Molecular Chain Structure Research Articles

The polysaccharides from blackened jujube with ultrasonic assistance extraction: Optimization of extraction conditions, antioxidant activity and structural analysis

Jujube is a widely grown agricultural product. In order to avoid the waste of resources and improve the added value of the blackened jujube, the blackened jujube was processed under certain temperature and humidity conditions. At present, there are relatively few researches on polysaccharides of blackened jujube. The selection of extraction method is very important for the study and utilization of plant polysaccharides. Ultrasonic assisted extraction technology has been widely used in polysaccharide extraction for its advantages of environmental protection, economy and high extraction rate. In order to fully tap the utilization potential of polysaccharides from blackened jujube, the ultrasonic assisted extraction technology of polysaccharides from blackened jujube was optimized. Based on the optimal conditions obtained by response surface analysis, the extraction rate of polysaccharide was as high as 12.75 ± 0.05%. The IC50 values of hydroxyl radical, DPPH radical and superoxide anion were 2.604 mg/mL, 0.754 mg/mL and 8.069 mg/mL, respectively. The blackened jujube polysaccharide (BJP) was mainly composed of rhamnose (Rha), arabinose (Ara), galactose (Gal) and galacturonic acid (Gal-UA), with a molecular weight of 1.42 × 106 Da, and the surface was a dense network structure with voids. The results showed that ultrasound-assisted extraction could extract polysaccharides more economically and efficiently. In this study, the polysaccharide extracted from blackened jujube has natural antioxidant effect, which may be related to the high content of galacturonic acid in polysaccharide and the molecular chain structure of polysaccharide can be destroyed by ultrasonic wave. As a kind of natural antioxidant, blackened jujube polysaccharide has important application value in functional products in food and medicine industries.

Iminodiacetic acid enhances the mechanical and degradation properties of copolyesters by hydrogen bonding and branching

The development of biodegradable polyester materials is of great significance in alleviating the problem of plastic pollution. Poly(butylene terephthalate adipate) (PBAT) is a typical aliphatic-aromatic copolyester and has a capacity of several hundred thousand tons per year. However, the relatively low mechanical strength and high requirement for degradation environment of PBAT limit its application fields. To compensate for the deficiencies in mechanical and degradable properties of PBAT, this study reports a molecular chain structure design on the amorphous region using diethyl iminodiacetate (DEI). A series of poly(butylene adipate iminodiacetate terephthalate) (PBAIT) with a DEI content of 5–20 mol% were obtained. DEI contains secondary amine groups, which can be amidated with ester bonds to produce branched sites, and branched structures can be formed from 75 to 79 % of DEI during the copolymerization process. PBAIT-10 exhibit better tensile strength (23.87 MPa), tensile modulus (108.2 MPa) and hydrophilicity than those of PBAT. In addition, PBAIT-10 also shows very high toughness, with an elongation at break of over 1000 %. PBAITs can be degraded in enzymatic or hydrolytic environments. The degradation mechanism was analyzed by 1H NMR spectra and FTIR, and further combined with 2D-IR analysis, which reveals the rapid degradation of the BI chain segments regardless of whether or not they form branched sites. This work provides an idea to prepare copolyesters that combine good mechanical properties with degradability under mild conditions.

Ceramic Microsphere Aerogels by Curled Precursor Molecular Chain: Antishrinkage, Thermal Insulation and Multiscale Simulations.

Ceramic aerogels prepared by the route of polymer-derived ceramics (PDCs) have been of significant attention in high-temperature insulation. However, the application of ceramic aerogels was seriously confined due to the structural damage and shrinkage cracking of ceramic precursors during pyrolysis. In this investigation, precursor ceramic microsphere aerogels with outstanding antishrinkage properties were prepared by storing strain in curled molecular chains and using polysilazane (PSZ) as the precursor. Meanwhile, precursor ceramic microsphere aerogels with different curled molecular chain structures were prepared by modulating solvent interactions and cross-linked structures. Different curled molecular chain structures were formed, and the impact on the antishrinkage properties of precursor aerogels was analyzed. The shrinkage resistance, thermal insulation, and mechanical properties of the prepared aerogels were tested and compared. Furthermore, the mechanism of the impact of different curled molecular chain structures on thermal insulation and mechanical properties was investigated through multiscale simulations combined with fractal theory. The thermal and stress transfer at the interfaces of different microsphere skeleton structures and the mechanisms were investigated. An idea for solving the problem of pyrolytic shrinkage in the preparation of ceramic aerogels was provided in this investigation. In addition, insights into the influence of the microsphere skeleton structure on the thermal and mechanical properties of ceramic aerogels were provided.

Preparation of high transparency, thermal stability, flame retardant polymethyl methacrylate nanocomposite via gamma-radiation polymerization

Achieving flame retardancy and thermal stability in poly(methyl methacrylate) (PMMA) while maintaining its inherent high transparency presents a significant challenge. In this work, we successfully fabricated an exceptional composite (P-SiO2-PMMA) with high transparency, flame retardancy, and thermal stability using 60Co γ-ray irradiation-induced copolymerization of methyl methacrylate (MMA), 2-hydroxyethyl 2-methyl-2-propenoate phosphate (HEMAP), and nano-silica (SiO2). The impact of the HEMAP on the crystal, optical, thermal stability, and combustion behavior properties of P-SiO2-PMMA has been investigated. P-SiO2/PMMA forms a three-dimensional network cross-linked molecular chain structure, enhancing the thermal decomposition temperature (Tdi), maximum thermal decomposition temperature (Tmax), glass transition temperature (Tg), and reducing the coefficient of thermal expansion (CTE). HEMAP and SiO2 significantly enhance the flame retardancy of the material. The limiting oxygen index (LOI) value of transparent flame-retardant 20-P-SiO2/PMMA composite material increased from 17.5% for PMMA to 23.2%, with a 47.3% decrease in peak heat release rate (PHRR). The flame retardant mechanism was also investigated. This study offers a novel approach for the industrial application of high transparency, thermal stability, and halogen-free flame-retardant PMMA composite.

Characteristic of fluoroether gum via non-linear rheological approaches

Abstract Large amplitude oscillatory shear (LAOS) tests were conducted on four types of fluoroether elastomer gum, namely VPL-85540, VPL-75545, VPL-65455, and VPL-55540 in order to study their molecular weight, chain structure, and branching degree from the perspective of rubber rheology. For the setting of shear rate in varied LAOS measurements, frequency and angular velocity controlling modes were attempted and compared. Non-linear rheological parameters showed that VPL-65455 possessed significant polymeric branching characteristics. VPL-55540 possessed the lowest molecular weight, and VPL-75545 was detected with higher long-pendant monomer content in its polymer chain. Rheological properties concluded from the analysis of two shear rate controlling modes of LAOS tests exhibited great consistency, which confirmed the reliability of LAOS tests in the characterization of fluoroether gum.

Synthesized Crosslinking Suspension Stabilizer for Spacer Fluid in High-Temperature Conditions: Synthesis, Behavior, and Mechanism Research

Summary High-temperature stability of spacer fluid is a vital prerequisite to ensure the safety of cementing operations in deep or ultradeep wells. Faced with this problem, the thermal stability of the suspension agent in the spacer fluid at high temperatures is improved from the aspects of polymerization monomer and molecular chain. A terpolymer SAD was synthesized by free radical polymerization of sodium styrene sulfonate (SSS), acrylamide (AM), and N, N’-diethylacrylamide (DEAA) in aqueous solution. The name of the terpolymer, SAD, is the initial letter composition of the three polymerization monomers. Polyethyleneimine (PEI) can improve the molecular chain structure of SAD by transamidation reaction with the amide group in SAD, so a high temperature suspension agent PSAD (polyethyleneimine + SAD) was obtained by compounding PEI with SAD. The structure and properties of PSAD were characterized by Fourier infrared spectroscopy, hydrogen nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, scanning electron microscopy (SEM), and viscosity test. In addition, the comprehensive properties of the spacer fluid under the action of PSAD are evaluated. The results showed that the crosslinking degree of PSAD gradually increased with the increase in temperature. After aging at 200°C, the decomposition temperature of PSAD was 305°C, which show terrific thermal stability. At the same time, the spacer fluid prepared by PSAD not only has excellent rheological properties in the range of 90 ~ 200°C but also keeps the density difference between the upper and lower parts of the slurry less than 0.02 g/cm3 and the filtration loss of the slurry less than 50 mL.

Modulation of Mechanical Properties of Silica-Filled Silicone Rubber by Cross-Linked Network Structure.

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory-Rehner model and Mooney-Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber.

Synthesis and properties of bio-based semi-aromatic heat-resistant copolymer polyamide 5T-co-6T

ABSTRACT Herein, poly(pentanediamine terephthalamide) (PA5T) homopolymer was synthesized via a salt-forming reaction+solid state polycondensation method using bio-based 1,5-pentanediamine and terephthalic acid as the primary raw materials. To address the issue of its narrower processing window, poly(hexamethylene terephthalamide)(PA6T), which also cannot be melt processed due to the processing window is negative, was introduced into its molecular chain to synthesize poly (pentanediamine/hexanediamine terephthaloyl) (PA5T-co-6T) copolymers. The structures were investigated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance carbon spectroscopy (13C-NMR). Furthermore, the melting temperature, crystallization temperature, thermal stability, and crystal growth mode of the polymer were tested and analyzed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and wide-angle x-ray diffraction (WAXD), respectively. The results demonstrate that the crystal growth mode gradually changes from three-dimensional spherical growth to two-dimensional disk-like or three-dimensional spherical growth with the increase of 6T chain segment content. Simultaneously, the crystallization temperature, melting temperature, and crystallization rate of the polymer all showed a trend of decreasing first and then increasing, which was due to the combined effects of the increase in the content of 6T chain segments on the molecular-chain structure and crystal structure of the polymer. Bio-based PA5T-co-6T has excellent heat resistance and a wider processing window than PA5T and PA6T, which possesses great application prospects in the fields of automotive, electronic appliances, and LED optics.

One-Dimensional Van Der Waals V2Se9 As a Conversion-Type Anode Material for Advanced Li Rechargeable Batteries

Volume expansion of active materials during lithium storage is one of the main issues in Li-ion batteries (LIBs) that should be addressed. In particular, large volume changes and particle cracking are problematic for electrode materials based on conversion reaction, which are considered attractive anode materials with high energy densities. In this study, a one-dimensional van der Waals (1D vdW) material, V2Se9, is proposed as a conversion-type anode material for LIBs. The V2Se9 electrode material has a 1D chain molecular structure with vdW interactions between chains to form a bulk crystal structure. The spaces between the 1D chains act as structural buffers and provide short Li+ diffusion paths that can improve the electrochemical performance of the electrode materials. The V2Se9 electrode exhibits a high reversible capacity of 563.3 mAh g-1 at 100 mA g-1 and a high rate capability of 109.1 mAh g-1 at 3200 mA g-1. The capacity retention of V2Se9 electrodes is 83.72 % after 100 cycles. Synchrotron X-ray diffraction and X-ray absorption spectroscopy reveal the formation of Li2Se and V metal, indicating that Li ion storage occurs via the conversion reaction. The structural stability of V2Se9 is demonstrated using SEM measurements of the discharged and charged V2Se9 electrodes during cycling. These results demonstrate the reaction mechanism of V2Se9 and highlight the potential of 1D vdW materials as high-performance anode materials in LIBs.

A green extraction method for agar with improved thermal stability and water holding capacity

The conventional agar extraction method has drawbacks such as high energy consumption, low yield, poor quality, and possible residual harmful factors, which greatly limit its application in high-end fields such as biomedicine and high-end materials. This work explored a new freezing-thawing-high-temperature coupling technique for agar extraction. It increased the yield and the strength of agar by 10.6 % and 13.7 %, respectively, as compared to direct high-temperature extraction of agar (HA). The greater molecular weight and lower sulfate content of agar obtained from freeze-thaw cycles combined with high temperature extraction (FA) may be attributed to the desulfurization effect caused by freeze-thaw cycles and the preservation of the molecular chain structure. The reduction in sulfate content decreases the steric hindrance resistance of the polysaccharide chains, enhances their interactions, and promotes the regularity and density of the agar structure, while also improving its water retention and thermal stability. In conclusion, this research can offer a theoretical basis and guidance for the eco-friendly extraction of agar with improved agar characteristics and expended its applications.

Biodegradable and biocompatible nonisocyanate polyurethanes synthesized from bio-derived precursors

Despite the enormous use of polyurethanes (PUs) in multiple aspects of modern lifestyle, the industrial scale manufacturing of PUs uses toxic chemicals like isocyanates, phosgene till today. In addition, the non-biodegradability and non-biocompatibility of PUs and their debris are serious cause of concerns for the environment. To deal with these challenges, in the current work, a new approach is reported in which bio-derived non-isocyanate polyurethanes were synthesized by exploiting viable amino acid-based diamines and biscyclocarbonates from sebacoyl chloride and diglycerol derivatives in a readily doable process. The newly designed polyhydroxyurethanes (PHUs) exhibited remarkable biodegradability and biocompatibility (cell viability) in comparison with commercial diamine based PHUs. A series of PHUs were synthesized in bulk and solvent free green synthetic route by polycondensing library of amino acids (such as glycine, alanine, valine, and isoleucine etc.) based diamines consisting of varying alkyl chain lengths and biscyclocarbonates like sebacic biscyclocarbonate and diglycerol biscyclocarbonate etc. All the synthesized PHUs were thoroughly characterised by IR, NMR and HRMS spectroscopic techniques. The impact of chain length and molecular structure of the synthesized PHUs were also evaluated using DSC, TGA, SEC, water contact angle measurements and hydrolytic degradation studies. The molar masses of the PHUs obtained from the SEC analysis are in the range of ∼17,000–24,000 Da. The current study demonstrated that amino acids is one of the major degradation products and are biocompatible in in-vitro conditions. The PHUs and their degradable products showed excellent cell viability when studied in HEK293T cells that were carried out using microgram to milligram concentration of PHUs. The outcome of this work in comparison to conventional PHUs and polyurethanes clearly demonstrated good biocompatibility and hence drawing attention to potential applications in bio-adhesives, bio-implants, drug delivery, and green coatings etc. in the near future.

Preparation and Properties of Multiple Dynamic Crosslinked Poly(siloxane‐urethane)

AbstractSelf‐healing poly(siloxane‐urethane) materials have garnered significant interest among researchers, owing to their superior resistance to high and low temperatures, solvents, corrosion, and biocompatibility. Nevertheless, most existing self‐healing poly(siloxane‐urethane) materials face challenges, including limited repair conditions and the challenge of balancing mechanical properties with repair efficiency. In this research, we introduced hydrogen bonds, metal coordination bonds, π–π bonds, and reversible ring structures into the poly(siloxane‐urethane) system through molecular chain structure design, successfully developing a multi‐dynamic cross‐linked poly(siloxane‐urethane) (PU‐Si), a development rarely reported in prior studies. This study examines the impact of varying amounts of hydroxyl‐terminated polydimethylsiloxane (PDMS‐OH) on the properties of PU‐Si. The results indicate that PU‐Si, regardless of the amount of PDMS‐OH added, can self‐healing under conditions of heating at 60 °C, and exposure to ultraviolet and infrared radiation. Specifically, when the PDMS‐OH addition reaches 1.0 g, the material exhibits superior mechanical properties and self‐healing efficiency, achieving a mechanical strength of 9.68 MPa and a self‐healing efficiency of 86.6 %. This material shows significant application potential in areas such as electronic skins, flexible sensors, and brain‐computer interfaces.

Bio-based epoxy resin demonstrating high breakdown strength and low dielectric loss via intrinsic molecular charge traps construction

In the ultra-high voltage, ultra-high capacity and high frequency energy systems, epoxy-based dielectric materials demonstrating high breakdown strength and low dielectric loss are urgently needed. This work reports a strategy to modulate the charge trap depth in bio-based epoxy dielectric materials by tailoring the local molecular chain structures, ultimately leading to the significant suppression of high-field conductivity and dielectric loss. With the introduction of octa (dimethylsiloxy)octasilsiloxane (POSS) as the intrinsic molecular charge traps, our synthesized epoxy dielectric material exhibits a high breakdown strength of Eb-DC = 81.5 kV/mm, 37 % higher than the traditional bisphenol A epoxy resin (DGEBA), and low dielectric loss of tan δ = 0.0022, 45 % lower than that DGEBA. Furthermore, simulation results give the structure-property relationships, guiding the molecular design. Specifically, the dielectric properties are positively correlated with the LUMO energy difference and charge separation index of the polymer molecular chains. This work provides a promising pathway to enhance the dielectric properties of polymers by building intrinsic molecular charge traps, which is prospective for practical electronics and electrical power systems.

Strong and tough semi-crystalline poly(aryl ether nitrile) with low coefficient of thermal expansion

The crystallization of poly (aryl ether nitrile) (PEN) has an essential impact on improving heat resistance, mechanical properties, chemical resistance, and dielectric properties. However, during the synthesis process, high crystallinity PEN is prone to precipitate out, which makes it difficult to carry out the synthesis reaction, which poses a significant challenge to synthesizing high crystallinity and high molecular weight PEN. In this work, hydroquinone (HQ) as the main phenolic monomer and 4,4′-biphenol (BP) as the second phenolic monomer were used to solve the technical difficulties in synthesis by copolymerization. The crystalline PEN with high molecular weight and significant crystallinity was obtained by regulating the molar ratio of BP to HQ. The effects of isothermal heat treatment on its crystalline, mechanical, and thermal properties were investigated. The influence laws of molecular chain structure and heat treatment process on the properties of PEN films were revealed. Among them, when the isothermal treatment temperature was 270 °C and the HQ: BP was 85:15, the mechanical strength reached 130 MPa, and the elongation at break could be up to an astonishing 50 %. Besides, the CTE value from 50 °C–150 °C is 40.84 ppm/°C, which is lower than most thermoplastics. Therefore, PEN with the HQ to BP molar ratio of 85:15 is suitable for large-scale production, providing new crystalline plastic specifications for high-performance special engineering plastics. A crystal bridge-tie chain model is summarized by the properties of HQ/BP-PEN films under different crystallization conditions, which provides an idea for preparing stiff and tough films.

Enhancing the foamability of poly(L-lactide-co-ε-caprolactone) through formation of stereocomplex crystal by introducing of poly(D-lactic acid)

The bio-elastomer poly (L-lactide-co-ε-caprolactone) (PLCL) with linear random molecular chain structure exhibits low viscosity and melt strength, resulting in poor foamability, cell merging, or collapse during the foaming process. Consequently, PLCL foams have large cell sizes and low cell densities, limiting their use as biodegradable elastomeric foams. To enhance the foamability of PLCL, poly (D-lactic acid) (PDLA) was incorporated into the PLCL matrix. Stereocomplex crystals (Sc-crystals) formed between the L-LA segments of PLCL and the molecular segments of PDLA. The effects of varying PDLA content on the basic properties and foaming behavior of the blends were investigated. Results indicate that optimal Sc-crystal formation occurs in the PLCL/PDLA-10 blend. The presence of Sc-crystals enhances melt strength and facilitates cell nucleation, reducing cell size from 351.2 to 11.8 μm and increasing cell density from 1.4 × 104 to 1.7 × 108 cells/cm³. Consequently, the mechanical properties of the foam are significantly improved. The Sc-crystal formation between PLCL and PDLA provides an effective method to enhance the processability of linear chain copolymers containing L-lactide.

Combined experiments and molecular simulations for understanding the thermo-responsive behavior and gelation of methylated glucans with different glycosidic linkages

HypothesisElucidation of the micro-mechanisms of sol–gel transition of gelling glucans with different glycosidic linkages is crucial for understanding their structure–property relationship and for various applications. Glucans with distinct molecular chain structures exhibit unique gelation behaviors. The disparate gelation phenomena observed in two methylated glucans, methylated (1,3)-β-d-glucan of curdlan (MECD) and methylated (1,4)-β-d-glucan of cellulose (MC), notwithstanding their equivalent degrees of substitution, are intricately linked to their unique molecular architectures and interactions between glucan and water. ExperimentsDensity functional theory and molecular dynamics simulations focused on the electronic property distinctions between MECD and MC, alongside conformational variations during thermal gelation. Inline attenuated total reflection Fourier transform infrared spectroscopy tracked secondary structure alterations in MECD and MC. To corroborate the simulation results, additional analyses including circular dichroism, rheology, and micro-differential scanning calorimetry were performed. FindingsDespite having similar thermally induced gel networks, MECD and MC display distinct physical gelation patterns and molecular-level conformational changes during gelation. The network of MC gel was formed via a “coil-to-ring” transition, followed by ring stacking. In contrast, the MECD gel comprised compact irregular helices accompanied by notable volume shrinkage. These variations in gelation behavior are ascribed to heightened hydrophobic interactions and diminished hydrogen bonding in both systems upon heating, resulting in gelation. These findings provide valuable insights into the microstructural changes during gelation and the thermo-gelation mechanisms of structurally similar polysaccharides.

Seawater‐degradable poly(ethylene adipate‐co‐terephthalate) copolyester: Synthesis, properties, and degradation behavior

AbstractThe application and promotion of biodegradable plastics are hindered by the imbalance between their mechanical and degradation performance imbalance, as well as high costs. Herein, a series of poly(ethylene adipate‐co‐terephthalate) (PEAT) copolyesters with excellent mechanical and degradation properties are synthesized by one‐step melt polycondensation. The influence of the proportion of aliphatic groups in the molecular chain on the structure and properties, especially the degradation performance, of the copolyesters was studied. The molecular chain flexibility and degradability of PEAT increases with increasing of adipic acid content and decreasing of ET fragment length (LET). The comprehensive mechanical properties of PEAT60 can be comparable to traditional packaging material poly(butylene adipateco‐terephthalate) (PBAT). The degradation performance of PEAT can be adjusted the molecular chain structure. PEAT with LET < 3 exhibit degradation performance, and PEAT with LET < 2.2 exhibit significant degradation acceleration. The excellent mechanical and degradable properties of PEAT copolyester make it expected to be used in degradable packaging and other fields to help solve plastic pollution, while its lower cost will aid in the promotion of degradable materials.

Novel bio-based polyurethane elastomers for adjustable room-temperature damping property

The distinctive viscoelastic behavior of elastomeres can be exploited for reducing vibrations and noise. However, the utility of conventional rubber-based elastomers is limited by low glass transition temperature (Tg) and narrow adjustable damping range, which constrain the room-temperature damping property. Moreover, the majority of rubber-based elastomers are sourced from unsustainable petroleum-based resources. Therefore, designing bio-based materials with room-temperature high-damping property to replace conventional rubber-based elastomers is crucial. Herein, a novel bio-based polyurethane (bio-PU) elastomer with an adjustable damping-temperature range and room-temperature high-damping property is successfully synthesized from bio-based poly (trimethylene ether) glycol. The effects of molecular chain structure on the thermal properties, mechanical properties, and adjustable damping-temperature range of the bio-PU elastomers, along with the mechanisms underlying these effects, are elucidated in detail. As the content of hard segment increasing, the Tg of bio-PU elastomers significantly increases from −13.0 to 29.9 °C, effectively encompassing the damping temperature range within the room-temperature working range. This promising strategy for formulating bio-based elastomers with adjustable damping-temperature range can advance the sustainable growth of PU industry and broaden the scope of PU damping applications.

The study of the structure and performance of polyoxymethylene modified by nucleating agent L

With the expanding application areas of polyoxymethylene (POM), the challenges in its crystal modification are becoming greater. Conventional nucleating agents have issues with compatibility with POM. So we used a nucleating agent L with a similar molecular chain structure to POM through melt blending to modify POM. Using instruments to characterize and test the samples, and studying the effect of nucleating agent L on the structure and properties of POM. The results showed that after adding a small amount of nucleating agent. The crystal size was reduced. The number and size of micro-pores at the cross-section were significantly reduced. The crystallization performance of POM were improved. This provides a new direction for the future development of POM-specific nucleating agents and the direction of efficient nucleating.

Enhancing mechanical integrity of vat photopolymerization 3D printed hydroxyapatite scaffolds through overcoming peeling defects

In ceramic vat photopolymerization (VPP) fabrication, directly peeling originally designed scaffolds from the platform is efficient but often introduces defects, compromising the mechanical integrity of hydroxyapatite (HAp) scaffold. The peeling process involves the resistance of the HAp green scaffolds to peeling forces, which is influenced by its modulus and toughness. In this study, the peeling behavior of cubic-pore HAp (CP-HAp) green scaffolds with varying levels of modulus and toughness was investigated. The characterization results show that the HDDA CP-HAp scaffolds with relatively high levels of modulus and toughness could effectively resist the peeling forces and inhibit the occurrence of peeling defects. Stress concentration and inadequate toughness in the HEMA CP-HAp scaffolds lead to the formation of peeling defects. The CTFA and PHEA CP-HAp scaffolds with low modulus exhibit both peeling cracks and numerous pores. The cracks result from stress concentration, while the pores are caused by the coiled and loose molecular chain structure occupying space. Understanding the mechanism of peeling defect initiation in HAp porous scaffolds contributes to improving resistance to such defects and efficiently fabricating high-performance ceramic scaffolds using VPP.