Advanced Industrial and Engineering Polymer Research最新文献

The highly conjugated chemical structure of polyimide fibers has endowed polyimide with outstanding mechanical properties, high thermal stability, good solvent resistance, and excellent light stability, resulting in a wide application prospect in aerospace, environmental conservation and other fields. However, the preparation of the fiber is very complicated compared to other organic fiber. With the expansion of production scale and continuous technical progress of polyimide fiber, the cost of fiber shows a downward trend and the product specifications are constantly enriched, which promoted the continuous expansion of the application of the polyimide fiber in many fields. This review focuses on the preparation methods, structure and properties and application of the fiber.

Because of their exceptional mechanical properties, carbon fibers are being used in composite applications where weight saving is key such as in the aerospace and sports sector, with increasing demands coming from wind energy, aerospace and defense. However, an even more significant increase in demand in automotive is foreseen if the cost price of carbon fiber could come down substantially. In 2012 the US Department of Energy set a target price level of 10 USD/kg to get carbon fiber into mainstream cars. These low-cost carbon fibers should possess a tenacity of at least 1.7 GPa with a corresponding elastic modulus of 170 GPa. Carbon fibers are currently predominantly based on polyacrylonitrile (PAN) precursor fibers, while pitch is used for some high-modulus fibers. The cost price of PAN-based carbon fibers is determined for at least 50% by the PAN precursor. Consequently, over the last decade huge R&D programs have been undertaken in search of cheaper and more sustainable precursors such as lignin and polyethylene. Despite major efforts no significant commercial successes have been obtained up to now in stark contrast with numerous claims in the scientific literature regarding so-called breakthrough technologies. Next to the recent revival in carbon fiber research another carbon allotrope, the carbon nanotube (CNT), has received huge attention as the ‘next generation’ reinforcing element for composites. Fibers and yarns have been made directly from CNTs or have been added into other high-performance fibers to boost their properties. However, also here despite major research efforts and numerous high impact publications the results obtained were at best interesting or doubtful with little commercial success.

In the previous chapters the emphasis was on high-performance fibers/tapes based on flexible chain polymers and in terms of strength and stiffness, the primus inter pares is ultra-highmolecular-weight polyethylene, UHMW-PE. These developments on flexible polymer molecules stem from the 1980s but were preceded by the development of high-performance fibers based on (more) rigid polymer chains, notably the aromatic polyamides or abbreviated (poly)aramids. These fibers were developed in the 1960s/1970s and considered at that time as a major disruptive innovation involving liquid-crystalline behaviour of polymer solutions. In this chapter the developments and future outlook of aramid fibers nowadays well known as Kevlar®/Du Pont and Twaron®/Teijin, will be discussed, as well as aromatic polyesters and rigid rod polymers M5 and PBO. In the last chapter ‘Epilogue’ the properties of aramid vs. PE fibers will be critically compared and discussed in view of current competition in the market notably in the ballistic applications and in ropes (mooring lines).

Polyethylene (PE) fibers based on ultra-high-molecular-weight polyethylene, UHMW-PE, have been developed successfully with outstanding specific values for strength and stiffness, at least at ambient temperature, as discussed in the previous chapters. But this relatively new class of high-performance PE fibers also possesses some limitations notably a relatively low melting temperature, appr. 150 °C, and relatively poor long-term properties viz. pronounced creep. The questions to be asked is whether other flexible polymer molecules as possible candidates for high-performance fibers are preferably available with stronger intermolecular interactions, i.e. hydrogen bonding or other polar interactions, than the weak Van der Waals interactions prevailing in between the polyethylene chains. In this chapter this question will be addressed and potential polymer candidates will be discussed.

High-performance polymer fibers are indispensable materials for human society and are used in the field of national defense, aerospace, automobile manufacturing and sports equipment, etc. At present, the commonly used high-performance fibers are man-made and oil-based such as carbon fibers, ultra-high molecular weight polyethylene e.g. UHMWPE, Dyneema® from DSM, the aromatic polyamide fibers e.g. Kevlar® from Du Pont and Twaron® from Teijijn Aramid (formerly Akzo Nobel), etc. In principle, these materials are not biocompostable and hence after service life can pollute the environment if not recovered e.g. as lost ‘ghost’ fishing nets in the oceans.

Nowadays, some companies make an endeavour to produce these fibers from bio-mass or recycled sources. For example, there are bio-based Dyneema® grades available from DSM from recycled sources and carbon fibers can in principle be produced from polyacrylonitrile, which is made form bio-based acetonitrile as being under development by e.g. Solvay and Aksa/Dow. But these so-called ‘drop-in’ fibers are exactly the same as their fossil-based counterparts, and therefore not biocompostable!

Consequently, it will be very meaningful if bio-based environmentally friendly fibers with both high-performance and biocompostability could be traced in Nature and/or developed from biomass to reduce environmental pollution. In this review, several typical well-known natural bio-based (cellulose and silk) and synthetic, man-made, biocompostable polymer fibers (polylactic acid fiber and polyglycolic acid fibers) are discussed as potential high-performance bio-based polymer fibers candidates. Their sources, structure, preparation methods and mechanical properties are discussed and their performance is compared with some standard high-performance fibers.

In the previous chapter the development of high-performance PE fibers via solution(gel)-spinning was discussed. The success of the simple solution(gel)-spinning process was a big incentive to explore other polymers as well as candidates for high-performance fibers, such as polypropylene and polar polymers like poly(vinyl alcohol) (PVOH) and poly(acrylonitrile) (PAN). In this chapter solution(gel)-spinning of polypropylene (PP) fibers will be discussed and subsequently the use of PP fibers and tapes in self-reinforced composites. In the second part of this chapter, tapes based on UHMW-PE are presented.

Direct methanol fuel cells (DMFCs) are an essential aspect of electricity and fuel concerns. Herein, we report a new combination of Palladium nanoparticles anchored on polydiphenylamine with reduced graphene oxide network (rGO/PDPA/Pd) nanohybrid synthesized via an in-situ chemical strategy. The rGO/PDPA/Pd electrocatalyst shows excellent electrocatalytic activity, lower oxidation potential (−0.1 V), improved current density (2.85 mA/cm²), excellent cyclic stability (94%), and longevity (1200 s) towards methanol oxidation reaction (MOR) in the alkaline medium, when compared to commercial Pd/C electrocatalyst. Significantly, the forward oxidation peak potential of rGO/PDPA/Pd electrocatalyst was shifted negatively by 110 mV as compared to commercial Pd/C electrocatalyst. These results suggest that rGO/PDPA/Pd electrocatalyst is considered as an effective anode catalyst for DMFCs.

The primary objective of this research paper is to detect and quantify the necking defect and surface velocity profiles in high-speed polymer melt extrusion film casting (EFC) process using Matlab® based image processing techniques. Extrusion film casting is an industrially important manufacturing process and is used on an industrial scale to produce thousands of kilograms of polymer films/sheets and coated products. In this research, the necking defect in an EFC process has been studied experimentally and the effects of macromolecular architecture such as long chain branching (LCB) on the extent of necking have been determined using image processing methodology. The methodology is based on the analysis of a sequence of image frames taken with the help of a commercial CCD camera over a specific target area of the EFC process. The image sequence is then analyzed using Matlab® based image processing toolbox wherein a customized algorithm is written and executed to determine the edges of the extruded molten polymeric film to quantify the necking defect. Alongwith the necking defect, particle tracking velocimetry (PTV) technique is also used in conjunction with the Matlab® software to determine the centerline and transverse velocity profiles in the extruded molten film. It is concluded from this study that image processing techniques provide valuable insights into quantifying both the necking defect and the associated velocity profiles in the molten extruded film.

With the escalation in continuous human curiosity, massive research work is going on in the field of inflatable structures and inflatable systems. These inflatable structures offer a great advantage for the building of emergency air shelters for civilian and military, industrial fuel and gas storage tanks, life rafts, lifeboats, etc. Even, more advanced inflatables like hull structure for lighter-than-air systems (LTA) and inflated radomes are employed in the defence sector. The advantage of inflatable structures lies on their excellent mechanical strength, lightweight, durability and they can be stored in a small volume. Specialty elastomers play an important role in developing inflatable structures because of their excellent properties towards weather resistance, UV and ozone resistance, stability against aging, and oxidation. In addition, they show good gas and vapour barrier properties. In the beginning of this review article, the structure and properties of specialty elastomers selected in this study have been discussed and then the gas transport mechanism through polymeric material is described. In the last part, the development of diverse types of inflatable systems used in industry, defence, and marine applications have been highlighted. More attention is given to the advanced application of inflatables in the defence sector. Throughout this review work, various literature and published work related to specialty elastomers application in inflatable systems have been reviewed. The main emphasis of this study is on the structure, properties and application of specialty elastomers in the advancement of inflatable structures.