Thermoplastic Particles Research Articles

Self-Granulating Thermoplastic Elastic Particles for Fracture Conformance Control in Ultraharsh Reservoirs: Laboratory Investigation and Field Application

Self-Granulating Thermoplastic Elastic Particles for Fracture Conformance Control in Ultraharsh Reservoirs: Laboratory Investigation and Field Application

Synergistic Effects of Liquid Rubber and Thermoplastic Particles for Toughening Epoxy Resin

This study aims to investigate the toughening effects of rubber and thermoplastic particles on epoxy resin (EP), and to understand the mechanism underlying their synergistic effect. For this purpose, three EP systems were prepared using diglycidyl ether of bisphenol-A (DGEBA) epoxy resin (E-54) and 4,4-Diamino diphenyl methane (Ag-80) as matrix resin, 4,4-diaminodiphenyl sulfone (DDS) as a curing agent, and phenolphthalein poly (aryl ether ketone) particles (PEK-C) and carboxyl-terminated butyl liquid rubber (CTBN) as toughening agents. These systems are classified as an EP/PEK-C toughening system, EP/CTBN toughening system, and EP/PEK-C/CTBN synergistic toughening system. The curing behavior, thermal properties, mechanical properties, and phase structure of the synergistic-toughened EP systems were comprehensively investigated. The results showed that PEK-C did not react with EP, while CTBN reacted with EP to form a flexible block polymer. The impact toughness of EP toughened by PEK-C/CTBN was improved obviously without significantly increasing viscosity or decreasing thermal stability, flexural strength, and modulus, and the synergistic toughening effect was significantly higher than that of the single toughening system. The notable improvement in toughness is believed to be due to the synergistic energy dissipation effect of PEK-C/CTBN.

Influence of fatigue damage on the impact performance of toughened-interleave carbon fibre epoxy composite laminates

The impact performance of mechanically fatigued carbon fibre-reinforced polymer (CFRP) composite laminates with and without thermoplastic toughening particles has been investigated through a joint experimental and numerical campaign. Prismatic carbon fibre/epoxy specimens with added toughening particles at the ply interfaces were mechanically fatigued with different load amplitudes leading to a loss in apparent stiffness of 10% to 15%. Following the fatigue loading, high resolution computed tomography (CT) has been performed, revealing varying degrees of delamination starting from the free edges along the length of the specimens. In addition, transverse matrix cracks are observed in all fatigued specimens regardless of the amount of delamination. The residual ballistic impact performance of the damaged specimens has been investigated in a dynamic three-point bending configuration at three different velocities, showing a significant detrimental effect of even barely visible initial delamination. In addition, post-mortem CT scans and detailed finite element simulations are used to gain further insight into the mechanisms by which the two types of initial damage affected the impact resistance of the laminates. Finally, repeating the same experiments on a similar CFRP system without discrete toughening particles showed that their inclusion significantly increased the impact resistance both with and without prior fatigue damage.

Preparation and properties of poly[(butylene adipate)‐co‐terephthalate]/thermoplastic hydroxypropyl starch films

AbstractPoly[(butylene adipate)‐co‐terephthalate] (PBAT) is currently the most widely used and versatile petroleum‐based fully biodegradable polyester, drawing extensive attention from researchers. However, the high production cost of PBAT restricts its widespread application. Currently, incorporating fillers into PBAT materials is considered the most effective approach to reduce production costs, with thermoplastic starch recognized as the optimal filler for PBAT base materials. Nevertheless, the low mechanical strength of thermoplastic starch significantly compromises the performance of PBAT base materials. In this study, thermoplastic starch with higher mechanical strength was prepared by partially substituting commonly used glycerol with a higher molecular weight sorbitol as the plasticizer. The enhanced thermoplastic starch was then used as a filler for PBAT materials, leading to the fabrication of PBAT‐based blend films with high starch content. Mechanical property tests revealed a 52.2% and 65.3% increase of tensile strength in the transverse and longitudinal directions, respectively, when sorbitol partially replaced glycerol as the plasticizer for thermoplastic starch. Scanning electron microscopy results demonstrated improved dispersion of thermoplastic starch particles in PBAT when sorbitol and glycerol were used together. Meanwhile, the thermal performance and stability of PBAT were not significantly affected by the thermoplastic starch filling. © 2024 Society of Chemical Industry.

Effect of thermoplastic particles on the mechanical performance and damage failure of notched fibre metal laminates

This study aims to explore the open-hole tension of fibre metal laminates containing thermoplastic particles experimentally and theoretically. In this regard, a vacuum bagging infusion process has been used to manufacture glass and glass metal laminates. Further, the tensile strength and damage failure modes were predicted using the Abaqus software, finite element analysis (FEA). This prediction was performed under a tensile test for notched composite laminates. The results of experimental tests indicated that the notch sensitivity is very important in terms of fracture and failures of composites. Furthermore, the findings show that the fibre metal laminates are less notch sensitive than glass composite laminates because of enhancing the composite ductility. In total, 28% of tensile strength decrease has been achieved after having holes for glass composites while the reductions were only 22%, 15% and 13% for glass composite laminates that have one, two and three aluminium layers, respectively. This reduction also becomes 4% for glass composite laminates that have one aluminium layer and thermoplastic particles and they exhibit typical ductile damage failures compared to other laminates. Further, the findings of numerical simulation for tensile strength and damage failure modes follow experimental results both qualitatively and quantitatively for notched composite laminates under tension loading.

Manufacturing Method and Characteristics of Nanocopper Fiber Yarn

In this study, several samples of nanocopper fiber fabrics with different proportions of copper content were used. Among them, black copper antibacterial staple Polyamide fiber (PA) and 6 wt.% copper antibacterial fabric were selected. Positron emission tomography (PET) and other fabrics containing nanocopper components were used as experimental control samples. In the process, a raw material containing blending slurry, a nanometal solution, several inorganic particles, and thermoplastic polyurethane colloidal particles were used. The raw material was mixed and stirred before being dried and hot-melted. In the first stage of the process, the wire was cooled vigorously for conversion into the second stage form where it became a final product, a nanocopper fiber yarn. Taguchi analysis was used to compare the antibacterial property of the nanocopper powder between different particle sizes under the same distribution, weight, and fiber granulation characteristics. Two bacterial species, specifically Escherichia coli and Staphylococcus aureus, were used to investigate the antibacterial property of the fabric. In addition, we investigated the mechanical properties of the fabric and observed its surface structure. The copper content in the nanocopper fiber fabrics was detected using an X-ray fluorescence spectrometer. This finding indicate that the samples contained copper antibacterial components fabrics. Subsequently, the uniformity and aggregation degree of the copper distribution on the fiber fabrics were compared between different fiber polyester materials.

Effects of accelerated curing in thermoplastic particle interleaf epoxy laminates

Faster heating rates of 10 °C/min and higher process temperatures of 210 °C were applied to the commercial M21 resin system. The total process time was reduced by two-thirds while achieving the same degree-of-cure in the epoxy. Thermal analysis and hot-stage microscopy showed that the thermoplastic interleaf particles melt at around 15 °C above the manufacturer's recommended 180 °C curing temperature. A short dwell at 180 °C was found to prevent the thermoplastic particle from mixing with the thermoset pre-polymer before ramping to the accelerated curing temperature of 210 °C. Such interaction was found to decrease the glass transition temperature by 13–45 %, but increase the mode I delamination resistance by 70–105 %, respectively. The results demonstrate that accelerated curing of interleaf systems can shorten cycle time and produce a range of physical and mechanical properties from a single base material, opening the design space to new and optimised composite structures.

Thermoplastic coating on fiber reinforced polymer composites by cold spray additive manufacturing

This work investigates the cold spray coating of nylon 6 on fiber-reinforced composite substrates. Deposition conditions are investigated by systematically varying the process parameters (impact velocity, temperature, carrier gas pressure, and flow rate) for two woven fiber-reinforced epoxy substrates with glass and carbon fiber reinforcements, resulting in deposition efficiencies exceeding 30%. Parametric studies are performed to identify the optimal system pressure and powder flow rates that lead to the successful deposition of the powder particles on composite substrates. It is observed that, upon impact, the particles undergo extensive plastic deformation without damaging the reinforcing fibers in the substrate. Microstructural observations reveal that the first (seeding) layer of nylon particles experiences a higher degree of plastic deformation due to the impact on a stiff substrate. The large plastic deformation in the impacting particles plays a key role in enabling adhesion to the substrate. The successive layers of deposited particles undergo less plastic deformation as they impact a comparatively softer pre-deposited nylon substrate. The underlying deposition mechanisms are further explored using multiscale finite element analyses. Results obtained in this work demonstrate the feasibility of cold spray deposition of thermoplastic particles on fiber-reinforced composites without imposing significant damage to the substrate.

Microscale evaluation of epoxy matrix composites containing thermoplastic healing agent

Among the strategies to produce healable thermosetting systems is their modification by the addition of thermoplastic particles. This work investigates the influence of poly(ethylene-co-methacrylic acid) (EMAA) on fiber-matrix interfacial properties of a glass fiber reinforced epoxy matrix composite. Epoxy-EMAA interactions were evaluated using differential scanning calorimetry (DSC) and infrared spectroscopy. The effects of EMAA on the epoxy network formation were evidenced by changes in glass transition temperature, cure kinetics and alteration of chemical groups during cure. Interfacial shear strength (IFSS) measurements obtained by single fiber pull-out tests indicate similar interfacial properties for pure and EMAA modified epoxy. Additionally, the potential for self-healing ability of an EMAA modified epoxy was demonstrated. However, IFSS after a healing cycle for the EMAA modified epoxy was lower as compared to the pure epoxy, because of the lower fiber-EMAA interfacial shear strength. So, thermoplastic healing agents has not only to fill cracks in the matrix material, but also have to be optimized regarding its interface properties to the reinforcing fibers.

Toughening effect of self-assembled thermoplastic particles on phthalonitrile containing benzoxazine and improved mechanical properties in the presence of fibers reinforcement

Phthalonitrile containing benzoxazine resin (BA-ph) was a new type of high-performance resin which could be used at high temperature by autocatalytic molding at low temperature. However, its brittleness after polymerization and weak interaction with fibers when it as the matrix of fiber reinforced composites (FRC) were obstacles to its wide application. In this study, Poly (arylene ether nitrile) containing phenolphthalein (PP-PEN) was introduced by solution blending to toughen BA-ph and its glass fiber (GF) FRC. The effects of PP-PEN on the crosslinking behavior and processability of BA-ph were studied by differential scanning calorimetry (DSC) and dynamic rheology analysis (DRA). The effect of PP-PEN on the structural strength and thermal stability of BA-ph/GF was further studied by other characterization methods. The non-notchable impact strength of BA-ph/PP-PEN/GF FRC formed at lower temperature (200 °C) could reach 148 kJ/m2, which was 91.4% higher than that of BA-ph/GF FRC. Furthermore, the fracture morphology showed that PP-PEN significantly enhanced the interfacial strength between BA-ph and GF. It has potential applications in aerospace, rail transportation and the fields requiring high-performance polymer matrix FRC.

Polyamide-nylon 6 particulate polycarbonate composites with outstanding energy-absorbing properties

As there are gradually increasing interests in polymeric energy-absorbing materials to reduce unwanted noise/vibration, and enhance impact resistance in structural applications, considerable efforts have been empirically made to improve energy-absorbing properties. However, there has been no detail understanding of the energy-absorbing mechanisms of particulate composites, thereby showing a trade-off between toughness and modulus/strength. Therefore, by coupling modeling and experimental efforts, this study systematically explores the thermoplastic polymer particle toughening and ways to overcome the typical compromise in energy-absorbing composites. Polyamide-nylon 6 particulate polycarbonate composite was carefully designed for achieving extraordinary energy absorption with the uncompromised properties. The debonding, fracture toughness and yieldings were semi-empirically investigated to reveal fracture energy contributions. It was found that the mainly responsible energy-absorbing mechanism was matrix yielding (48.28%), which results from the particle debonding and significantly contribute to crack propagations. This study could provide new solutions for the energy-absorbing composites without any comprome in modulus/strength.

On the mix-mode fracture of carbon fibre/epoxy composites interleaved with various thermoplastic veils

This work studied the mix mode-I/II fracture behaviour of an aerospace-grade carbon fibre/epoxy composite that was interlayer-toughened by Polyamide-12 (PA), Polyphenylene-sulphide (PPS), Polyimide (PI), Polyethersulfone (PES) and Polyethylenimine (PEI) fibres. During the laminate curing process, the PA fibres melted, the PPS and PI fibres kept in their original form and the PES and PEI fibres dissolved in the epoxy matrix. This resulted in different toughening mechanisms of the veils for the mix mode-I/II fracture of the laminates, which was studied using a cracked lap-shear test. The main toughening mechanisms were observed to be plastic deformation and failure of the thermoplastic resin for the meltable PA veils, thermoplastic fibre debonding and bridging for the intact PPS and PI veils, and thermoplastic particle debonding and plastic void growth for the dissolvable PES and PEI veils. The experimental results revealed that the fibre debonding and bridging mechanism was superior for toughness enhancement, followed by the thermoplastic particle debonding and plastic void growth mechanism. For instance, interleaving the PPS and PEI veils increased the mix-mode fracture propagation energy of the laminates by 345% and 171%, respectively. However, the toughening performance of the PA and PI veils was poor, since the crack mainly propagated at the vicinity around the interlayer/laminate interface.

Application of Image Technique to Obtain Surface Velocity and Bed Elevation in Open-Channel Flow

The frequency of droughts and floods is increasing due to the extreme climate. Therefore, water resource planning, allocation, and disaster prevention have become increasingly important. One of the most important kinds of hydrological data in water resources planning and management is discharge. The general way to measure the water depth and discharge is to use the Acoustic Doppler Current Profiler (ADCP), a semi-intrusive instrument. This method would involve many human resources and pose severe hazards by floods and extreme events. In recent years, it has become mainstream to measure hydrological data with nonintrusive methods such as the Large-Scale Particle Image Velocimetry (LSPIV), which is used to measure the surface velocity of rivers and estimate the discharge. However, the unknown water depth is an obstacle for this technique. In this study, a method combined with LSPIV to estimate the bathymetry was proposed. The experiments combining the LSPIV technique and the continuity equation to obtain the bed elevation were conducted in a 27 m long and 1 m wide flume. The flow conditions in the experiments were ensured to be within uniform and subcritical flow, and thermoplastic rubber particles were used as the tracking particles for the velocity measurement. The two-dimensional bathymetry was estimated from the depth-averaged velocity and the continuity equation with the leapfrog scheme in a predefined grid under the constraints of Courant–Friedrichs–Lewy (CFL). The LSPIV results were verified using Acoustic Doppler Velocimetry (ADV) measurements, and the bed elevation data of this study were verified using conventional point gauge measurements. The results indicate that the proposed method effectively estimated the variation of the bed elevation, especially in the shallow water level, with an average accuracy of 90.8%. The experimental results also showed that it is feasible to combine the nonintrusive imaging technique with the numerical calculation in solving the water depth and bed elevation.

A Healable Epoxy with Comprehensive Properties by Incorporating Thermoplastic Epoxy Microspheres

AbstractHealable materials by incorporating thermoplastic particles as healants can not only possess healability, but also retain the intrinsic properties of the host matrix. Herein, solid healant microspheres made of a thermoplastic epoxy poly(bisphenol A‐co‐epichlorohydrin) are fabricated using a solvent evaporation technique and then incorporated into the thermosetting epoxy to formulate a healable epoxy. Slight dissolution of the microspheres is observed during the curing process of the matrix, which strengthens the bond between the microspheres and matrix. The healing performance is tested after heating at 180 °C for 20 min, and maximum healing efficiency of about 95% is achieved. Due to the thermoplastic feature of the healant, this healable system possesses multi‐time healability. Expectedly, it shows the solid microspheres increase the fracture toughness and do not evidently affect the tensile and thermal properties of the epoxy matrix. This developed healable material with comprehensive properties promises a potentially practical healing system.

Environmental Effects on the Coefficient of Friction and Tack Adhesion of Formulated Waterborne Coatings

Waterborne coatings emit a low amount of harmful volatile organic compounds (VOCs) into the atmosphere compared to solvent-cast coatings. A typical waterborne formulation for agricultural applications consists of colloidal thermoplastic particles (latex) as the binder, a thickener to raise the viscosity, inorganic filler particles with a water-soluble dispersant, and a colloidal wax to modify surface properties. The formulations typically contain hygroscopic species that are potentially subject to softening by environmental moisture. The hardness, tack adhesion, and coefficient of friction of formulated coatings determines their suitability in applications. However, the relationship of these properties to the components in a coating formulation has not been adequately explored. Furthermore, the relationship between hygroscopic components and properties is an added complication. Here, we have characterized the hardness and tack adhesion of model formulated coatings using a single micro-indentation cycle with a conical indenter under controlled temperatures (above and below the glass transition temperature of a latex binder) and relative humidities. In parallel, we measured the coefficient of kinetic friction, μk, for the same coatings using a bespoke testing rig under controlled environmental conditions. Across a range of temperatures, RH and compositions, we find an inverse correlation between the coating hardness and μk. Any correlation of μk with the roughness of the coatings, which varies with the composition, is less clear. Formulations that contain wax additives have a higher μk at a low RH of 10%, in comparison to formulations without wax. For the wax formulations, μk decreases when the RH is raised, whereas in non-wax formulations, μk increases with increasing RH. Wax-containing coatings are hydrophilic (with a lower water contact angle), however the wax has a lower water permeability. A lubricating layer of water can explain the lower observed μk in these formulations. The addition of wax is also found to planarize the coating surface, which leads to higher tack adhesion in dry coatings in comparison to coatings without wax. Greater adhesive contact in these coatings can explain their higher friction. Our systematic research will aid the design of seed coating formulations to achieve their optimum properties under a wide range of environmental conditions.

Effects of Modified Thermoplastic Starch on Crystallization Kinetics and Barrier Properties of PLA.

This study reports on using reactive extrusion (REX) modified thermoplastic starch particles as a bio-based and biodegradable nucleating agent to increase the rate of crystallization, percent crystallinity and improve oxygen barrier properties while maintaining the biodegradability of PLA. Reactive blends of maleated thermoplastic starch (MTPS) and PLA were prepared using a ZSK-30 twin-screw extruder; 80% glycerol was grafted on the starch during the preparation of MTPS as determined by soxhlet extraction with acetone. The crystallinity of PLA was found to increase from 7.7% to 28.6% with 5% MTPS. The crystallization temperature of PLA reduced from 113 °C to 103 °C. Avrami analysis of the blends showed that the crystallization rate increased 98-fold and t1/2 was reduced drastically from 20 min to <1 min with the addition of 5% MTPS compared to neat PLA. Observation from POM confirmed that the presence of MTPS in the PLA matrix significantly increased the rate of formation and density of spherulites. Oxygen and water vapor permeabilities of the solvent-casted PLA/MTPS films were reduced by 33 and 19% respectively over neat PLA without causing any detrimental impacts on the mechanical properties (α = 0.05). The addition of MTPS to PLA did not impact the biodegradation of PLA in an aqueous environment.

Structural design to enhance mechanical properties of carbon-fiber-reinforced thermoplastics using colloidal particles and soft and hard resins

Carbon-fiber-reinforced plastics (CFRPs) can facilitate vehicular weight reduction and thus have attracted significant attention in the automobile industry. Currently, a thermosetting resin is commonly used as a CFRP matrix, and carbon-fiber-reinforced thermoplastics (CFRTP) have been widely investigated owing to their low weight and utility in mass production. However, the materials used in vehicles must have high energy absorption, i.e., high residual stress. Herein, the surface modification of carbon fibers with thermoplastic particles were modified to improve the interfacial properties of the carbon fibers and thermoplastic resin and enhance the bending strength of the CFRTP. Furthermore, the energy absorption of the CFRTP was improved by incorporating two different thermoplastic resins into the structure; a high impact strength polymer alloy (HISPAT) provided by Toyota Boshoku that served as a soft layer, and polyamide 6 (PA6), known as engineering plastic, as a hard layer. Furthermore, structural design was improved to enhance the energy absorption and strength of the CFRTP.

Synthesis and characterization of the properties of thermosensitive elastomers with thermoplastic and magnetic particles for application in soft robotics

AbstractIn the currently rapidly developing field of soft robots, smart materials with controllable properties play the central role. Thermosensitive elastomers are soft, smart materials whose material properties can be controlled by changing their temperature. The aim of this work is to investigate the mechanical properties, to analyze the surface, the inner structure, and the heat transfer within the thermosensitive elastomer materials. This should provide a knowledge base for new combinations, such as a combination of thermosensitive and the well‐known magneto sensitive elastomers, in order to realize new applications. Thermoplastic polycaprolactone particles were incorporated into a flexible polydimethylsiloxane matrix to produce thermosensitive elastomer samples. With a low melting point in the range of 58–60°C, polycaprolactone offers good application potential compared to other thermoplastic materials such as polymethamethylacrylate with a melting point above 160°C. Test samples of different material compositions and geometries were made to examine temperature‐depending material properties. Two useful effects were identified: temperature‐dependent change in stiffness and the shape memory effect. In certain examinations, carbonyl iron particles were also included to find out if the two particle systems are compatible with each other and can be combined in the polydimethylsiloxane matrix without disadvantages. Changes in shore hardness before and after the influence of temperature were investigated. Micro computed tomography images and scanning electron microscopy images of the respective samples were also obtained in order to detect the temperature influence on the material internally as well as on the surface of the thermosensitive elastomers in combination with carbonyl iron particles. In order to investigate the heat transfer within the samples, heating tests were carried out and the influence of different particle concentrations of the thermosensitive elastomers with and without carbonyl iron particles was determined. Further work will focus on comprehensive investigations of thermo‐magneto‐sensitive elastomers, as this will enable the functional integration in the material to be implemented with increased efficiency. By means of the different investigations, the authors see future applications for this class of materials in adaptive sensor and gripper elements in soft robotics.

The role of poly (ethylene-co-methacrylic acid) (EMAA) on cure kinetics and thermomechanical properties of epoxy

The addition of thermoplastic to thermosetting matrix systems has been proposed as a successful strategy to produce polymers with self-healing ability. Curing mechanism of diglycidyl ether of bisphenol A/triethylene-tetramine epoxy system modified with poly(ethylene-co-methacrylic acid) (EMAA) thermoplastic healing agent was investigated in this work. The effects of thermoplastic content, particle size and dispersion on thermomechanical properties were studied. Specimens were produced with 5 wt. %, 10 wt. % and 15 wt.% EMAA with particle sizes ≤ 125 μm or ≤ 425 μm. The addition of thermoplastic produced a reduction in E’ of about 27% for samples with particles ≤ 125 μm and about 45% for samples with particles ≤ 425 μm. Samples with particle size ≤ 125 μm showed a reduction in Tg of up to 37 °C as compared to neat epoxy. In the case of samples with particle size ≤ 425 μm, no direct correlation between Tg and mass fraction of added EMAA is found. Thus, particle size played an important role on thermomechanical properties and cure kinetics of epoxy. The greater the interfacial area, the greater was the change in final properties as compared to the unmodified material. It was also observed that the mass fraction and particle size can interfere in the curing reactions, where results suggest deceleration when smaller particles (≤ 125 μm) are added in larger fractions and acceleration with increasing mass fraction of larger particles (≤ 425 μm). All experimental reactions could be fit to the autocatalytic Sourour and Kamal model with good agreement; the model was able to predict the effects of thermoplastic addition in different particle sizes and mass fractions.

The influence of temperature and moisture on the mode I fracture toughness and associated fracture morphology of a highly toughened aerospace CFRP

This paper addresses the characterisation of the mode I interlaminar fracture toughness of a carbon fibre/epoxy composite material, toughened with thermoplastic particles in the ply interlayers. The characterisation is undertaken at −55 °C, 19 °C, and 90 °C, on both dry and fully moisture saturated coupons. Fractographic observations of the delamination surfaces allows identification of the failure mechanisms. The mode I propagation fracture toughness tested at wet/90 °C exhibits a 176% increase compared to the dry/19 °C specimens, due to enhanced plastic deformation of the interlayers and more prominent fibre bridging. Moisture-saturated coupons tested at −55 °C suffered a 57% reduction of mode I fracture toughness compared to those under dry/19 °C conditions. This is due to the dis-bond and consequent plucking of the thermoplastic particles from the surrounding matrix. This observation points to the fact that wet/cold conditions may represent the worst-case scenario for the interlaminar fracture performance of composite systems toughened with thermoplastic interleaves.