforced with Glass and Carbon Fibers

AbstractThe objective of this study is to investigate the mechanical properties of the polymeric composite hybrid type interply reinforced with glass fibers GF and carbon fibers CF with the structure of the material consisting of: a) three layers CF:GF with the sequence [CF/GF/CF]; b) five layers CF:GF with the sequence: 1) [CF/GF/CF/GF/CF] and 2) [CF/CF/GF/CF/CF]. The GF:CF hybrid biocomposite interply type is made using the working methodology based on the Liquid resin Infusion (LRI) and Vacuum infusion techniques. The general mechanical properties are evaluated experimentally using standard tensile and bending tests using five specimens made according to ASTM standards. Based on the experimental results and the diagrams obtained at the tensile and bending tests of the hybrid polymeric biocomposite type interply comparisons are made regarding the mechanical properties of the composite for each type of structure. The general results confirm, from a mechanical point of view, the usefulness of this type of composite for engineering and biomedical applications.

A multiphase flow approach to gas permeability of composite facesheets during Co-cure of honeycomb core sandwich structures

Co-curing composites facesheets to produce sandwich structures involves heating a prepreg-core assembly in a vacuum bag and compacting it by an external pressure until the prepreg cures and bonds to the core. During this process, vacuum pressure can cause atmospheric air in the honeycomb core to bubble through uncured prepreg facesheets and impact material quality, such as excess resin bleed and void growth in either the facesheet or the bondline. In this paper, we propose a multiphase flow model to predict core gas pressure throughout the process. Fully impregnated prepreg facesheets only become permeable to gas as liquid resin desaturates pores in the fabric weave. To solve for the core gas pressure, resin and gas transport equations are solved simultaneously. The permeability of each phase is a function of saturation–defined by the Brooks-Corey model to be a power law function of the capillary pressure. Deviating from a single phase (gas only) model, using dimensionless analysis we identify four material properties which control the outcome: (i) an intrinsic permeability, K i, which only depends on the fabric architecture and is invariant to all process variables (time, temperature, pressure), (ii) the ratio of fluid viscosities, μ w/ μ g, where resin viscosity varies strongly with temperature and degree of cure, (iii) a bubbling (capillary) pressure, P b, which defines the minimum pressure needed to penetrate the largest pore, and (iv) a pore size distribution parameter, λ, which defines the percentage of pores which may desaturate given the evolving capillary pressure. Changes in observed gas permeability due to time and temperature are explained by the evolving desaturation of facesheet resin and the known relationship to resin viscosity. By applying this model, a reduced set to material characterization is required and complex process cycles can quickly be interrogated. With our experiments we demonstrate that one single value for K i and one single value for λ can be used to predict the gas pressure decay (time dependent) at different temperatures, confirming that the intrinsic permeability is constant for the fiber network and changes in the relative permeability to air are due to the decrease in viscosity only. The limitations of this model are presented and discussed.

Electrically conductive carbon fiber reinforced plastics induced by uneven distribution of polyaniline composite micron-sized particles in thermosetting matrix

We developed electrically conductive carbon fiber reinforced plastic (CFRP) for lightning strike protection by infusing carbon fiber (CF) woven fabric with a low viscosity liquid conductive thermosetting resin, providing a conductivity in the thickness direction of the CFRP of above 0.1 S/cm. The novel CFRP fabrication method uses a styrene derivative based thermosetting resin liquid dispersion including newly designed micron-size polyaniline (PANI)/dodecyl benzene sulfonic acid (DBSA) based composite particles. The dispersion liquid showed low viscosity and no viscosity increase at room temperature, and could penetrate into CF woven fabric and undergo a cross-linking reaction after heating to around 120 °C. Nine-layered stacked sheets were hot-pressed to make solid laminated composites with 50 vol% CF. The cross-section in the thickness direction was analyzed by optical microscopy, scanning electron microscopy, and electron probe microanalysis to determine the distribution of PANI/DBSA particles and CF per unit area. It was found that PANI/DBSA particles were located between the binding of the plain-woven CF, and showed a conductivity of 0.5 S/cm in the thickness direction, even when the PANI amount was as small as 4 wt%.

Studies on Water Absorption Properties of Fiber- Board Prepared Using Sugarcane Bagasse with Natural Resins

A study was conducted to evaluate the effect of fiber content and incorporation of natural resin on the water absorption behavior and swelling in thickness of sugarcane bagasse (SB)-reinforced epoxy-natural resin fiber-boards. Artificial (epoxy) and natural resins (cashew nut shell liquid (CNSL) resins, black dammar and pine resins) were used as a binder. The weight proportions of fiber: epoxy + hardener: natural resin were viz., 1:1:1.50, 1:1:1.75, 1:1:2. The lowest water absorption percent value for the sample immersed for 2 h and 24 h is shown by board prepared by mixing cashew nut shell liquid resin. There was less swelling in the thickness of the fiber board made with the fiber to resin weight ratio of 1:2.75. The cashew nut shell liquid resin was found to be effective in terms of Water absorption (WA) and thickness swelling (TS). Hence, the cashew nut shell liquid resin would be an alternate source for artificial resin source with less environmental hazards.

Electrostatic incitation on fiber surface for enhancing mechanical properties of fiber-reinforced composite

The excellent wettability contributes to the formation of mechanical interlocking morphologies at the interface as well as to the reduction of the internal defects in the composite for enhancing the mechanical properties of the fiber-reinforced composites. Herein, a facile and effective electrostatic method is proposed, where a small proportion of negative charges are merely sprayed on the fiber surface to modulate wettability. The results revealed that negatively charged fibers exhibit superior wettability for resin. Furthermore, the interfacial shear strength (IFSS) of the electrostatically treated T800H carbon fiber (T800H-ES)-based composite is 29.9% higher than that of the untreated-fiber composites. The improvement in interfacial properties is mainly ascribed to the formation of mechanical interlocking induced by surface charge-triggered Cassie-Baxter (CB) to Wenzel (WZ) transition of a liquid resin on the fiber surface, as verified by molecular dynamics (MD) simulations of carbon fiber–resin interfacial wetting. In addition, T800H-ES based composite has a 41.2% increase in tensile strength, a 22.5% increase in interlaminar shear strength (ILSS), and a 100.5% increase in fracture energy compared to as-received composite. These increases were mainly attributed to the improved interfacial adhesion and the reduction in internal composite defects. Consequently, this study reveals that the electrostatic charge-assisted wetting method is a green, cost-effective, and promising method for preparing composites with outstanding interfacial characteristics and mechanical properties.

High performance natural fiber composites from mat and UD flax reinforcements backed with a mat Binder: A study of mat fiber surface fibrillation

The natural fiber composites (NFC) market is growing at fast rate in markets such as automotive interiors, construction and wind energy. The major driving force is the rise in demand for lightweight and environmentally sustainable materials. This research aims at developing high performance NFC, made from hybridizing short flax fibers and unidirectional flax filaments in the fabrication of mat and combined UD flax-mat reinforcement, by studying the mechanical surface fibrillation of the short flax fibers to improve the fiber–matrix load transfer. The results show an increase in the longitudinal tensile properties up to about 500 mill revolutions, after which a deterioration of the fiber structure occurs with corresponding reductions on properties. However, fibrillation reduces permeability to liquid resin, except in the transverse direction of UD flax-mat reinforcement. Globally, the mechanical fibrillation has a positive impact on mechanical properties and fracture behavior while impregnation can be further improved to ease manufacturing.

An assessment on effect of process parameters on pull force during pultrusion

This research investigates the process behaviour by prediction of the pull force required to drag the raw materials through heated die at different reinforcing material configuration during pultrusion. Pultrusion is a continuous manufacturing process that is widely used in manufacture for composite profiles. A specially designed device, friction force by virtue of pulling on ‘resin impregnated’ fibres with both liquid resin and partially cured resin, was employed to measure pulling force against temperature and resin conversion. This allowed to experimentally simulate materials tracing in short and long die length used in process. Differential scanning calorimetry (DSC) was used to determining polymer conversion. The results shows that the downstream part of a die has no significant effect on the pulling force before a specific conversion level is achieved and that higher resin conversion leads to a higher friction at viscous/liquid zone. The difference noted is much more significant when the temperature is low (e.g. room temperature) and considerably drops due to on rising temperature. Further, a new mathematical model is proposed that predicts the rise in compaction pressure on increasing fibre volume fraction and drag velocity which is an opposite characteristic to tapping angle and part thickness considerations. Similarly, many parameters including shrinkage, viscous force and dry friction were modelled and simulated for ortho polyester resins as a function of temperature and resin conversion during dynamic pulling. The study has direct application in configuring pultrusion manufacturing customisation for a specific configured material, components manufacturing and respective designing of the die for the profile to be manufactured.

The Preforming of an Interlaminar Toughened Carbon Fiber/Bismaleimide Resin Composite by a Benzoxazine-Based Tackifier.

When thermoplastic resin-toughened carbon fiber (CF) composites are formed by liquid resin transfer molding (RTM), the conventional methods cannot be used to set the fabric preform, which affects the overall mechanical properties of the composites. To address this challenge, the benzoxazine-based tackifier BT5501A was designed, a preforming–toughening bifunctional CF fabric was fabricated by employing thermoplastic polyaryletherketone (PEK-C), and an aviation RTM-grade bismaleimide (BMI) resin was used as the matrix to study the effect of the benzoxazine-based tackifier on the thermal curing property and heat resistance of the resin matrix. Furthermore, the preforming and toughening effects on the bifunctional CF fabric reinforced the BMI resin composites. The tackifier BT5501A has good process operability. The application of this tackifier can advance the thermal curing temperature of the BMI resin matrix and decrease the glass transition temperature of the resin, compared to that of the pure BMI resin. Furthermore, when the tackifier was added into the CF/PEK-C/BMI composites, the obtained CF/BT5501A/PEK-C/BMI composites had comparable compression strength after impact, pit depth, and damage area, compared to the CF/PEK-C/BMI composites, while the tackifier endowed the fabric preform with an excellent preforming effect.

FORMATION OF POWDER COATING PROPERTIES IN THE SYSTEM "FILM-FORMING ‒ CROSS-LINKING AGENT"

The results of the influence of film formers of different types on the formation of the properties of powder paints and coatings based on them was showed. Powder coating are one of the most promising types of paints and varnishes for industrial use. Their main advantages are the absence of solvents, virtually waste-free coating technology (the degree of utilization of the powder in the application is close to 100 %), relative simplicity and efficiency in the production process of the coating. As a result of study it has been revealed that the use of powder coating systems of different chemical nature provides higher physical and mechanical characteristics of coatings in comparison with traditional systems based on liquid acrylic resin, which in its turn allows to consider such systems as an alternative for protection of construction metal products and structures against the mechanical influences. At the same time, it has been shown that a change in the film former and crosslinking agent in the composition of powder systems differently influences the formation of powder coating properties depending on the type of the film former and its characteristics (viscosity, glass transition temperature) as well as the type of the crosslinking agent. The use of systems "polyester film forming – TGIC", "polyester film forming – НАА" provide high physical and mechanical properties of coatings without deterioration of technological properties of systems, when using film forming with dynamic Brookfield viscosity values within 30oC). In turn, the decrease of the glass transition temperature index and the increase of the resin viscosity index negatively affect the formation of the technological properties of the powder systems and, accordingly, the physical and mechanical characteristics of the coating.

The application of liquid crystalline epoxy resin for forming hybrid powder coatings

The application of liquid crystalline epoxy resin for forming hybrid powder coatings

High‐Precision Printing of Complex Glass Imaging Optics with Precondensed Liquid Silica Resin (Adv. Sci. 18/2022)

3D Printing of Glass Imaging Optics In article number 2105595, Douglas A. Loy, Rongguang Liang, and co-workers develop a liquid silica resin (the left molecule in the picture) to print optical element with high precision through two-photon polymerization. The printed optics is then converted to inorganic glass (silicon dioxide, the right molecule in the picture) through thermal treatment. Precision complex glass optical systems, such as micro-objective (in the picture), can be fabricated. This research demonstrates that 3D printing of glass imaging optics has a high potential for precision optical imaging applications.

Comparison of product safety data sheet ingredient lists with skin irritants and sensitizers present in a convenience sample of light-curing resins used in additive manufacturing

Material jetting and vat photopolymerization additive manufacturing (AM) processes use liquid resins to build objects. These resins can contain skin irritants and/or sensitizers but product safety data sheets (SDSs) might not declare all ingredients. We characterized elemental and organic skin irritants and sensitizers present in 39 commercial products; evaluated the influence of resin manufacturer, system, color, and AM process type on the presence of irritants and sensitizers; and compared product SDSs to results. Among all products, analyses identified 23 irritant elements, 54 irritant organic substances, 22 sensitizing elements, and 23 sensitizing organic substances; SDSs listed 3, 9, 4, and 6 of these ingredients, respectively. Per product, the number and total mass (an indicator of potential dermal loading) of ingredients varied: five to 17 irritant elements (8.32–4756.65 mg/kg), one to 17 irritant organics (3273 to 356,000 mg/kg), four to 17 sensitizing elements (8.27–4755.63 mg/kg), and one to seven sensitizing organics (15–382,170 mg/kg). Median numbers and concentrations of irritants and sensitizers were significantly influenced by resin system and AM process type. The presence of undeclared irritants and sensitizers in these resins supports the need for more complete information on product SDSs for comprehensive dermal risk assessments.

Enhanced thermal conductivity of epoxy acrylate/h‐BN and AlN composites by photo‐curing 3D printing technology

AbstractFilling hexagonal boron nitride (h‐BN) is a hot topic in the research of improving the thermal conductivity of polymer composites. Conversely, its difficulty in dispersing and forming a three‐dimensional thermal network has become a major problem. This article uses liquid resin can effectively help the filler to be evenly dispersed and construct a multi‐layer connection network through 3D printing technology, which improves the thermal conductivity of polymer effectively. With the addition of 30 wt% h‐BN, the thermal conductivity of the epoxy acrylate (EA) composite reaches 1.60 Wm−1 K−1, which is 6.8 times that of pure epoxy acrylic resin. Our work provides a new idea for improving the thermal conductivity of photocured polymers.

Arkema Introduces TIPPOXTM 2028 thermal PMMA stabilizer, Clearstrength® XT 151 additive and Sartomer® advanced tough liquid resins, and receives certification for its bio-based materials made from castor crops.

On May 10, Arkema announced the launch of TippoxTM 2028 stabilizer, an optimized stabilizer for its growing base of customers in PMMA production. TippoxTM 2028 stabilizer is claimed to offer a new approach to traditionally utilized methods of handling thermal degradation.