H. H. Kausch

• Prof. Dr. Dr. h.c.
• Managing Director at Swiss Federal Institute of Technology in Lausanne

not permitted

Fracture of polymers is defined as the stress-biased material disintegration through the formation of new surface within a body. The essential molecular damage mechanisms leading to crack initiation followed by stable and/or unstable crack propagation are described; fracture phenomena are identified and quantified using different concepts of fractu...

In this article the role of voids or particulate inclusions of different sizes on mechanical properties and particularly on toughness in several polymers is discussed. With decreasing void sizes and intervoid distances, the influence of the interphase material around the voids becomes more important and characteristic changes in the nano- and micro...

A definition of macromolecular science (as opposed to polymer science and engineering) is given, from which the year 1930 is derived as the year of its birth. The scope of treatment of this paper will be limited to solid technical polymers. Some important discoveries of polymer technology in the nineteenth century are reviewed together with the rea...

We have explored a new technology based on chemically induced phase separation that yields porous epoxies and cyanurates with a closed cell morphology and micrometer sized pores with a narrow pore size distribution. When the precursor monomers are cured in the presence of a low molecular weight liquid, the desired morphology results from a phase se...

Polymer strength depends on the nature of the constituting elements and their mechanical, thermal, and otherwise physical, but also chemical interaction. Some of these mechanisms are discussed in this paper; special attention is given to disentanglement and chain scission.

Different types of polymer nanocomposites on the base of polystyrene, polymethylmethacrylate, and polycarbonate with alumina and SiO2 nanoparticles and carbon nanotubes have been studied. Miniaturized, microdimensional samples were used, enabling a good control of morphology and distribution of particles by means of transmission and scanning electr...

Three approaches towards a fracture theory are discussed, namely the statistical, the continuum-mechanical, and the micro-morphological approach. The latter recognizes that (amorphous or semicrystalline) high-polymer solids are composed of chain molecules which show a close range order and/or a superstructure. Information from morphological and spe...

The motion of whole chains or of parts thereof fundamentally influences the rheological and the mechanical properties of liquid and solid polymers. In this contribution different forms of interaction between a moving chain and a moving environment are discussed. Depending on the experimental and on the molecular time scales (where the latter is ess...

In thin amorphous polymer films, the entanglement density, ve, strongly influences the draw ratio during micronecking and the competition between cavitational and non-cavitational processes, often referred to as crazing and shear deformation respectively. TEM investigations suggest this also to be true of polymers capable of crystallizing, although...

The deformation processes in crystalline polymers have been studie ever since the discovery of chain folding in 1957. Since then, scientists have been intrigued by the different steps of the transformation of the folded-chain lamellar structure of single crystals or of macroscopically isotropic, often spherulitic, polymers into fibrous morphologies...

It has been known for more than 20 years that, in crazes of polystyrene (PS), the craze fibrils show a very high ductility with elongations at break up to 300%. Later, a similarly high ductility was found in laminated multilayer tapes and in styren-butadiene-styrene (SBS) block copolymers with an arrangement of very tiny PS lamellae. In both cases...

Polymer molecules respond to the application of stress by disentanglement, chain orientation and bond rupture. Being the last step in this series of events, the efficiency of flow-induced mechanochemical degradation depends markedly on the details of the pervading flow field. From the results of fluid mechanics, it is usual to distinguish degradati...

By way of introduction to the subject of this Volume1 this contribution reviews the effects of the most prominent properties of macromolecules (their enormous length, strong elastic anisotropy in axial and lateral directions and high segmental mobility) and of their characteristic dimensions on the elementary molecular deformation mechanisms of the...

This paper deals with the mechanical properties (plastic deformation, micromechanism of deformation, fracture) of various amorphous polymers: poly(methyl methacrylate) and its maleimide and glutarimide copolymers, bisphenolA (and/or tetramethyl bisphenolA) polycarbonate, and aryl-aliphatic copolyamides. First, the required background on molecular c...

Degradation can result from a variety of chemical, physical and mechanical mechanisms, most of them involving a reduction of molecular weight and thus a decrease in the mechanical performance of the degraded polymer. A clear understanding and control of these mechanisms is absolutely essential: without stabilization some polymers (e.g. PVC, polyole...

In this paper, a review of the molecular aspects of fracture is given, a subject that was pioneered by S. N. Zhurkov and his colleagues. Particular attention will be paid to the mechanisms of stress transfer onto straight chain segments, the role of chain interpenetration in establishing interfacial strength during crack healing, to the concept of...

In this introductory lecture a brief review is given first on the mechanical problems, which derive from the existence and the large variety of interfaces in thermoplastic polymers, taking into account their specific organization and the particularities of the geometry of stress and strain. Then (fracture mechanics) methods are discussed to determi...

The influence of the primary molecular parameters chain configuration, architecture and molecular weight (MW) on the mode of mechanical breakdown is discussed for two series of (amorphous) thermoplastic polymers, methyl methacrylate glutarimide copolymers and amorphous semi-aromatic polyamides. Structural and dynamic analyses and fracture mechanica...

Recent investigations of the tensile fracture behaviour of representative glassy and semicrystalline impact-resistant polymers are reviewed, with emphasis on the microdeformation behaviour as revealed by electron microscopy of sections from bulk specimens, where the crack-tip damage zone has been embedded and/or stained under load, and on thin film...

Toughness quantification of polymers is still an open issue, since no unique fracture mechanics method is able to provide intrinsic crack propagation resistance values over the whole range of material behaviours from brittle to ductile. A sensitive way to characterise the mechanical performance of these materials, exemplified with rubber modified i...

Toughness assessment of ductile polymers is still an open issue, especially at high loading rates, the main challenge being to measure intrinsic values. An original approach derived from linear elastic fracture mechanics (LEFM) is presented. It consists of determining experimentally the size of the plastic zone developed at the vicinity of the crac...

Raman microscopy is applied to a gel-spun UHMWPE-fibre (Dyneema SK60) to determine the distribution of axial molecular stresses and their change with time (in creep and during stress relaxation). A more detailed method is proposed to quantify the observed characteristic changes in local stress distribution. The increase in highly overstressed bonds...

The load transmission through macromolecules is determined by the nature and the rate of their external interaction with the surroundings and by internal relaxation mechanisms. The time scales for the orientation, disentanglement, and scission of chains in elongational flows, polymer melts, and solids will be discussed in this paper. Die durch ein...

An expression of the kinetics describing the rate of bond scission under stress is proposed and applied to the case of degradation of polymers in transient elongational flow. The new equation permits to take into account the existence of critical values, either for molecular weight or strainrate, below which no chain scission occurs. Compared with...

Optical and transmission electron microscopy have been used to investigate the microdeformation mechanisms in thin films of amorphous semi-aromatic polyamides with different chemical structures and chain lengths. In the chosen range of test temperatures (between 2120 8C and the principal mechanical relaxation temperature, Ta), three successive micr...

Biomaterials repair, reinforce or replace damaged functional parts of the (human) body. All mechanical and biological interactions between an implant and the body occur across the interface, which has to correspond as nearly as possible to its particular function. Much of the progress in adapting polymer materials for use in a biological environmen...

The mechanical properties of extruded films of isotactic polypropylene (iPP) and ethylene-propylene rubber toughened iPP (iPP/EPR) have been analyzed in terms of the specific essential and non-essential work of fracture using high speed tensile test apparatus modified for quasi-static testing in the range 0.0001 to 3 ms.1. Three iPP/EPR grades with...

The tensile and fracture behaviour of neat α and β nucleated isotactic polypropylene and rubber-modified α and β nucleated isotactic polypropylene has been investigated at test speeds of 0.0001–10 ms−1 in the temperature range −30 to +60 °C. The presence of the β phase had little effect at low temperature. However, at +25 and +60 °C, it increased t...

The sub-T-g relaxations of Bisphenol-A polycarbonate (BPA-PC) can be selectively altered by appropriate chemical modification. It is established that these secondary relaxations are responsible for the in-chain cooperative motions of BPA-PC and have profound effects on the deformation behavior of the bulk material. Through investigations of the mic...

This contribution reviews the phenomenology of fracture in low Tg semicrystalline homopolymers with emphasis on the influence of molecular and morphological parameters on the underlying microdeformation mechanisms, and the transitions from macroscopically ductile to brittle fracture as the loading conditions are varied. Particular attention is give...

Fracture of polymers is defined, and the essential phenomena of stable and unstable crack propagation are described and quantified using different concepts of fracture mechanics (linear elastic, confined plasticity, essential work of fracture). Particular attention has been given to a discussion of toughness and time-dependent strength in terms of...

As fillers are traditionally designated those finely divided solids which are added to a polymer matrix in relativly large amounts to modify its properties and/or to reduce the price of the resulting compound. Generally a filler material is stiffer than the matrix and depending on their origin, shape and treatment fillers are reinforcing or not. In...

To establish whether coronary perfusion with cardioplegic solutions results in better intraischaemic structural preservation of endothelial cells than of cardiomyocytes, we determined intraischaemic swelling of these two cell types in hearts differently arrested during global ischaemia at 5 degrees C. Cardiac arrest was induced in situ by aortic cr...

The controlled synthesis of low molecular weight (Mn from 700 to 10 000 g/mol) poly(lactic acid) (PLA) telechelic oligomers end-capped with acrylate groups by a one-step reaction was investigated. A transesterification reaction was carried out in solution with a Lewis acid titanium catalyst using a high molecular weight PLA and a low molar mass dia...

Brittle failure has been observed in polyoxymethylene during long-term low-level tensile loading at elevated temperatures. It is argued to be associated with slow crack growth via the breakdown of the localized planar fibrillar damage zones that form under these conditions. This phenomenon has been characterized using notched compact tension specim...

The fracture behaviour of an isotactic polypropylene and an impact modified isotactic polypropylene containing 15 wt% of ethylene–propylene rubber has been investigated at test speeds of between 0.1 mm/s and 14 m/s, using compact-tension specimens. The homopolymer displayed a ductile–brittle transition as the test speed was increased, which was ass...

Tensile testing of plain-weave-cloth-reinforced polyamide composites has been carried out at various strain rates ranging from 1×10−2 to 4×101 s−1 in a servohydraulic testing apparatus. Four different polyamide composites studied were composed of two kinds of reinforcements, carbon fibre (CF) and glass fibre (GF), and two kinds of matrices, polyami...

Essential Work of Fracture (EWF) tests have been carried out on double edge notched samples machined from injection molded sheets of commercial grades of polyoxymethylene homopolymer with different molecular weight averages. Most of the measurements were made at 1000C and over a range of test speeds in which polyoxymethylene is anticipated to under...

The influence of a phenolic antioxidant and two hindered amine stabilizers (HAS) on the degradation behaviour of isotactic polypropylene was investigated for temperatures in the range 120–149°C. Consistent with earlier reports, phenolic-stabilized specimens were found to decompose in a catastrophic manner at the end of an induction period, whereas...

In this presentation, a review is given on the main effects of mineral particulate fillers (with an aspect ratio of about unity) on the deformation and fracture of amorphous and semicrystalline thermoplastic and thermosetting polymers. Elastomeric modifiers, polymer blends, and filled elastomers are not considered here. Fillers are generally used t...

In open heart surgery and transplantation, sufficient structural preservation of the myocardium immediately following cardioplegic arrest is a precondition for overcoming ischemia and for resumption of postischemic function. Therefore, we compared the protective effect of three clinically applied cardioplegic solutions with fibrillating and beating...

Un materiau durable est un materiau qui peut fiablement servir longtemps. Cette definition implique les notions de temps, d'endommagement et de resistance contre les agressions environnementales. Dans cette presentation, nous discutons du comportement mecanique du polypropylene stabilise et vieilli. En utilisant diverses methodes de caracterisation...

We have investigated the microdeformation mechanisms in thin films and bulk samples of impact-modified PMMA over a range of experimental conditions by TEM. The extent of cavitation of the modifier particles and the competition between crazing and simple shear deformation are discussed, as well as the extent to which the thin film behaviour is repre...

The viscoelastic response of a chopped strand mat E-glass fibre reinforced vinylester resin has been studied over a wide range of applied stress levels. At low applied stress levels, the material exhibited a linear viscoelastic response well represented by Schapery''s power law model with constant C and n terms. At higher stresses nonlinear behavio...

Mode I fracture behavior of rubber toughened PMMA (RT-PMMA) was studied over five decades of displacement rates (10-4-13 m/s) using a high speed tensile testing machine. Two kinds of RT-PMMA, extruded RT-PMMA containing 20 wt.% rubber particles (EM20) and pressed RT-PMMA containing 40 wt.% rubber particles (PM40), exhibited different rate dependenc...

After the chemical structure, the polymer chain length and its distribution are undoubtedly the next most important molecular parameters controlling the physical, mechanical and processing properties of plastic materials. Change in material properties with increasing molecular weight (MW) without a change in chemical composition is well-exemplified...

The MWD is probably the single most fundamental property of a polymer (see Molecular Weight Distribution and Mechanical Properties). Depending on the application, MW of polymer materials can encompass an extremely large range extending from several hundreds (paints, coatings, functionalised polymers) to a few million daltons (UHMWPE, high performan...

Flexible Polymer Chain Dynamics in Elongational Flow fulfills a need by presenting the most important advances in the field of flexible polymer chains in "strong" flow in a single literature source. Although several excellent treatises on polymer dynamics have appeared over the years, most of them deal with polymer chains in the quiescent state or...

The influence of molecular weight on the mechanical properties of isotactic poly(propylene) (iPP) and iPP blended with ethylene-propylene copolymers has been investigated by means of the microhardness technique. The hardness (H) of iPP is shown to slightly decrease with increasing molecular mass, within the range of molecular weights investigated....

Molecular weight distribution obtained by gel permeation chromatography (GPC) conceals a wealth of mechanistic information which can be disclosed only after adequate data treatment. This paper discusses how GPC chromatograms may be used for the elucidation of polymer degradation kinetics. The case of ultrasonic degradation of dilute polystyrene sol...

Transmission electron microscopy has been used in conjunction with RuO4 staining to investigate the structure of (iPP/iPP-g-MA)−PA6 reaction bonded interfaces and microdeformation at interfaces which had failed by crack propagation along the interface. In relatively weak interfaces, the crack tip was preceded by a single, well-defined crazelike fib...

A zero-order model is presented, which allows calculation of the stress distribution in porous epoxies by taking into account the interaction between randomly distributed voids. These results demonstrate that the mean value of the stress concentration factor increases with the volume fraction of voids. This leads to a decrease in sample yield stren...

Transient elongational flow, created by forcing a polymer solution across a narrow contraction, is characterized by a high strain rate of limited duration. Due to an inherent short residence time, this type of flow generally is considered as being less efficient in extending isolated flexible molecular coils than “stagnation” point elongational flo...

The electrical conductivity of polymer resins containing gold and silver particulate fillers has been investigated as a function of the particle content. At the same time, an apparatus constructed in-house has permitted measurement of the conductance between two isolated filler particles in the presence of an epoxy or polyester resin undergoing cur...

Segmental orientation of anthracene-labelled polystyrene chains dissolved in DOP was studied in opposed-jet flow with a new rheooptical technique, "polarization-modulated fluorescence depolarization". The method relies on a high-speed phase modulated incident UV-laser beam to excite the chromophore. Experiments were analyzed with Jones-Mueller matr...

Flow birefringence of dilute polystyrene solutions was studied in opposed-jet flow with a polarization-modulated optical polarimeter. Change in flow character from "quasi-steady" to "transient" elongational flow, was achieved by adjusting the jet separation distance between 0.3=B7d and 3=B7d = (d =3D orifice diameter, 500 =B5m). Birefringence profi...

The electrical contact resistance between isolated pairs of micron-sized gold particles has been measured as a function of their separation using apparatus constructed in house. When incorporated into a percolation model for current transport in a conducting particle filled insulator, the results of such measurements have been shown to be consisten...

Compact tension specimens were loaded at 1 and 7 m/s with two different accelerations imposed. Experimental photoelastic patterns recorded by a high speed camera were compared with those simulated by transient dynamic elastic Finite Element (F.E.) analysis. The positive results of this comparison validated the F.E. analysis, and gave credit to a co...

A brief review is given of the relative importance of parameters determining the long time behaviour of thermoplastics (chain topology and mobility, sample morphology, physical and chemical aging, creep deformation). An example is then given, namely results from a study of the response of polyoxymethylene (POM) to static and dynamic load conditions...

Melt crystallized isotactic polypropylene thin films of thickness between 30 and 100 nm have been investigated by high-resolution transmission electron microscopy at room temperature. The c-axis projection of the 2*31 helices and their packing in the lattice were clearly visible in flat-on lamellae of the α-phase following reconstruction from the c...

Abstract The study of time dependent crack growth in polymers using a fracture mechanics approach has been reviewed. The time dependence of crack growth in polymers is seen to be the result of the viscoelastic deformation in the process zone, which causes the supply of energy to drive the crack to occur over time rather than instantaneously, as it...

Compact Tension specimens were loaded at 1 and 7 m/s with two different accelerations imposed. Experimental photoelastic patterns recorded by a high speed camera were compared with those simulated by dynamic elastic Finite Element (FE) analysis. The positive results of this comparison validated the FE analysis. It is demonstrated that when the init...

The tensile and fracture properties of rubber toughened poly(methylmethacrylate) (rtPMMA) modified by spherical core-shell particles, and poly(urethane)/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer networks (IPN) are investigated at different strain rates. The deformation and fracture mechanisms are studied by transmission electron...

The kinetics of ultrasonic degradation has been investigated for dilute polystyrene solutions in decalin. The increase in the scission rate constant (K) with initial molecular chain length was systematically investigated over 2 decades of molecular weight by using narrow polymer fractions with M = 50 × 103 − 8.5 × 106Da. An empirical relation of th...

The deformation behaviour of amorphous thin films of poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends was investigated over a wide temperature range by optical and transmission electron microscopy. All the materials showed localized shear deformation at temperatures well below Tg. In pure PEI and in blends with up to 60 wt% PEEK conte...

Epoxy systems EPN/BA and EPN/DDS having significantly different cross-link densities have been modified using core–shell rubber particles. The toughening mechanisms have been investigated and the results show that cavitation and particle–matrix debonding play different roles in the low and high cross-link density epoxy resins.

The fracture toughness has been investigated with single edge notched bending specimens in solvent-modified epoxies, which were prepared via the Chemically Induced Phase Separation technique. The generation of a controlled morphology with liquid droplets in the micrometer range leads to a substantial increase in the fracture energy of nearly 400% c...

Transient elongational flow was created by forcing a polymer solution across a narrow contraction. Rheo-optical measurements revealed a localized birefringence zone above a critical strain-rate in the immediate orifice entrance. Birefringence was studied for dilute PS solutions (50-500ppm) as a function of fluid strain-rate (1000-38000/s) and polym...

Solution cast thin films of the VectraRM HBA-HNA thermotropic liquid crystalline random copolymer, annealed for 1 h at 240°C have been investigated by HREM. Non-periodic layer crystals were observed with the c∗ direction lying in, or close to the plane of the films, with crystalline core widths of about 10 nm. Lattice fringes werre obtained from th...

Free standing thin films of poly(ether ether ketone) crystallized in situ by heating from the glassy state have been shown to be suitable for high resolution transmission electron microscopy lattice imaging. Films mounted on coarse-mesh copper grids could also be observed in the deformed state, allowing lattice imaging of regions of strain induced...

Oriented films of PTFE, UHMWPE and Vectra, TM prepared by friction transfer, have been investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the results have been compared. These techniques can provide molecular resolution of the internal structure and the sample surface respectively, with certain limitati...

A finite element model is used to compute the dynamic stress intensity factor (S.I.F.) during rapid crack propagation. It is shown that the inertial effects in a transient dynamic linear elastic analysis for an accelerating and decelerating crack can be responsible for the non uniqueness of the S.I.F. at a given crack speed.

Microdeformation in thin films of rubber modified poly(methyl methacrylate) has been investigated using TEM. The effects of two-layer core—shell particles with rubbery cores, and three-layer particles with glassy cores are compared. While the former undergo relatively coarse cavitation and may act to block fibril drawing in matrix crazes, the rubbe...

We have prepared triblock copolymers of poly(phenylene oxide) (PPO) and polysulphone (PSF) of the form PPO–PSF–PPO in order to assess their intrinsic mechanical properties and their potential as interfacial compatibilizers in polystyrene/PSF blends. For sufficiently long polysulphone block lengths, we observed microphase separation both in the trib...

Rubber toughened Styrenics represent an interesting model system for a blend containing a soft second phase in the form of dispersed spherical particles. The elastic properties of such a system have been widely examined in the past, both from experimental and theoretical viewpoints, however some questions remain unanswered. In this work an attempt...

Crack-tip deformation has been investigated in pre-cracked samples of core-shell rubber particle modified epoxy resins with different degrees of crosslinking. Light cross linking resulted in cavitation of the modifier, the formation of croids and extensive crack-tip yielding, whereas these deformation mechanisms were suppressed at room T in highly...

Highly oriented poly(tetrafluoroethylene) (PTFE) films were obtained by sliding a bar of a commercial grade PTFE along a strip of mica at a temperature of 300C. High resolution transmission electron microscopy was used to image the 1010 lattice planes of the hexagonal phase IV in suitably oriented regions of the sample, indicating coherent order ov...

Birefringence measurements are reported in transient and stagnation point elongational flows created by forcing a polymer solution through a narrow contraction. A strongly molecular weight dependent birefringence was observed and attributed to segmental orientation caused by individual chain extension. The birefringence was also found to depend on...

Models for the dynamics of dilute polymer solutions under elongational flow have been examined in the light of new experimental data. In particular birefringence measurements on the polystyrene-decalin and poly(ethylene oxide)—water systems in both stagnation point and transient elongational flows are the most revealing as to the nature of polymer...

The bulk tensile behaviour of poly(ether ether ketone) and poly(ether imide) homopolymers and their blends has been investigated, and the temperature and strain rate dependence of the yield stress discussed in terms of simple Eyring rate theory. In fracture mechanics tests, the KIC of PEEK was found to decrease significantly with increasing test sp...

Transmission electron microscopy and optical studies of thin films of isotactic polystyrene (iPS) and polyoxymethylene (POM) provide evidence for a distinction between crazing mechanisms in semicrystalline polymers above and below Tg. In the latter temperature regime, deformation in iPS and POM crystallized at high supercooling has been discussed i...

Thin melt crystallized spherulitic films of isotactic polypropylene have been deformed in uniaxial tension at different temperatures and examined by transmission electron microscopy. As the temperature was increased above approximately −80°C, a transition from high aspect ratio craze-like features to highly voided shear deformation zones was observ...

Routine MW analysis of polymers is generally performed in solution by Gel Permeation Chromatography. The technique, however, presents increasing difficulties in the ultra-high and ultra-low MW range. Moreover, GPC is not applicable to most fluorinated and»high performance«thermoplastics which require dissolution temperatures close to the polymer me...

The fracture behavior of neat and rubber-toughened poly(methyl methacnjlate) (PMMA) was investigated at room temperature over five decades of testing velocities (from J(H to 14 m/s). The toughened PMMA materials underwent three successive transitions, whereas the neat material remained brittle over the entire range of testing velocities. The transi...

Biomer is generally processed by repeated deposition of layers by solution casting onto a preshaped former. The precise nature of this processing route may influence the mechanical response and surface properties of the finished article and, as a result, its subsequent in vivo behaviour. Here we have studied the influence of a range of processing p...

High impact polystyrene (HIPS) particles with sizes well below 1 μm have been demonstrated to interact with growing crazes giving rise to some local, non-catastrophic fibril texture damage, which increases with increasing particle size and volume fraction of the second phase. The influence of such damage on the sub-critical fracture behaviour of so...

We have investigated the influence of scanning rate on the form of DSC melting curves in semicrystalline polymers in which the melting point varies spatially within the sample. A numerical solution for the heat balance in the sample cell was used, taking into account heat absorbed during the melting transition for a given sample mass. The simulatio...