Harald Brünig

Melt Spinning of Poly(3‐hydroxybutyrate) for Tissue Engineering Using Electron‐Beam‐Irradiated Poly(3‐hydroxybutyrate) as Nucleation Agent

Electron-beam-irradiated poly(3-hydroxybutyrate) was used as a nucleating agent for poly(3-hydroxybutyrate) in a melt-spinning process. Molecular data and thermal properties of the irradiated samples were determined. The thermal properties of the nucleated melts were determined to assess the influence of the nucleation agents, and then spinning tests were carried out. Thermal and textile properties of the spun fibers were also determined. Estimations of the improvement of the crystallization in the spinline and of the inhibition of secondary crystallization in the fibers from the use of the described blood-compatible nucleation agents are given.

Online Spinning of Commingled Yarns-Equipment and Yarn Modification by Tailored Fibre Surfaces

A unique melt spinning equipment for E-glass is compatibly combined with a melt spinning extruder to manufacture commingled yarns. The in-situ commingling enables to combine homogeneously both glass and polypropylene filament arrays in one processing step and without fibre damage compared to commingling by air texturing. Best composite performance is achieved with a sizing for glass fibres consisting of aminosilane and maleic anhydride grafted polypropylene film former, which enable a good strand integrity with the polypropylene yarn. The results of fundamental research on variation of technological processing conditions like diameter ratios, draw ratios, variation of cooling conditions and arrangements of intermingling are reported for glass fibre/polypropylene systems.

Adjusting the mechanical behavior of embroidered scaffolds to lapin anterior cruciate ligaments by varying the thread materials

Traumatic rupture of the anterior cruciate ligament (ACL) can cause local destabilization and loss of mobility. Reconstruction using engineered ACL grafts is rarely successful due to sub-optimal material choice and mechanical performance. Thus, the presented work demonstrates the fabrication of various embroidered single- and bi-component scaffolds made of two commercially available monofilament threads (polydioxanone, poly(lactic acid-co-ɛ- caprolactone)) as well as a novel melt spun poly(L-lactic acid) multifilament and their mechanical analysis by tensile tests and under cyclic loading. Selected scaffolds, adjusted by material composition and textile parameters, revealed a load–strain behavior comparable to native lapin ACL tissue exhibiting a sufficient amount of elastic deformation within the toe-region of 1.7%, scaffold stiffness of 123 N/mm and adequate maximum tensile load (300 N) and strain (20%). Therefore, the design of resorbable embroidered bi-component scaffolds represents a promising approach to replace artificial non-resorbable ligament grafts and allows for innovative tissue engineering strategies.

Providing the right cues in nerve guidance conduits: Biofunctionalization versus fiber profile to facilitate oriented neuronal outgrowth

Following peripheral nerve injury, rapid and spatially oriented axonal outgrowth from the proximal nerve stump is required for successful tissue regeneration. Regenerative strategies such as introducing fiber bundles into the nerve guidance conduits improve the directional growth of neurons and Schwann cells. Recently, it has been proposed that fiber profiling increases cell alignment and could accelerate neuronal growth. Here, we evaluate the impact of fiber profiling on the extent of neurite outgrowth in vitro as compared to non-profiled round fibers. We developed novel profiled trilobal poly(lactic acid) (PLA) fibers and systematically tested their potency to support nerve regeneration in vitro. The profiled fibers did not improve neurite outgrowth as compared to the round fibers. Instead, we show that growing neurites are merely guided by the type and quantity of proteins adsorbed on the polymer surface. Together this data has significant implications for in vivo experiments focusing on directional regrowth of severed axons across lesion sites during peripheral nerve regeneration.

The Influence of Different Ether Carboxylic Acids on Polyester Fibre Friction

Abstract The influence of different surface active ether carboxylic acids as spin finishes on polyester fibre friction has been studied. The fibre friction was indirectly assessed through measurements of yarn tensile forces during the melt-spinning process. After manufacturing, the friction of fibre against steel was evaluated using the method of inclined plane. Results for the static fibre-steel friction coefficient obtained are in good agreement with the yarn tensile force data. The influence of different finishing agents as lubricants on the fibre friction was revealed.

Long-term hydrolytic degradation study on polymer-based embroidered scaffolds for ligament tissue engineering:

Following anterior cruciate ligament injury, a mechanically stable tissue replacement is required for knee stability and to avoid subsequent damages. Tissue engineering of the anterior cruciate ligament demands a biocompatible scaffold with a controllable degradation profile to provide mechanical support for 3 to 6 months. It has been argued that embroidered textile scaffolds made of polylactic acid and poly(lactic-co-ɛ-caprolactone) fibres are a promising approach for the ligament tissue engineering with an adapted functionalization and cell seeding strategy. Therefore, the hydrolytic degradation behaviour of embroidered scaffolds made of polylactic acid and a combination of polylactic acid and poly(lactic-co-ɛ-caprolactone) fibres was investigated under physiological conditions for 168 days. The changes in the mechanical behaviour, the molecular weights as well as the surface structures were analysed. Sufficient mechanical properties comparable to native anterior cruciate ligament tissue could be demonstrated for scaffolds made of polylactic acid fibres after 6 months under hydrolysis. These results clarify the potential of using embroidered scaffolds for ligament tissue engineering.

Bicomponent fibres for controlled release of volatile mosquito repellents

Core-sheath structured fibres were developed for application as part of an alternative malaria vector control intervention aimed at reducing outdoor malaria transmission. The fibres were prepared by melt spinning of high density polyethylene (HDPE) as sheath and with a concentrate containing volatile N,N-Diethyl-m-toluamide (DEET) in poly(ethylene-co-vinyl acetate) (EVA) as core. The concentrate was prepared by a simple absorption processes to a content up to 40 wt% DEET. Scanning electron microscope imaging confirmed the formation of a bicomponent core-sheath fibre structure. Confocal Raman spectroscopy revealed the development of a concentration gradient of DEET in the sheath layer, suggesting a diffusion controlled release process. Excellent processability was demonstrated on an extrusion system melt spinning with take up speeds reaching 3000 m min-1. Sample textiles knitted from such filaments showed high residual repellence activity even after 20 cold washes or after eight months ageing under laboratory conditions. These findings indicate that this technology offers an alternative way to prevent outdoor mosquito bites in an effective and affordable manner.

Processing of Poly(lactic Acid)

Polymer applications range from biomedical devices and structures, packaging, or toys to automotive and industrial items. So far, biopolymers could replace commodity polymers in a variety of products, especially for biomedical applications or food packaging. One of the most used and widely studied biopolymers is poly(lactic acid) (PLA). To generate new application fields and provide a broader application of PLA, research on processing behavior is still required. This chapter covers the processing relevant behavior of PLA and processing conditions for extrusion melt spinning, injection molding, and additive manufacturing. The processing-related behavior is compared to that of commodity polymers. The aim is to provide an overview of the state of the art and some recent new developments in this research field.

Acicular precipitated calcium carbonate as inorganic whisker for reinforcing of polypropylene fibers

Abstract Acicular precipitated calcium carbonate (PCC) was used as appropriate inorganic whisker for improving the mechanical properties of melt spun polypropylene fibers. Nucleation effects of the PCC in dependence to concentration, surface coating and pre-shearing were analyzed. Melt-spinning experiments were carried out in order to determine the reinforcing effect.