Surface treatment of LLDPE and LDPE blends by nitric acid, sulfuric acid, and chromic acid etching

From Basics to Frontiers: A Comprehensive Review of Plasma-Modified and Plasma-Synthesized Polymer Films

This comprehensive review begins by tracing the historical development and progress of cold plasma technology as an innovative approach to polymer engineering. The study emphasizes the versatility of cold plasma derived from a variety of sources including low-pressure glow discharges (e.g., radiofrequency capacitively coupled plasmas) and atmospheric pressure plasmas (e.g., dielectric barrier devices, piezoelectric plasmas). It critically examines key operational parameters such as reduced electric field, pressure, discharge type, gas type and flow rate, substrate temperature, gap, and how these variables affect the properties of the synthesized or modified polymers. This review also discusses the application of cold plasma in polymer surface modification, underscoring how changes in surface properties (e.g., wettability, adhesion, biocompatibility) can be achieved by controlling various surface processes (etching, roughening, crosslinking, functionalization, crystallinity). A detailed examination of Plasma-Enhanced Chemical Vapor Deposition (PECVD) reveals its efficacy in producing thin polymeric films from an array of precursors. Yasuda's models, Rapid Step-Growth Polymerization (RSGP) and Competitive Ablation Polymerization (CAP), are explained as fundamental mechanisms underpinning plasma-assisted deposition and polymerization processes. Then, the wide array of applications of cold plasma technology is explored, from the biomedical field, where it is used in creating smart drug delivery systems and biodegradable polymer implants, to its role in enhancing the performance of membrane-based filtration systems crucial for water purification, gas separation, and energy production. It investigates the potential for improving the properties of bioplastics and the exciting prospects for developing self-healing materials using this technology.

Influence of ultraviolet and chemical treatment on the biodegradation of low-density polyethylene and high-density polyethylene by Cephalosporium strain

In the present work, the potential of Cephalosporium strain in degrading the pre-treated (ultraviolet irradiation followed by nitric acid treatment) low-density polyethylene and high-density polyethylene films was investigated. Our observations revealed a significant weight reduction of 24.53 ± 0.73% and 18.22 ± 0.31% in pre-treated low-density polyethylene and high-density polyethylene films respectively, after 56 days of incubation with the Cephalosporium strain. Changes in the physicochemical properties of the mineral salt medium (MSM) were studied to assess the extent of biodegradation. The pH of the MSM decreased gradually during the incubation period, whereas its total dissolved solids and conductivity values increased steadily. Fourier transform infrared spectroscopy (FTIR) indicated the formation of hydroxyl and C = C groups in biodegraded low-density polyethylene films, while in the case of biodegraded high-density polyethylene films it indicated the [Formula: see text]CH₂ stretching. Furthermore, the thermogravimetric analysis (TGA) revealed an enhancement in the thermal stabilities of both the LDPE and HDPE films post the biodegradation. Modifications in the polymer surface morphologies after UV irradiation, chemical treatment, and biodegradation steps were visualized via scanning electron microscopy (SEM) analysis. All our observations confirm the ability of the Cephalosporium strain in biodegrading the pre-treated LDPE and HDPE films.

Influence of nitric acid on biodegradation of polystyrene and low-density polyethylene by Cephalosporium species

Petroleum-based polymers are not susceptible to microorganisms because of its high molecular weight. Acid treatments convert the polymers into a more oxidized form having low molecular weight. The present in-vitro degradation study focuses on the potential of Cephalosporium species to degrade acid-treated polystyrene (PS) and low-density polyethylene (LDPE) films. A weight loss of around 12% and 13% was achieved for PS and LDPE films respectively in eight weeks of treatment with Cephalosporium species. Fourier transform infrared spectroscopy analysis showed the formation of hydroxyl and carbonyl groups in nitric acid treated PS and LDPE films, respectively. Scanning electron microscopy indicated modifications in the surface morphology of PS and LDPE films after chemical and microbial treatment. An increase in crystallinity of pre-treated polymer samples was observed after fungal treatment. The observations of present study confirmed the enzymatic deterioration and assimilation of pre-treated PS and LDPE samples by the microbial species.

Improving Surface Functionality, Hydrophilicity, and Interfacial Adhesion Properties of High-Density Polyethylene with Activated Peroxides

Polyolefins have had limited application in advanced technologies due to their low surface energy, hydrophobicity, and weak interfacial adhesion with polar coatings. Herein, we propose the use of transition metals at their lowest oxidation state and inorganic peroxides to improve the functionality, surface free energy, hydrophilicity, and adhesion properties of high-density polyethylene (HDPE). Among the nine combinations of transition metals and peroxides used in this study, the combination of Co(II) and peroxymonosulfate (PMS) peroxide was the most effective for surface modification of HDPE, followed closely by the combination of Ru(III) and PMS. After chemical treatment, HDPE's surface functionality, composition, and energy were analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Hydroxyl, carbonyl, and carboxylic acid functional groups were detected on the surface, which explained the improved hydrophilicity of the modified HDPE surface; the contact angle of HDPE with DI water decreased from 94.31 to 51.95° after surface treatment. To investigate the effect of HDPE's surface functionality on its interfacial properties, its adhesion to a commercial epoxy coating was measured via pull-off strength test according to ASTM D54541. After only 20 min of surface treatment with Co(II)/PMS solution, the adhesion strength at the interface of HDPE and the epoxy coating increased by 193%, confirming the importance of polyolefins' surface functionality on their interfacial adhesion properties. The method outlined herein can improve HDPE's surface functionality by introducing sulfate radicals. It improves HDPE's hydrophilicity and adhesion properties without requiring strong acids or time-consuming pre- or post-treatment processes. This process has the potential to increase the use of polyolefins in various industries, such as for protective coatings, high performance lithium-ion battery separators, and acoustic sensors.

Preparation of Biocomposite Material with Superhydrophobic Surface by Reinforcing Waste Polypropylene with Sisal (Agave sisalana) Fibers

Nowadays, eco-friendly, renewable, and biodegradable biocomposites are among the most intensely sought materials of choice. Biocomposites have been widely used as substitutes for plastics due to their biodegradability. However, biocomposite materials absorb water and ultimately loss mechanical properties that affect service life. In this work, a biocomposite material with superhydrophobic surface was prepared by reinforcing waste polypropylene with sisal (Agave sisalana) fibers. The biocomposite was prepared by mixing waste polypropylene and sisal fiber with 5%, 10%, 15%, and 20% fiber loading. Based on characterization results, the composite with 15% fiber content is considered as optimum ratio. Physicochemical properties of composites were evaluated using standard American Society of Testing Materials including biodegradability test and chemical resistance test. The biodegradability of the composite before surface modification was determined by calculating weight loss and found to be 0.11%, 4.62%, 7.15%, and 10.97% for 0%, 5%, 10%, and 15% fiber loadings, and their tensile strength was $10.25\pm 0.05$ , $14.47\pm 0.02$ , $14.48\pm 0.02$ , and $19.90\pm 0.09\text{MPa}$ for 0%, 5%, 10%, and 15% fiber content, respectively. The surface of the composite was modified for hydrophobicity by etching the surface with chromic acid followed by treating with stearic acid. The FTIR and the SEM images of unmodified and modified (superhydrophobic) surface of composites clearly state the significant difference in chemical composition and surface structure, respectively. The superhydrophobicity of the surface-modified biocomposite was defined by its self-cleaning and low wet ability properties.

Fabrication of Activated Carbon Fibers with Sheath-Core, Hollow, or Porous Structures via Conjugated Melt Spinning of Polyethylene Precursor

Using polyethylene as carbon precursor, we have fabricated cost-effective carbon fibers with a sheath-core structure via conjugate melt spinning. Low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were used as the sheath and core of the fiber, respectively, while sulfonation with sulfuric acid was conducted to enable the crosslinking of polyethylene. We demonstrated that carbonization and activation of the sheath-core-structured polyethylene fiber can result in a well-developed microporous structure in the sheath layer, and due to the core-sheath structure, the resulting activated carbon fibers exhibit a high tensile strength of ~455 MPa, initial modulus of ~14.4 GPa, and Brunauer-Emmett-Teller (BET) surface area of ~1224 m²/g. Finally, activated carbon fibers with a hollow, sheath-core, and porous were successfully fabricated by controlling the degree of crosslinking of the LDPE/HDPE sheath-core fiber.

Effect of surface morphology change of polystyrene microspheres through etching on protein corona and phagocytic uptake

Surface physicochemistry properties of polymer particles are crucial for protein corona formation and macrophage phagocytosis when they contact with living body. In this work, polystyrene microspheres (PS-MSs) were selected as a model of polymer microparticles and fabricated by chromic acid etching through controlling conditions to obtain different surface morphology structures and to investigate their effect on the protein adsorption and phagocytic uptake of PS-MSs. The adsorption of bovine serum albumin (BSA) and fibrinogen (FIB) on PS-MSs showed almost the same tendency, i.e. the etched PS-MSs presented lower protein adsorption compared with original microspheres. The adsorption of BSA and FIB was the lowest when the protuberances on the etched surfaces were maximum and the size of the protuberances was minimum. Furthermore, the surface morphologies of PS-MSs were influenced in return not only by the amounts of proteins but also by protein types. Meanwhile, the macrophages phagocytosis of PS-MSs depended on the amounts and kinds of adsorbed proteins, especially the albumin content. In a word, phagocytosis and protein adsorption can be regulated by microsphere morphologies through etching, which provides a promising strategy to avoid invalid uptake for polymer particles such as drug delivery carriers.

Preparation of Polyethylene and Ethylene/Methacrylic Acid Copolymer Blend Films with Tunable Surface Properties through Manipulating Processing Parameters during Film Blowing

Polymer films based on polyethylene (PE) and ionomer ethylene/methacrylic acid (EMAA) copolymer blend were prepared by film blowing, whose surface properties were tuned by varying processing parameters, i.e., take up ratio (TUR). Blends of PE/EMAA copolymer were firstly prepared by the melt-mixing method, before being further blown to films. The wettability of the film was investigated by measuring the contact angle/water-film encounter time, and optical properties, i.e., the haze and transmittance. The wettability was found to be enhanced with the increase of TUR. So too was the haze, while the transmittance was found to be almost independent of TUR. The XPS and AFM results directly show the increasing polar functional groups (-COO^-) on the surface and roughness with increasing TUR. Further analysis of the 2D SAXS and WAXS unveiled the origin of the invariant transmittance, which resulted from the minor change of the crystallinity and the monotonic increase of the haze, with TUR resulting from the evolution of crystal orientation. In addition to other post-modification methods, the current study provides an alternative route to prepare large-scale PE films as the template for the advanced potential applications, i.e., covering in the layer of roof, the privacy of protective windows, and multitudes of packaging.

Analysis of partially sulfonated low density polyethylene (LDPE) membranes as separators in microbial fuel cells

Sulfonated low density polyethylenes (LDPEs) in varied molar ratios have been analyzed as separating barriers in microbial fuel cells (MFCs) for bioelectricity production.

A nanocomposite membrane composed of incorporated nano-alumina within sulfonated PVDF-co-HFP/Nafion blend as separating barrier in a single chambered microbial fuel cell

Nano-Al₂O₃ is incorporated within the blend of sulfonated PVDF-co-HFP/Nafion in varying molar ratios for the preparation of nanocomposite membranes.

Acid catalysed cross-linking of poly vinyl alcohol (PVA) by glutaraldehyde: effect of crosslink density on the characteristics of PVA membranes used in single chambered microbial fuel cells

In the present study, acid catalysed cross-linking of poly vinyl alcohol (PVA) with varying concentrations of glutaraldehyde was analyzed and the cross-linked PVAs were utilized as membrane separators in single chambered microbial fuel cells (MFCs).

Crosslinked inter penetrating network of sulfonated styrene and sulfonated PVdF-co-HFP as electrolytic membrane in a single chamber microbial fuel cell

In the present study, semi-IPN membranes of sulfonated styrene (SS) and sulfonated PVdF-co-HFP membranes have been analyzed as a polymer electrolyte membrane in single chamber microbial fuel cells (MFCs).