Polypropylene Surface Research Articles

In Situ Growth Strategy to Construct "Four-In-One" Separators with Functionalized Polyphosphazene Coatings for Safe and Stable Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are facing many challenges, such as the inadequate conductivity of sulfur, the shuttle effect caused by lithium polysulfide (LiPSs), lithium dendrites, and the flammability, which have hindered their commercial applications. Herein, a "four-in-one" functionalized coating is fabricated on the surface of polypropylene (PP) separator by using a novel flame-retardant namely InC-HCTB to meet these challenges. InC-HCTB is obtained by cultivating polyphosphazene on the surface of carbon nanotubes with an in situ growth strategy. First, this unique architecture fosters an enhanced conductive network, bolstering the bidirectional enhancement of both ionic and electronic conductivities. Furthermore, InC-HCTB effectively inhibits the shuttle effect of LiPSs. LSBs exhibit a remarkable capacity of 1170.7mAhg-1 at 0.2C, and the capacity degradation is a mere 0.0436% over 800 cycles at 1C. Third, InC-HCTB coating serves as an ion migration network, hindering the growth of lithium dendrites. More importantly, InC-HCTB exhibits notable flame retardancy. The radical trapping action in the gas phase and the protective effect of the shielded char layer in the condensed phase are simulated and verified. This facile in situ growth strategy constructs a "four-in-one" functional separator coating, rendering InC-HCTB a promising additive for the large-scale production of safe and stable LSBs.

Effect of Functionalization of Texturized Polypropylene Surface by Silanization and HBII-RGD Attachment on Response of Primary Abdominal and Vaginal Fibroblasts.

Soft tissue defects, such as incisional hernia or pelvic organ prolapse, are prevalent pathologies characterized by a tissue microenvironment rich in fragile and dysfunctional fibroblasts. Precision medicine could improve their surgical repair, currently based on polymeric materials. Nonetheless, biomaterial-triggered interventions need first a better understanding of the cell-material interfaces that truly consider the patients' biology. Few tools are available to study the interactions between polymers and dysfunctional soft tissue cells in vitro. Here, we propose polypropylene (PP) as a matrix to create microscale surfaces w/wo functionalization with an HBII-RGD molecule, a fibronectin fragment modified to include an RGD sequence for promoting cell attachment and differentiation. Metal mold surfaces were roughened by shot blasting with aluminum oxide, and polypropylene plates were obtained by injection molding. HBII-RGD was covalently attached by silanization. As a proof of concept, primary abdominal and vaginal wall fasciae fibroblasts from control patients were grown on the new surfaces. Tissue-specific significant differences in cell morphology, early adhesion and cytoskeletal structure were observed. Roughness and biofunctionalization parameters exerted unique and combinatorial effects that need further investigation. We conclude that the proposed model is effective and provides a new framework to inform the design of smart materials for the treatment of clinically compromised tissues.

Hydrophilic surface modification of polypropylene by AC-DBD and NS-DBD

Dielectric barrier discharge (DBD) is a method to modify material surfaces by creating low-temperature plasma at atmospheric pressure. However, in comparison to low-pressure discharge, atmospheric DBD has the drawback of uneven surface treatment due to the ease of forming filamentary channels. This limitation hinders the widespread application of DBD technology in material surface modification. In this study, the surface of polypropylene (PP) was treated using high frequency alternating current (AC) and nanosecond (NS) pulsed argon DBDs to improve surface hydrophilicity. The changes of the PP surface hydrophilicity and the treatment uniformity were characterized by water contact angle (WCA) measurement. The relationships between the DBD characteristics, the treatment effect and the treatment uniformity of the PP surface were investigated using electrical and optical diagnostic techniques. The PP material surfaces before and after plasma treatments were evaluated by the physical morphology and chemical composition measurements to examine the influence of DBD on the treatment effect and uniformity on the PP material surface. The findings show that the modification by AC-DBD reduces the WCA of PP material surface by 40°∼50° and exhibits a variance of 1.77, indicating an improvement in hydrophilicity to some extent. Furthermore, the modification by NS-DBD further decreases the WCA of PP material surface, reducing the variance to 1.14. Compared with AC-DBD, NS-DBD has a better uniformity, a higher concentration of active particles in plasma, a greater surface roughness of PP material after treatment, a better hydrophilicity and a more uniform effect with less energy consumption. The results are meaningful to improve the application of DBD in material surface modification and optimize the power source election and operation parameters.

Biofilm-influenced weathering of polypropylene films submerged in field samples from freshwater and marine ecosystems

Polymers in aquatic ecosystems are susceptible to degradation by natural weathering where abiotic factors and biotic factors induce changes to the physiochemical properties of the materials. The extent of plastic weathering depends on both on the material and the location, though few studies have considered the joint effects of abiotic and biotic factors present in different environments on a single plastic material. This study used microscopy, Fourier-Transform Infrared Spectroscopy (FTIR), and goniometry to evaluate biofilm growth through morphological and chemical changes of polypropylene (PP) films incubated in filtered water as a control, lake water, and ocean water. With results from the qualitative and quantitative characterizations, biofilm growth was indicated on all samples by 16 weeks. The most notable changes occurred to films immersed in ocean water as opposed to freshwater or the control. After removal of biofilm, PP degradation was also confirmed. Finally, amplicon sequencing of the 16srRNA gene on samples immersed in ocean water revealed that proteobacteria can survive on polypropylene surfaces without supplement for at least 8 weeks while PP degrades oxidatively. This work suggests that biofilm-influenced degradation can induce, and therefore accelerate polyolefin aging in the environment, especially in the presence of ocean microbial consortia.

Janus Nanofiber Membranes with Photothermal‐Enhanced Biofluid Drainage and Sterilization for Diabetic Wounds

AbstractDiabetic wounds are difficult to heal, and the key to wound healing is exudate management and effective disinfection. Inspired by the asymmetric wettability of Janus‐structured lotus leaves, herein the study has presented the design of a biomimetic asymmetric Janus membrane that integrates unidirectional biofluid drainage and photothermal‐enhanced evaporation/sterilization capabilities for accelerating diabetic wound healing. This Janus membrane is prepared by electrospinning polyacrylonitrile (PAN) nanofiber membrane containing polydopamine (PDA) on the surface of polypropylene (PP) nonwoven membrane. Such PP/PANx%PDA Janus membrane enables antigravity “pumping” of the water from the hydrophobic PP layer to the hydrophilic PANx%PDA layer within 22 s through contact points on the Janus interface. The incorporation of 30 wt% PDA in PAN imparts high photoabsorption and photothermal responsiveness, facilitating continuous volatilization of the exudate, achieving twice the displacement of water, and causing irreversible damage to bacteria. As a result, it effectively alleviates inflammation and cellular fibrosis while promoting collagen deposition due to its structure and antibacterial properties. Impressively, such photothermal‐enhanced Janus membrane achieves an impressive closure rate of 96.7% for diabetic wounds, better than that of (59.8%) for conventional bandages. Therefore, this asymmetric Janus membrane offers a promising alternative for the healing of chronic diabetic wounds.

Preparation of PDMS and PDMS-UiO-66 oxygen-rich membranes and modules for membrane-aerated biofilm reactors.

A membrane-aerated biofilm reactor (MABR) combines membrane technology with biofilm processes and has unique advantages in the treatment of organic wastewater and volatile wastewater. The common membranes for MABR systems usually have relatively uneven pore structures and low bubble point pressure, resulting in unsatisfactory O2 utilization and wastewater treatment efficiency. In this work, polydimethylsiloxane (PDMS) and UiO-66 (a Zr-based metal organic framework) were coated on the surface of a commercial polypropylene (PP) hollow fiber membrane to prepare oxygen-rich MABR membranes and modules, which showed an attractive O2 utilization rate and wastewater treatment efficiency. The bubble points of the PDMS and PDMS-UiO-66 membranes were significantly higher than those of the PP membranes, and the PDMS-UiO-66 membranes had better oxygen enrichment capacity and biological affinity. The optimal PDMS-UiO-66 membrane modules had an O2 permeance of 31.65 GPU (1 GPU = 3.35 × 10-10 mol m-2 s-1 Pa-1), with O2/N2 selectivity of 2.21. The membrane hanging effect and processing capacity for domestic sewage were greatly improved. This study may provide insights and guidelines to fabricate porous mixed matrix membranes and modules in the industry for MABR. The developed products are expected to be applied in the actual separation process.

Gas ultrafine bubbles improve the efficacy of antimicrobials against eliminating fresh and aged Bacillus subtilis biofilms on various dairy processing surfaces

The objective of this research was to study the impact of incorporating gas ultrafine bubbles (UFB) on the efficacy of chlorine and peracetic acid antimicrobial (AM) solutions against Bacillus subtilis biofilms on polypropylene, silicone, and stainless-steel surfaces. B. subtilis biofilms were grown on coupons of various surfaces at 25 °C (for 3 and 30 days for fresh and aged biofilms, respectively) by immersing in B. subtilis inoculated brain heart infusion broth. The AM solutions (50, 100, and 200 ppm chlorine, and 20, 40, and 80 ppm peracetic acid) were prepared from the water incorporated with air, CO2, or N2 UFB. Coupons with biofilms were treated by submerging in AM solutions with or without UFB for 1 min. The AM solutions with CO2 UFB resulted in significantly higher log reductions (2.2–3.7 log CFU cm−2) of fresh and aged B. subtilis biofilms on all surfaces compared to AM solutions without UFB (1.2–2.5 log CFU cm−2).

A Facile Surface Modification Scheme for Medical-Grade Titanium and Polypropylene Using a Novel Mussel-Inspired Biomimetic Polymer with Cationic Quaternary Ammonium Functionalities for Antibacterial Application.

Medical device-associated infection remains a critical problem in the healthcare setting. Different clinical- or device-related methods have been attempted to reduce the infection rate. Among these approaches, creating a surface with bactericidal cationic functionality has been proposed. To do so, a sophisticated multi-step chemical procedure would be needed. Instead, a simple immersion approach was utilized in this investigation to render the titanium and polypropylene surface with the quaternary ammonium functionality by using a mussel-inspired novel lab-synthesized biomimetic catechol-terminated polymer, PQA-C8. The chemical oxidants, CuSO4/H2O2, as well as dopamine, were added into the novel PQA-C8 polymer immersion solution for one-step surface modification. Additionally, a two-step immersion scheme, in which the polypropylene substrate was first immersed in the dopamine solution and then in the PQA-C8 solution, was also attempted. Surface analysis results indicated the surface characteristics of the modified substrates were affected by the immersion solution formulation as well as the procedure utilized. The antibacterial assay has shown the titanium substrates modified by the one-step dopamine + PQA-C8 mixtures with the oxidants added and the polypropylene modified by the two-step scheme exhibited bacterial reduction percentages greater than 90% against both Gram-positive S. aureus and Gram-negative E. coli and these antibacterial substrates were non-cytotoxic.

Polypropylene-Rendered Antiviral by Three-Dimensionally Surface-Grafted Poly(N-benzyl-4-vinylpyridinium bromide).

To inhibit viral infection, it is necessary for the surface of polypropylene (PP), a polymer of significant industrial relevance, to possess biocidal properties. However, due to its low surface energy, PP weakly interacts with other organic molecules. The biocidal effects of quaternary ammonium compounds (QACs) have inspired the development of nonwoven PP fibers with surface-bound quaternary ammonium (QA). Despite this advancement, there is limited knowledge regarding the durability of these coatings against scratching and abrasion. It is hypothesized that the durability could be improved if the thickness of the coating layer were controlled and increased. We herein functionalized PP with three-dimensionally surface-grafted poly(N-benzyl-4-vinylpyridinium bromide) (PBVP) by a simple and rapid method involving graft polymerization and benzylation and examined the influence of different factors on the antiviral effect of the resulting plastic by using a plaque assay. The thickness of the PBVP coating, surface roughness, and amount of QACs, which jointly determine biocidal activity, could be controlled by adjusting the duration and intensity of the ultraviolet irradiation used for grafting. The best-performing sample reduced the viral infection titer of an enveloped model virus (bacteriophage ϕ6) by approximately 5 orders of magnitude after 60 min of contact and retained its antiviral activity after surface polishing-simulated scratching and abrasion, which indicated the localization of QACs across the coating interior. Our method may expand the scope of application to resin plates as well as fibers of PP. Given that the developed approach is not limited to PP and may be applied to other low-surface-energy olefinic polymers such as polyethylene and polybutene, our work paves the way for the fabrication of a wide range of biocidal surfaces for use in diverse environments, helping to prevent viral infection.

Theoretical Prediction of the Reaction Probabilities of H, O, and OH Radicals on the Polypropylene Surface.

To determine the H-abstraction reaction probabilities of H/O/OH radicals with a polypropylene (PP) surface, a first-principles calculation was performed based on the DLPNO-CCSD(T)/CBS//M06-2X-D3/def-TZVP theory level. The PP chain model used in this study was 2,4,6-trimethylheptane. The rate constants of the H/O/OH radicals with the isolated PP chain model were calculated based on the conventional transition-state theory. By comparing the experimental values and considering the error factors and their compensation, it was concluded that the orders of magnitude of the predicted rate constants were accurate. The resulting rate constants were converted to reaction probabilities between the H/O/OH radicals and the PP surface. The method used in this study is applicable for obtaining theoretical values of surface reaction probabilities based on first-principles calculations. The calculation at the DLPNO-CCSD(T)/CBS theory level has high accuracy but consumes a large amount of computational resources. The study also demonstrated that the double-hybrid functionals, wB97x-2-D3(BJ) and rev-DSD-PBEP86-D3(BJ), with a 3-ζ or 4-ζ basis set, could reproduce the electronic energy values obtained from DLPNO-CCSD(T)/CBS while using only approximately 1/100 of the computational resources required by the latter under our computer configuration.

Theoretical mechanism behind the higher efficiency of O than OH radicals in polypropylene surface modification: a molecular dynamics study

O and OH radicals are the most important reactive oxygen species in the plasma treatment of polymer surfaces. In our previous studies, we found that the modification efficiency of polypropylene (PP) surface by O radicals was approximately four times higher than that by OH radicals. This observation contrasts with the well-established fact that the chemical reactivity of O radicals with saturated hydrocarbons (C n H2(n + 1)) is 50–60 times lower than that of OH radicals. In this study, classical molecular dynamics simulations with a reactive force field were used to explain this contradiction. The results showed that the surface modification of PP by O or OH radicals is a Langmuir–Hinshelwood process. Both O and OH radicals penetrated the bulk PP, that is, physical adsorption occurred before the chemical reactions. The penetration depth of O radicals was greater than that of OH radicals. Compared to the case of OH radicals, alkoxy radicals (RO·) are more readily formed upon the interactions of the PP surface with O radicals. Furthermore, the β-scission (splitting of the C–C bonds) of RO· can be accelerated by the physically adsorbed O radicals, leading to earlier breakage of PP chains. The improved efficiency of the surface modification of PP upon exposure to O radicals, in contrast to that of OH radicals, can be attributed to the differences in the above three crucial processes. These findings are significant for modelling and understanding the mechanisms of plasma-polymer surface treatment at the atomic and molecular levels.

Preparation of superhydrophobic nanowires on polypropylene surface via injection compression molding for efficient fog collection.

In this work, a superhydrophobic polypropylene (PP) replica with nanowires is fabricated using an injection compression molding (ICM) process. The morphology, superhydrophobicity and fog water harvesting efficiency of the as-prepared PP replica surface are investigated. Morphological characterization indicates that the PP replica surface exhibits nanowires with intertwined tips. Compared to the untreated PP surface (referred to as the PP counterpart), the PP replica surface shows a higher contact angle (CA) and lower rolling angle (RA). Furthermore, the complete transfer of a water droplet with no volume loss from the PP replica surface to the filter paper shows that nanowires on the PP replica surface are responsible for the superhydrophobic and low-adhesive properties of the surface. The Cassie-Baxter state with a CA of ∼153°, low ice adhesion strength (13.3 kPa at -20 °C) and good fog water harvesting efficiency (∼7.26 g m-2 s-1) demonstrate that the prepared PP replica has economic potential for fog water harvesting applications.

Mechanism behind polypropylene surface modifications by OH radicals: An experimental study

We quantitatively investigated the roles and mechanisms of OH radicals in polypropylene (PP) surface modification utilizing a previously proposed vacuum ultraviolet photodissociation reactive species supply method. Water contact angle (WCA), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to characterize the modifications in surface hydrophilicity and components. The relationship between the WCA decline rate and OH radical density at the PP surface was quantified as (2.1 ± 0.1)[OHs] + (0.5 ± 0.1) degrees/s, where [OHs] is in ppm. The ATR-FTIR and XPS results demonstrated that C–OH, CO, C–O–O, and OCO groups were gradually introduced onto the PP surface at different treatment stages. The formation and behavior of low-molecular-weight oxidized materials (LMWOMs) on the PP surface during OH radical treatment were investigated. A modified layer composed of LMWOMs eventually formed on the PP surface. The physicochemical mechanisms underlying these phenomena at the micro-level were also discussed. A possible surface oxidation model was proposed based on WCA results, surface functional groups, and LMWOMs, indicating that the oxidation of the PP chains by OH radicals was initiated at the topmost surface and advanced in the depth direction.

Long-term study of the bacterial colonization of polypropylene microplastics in a freshwater lake by optical and molecular methods

Bacterial colonization and the associated bacterial community on microplastic surfaces in freshwater might alter the physiochemical properties of the plastic surfaces. In our study, a long-term investigation of these potential alterations was performed, as biofilm development needs a more extended period to form, and it could change in connection with the environmental conditions or the location. In this study, our formerly published [56], self-developed plastic colonizer method was used for continuous monitoring of plastic associated bacterial community. The same colonizers, filled with commercially available polypropylene plastic straws cut into less than 5 mm small pieces (microplastic particles), were submerged in a freshwater lake in Hungary (Vácszentlászló), but in this study these sampling tools were kept in the freshwater environment for a much longer period. Time of incubation was fourteen months, started from April 2019 and last until June 2020. Samples from plastic colonizers and a lake water were collected every month (first was taken in May 2019) during this study. The waterborne and polypropylene-associated bacterial communities of these samples were analyzed by Illumina 16S rRNA gene amplicon sequencing. The plastic-associated bacterial community was described at different taxonomic levels. In the first month, the water-associated waterborne community was dominated by Proteobacteria and Cyanobacteria. Proteobacteria followed by Bacteroidetes, and Actinobacteria dominated the polypropylene-associated community. Over time, the bacterial composition on the polypropylene (PP) surface, in terms of phylum level, was altered, eventually becoming distinct from the bacterial community found in the lake water. In addition, Raman microscopy, scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to study the physiochemical changes of the incubated microplastic surfaces due to bacterial colonization. The physical changes were dominant, with the relatively little ageing impact on the chemical composition. Surface morphology and composition of the plastic were studied as they could significantly influence the physical properties of microplastics, the microbiota, and environmental interactions that affect plastisphere colonization. General water analyses of the lake water was also the part of the research, and it was conducted four different time points during the study. Some of the measured components (mostly in August and October of 2019) exceeded the Hungarian governmental threshold for water quality.

Exploring TiO2-PP as a Reusable Floating Photocatalyst for Humic Acid and Iron Removal in Peat Water

In this study, we fabricate TiO<sub>2</sub>-PP catalyst and analyze its use for peat water photodegradation. The photocatalyst is a thin layer of TiO<sub>2</sub> deposited on the surface of polypropylene (PP) grains by the thermal milling method. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) images indicate that the fabrication successfully deposited TiO<sub>2</sub> particles on the PP grain surface homogeneously well. The results show that photocatalysis of peat water using TiO<sub>2</sub>-PP with solar irradiation is more effective than the UV lamp. After photocatalysis for 40 hours with solar irradiation, the humic acid content in peat water decreases significantly, accompanied by a decrease in Fe concentration. When being reused, TiO<sub>2</sub>-PP photocatalyst shows performance above 92% in the fourth iteration, while in the fifth iteration, the performance decreases to 83%. These results show that TiO<sub>2</sub>-PP has the potential to be applied as a reusable floating photocatalyst to reduce the humic acid and iron content in peat water.

Experimental Investigation of the Peel Strength of Artificial Leather and Polypropylene Specimens.

This study investigates the surface properties and adhesive strength of polypropylene (PP) in order to enhance the bond between PP injection-molded specimens and polyvinyl chloride (PVC) synthetic artificial leather. Plasma, primer, and flame treatments were applied to the surface of each specimen prepared using the two types of injection molds. The surface morphology, surface roughness, and contact angle were analyzed, and peel-strength analyses and a morphological inspections of the peeled specimens were performed. The peeling strength of the PP injection molding was measured, followed by a morphological examination of the peeled specimens. The plasma and flame treatments improved the peel strength, and the plasma and flame treatments changed the rough exterior to a hydrophilic surface, improving the peel strength. In addition, the primer treatment exhibited a lower peel strength than did the other treatments. This confirmed the low adhesion of the primer to the hydrophobic PP surface. The outcomes of this study can be employed across a multitude of industries that require improved adhesion for PP injection molded products.

Fabrication methodologies for antimicrobial polypropylene surfaces with leachable and nonleachable antimicrobial agents

AbstractReported herein is the fabrication of antimicrobial polypropylene (PP) surfaces with nonleachable magnesium hydroxide biocides and compares its performance with leachable copper (II) chloride dihydrate. Two methods were used for creating PP‐bearing biocides. One way involves melt‐blending of biocides and PP and subsequent injection molding to create the desired antimicrobial PP surface. Another technique consists of thermal embossing of antimicrobial agents on the PP surface. The biocide‐bearing PP surfaces were evaluated against Escherichia coli (E. coli) K‐12 MG1655) for up to 24 h. In the case of injection‐molded PP system, leachable CuCl2·2H2O showed a 5.87 ± 0.01 log reduction after 24 h, but only 0.47 ± 0.03 log reduction for PP bearing nonleachable Mg(OH)2. On the contrary, thermally embossed PP with CuCl2·2H2O and Mg(OH)2 showed 2.28 ± 0.03 and 3.78 ± 0.03 log reductions, respectively, after 24 h. The nonleachable Mg(OH)2 imparted antimicrobial properties only to the PP surface prepared via thermal embossing. In contrast, owning to the leachable copper ions, leachable CuCl2·2H2O biocides imparted PP surfaces antimicrobial irrespective of the molding or surface embossing approach. This approach provides an advantage for nonleachable PP‐based antimicrobial surfaces in overcoming the toxicity concern associated with plastics bearing leachable biocides.

Investigation of water separation capabilities of demisters integrated with microstructured surfaces

Demisters with high water separation efficiencies play an important role in performance enhancement of thermal desalination. Bio-inspired, microstructured surfaces have been highlighted due to the potential to considerably increase water separation by enhancing water capturing and transporting features. However, experimental investigation on the performance enhancement of the demisters with those functional surfaces is still lacking. Herein, we demonstrate water collection and separation characteristics of the large-scale demisters integrated with hybrid microstructured surfaces. Particularly, the hybrid microstructured polypropylene surfaces to possess the vertically-aligned spiky cone arrays along with multiple sets of open-type microchannels are successfully fabricated in uniform manner by using an injection molding process. The fabricated hybrid microstructured surfaces perform twice and up to 3.2 times higher water collection than the control planar surfaces in low-speed and high-speed air flows, respectively, owing to their enhanced water capturing and transporting capabilities by the capillary pressure generated by the microstructures. As a model study, the inner surfaces of the axial cyclone-type demister ducts are modified with the hybrid microstructured surfaces, leading to up to 12 % enhancement of the water separation efficiencies of the demisters, compared to the control planar surface demister in high-speed air flow.

Nanoscale thinning of metal-coated polypropylene films by Helium-ion irradiation

Polypropylene (PP) films have a wide range of applications, e.g. as dielectric materials for metallized film capacitors. In this article, we present a method for thickness reduction of PP films by ion irradiation, which has a direct effect on device capacitance. We show that the thickness of PP layers can be reduced by irradiation with He+ ions and controlled on the nanometer scale by the irradiation dose. The effect of different thin metal film coatings on PP surface was also investigated. The metal coatings were used for two reasons: they function as one of the metal electrodes in the capacitor structure, and they minimize sample charging during ion irradiation. Three different metallization materials were investigated: 5 nm Pt60Pd40, 5 nm Au, and 15 nm Al. We studied two technologically relevant PP films: the thinnest commercially available biaxially oriented polypropylene (BOPP) and spin-coated polypropylene (SC-PP) thin films. The irradiation was done with a focused Helium-ion beam (He-FIB) in a Zeiss Orion NanoFab Microscope at a landing energy of 30 keV with doses in a range of 5.4 × 10–5 nC/μm2 to 8.1 × 10–3 nC/μm2. An atomic force microscope (AFM) was used to analyze the details of surface modification: the surface height of the irradiated regions and surface morphology changes caused by the irradiation. For all applied doses, the Al-coated samples demonstrated smaller surface-height reduction compared to the Pt60Pd40 and Au-coated samples. We speculate that the possible factors responsible for this effect include differences in the thickness and the crystalline-grain orientation (texture) of the metallization films. Both BOPP and spin-coated PP presented surface ridges at the borders between the irradiated and non-irradiated regions. It can be attributed to the mechanical strain induced by the material modification.

Effect of fly ash modified plastic particles using heat welding method on performance and interface modification mechanism of mortars

The weak bonding of plastic/paste caused by the hydrophobicity of plastic surface is a significant bottleneck for the large-scale application of plastics in concrete, which seriously affects the macro and micro structure of plastic concrete. To address this issue, a heat welding modification method was proposed in this paper, which utilized the thermoplastic of the plastic, fly ash was welded to the polypropylene (PP) surface to form a composite aggregate with fly ash properties (F@PP). Experimental results revealed that F@PP exhibited better wettability (contact angle = 75°) and pozzolanic activity compared to unmodified PP. Moreover, compared to PP mortar or F/PP mortar (simply add fly ash to PP mortar), the microscopic interface of F@PP/paste was more compact and its Ca/Si was mostly reduced to less than 2.0. The porosity of F@PP mortar was significantly reduced by 50–57% at 28d and the compressive strength was increased by 11–28% at 3d, 7d, and 28d. These findings highlight the effectiveness of the proposed heat weld method in enhancing the plastic/paste interface and the performance of plastic mortars.