Pure Polymer Research Articles

Development of polyvinylpyrrolidone, inorganic nanoparticles, and lithium carbonate nanostructured systems

AbstractNanocomposites with inorganic nanofillers spread in a polymer matrix have been used for the development of pharmaceutical systems to treat mental illnesses such as bipolar disorder and Alzheimer's disease. In this study, nanostructured particles using a solution intercalation technique combined with a spray‐drying process using polyvinylpyrrolidone (PVP), montmorillonite, titanium dioxide, and lithium carbonate, with the aim of designing a new drug delivery system. XRD and low‐field nuclear magnetic resonance analyses showed that PVP/MMT 1% achieved an intercalated/exfoliated morphology. However, the incorporation of TiO2 nanoparticles into the PVP matrix did not affect its structure, indicating that there was not a strong interaction between the polymer and the TiO2 nanoparticles. Thermal analysis did not reveal any changes in the nanocomposites compared to the pure polymer. Scanning electron microscopy (SEM) analysis revealed a pseudo‐spherical shape, and SEM‐energy‐dispersive x‐ray spectrometry (EDS) confirmed the dispersion of MMT in the PVP matrix. The introduction of lithium carbonate into the PVP/MMT matrix created a new system with higher molecular mobility; the drug introduction increased the mean droplet size, and the zeta potential remained negative. Overall, the results indicate that the applied methodology can produce a new nanostructured particle as a drug delivery system.

Why Volume and Dynamics Decouple in Nanocomposite Matrices: Space that Cannot Be Accessed is Not Free.

Polymer nanocomposites have important material applications and are an ongoing focus of many molecular level investigations, however, puzzling experimental results exist. For example, specific volumes for some polymer nanocomposite matrices are 2% to 4% higher than for the neat polymer; in a pure polymer melt this would correspond to a pressure change of 40 to 100MPa, and a decrease in isothermal segmental relaxation times of 3 to 5 orders of magnitude. However, the nanocomposite segmental dynamics do not show any speed up. We can explain this apparent uncoupling of dynamics from specific volume, and the key is to consider the system expansivity, i.e., the temperature dependence of the volumetric data, together with the concept of limiting volume at close liquid packing. Using pressure, volume, temperature data as a path to both, we are able to predict the effect of nanoadditives on the accessible, i.e., free, space in the material, which is critical for facilitating molecular rearrangements in dense systems. Our analysis explains why an increase in specific volume in a material may not always lead to faster segmental dynamics.

Investigation of miscibiliy and physicochemical properties of synthetic polypeptide with collagen blends and their wound healing characteristics

A suitable condition is needed to foster a rapid recovery of wounds, which is a dynamic and intricate process. The development and characterization of mats of plastic-like peptide polymer (PLP) with collagen for wound healing applications are reported in this work. Viscosity parameters such as the Huggins coefficient [KH], the intrinsic viscosity [η], α by Sun, ∆[η]m by Garcia ∆B and μ suggested by Chee, ∆K, and β advocated by Jiang and Han, recommend the miscibility of the polypeptide in solution phase. Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) methods in a solid phase. Thermal characteristics using a differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) showed higher stability for the blends than the pure polymers. The collagen and PLP blends showed exceptional in vitro cytocompatibility, and the in vivo wound-healing studies on the Sprague-Dawley rats demonstrated faster wound healing within two weeks compared to the cotton gauze-treated injuries. Therefore, these membranes can be a possible alternative for treating skin injuries.

Bio-Based White Eggshell as a Value-Added Filler in Poly(Lactic Acid) Composites

Based on its positive environmental impact, poly(lactic acid) (PLA) has been a gradual substitute for synthetic plastics used in diverse applications. The use of industrial limestone (ILS) as a filler in polymers can have advantages of changing the properties of pure polymers. Waste eggshells (WE) can be seen as an alternative filler to ILS as they are also a source of calcium carbonate. To assess the feasibility of both filler types and sizes, PLA composites were manufactured by injection molding with filler contents of 5, 10, and 20 wt.%. Tensile, flexural, and impact mechanical properties were evaluated in addition to water absorption. One-way analysis of variance (ANOVA) was performed to determine whether statistically significant differences among the measured mechanical properties existed. Scanning electron microscopy (SEM) was used to view the morphology of the fillers and fractured surfaces. The composite tensile strengths and flexural strengths performed the best when filler loadings were 5 wt.% and 10 wt.%, respectively, for both filler types. The tensile and flexural modulus both increased with filler loadings. The impact strength for the composites was obtained at a threshold level of 5 wt.% filler loadings for both filler types and slightly better for smaller particles sizes. ANOVA identified statistically significant differences for the mean mechanical property values evaluated. SEM showed the fractured surfaces of the PLA composites were different from the pure PLA indicating some transformation occurred to the matrix. The weight gains due to water absorption were observed to increase with increase in content of both filler types while the smaller particles had slightly higher water weight gains. Although the composites containing ILS fillers had somewhat enhanced mechanical properties over the WE-filled composites, the end application will dictate which filler type to use in PLA.

Stretchable and transparent alginate ionic gel film for multifunctional sensors and devices

Flexible and stretchable substrates based on pure natural polymers have attracted widespread attention for next-generation “green” electronics. However, fabrication of stretchable and “green” electronic sensors with integrated high stretchability, optical transmittance and good conductivity still remains tremendous challenges. Herein, alginate ionic gel films (AIGFs) with integrated high stretchability (tensile strength of 4.13 MPa and 191.1 % fracture strain) and excellent transparent properties (transparency of ∼92 %) are achieved by the glycerol inducing physical crosslinking and CaCl2 initiating ionic crosslinking, a simple soaking and drying strategy. The obtained gel films not only exhibit good ionic conductivity, but also high reliability, wide-range sensing, and multiple sensitivity to external stimulus. More importantly, these ionic conductive gel films as green substrates are successfully utilized for construction of flexible and patterned optoelectronic devices. This promising strategy will open up new powerful routes to construct highly stretchable, transparent, and ionic conductive substrates for multifunctional sensors and devices.

Mechanical and thermal characterization of additive manufactured fish scale powder reinforced PLA biocomposites

This research work is aimed to convert fish scale wastes as an effective reinforcement in polylactic acid (PLA) as a new bio-composite filament for fused deposition-based 3D printing applications. Various concentrations of fish scale particles (0, 10, 20, and 30%) were used to make the filaments. The performance of the developed filaments was assessed by printing the filament into various test specimens to perform tensile, flexural, impact, hardness, and water absorption experiments as per the ASTM standards. The outcomes of the results show that the PLA/fish scale powder (20%) composite has performed well than the remaining composites. Furthermore, the adding 20% fish scale powder increased the tensile strength and flexural strength of the 3D printed PLA composite by 15% and 39.78% respectively. This is evident that the novel bio-composite exhibited better properties than the pure polymer making it a potential replacement as bone-grafting material and scaffolds for bio-engineering applications.

Tribological performance of polyamide 6/wax blend for rolling bearing, bushing and gear applications

Today, machine manufacturing is developing rapidly and plastic materials are preferred in some parts of these machines. Rolling bearings, gears, bushings and rollers are some of the machine elements manufactured from plastic in recent years. The working life of the aforementioned machine elements actually depends on the working conditions as well as the material. At the same time, the speed and load carrying capacity of the machine elements or counter materials during operation determine the life of the plastic material. In this experimental study, polyamide 6 polymer, which is among the engineering plastics used in rolling bearings, gears, rollers and bushings, was used. In addition, PA6 polymer blends with 6% wax solid lubricant were produced to increase wear resistance and their tribological performances were investigated. The polyamide 6/wax blend was first produced in granule form in twin screw extruder by compound production method. Then, test specimens were injection molded using the granules. AISI 316L stainless steel was used as a counter-disc in tribology tests. The tests were carried out under dry sliding conditions and at room temperature. Wear tests were carried out on a pin-disc wear tester at two different loads (50 N and 100 N) and four different sliding speeds (0.5, 1.0, 1.5 and 2.0 m/s). The coefficient of friction and specific wear rate of the materials were determined. According to the test results, an increase in the coefficient of friction and specific wear rate of both PA6 polymer and PA6/6% wax blend was observed with increasing sliding speed. At the load and speed ranges studied, the coefficient of friction of pure PA6 polymer varied between 0.25 and 0.36, while the coefficient of friction of PA6/6% wax blend varied between 0.10 and 0.13. The wear rate of PA6 polymer was obtained in the range of 1.2-12x10-4 mm3/Nm, while the wear rate of PA6/6% wax blend was obtained in the range of 1.2-3.0x10-5 mm3/Nm. The addition of 6% wax to PA6 polymer caused a significant decrease in both friction coefficient and wear rate and contact surface temperature.

A Study of the Physical Properties of Nanoscale Dental Fillings

Background:
 A compound is defined as the substance that arises from the mixing of two different substances, and the new materials produced have new properties that differ from the properties of the primary materials. The material produced has a cohesive structure. A compound consists of two basic components, the base material called the "matrix" and the additive called the "filler". The matrix is a polymer, and the filler is different from the type of polymer; it is an inorganic substance like minerals. The filler within the crystalline medium (matrix) is randomly distributed; this occurs because the particle size of the two materials (polymer and filler) are nearly equal and separate when the size of the filler particles is small relative to the size of the polymeric particle.
 Materials and Methods:
 The mechanical (hardness and compressive strength) and ultrastructural properties were measured by atomic force microscopy (AFM) for different concentrations of the added nanomaterials are (0, 2.5, 5 and 7.5) wt%. With the casting method, to be used to prepare samples of structural properties, special molds have been used to examine the mechanical properties (hardness and compressive strength), through which the surface can be viewed with high precision very small (100 µm to less than 1 µm) . Compressive strength test is important. It is very important for dental materials as these materials must have mechanical properties similar to the teeth in order to resist chewing forces and it is compressive in a force range of (450-500) newtons. The compressive strength test is very important for dental materials as these materials must have mechanical properties, for the purpose of measuring the compressive strength, cylindrical samples with a diameter of (3 mm) and a thickness of (6 mm).
 Results:
 The (AFM) images showed the surface shape of the nanopolymer (PMMA) before and after the addition of nanomaterials, where we notice in a clear picture the increase in the roughness, the mean root value (RMS) and the average particle size. After adding the oxides, and increasing the added proportions, since the roughness when adding nano-oxides is useful for tooth adhesion, and despite the difference in (roughness) values, the values are still less than (200 nm), which was reported as an initial point for the accumulation of bacterial plaques and the risk of incidence of caries and periodontitis, and it can be assumed that the surfaces evaluated in this study have a smooth surface. Which does not represent any risk of scale build-up. We also notice when studying and examining the mechanical properties of hardness, as hardness is the surface resistance to cutting and scratching, as we notice an increase in hardness with increasing concentrations of nanomaterials. The compressive strength test of the nanofilling was also carried out before and after the addition of nanomaterials, as we notice an increase in the amount of compression with the increase in the percentage of addition of nanomaterials as well. These oxides are very safe and harmless to the human body.
 
 Conclusion:
 Samples of novel nanocomposites (PMMA-ZnO-MgO) for dental filling applications have been synthesized. The addition of nanomaterials to the pure polymer leads to an increase in the surface roughness, as well as the roughness rate, the average root value (RMS), and the average grain size with an increase in the proportions of impurities, which leads to an increase in the cohesion and hardness of the filling, as the increase in agglomerations leads to an increase in the cohesion of the filling with the teeth and its durability. While the higher the added percentage, the roughness increased, as we found the highest roughness at (7.5)%, which reached (34.72 nm). Therefore, the filler achieved clear structural properties and a radical change in the structure of the polymer used as a result of the addition of nanomaterials, in addition to durability, quality, safety, and suitability for human tissues. The study showed the mechanical properties and proved that the material (MgO) containing the nano-filling has resistance to the compressive strength test, as it reached the highest resistance to the compressive strength of the addition ratio (7.5)%, which amounted to (150 MPa), while the hardness reached (90.7 MPa) at (7.5%), where The physical properties increase with the increase in the percentage of added nanomaterials.

Continuous productions of highly fluorescent carbon dots and enriched polymer nanofibers via microfluidic techniques

Carbon dots (CDs) have shown great promise in various fields owing to their fascinating properties. However, most of high-performance CDs are usually synthesized upon intermittent operations, which are difficult to produce continuously in batch. In this regard, we develop a robust aluminum-based microfluidic chip reaction platform with imbibition-injection cycle feeding and ease of scale-up production, allowing the rapid and continuous synthesis of highly fluorescent CDs. The as-prepared CDs possess excellent optical properties, including high photoluminescence (PL) quantum yield (QY) of 71%, narrow full width at half maximum (FWHM) of 65 nm by optimizing the parameters of reaction. Combined with electro-microfluidic spinning, the continuous production of fluorescent enriched CDs/polymer nanofibers could further be realized. CDs/thermoplastic polyurethane (TPU) and CDs/polyamide 6,6 (PA66) nanofibers are prepared to exhibit enhanced mechanical properties with tensile strength 2.9 and 4.1 times higher than those of the pure polymer matrix, respectively. This work contributes a new kind of microfluidic chip for nanomaterial synthesis, and paves a way toward rapid and continuous preparation of high-performance CDs and CDs/polymers nanofiber films by microfluidic techniques.

The Role of Polymer Chain Stiffness and Guest Nanoparticle Loading in Improving the Glass Transition Temperature of Polymer Nanocomposites.

The impact of polymer chain stiffness characterized by the bending modulus (kθ) on the glass transition temperature (Tg) of pure polymer systems, as well as polymer nanocomposites (PNCs), is investigated using molecular dynamics simulations. At small kθ values, the pure polymer system and respective PNCs are in an amorphous state, whereas at large kθ values, both systems are in a semicrystalline state with a glass transition at low temperature. For the pure polymer system, Tg initially increases with kθ and does not change obviously at large kθ. However, the Tg of PNCs shows interesting behaviors with the increasing volume fraction of nanoparticles (fNP) at different kθ values. Tg tends to increase with fNP at small kθ, whereas it becomes suppressed at large kθ.

A mechanical, thermal and electrical properties study of novel vulcanised blends of poly(epichlorohydrin) elastomer with polyaniline dodecylbenzenesulfonate

With good mechanical and thermal properties, elastomers having appreciable electrical conductivity may potentially be developed as smart materials for applications such as strain sensors, artificial muscles or flexible biosensors. With such applications in mind, the purpose of this study was to investigate the structure-properties relationships of new vulcanised blends of a poly (epichlorohydrin) elastomer (PECH) and electrically-conducting polyaniline dodecylbenzenesulfonate salt (PAni.DBSA). PAni.DBSA, synthesised by a published method, was blended with PECH and vulcanised with a commercial sulfur cross-linking agent in an internal mixer. The morphological, mechanical, thermal and electrical properties were examined as a function of the amount of PAni.DBSA in the blends. The electrical conductivities increased with the proportion of polyaniline, showing a low percolation threshold of about 1 wt. % (1.07 vol %) PAni.DBSA (from about 10−12 to 10−10 S cm−1), and a second stage of percolation around 5 wt.%, ultimately reaching around 3 × 10−8 S cm−1. The results from microscopy and other techniques indicated that a mixture of micro- and nano-sized PAni.DBSA particles was dispersed in the elastomer matrix at compositions above 5 wt. % PAni.DBSA. The infrared spectra of vulcanised PECH-PAni.DBSA blends showed features of the pure polymers, with some notable peak shifts due to intermolecular interactions between the constituents. Thermal properties of the conductive blends were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stabilities of the blends were strongly dependent on the ratio of PAni.DBSA to PECH, and the two components inhibited the thermal decomposition of each other. The elastomer’s glass transition temperature (Tg) was determined by thermomechanical analysis (TMA); each blend showed only one such transition, at temperatures that increased monotonically with the proportion of PAni.DBSA present, indicating a significant degree of molecular interaction between the two polymers.

PVC polymer/ZnO/NiO/Co3O4 nanocomposites: Toward improved optical properties

AbstractUndoped and doped polyvinyl chloride (PVC) with zinc, nickel and cobalt oxides, ZnO/[(1−x)NiO/xCo3O4], composites were fabricated using co‐precipitation and casting techniques. The different phases present in the nanofiller ZnO/[(1−x)NiO‐xCo3O4] mixed oxides were determined using synchrotron x‐ray diffraction technique. X‐ray diffraction, scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDS) analysis techniques were used to investigate the structure, composition, and morphology of pure and loaded PVC with nanofiller oxides. In general, compared with pure PVC, the absorbance was greatly enhanced, especially in the UV region, upon loading ZnO/[(1−x)NiO‐xCo3O4], but it changed irregularly with the cobalt oxide (Co3O4) content (x). The direct and indirect optical band gaps of pristine PVC (4.14, 4.12 eV) reduced irregularly to minimum values 3.97 and 3.23 eV respectively for the polymer doped with ZnO/[0.3NiO/0.7Co3O4]. The refractive index was enhanced in the visible and IR regions and attained its highest value for PVC doped with zinc oxide/nickel oxide (ZnO/NiO) only (x = 0.0). NiO and Co3O4 ratios affect the linear and nonlinear optical parameters. The emitted spectra from pure and doped PVC polymers with the composite oxides [ZnO/[(1−x)NiO‐xCo3O4] under different excitation wavelengths were also explored. The FL intensity enhanced for the excitation wavelengths (λexc) = 380 and 434 nm but quenched for λexc = 317 nm. The loaded polymers absorb UVA, UVB, and UVC rays and are good candidates for solar cell applications.

Flexible composite films with enhanced piezoelectric properties for energy harvesting and wireless ultrasound-powered technology

In the last years, ultrasound energy harvesting has emerged as the most promising technique for wireless power supply of implanted medical devices. These devices require flexible piezoelectric materials with high piezoelectric response in the ultrasonic range. Here we report on bio-compatible NBT-BT/PVDF flexible composites, with variable filler content up to 50 vol%, prepared by a properly designed and optimized process, which incorporates in a complex connectivity pattern fully sintered NBT-BT crystalline powders in a PVDF matrix. The dielectric constant of the flexible composites increased from 10 of pure PVDF polymer to 110 of composite films with 50 vol% NBT-BT content, while the high frequency piezoelectric d33 constant increased from 0.2 pC/N to 33 pC/N for the same samples. The composite with 50 vol% NBT-BT exhibits the figure of merit for the harvested ultrasound energy d33g33 ≅ 1.54 × 10−12 m3/J, which is comparable to the figure of merit for the NBT-BT piezoelectric ceramic (1.8 × 10−12 m3/J) and higher than other reported results for random composites. Based on these results, this study provides an easy method to fabricate random flexible piezoelectric composites with enhanced high frequency piezoelectric response and high energy density harvested from an ultrasound source.

A diffusion–deformation model with damage for polymer undergoing rapid decompression failure

Green hydrogen is emerging as one of the most promising alternatives to replace fossil fuels. While hydrogen gas has a good energy density by weight, its poor energy density by volume requires it to be stored under high pressure for commercial use. The hydrogen infrastructure developed to handle this high pressure hydrogen contains multiple components made of polymers such as O-rings, pipes, hoses, and inner liners of storage tanks. Although polymers do not react chemically with hydrogen gas, they undergo a mechanical failure when high pressure hydrogen gas is suddenly depressurized. This phenomenon known as ‘rapid decompression failure’ (RDF) occurs due to the diffusion of hydrogen through polymer and getting trapped inside preexisting cavities or voids.In this paper, a continuum mechanics-based coupled diffusion–deformation-damage model was developed to predict the hydrogen distribution, stress distribution, and damage propagation inside the polymer while it undergoes rapid decompression failure. The polymer was modeled as a hyperelastic material because it represents the nonlinear material response observed in uniaxial tensile tests perfectly. The effect of hydrogen diffusivity, preexisting cavity size, cavity location, applied hydrogen pressure, and depressurization rate on damage initiation was studied. It was found that the coefficient of diffusion plays an important role in damage initiation and damage was mostly concentrated in the inside areas rather than near the surface. Experiments were conducted with ethylene propylene diene monomer (EPDM) which agreed well with the predicted trends using the given model. The effect of adding carbon black and silica filler particles and plasticizer to the pure EPDM polymer was also studied. It was found that damage during RDF decreases with the addition of fillers, but increases with the addition of the plasticizer. Finally, the damage evolution in the presence of two cavities was also studied, and was found that the interaction of stress fields around the cavities alters the damage occurring during RDF.

Carbon based Nanofillers Embedded Fouling Resistant Polyvinyl Chloride Nanocomposite Membranes for Oil-water Separation

Herein, we discussed the development of polyvinyl chloride (PVC) based nanocomposite ultrafiltration (UF) membrane by embedment of nanofillers such as carbon black (CB), graphitized carbon black (GCB) or mesoporous carbon, multiwalled carbon-nanotube (MWCNT), carboxylated multiwalled carbon-nanotube (CMWCNT) with increased permeate flux and fouling resistance. Ultrafiltration membranes were prepared using casting solution of PVC in N, N-dimethylacetamide (DMAc) solvent with polyethylene glycol with average MW 600Da (PEG-600) as additives with and without nanofillers. Membranes prepared were characterized in terms of pure water permeability, separation of single uncharged solutes like polyethylene oxide (PEO), water contact angle and tensile strength. Membranes were tested with synthetic oily waste water (1000 ppm oil-water emulsion) followed by pure water flux recovery after cleaning by flow reversal flushing using deionized water. The product flux was observed to increase by ~35.5%, ~11.4% & ~44.4% in PVC-GCB, PVC-MWCNT and PVC-CMWCNT membranes respectively than the pure PVC membranes. The flux recovery on cleaning of fouled membranes is ~56% in pure PVC membrane, whereas it is ~72%, ~74% & ~80% for PVC-GCB, PVC-MWCNT and PVC-CMWCNT membranes respectively. Incorporation of the carbon based nanofillers in pure polymer matrixes not only enhances the water permeability with marginal decrease of the separation performances but also it increases mechanical strength and the fouling resistance of the membranes. The carbon fillers-based PVC nanocomposite membranes are found promising candidates for cleaning oily wastewater.

Optical, and electrical conductivity properties of ZnO and TiO2 nanoparticles scattered in PEO-PVA for electrical devices

Polyvinyl alcohol (PVA)/Polyethylene oxide (PEO) has been blended and doped with zinc oxide and titanium oxide nanoparticles. Different concentration of the prepared ZnO and TiO2 NPs make a change in PVA/PEO- ZnO/TiO2 NPs nanocomposites films improve the characterization of PVA/PEO. XRD scans show two broad peaks at about 18.8° and 21.95° for PVA/PEO blend. XRD scans show of PVA/PEO- ZnO/TiO2 NPs nanocomposites films obtain the hexagonal structure of ZnO and the anatase phase of TiO2 NPs. The addition of dopants in the PVA/PEO blend results in a reduce in degree of crystallinity compared to the pure blend. This is evident from the decrease in the crystallinity index (Xc value) from 37.25 to 22.31. This reduction in crystallinity can have implications for the material's opticla, thermal, and electrical properties, and should be considered when evaluating its suitability for specific applications. FT-IR results show changes in intensity of bands that could be assigned to the strong interaction between PVA/PEO and ZnO/TiO2 nanoparticles. The Egopt values reduced by raising laser ablation time due to unstructured defects that enhanced the density of localized states in the band gap, dropping from 4.72 eV to 3.0 eV for direct transitions and from 3.05 eV to 2.35 eV for indirect transitions. It undergoes complete decomposition at a higher temperature, resulting in a mass percentage of 45 ± 0.3 wt%. In comparison, the pure polymer blend sample has a lower mass percentage of 33 ± 0.03 wt% during the same temperature range. The fabricated system of PVA/PEO- ZnO/TiO2 NPs nanocomposites films showing improved in AC conductivity and dielectric characteristics and could be suggested in electrical applications.

Thermal Conductivity of Polyvinylidene Fluoride Films with a Multi-Scale Framework.

The orientation of amorphous regions in pure polymers has been noted to be critical to the enhancement of thermal conductivity (TC), but the available reports are still rather few. Here, we propose to prepare a polyvinylidene fluoride (PVDF) film with a multi-scale framework by introducing anisotropic amorphous nanophases in the form of cross-planar alignments among the in-planar oriented extended-chain crystals (ECCs) lamellae, which show an enhanced TC of 1.99 Wm-1 K-1 in the through-plane direction (K⟂) and 4.35 Wm-1 K-1 in the in-plane direction (K∥). Structural characterization determination using scanning electron microscopy and high-resolution synchrotron X-ray scattering showed that shrinking the dimension of the amorphous nanophases can effectively reduce entanglement and lead to alignments formation. Moreover, the thermal anisotropy of the amorphous region is quantitatively discussed with the aid of the two-phase model. Superior thermal dissipation performances are intuitively displayed by means of finite element numerical analysis and heat exchanger applications. Moreover, such unique multi-scale architecture also results in significant benefit in the improvement of dimensional stability and thermal stability. This paper provides a reasonable solution for fabricating inexpensive thermal conducting polymer films from the perspective of practical applications.

Activated Gas Transport in Polymer-Grafted Nanoparticle Membranes

Carbon capture and related gas separation processes are critical tools in our efforts to combat climate change. While polymer membranes are seen as a central construct to achieve these goals, their performance needs further improvement to meet current sustainability goals. It is in this context that membranes composed of polymer-grafted nanoparticles (GNPs) become highly germane. Previous work has shown that gas transport in pure GNP membranes can be strongly enhanced relative to that in the corresponding neat polymer. Additionally, we found that larger gases display greater degrees of permeability enhancement than smaller ones. There is currently no clear understanding of these two underpinning facts, and to address this issue, we have characterized the activation energy driving the permeability of multiple gases in several GNP membranes. Our results show that gases smaller than a critical size display the same activation energy as in the native polymer─any enhancement therefore is associated with changes in local gas/chain dynamics, e.g., the speeding up of polymer dynamics due to the local stretching in a brush conformation. Our results are consistent with the notion that small gases are present in the whole polymer layer. Conversely, larger gases show substantially lower activation energies and, in contrast to the neat polymer, exhibit essentially no dependence on penetrant size. Sorption measurements illustrate that this is a result of the enhanced solubility of larger gases in GNPs, relative to that in the pure polymer, which is reflected in their significantly more favorable enthalpies of solvation. Larger gases thus preferentially sorb into the interstitial spaces in the GNP assembly, thereby resulting in even higher permeability enhancements in the GNP layers relative to smaller gases. GNPs, therefore, provide us with multiple handles to control gas transport, a fact that offers critical insights into their utility for gas separations.

Property Improvement of Polybutylene Succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic Acid (PLA) Films with PCL (Polycaprolactone) for Flexible Packaging Application

Nowadays, developing highly biodegradable polymer films for flexible packaging applications is one of many researchers' demanding and challenging tasks. Conventional plastics/polymers are still being extensively used, creating environmental pollution. Because most of the commercially available plastic products are marketed as biodegradable are not truly biodegradable and have several limitations for making flexible packaging films. The main objective of this work is to manufacture biodegradable polymer blends, with the best performance characteristics, for flexible packaging applications. The paper focused on improving the properties, i.e., tensile, barrier, and biodegradation properties, of commercially available polymers such as Polybutylene succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic acid (PLA) by blending with Polycaprolactone (PCL) for flexible packaging application. Polymer films of various compositions such as PBS-PCL, PHB-PCL, and PLA-PCL blends were fabricated by injection molding and hot pressing. The characterization analysis included analyzing polymer blends' tensile and water vapor barrier properties, as per ASTM D882-18 method and ASTM E96-16 method, respectively, following that biodegradation analysis in compost (ASTM D5338-15 method) and seawater medium (ASTM D6991-17 method) of the polymer blends, and analysis of PCL blends' effect. The research showed that compared to the pure polymer blends such as PBS, PHB, and PLA blends, polymer blends with 20% of PCL has increased tensile elongation by 26.3%, 68%, and 171%, respectively, and the water vapor barrier properties were increased by 28.3%, 26.8%, and 30.3%. the biodegradation rate in compost medium was increased by 21.9%, 6.4% and 21.2%, and the biodegradation rate in seawater medium was increased by 31%, 7.5%, and 16.6%, respectively, even though a slight decrease in tensile strength. In conclusion, the polymer blends with 20wt% of PCL provide overall improved of polymer properties.

Thermal Degradation Kinetics of Completely Biodegradable and Biobased PLA/PHB Blends

In this article, the influence of blend ratio of plasticized poly(lactic acid)/poly(3-hydroxybutyrate) (PLA/PHB) and chitin nanoparticles (ChNP) nanocomposites on the thermal stability and degradation kinetics has been investigated using thermogravimetric analysis under nitrogen atmosphere at four different heating rates (i.e., 5, 15, 30, and 50°C/min). The derivative thermogravimetric curves have indicated single-step and two-step degradation processes for individual polymers and polymer blends, respectively. It suggests immiscibility or partial miscibility between the polymers. The degradation kinetic parameters were studied over the 30 – 500°C temperature range by using the Kissinger-Akahira-Sunose (KAS) and Vyazovkin isoconversional methods under non-isothermal conditions. The average values of the effective activation energies of the deconvoluted PHB and PLA peaks in the PLA:PHB 70:30 (B73) blends were higher than those of the pure polymers, while in the PLA:PHB 60:40 (B64) blends were lower, which was attributed to the different morphology of the blends. Furthermore, the effective activation energy of the nanocomposites diminished due to the catalyzing effect of the chitin nanoparticles. By means of the invariant kinetic parameters (IKP) method, it was possible to evaluate the preexponential factor and the activation energy of the blends without any assumptions concerning kinetic model. The invariant activation energies calculated were in accordance with the ones estimated by the isoconversional methods. Finally, Avrami-Erofeev function was determined as the most probable kinetic mechanism of the systems studied by applying the Sestak-Berggren equation.