The Interface and Interphase in Polymer Matrix Composites: Effect on Mechanical Properties and Methods for Identification

Novel insights into the mechanism of dynamic changes in microstructure and physicochemical properties of corn straw pretreated by ball milling and feasibility analysis of anaerobic digestion

In this study, the effects of Ball milling (BM) pretreatment (0-240 min) on the microstructure, physicochemical properties and subsequent methanogenesis performance of corn straw (CS) were explored, and the feasibility analysis was carried out. The results showed that BM pretreatment destroyed the dense structure of the CS, and the particle size was significantly reduced (D50: 13.85 μm), transforming it into a cell-scale granular form. The number of mesopores increased, the pore volume (PV) (0.032 cm3/g) and specific surface area (SSA) (4.738 m2/g) considerably increased, and the water-absorbent property was improved. The crystalline order of cellulose was disrupted and the crystallinity (CrI) (8.61 %) and crystal size (CrS) (3.37) were remarkably reduced. The cross-links between lignocelluloses were broken, and the relative content and functional groups did not alter obviously. The bulk density (BD), repose angle (RA) and slip angle (SA) dramatically increased. As a result, CS was more readily accessible, attached and utilized by microorganisms and enzymes, causing the hydrolysis and acidification of AD to be greatly facilitated. Compared with the untreated group, the cumulative methane production (CMP) increased by 35.83 %-101.97 %, and the lag phase time (λ) was shortened by 33.04 %-71.17 %. The results of redundancy analysis, Pearson analysis and Mantel test showed that BM pretreatment affects the process of AD by changing the physicochemical factors of CS. The normalization analysis showed that particle size (D90) and BD can be used as direct indicators to evaluate the performance of AD and predict the threshold of biodegradation of CS. Energy analysis and energy conversion assessment showed that BM is a green and efficient AD pretreatment strategy. This result provides a theoretical basis for the industrial application of BM pretreatment towards more energy-efficient and sustainable development.

Polymer-Assisted Graphite Exfoliation: Advancing Nanostructure Preparation and Multifunctional Composites

Exfoliated graphite (ExG) embedded in a polymeric matrix represents an accessible, cost-effective, and sustainable method for generating nanosized graphite-based polymer composites with multifunctional properties. This review article analyzes diverse methods currently used to exfoliate graphite into graphite nanoplatelets, few-layer graphene, and polymer-assisted graphene. It also explores engineered methods for small-scale pilot production of polymer nanocomposites. It highlights the chemistry involved during the graphite intercalation and exfoliation process, particularly emphasizing the interfacial interactions related to steric repulsion forces, van der Waals forces, hydrogen bonds, π-π stacking, and covalent bonds. These interactions promote the dispersion and stabilization of the graphite derivative structures in polymeric matrices. Finally, it compares the enhanced properties of nanocomposites, such as increased thermal and electrical conductivity and electromagnetic interference (EMI) shielding applications, with those of neat polymer materials.

Interfacial interactions between spider silk protein and cellulose studied by molecular dynamics simulation

CONTEXT

Due to their excellent biocompatibility and degradability, cellulose/spider silk protein composites hold a significant value in biomedical applications such as tissue engineering, drug delivery, and medical dressings. The interfacial interactions between cellulose and spider silk protein affect the properties of the composite. Therefore, it is important to understand the interfacial interactions between spider silk protein and cellulose to guide the design and optimization of composites. The study of the adsorption of protein on specific surfaces of cellulose crystal can be very complex using experimental methods. Molecular dynamics simulations allow the exploration of various physical and chemical changes at the atomic level of the material and enable an atomic description of the interactions between cellulose crystal planes and spider silk protein. In this study, molecular dynamics simulations were employed to investigate the interfacial interactions between spider silk protein (NTD) and cellulose surfaces. Findings of RMSD, RMSF, and secondary structure showed that the structure of NTD proteins remained unchanged during the adsorption process. Cellulose contact numbers and hydrogen bonding trends on different crystalline surfaces suggest that van der Waals forces and hydrogen bonding interactions drive the binding of proteins to cellulose. These findings reveal the interaction between cellulose and protein at the molecular level and provide theoretical guidance for the design and synthesis of cellulose/spider silk protein composites.

METHODS

MD simulations were all performed using the GROMACS-5.1 software package and run with CHARMM36 carbohydrate force field. Molecular dynamics simulations were performed for 500 ns for the simulated system.

Probabilistic Analysis of Composite Materials with Hyper-Elastic Components

This work is a comprehensive literature overview in the area of probabilistic methods related to composite materials with components exhibiting hyper-elastic constitutive behavior. A practical area of potential applications is seen to be rubber, rubber-like, or even rubber-based heterogeneous media, which have a huge importance in civil, mechanical, environmental, and aerospace engineering. The overview proposed and related discussion starts with some general introductory remarks and a general overview of the theories and methods of hyper-elastic material with a special emphasis on the recent progress. Further, a detailed review of the current trends in probabilistic methods is provided, which is followed by a literature perspective on the theoretical, experimental, and numerical treatments of interphase composites. The most important part of this work is a discussion of the up-to-date methods and works that used the homogenization method and effective medium analysis. There is a specific focus on random composites with and without any interface defects, but the approaches recalled here may also serve as well in sensitivity analysis and optimization studies. This discussion may be especially helpful in all engineering analyses and models related to the reliability of elastomers, whose applicability range, which includes energy absorbers, automotive details, sportswear, and the elements of water supply networks, is still increasing, as well as areas where a stochastic response is the basis of some limit functions that are fundamental for such composites in structural health monitoring.

Characterization and antimicrobial activity of spice extract-loaded algal microcomposites based on the microemulsion technique

In recent years, with the increase in knowledge and awareness, people's efforts to return to nature have increased in the field of medical science and cosmetics industry. Spices, sumac and coriander, grown and frequently used in Turkey, have different bioactive effects. Microalgae are preferred in the treatment of skin problems. The aim of this study was to synthesize algae microcomposites that were effective against bacterial infections, prepared based on microemulsion technique and loaded with spice extract. Microemulsion formulations were prepared by the titration method. Aqueous and ethanolic extractions of sumac/coriander were carried out using the ultrasonic-assisted extraction method. Twenty-four different algal microcomposites loaded with extracts were synthesized. The disk diffusion method was used to determine the antimicrobial activity. The DPPH free radical scavenging activities, the total phenolic content (TPSC), and the characteristics (FT-IR) of the microcomposites were investigated. In addition, the chemical contents of extracts were determined by the GC-MS method. Aqueous extracts of both sumac and coriander were highly effective against Escherichia coli (ES DII). The highest antimicrobial activity against Staphylococcus aureus (F6 III) was obtained with M9 (microcomposite containing ethanolic extract of sumac) and M15 (microcomposite containing aqueous extract of coriander). The highest TPSC value (6.025 mg GAE/gr) was detected in the aqueous extract of coriander. The DPPH radical scavenging activities of coriander extracts were lower than those of sumac extracts. It has been determined that the spices contain organic (propanoic, butanoic, malic and benzoic) acids and fatty (palmitic, oleic and myristic) acids. According to the results of FT-IR spectroscopy, microcomposites prepared with sumac and coriander extracts were successfully synthesized. The synthesized algae-based microcomposites have properties that could be in the green-labeled bio-based category.

Efficient saccharification of wheat straw pretreated by solid particle-assisted ball milling with waste washing liquor recycling

Wheat straw was pretreated using ball milling (BM) promoted by solid particles (NaOH, NaCl, citric acid). NaOH showed the best synergistic interaction effect, due to the breakage of β-1,4-glycosidic bonds among cellulose molecules by the alkali solid particles induced by BM. NaOH-BM pretreatment decreased the straw crystallinity from 46% to 21.4% and its average particle size from 398.3 to 50.6 μm in 1 h. After 4 h milling, the reducing-end concentration of cellulose increased by 3.8 times from 12.5 to 60.2 μM, with glucose yield increased by 2.1 times from 26.6% to 82.4% for 72 h enzymatic hydrolysis at cellulase loading of 15 FPU/g dry substrate. The pretreatment washing liquor was recycled for the re-treatment of partially pretreated biomass at 121 °C for 30 min, resulting in 99.4% glucose yield by enzymatic hydrolysis. BM assisted with alkali particles was an effective approach for improving biomass enzymatic saccharification.

Effect of Nanoparticles Surface Bonding and Aspect Ratio on Mechanical Properties of Highly Cross-Linked Epoxy Nanocomposites: Mesoscopic Simulations

The paper aims to study the mechanical properties of epoxy resin filled with clay nanoparticles (NPs), depending on their shapes and content on the surface of a modifying agent capable of forming covalent bonds with a polymer. The cylindrical clay nanoparticles with equal volume and different aspects ratios (disks, barrel, and stick) are addressed. The NPs' bonding ratio with the polymer (RGC) is determined by the fraction of reactive groups and conversion time and varies from RGC = 0 (non-bonded nanoparticles) to RGC = 0.65 (more than half of the surface groups are linked with the polymer matrix). The performed simulations show the so-called load-bearing chains (LBCs) of chemically cross-linked monomers and modified nanoparticles to determine the mechanical properties of the simulated composites. The introduction of nanoparticles leads to the breaking of such chains, and the chemical cross-linking of NPs with the polymer matrix restores the LBCs and strengthens the composite. At small values of RGC, the largest value of the elastic modulus is found for systems filled with nanoparticles having the smallest surface area, and at high values of RGC, on the contrary, the systems containing disk-shaped particles with the largest surface area have a larger elastic modulus than the others. All calculations are performed within the framework of a mesoscopic model based on accurate mapping of the atomistic structures of the polymer matrix and nanoparticles into coarse-grained representations, which, if necessary, allow reverse data mapping and quantitative assessment of the state of the filled epoxy resin. On the other hand, the obtained data can be used to design the functional materials with specified mechanical properties based on other practically significant polymer matrices and nanofillers.

One Surface Treatment, Multiple Possibilities: Broadening the Use-Potential of Para-Aramid Fibers with Mechanical Adhesion

Aramid fibers are high-strength and high-modulus technical fibers used in protective clothing, such as bulletproof vests and helmets, as well as in industrial applications, such as tires and brake pads. However, their full potential is not currently utilized due to adhesion problems to matrix materials. In this paper, we study how the introduction of mechanical adhesion between aramid fibers and matrix material the affects adhesion properties of the fiber in both thermoplastic and thermoset matrix. A microwave-induced surface modification method is used to create nanostructures to the fiber surface and a high throughput microbond method is used to determine changes in interfacial shear strength with an epoxy (EP) and a polypropylene (PP) matrix. Additionally, Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy were used to evaluate the surface morphology of the fibers and differences in failure mechanism at the fiber-matrix interface. We were able to increase interfacial shear strength (IFSS) by 82 and 358%, in EP and PP matrix, respectively, due to increased surface roughness and mechanical adhesion. Also, aging studies were conducted to confirm that no changes in the adhesion properties would occur over time.

Elucidation of Mechanical, Physical, Chemical and Thermal Properties of Microbial Composite Films by Integrating Sodium Alginate with Bacillus subtilis sp

Materials are the foundation in human development for improving human standards of life. This research aimed to develop microbial composite films by integrating sodium alginate with Bacillus subtilis. Sodium alginate film was fabricated as control. The microbial composite films were fabricated by integrating 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 g of Bacillus subtilis into the sodium alginate. Evaluations were performed on the mechanical, physical, chemical and thermal properties of the films. It was found that films reinforced with Bacillus subtilis significantly improved all the mentioned properties. Results show that 0.5 g microbial composite films had the highest tensile strength, breaking strain and toughness, which were 0.858 MPa, 87.406% and 0.045 MJ/m³, respectively. The thickness of the film was 1.057 mm. White light opacity, black light opacity and brightness values were 13.65%, 40.55% and 8.19%, respectively. It also had the highest conductivity, which was 37 mV, while its water absorption ability was 300.93%. Furthermore, it had a higher melting point of 218.94 °C and higher decomposition temperature of 252.69 °C. SEM also showed that it had filled cross-sectional structure and smoother surface compared to the sodium alginate film. Additionally, FTIR showed that 0.5 g microbial composite films possessed more functional groups at 800 and 662 cm⁻¹ wavenumbers that referred to C–C, C–OH, C–H ring and side group vibrations and C–OH out-of-plane bending, respectively, which contributed to the stronger bonds in the microbial composite film. Initial conclusions depict the potential of Bacillus subtilis to be used as reinforcing material in the development of microbial composite films, which also have the prospect to be used in electronic applications. This is due to the conductivity of the films increasing as Bacillus subtilis cell mass increases.

Synergic Effect of TiO2 Filler on the Mechanical Properties of Polymer Nanocomposites

Nanocomposites with polymer matrix offer excellent opportunities to explore new functionalities beyond those of conventional materials. TiO₂, as a reinforcement agent in polymeric nanocomposites, is a viable strategy that significantly enhanced their mechanical properties. The size of the filler plays an essential role in determining the mechanical properties of the nanocomposite. A defining feature of polymer nanocomposites is that the small size of the fillers leads to an increase in the interfacial area compared to traditional composites. The interfacial area generates a significant volume fraction of interfacial polymer, with properties different from the bulk polymer even at low loadings of the nanofiller. This review aims to provide specific guidelines on the correlations between the structures of TiO₂ nanocomposites with polymeric matrix and their mechanical properties. The correlations will be established and explained based on interfaces realized between the polymer matrix and inorganic filler. The paper focuses on the influence of the composition parameters (type of polymeric matrix, TiO₂ filler with surface modified/unmodified, additives) and technological parameters (processing methods, temperature, time, pressure) on the mechanical strength of TiO₂ nanocomposites with the polymeric matrix.

Experimental evaluation of bamboo fiber/particulate coconut shell hybrid PVC composite

Bamboo fibers (BF) treated in 1.3 Molar NaOH and particulate coconut shell (PCS) sieved to − 45 µm were incorporated into polyvinyl chloride (PVC) matrix towards improving the properties of PVC composite for ceiling boards and insulating pipes which sags and degrade with time needing improvement in properties. The process was carried out via compression moulding applying 0.2 kPa pressure and carried out at a temperature of 170 °C. Composites developed were grouped according to their composition. Groups A, B, C, and D were infused with 2, 4, 6 and 8 wt% PCS at constant amount, respectively. Each group was intermixed with a varying proportions of BF (0–30 wt% at 5% interval). Tests carried out on the samples produced revealed that the yield strength, modulus of elasticity, flexural strength, modulus of rupture were enhanced with increasing BF proportion from 0 to 30 wt% BF at 2 wt% constant PCS input. Thermal and electrical properties trended downward as the fiber content reduced even as the hardness was enhanced with PCS/BF intermix which was also reflected in the wear loss index. Impact strength was highest on the infix of 4 wt% PCS and 15 wt% BF. Compressive strength was better boasted with increasing fiber and PCS amount but 8 wt% PCS amounted to depreciation in trend. It was generally observed that PCS performed optimally at 2 wt% incorporation while beyond that resulted in lowering of strength. Blending of the two variable inputs; 0–30 wt% BF and 2 wt% PCS presented better enhancement in properties.

Durability of Externally Bonded Fiber-Reinforced Polymer Composites in Concrete Structures: A Critical Review

Externally bonded fiber-reinforced polymer composites have been in use in civil infrastructure for decades, but their long-term performance is still difficult to predict due to many knowledge gaps in the understanding of degradation mechanisms. This paper summarizes critical durability issues associated with the application of fiber-reinforced polymer (FRP) composites for rehabilitation of concrete structures. A variety of factors that affect the longevity of FRP composites are discussed: installation, quality control, material selection, and environmental conditions. Critical review of design approaches currently used in various international design guidelines is presented to identify potential opportunities for refinement of design guidance with respect to durability. Interdisciplinary approaches that combine materials science and structural engineering are recognized as having potential to develop composites with improved durability.

A Life Cycle Engineering Perspective on Biocomposites as a Solution for a Sustainable Recovery

Composite materials, such as carbon fibre reinforced epoxies, provide more efficient structures than conventional materials through light-weighting, but the associated high energy demand during production can be extremely detrimental to the environment. Biocomposites are an emerging material class with the potential to reduce a product’s through-life environmental impact relative to wholly synthetic composites. As with most materials, there are challenges and opportunities with the adoption of biocomposites at the each stage of the life cycle. Life Cycle Engineering is a readily available tool enabling the qualification of a product’s performance, and environmental and financial impact, which can be incorporated in the conceptual development phase. Designers and engineers are beginning to actively include the environment in their workflow, allowing them to play a significant role in future sustainability strategies. This review will introduce Life Cycle Engineering and outline how the concept can offer support in the Design for the Environment, followed by a discussion of the advantages and disadvantages of biocomposites throughout their life cycle.

A Review of the Polymer for Cryogenic Application: Methods, Mechanisms and Perspectives

Recently, the application of polymer-based composites at cryogenic conditions has become a hot topic, especially in aerospace fields. At cryogenic temperature, the polymer becomes more brittle, and the adverse effect of thermal stress induced by temperature is more remarkable. In this paper, the research development of thermoset and thermoplastic polymers for cryogenic applications are all reviewed. This review considers the literature concerning: (a) the cryogenic performance of modified thermoset polymers and the improving mechanisms of the reported modification methods; (b) the cryogenic application potential of some commercial thermoplastic polymers and the cryogenic performance of modified thermoplastic polymers; (c) the recent advance in the use of polymer for special cryogenic environment-liquid oxygen. This paper provides a comprehensive overview of the research development of the polymer for cryogenic application. Moreover, future research directions have been proposed to facilitate its practical applications in aerospace.

Development in Additive Methods in Aramid Fiber Surface Modification to Increase Fiber-Matrix Adhesion: A Review

This review article highlights and summarizes the recent developments in the field of surface modification methods for aramid fibers. Special focus is on methods that create a multifunctional fiber surface by incorporating nanostructures and enabling mechanical interlocking. To give a complete picture of adhesion promotion with aramids, the specific questions related to the challenges in aramid-matrix bonding are also shortly presented. The main discussion of the surface modification approaches is divided into sections according to how material is added to the fiber surface; (1) coating, (2) grafting and (3) growing. To provide a comprehensive view of the most recent developments in the field, other methods with similar outcomes, are also shortly reviewed. To conclude, future trends and insights are discussed.

Stimuli-Responsive Nanodiamond-Polyelectrolyte Composite Films

Nanodiamonds (NDs) can considerably improve the mechanical and thermal properties of polymeric composites. However, the tendency of NDs to aggregate limits the potential of these non-toxic, mechanically- and chemically-robust nanofillers. In this work, tough, flexible, and stimuli-responsive polyelectrolyte films composed of cross-linked poly(butyl acrylate-co-dimethylaminoethyl methacrylate) (P(BA-co-DMAEMA)) were prepared by photopolymerization. The effects of the added carboxylate-functionalized NDs on their mechanical and stimuli-responsive properties were studied. When the negatively charged NDs were added to the polymerization media directly, the mechanical properties of the films changed only slightly, because of the uneven distribution of the aggregated NDs in the films. In order to disperse and distribute the NDs more evenly, a prepolymerized polycation block copolymer complexing agent was used during the photopolymerization process. This approach improved the mechanical properties of the films and enhanced their thermally-induced, reversible phase-transition behavior.

Interfacial Characteristics of Boron Nitride Nanosheet/Epoxy Resin Nanocomposites: A Molecular Dynamics Simulation

The interface between nanofillers and matrix plays a key role in determining the properties of nanocomposites, but the interfacial characteristics of nanocomposites such as molecular structure and interaction strength are not fully understood yet. In this work, the interfacial features of a typical nanocomposite, namely epoxy resin (EP) filled with boron nitride nanosheet (BNNS) are investigated by utilizing molecular dynamics simulation, and the effect of surface functionalization is analyzed. The radial distribution density (RDD) and interfacial binding energy (IBE) are used to explore the structure and bonding strength of nanocomposites interface. Besides, the interface compatibility and molecular chain mobility (MCM) of BNNS/EP nanocomposites are analyzed by cohesive energy density (CED), free volume fraction (FFV), and radial mean square displacement (RMSD). The results indicate that the interface region of BNNS/EP is composed of three regions including compact region, buffer region, and normal region. The structure at the interfacial region of nanocomposite is more compact, and the chain mobility is significantly lower than that of the EP away from the interface. Moreover, the interfacial interaction strength and compatibility increase with the functional density of BNNS functionalized by CH3–(CH2)4–O– radicals. These results adequately illustrate interfacial characteristics of nanocomposites from atomic level.

Colloids of detonation nanodiamond particles for advanced applications

Nanodiamond (ND) is one of the most attractive allotropic modification of carbon due to their unique physical and chemical properties. In the present review the current state of science and technology in the field of NDs is analyzed. ND can be used in various application and in different form e.g. as a dispersion phase in suspension, as a filler in composites, etc., so the sedimentation stability of ND in different media are under scrutiny. Thus, theoretical aspects of ND suspension coagulation mechanisms and the methods avoiding it were considered. The dependence of rheological behavior on particles modification was discussed as well. Various methods for the preparation and modification of NDs to obtain particles of various sizes on a nanometer scale with different physicochemical properties were reviewed. The area of practical application for NDs was considered on the example of polymer composites. The various manufacturing methods, mechanical properties and medical aspects for thermosetting, thermoplastic and elastomer ND composites were summarized.

Yttrium oxide nanoparticle loaded scaffolds with enhanced cell adhesion and vascularization for tissue engineering applications

In situ tissue engineering is emerging as a novel approach in tissue engineering to repair damaged tissues by boosting the natural ability of the body to heal itself. This can be achieved by providing suitable signals and scaffolds that can augment cell migration, cell adhesion on the scaffolds and proliferation of endogenous cells that facilitate the repair. Lack of appropriate cell proliferation and angiogenesis are among the major issues associated with the limited success of in situ tissue engineering during in vivo studies. Exploitation of metal oxide nanoparticles such as yttrium oxide (Y₂O₃) nanoparticles may open new horizons in in situ tissue engineering by providing cues that facilitate cell proliferation and angiogenesis in the scaffolds. In this context, Y₂O₃ nanoparticles were synthesized and incorporated in polycaprolactone (PCL) scaffolds to enhance the cell proliferation and angiogenic properties. An optimum amount of Y₂O₃-containing scaffolds (1% w/w) promoted the proliferation of fibroblasts (L-929) and osteoblast-like cells (UMR-106). Results of chorioallantoic membrane (CAM) assay and the subcutaneous implantation studies in rats demonstrated the angiogenic potential of the scaffolds loaded with Y₂O₃ nanoparticles. Gene expression study demonstrated that the presence of Y₂O₃ in the scaffolds can upregulate the expression of cell proliferation and angiogenesis related biomolecules such as VEGF and EGFR. Obtained results demonstrated that Y₂O₃ nanoparticles can perform a vital role in tissue engineering scaffolds to promote cell proliferation and angiogenesis.

An aggregated understanding of cellulase adsorption and hydrolysis for ball-milled cellulose

This study evaluated the effects of physicochemical properties of a series of ball-milled cellulose on cellulase adsorption and glucose yield. The relationship between cellulase adsorption and initial hydrolysis rate was also discussed. We found that hydrophobicity and surface charge are the key factors affecting cellulase adsorption on ball-milled cellulose. The results demonstrated that glucose yield had a positive correlation with specific surface area, while showed a negative correlation with particle size, degree of polymerization and crystallinity. Among these properties, specific surface area and crystallinity are the key factors affecting glucose yield. As ball milling progressed, cellulose showed lower enzyme adsorption capacity/amount of bound enzyme during initial stage of hydrolysis, but had higher initial hydrolysis rate. The enhanced rate is attributed to the fact that the amorphous region produced by ball milling reduces the free energy required for decrystallization thus increases the catalytic efficiency of the bound enzyme.

Novel three-dimensional interphase characterisation of polymer nanocomposites using nanoscaled topography

Mechanical properties of polymer nanocomposites depend primarily on nanointerphases as transitional zones between nanoparticles and surrounding matrices. Due to the difficulty in the quantitative characterisation of nanointerphases, previous literature generally deemed such interphases as one-dimensional uniform zones around nanoparticles by assumption for analytical or theoretical modelling. We hereby have demonstrated for the first time direct three-dimensional topography and physical measurement of nanophase mechanical properties between nanodiameter bamboo charcoals (NBCs) and poly (vinyl alcohol) (PVA) in polymer nanocomposites. Topographical features, nanomechanical properties and dimensions of nanointerphases were systematically determined via peak force quantitative nanomechanical tapping mode. Significantly different mechanical properties of nanointerphases were revealed as opposed to those of individual NBCs and PVA matrices. Non-uniform irregular three-dimensional structures and shapes of nanointerphases are manifested around individual NBCs, which can be greatly influenced by nanoparticle size and roughness, and nanoparticle dispersion and distribution. Elastic moduli of nanointerphases were experimentally determined in range from 25.32 ± 3.4 to 66.3 ± 3.2 GPa. Additionally, it is clearly shown that the interphase modulus strongly depends on interphase surface area and interphase volume. Different NBC distribution patterns from fully to partially embedded nanoparticles are proven to yield a remarkable reduction in elastic moduli of nanointerphases.

Changes in the physicochemical structure and pyrolysis characteristics of wheat straw after rod-milling pretreatment

Pyrolysis is increasingly used for raw biomass conversion. In this study, the effects of rod-milling pretreatment (RMP) on the physicochemical properties and pyrolysis characteristics of wheat straw (WS) was found. The mechanism behind these changes was further analyzed. RMP appreciably reduced the particle size and cellulose crystallinity, and increased the specific surface area and pore volume of WS. Under RMP, with an increasing conversion rate α, the activation energy E was expressed as a para-curve, whereas it was expressed as a tangent curve for samples that underwent hammer-milling pretreatment (HMP). At the same α, the thermal degradation temperature for RMP was lower than that for HMP. The E value clearly decreased with RMP, and increased following a wave-like pattern with increased rod-milling strength (RMS). The lowest E value (118.69 or 108.97 kJ/mol) was obtained with a milling time of 60 min. Hence, RMP is an environmental-friendly and effective method for improving the efficiency of pyrolysis.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis

Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer remains amorphous after coating of the rate controlling membrane, whether formed from an ethanol solution or an aqueous dispersion.

Combined effect of α-nucleating agents and glass fiber reinforcement on a polypropylene composite: a balanced approach

An approach by combining α-nucleating agents and glass fibre reinforcement for improving the comprehensive mechanical properties of polypropylene composite: a balanced approach.

Interphase Induced Dynamic Self-Stiffening in Graphene-Based Polydimethylsiloxane Nanocomposites

The ability to rearrange microstructures and self-stiffen in response to dynamic external mechanical stimuli is critical for biological tissues to adapt to the environment. While for most synthetic materials, subjecting to repeated mechanical stress lower than their yield point would lead to structural failure. Here, it is reported that the graphene-based polydimethylsiloxane (PDMS) nanocomposite, a chemically and physically cross-linked system, exhibits an increase in the storage modulus under low-frequency, low-amplitude dynamic compressive loading. Cross-linking density statistics and molecular dynamics calculations show that the dynamic self-stiffening could be attributed to the increase in physical cross-linking density, resulted from the re-alignment and re-orientation of polymer chains along the surface of nano-fillers that constitute an interphase. Consequently, the interfacial interaction between PDMS-nano-fillers and the mobility of polymer chain, which depend on the degree of chemical cross-linking and temperature, are important factors defining the observed performance of self-stiffening. The understanding of the dynamic self-stiffening mechanism lays the ground for the future development of adaptive structural materials and bio-compatible, load-bearing materials for tissue engineering applications.

Mechanical fragmentation of corncob at different plant scales: Impact and mechanism on microstructure features and enzymatic hydrolysis

In this work, corncob samples at different scales, i.e., plant scale (>1mm), tissue scale (500-100μm) and cellular scale (50-30μm), were produced to investigate the impact and mechanisms of different mechanical fragmentations on microstructure features and enzymatic hydrolysis. The results showed that the microstructure features and enzymatic hydrolysis of corncob samples, either at a plant scale or tissue scale, did not change significantly. Conversely, corncob samples at a cellular scale exhibited some special properties, i.e., an increase in the special surface area with the inner mesopores and macropores exposed to the surface; breakage of crystalline cellulose and linkages in polysaccharides; and a higher proportion of polysaccharides on the surface, which significantly enhanced enzymatic digestibility resulting in a 98.3% conversion yield of cellulose to glucose which is the highest conversion ever reported. In conclusion, mechanical fragmentation at the cellular scale is an effective pretreatment for corncob.