The heavy reliance on petrochemical polymer foams in production and consumption has triggered escalating plastic pollution. Herein, fully bio-based and biodegradable poly(lactic acid) (PLA) open-cell foams for selective oil absorption were developed using a green supercritical CO2 foaming method. For the purpose of not affecting the degradation of PLA, homogeneous PLA fiber (PLAF) was employed as nucleating agent and hard phase to regulate the cellular structure of foams. The incorporation of PLAF significantly accelerated the crystallization rate, thus reducing the crystallization half-time from 15.8 min to less than 1.0 min. The PLAF dramatically improved melt viscoelasticity owing to the formed network-like structures. During foaming, the unmolten PLAF not only increased cell density but also promote cell opening. The annealed PLA-5 foam exhibited excellent heat stability, retaining 62 % of its original height after pressing at 120 degrees C. Owing to the open-cell structure, the PLA-5 foam demonstrated high adsorption capacities for oils and organic solvents, ranging from 13.6 to 24.6 g/g, and maintained 87 % of its initial adsorption efficiency after 10 cycles. This study presents a facile approach for developing environmentally friendly foams used for oil-water separation.

During batch foaming, ultra-high molecular weight polyethylene (UHMWPE) presents a narrow foaming temperature window. This is a common challenge for many semicrystalline polymers and often leads to unsatisfactory foaming results. This study examines the foaming behavior of UHMWPE using supercritical COQ as a physical foaming agent, with a focus on the synergy between molecular weight, melt state and depressurization rate. Compared to the conventional rapid depressurization foaming schedule, a slow depressurization rate broadened the foaming temperature window of UHMWPE from 3 to 6 degrees C to 18 degrees C and allowed it to be foamed in a fully molten state. This phenomenon stems from the low melt strength of fully molten UHMWPE during rapid depressurization, whereas it exhibits high melt strength under slow depressurization. This relationship is also corroborated by hot tensile experiments performed at partially and fully molten state. Furthermore, slow depressurization also improved the cell morphology of UHMWPE foams produced at a partially molten state, especially, the phenomenon becomes more pronounced with increasing of molecular weight.

Flow-induced polymer melt can develop heterogeneity involving both quasi-ordered structures, namely, nucleation precursors (NPs) and partially disentangled chains (PDCs). These states can retain a memory that affects the subsequent crystallization process. In this work, the interplay between the NP and the PDC in isotactic polypropylene (i-PP) melt was investigated by rheological measurements, and its contribution to the crystallization behavior was assessed. After the application of a steady shear flow, which causes partial disentanglement, the characteristic re-entanglement time follows an Arrhenius temperature dependence with a much higher activation energy at temperatures below the equilibrium melting point, suggesting a cooperative motion of chain segments that are aligned and clustered by shear. With decreasing temperature, the unexpectedly long re-entanglement time, abnormally high activation energy, and increased entanglement density indicate that the NPs can provide extra physical entanglements that increase the melt viscosity and storage modulus, thereby postponing the re-entanglement process of the PDCs to the equilibrium melt state. Moreover, the origin of the flow-memory effect on crystallization was successfully investigated, revealing a synergistic interplay between the NPs and PDCs. The crystallization kinetics becomes slower, and the crystalline morphology changes from a shish-kebab structure to a spherulite with the increase of shear temperature and holding time. The relative shear efficiency, a measure for the flow-induced acceleration of crystallization kinetics, shows a double-decay trend, suggesting the sequential relaxation of the NP and the PDC. Finally, by changing the shear rate, shear strain, and molecular weight, the entanglement density can be efficiently adjusted, while the activation energy of the precursor cluster relaxation is basically unchanged.

Poly(ferrocenyldimethylsilane) (PFDMS) crystallizes slowly due to its unique “aromatic sandwich” structure, enabling crystallization over a wide temperature range. In this work, the morphology and growth kinetics of PFDMS lamellar crystals in ultrathin films were investigated using atomic force microscopy (AFM) and polarized optical microscopy (OM). As the crystallization temperature (Tc1) decreases from 90 to 65 °C, the lamellar growth rate decreases, and the growth mode transitions from linear to nonlinear, accompanied by a change in crystal morphology from rounded rectangular to elliptical shapes. In rounded rectangular lamellae, kinetic roughening occurs on specific growth faces, whereas in elliptical lamellae all growth fronts become kinetically roughened. In addition, AFM characterization of self-seeded PFDMS single crystals reveals that their orientational dispersion, quantified by FWHM/2 (half of the full width at half maximum of the Gaussian-fitted orientation distribution), increases with decreasing Tc1. Moreover, the FWHM exhibits an inverse scaling relationship with the plateau width (Wd∞) of depletion zone, i.e., FWHM ∼ Wd∞−1. Since the depletion zone width can serve as an effective measure of the diffusion length, these results demonstrate that diffusion-limited growth plays a key role in determining crystal growth kinetics and morphology, while also governing the evolution of internal crystallographic orientation in kinetically roughened monolayer lamellae.

In this study, a solvent-assisted foaming method via plasticization of ethyl lactate and enhanced CO2 diffusion was proposed to prepare microcellular cellulose acetate (CA) foams. Under the plasticization effect of ethyl lactate on CA, the glass transition temperature of CA30 (CA containing 30 wt% ethyl lactate) precursors was decreased to approximately 100 degrees C, thus decreasing the foaming temperature and broadening the foaming temperature window to 60 degrees C. By adjusting the foaming temperature and pressure, the expansion ratio of CA30 foams ranged from 2.3 to 21.6-fold. Samples with a smaller cell size (15 mu m) achieved a compressive strength of 0.17 MPa, which was four times higher than that of foams with larger cell size (50 mu m), when they had a similar expansion ratio. As the expansion ratio increased from 2.3 to 9.8-fold, the thermal conductivity of CA30 foams decreased rapidly, and then remained relatively stable. When the expansion ratio was 21.6-fold, the thermal conductivity was as low as 41.0 mW/(m & sdot;K).

High-performance polymer foams are becoming essentials in industries such as automotive and aerospace. Herein, poly(phenylene sulfide)/carbon fiber (PPS/CF) composite foams with high compressive properties were prepared by a melt-quenching foaming method. As the CF content increased from 0 to 30 wt%, the crystallinity of PPS changed from 48.2 % to 72.4 %. Compared with neat PPS, the tensile strength of the composites with 30 wt% CF increased from 63.3 MPa to 112.8 MPa and impact strength increased from 14.5 kJ/m2 to 25.4 kJ/m2. The composites also exhibited an enhanced viscoelasticity, which was conducive to foaming. By adjusting the foaming temperature, pressure, and CF content, foams with expansion ratio of 1.2-6.4-fold were prepared. Owing to the heterogeneous nucleation of CF, the cell density was increased and cell size was significantly reduced. The compression tests showed that the compressive strength of composite foams with 30 wt% CF was up to 2.7 MPa. After annealing, the compressive strength of foam with 20 wt% CF was further increased by 138.5 % owing to the enhanced crystallinity. The prepared PPS/CF composite foams exhibit good application prospects in the lightweighting of automotive and aerospace fields.

Conductive polymer microcellular foamed materials are a type of functional composite that combines lightweight cell structures with controllable conductivity. Their core feature lies in regulating the cell structure of the material through microcellular foaming technology, along with the introduction of conductive fillers or the intrinsic conductivity of the polymer, to achieve enhanced electrical performance. This paper systematically reviews conductive polymers and their microcellular foamed materials, highlighting research progress in foaming mechanisms, preparation processes, and functional applications. It first analyzes the key mechanisms of bubble nucleation, growth, and stabilization during the microcellular foaming of conductive polymers. Then, it elaborates on the research status and functional mechanisms of these materials in three typical application scenarios: electromagnetic shielding, flexible sensors, and thermal management. Finally, it outlines the future development directions of conductive polymer microcellular foamed materials in multifunctional integration, green fabrication, and intelligent applications, aiming to provide theoretical guidance and technical pathways for future research.

In the field of food colloids, selenium (Se) modification is considered a promising strategy for the development of organic selenium additives. However, the synthesis of Se-polysaccharide is frequently hindered by low selenium incorporation and uncontrolled molecular weight (MW) degradation. In this study, a collection of acidic deep eutectic solvents (ADESs), formulated from choline chloride paired with diverse carboxylic acids were developed as dual-functional media for the selenylation of locust bean gum (LBG). The resulting selenized LBG (SeLBG) exhibited a markedly enhanced Se content (up to 11,038 μg/g), representing a significant improvement over HNO3/Na2SeO3 and DMSO-based methods. Further analysis revealed significant correlations between ADES acidity (H0), polarity (ETN) and selenylation efficiency, with stronger acidity and higher polarity generally associated with increased Se incorporation. FT-IR and 13C NMR characterization confirmed the formation of selenite esters, primarily through substitution at the C-6 hydroxyl groups of mannose residues. Moreover, MW analysis demonstrated that polysaccharide degradation was modulated by both solvent acidity and polarity, where higher polarity was associated with greater molecular-weight reduction, which may be related to enhanced polysaccharide solvation and conformational changes. Importantly, computational analyses rooted in density functional theory (DFT) alongside molecular dynamics (MD) modeling indicated enhanced hydrogen-bonding affinity between ADESs and LBG enhanced solvation and exposed more reactive sites, thereby facilitating improved selenylation efficiency. This work demonstrated that tailoring the physicochemical properties of ADESs enables precise control over the Se content and MW of Se-polysaccharides, providing a robust strategy for the structure-oriented synthesis of bioactive glycan derivatives.

Against the backdrop of the global trends toward lightweighting, multi-functionalization, and greening of materials, polypropylene (PP) has been extensively applied owing to its advantages of low density and low cost. However, its inferior foaming performance fails to meet high-end application requirements, which is primarily attributed to its low melt strength and restricted crystallization behavior. In this paper, the five-dimensional selection mechanism and classification of components for PP micro/nanocomposites fabricated via supercritical foaming are systematically summarized. The regulatory effects of micro/nano additives on the crystallization, rheological properties, and foaming behavior of PP are quantitatively analyzed. The parameter optimization windows of three foaming processes, namely batch foaming, extrusion foaming, and injection foaming, are integrated (e.g., a foaming temperature of 150-170 °C and a saturation pressure of 8-20 MPa). Additionally, the application progress of PP micro/nanocomposite foams in fields such as automotive lightweighting (with a weight reduction rate of 64.29%) and building thermal insulation (with a thermal conductivity as low as 29 mW/(m·K)) is outlined. The core novel insight of this work lies in clarifying the unified mechanism of crystal refinement induced by reinforcing agents with different geometric morphologies, which is dominated by the synergy between heterogeneous nucleation and steric hindrance. This finding provides theoretical and technical guidelines for the industrial-scale preparation of high-performance PP foams.

This study presents a novel, lightweight and flexible PBAT/GNP/Ag composite film engineered for simultaneous high-performance thermal management and EMI shielding. Utilizing a facile vacuum filtration and hot-pressing approach, a parallel-oriented layered PBAT/GNP skeleton was constructed. Ag nanoparticles of varying sizes and loadings were subsequently incorporated via solution adsorption, forming a unique "brick-mortar-gravel" structure where GNP serves as the continuous conductive "brick" phase, PBAT acts as the "mortar" phase and Ag particles function as discrete "gravel". The composite film incorporating 20 nm Ag nanoparticles achieved ultrahigh in-plane thermal conductivity of ca. 81 W center dot m(-1) K-1, which is 90% higher than that of the PBAT/GNP composite film. Meanwhile, the highest electrical conductivity of 3696 S center dot m(-1) was achieved for this composite film, which is 133% higher than the film without Ag nanoparticles addition. Moreover, the composite film also exhibited outstanding EMI shielding effectiveness of above 45 dB in K-band, effectively blocking more than 99.99% of incident radiation, with a remarkable surface-specific shielding effectiveness of ca. 9500 dB center dot cm(2) g(-1). Finally, the PBAT matrix imparts necessary flexibility to the otherwise brittle GNP-dominated film. This improved bending tolerance, combined with a low density below 1.1 g center dot cm(-3), demonstrates a viable strategy in this work for constructing advanced multifunctional materials, which is crucial for applications in flexible electronics and EMI protection.

Naturally derived materials have attracted much attention owing to the demand of sustainability. In this work, bio-based polyamide was used to tailor the foaming behavior of poly(lactic acid) by dispersing into different geometric sizes. The results showed that both micro-sized spherical and fibrillar polyamide markedly shortened the half-crystallization time of poly(lactic acid) in isothermal crystallization process, while nanofibrils played a better role on promoting crystallization than submicron spheres. When the polyamide was in a fibrillar state, the blends exhibited a higher complex viscosity in low frequency region. With increasing frequency, the blend containing nanofibrils displayed an obvious disentanglement phenomenon. Regarding foaming, the micro-sized polyamide particles with larger diameter were more conducive to cell nucleation than that with smaller size. The nanofibrils led to the highest cell density of 1.46 × 109 cells/cm3 and smallest cell size of 22.5 μm in foams, and promoted the formation of open-cell structures. Owing to the reduced cell size, the collapse stress of foams containing polyamide was higher than that of poly(lactic acid) foam. This work provides a method for regulating cellular structure of polymers by controlling the geometric size of the second phase.

The effect of Form I nanocrystal size on the induction time (t i) of isotactic polybutene-1 (iPB-1) heterogeneous nucleation has been investigated using small-/wide-angle X-ray scattering (SAXS/WAXS). By controlling the crystallization temperature (T c1) of starting Form II and the transition time from Form II to Form I, respectively, we tune the height (h) and radius (r) of cylindrical Form I nanocrystals. A faster rate (i.e., a shorter t i) of heterogeneous nucleation on the larger nanocrystals (h similar to 57 nm, r similar to 23 nm) can be observed at the same mass fraction, even if the number density (N) of the smaller nanocrystals (h similar to 37 nm, r similar to 13 nm) is approximately five times that of the larger ones. In addition, we observed a dramatic increase (nearly 600%) in (1/t i)/N, representing the nucleation ability of individual nanocrystal, when h increases from similar to 37 to similar to 57 nm (by similar to 54%) at a constant r of similar to 15 nm, whereas (1/t i)/N only exhibits a similar to 110% increase when the nanocrystal increases its radius by similar to 120% at a constant h (e.g., similar to 37 nm). These results indicate that h, rather than r, plays a central role in heterogeneous nucleation. Further, in a size range of h = 27-57 nm, we found the t i scales with h according to a power law t i similar to h -alpha, where the exponent alpha increases with secondary crystallization temperature (T c2). This reveals that the impact of h on the heterogeneous nucleation rate intensifies as the critical nucleus size increases. Our findings demonstrate that such an experimental model system could shed light on investigating the size effect of polymer nanocrystals in heterogeneous nucleation.

The fabrication of polymer composite foams with several functions offers various advantages. Herein, we reported a highly efficient and mass-produced method for preparing polypropylene/carbon fiber/carbon black (PP/CF/CB) composite foams bonded with continuous CF reinforced PP prepregs. CFs were uniformly dispersed in PP via melt blending, but some agglomerations of CBs were observed owing to their little size. Compared with pure PP, the introduction of CB improved the thermal stability and flame retardance of composites. Owing to the homogeneity of polymer between composites and prepregs, they were well bonded by injection molding. The tensile strength of the samples bonded with prepregs was improved by 158.3-257.7 % for different filler contents. As CF and CB played the role of heterogeneous nucleation, and the high-pressure foam injection molding could easily tailor cellular structure by adjusting the holding time and mold temperature, composite foams bonded with two prepregs and with desired cells were successfully prepared. The injected foams with two prepregs had an enhanced electromagnetic interference shielding performance, which was 65.4 dB when the content was 10 wt% and 15 wt% for CF and CB, respectively. This work provides a universal approach for efficient and large-scale preparation of lightweight and multifunctional polymer composite foams.

A continuous, solvent-free sintering strategy was devised to systematically adjust the molecular chain entanglement density (ve) of UHMWPE by controlling chain diffusion through adjustments in heating rate and sintering temperature. Entanglement density was quantified by melt-state rheology and above-melting tensile tests, yielding values from 40 % to 100 % of the equilibrium state. DMA and DSC revealed that increasing ve delays crystallization onset, reduces overall crystallinity from 56.3 % to 41.2 %, decreases lamellar thickness from 26.9 to 25.98 nm, and lowers the melting temperature from 140.2 degrees C to 135.4 degrees C. At room temperature, higher ve correlates with reductions in tensile modulus, strength, and elongation at break, whereas at-196 degrees C (liquid-nitrogen conditions) impact toughness increases sharply from 18.8 to 27.1 kJ/m2, a 44 % improvement. Comparative tests on UHMWPE grades with molecular weights of 1.9, 2.8, and 8.2 x 103 kg/mol confirm that higher molecular weight enhances cryogenic toughness via elevated ve. Microstructure and fracture-surface analyses attribute improved low-temperature energy dissipation to reinforced interparticle welding and an internal "chain-spring" network formed by dense entanglements. This work clarifies the interplay among entanglement, crystallinity, and mechanical performance in UHMWPE and provides a scalable route to engineer polyethylene for both room and extreme-temperature applications.

Current research on polymer-based electromagnetic interference (EMI) shielding materials has predominantly focused on the design of their physical structure and diversity of fillers, while the fundamental correlation between their microstructural development and multifunctional performance remains insufficiently addressed, especially in the monolayer single filler system. This investigation systematically elucidates the critical role of molecular chain diffusion in governing both mechanical and EMI shielding properties of nascent ultrahigh molecular weight polyethylene/carbon nanotubes (UHWMPE/CNTs) composites, during their sintering process. Through precise regulation of sintering parameters such as sintering temperature and heating rate, controlled molecular chain diffusion and optimized interfacial welding were obtained, thereby the increased crystallinity and three-dimensional conductive network were achieved. Remarkably, treated under a sintering temperature of 150 degrees C with a heating rate of 0.3 degrees C/min, a tensile strength of 53.9 MPa (+31.8 %), elongation at break of 578 % (+21.2 %), and an EMI shielding effectiveness of 30.6 dB (+42.3 %) of the UHMWPE/5CNTs with a thickness of 1.5 mm were resulted, compared to its conventional high rate sintered (210 degrees C, 15 degrees C/min) counterpart. Furthermore, the CNTs, confined to the interfacial region, enhanced the electric conductive network of the UHMWPE/5CNTs, but did not significantly influence its inherent melting behavior and chain entanglement. So, such lightweight nanocomposites made through microstructure-property manipulation with a comparatively low CNTs distribution and balanced mechanical-electrical functionality has potential application in the EMI shielding protection area.

Polymer nanocomposite foams with high electromagnetic interference (EMI) shielding performance have become the research hotspot to reduce electromagnetic wave pollution. Herein, we prepared polyethylene/poly (vinylidene fluoride)/carbon nanotubes/Fe3O4(PE/PVDF/Fe3O4/CNTs) nanocomposites and nanocomposite foams by following the simple melt blending and batch foaming procedures. The co-continuous structure system of PVDF/PE was achieved by altering the matrix ratio of PVDF/PE, while reaching a maximum average EMI shielding efficiency of ca. 28 dB for the nanocomposite with PVDF/PE ratio of 5:5. Furthermore, the largest specific EMI SE of as high as 275 dB center dot cm(2)center dot g(-1) was obtained for the nanocomposite foam with PVDF/PE ratio of 9: 1, in which the EMI shielding mechanism is mainly based on absorption, leading to a significantly reduction in the secondary EM wave pollution. Therefore, the preparation of porous polymer nanocomposite foams with excellent EM wave absorption performance served as a novel strategy to reduce secondary EM wave pollution that holds great potential for applications in both military and civilian fields.

Construction of highly conductive layer on polymer foams is conducive to enhancing the electromagnetic interference (EMI) shielding performance. Herein, sandwich structures consisted of poly(butylene adipate-coterephthalate) (PBAT)/carbon fiber (CF) foam and continuous CF reinforced polypropylene prepregs were prepared. The prepregs and PBAT/CF composite film were first bonded by hot pressing, and then foamed using supercritical CO2. The morphology of fracture surfaces and peeling tests of the pressed samples demonstrated a good bonding in interfaces between prepregs and composites. Because the bonded prepregs hindered gas escape from PBAT/CF film, the cells of foams with prepregs were more uniform and denser. By adjusting the foaming temperature, pressure, and CF content, foams with cell size of 2.7-34.3 mu m, cell density of 4.4 x 107-7.3 x 1010 cells/cm3, and expansion ratio of 1.2-2.8 were achieved. Owing to the high conductivity of prepregs, sandwich structures also had an enhanced the EMI shielding performance. The EMI shielding effectiveness of the sandwich structure with a thickness of 0.7 mm and a 51 % decrease in density was 38.1 dB.

Fast development of information science and electronic technology, as well as the use of related equipment have been inducing unavoidable electromagnetic wave (EMW) pollution. High performed electromagnetic interference (EMI) shielding composites are required for weakening or resolving such problems. In this study, we aimed to prepare lightweight and porous composites with high EMI effectiveness, especially under relatively high service temperature condition. Silicon carbide (SiC) and zirconium diboride (ZrB2) were compounded with cotton fibers (CFs) to prepare ZrB2-SiC/CF compounds, cooperated with high-temperature sintering technique at 800 degrees C-1200 degrees C. Furthermore, epoxy resin dipping was applied to improve the mechanical property, combining with Fe3O4 nanoparticle' coating on their surface to enhance the EMI shielding performance. Average EMI shielding efficiency of the ZrB2-SiC/60CF@Epoxy-Fe3O4 with a thickness of 1.54 mm was as high as 58.93 dB, at a frequency range of 18-26 GHz. High dielectric loss induced by carbonated CFs, magnetic loss from Fe3O4 nanoparticles, as well as the porous structure contributed to this high EMI shielding performance. The MATLAB software was used to further exam the SEM pictures before and after sintering and helped to explain the change in composite's porosity and morphology, as well as their influence on the EMI shielding performance.

Nanofibers, as nucleating agents, can significantly alter the nucleation and growth dynamics of polymer crystallization, thereby modulating the morphology and structure of crystals to enhance mechanical performance of the materials. In this study, the effects of nanofibrillar nucleating agent 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS) content, melting temperature, and injection speed on the crystallization behavior and mechanical performance of isotactic polypropylene (iPP) were systematically investigated. The incorporation of DMDBS significantly increased the number of iPP nuclei, reduced crystal size and raised the onset crystallization temperature by approximately 11 °C. Concurrently, the tensile strength and elastic modulus of injection-molded iPP samples improved by 15% and 55%, respectively. However, a rise in the melting temperature led to a decrease in the crystallinity, tensile strength, elastic modulus, and impact strength of both neat iPP and iPP/DMDBS samples. With the increase in injection speed, the tensile strength and elastic modulus of iPP/DMDBS samples increased. During the crystallization process, DMDBS crystallizes prior to the iPP melt, forming the nanofibrillar network that effectively reduced the energy barrier for iPP crystal nucleation. Furthermore, under the influence of shear forces during processing, the presence of these nanofibrillar networks promoted the formation of oriented crystalline structures, which in turn contributed to the enhanced tensile strength and elastic modulus observed in iPP samples.

Atomic force microscopy (AFM) and optical microscopy (OM) were utilized to study the growth kinetics and morphology of the flat-on stereocomplex lamellae in poly(d-lactide)/poly(l-lactide) (PDLA/PLLA) blend ultrathin films at various crystallization temperatures (T-c) and mass ratios. As the T-c increases from 170 to 195 degrees C, the crystal morphology of PLA stereocomplex (SC-PLA) lamellae transitions from dendrites with curved main and side branches to triangular crystals without curvature, accompanied by a decrease in the early growth rate (G(e)). Similarly, increasing the mass ratio of PDLA to PLLA from 1.5:1 to 9:1 results in a decrease in G(e), while the curvature radius of the main branch (rho(b)) increase. By measuring the width (w(d)) of the depletion zone ahead of the growing lamellae, we made an intriguing observation that rho(b) correlates with w(d), through a power law relationship: rho(b) similar to w(d)(alpha) (alpha = 1-2, depending on the molecular weight). Furthermore, w(d) increases over time at higher T-c, leading to a non-linear growth of crystals (G(e) continuously decays with time), confirmed a diffusion-controlled growth mechanism. Concurrently, the thickness of stereocomplex lamellar crystals begins to expand as growth rate diminishes to approximately 40 % of G(e). This indicates that the non-equilibrium growth kinetics is the primary factor driving the changes in rho(b) and thickness of main branches of SC-PLA dendritic crystals within ultrathin films.