Ralf Lach

Martin Luther University Halle-Wittenberg | MLU · Department of Polymer Testing and Diagnostics

For the investigations, scaffolds for bone regeneration (in the form of non-woven mats) were fabricated based on a polymer blend based on polycaprolactone, poly-L-lactic acid and gelatin by electrospinning which were partly modified using vitamin D3 and reinforced with 0 – 12 % nano-hydroxyapatite (nano-HAp extracted from ostrich bones) to improve...

Multi-walled carbon nanotubes and graphite nanoplatelets were functionalized via acid treatment to overcome the problem of agglomeration. Fourier transform infrared spectroscopy showed the chemical modification of the nanocarbons while the general relationship between the chemical treatment and the defects population was analyzed by Raman spectrosc...

Structural, mechanical, thermal and surface properties comprising biodegradable aromatic–aliphatic polymer poly(butylene adipate-co-terephthalate) (PBAT) and the wheat stalk-based nanocellulose (NCC) were studied. The materials were found to comprise the compatible and yet phase-segregated constituents which kept their identity in the nanocomposite...

Plastic components subjected to a constant load, such as pipes or load‐bearing structures in motor vehicles, tend to creep and show increased deformation over time. In special applications for example coolant expansion tanks, increased temperatures and media also affect the long‐term creep behavior. In this study, the influence of media–thermal agi...

For bone tissue engineering, nano‐hydroxyapatite (nano‐HAp) is a widely used bioceramic filler in polymer fibrous scaffolds that changes the morphology and micromechanical behavior of fibers. In this study, different volume fraction percentages of nano‐HAp and vitamin D3 (VD3) are incorporated into electrospun polymer blend fibrous scaffolds compri...

The morphology and mechanical properties of solution‐cast poly(butyl methacrylate)–polystyrene (PBMA–PS) diblock copolymer films (Mn = 270 kg mol−1, 70 Vol.‐% PS) prepared by using different solvents (cyclohexane, toluene, chloroform, and dioxane) are investigated in this study. All solvents except dioxane, which leads to PBMA cylinders in the PS m...

Nanocomposites of multiwalled carbon nanotubes (MWCNTs) with poly(butylene adipate-co-terephthalate) (PBAT), a flexible aromatic–aliphatic copolyester, were prepared by melt mixing followed by compression moulding to investigate their spectroscopic, morphological, mechanical and electrical properties. A comparison of the Fourier transform infrared...

Rapid manufacturing of individualized products made from plastics using 3D printing technologies will now become a highly growing market. However, the influence of morphology and processing parameters (such as speed of printing and screen angle) on the fracture mechanics performance of such additively produced materials is still inadequately invest...

Structural, thermal and mechanical properties of the compostable composites comprising a biodegradable aliphatic-aromatic copolyester (namely, the poly(butylene adipate-co-terephthalate; PBAT), and microcrystalline cellulose (MCC) derived from agricultural waste, the wheat stalk, were investigated. Purely physical interaction between the components...

Nanocomposites of poly(lactic acid) (PLA)/poly(butylene adipate‐co‐terephthalate) (PBAT) blends with multiwalled carbon nanotubes (MWCNTs) were prepared and their morphology, as well as electrical, mechanical, and thermal properties were investigated. The motivation of this work is to prepare electrically conductive and environmentally benign polym...

Abstracts of the international conference "Polymertec 2021 digital" (09-11 June 2021, Merseburg/Germany).

A new type of ionomeric nanocomposite based on elastomeric ethylene/1-octene copolymer (EOC) and organophilically modified layered silicate was synthesized through sulfonation of the EOC followed by solution casting. The morphology-mechanical properties correlation of the product was studied with the help of scanning electron microscopy (SEM), atom...

The object of this study has been to investigate the effect of filler dimensionality on morphology and mechanical properties of polymer nanocomposites using various kinds of nanofillers (such as multiwalled carbon nanotubes (1D filler), layered silicate (2D filler), and boehmite (3D filler)) dispersed in the matrix of ethylene-1-octene copolymer (E...

ABSTRACT Starch was extracted from potato (Solanum tuberosum) cultivated in Nepal. The yield of starch of different sorts of the species S. tuberosum was compared with each other. Extracted starch (E St.) Kufre Sindure was characterized and compared with commercial starch (Com St.) by the Fourier transform infrared spectroscopy (FTIR). The properti...

Further developed methods based on an indenter penetration into a material allow generalised quantitative statements on the composition, the depth-dependent mechanical properties and the delamination behaviour of multilayer polymer films, which is demonstrated on gelatine-coated polyethylene terephthalate and polyethylene films. These highly sensit...

Star-shaped polystyrene-block-polybutadiene-block-polystyrene (SBS) block copolymer (BCP) was subjected to epoxidation reaction using m-chloroperoxy benzoic acid (MCPBA). The epoxidized SBS block copolymer (eSBS) was then blended with diglycidyl ether of bisphenol-A based epoxy resin (EP) and cross-linked with methylene dianiline (MDA). The materia...

Present work explains the synthesis of urea–formaldehyde composites with Allo (Girardinia diversifolia) and cotton (Gossypium arboreum) fibers. Urea–formaldehyde resin was synthesized by condensation polymerization of urea and formaldehyde monomers. Cellulose fibers were extracted by various chemical treatments of natural fibers. Composites were pr...

An agricultural waste, the wheat stalk, was used for the extraction of microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) via a series of thermochemical and mechanical treatments. The MCC and NCC were then compounded with the biodegradable polymer, poly(butylene adipate‐co‐terephthalate), PBAT, by melt mixing. The properties of th...

An accelerated approach to assess the long‐term performance of biodegradable agriculture films such as mulch films based on poly(butyrate adipate terephthalate) (PBAT) is presented. PBAT films were aged in water and in air at 80 °C for different times and morphological changes were analysed using Fourier‐transform infrared spectroscopy and light mi...

Applying dynamic fracture mechanics, a simple analytical model for the evolution of the crack propagation velocity during unstable crack growth has been developed. Based on the energy balance concept, rarely used in dynamic fracture mechanics, this model allows the estimation of the crack growth energy and the process zone size to be 1.2 J at break...

The 2018 international scientific conference PolyMerTec was held, together with the 16th meeting “Deformation and Fracture Behaviour of Polymers”, in Merseburg for the third time. First of all, the guest editors of this issue of Macromolecular Symposia would like to express their gratitude to all the esteemed participants, the enthusiastic organisi...

The work aims at establishing the optimum conditions for dual thermal and electron beam curing of thermosetting systems modified by styrene/butadiene (SB)-based triblock copolymers in order to develop transparent and toughened materials. The work also investigates the effects of curing procedures on the ultimate phase morphology and mechanical prop...

p>Micro- and nanocrystalline cellulose were extracted from wheat stalk (WS) using different thermomechanical and chemical treatments and characterized by spectroscopic, microscopic and diffraction techniques. The virgin WS fibers were found to be structurally quite similar to the commercial microcrystalline cellulose (MCC). Similar to the commercia...

Micro-and nanocrystalline cellulose were extracted from wheat stalk (WS) using different thermomechanical and chemical treatments and characterized by spectroscopic, microscopic and diffraction techniques. The virgin WS fibers were found to be structurally quite similar to the commercial microcrystalline cellulose (MCC). Similar to the commercial o...

p>We investigate the ways of improving thermal and mechanical properties of diglycidyl ether of bisphenol-A (DGEBA) based thermoset resin using diaminodiphenylsulphone (DDS) as hardener and using epoxidized polystyrene/polybutadiene-based triblock copolymers as modifier. The epoxidation was performed. The targeted chemical modification using meta -...

Conventional methods for testing the long‐term resistance against creep and slow crack growth (SCG) become more and more unusable for highly improved polymers due to the required long times of often more than 1 year. Therefore, there is a great need for developing new time‐saving methods for predicting the lifetime of such polymers. In this study,...

Compared to other methods of fatigue testing which are in need of expensive testing machines and often highly time-consuming, the developed rolling ring tester is cost-effective, easily to handle and allows relatively fast data acquisition. Within only a few days essential information for fast quality assurance of laser-sintered parts are available...

In this work, we investigate the morphological and mechanical properties of blends of diglycidyl ether of bisphenol-A (DGEBA) and epoxidized polystyrene–polybutadiene star block copolymer (epST3) using diamino-diphenyl sulphone (DDS) as a hardener. The epoxidation of the star block copolymer was performed using meta-chloroperoxybenzoic acid (m-CPBA...

The overall stable crack initiation and propagation behaviour of fracture mechanics specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of elastic–plastic fracture mechanics including the crack propagation kinetics. The effect of specimen shape, orientation, welding and lading rate...

Based on the crack resistance (R) concept of elastic fracture mechanics the crack propagation kinetics at impact and quasi-static loading conditions was analysed both from the experimental and analytical point of view. For blends composed of polyurethane (TPU) and an acrylonitrile–butadiene–styrene copolymer (ABS), it has been shown that the stop b...

Pipe failure in long-term applications is characterised by creep crack initiation and creep crack growth. Both can be determined by fracture mechanics-based tests of the pipe materials. Nowadays, several accelerated tests are available: PENT (Pennsylvania Edge Notch Tensile Test), FNCT (Full Notch Creep Tensile Test), CRB (Cracked Round Bar Test) o...

The main aim of the paper is to study the influence of both material inhomogeneity and weld bead geometry on crack propagation in welded polyolefin pipes. Lifetime of three pipes welded by different welding procedures is numerically estimated. Experimentally observed shapes of weld bead and change of material properties inside the welded region (th...

Polymeric stretch films are wrapped around a packaging unit to keep it bundled and safe for transportation and storage. To maintain the generated retention forces and prevent a peel-off of the film, adhesive interactions between the film layers are required. Fracture mechanics investigations have been done in order to characterise the autohesive (c...

Sulphur-crosslinked styrene–butadiene vulcanizate filled with carbon black up to 50 parts per hundred rubber (phr) were mainly investigating using an instrumented impact tensile tester. The experimentally determined and the calculated critical J-values are in a good agreement. The pronounced energy dissipation capability of the vulcanizate with 50...

Based on results of atomic force microscopy and dynamic mechanical analysis applied on binary blends of polystyrene (PS)–poly­butadiene (PB) star block copolymers (ST3) having different compositions, a three-phase morphology that comprises PB-rich, PS/PB-mixed and PS-rich phase has been found. The pronounced enhancement of toughness in blends with...

The Stepped Isothermal Method (SIM) is a relatively new method for accelerated determination of the creep behaviour of polymers. The need for such a new method arises from the fact that for modern plastic components such as pipe systems minimum lifetimes of 50 years and more are achieved. The analysis of creep applying conventional methods of testi...

The plastic constraint factor based on Hill's theory of plasticity is widely used to check the stress state applying the essential-work-of-fracture (EWF) approach to polymers. However, the plastic constraint factor experimentally determined as the ratio of the net section stress in cracked specimens and the yield stress does not match the theoretic...

The mixed mode brittle fracture (mode I/mode II) of poly(methyl methacrylate) (PMMA) was investigated using single-edge notched tensile (SENT) specimens by applying a mixed mode special loading device which allows varying the loading angle from 0° (pure mode I) to 90° (pure mode II). The experimental results dealing with mixed mode fracture toughne...

The overall stable crack initiation and propagation behaviour of specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of elastic–plastic fracture mechanics including the crack propagation kinetics. The effect of specimen shape, orientation, welding, lading rate, composition/microstru...

The prototype of a depth-sensing macrohardness testing system with temperature chamber and temperature controlling unit for contact heating/cooling was upgraded in terms of control and software in such a way, that it allows application of the Stepped Isothermal Method (SIM) as for now. The SIM is a single-specimen method, for which the temperature...

Chitosan was prepared from shells of locally available fresh water prawns with variation of sodium hydroxide concentration and reaction time. The biopolymer was melt-mixed with a commercially available biodegradable polymer, the poly(butylene adipate-co-terephthalate) (PBAT). The chitosan and blend films were characterized by Fourier transform infr...

Chitin was prepared from prawn shells waste by chemical treatments viz. demineralization, deproteinization and decolorization. Chitosan was prepared by deacetylation of chitin with 50% NaOH at 100 °C in the presence of nitrogen. Deacetylation was performed at different intervals of time to get a series of chitosans having different degrees of deace...

The main aim of the paper is to study the influence of both material inhomogeneity and weld bead geometry on crack propagation in welded polyolefin pipes. Axially and circumferentially oriented cracks are studied and the stress intensity factors are compared considering different positions of the cracks. Two cases of the welded pipe system are comp...

In this work, model structures coextruded from polyolefin materials with different resistance against elastic and plastic deforma- tion (tensile modulus and work of deformation up to the yield point) as well as different resistance against stable crack initiation and propagation were experimentally analyzed using the multiple-specimen crack resista...

The short-term performance (Martens hardness and indentation modulus) and the time-dependent creep behavior of polyamide 6 (PA 6) and two PA 6 nanocomposites containing 3.5 wt % montmorillonite (MMT) or 5 wt % halloysite nanotubes (HNT) were analyzed by different depth-sensing indentation techniques in the nano-, micro- and macro-range of loading a...

A star shaped polystyrene-block-polybutadiene-block-polystyrene (SBS) block copolymer was subjected to epoxidation reaction using different reagents such as m-chloroperoxy benzoic acid (MCPBA), peracetic acid (PAA), performic acid (PFA) and hexaflouro-isopropanol (HFIP). All the methods led to the targeted modification of the block copolymer satisf...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Description of Properties. Parent documents: SpringerMaterial s home Volume VIII/ 6A3

The paper presents a methodology for the lifetime assessment of welded polymer pipes. A fracture mechanics analysis of a butt-welded joint is performed by simulating radial crack growth in the nonhomogenous region of the pipe weld. It was found that the presence of material nonhomogeneity in the pipe weld caused by the welding procedure leads to an...

The short-term performance (Martens hardness and indentation modulus) and the time-dependent creep behavior of polyamide 6 (PA 6) and two PA 6 nanocomposites containing 3.5 wt % montmorillonite (MMT) or 5 wt % halloysite nanotubes (HNT) were analyzed by different depth-sensing indentation techniques in the nano-, micro- and macro-range of loading a...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Impact Loading of Thermosets and High Performance Composites - Data. Parent documents: SpringerMateria...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance (Fracture Mechanic Method) - Data. Parent documents: SpringerMaterial s hom...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance – introduction. Parent documents: SpringerMaterial s home Volume VIII/ 6A3

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance (Fracture Mechanic Method) - Application. Parent documents: SpringerMateria...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance (Constant Tensile Load) – data. Parent documents: SpringerMaterial s home V...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Quasi-Static Loading of Thermoplastics - Data. Parent documents: SpringerMaterial s home Volume VIII/...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance (Bent Strip Method)–Data. Parent documents: SpringerMaterial s home Volume...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Stress Cracking Resistance (Constant Tensile Load) – Application. Parent documents: SpringerMaterial s...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Quasi-Static Loading of Thermosets and High Performance Composites - Data I. Parent documents: Springe...

This document is part of part 3 'Mechanical and Thermodynamical Properties of Polymers' of Subvolume A 'Polymer Solids and Polymer Melts' of Volume 6 'Polymers' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It deals with Quasi-static loading – Energy determined Parameters - data. Parent documents: SpringerMaterial s home...

The authors introduce a prototype of a recording (depth-sensing) macroindentation testing machine that has been modified and extended with a temperature chamber. This prototype allows the analysis of different hardness values (Martens hardness, indentation hardness, ball indentation hardness, etc.) and the indentation modulus, as well as time-depen...

The paper summarizes our investigations performed with micro- and nanoindentation techniques and results presented in literature, concerning local mechanical behavior of welded joints [polyamide 6, polypropylene, polyethylene (high density and crosslinked polyethylene), poly(vinyl chloride)] and weld lines (polypropylene, polycarbonate, polystyrene...

Instrumented scratch test was carried out to determine the scratch resistance of polyamide 6 (PA 6) nanocomposites, where two kinds of nanofillers were tested, both based on silicates: montmorillonite (MMT) and halloysite nanotubes (HNT). In this work the influence of the sliding velocity, normal applied load and time-dependent recovery on the pene...

Recent research has shown that the resistance against crack initiation and propagation of polyethylene blown films depends on density, chain branching and crystal orientation next to the processing parameters. To assess low-density polyethylene blown film fracture toughness with different thicknesses, the essential work of fracture method has been...

A new type of ionomeric nanocomposite based on elastomeric ethylene/1-octene copolymer (EOC) and organophilically modified layered silicate was synthesized through sulfonation of the EOC followed by solution casting. The morphology–mechanical properties correlation of the product was studied with the help of scanning electron microscopy (SEM), atom...

The object of this study has been to investigate the effect of filler dimensionality on morphology and mechanical properties of polymer nanocomposites using various kinds of nanofillers (such as multiwalled carbon nanotubes (1D filler), layered silicate (2D filler), and boehmite (3D filler)) dispersed in the matrix of ethylene-1-octene copolymer (E...

Scratch test was carried out to determine the scratch resistance of PA6 nanocomposites, where two kinds of nanofillers were tested, both based on silicates: montmorillonite (MMT) and halloysite nanotubes (HNT). In this work the influence of the sliding velocity, normal applied load and time-dependent recovery on the penetration depth and scratch ha...

The object of this study has been to investigate the effect of filler dimensionality on morphology and mechanical properties of polymer nanocomposites u