Volume 37, Issue 5

Electron beam (EB) processing of pristine and filled polymeric materials is considered as one of the most viable techniques in the development of three-dimensional (3D) network structures of polymeric or composite systems with improved physical and chemical properties. The grafting, or the crosslinking process induced by the merging of the macro free radicals generated during the electron beam modification without the aid of any chemical agent or heat, is responsible for the formation of the 3D networks in polymeric systems. Owing to its distinct advantages such as fast, clean and precise, electron beam (EB) radiation technology takes up a vital role in the crosslinking of polymeric compounds. However, during the course of electron beam treatment of polymers, two processes viz ., crosslinking and chain scission take place simultaneously, depending on the level of radiation dose used for the processing. The present paper reviews the role of irradiation dose in the presence and absence of radiation sensitizer on the crosslinking and structure formation in a wide variety of soft matrices such as elastomers, latexes, thermoplastic elastomers and their respective filled systems. Notable improvements in mechanical and dynamic mechanical properties, thermal stability, processing characteristics, etc., of the EB processed elastomers and their composites are discussed elaborately in the paper. Specially, the property improvements observed in the EB processed pristine and filled rubbers in comparison to the conventional crosslinking technology are critically reviewed. The level of radiation dose inducing crosslinking in both pristine and filled rubbers, determined by calculating crosslink to scission ratio on the basis of Charlesby–Pinner equation is also discussed in the paper. Finally, the application aspects of electron beam curing technology with special emphasis to cable and sealing industries as developed by one of the authors are highlighted in the paper.

The numerous combinations of different rubbers as matrix materials with graphene/graphene derivatives as nanofillers, which are used to fabricate graphene/rubber nanocomposites, are illustrated in this study. The different processing methods for producing graphene/rubber nanocomposites are investigated in depth. Furthermore, based on the results of various experiments performed with the produced graphene/rubber nanocomposites, an attempt is made to establish an outline over the influence of graphene nanofillers inside the rubber matrix. To explain the composite material characteristics, different processes, and the consequence of the incorporation of graphene/graphene derivatives nanofillers, a unique approximation has been accomplished.

Biodegradable polymers have become important in different fields of application, where biodegradability and biocompatibility are required. Herein, the melt spinning of biodegradable polymers including poly(lactic acid), poly(butylene succinate), polyhydroxyalkanoate (PHA), poly(ɛ-caprolactone) and their biocomposites is critically reviewed. Biodegradable polymer fibers with added functionalities are in high demand for various applications, including biomedical, textiles, and others. Melt spinning is a suitable technique for the development of biodegradable polymer fibers in a large-scale quantity, and fibers with a high surface area can be obtained with this technique. The processing variables during spinning have a considerable impact on the resulting properties of the fibers. Therefore, in this review, the processing-property relationship in biodegradable polymers, blends, and their composites is provided. The morphological characteristics, load-bearing properties, and the potential application of melt-spun biodegradable fibers in various sectors are also provided.

In this paper, poly(butylene succinate) (PBS)/polylactide (PLA)/poly(vinyl acetate) (PVAc) ternary blends were prepared via directly blending. The content of PBS in each sample was fixed at 30 wt% and that of PVAc was different, 2, 4 or 6%. PBS/PLA (30/70, g/g) and PLA/PVAc (66/4, g/g) were also prepared for comparison. XRD and DSC results showed that PVAc was miscible with PLA, and the crystallinity ( X c ) of PLA in PBS/PLA increased by adding PBS, but X c of PBS and PLA in PBS/PLA/PVAc ternary blends reduced by adding PVAc. SEM images showed that PBS was dispersed as droplets in each blend The addition of PVAc improved the compatibility between PBS and PLA, and the fracture surfaces of the ternary blends became rougher than that of PBS/PLA. The tensile and impact tests results showed that PVAc could enhance PLA and the highly toughened PBS/PLA blend. Finally, PBS/PLA/PVAc blend with 2% of PVAc was highly toughened without sacrificing its strength. Its strength was the same as that of PBS/PLA, while the elongation at break and impact strength of the former were 2.8 and 2.5 times those of the latter.

In this paper, the parameters affecting the sealing life of UHMWPE and PTFE in ultra high pressure systems were investigated. A life test system was designed and manufactured in which different parameters can be tested in the sealing construction. The life test system consists of two hydraulic pressure intensifiers, and a hydraulic and electronic control unit. The effects of the extrusion gap, piston rod material and surface roughness, in addition to the material, geometry and number of the sealing elements, on the life of the sealing members were investigated. Two levels were determined for each parameter, and experiments were carried out at a pressure of 450 MPa according to a Taguchi L8 orthogonal experimental design. Pressure intensifiers were operated reciprocatively, thus allowing to perform two tests simultaneously, saving time. Working cycles of the pressure intensifiers were measured. Each experiment continued until the seals were damaged, and a critical leakage rate occurred at the pressure intensifiers. ANOVA was applied to the experimental results. According to the results, the most significant parameter affecting the sealing life is the extrusion gap with a rate of 77%, followed by the piston rod surface roughness with a rate of 13%, and the piston rod material with a rate of 4%. The effects of the remaining parameters on the sealing life are more limited. The results obtained will contribute to the industrial design of sealing structures for ultra-high pressures.

A styrene-butadiene-styrene (SBS) modified asphalt compound was prepared by the addition of polyphosphoric acid (PPA) and sulfur. The effect of PPA and sulfur on major physical properties, including toughness and tenacity, aging resistance, and storage stability was investigated. The structural characteristics of SBS-modified (SM) asphalt, SBS/PPA-modified (SPM) asphalt, and SBS/PPA/sulfur-modified (SPSM) asphalt were investigated using scanning electron microscopy (SEM), gel filtration chromatography (GPC), and thermal analysis. It has been found that acidification prompted the clustering of SBS particles and confined the swelling of SBS, making SPM asphalt more susceptible to aging. Vulcanization changed the morphological characteristics of SBS in asphalt, improved the compatibility between SBS and asphalt, and weakened the aging susceptibility. Therefore, it is reasonable to modify SM asphalt by using PPA and sulfur together.

One possible way to increase the use of bioplastics and thus contribute to a more resource-efficient and sustainable economy is to broaden the application range of such bioplastics. Poly(lactic acid) (PLA) is a promising and commercially available bio-based and biologically degradable polymer, which exhibits a high strength and stiffness but is very brittle. Blending with other polymers can lead to an enhancement of the ductility of the PLA. The goal of this work was to show that blending of PLA with a bio-based thermoplastic polyester-urethane elastomer (TPU) increases the ductility of the compound and also affects the adhesion of the layers when the materials – the modified PLA compound and the TPU – are processed via two-component (2C) injection molding to form corresponding composite parts. The results show that both goals – the increased ductility as well as the increased adhesion between the polymeric phases in 2C parts – can be reached by compounding PLA with two different bio-based polyester-based TPUs. Tensile strength and Young’s modulus of the compounds decrease according to a linear mixing rule with the addition of TPU. Elongation at break and notched Charpy impact strength increase by 750 and 200%, respectively. By addition of the TPU, the surface free energies of the compounds were increased, especially the polar parts. This led to reduced interfacial tensions between the produced compounds and the neat TPUs and thus increased the adhesion between them. For the softer TPU the adhesion was so strong that the TPU showed a cohesive failure in the 90° peel test and thus could not be separated from the compound substrate at all. For the harder TPU the bonding strength increased by 140% upon the addition of this TPU inside the hard component.

The objective of this research is to produce and analyze natural fiber-based composites (sisal/polyester, kenaf/polyester, pineapple/polyester) and their hybrid composites (sisal/kenaf/polyester, kenaf/pineapple/polyester, and sisal/kenaf/pineapple/polyester) made by compression molding. These composites were characterized mechanically using hardness (shore D), tensile, flexural, and impact (Charpy) tests. Fiber matrix bonding was analyzed using Scanning Electron Microscopy (SEM). Among all the fiber-based samples (sisal/polyester, kenaf/polyester, and pineapple/polyester), sisal/polyester shows a high hardness value of 93.24 S d, a tensile strength of 43.00 MPa, and an impact strength around 7.42 kJ/m 2 , while pineapple/polyester produces a better flexural strength of 83.21 MPa. Hybrid composites showed improved mechanical performance. The mechanical characteristics of the sisal/kenaf/pineapple/polyester hybrid composite were 56.16 MPa, 1.71 GPa, and 9.34 kJ/m 2 . The highest flexural strength of the Sisal/kenaf/polyester multi-layered samples was observed as 83.24 MPa.