Interfacial chemistry of UHMWPE fiber composites: surface modification, adhesion mechanisms, impact performance, and implications for lightweight sports protection

1 Introduction

Lightweight sports protective equipment spans rigid or semi-rigid shell systems, particularly helmets, and flexible body protectors such as anti-stab/puncture textiles. Both must provide protection against blunt impact, cutting, or puncture at low areal density, but their structural requirements differ: rigid shells require effective load spreading and control of linear and rotational impact response, whereas flexible protectors must preserve drapability, yarn mobility, and wearer comfort (Li et al., 2019; Bottlang et al., 2020; Bhudolia et al., 2021; Zhang et al., 2023). Protection in multilayer anti-stab fabrics and shear-thickening-fluid-impregnated ultra-high-molecular-weight polyethylene (UHMWPE)/Kevlar systems depends not only on fiber strength but also on fabric architecture, yarn mobility, impactor geometry, and reinforcement–matrix interactions (Li et al., 2019; Zhang et al., 2023). UHMWPE fibers are particularly attractive because gel spinning and extensive drawing produce a highly oriented semicrystalline structure with exceptional specific strength, modulus, toughness, and energy-absorption capacity at low density (Smith and Lemstra, 1980; Berger et al., 2003). Their protective response, however, remains strongly dependent on matrix chemistry and structural configuration (Wang et al., 2023).

The principal limitation is the chemically inert UHMWPE surface, which is dominated by non-polar C–C and C–H bonds and exhibits low surface energy, poor wettability, and limited affinity for polar matrices (Moon and Jang, 1999). Weak interfacial bonding restricts stress transfer and promotes premature debonding, yarn slip, and delamination. Oxygen-plasma treatment can increase surface polarity and roughness, improve interfacial shear transfer, and reduce impact-damage area and indentation depth, demonstrating that surface chemistry directly influences macroscopic damage evolution (Wu et al., 2022). Nevertheless, available evidence does not support treating maximum adhesion as a universal design objective because impact energy is also dissipated through matrix deformation, delamination, interfacial sliding, fiber pull-out, and fiber rupture (He et al., 2022). In PPTA/UHMWPE laminates, an intermediate level of interlayer adhesion produced lower ballistic failure and indentation than both more weakly constrained and more strongly bonded configurations, providing direct evidence of an adhesion optimum for that specific architecture and loading condition (Zhu et al., 2023).

Physical activation, chemical grafting, polymer coatings, and bio-inspired interlayers have been developed to introduce reactive groups and tailor interphase chemistry and stiffness. Representative approaches include hydroxyethyl-methacrylate grafting, plasma-assisted polypyrrole deposition, CNT-modified polydopamine sizing, and nanoparticle-reinforced hierarchical interphases (Jin et al., 2016; Zhang et al., 2018; Shanmugam et al., 2019; Wang et al., 2022). Two distinct evidence gaps remain. First, surface chemistry, static interfacial adhesion, and impact performance are commonly characterized separately or at different structural scales, limiting direct chemistry–adhesion–impact correlation and causal attribution. Second, long-term reliability is much less systematically assessed, despite the sensitivity of UHMWPE to weathering-induced oxidation and chain scission and to temperature-dependent changes in deformation and penetration resistance (Li et al., 2012; Forster et al., 2015; Cao et al., 2021).

A targeted literature search was conducted in Web of Science, Scopus, and Google Scholar for studies published or available online until 30 June 2026. The selected keywords were organized into two complementary Boolean search strings, and explicit inclusion and exclusion criteria were applied during literature screening: (“UHMWPE” OR “ultra-high molecular weight polyethylene”) AND (fiber OR fibre OR fabric OR composite) AND (“surface modification” OR interface OR interphase OR adhesion OR graft OR plasma OR coating), and (“UHMWPE” OR “ultra-high molecular weight polyethylene”) AND (fiber OR fibre OR fabric OR laminate OR composite) AND (impact OR ballistic OR stab OR puncture OR helmet OR “sports protect”). Studies were considered when they addressed UHMWPE fibers, fabrics, or fiber-reinforced composites and provided information on surface or interphase modification, interfacial behavior, fiber integrity, or impact/penetration response relevant to the scope of this review. Studies focused solely on bulk UHMWPE, biomedical applications unrelated to fibrous protection, or reports lacking sufficient information on treatment, interface, or mechanical response were excluded. Duplicate records were removed before title and abstract screening, followed by full-text assessment of potentially relevant studies. Studies meeting these criteria were retained for qualitative synthesis, with ballistic and coupon-level studies included where they provided mechanisms relevant to lightweight sports-protection systems. For evidence-level assessment, the retained primary experimental studies were additionally classified according to the highest level of validation achieved as interface-level (I), composite/impact-level (C), or sports-equipment/system-level (E); review articles and background references were excluded from this count.

The temporal distribution of the screened literature is summarized in Figure 1A, with separate trends for UHMWPE interface/surface modification, impact and ballistic response, and sports-equipment-related studies. The comparison shows the broader development of interface- and impact-oriented research while placing the more limited sports-equipment-specific evidence in quantitative context.

Several recent reviews have addressed different aspects of UHMWPE composites, including fiber-surface modification and interfacial properties (Chhetri and Bougherara, 2021), fiber–polymer compatibilization and mechanical performance (Shelly et al., 2024), and surface-modification strategies across broader UHMWPE applications (He et al., 2024). Impact-oriented reviews have instead concentrated primarily on ballistic fabrics and composites, with emphasis on energy absorption and associated damage mechanisms (Joshi et al., 2024). Within sports-protection research, rigid and flexible UHMWPE architectures impose distinct structural and interfacial requirements. Rigid or consolidated shell-like composites depend more strongly on matrix-supported load spreading and interlaminar integrity, whereas flexible textile protectors rely more strongly on yarn mobility, inter-yarn friction, layer sliding, and conformability; consequently, an increase in interfacial constraint cannot be assumed to benefit the two protector classes in the same manner (Li et al., 2019; Bottlang et al., 2020; Wang et al., 2023; Zhang et al., 2023). The existing literature has therefore largely treated interface chemistry, impact response, and equipment architecture separately. Against this background, the present mini review links surface chemistry and interphase structure to adhesion and protective response across scales, evaluates how these mechanisms translate to rigid and flexible sports protectors, and separately assesses the limited evidence on durability and environmental reliability.

2 Interfacial challenges of UHMWPE fiber composites

2.1 Surface and molecular characteristics of UHMWPE fibers

Gel spinning and multistage drawing generate highly oriented, extended-chain crystalline domains connected by amorphous regions and load-bearing tie molecules, providing exceptional axial-specific strength and modulus but limited transverse cohesion governed by van der Waals interactions, chain slip, and fibrillar separation (Smith and Lemstra, 1980; Berger et al., 2003). The UHMWPE surface is correspondingly non-polar, chemically inert, and low in surface free energy, while dense chain packing and high crystallinity restrict resin wetting, molecular interdiffusion, and chemical reaction. Surface pits introduced by oxygen plasma can enhance mechanical interlocking and shift failure from the interface toward the fiber interior (Moon and Jang, 1999), whereas corona activation followed by poly(vinyl alcohol)–glutaraldehyde deposition increases oxygen-containing groups and epoxy adhesion (Han et al., 2020). Thus, interfacial performance is controlled jointly by surface chemistry, fibrillar morphology, and structural anisotropy.

2.2 Matrix-dependent interfacial requirements

The optimum interphase depends on matrix polarity, stiffness, curing kinetics, molecular mobility, and deformation capacity. Thermosetting matrices require effective pre-gelation wetting and stable chemical anchoring after curing; amphiphilic polymer brushes can bridge the non-polar fiber surface and polar resin network, although overly rigid interlayers may create modulus discontinuities and stress concentrations (Wang et al., 2026). Elastomeric matrices instead require compliant interfaces that suppress uncontrolled fiber slip while accommodating large cyclic deformation, as demonstrated in UHMWPE-reinforced polyurethane/epoxy interpenetrating networks and polydopamine–aminosilane-modified fiber–rubber systems (Lin et al., 2007; Liu et al., 2024). Thermoplastic interfaces are additionally governed by melt viscosity, processing temperature, chain interdiffusion, and crystallization. Bromination alters both surface functionality and HDPE transcrystallinity (Vaisman et al., 2003), CNT-modified polydopamine improves compatibility in chemically dissimilar systems (Shanmugam et al., 2019), and self-reinforced UHMWPE/HDPE composites require a narrow consolidation window to prevent fiber melting, orientation relaxation, and misalignment (Qiao et al., 2024).

2.3 Trade-offs in interfacial engineering

Two coupled trade-offs define UHMWPE interfacial design. First, increasing activation can improve surface polarity and roughness but damage the highly oriented fibrillar structure. Chromic-acid etching enhanced interfacial shear strength at the expense of fiber tensile properties (Silverstein and Breuer, 1993), while mixed O₂/N₂ plasma treatment followed by in situ PPy growth increased UHMWPE/epoxy IFSS from 3.45 to 15.75 MPa (+357%) but reduced single-fiber tensile strength from 7.156 to 6.633 GPa (−7.3%) (Yang et al., 2023). Second, maximum adhesion does not necessarily maximize impact protection. In PPTA/UHMWPE laminates, moderate interlayer adhesion after a 1-min plasma treatment reduced the ballistic failure rate from 0.17 to 0.05 and mean indentation from 26.10 to 21.71 mm, whereas further adhesion increase reversed the improvement (Zhu et al., 2023). Complementary studies also indicate treatment-dependent optima: optimized oxygen plasma simultaneously improved interface shear performance and reduced impact damage (Wu et al., 2022), while ZnO-nanowire/UHMWPE–epoxy IFSS peaked at +135% after a 30-s plasma pretreatment, although impact performance was not evaluated (Steinke and Sodano, 2022). Together, these results support an application-specific operating window that balances stress transfer, interfacial toughness, post-debonding friction, and fiber integrity.

3 Surface modification strategies and interphase construction

UHMWPE modification should increase interfacial reactivity without compromising fibrillar integrity or adding excessive mass and stiffness. Physical activation, wet-chemical functionalization, and engineered interlayers differ mainly in modification depth, stability, compliance, and scalability.

3.1 Physical activation

Plasma, corona, UV/ozone, laser, and ionizing irradiation generate radicals, oxygenated groups, crosslinks, and shallow roughness. Oxygen plasmas functionalize directly, whereas inert-gas treatments form radicals that oxidize in air. Both improve wetting and mechanical anchoring, although outcomes depend on treatment atmosphere and matrix chemistry (Oosterom et al., 2006; Huang et al., 2013). Atmospheric plasma and corona suit continuous textile processing because they require little or no liquid reagent. Their processing window is narrow: insufficient exposure yields limited activation, whereas over-treatment causes fibrillar erosion, chain scission, and strength loss. Hydrophobic recovery further requires prompt impregnation or chemical stabilization (He et al., 2018; Dominguez-Lopez et al., 2021). Quantitative studies illustrate both the effectiveness and limitations of plasma activation. Ar plasma reduced the UHMWPE textile water contact angle from ∼80° to 28° and increased peel strength from 0.6 to 4.6 kgf in−1 while generating additional surface anchoring features (Huang et al., 2013). Atmospheric plasma similarly reduced contact angle from ∼85° to 40° and increased roughness by ∼6 nm, but the contact angle recovered to 66°–73° after 90 days (Dominguez-Lopez et al., 2021). Plasma activation therefore offers low-mass enhancement of wettability and anchoring but remains limited by surface aging and treatment-induced fiber damage.

3.2 Wet-chemical modification and grafting

Unlike shallow physical activation, oxidative etching removes weak surface layers while introducing polar groups and microscale roughness.

Coupling agents and graft polymerization offer greater matrix specificity. Silanes require pre-activated polar sites and controlled hydrolysis and curing, whereas photoinduced grafting introduces carboxyl-, amide-, or epoxy-reactive chains (Zhang et al., 2009; Li et al., 2011). The graft ratio alone is insufficient: excessive thickness, weak anchoring, or residual homopolymer can form a weak boundary layer. Sequential activation–grafting can stabilize transient radicals as matrix-compatible chains, improving adhesion, fatigue resistance, and aging stability, but remains sensitive to graft density, coating uniformity, and reaction control (Wang et al., 2018; Yin et al., 2023).

3.3 Bio-inspired and functional interlayers

Functional interlayers offer an alternative to direct surface activation. Polydopamine (PDA) provides an aqueous primer for secondary grafting and crosslinking. Although its initial attachment to untreated UHMWPE may rely partly on adsorption, epoxy- or amine-functionalization improves compatibility with rubber and other reactive matrices (Sa et al., 2015; Hu et al., 2017).

Hierarchical interlayers combine chemical interaction with mechanical anchoring. CNT-modified PDA increases interfacial area, roughness, and crack bridging, whereas PDA-assisted ZnO enhances polar interaction and sliding resistance; excessive loading may stiffen yarns, add mass, and create stress concentrations (Shanmugam et al., 2019; Fang et al., 2022). Multilayer coatings can separate fiber anchoring from matrix interaction and produce graded stress transfer (Chhetri et al., 2022). Diazirine-functional polymers enable direct covalent modification through carbene insertion into polyethylene C–H bonds without severe pre-oxidation, although cost, activation, durability, and continuous-processing compatibility remain unresolved (Nazir et al., 2024).

3.4 Comparative assessment

Table 1 compares representative UHMWPE interfacial-modification studies using the reported treatment conditions, matrix or structural configuration, interfacial response, fiber-strength retention, impact-related performance, durability, and processing constraints. Because the studies employ different matrices, interface tests, specimen architectures, and loading conditions, percentage changes are reported relative to the corresponding untreated or control condition within each study and should not be interpreted as directly normalized rankings across studies. Parameters not evaluated in the original study are identified as not reported (NR).

TABLE 1. Comparison of UHMWPE interfacial modification strategies for lightweight sports-protective composites.

NR, not reported in the cited study. Percentage changes refer to the corresponding untreated or control condition within each individual study. Because matrix chemistry, interfacial test method, specimen architecture, treatment protocol, and loading condition differ substantially among studies, the numerical values are intended for within-study comparison and should not be interpreted as normalized cross-study rankings. I, interface-level evidence based mainly on surface characterization or micromechanical/interfacial testing; C, composite-, laminate-, or fabric-level mechanical, impact, ballistic, durability, or repeated-loading evidence. Evidence level indicates the highest validation level reached by the cited study. Composite-level evidence should not be interpreted as direct validation of sports-equipment performance.

Bold values indicate the optimal results reported in each study.

The modification routes involve distinct trade-offs. Physical activation adds negligible mass and is compatible with continuous textile processing but is limited by hydrophobic recovery, narrow process windows, and fibrillar erosion (Huang et al., 2013; Dominguez-Lopez et al., 2021). Wet-chemical and grafting routes offer stronger matrix-specific anchoring but introduce reagent, uniformity, processing-complexity, and fiber-damage concerns (Silverstein and Breuer, 1993; Li et al., 2016; Wang et al., 2018; Yin et al., 2023). Bio-inspired and hierarchical interlayers provide tunable chemistry, anchoring, and crack bridging at the cost of added mass, local stiffening, dispersion control, and processing complexity (Shanmugam et al., 2019; Chhetri et al., 2022; Fang et al., 2022). These penalties are particularly important for flexible protection, whereas rigid shells can tolerate stronger and more continuous interphases.

The comparison reveals a clear imbalance in the available evidence. Large improvements in interfacial metrics are frequently reported, whereas fiber-strength retention, dynamic impact response, and especially durability are assessed much less consistently. The magnitude of an adhesion increase alone also does not predict protective performance: values such as IFSS, TFBT strength, H-pull force, and inter-yarn friction describe different interfacial processes and cannot be ranked directly across material systems. Their implications therefore need to be interpreted together with fiber integrity, post-debonding sliding, structural architecture, and loading mode.

4 Adhesion mechanisms and multiscale characterization

In this study, “interface” encompasses fiber–matrix, inter-yarn, and interlaminar contacts, which govern local stress transfer, yarn sliding, and delamination, respectively. The fiber–matrix boundary is better treated as a finite interphase whose composition, morphology, thickness, and mechanical gradient control stress transfer, crack initiation, debonding, and post-debonding friction. Raman mapping of UHMWPE/LDPE composites revealed an oriented and crystallized transition region in the adjacent matrix, confirming that interfacial effects extend beyond direct molecular contact (Bai et al., 2022).

4.1 Chemical and physical adhesion mechanisms

Untreated UHMWPE adheres mainly through dispersion forces, limited mechanical contact, and friction. Oxidation, grafting, and functional coatings introduce polar or reactive groups that enable covalent bonding, hydrogen bonding, dipolar interactions, and acid–base interactions. PVA–glutaraldehyde, epoxy-functionalized PDA, and plasma-assisted polypyrrole improve compatibility with epoxy or rubber and may reduce fiber–matrix stiffness mismatch (Sa et al., 2015; Jin et al., 2016; Han et al., 2020).

Pits, grooves, fibrils, and hierarchical nanostructures further enhance mechanical interlocking. Oxygen plasma can shift failure from the interface toward the fiber interior, whereas ZnO nanowires increase contact area and sliding resistance; both exhibit treatment-dependent optima (Moon and Jang, 1999; Steinke and Sodano, 2022). In thermoplastics, chain interdiffusion, entanglement, interfacial crystallization, and friction may contribute as strongly as chemical bonding. Adhesion should therefore be interpreted as a coupled chemical–morphological–mechanical response.

4.2 Multiscale characterization and mechanical evidence

No single technique can establish interfacial causality. XPS/FTIR, SEM/AFM, and Raman/DSC/XRD probe surface chemistry, morphology and coating continuity, and interphase orientation or crystallization, respectively. Their combined use is essential because wettability alone cannot distinguish chemical activation from roughness-induced effects, as shown for irradiated UHMWPE fibers (He et al., 2018).

Microbond and single-fiber pull-out tests quantify local debonding, but apparent interfacial shear strength depends on specimen geometry, residual stress, matrix deformation, and loading rate and is therefore not an intrinsic constant. Complete load–displacement curves are more informative because they separate crack initiation, progressive debonding, and frictional sliding. Functionalized graphitic nanofibers, for example, increased peak force, debonding energy, and frictional work in UHMWPE/epoxy interfaces (Salehi-Khojin et al., 2007). Accordingly, interfacial shear strength should not be interpreted in isolation; it should be evaluated together with post-treatment fiber tensile strength, debonding energy, frictional work, yarn pull-out, and rate-dependent composite response. This requirement is consistent with broader fiber-reinforced systems, in which the intrinsic mechanical properties of the reinforcement are characterized independently before composite-level performance is interpreted (Di Chicco et al., 2025).

4.3 Establishing chemistry–adhesion causal relationships

Robust attribution requires untreated and process-control groups, treatment gradients, and concurrent measurements of chemistry, morphology, fiber-strength retention, debonding, friction, and laminate damage. The preferred evidence chain is as follows:

processing → interphase structure → debonding and friction → laminate damage → impact performance.

Studies that jointly vary treatment parameters and evaluate surface, interfacial, and impact responses provide stronger mechanistic evidence than contact-angle or adhesion data alone (Wu et al., 2022). Static adhesion must also be interpreted cautiously because moderate interlayer bonding can improve impact resistance, whereas excessive bonding may suppress beneficial delamination and sliding (Zhu et al., 2023).

5 From interfacial chemistry to impact performance

Representative studies show that interfacial modification affects impact response through fiber–matrix stress transfer, interphase architecture, inter-yarn friction, and interlayer constraint, with the relative contribution of these pathways depending on treatment severity and structural configuration (Shanmugam et al., 2019; 2020; Steinke and Sodano, 2021; Wu et al., 2022; Zhu et al., 2023). Figure 1 synthesizes these relationships into an application-specific operating-window framework while distinguishing mechanistic evidence from direct sports-equipment validation.

5.1 Impact damage and performance metrics

Impact generates compression, through-thickness shear, and tensile-wave propagation, dissipating energy through fiber deformation and rupture, matrix deformation, debonding, delamination, and frictional sliding. Tomography and high-speed three-dimensional digital image correlation show that these mechanisms act concurrently and vary with loading direction and laminate architecture (He et al., 2022; Zhu et al., 2024).

These loading modes impose distinct rates, contact geometries, boundary conditions, and deformation fields. Ballistic impact produces highly localized high-rate tensile, shear, and delamination damage (He et al., 2022), whereas low-velocity impact is governed more strongly by plate-scale bending, indentation, and architecture-dependent deformation (Hazzard et al., 2017). Stab and puncture loading emphasize local cutting, yarn separation, friction, and pull-out (Li et al., 2019), while sports-related blunt or oblique impact additionally couples protector geometry, liners, retention, and rotational response (Bottlang et al., 2020). Evidence is therefore transferred here at the level of specific mechanisms rather than by assuming equivalent loading regimes or performance metrics.

Taken together, the quantitative comparisons in Table 1 are consistent with a conceptual framework comprising three broad interfacial regimes. Insufficient constraint promotes premature debonding or excessive sliding before the reinforcement is fully engaged, whereas intermediate constraint permits effective stress transfer while retaining delamination, pull-out, and frictional sliding as dissipative processes. Further constraint can suppress these mechanisms and concentrate damage locally. Figure 1C summarizes this behavior as an application-specific operating window. Its position and width are expected to vary with matrix chemistry, interphase toughness, architecture, loading rate, and impact mode, and the schematic should, therefore, not be interpreted as a universal quantitative adhesion curve.

Protection should be assessed through load attenuation, energy management, deformation, and residual damage, rather than a single metric. High stiffness may increase transmitted force, whereas high apparent absorption may reflect irreversible damage. Thermoplastic UHMWPE laminates further show that matrix chemistry and ductility influence impact load, deformation, energy absorption, structural integrity, and damage evolution (Kazemi et al., 2020). Penetration data should be normalized by mass, thickness, or areal density and reported with impactor geometry, loading rate, boundary conditions, and failure mode, particularly because flexible and rigid UHMWPE composites respond differently (Wang et al., 2023). A minimum dataset should include incident and absorbed energy, transmitted force, maximum deformation, damage area, residual performance, areal density, thickness, and conditioning history.

5.2 Translation to lightweight sports protective equipment

These loading-mode distinctions define the boundary for translating material- and laminate-level evidence to lightweight sports protective equipment. Evidence-level classification of the retained primary experimental studies showed that [I%] remained at the interface level, [C%] reached composite/impact-level validation, and only [E%] reached sports-equipment/system-level validation. Much of the available UHMWPE evidence still derives from ballistic panels or flat coupons and is therefore primarily mechanistic, whereas sports protectors additionally involve curvature, compliant foams or liners, fastening and retention systems, oblique contact, repeated loading, flexibility, and comfort constraints. Ballistic and coupon-level results are consequently used here to identify transferable mechanisms rather than as direct validation of sports-equipment performance.

For helmets, normal-impact attenuation alone is insufficient because oblique impacts generate linear and rotational head motion; testing should therefore evaluate complete shell–liner–retention–headform systems (Bottlang et al., 2020). Ductile thermoplastic and hybrid shells can provide more progressive energy absorption than brittle configurations (Bhudolia et al., 2021).

Flexible protectors require a different balance among fiber tension, yarn mobility, inter-yarn friction, layer sliding, and drapability. UHMWPE-containing martial-arts fabrics must combine puncture resistance with low areal density and comfort, while shear-thickening-fluid-treated UHMWPE/Kevlar fabrics show that reinforcement–impregnant interactions also govern protection (Li et al., 2019; Zhang et al., 2023). Durability validation should include temperature, moisture or perspiration, ultraviolet exposure, abrasion, repeated flexing, cleaning, and multiple-impact conditioning because weathering and thermal conditions can alter UHMWPE chemistry, tensile retention, deformation, and penetration resistance (Li et al., 2012; Forster et al., 2015; Cao et al., 2021).

Interfacial strategies should ultimately be judged by protection normalized by mass or thickness together with residual performance, flexibility, durability, and manufacturability. Rigid shells favor thin, well-anchored, fracture-tough interphases, whereas flexible textiles require compliant or discontinuous interphases that preserve controlled sliding and drapability. The target is an application-specific operating window rather than maximum adhesion.

6 Discussion and future directions

UHMWPE interfacial engineering is therefore not a single-variable optimization problem. Across fiber–matrix, inter-yarn, and interlaminar scales, improved stress transfer must be balanced against fiber preservation, controlled debonding, delamination, pull-out, and frictional dissipation (Wang et al., 2022; Steinke and Sodano, 2021; 2022; Wu et al., 2022; Zhu et al., 2023). The preferred interphase is consequently application- and rate-dependent rather than that providing the maximum isolated adhesion value.

Cross-study comparison remains difficult because fiber grade, sizing history, matrix chemistry, treatment conditions, architecture, and test geometry are rarely standardized. Contact-angle, microbond, pull-out, peel, and interlaminar tests probe different interfacial processes and should not be treated as interchangeable. More importantly, surface chemistry is often characterized separately from dynamic composite behavior, preventing direct attribution of impact improvements to specific mechanisms. Future studies should establish a continuous processing–structure–performance chain by combining interphase characterization with rate-dependent debonding, fiber-strength retention, laminate damage, and residual protection. High-speed digital image correlation and X-ray computed tomography can resolve transient deformation and internal failure but remain insufficiently integrated with chemical and micromechanical measurements (He et al., 2022; Zhu et al., 2024).

Application-level validation remains a major gap because coupon- and ballistic-level mechanisms do not capture the combined effects of protector geometry, retention, repeated loading, comfort, and environmental exposure. Future studies should therefore integrate equipment-level impact testing with durability conditioning and multiscale interfacial characterization (Bottlang et al., 2020; Forster et al., 2015; Cao et al., 2021).

Broader fiber-reinforced systems provide useful methodological analogies, although they should not be treated as direct evidence for UHMWPE surface chemistry. Tensile testing of flax yarns and grids illustrates the importance of characterizing reinforcement mechanical properties independently when assessing composite improvements (Di Chicco et al., 2025). Reviews of hemp-fiber treatments similarly emphasize that adhesion enhancement should be considered jointly with fiber preservation, matrix compatibility, durability, and sustainability (Costa Laktim and Formisano, 2025). Experimental work on jute-reinforced hydraulic-lime mortar further reinforces the general principle that composite performance reflects coupled fiber–interface–matrix behavior rather than reinforcement properties in isolation (Formisano et al., 2020).

Future interphases should combine thin covalent anchoring layers with compliant outer regions, reversible interactions, or sacrificial bonds to preserve stress transfer while enabling controlled damage. Spatially graded treatments may provide strong bonding in impact-critical regions without sacrificing flexibility and ventilation. Direct C–H functionalization using diazirine-based primers is promising but requires validation of cost, coating mass, durability, and continuous processing (Nazir et al., 2022). Standardized multiscale workflows should also account for the finite interphase, including matrix orientation and crystallization beyond the nominal fiber surface (Bai et al., 2022). Ultimately, the preferred interface is not that with the highest isolated adhesion value, but that which best balances protection, controlled damage, durability, comfort, scalability, and environmental responsibility.

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Footnotes

Edited by: Mazeyar Parvinzadeh Gashti, Pittsburg State University, United States

Reviewed by: Antonio Formisano, University of Naples Federico II, Italy

Pankaj Shrivastava, University of South Africa, South Africa

Hongling Yi, East China University of Science and Technology, China