József Karger-Kocsis

Polypropylene Structure, blends and composites

Volume 1: Polymorphism in polypropylene homo- and copolymers. Molecular structure of polypropylene homo- and copolymers. Crystalline structures of polypropylene homo- and copolymers. Crystallisation, melting and supermolecular structure of isotactic polypropylene. Nucleation of polypropylene. Epitaxial growth on and with polypropylene. Processing-induced structure. Higher order structure of injection-moulded polypropylene. Knit-line behaviour of polypropylene and polypropylene-blends. Welding and fracture of polypropylene interfaces. Self-reinforcement of polypropylene. Processing-induced structure formation. Volume 2: Manufacturing and properties of polypropylene copolymers. Primary spherulite nucleation in polypropylene-based blends and copolymers. Polypropylene alloys and blends with thermoplastics. Structure and properties of polypropylene-elastomer blends. Oriental drawing of polypropylene and its blends. Thermoplastic elastomers by blending and dynamic vulcanization. Index. Volume 3: Particulate-filled polypropylene: structure and properties. Processing and properties of reinforced polypropylenes. Fibre orientation prediction in injection moulding. Microstructural aspects of fracture in polypropylene and in its filled, chopped fibre and fibre mat reinforced composites. Glass mat reinforced polypropylene. Some wetting and adhesion phenomena in polypropylene composites. Manufacturing methods for long fibre reinforced polypropylene sheets and laminates. Thermoforming of unidirectional continuous fibre-reinforced polypropylene laminates and their modelling. Fracture performance of continuous fibre reinforced polypropylene. Interfacial crystallization of polypropylene in composites. Index.

Ground tyre rubber (GTR) in thermoplastics, thermosets, and rubbers

The disposal of worn tyres and their economic recycling mean a great challenge nowadays. Material recycling is the preferred way supported by legislative actions and economical/ecological arguments. This paper surveys the recent developments devoted to the reclamation, surface treatments, and to the use of ground tyre rubber (GTR) in thermoplastics, thermosetting resins, and rubber formulations. This review discloses also the principle underlying compatibilization to improve the adhesion of GTR to the corresponding matrix. It was concluded that value-added application of GTR can especially be expected in thermoplastic elastomers, and rubber combinations.

Effects of steel counterface roughness and temperature on the friction and wear of PE(E)K composites under dry sliding conditions

Abstract The friction and wear behavior of virgin polyetheretherketone (PEEK) and of polyetherketone (PEK) and PEEK composites, including different types and amounts of fiber reinforcement and/or lubricating agents, was studied as a function of steel counterface roughness and testing temperature. Roughness effects were more pronounced in the non-reinforced PEEK than in the fiber-filled versions. An increase in testing temperature resulted in higher specific wear rates and in lower coefficients of friction for the different materials tested. The incorporation of carbon fibers proved to be more beneficial than glass fibers with respect to both friction and wear performance. The composition with the highest resistance to wear at elevated temperatures ( e.g. 220 °C) and a low coefficient of friction ( μ p = 1 MPa and v =1 m s −1 respectively) was a PEEK version containing 15 wt.% polytetrafluoroethylene (PTFE) particles and 15 wt.% graphite lubricant.

Molecular dependence of the essential and non-essential work of fracture of amorphous films of poly(ethylene-2,6-naphthalate) (PEN)

Abstract Plane stress fracture toughness of amorphous films of poly(ethylene-2,6-naphthalate) (PEN) with various molecular weights (MW; characterized by the intrinsic viscosity, IV) was determined by the essential work of fracture (EWF) concept using tensile-loaded deeply double-edge notched (DDEN-T) specimens. These PENs met the basic requirement of the EWF concept: full ligament yielding, which was marked by a load drop in the force–displacement curves of the DDEN-T specimens, preceded the crack growth. This “load mark” allowed us to partition between yielding and necking. The yielding-related EWF terms were not affected by the MW of the resins and thus served for the comparison of the results. It is argued that the EWF response is governed by the entanglement network density. The role of entanglements was substantiated by showing that the “plastic” zone developed via cold drawing and not by true plastic deformation. On the other hand, MW influenced the necking related EWF terms. High MW PENs failed by stable crack growth, whereas low MW resins experienced unstable crack growth (more exactly a transition from stable to unstable crack growth) in the necking phase. This was traced to the load distribution capacity of the long entangled chains. Attempts were also made to estimate the essential and non-essential work of fracture parameters and their constituents from uniaxial tensile tests performed on dumbbells.

For what kind of polymer is the toughness assessment by the essential work concept straightforward

SummaryThe essential work of fracture (EWF) concept seems to be a proper and easy way to determine the inherent fracture behavior of ductile polymers. Unfortunately, all experiments reported until now were performed on polymers which did not meet the basic requirement of this fracture mechanical approach, viz. full ligament yielding prior to onset of crack growth. This problem often resulted in wrong conclusions and useless discussions on the specimen preparation, including notching techniques. By using tensile-loaded deeply double-edge notched (DDEN-T) specimens of amorphous copolyesters (aCOP) it was demonstrated that they are, in fact, the optimum choice to push forward the EWF concept for ductile polymers. Full ligament yielding before crack growth was evidenced by infrared thermographic (IT) frames taken during the loading of the DDEN-T specimens. The yielding “marked” with a load-drop in the corresponding load-displacement curves, enabled to split both the specific essential and non-essential work of fracture into their contribution terms: yielding and necking incl. fracture, respectively. It was argued that this EWF approach is most straightforward for the toughness description of such amorphous polymers that undergo necking by (multiple) shear banding without considerable strain-hardening, as aCOPs do.

Thermoplastic elastomers based on compatibilized poly(ethylene terephthalate) blends: effect of rubber type and dynamic curing

Thermoplastic elastomers containing poly(ethylene terephthalate) (PET) in 50 wt%, compatibilizer (glycidyl methacrylate grafted rubber or glycidyl methacrylate containing copolymer) in 30 wt% and various rubbers (20 wt%) were produced by melt blending with and without dynamic curing (dicumyl peroxide initiated). The static tensile (stress‐strain behaviour) and dynamic mechanical thermal properties (DMTA) of the systems along with their phase morphology (scanning electron microscopy of cryofractured and etched surfaces) were determined. It was found that the blend compatibility with PET is strongly improved when a high acrylonitrile-containing nitrile rubber (NBR) and an ethylene-glycidyl methacrylate copolymer (EGMA) or a GMA grafted ethylene/propylene rubber (EPR-g-GMA) are used as rubber and/or compatibilizer in the blend recipes. The effect of dynamic curing on the tensile and DMTA properties of the blends was negligible. Fractographic inspection of the fractured surface showed the development of a co-continuous phase structure which was in accordance with learnings from the DMTA spectra. q 2000 Elsevier Science Ltd. All rights reserved.

Shape memory characteristics of woven glass fibre fabric reinforced epoxy composite in flexure

Shape memory characteristics of a woven glass fibre fabric reinforced epoxy composite (reinforcement content: 38 vol.%) were assessed in three-point bending mode in a dynamic mechanical analysis device and compared to those of the parent epoxy resin. From unconstrained tests, the shape fixity and recovery ratios and the recovery rate, whereas from constrained tests the recovery stress were determined. The shape fixity and recovery rate decreased due to the glass fibre reinforcement which had, however, no effect on the shape recovery. Major benefit of the woven glass fibre fabric was that the recovery stress could be enhanced by two orders of magnitude in comparison to the neat epoxy. Glass fibre reinforcement was accompanied with a substantial decrease in the failure-free flexural deformability of the composite specimen.

Determination methods of the grafting yield in glycidyl methacrylate-grafted ethylene/propylene/diene rubber (EPDM-g-GMA): Correlation between FTIR and1H-NMR analysis

A normalized and universally applicable calibration function for the Fourier-transformed infrared (FTIR) quantification of the glycidyl methacrylate (GMA) grafting yield in polymers of known compositions having ethylene block sequences was established. The 1H nuclear magnetic resonance (1H-NMR) spectroscopy results achieved on different GMA-grafted ethylene/propylene/diene rubber (EPDM-g-GMA) and ethylene/GMA copolymers were correlated to their FTIR data to calibrate the relative determination of the FTIR method. Both direct and indirect standardization approaches were followed and evaluated. The calibration deduced was used to investigate the free radical grafting reaction of GMA on EPDM rubber in the melt phase.

Water-Assisted Production of Thermoplastic Nanocomposites: A Review

Water-assisted, or more generally liquid-mediated, melt compounding of nanocomposites is basically a combination of solution-assisted and traditional melt mixing methods. It is an emerging technique to overcome several disadvantages of the above two. Water or aqueous liquids with additives, do not work merely as temporary carrier materials of suitable nanofillers. During batchwise and continuous compounding, these liquids are fully or partly evaporated. In the latter case, the residual liquid is working as a plasticizer. This processing technique contributes to a better dispersion of the nanofillers and affects markedly the morphology and properties of the resulting nanocomposites. A survey is given below on the present praxis and possible future developments of water-assisted melt mixing techniques for the production of thermoplastic nanocomposites.

Epoxy/Polycaprolactone Systems with Triple-Shape Memory Effect: Electrospun Nanoweb with and without Graphene Versus Co-Continuous Morphology

Triple-shape memory epoxy (EP)/polycaprolactone (PCL) systems (PCL content: 23 wt %) with different structures (PCL nanoweb embedded in EP matrix and EP/PCL with co-continuous phase structure) were produced. To set the two temporary shapes, the glass transition temperature (Tg) of the EP and the melting temperature (Tm) of PCL served during the shape memory cycle. An attempt was made to reinforce the PCL nanoweb by graphene nanoplatelets prior to infiltrating the nanoweb with EP through vacuum assisted resin transfer molding. Morphology was analyzed by scanning electron microscopy and Raman spectrometry. Triple-shape memory characteristics were determined by dynamic mechanical analysis in tension mode. Graphene was supposed to act also as spacer between the nanofibers, improving the quality of impregnation with EP. The EP phase related shape memory properties were similar for all systems, while those belonging to PCL phase depended on the structure. Shape fixity of PCL was better without than with graphene reinforcement. The best shape memory performance was shown by the EP/PCL with co-continuous structure. Based on Raman spectrometry results, the characteristic dimension of the related co-continuous network was below 900 nm.