Volume 40, Issue 8

Polymer blends have been widely used as tribological materials for replacements of traditional metals and ceramics. Polymer blends consist of the reinforced phase, the matrix phase and interfaces between reinforced and matrix phase. Although the interface structure of polymer blends is usually small in size, it is one of the key factors for deciding the physical and tribological properties of polymer blends. Thus, this review highlights the most recent trends in the field of influences of interface structure on tribological properties of engineering polymer blends. Emphasis is given to the improvement methods of interfacial compatibility of polymer blends and the behavior variation of interface structure during friction process.

In this work, polypropylene (PP) filled with different proportions of CoSt were prepared in a twin-screw extruder by compounding technique. Eight films of these compounds were prepared using compression moulding. The modified PP films were characterized for chemical, physical, thermal, and morphological properties (before and after biodegradation). The biodegradation of the CoSt filled PP films was studied under controlled composting conditions, and the degradation intermediates were evaluated for their ecotoxicological impact. The CoSt present in the PP film was confirmed by Fourier transform infrared spectroscopy. As the addition of CoSt was progressively increased, the tensile strength and thermal stability decreased as shown by UTM and thermogravimetric analysis. The compounding of CoSt in PP reduced its crystallinity as revealed by the differential scanning calorimetry and X-ray diffraction analysis, and this led to enhanced degradation of PP. After biodegradation, SEM results of modified PP films showed rougher morphology than before biodegradation. The maximum biodegradation (19.78%) was shown by the film having 2 phr CoSt. The ecotoxicity tests of the degraded material, namely, microbial test, plant growth test, and earthworm acute-toxicity test demonstrated that the biodegradation intermediates were nontoxic. Hence, CoSt filled PP has high industrial potential to make biodegradable flexible packaging.

In this study, retinoic acid loaded-PLGA-gelatin matrixes were prepared with both freeze-casting and freeze-drying techniques. Herein, the effect of unidirectional microstructure with tunable pores on release profile, cellular adhesion, migration, and differentiation was compared. Morphological observation determined that highly interconnected porous structure can be formed, but lamellar pore channels were observed in freeze-casting prepared constructs. The absorption ratio was increased, and the biodegradation rate was decreased as a function of the orientation of microstructure. The in-vitro release study illustrated non-Fickian release mechanism in both methods, so that erosion has predominated over diffusion. Accordingly, PLGA-gelatin scaffolds prepared with freeze-drying technique showed no adequate erosion due to the rigid structure, while freeze-casting one presented more favorable erosion. Microscopic observations of adhered P19 embryonic cells on the scaffolds showed that the freeze-casting matrixes with unidirectional pores provide a more compatible microenvironment for cell attachments and spreading. Besides, it facilitated cell migration and penetration inside the structure and may act as guidance for neuron growth. Improvement in the expression of neural genes in unidirectionally oriented pores proved the decisive role of contact guidance for nerve healing. It seems that the freeze-cast PLGA-gelatin-retinoic acid scaffolds have initial features for nerve tissue regeneration studies.

A novel optical probe consistinsg of Ag@PANI (silver-polyaniline) nanocomposites was developed for detection of mercury ions (Hg 2+ ). The poly-dispersed Ag@PANI nanocomposites were synthesized by complexation reaction method. We studied structural and functional properties of polymer nanocomposites thoroughly. Ag@PANI nanocomposites consist of fibrous morphology with a mean particle size of 31.39 nm. Ag@PANI nanocomposites consist of face-centered cubic crystal structure with an average crystallite size of 19.41 nm. Raman spectroscopy was used in sensitive and selective detection of Hg 2+ ions in dynamic range of 0.01–0.1 ppm with limit of detection of 0.019 ppm. Ag@PANI nanocomposite sensor for Hg (II) ions has shown some sublime results in pH range 3–5. Ag@PANI-based sensing probe can be beneficial for Hg 2+ ions detection in highly sensitive biological, chemical and environmental analysis. Our sensing probe has shown good reproducibility, and all recorded observations revealed that sensing probe consisting of Ag@PANI nanocomposites is well suited for detection of Hg 2+ ions.

Porous implants play a crucial role in allowing ingrowth of host connective tissue and thereby help in keeping the implant in its place. With the aim of mimicking the microstructure of natural extracellular matrix, ultrahigh-molecular-weight polyethylene (UHMWPE) porous samples with a desirable pore size distribution were developed by combining thermally induced phase separation and salt leaching techniques. The porous UHMWPE samples consisted of a nanofibrous UHMWPE matrix with a fibre diameter smaller than 500 nm, highly interconnected, with a controllable pore diameter from nanoscale to 300 µm. Moreover, a porous UHMWPE sample was also developed as a continuous and homogeneous coating onto the UHMWPE dense sample. The dense/porous UHMWPE sample supported human foetal osteoblast 1.19 cell line proliferation and differentiation, indicating the potential of porous UHMWPE with a desirable pore size distribution for bone application. An osseointegration model in the sheep revealed substantial bone formation within the pore layer at 12 weeks via SEM evaluation. Ingrown bone was more closely opposed to the pore wall when compared to the dense UHMWPE control. These results indicate that dense/porous UHMWPE could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic application.

This work focuses on the potential use of cellulose fibers extracted from Mediterranean saltbush ( Atriplex halimus ) as a filler in the polymeric matrix. The fully biodegradable composites were prepared from polylactic acid (PLA) as matrix and microcellulose fibers ranging from 0 to 15 wt.%. The influence of the fiber content on the structure, mechanical, thermal, and water absorption properties was evaluated. Mechanical results indicated that fibers acted effectively as reinforcement, increasing the tensile strength and the Young’s modulus of PLA by 25 and 45%, respectively. This is due to the good stress transfer between fibers and matrix through the strong interactions that have been evidenced by Fourier Transform Infrared (FTIR) spectroscopy. The thermogravimetric analysis showed that PLA composites have a slightly lower degradation temperature than the pure PLA, but they still have favorable thermal stability. Water absorption measurements and biodegradability tests showed that the addition of fibers accelerates degradation kinetics and confirm that the prepared composites are an environmentally safe material suited for different applications.

Glass ceramics from the CaO–P 2 O 5 –SiO 2 system were synthesized. They were characterized by XRD, SEM and EDX methods. It was found that they contain two crystalline [Whitlockite, Ca 3 (PO 4 ) 2 and Hydroxylapatite, Ca 5 (PO 4 ) 3 (OH)] and one residual amorphous phase. The ceramics are composed of porous aggregates of fine particles with predominant macro- and mesopores in it. The ceramics were used as a functional filler in natural rubber based composites, as the filling is in the range of 5–50 phr. The influence of the chemical nature and structure of the ceramics and the degree of filling on the vulcanization characteristics, physicomechanical parameters, dielectric and dynamic properties, the coefficient of thermal conductivity and the volume resistivity, including external pressure or bending on the specimens were investigated. An influence of the filler and the degree of filling on all studied properties was found. All tested composites have dielectric parameters ( ε ′, real part of complex permittivity; ε ′′, imaginary part of complex permittivity; σ , conductivity; tan δ ɛ , tangent from dielectric loss angle) suitable for use as substrates and insulating layers of flexible antennas. Particularly impressive are composites containing 30 and 50 phr fillers, which have the lowest tangent from dielectric loss angle values.

Star-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss ( T d5 ) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

This article describes the development of a mathematical model of forward roll coating of a thin film of a non-Newtonian material when it passes through a small gap between the two counter-rotating rolls. The conservation equations of mass, momentum, and energy in the light of LAT (lubrication approximation theory) are non-dimensionalized and solutions for the velocity profile, flow rate, pressure distribution, pressure, forces, stresses, power input to the roller, and temperature distribution are calculated analytically. It is found that by changing (increasing/decreasing) the value of material parameters, one can really control the engineering parameters like, stress and the most important the coating thickness and is a quick reference for the engineer working in coating industries. Some results are shown graphically. From the present study, it has been established that the material parameter is a device to control flow rate, coating thickness, separation points, and pressure distribution.