Enhanced Scratch Resistance Research Articles

Scratch resistance of glass‐basalt fiber reinforced epoxy hybrid composites: A comparative study

AbstractThis research explores the scratch resistance of polymer composites reinforced with hybrid glass and basalt fibers under repeated loadings. By examining the behavior across 1–10 repetitions using Rockwell and Vickers indenters, the study delves into the complex interplay between composite matrices and the fibers' configurations. Through Scanning Electron Microscope (SEM) imaging and 3D profilometry, it reveals how different fibers influence the composite's surface post‐scratch tests. Basalt fibers are found to offer superior scratch protection over glass fibers, although both types' of effectiveness declines with increased loading cycles, showing significant material loss and surface damage respectively. Composites with these fibers display enhanced resistance, especially when basalt fibers are optimally positioned on the surface. The study underscores the critical role of fiber‐matrix bonding in scratch resistance and the significant impact of mechanical stress. It was found that the scratch hardness values reduced with more repeats in the scratch tests utilizing Vickers and Rockwell indenters. The sample with the label G4B6G4 has the greatest hardness values, which is noteworthy. After 10 repeats, the scratch hardness values for this sample reduced to 225 N/mm2 and 75 N/mm2, respectively, from roughly 340 N/mm2 and 225 N/mm2 at both ends for a single repetition. In addition, ANOVA for penetration depth is dominated (66.01%) by the repetition factor. The most common kind is indenter (42.79%), with low p‐values. Despite material and indenter effects, groove area study confirms the significance of repetition (65.72%).Highlights Basalt fibers enhance scratch resistance more than glass fibers. Increased scratch repetitions lead to fiber breakage and material loss. Hybrid fiber layers distribute load and minimize surface damage. Strong fiber‐matrix adhesion is crucial for reducing damage severity. Research informs the design of durable, fiber‐reinforced composites.

The Scratch Resistance of a Plasma-Assisted DUPLEX-Treated 17-4 Precipitation-Hardened Stainless Steel Additively Manufactured by Laser Powder Bed Fusion

The Scratch Resistance of a Plasma-Assisted DUPLEX-Treated 17-4 Precipitation-Hardened Stainless Steel Additively Manufactured by Laser Powder Bed Fusion

Mechanical properties and scratch recovery of nanoclay/polyester composite coatings for pre-coated metal (PCM) sheets

Scratch resistance is crucial for the polyester coating on pre-coated metal (PCM) used in domestic appliances and automotive parts to prevent aesthetic degradation and corrosion of the steel substrate. Incorporating nanoclay filler into a polyester coating has demonstrated the potential to enhance scratch resistance. In this study, Lucentite™ (LU) nanoclay with hydrophilic surface modification was added into polyester to fabricate LU/polyester nanocomposite coatings. Nanoindentation and scratch were applied to evaluate the hardness and scratch resistance of the polyester-based coatings, respectively. The result showed that as the LU loading increased from 0.0 to 5.0 wt%, the coating hardness decreased from 187 ± 3 MPa to 107 ± 11 MPa. This softening effect is ascribed to the interactions between the modified clay surface and crosslinker, resulting in reduced degree of crosslinking. Despite the decrease in hardness, adding LU resulted in impressive self-healing abilities of the coatings, attributed to both the reduced crosslinking density and the rotation of the LU platelets. The magnitude of recovery increased with the LU loading. When subjected to scratch loads between 5 and 40 mN, coatings with 5.0 wt% LU demonstrated full recovery after 100 min, while the pure polyester only exhibited 80%–63 % recovery 1000 min after scratch. This unique ability can provide a significant advantage for utilizing these polyester-based composite coatings on PCM sheet.

Superlubricity and Stress-Shielding of Graphene Enables Ultra Scratch-Resistant Glasses.

Glasses, when subjected to scratch loading, incur damages affecting their optical and mechanical integrity. Here, it is demonstrated that silica glasses protected with mechanically exfoliated few-layer graphene sheets can exhibit remarkable improvement in scratch resistance. To this extent, the friction and wear characteristics of silica glasses with exfoliated graphene using atomic force microscopy (AFM) are explored. The friction forces recorded during AFM scratch tests of the graphene-glass surfaces at multiple loads exhibit ∼98% reduction compared to that of the bare silica glass, with the friction coefficient falling in the superlubricity regime. This dramatic reduction in friction achieved by the graphene sheets results in significantly lower wear of the graphene-glass surfaces postscratching. Further investigations employing atomistic simulations reveal that the stress-shielding mechanism is due to the reduced deformation of graphene-glass surfaces, thereby curtailing the overall damage. Altogether, the present work provides a new fillip toward the development of glasses with enhanced scratch resistance exploiting two-dimensional coatings.

Miscibility and related rheological, physical, and optical properties of polycarbonate/poly(methyl methacrylate-co-phenyl methacrylate) blends: Effect of varying phenyl methacrylate composition

This study presents a systematic investigation of miscibility, rheological, and physical/optical properties of polycarbonate (PC)/poly (methyl methacrylate-co-phenyl methacrylate) (PMMA-co-PPhMA) blends with varying copolymer composition and blend weight percentage (wt%). Herein, single glass transition behavior from miscible blends was confirmed through differential scanning calorimetry (DSC) and dynamic mechanical analyzer (DMA), while further analysis revealed differences in blend homogeneity. X-ray scattering and rheometer measurements complemented this different phase homogeneity in the blends. PMMA-co-PPhMA with 14 mol% of PhMA (denoted as PMPA-2) demonstrated the most favorable miscibility and phase homogeneity among the prepared blends. Enhanced scratch resistance was achieved by increasing the wt% of PMMA-co-PPhMA, but phase inhomogeneity resulted in decreased optical transparency. The blend between PC and PMPA-2 exhibited optimal rheological, mechanical, and optical properties. This study provides insights into the PC-based blend materials for applications in various industrial fields.

Electrospun glass nanofibers to strengthen polycarbonate plastic glass toward photoluminescent smart materials

Electrospun glass nanofibers (GNFs) were used to strengthen polycarbonate (PC) to create long-persistent photoluminescent and fluorescent smart materials such as afterglow concrete and smart window. Physical integration of lanthanide-activated aluminate (LA) nanoparticles (NPs) yielded transparent GNFs@PC smart sheets. Spectral investigations utilizing photoluminescence and CIE Lab parameters were performed to confirm that the translucent appearance of GNFs@PC changed to green when exposed to UV light. This fluorescence activity was quickly reversible for the GNFs@PC hybrids with low concentrations of LANPs, which indicate fluorescence emission. Higher phosphor concentrations in GNFs@PC led to longer-lasting afterglow photoluminescence and slower reversibility. The GNFs@PC hybrids showed an emission band detected at 518 nm upon excitation at 368 nm. The morphological characteristics of LANPs and GNFs were analyzed by transmission electron microscopy (TEM), which revealed sizes of 11–26 nm and 250–300 nm, respectively. GNFs were prepared using electrospinning technology and then used as a roughening agent into PC sheets. Morphological characteristics of GNFs and GNFs@PC smart sheets were examined using energy-dispersive X-ray spectroscopy (EDXA), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). The GNFs@PC smart sheets were shown to have enhanced scratch resistance in comparison to LANPs-free PC control sample. Increases in LANPs concentration enhanced both hydrophobicity and UV protection.

Aluminum inoculated overlay microstructure for enhanced scratch resistance

Large M7C3 carbides were refined by inoculation with small levels (0, 0.1, 0.5, and 1 wt%) of aluminum in chromium carbide overlay. Multiple cracks were observed in the large primary M7C3 carbides in 0% aluminum sample, while less cracking was observed for refined M7C3 carbides, under similar scratch tests. The refinement mechanism is believed to involve the heterogeneous nucleation of carbides on Al2O3 that has formed prior to M7C3 nucleation. Aluminum is shown to shorten the growth time of primary M7C3 carbides by raising the eutectic temperature. The overlay is slightly softer in the 1% aluminum sample due to a decrease the amount of martensite and an increase of retained austenite in the overlay matrix. A new approach is introduced to refine the primary M7C3 carbides by using a small amount of Al addition without producing new hard phases.

Enhanced scratch resistance of silver nanowire electrodes using a polyether acrylate and silica composite overcoating

• AgNWs were coated with polyether acrylate resin and silica composite (PAR). • PAR coating increased scratch resistance of AgNW electrodes. • No significant degradation of optical and electrical properties of AgNWs was observed. Silver nanowires (AgNWs) are a promising electrode material for next-generation flexible/wearable electronics; however, the industrial use of AgNWs is limited owing to their poor resistance to scratch damage. In this study, a UV-curable polyether acrylate resin and silica composite (PAR) was adopted as an overcoating material on the AgNW electrodes to improve the scratch resistance. The simple formation of PAR overcoating on the AgNW electrodes was possible because of its UV-curable characteristics. In addition, nanoscale silica particles in PAR blocked the penetration of the scratching tip through PAR overcoating, thereby protecting the AgNWs from scratch damage. The PAR-coated AgNW electrodes showed excellent scratch resistance, with no significant degradation in optical transmittance, sheet resistance, and figure of merit. The strategy of using UV-curable PAR composite overcoating will accelerate the actual usage of AgNW electrodes in flexible electronics.

Laser powder bed fusion of hydroxyapatite functionalized Ti-6Al-4V bi-material with potential biomedical applications

• Laser powder bed fusion was utilized to produce HA-Ti64/Ti64 bi-materials. • Addition of HA to Ti64 led to 20 and 22% increase in hardness and yield strength. • The fabricated bi-materials featured enhanced scratch resistance compared to Ti64. • Improvement of mechanical properties were mainly due to the refining of α′ laths. Hydroxyapatite (HA) was added to the Ti-6Al-4V (Ti64) to fabricate Ti64/Ti64-HA bi-materials using the laser powder bed fusion (L-PBF) process. Incorporation of 1wt.%HA into the Ti64 led to a significant enhancement in hardness (20 %), yield strength (22 %), and scratch resistance and mitigated the concerns associated with the relatively poor wear resistance of the Ti64 in load-bearing implant applications. The improved mechanical properties were mainly due to the refining of α′ laths and the second constituent strengthening.

Simultaneous enhancement of anti-friction and wear resistance performances via porous substrate and FeCoNiTiAl high entropy alloy coating of artificial joint materials

It remains an extreme challenge to fabricate artificial joint materials with applicability of mechanical properties compared with bones, superior biocompatibility, anti-friction and wear resistance performances. Here, we report an effective strategy to simultaneously enhance the anti-friction and wear resistance performance of Ti6Al4V substrate through optimizing the porosity and sputtering a high-entropy alloy (HEA) coating. The progressive scratch experiments are carried out to equivalently imitate the scratch deformation process induced by hard particles and evaluate the anti-friction and wear resistance performances, which directly reveal the significantly decreased coefficient of friction (COF) of porous substrate based on suitable pore diameter covered with HEA coating compared with pure Ti6Al4V substrate. The porous design is verified to effectively weaken the stress shielding effect and simultaneously improve the hydrodynamic lubrication. Attributed to the coupling effects of pore structure-induced “flexibility” and HEA coating-induced surface hardening, the composite structure exhibits low COF value, wear volume and enhanced scratch resistance. The design concept would facilitate the development of novel medical implant materials with requirements of anti-friction and wear resistance.

Effects of Pre- and Post-Carburizing Surface Modification on the Tribological and Adhesion Properties of Heat-Resistant KHR 45A Steel for Cracking Tubes.

In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) technology on the tribological properties and scratch-induced adhesion behavior of a heat-resistant KHR 45A steel cracking tube, which is used for the pyrolysis process, were investigated. The main objective of this study is to investigate the effects of pre- and post-carburizing UNSM treatment on the tribological and adhesion performances of carburized domestic KHR 45A (A) steel and to compare the results with the existing carburized Kubota-made KHR 45A steel (B). A carburizing process was carried out on the polished and UNSM-treated KHR 45A steel substrates, which were cut out from the cracking tube, at 300 °C heat exposure for 300 h. The thickness of the carburizing layer was about 10 μm. UNSM technology was applied as pre- and post-carburizing surface treatment; both reduced the friction coefficient and wear rate compared to that of the carburized KHR 45A steel substrate. It was also found that the application of UNSM technology increased the critical load, which implies the improvement of adhesion behavior between the carburizing layer and the KHR steel substrate. The application of UNSM technology as pre- and post-carburizing surface treatment could help replace carburized Kubota-made KHR 45A steel (B) thanks to the improved tribological performance, enhanced scratch resistance, load bearing capacity, and adhesion of domestic KHR 45A (A) steel.

Effect of reduced graphene oxide overcoating on scratch resistance of Ag nanowire electrodes

In this study, the effect of reduced graphene oxide (rGO) overcoating on the scratch resistance of Ag nanowire electrodes was explored for the first time. By performing nanoscratch tests on the nanowire electrodes with and without the rGO overcoating, the lateral forces imposed on the samples were measured when the nanoscale tip was moved laterally; these forces were correlated to the scratch resistance. The lateral forces of the Ag nanowire electrode with an rGO overcoating were significantly higher than those of the uncoated electrode, indicating an increased resistance to the lateral movement of the tip and thus an enhanced scratch resistance. Furthermore, scanning probe microscope images showed that the Ag nanowire electrode without an rGO overcoating exhibited wider scratches after testing than those observed at the coated electrode. These results confirmed that rGO overcoating is effective for enhancing the scratch resistance of Ag nanowire electrodes.

The Role of POSS Functionality on Induced Deviation of Nano and Micromechanical Properties of UV Curable Urethane Acrylate Nanocomposite Coatings

The inorganic-organic hybrid coatings based on UV curable urethane acrylate contained two types of polyhedral oligomeric silsesquioxane (POSS) were prepared. The hydroxyl functionalized POSS nanoparticles, pristine POSS, and the one modified by acrylic acid utilized to study the effect of nanoparticle content and its functionality on ultimate mechanical properties of the hybrid coatings. The nanomechanical properties and scratch resistance of nanocomposite coatings were evaluated with nanoindentation and nanoscratch techniques, respectively. Consequently, the results compared with previously obtained DMTA data. The results revealed that by embedding acrylic acid modified POSS, the surface hardness and elastic modulus improved. Further increasing acrylic acid modified POSS content to 5%, the surface elastic modulus and hardness improved to 37% and 35%, respectively, relative to neat coating and also the enhanced scratch resistance was observed. Furthermore, the discrepancy between the surface elastic modulus and bulk elastic modulus was rationalized and the contributed parameters that led to this deviation such as pile-up area, holding time and hydrostatic stress was investigated. The results showed that apart from the inefficiency of Oliver and Pharr method to precisely evaluate the nanomechanical properties of hybrid coatings, the targeted placement of POSS nanoparticle is responsible for this disparity between surface mechanical properties and its bulk values.

The effect of individual elements of alkali aluminosilicate glass on scratch characteristics: A molecular dynamics study

Flaws on glass surfaces significantly reduce mechanical strength by concentrating applied stresses on their tips. Since these surface defects are formed by surface contact loading, such as scratching, it is crucial to enhance scratch resistance for high mechanical strength. In this regard, we investigate contributions of individual elements of alkali aluminosilicate glass (15Na2O∙5MgO∙11Al2O3∙69SiO2) to surface deformations during scratching by utilizing molecular dynamics simulations. It is found that the friction coefficient is inversely proportional to the amount of elastic deformation. Analyses of local atomic structure demonstrate that Mg and Al mainly contribute to the elastic response, whereas Na tends to heavily participate in plastic deformation. Chemical strengthening of glass further enhances the elastic behavior of Mg and Al and alters the characteristic of alkali elements from plastic to elastic participation. Atomic-level understanding of individual roles of glass elements is expected to contribute to developing advanced glasses with high surface damage resistance.

Scratch Resistance of Flexible Carbon Fiber‐Reinforced Polymer Composites Improved by Atmospheric Pressure Plasma Polymerized‐Organosilicon Oxide Films

An improvement on the scratch resistance of flexible carbon fiber‐reinforced polymer composites (FCFRPCs) has been undertaken by deposition of organosilicon oxide (SiOxCy) films. The SiOxCy films are synthesized using a low temperature‐atmospheric pressure‐plasma polymerization method with an atmospheric pressure plasma jet (APPJ) at various substrate distances. SiOxCy thin films are rapidly deposited onto FCFRPCs at a short exposed‐duration of 150 s with an APPJ. The precursor tetramethyldisiloxan (TMDSO) vapors are mixed with air gases, injected into the air plasma jet of APPJ, and sprayed onto FCFRPCs at room temperature (~23°C) at atmospheric pressure. The scratch resistance of FCFRPCs is meaningfully improved from an overpowering occurrence of scratching (100%) on as‐received FCFRPC to an overall absence of scratching (0%) on SiOxCy film deposited FCFRPC against the steel wool for up to 62 cycles at a 100 g loading. The enhanced scratch resistance of FCFRPCs by APPJ‐synthesized SiOxCy films is strongly dependent on the increased nanoindentation hardness (of up to 1.60 GPa), the increased surface hardness (of up to 7H), and the decreased surface roughness (of up to 6.5 nm for the roughness of the standard deviation from the height mean Rms and 2.5 nm for the roughness of the mean deviation from the height mean Ra), respectively. How the critical films characteristics affect the increased surface hardness and the decreased surface roughness for APPJ‐synthesized SiOxCy films are discussed. POLYM. COMPOS., 40:E1893–E1902, 2019. © 2018 Society of Plastics Engineers

The role of cross-linking in the scratch resistance of organic coatings: An investigation using Atomic Force Microscopy

Understanding how the composition of organic coatings influences their ability to resist surface damage during use remains a challenge. A relevant potential influence is that of cross-linking density. This parameter is frequently used for tailoring the mechanical properties of organic coatings and it manifests itself in terms of scratch resistance. However, the mechanisms that influence scratch resistance are not fully understood. From a thermodynamic perspective, wear of coatings is related to their ability to dissipate friction energy. Hence, it would be reasonable to assume that cross-linking influences the scratch resistance of coatings by influencing their viscoelasticity, as this is one of the parameters that define energy dissipation during shear. This hypothesis was investigated by studying two similar waterborne polyurethane coatings that have different cross-linking properties. The multiple abilities of Atomic Force Microscopy (AFM) were used to characterize the coatings’ scratch resistance, frictional properties, stiffness, adhesiveness and viscoelasticity. Significantly, it was found that monitoring the thermal noise of AFM cantilevers in contact with the coatings was sensitive enough to quantify the effects of cross-linking on their viscoelasticity. Based on this work, cross-linking is proposed to enhance scratch resistance by elastically storing, and eventually releasing, part of the mechanical energy that was transferred to the coatings during shear.

Sliding friction on particle filled epoxy: Developing a quantitative model for complex coatings

Epoxy resins represent an important class of thermosetting polymers that are extensively used in demanding applications like in scratch resistant coatings. Usually fillers, either hard (inorganic) or soft (rubbery), are added. Here we test hard and soft particle-filled epoxy systems in single asperity sliding friction experiments, and analyze the results with the hybrid numerical-experimental approach presented earlier. The focus is on the detailed modeling of the local deformation processes and it is confirmed that a rate-independent friction model proves appropriate to quantitatively model this complex process. The constitutive framework developed for amorphous thermoplastic polymers adequately describes also these thermoset systems. The materials response during scratching is likewise. Hard fillers decrease the penetration of the indenter into the surface, and consequently enhance scratch resistance; they cause the lateral friction force to decrease, since less material flows in front of the indenter tip. Soft fillers increase the penetration into the surface, according to expectations, but surprisingly also decrease the friction force.Simulations do not predict this, and suggest an alternative explanation. Migration of rubber particles during sample preparation to the surface could have occurred. Adding a thin rubbery layer to the surface makes the model quantitative, but SEM and TEM pictures of the cross-sections do not confirm this phase separation and instead show the presence of a large number of very small voids. Including these voids in the modeling allows to predict the penetration depth into the surface and lateral force quantitative for all sliding speeds.

POSS functionalized with mixed fluoroalkyl and methacryloxy substituents as modifiers for UV-curable coatings

UV-curable acrylate-based coatings were modified by copolymerization of base resins with polyhedral oligomeric silsesquioxanes (POSS) containing four methacryloxy and four fluoroalkyl substituents in one molecule (4M4F-POSS), giving hybrid organic–inorganic coatings. Such modifiers are covalently linked to the matrix (by methacryloxy groups) preventing them from exuding onto the surface, and fluoroalkyl substituents (along with the POSS cages) improve scratch resistance and hydrophobicity. Two types of POSS derivatives differing with the length of the fluoroalkyl chain were tested. These compounds were applied in two types of formulations: wood-derived and aluminum substrates. Modification of the coatings led to a substantial increase in the hydrophobicity and enhanced scratch resistance after incorporation of only 1.5 wt% of the modifier. Water contact angle increased by up to 14–160% of the initial value, whereas the scratch hardness for the first surface stripping improved by about 30–170% in the presence of 5 wt% of POSS. The latter can be associated with the increase in the surface sliding properties caused by the presence of fluoroalkyl substituents of the modifier. Better results were obtained for POSS containing shorter fluoroalkyl substituents.

The Potential of Functionalized Ceramic Particles in Coatings for Improved Scratch Resistance

The top layer of a typical high pressure floor laminate (HPL) consists of a melamine formaldehyde (MF) impregnated special wear layer (overlay) with alumina particles. This top layer plays a crucial role in determining the mechanical properties of the laminate. For HPLs, scratch resistance and scratch visibility are particularly important properties. This study aimed to improve the mechanical properties, particularly the scratch resistance, by adjusting the composition of the overlay. Laminates containing alumina particles were prepared and tested. These alumina particles were additionally functionalized with a silane coupling agent to ensure better adhesion between the particles and the resin. The functionalized particles led to enhanced scratch resistance of the laminates as well as improved dispersion of the particles within the resin. Micro scratch testing revealed that by using functionalized particles, the scratch surface damage was reduced and the recovery characteristics of the surface layer were improved. Higher scratch resistance and scratch hardness were thus obtained, along with a reduced scratch visibility.

Down-conversion particles as internal UV-source assist in UV-curing systems: Physical and mechanical properties of UV-curable micro-composites

UV-curable composites always suffer from low conversion due to the low penetration depth of photons as a result of absorption of light by fillers. Herein, down-conversion particles were introduced as mineral materials within the composites to observe the alteration in final conversion along with some physical and mechanical properties. FT-IR, DMTA, micro-indentation, pendulum hardness, scratch resistance, and surface roughness analysis exhibited no reduction in the photopolymerization process in all the composites, and enhanced scratch resistance up to 5% filling. Storage modulus and cross-linked density were increased up to 5% loading, and enhanced micro-hardness up to 5% loading and decreased in 10% loaded composites. However, the surface hardness decreased because of increased surface roughness due to the addition of micron-sized fillers.