PP Surface Research Articles

The thermal conductivity of 3D network reinforced polypropylene matrix composites was constructed by the pickering‐like emulsion method

AbstractPolypropylene (PP) has the advantages of corrosion resistance, easy processing, and low dielectric loss, but its low thermal conductivity limits the application of its composites in fields such as electronic packaging. To solve this problem, in this work, composite microspheres with the segregated structure were prepared by coating boron nitride nanosheets (BNNSs) on the PP surface by Pickering‐like emulsion method, and BNNSs@PP composites with three‐dimensional thermal conductivity network were obtained after molding. Due to the high thermal conductivity of BNNSs and the formation of perfect thermal conduction pathways, the thermal conductivity of the composites reached 1.71 W m−1 K−1 when the content of BNNSs was 10.1 wt%, which was a 713% increase in thermal conductivity for that of pure PP. At the same time, the mechanical properties of the composites were ensured. This method provides a simple and effective technique to improve the thermal conductivity of PP‐based thermally conductive composites, which has a wide application potential in electronic packaging.

Effect of Compressive Modulus of Porous PVA Hydrogel Coating on the Preventing Adhesion of Polypropylene Mesh.

PP mesh is a widely used prosthetic material in hernia repair. However, visceral adhesion is one of the worst complications of this operation. Hence, an anti-adhesive PP mesh is developed by coating porous polyvinyl alcohol (PVA) hydrogel on PP surface via freezing-thawing process method. The compressive modulus of porous PVA hydrogel coating is first regulated by the addition of porogen sodium bicarbonate (NaHCO3) at various quality ratios with PVA. As expected, the porous hydrogel coating displayed modulus more closely resembling that of native abdominal wall tissue. In vitro tests demonstrate the modified PP mesh show superior coating stability, excellent hemocompatibility, and good cytocompatibility. In vivo experiments illustrate that PP mesh coated by the PVA4 hydrogel that mimicked the modulus of native abdominal wall could prevent adhesion effectively. Based on this, the rapamycin (RPM) is loaded into the porous PVA4 hydrogel coating to further improve anti-adhesive property of PP mesh. The Hematoxylin and eosin (H&E) and Masson trichrome (MT) staining results verified that the resulting mesh could alleviate the inflammation response and reduce the deposition of collagen around the implantation zone. The biomimetic mechanical property and anti-adhesive property of modified PP mesh make it a valuable candidate for application in hernioplasty.

Metallization of polypropylene substrates through surface functionalization and physical vapor deposition of chromium coatings

Physical vapor deposition (PVD) of chromium coatings represents an interesting alternative to electroplating to obtain metallized plastic parts for a variety of manufacturing sectors. This process is however hampered by the limited adhesion of the metallic layer on the underlying polymeric substrates. Within this context, PVD metallization of polypropylene substrates has so far been particularly challenging given the low surface energy and poor wettability of this commodity plastics. To address this issue, a comprehensive approach is proposed here to enable the production of PVD-metallized PP substrates with excellent and stable interlayer adhesion. The adhesive properties of the PP substrate are modified by a selective UV-induced photografting process in which vinyl-, glycidyl- or 2-hydroxyethyl methacrylate species are covalently attached to the PP surface, as confirmed by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and surface wettability measurements. Based on the chemistry of the photografted functionality, different resin systems are selected and investigated for use as primers to enable subsequent chromium deposition, including acrylic, epoxy and polyurethane systems. The effect of the photografting process on the adhesion between PP and the primers is systematically assessed by means of pull-off tests, highlighting a significant improvement of the adhesion force after surface functionalization with appropriate grafting agents. Finally, functionalized PP substrates are chromated through PVD, obtaining homogeneous and crack-free chromium surfaces upon judicious selection of suitable primer-grafting agent combinations. This also led to outstanding interlayer adhesion and micromechanical performance. This work provides the first demonstration of chromium-metallization of PP substrates via PVD for metallized plastic components with excellent surface characteristics, and paves the path for the design of mechanically durable and aesthetically-compliant PVD-metallized PP components.

PVA/whey protein nanofiber-coated PP melt blown integrated with Pickering emulsion of citral stabilized for potential medical applications

As an antibacterial agent with pleasant fragrance, citral (CIT) indicates hydrophobic character, and therefore has low water solubility. In this study, Pickering emulsions were formed and polyvinyl alcohol (PVA)/whey protein hydrophilic nanofibers were coated on PP melt blown non-woven surfaces by electrospinning method. In this context, hydrophobic citral essential oil is stabilized with β-cyclodextrin (β-CD) in the electrospinning process. PVA and whey protein polymer blend were used as nanofiber matrixes. The morphological, physical, and thermal properties of the β-CD/citral complexes were investigated in PVA/whey protein nanofiber-coated PP non-wovens at various β-CD levels (1:2, 1:4 and 1:6). Furthermore, zone inhibition procedure was performed to evaluate antibacterial activity of the samples against Gram (+) (Staphylococcus aureus ATCC® 25923) and Gram (-) (Escherichia coli ATCC® 25922, and Pseudomonas aeruginosa ATCC® 27853) bacteria. The morphology of fibers showed that all obtained nanofiber-coated PP surfaces were in the range with 216 - 330 nm average fiber diameter. Fourier Transform Infrared (FT-IR) and thermal gravimetric analysis (TGA) thermograms revealed that citral were successfully integrated into the bio-based nanofibers. As the amount of citral increased (i.e., the β-CD/citral increased), the thermal resistance of bio-based nanofiber coated PP surfaces increased. Antibacterial activity indicated the citral-loaded nanofiber-coated PP surfaces were most effective against Escherichia coli, while none of the samples have antibacterial activity against Pseudomonas aeruginosa. Overall, the results displayed that the fabricated PVA/whey protein nanofiber-coated PP samples integrated with Pickering emulsion of citral stabilized have promising wound dressing applications.

Recovery of copper sulfate from acidic mine waters by membrane crystallization

The recovery of valuable resources from acid mine waters has attracted high interest in moving forward to a circular economy approach. In this work, acidic solutions were processed by a MCr process for the first time, allowing the recovery of copper in the form of copper sulfate crystals. PP and PTFE membranes were investigated at different temperatures (40–80 °C), showing a remarkable water flux decrease over time due to a severe accumulation of crystals on the surface of both PP and PTFE membranes, favoring the heterogeneous crystallization of CuSO4 on the membrane surface instead to the acid solution bulk. The flowrate and acid concentration were also evaluated to find operational conditions that can control crystal accumulation. The high accumulation of crystals was observed for all operating conditions except for a highly acidic condition of 100 g/L acid, where the membrane visually responded by repelling the crystals accumulation on the surface. The membranes were wholly characterized, observing a dramatic impact on the membrane morphology. Results show that copper crystallization by membranes is challenging. Still, considering new membrane materials, operating conditions could allow the process's feasibility.

Functional surfaces by plasma grafting of itaconic acid onto polypropylene mesh: synthesis and structural investigations

AbstractPolypropylene (PP) is an unflinching element of biomaterials for human healthcare, leading to enormous possibilities for their functional development within a broad range of biocompatible and bioreceptive materials. Plasma grafting of itaconic acid was carried out on a PP surface by oxygen plasma activation. The variation of grafting parameters, such as monomer concentration, reaction temperature and reaction time, as a function of the degree of grafting was investigated. The graft distribution and surface homogeneity of the PP surfaces were evaluated using confocal microscopy, field emission scanning electron microscopy and atomic force microscopy. These surface characterizations led to information about the impact of grafts on the material surface. © 2023 Society of Industrial Chemistry.

Photothermal-driven pH-responsive fiber composite membrane for oil-wastewater purification

Oil spills and the discharge of organic wastewater have posed a severe danger to environmental security. To address this issue, various functional oil/water separation materials for wastewater purification have been developed. In this work, MXene/PPy was loaded on PP fiber by simple in-situ polymerization and vacuum-assisted filtration technology. Polypropylene was modified by dopamine (PDA) through in-situ polymerization, to improve the loading fastness of MXene/PPy on the surface of PP. To increase the durability of the fiber membrane, the pH-responsive polymer (PDM) was simply immersed on the outer layer. The successfully prepared PP-MXene/PPy-PDM has excellent pH response and photothermal conversion performance. When pH= 2, the water contact angle (WCA) was 52°. When pH= 12, WCA was 125°. The surface of PP-MXene/PPy-PDM was heated to 104.6 ℃ in ten minutes under the irradiation of 2 kW·m−2. PP-MXene/PPy-PDM could continuously separate oil/water mixture for 12 h, and the highest separation flux was 3.87 kg·m−2·h−1. Moreover, PP-MXene/PPy-PDM has excellent stability, corrosion resistance and recyclability. This study provided a new strategy for preparing intelligent responsive fiber composite membrane for oil-water separation, which has a wide range of practical applications in the treatment of oily wastewater.

Preparation of polypropylene with photothermal conversion and hydrophilicity by one-step impregnation for efficient interfacial water evaporation

Solar-driven interfacial water evaporation is a technology that is currently attracting significant interest for tackling freshwater scarcity. However, the creation of porous membranes with photothermal conversion and hydrophilicity remains a challenging task. This study utilizes melt-blown polypropylene nonwoven (PP), a substrate with high porosity, low cost and high yield, to prepare evaporation membranes exhibiting photothermal conversion properties. The PP surface was treated with a one-step impregnation method to produce both shell and nanoparticles containing MnO2−x. The addition of MnO2−x grants the PP membranes both photothermal conversion and hydrophilicity simultaneously. Sunlight absorption efficiency of PP membranes covered with MnO2−x (M-PP) is 85.83%, and its hydrophilicity and porosity enable it to form an ultra-thin layer of water during evaporation, promoting rapid escape of vapors. Evaporation rate of M-PP membranes reach 1.02 kg m−2 h−1, much higher than that of PP and bulk water. In addition, M-PP membranes have excellent corrosion resistance, which is potentially valuable in treating wastewater and desalinating seawater.

Insight into peculiar adhesion of cells to plasma‐chemically prepared multifunctional “amino‐glue” surfaces

AbstractPlasma polymers (PPs) can easily modify material surfaces to improve their bio‐applicability due to match‐made surface‐free energy and functionality. However, cell adhesion to PPs typically composed of various functional groups has not yet been fully understood. We explain the origin of strong resistance to trypsin treatment previously noted for nonendothelial cells on amine PPs. It is caused mainly by nonspecific adhesion of negatively charged parts of transmembrane proteins to the positively charged amine PP surface, enabled by thin glycocalyx. However, endothelial cells are bound primarily by their thick, negatively charged glycocalyx and sporadically by integrins in kinetic traps, both cleaved by trypsin. Cell scratching by atomic force microscopy tip confirmed the correlation of trypsin resistance to the strength of cell adhesion.

Smoke suppression, flame retardancy, and fire toxicity of polypropylene containing melamine salt of pentaerythritol phosphate halloysite

AbstractPolypropylene (PP) was melt blended with a new mono molecular intumescent flame retardant, melamine salt of pentaerythritol phosphate halloysite (MPPH) to enhance its thermal stability, flame retardancy, and smoke suppression properties. The structure of MPPH was elucidated by Fourier transform infrared (FTIR), 1H NMR, X‐ray diffraction (XRD), and energy dispersive X‐ray (EDX) analysis. PP composites results showed that MPPH increased the thermal stability of PP at high temperatures in all PP composites. The horizontal flammability test (UL94H) showed that MPPH stopped flame propagation in PP composites. Vertical burning rate test (UL94V) revealed that PP composites can attain V0 rating at loading levels 25, 30, and 35 wt.% of MPPH. Limiting oxygen index (LOI) data indicated that adding 20, 25, 30, and 35 wt.% of MPPH to PP increased the LOI value of PP (19.2%) to 27.1%, 32.5%, 35.4%, and 38.7%. MPPH succeeded in reducing the maximum specific optical density (Dsmax), mass specific optical density (MOD), and rate of smoke generation during the first 4 min (VOF4) of PP composites compared to PP alone. FTIR gas analyzer results revealed that MPPH decreased the emission of CO and CO2 in the gas phase during the combustion process. Digital photos and scanning electron microscope (SEM) images of char residues remained after the smoke density test revealed that MPPH succeeded in forming a cellular and cohesive char layer on the PP surface. The new data is expected to increase the use of PP in rigid packaging applications.

The effects of weathering-induced degradation of polymers in the microplastic study involving reduction of organic matter

The analysis of microplastics in complex environmental samples requires the use of chemicals to reduce the organic matrix. This procedure should be evaluated in terms of the preservation of the microplastic's integrity, typically done with pristine reference microplastics. However, real microplastics are most likely degraded due to weathering, so pristine reference microplastics might not depict the appropriateness of the process. This study performed a purification process using sodium dodecyl sulfate and hydrogen peroxide on sewage sludge containing LLDPE, HDPE, PP, PS, PET, PA66 and SBR samples exposed to simulated environmental weathering. The degradation of the polymers was assessed by analyzing surface morphology, mass variation, and mechanical, thermal and chemical properties. Comparison with pristine polymers revealed that the purification process can lead to more detrimental effects if the polymers are weathered. After the purification process, some important observations were: 1) LLDPE, PP and SBR surfaces had cracks in the weathered samples that were not observed in the pristine samples, 2) weathered LLDPE, PP and PA66 experienced greater mass loss than pristine, 3) the fragmentation propensity of weathered LLDPE, HDPE, PP, PS and SBR increased compared to pristine samples and 4) the main characteristic peaks in FTIR spectrum could be identified and used for chemical identification of most polymers for pristine and weathered samples. Based on the findings of this study, when analyzing the efficiency and adequacy of a purification process with methods based on surface morphology, mass variation and particle counting indicators, it is recommended to consider the differences that potentially arise between pristine and weathered microplastics, especially for polyolefins (PEs and PP).

Mussel-inspired polyurethane coating for bio-surface functionalization to enhance substrate adhesion and cell biocompatibility

Considerable implant materials are prone to cause a severe inflammatory reaction due to poor histocompatibility, which leads to various complications and implant failure. Surface coating modification of these implant materials is one of the most important techniques to settle this problem. However, fabricating a coating with both adequate adhesiveness and excellent biocompatibility remains a challenge. Inspired by the adhesion mechanism of mussels, a series of mussel-inspired polyurethanes (PU-LDAs) were synthysized through a step growth polymerization based on hexamethylene diisocyanate as a hard segment, polytetra-methylene-ether-glycol as a soft segment, lysine–dopamine (LDA) and butanediol as chain extenders with different mole ratios.The coatings of PU-LDAs were applied to various substrates, such as stainless steel, glass and PP using a facile one-step coating process. The introduction of 3,4-dihydroxyphenylalanine (DOPA) groups can greatly improve the adhesion ability of the coatings to the substrates demonstrated by a 180° peel test. The peel strength of the PU-LDA100 coating containing high LDA content was 76.3, 48.5 and 67.5 N/m, which was 106.2%, 246.4% and 192.2% higher than that of the PU-LDA00 coating without LDA on the surface of stainless steel, glass and PP, respectively. Meanwhile, this PU coating has a lower immune inflammatory response which provides a universal method for surface modification of implant materials. Moreover, the DOPA groups in PU-LDAs could combine with the amino and thiol groups on cell membrane surface, leading to the improvement of cell adhesion and growth. Therefore, it has great potential application in the field of biomedical implant materials for the clinic.

The functionalization of selected chemical agents on a polypropylene fiber and the study on the physical and anti‐bio‐fouling properties of the functionalized fibers

AbstractThe functionalizing of a fiber surface by a chemical may alter the physical and biological properties of the fiber. The functionalization of a polypropylene fiber (PP) by selected monomers (1) acrylic acid (AA), (2) 2‐hydroxyethyl methacrylate (HEMA), (3) 2‐dimethyl amino ethyl methacrylate (DMAEMA), and (4) methyl acrylate (MA) studied using two different ultraviolet (UV) irradiation techniques, simultaneous UV irradiation and functionalization (SUVF) and pre‐UV irradiation (PUV). Based on the measured grafting parameters, it found, the tendency of monomers for functionalizing on the PP surface was the highest for the AA and HEMA, and the lowest for the MA and DMAEMA for used SUVF and PUV techniques, respectively. The SEM micrographs showed the smooth surface of the PP fiber changed to a rough surface after functionalization. The functionalization also increased the crystallinity with little effect on melting point of the fiber. Except for the MA, functionalization increased the hydrophilic properties of the fiber. The PUV technique was more effective on the grafting degree % of the monomer than the SUVF technique for functionalized fibers with HEMA and MA. The biological experiments demonstrated the eligibility of AA as a favorable functionalizing agent for increasing the anti‐bio‐fouling properties of the studied PP fiber.

Study on the performance and mechanism of modified mica for improving polypropylene composites

Abstract Polypropylene (PP) has the most extensive plastics of plastics because of the advantages of simplicity, easy processing, high mechanical properties, high corrosion resistance and abrasion resistance and electrical insulation. The application of PP has limitations in many fields because it is lack of formation shrinkage, low modulus, poor thermal stability, strong gap and low temperature and cracking. The addition of mineral fillers can not only improve their performance, not just the PP/mineral filler composite materials required, but also reduce the cost of the material. Therefore, in this paper, lamellar mica was selected as mineral filler to modify the surface of PP. The effects of titanate coupling agent and silane coupling agent modified mica, and their addition on the properties of PP were systematically studied. KH-570 modification increases the tensile strength, bending strength and modulus of the composites, while JN-114 and KH-570 can effectively improve the toughness and processability of PP composites. The interaction between modifier and mica was analyzed comprehensively by infrared spectroscopy (FTIR), and the effect mechanism of mica on the properties of PP was discussed by scanning electron microscope. The results show that different modified mica as mineral filler and PP can produce synergistic effect.

Rational design of dual-functional surfaces on polypropylene with antifouling and antibacterial performances via a micropatterning strategy

We construct a dual-function micropatterned PP surface with antifouling and antibacterial properties through plasma activation, photomask technology and ultraviolet light-induced graft polymerization.

Mass Transfer and Optical Properties of Active PET/PP Food-Grade Films Impregnated with Olive Leaf Extract

A supercritical solvent impregnation (SSI) technique was employed to incorporate, by batch- and semicontinuous-modes, bioactive olive leaf extract (OLE) into a food-grade multilayer polyethylene terephthalate/polypropylene (PET/PP) film for active food packaging applications. The inclusion of OLE in the polymer surfaces significantly modified the colour properties of the film. A correlation of 87.06% between the CIELAB colour parameters and the amount of the OLE impregnated in the film was obtained which suggests that colour determination can be used as a rapid, non-destructive technique to estimate the OLE loading in the impregnated matrices. The UV barrier and water permeability properties of the films were not significantly modified by the incorporation of OLE. The migration of OLE into a 50% (v/v) ethanol food simulant demonstrated faster release of OLE from the PP surface than from the PET surface which may be due to the different interactions between OLE and each polymer.

Designing a Bioinert Surface by Simple Coating with Cholesterol End-Modified Poly(ethylene glycol).

A bioinert surface has been designed by simple coating with cholesterol end-modified poly(ethylene glycol), Chol-U-Pr-mPEG, using a cholesterol anchor. A poly(propylene) (PP) surface was immersed into the Chol-U-Pr-mPEG aqueous solution, where control mPEGs without cholesterol were not suitable for the design of bioinert surfaces. The resulting surfaces coated with Chol-U-Pr-mPEG above and below its critical micelle concentration were swollen and less swollen, respectively. Chol-U-Pr-mPEG with a molecular weight of 2000, Chol-U-Pr-mPEG (2k), formed a swollen layer with a thickness of 10-15 nm and adhered to the PP surface with an estimated Kd value of 4.4×10-7 M. The resulting Chol-U-Pr-mPEG (2k)-coated surface with the swollen layer suppressed the adsorption of γ-globulin proteins and the adhesion of platelets in plasma. Although the PP surface coated with Chol-U-Pr-mPEG with a molecular weight of 5000, Chol-U-Pr-mPEG (5k), also suppressed the adsorption of γ-globulin proteins, the Chol-U-Pr-mPEG (5k)-coated PP surface did not suppress the adhesion of the platelets in plasma despite the existence of a swollen layer with a thickness of 20-25 nm. These results suggest that the Chol-U-Pr-mPEG-coated PP surface with an optimized swollen layer has been established as a bioinert surface by a facile method.

Stability of a‐C:H:SiOx coating on polypropylene to chemical sterilization

AbstractPolypropylene (PP) is traditionally used in the production of medical devices, such as catheters, dialyzers, syringes due to its good chemical and thermal resistance, biocompatibility, and low cost. Sterilization can however damage these devices, when the polymer additive releases into physiological fluids, thereby harming the patient health. This article proposes to deposit biocompatible a‐C:H:SiOx coatings onto PP surfaces and studies the coating stability after chemical sterilization. Five different chemical sterilizers, namely, hydrogen peroxide, ethanol, miramistin, formaldehyde, and ethylene oxide are used to compare their effect on the coating stability on the PP substrate. Untreated and sterilized samples are incubated in a liquid synthetic nutrient to obtain extracts that are used for sterility testing and determining the degree of interaction of samples with the nutrient medium. The changes in the coating functional groups and surface morphology are examined by using the Fourier transform infrared spectroscopy and the scanning electron microscopy, respectively. It is shown that the a‐C:H:SiOx coating has a protective effect on the PP substrates subjected to chemical sterilization. The experiment results clearly showed that the ethanol sterilization causes the most serious changes in the structure of PP, and also leads to the barrier coating failure. On the other hand, ethylene oxide sterilization has a minimal effect on the structure of both uncoated and coated PP substrates.

Titanium-based nanorods/ketjen black modified separator as polysulfides barrier for lithium sulfur cell

Abstract The practical application of lithium sulfur (Li/S) cells is mainly hindered by the shuttle effect. Herein, the titanium-based nanorods/ketjen black (KB) composite prepared by a facile hydrothermal reaction is deposited on polypropylene to fabricate a bi-functional separator (KTO-2/PP) for Li/S cell. Using bare sublimed sulfur cathode, the cell based on KTO-2/PP separator exhibits excellent rate capability, delivering 1122, 856, and 566 mAh g−1 at 0.2, 1 and 2C, respectively. Moreover, the reversible capacity of the KTO-2/PP based cell can reach 754 mAh g−1 (1C) in the 200th cycle. Such performance boost is primarily ascribed to the KTO-2/PP separator, that Li+ is allowed to pass through but lithium polysulfides (LiPS) is shielded against shuttle. The conductive KB facilitates electron transport and adsorbs LiPS physically. The titanium-based nanorods adsorbs LiPS chemically by forming Ti–S bond which is confirmed by XPS analysis. Regarding the aged Li/S cell using KTO-2/PP, the smooth surface of PP (facing lithium anode) and the less sediment and negligible corrosion on anode indicate that the KTO-2/PP separator acts as an efficient barrier to inhibit the LiPS migration and enhances the electrochemical performance.

Design and preparation of superwetting polymer surface

A new strategy to prepare superwetting polymer surface is reported in this paper. Polypropylene sheets with superhydrophilic, superlipophilic and superamphilic surfaces can be prepared easily by using this strategy. PP sheet with a superhydrophilic surface or a superlipophilic surface was prepared by grafting hydrophilic monomer or lipophilic monomers onto PP sheet with a microporous surface. The microporous surface of PP sheet displays contact angle of 0° for aqueous and oily liquids when both hydrophilic and lipophilic monomers were grafted onto PP microporous surface, indicating that superamphilic PP surface can be also obtained by using this strategy. The effects of grafting modification on surface morphology and chemical composition were investigated and the mechanism of superwetting was explored. It is well known that PP cannot be bonded by aqueous binder, while PP with superhydrophilic surface prepared in this work can be bonded together by aqueous binder with bonding strength of 8Kpa.