Fibers & Textiles

Analysis of Spinneret Geometry and other Hard-to-Reach Surfaces

Problem Statement

Precisely maintained geometry of spinneret channels is crucial for optimal production conditions in fiber processes. Any deviations affect either spinning stability or product quality. Since nozzle channels are typically long and very narrow, direct microscopic inspection is not feasible.

Solution

In such cases, Analytik Service Obernburg GmbH employs a combination of microscopy and replication technology. This yields an exact negative impression of the channel, offering numerous advantages.

• Our replication material is characterized by low adhesion, allowing the impression to be easily removed even from very long channels (up to several cm) without damaging the spinneret or the impression itself.
• The shrinkage of our replication material is very low, allowing geometries and angles to be reproduced with high precision.
• The analysis of surface morphology is performed using optical microscopy (Fig. 1) or scanning electron microscopy (SEM), preserving structures even in the sub-µm range (Fig. 2).
• Surface roughness and channel structure are examined at high resolution using SEM.
• Our replication material has a short curing time (a few minutes), thus keeping the downtime of a spinneret correspondingly short. The actual analysis takes place offline on the impression.

Industries & Applications

Chemical Fiber Manufacturers – Solutions for process control and quality monitoring.

Analysis Objectives

Investigation and documentation of hard-to-reach geometries for precise quality control.

Materials

Spinnerets – Testing of channel structure and surface quality.

Analysis Methods

• Replication Method
• Light Microscopy
• Scanning Electron Microscopy (SEM)

Airbag Damage Analysis

Advantages

Scanning electron microscopy (SEM) provides well-resolved images with high depth of field. With Analytik Service Obernburg’s many years of experience in the fiber sector, various damage patterns can usually be directly attributed to their causes.

Elemental analysis in SEM can provide additional insights. The results obtained often allow conclusions to be drawn, from which solution approaches for future error prevention can be derived.

Results

• Negative impressions of two spinneret channels: Both channels are geometrically specified identically, but the channel lengths differ by approx. 10%.
• The right channel shows a slight widening in the exit area.

Internal Structure of Spinneret Channels:

• Left: Poor Quality
• Right: High Quality

Mechanical Testing under Temperature

Problem Statement

Mechanical properties such as the modulus of elasticity, tensile strength, or elongation at break show a strong temperature dependence in plastic materials. Nevertheless, the corresponding material data are often only known at room temperature – but not at low or high temperatures, as they occur, for example, when used in automotive components.

Solution

We can determine mechanical parameters of plastic materials over a very wide temperature range. For this purpose, a temperature chamber is used, which can be cooled down to temperatures as low as -80 °C by means of liquid nitrogen cooling. On the other hand, high temperatures up to 200 °C can also be reached by means of a forced air heater. This temperature chamber is operated in combination with a universal tensile testing machine (maximum tensile force 10 kN) and special clamping tools. The overall system thus enables the performance of various mechanical tests such as tensile, compression, and bending tests as a function of temperature.

• Industries:Fiber Manufacturers, Weaving Mills, Automotive Suppliers
• Analysis Objectives: Mechanical data under temperature
• Materials:Fibers, Fabrics
• Analysis Method:Tensile Test

Example – Chemical Fiber Fabric (Temperature -40 °C)

The adjacent diagram shows the stress-strain behavior of a chemical fiber fabric at three different measurement temperatures. The tensile strength reaches its highest value at –40 °C (blue curve) and, as expected, decreases significantly with increasing temperature (green and red curves). Simultaneously, the elongation at break increases with rising temperature, reaching its maximum value at 80 °C under the three test conditions.

Example – Chemical Fiber Fabric (Temperature +80 °C)

The fineness-related maximum force of a chemical fiber yarn was measured over a temperature range from –80 °C to +80 °C. The results are presented in the following figure along with a regression analysis (red line).

A nearly linear decrease in maximum force of approximately 50% is clearly visible. Such strong temperature-sensitive material changes must be absolutely considered during design and subsequent use.

Advantages

When a fabric or, more generally, a plastic is used under strongly varying temperatures, the temperature-dependent changes in mechanical properties must not be neglected. Such effects must be imperatively considered during design – be it in construction or material selection.

Mechanical tests at different temperatures allow for the determination of application-specific material parameters that are precisely tailored to your product.

How Do Holes Form in the Airbag?

Problem Statement

Particularly during the development phase of new airbag modules, damage to the airbag can sometimes be observed after deployment tests. To make optimizations, it is necessary to know the cause of such damage.

Solution

In such cases, Analytik Service Obernburg GmbH utilizes a combination of light microscopy and scanning electron microscopy (SEM). While light microscopy allows for the rapid detection of larger and smaller defects, SEM images show the morphology of the threads in detail. These often allow conclusions to be drawn about the cause and type of damage.

• Industries:Automotive Suppliers
• Analysis Objectives:Damage Analysis
• Materials:Fabrics
• Analysis Methods: Light Microscopy, Scanning Electron Microscopy

Here, the threads at the edge of the defect were flattened and often even severed. The damage pattern indicates strong mechanical influences and can clearly be attributed to the manufacturing or assembly process. Consequently, in such cases, it must be examined at which point in the process large forces act on the fabric.

The filament ends of this defect are cleanly severed, with all filaments having the same length. The defect was caused by a sharp cut. The manufacturing process must therefore be checked for sharp-edged components.

This damage pattern near a defect indicates a thermo-mechanical contact, such as occurs with strong friction and high speed. To avoid such damage, design changes to the module are often necessary.

This damage pattern is merely a “harmless” deposit due to contact with the polymer cap. Damage to the filaments has barely occurred, so the function of the airbag is not impaired.

Advantages

Results

Scanning electron microscopy (SEM) provides high-resolution images with great depth of field. Thanks to Analytik Service Obernburg’s many years of experience in the fiber sector, damage patterns can often be directly attributed to their causes. Additionally, elemental analysis in SEM offers valuable insights. The knowledge gained often allows conclusions to be drawn, from which targeted solution approaches for future error prevention can be derived.

Learning from Filter Residues

Problem Statement

Contaminants in the polymer repeatedly lead to spinning problems in chemical fiber production. While filters retain many – especially larger – particles, smaller or gel-like contaminants still pass through the filter. If a large amount of particles is retained, this leads to a premature pressure increase, so the filter must be changed prematurely. Although the polymer is cleaned by the filter, the actual cause of the contaminants remains unknown.

Solution

Analytik Service Obernburg employs microscopic techniques on cross-sections to trace the filter residues.

• Industries:Chemical Fiber, Plastics Processors
• Analysis Objectives: Process Optimization, Product Optimization, Damage Case Analysis
• Materials: Filter Screens, Contaminants, Polymers
• Analysis Methods: Light Microscopy, Scanning Electron Microscopy (SEM-EDX)
• Supplementary Methods: FTIR Spectroscopy
• Related Questions: Solids in Liquids, Inclusions

Example – Light Microscopic Analysis

After polishing the cross-section, the filter wires are visible under reflected light, but the residues are poorly discernible (Fig. 1). By using polarized light, the intrinsic color of the residues is obtained. Soot appears black here. With the help of fluorescence, degraded polymer can often be detected, which, with sufficient pressure build-up, can be forced through the filter openings. The color can be correlated with the extent of the damage.

Example – SEM/EDX Material Identification

Material identification of the residues is performed using X-ray analytics (EDX) spectra in the scanning electron microscope (SEM). This is sufficient for simple residues, e.g., mineral contaminants. If the structure is more complex, elemental distribution maps can help understand the composition. In the above case (Fig. 2), the residue originated from the wall of the reaction vessel in which the polymer was synthesized, with different polymer types being produced consecutively in the same vessel. Manganese phosphate or antimony are typical catalysts in polyester production, while titanium dioxide is used as a white pigment.

Advantages

The described method allows for the visualization and identification of filter residues. This enables the analysis of causes for contaminants and the optimization of processes. Filtration concentrates the contaminants. The method is also suitable, in a modified form, for separating and examining solids from liquids. Furthermore, Analytik Service Obernburg possesses extensive expertise in other microscopic and spectroscopic methods.

The filament ends of this defect are cleanly severed, with all filaments having the same length. The defect was caused by a sharp cut. The manufacturing process must therefore be checked for sharp-edged components.

Fig. 1: Polished sieve cross-section with soot particles (black) and degraded polymer (fluorescence images)

Fig. 2: Material Contrast (BSE) and Distribution Maps of Selected Elements

Solution Viscosity of Polyamides according to DIN EN ISO 307, of Polyester and other Polymers according to DIN EN ISO 1628-2, -5 and ISO 1628-4

Problem Statement

Do you want to know the influence of your processes on polymer properties or optimize your processing steps? Are you interested in whether a material tends to degrade under certain environmental influences? Do you want to check the polymer properties of your granulate and thus the adherence to specifications by your suppliers?

Solution

The viscosity number provides information related to the chain length of macromolecules. The method (Fig. 1) is standardized for common plastics:

• DIN EN ISO 307 for Polyamides
• DIN EN ISO 1628-2, -5 and ISO 1628-4 for Polyester and other polymers such as polycarbonate and polybutylene terephthalate.

Analytik Service Obernburg possesses decades of experience and high competence in this field, which is also demonstrated by very good interlaboratory test results.

• Industries: Automotive Suppliers, Chemical Fibers, Plastics Processors
• Analysis Objectives: Optimization, Quality Assurance, Damage Analysis
• Materials:Fibers, Plastic Granulates, Injection Molded Parts
• Analysis Methods: DIN EN ISO 307, DIN EN ISO 1628-2, -5 and ISO 1628-4
• Related Questions: Plastics Analytics, Viscosity Measurements

Appropriate sample preparation is a very important part of this service.
Due to a high degree of automation (Fig. 2), we are able to prepare the polymer solutions for measurement with great precision.
We offer viscosity number determination in a variety of solvents.

Our standard repertoire includes:

• Formic acid
• m-Cresol
• Dichloroacetic acid
• Sulfuric acid
• Hexafluoroisopropanol
• Chloroform
• Tetrachloroethane
• Solvent mixtures such as:
  • Phenol / 1,1,2,2-Tetrachloroethane
  • Phenol / 1,2-Dichlorobenzene

Do you require the viscosity number in a different solvent or solvent mixture?
Do not hesitate – simply contact us.

Advantages

Our qualified employees work in this analysis area around the clock (24/7).
Thus, we can react quickly even in very urgent cases. Even results within 24 hours are possible with us.
Contact us – we will find the best solution.
You focus on your processes, we handle the necessary analyses.

Fig. 1: Fully automatic solution viscosity measurement system; allows for the rapid processing of large sample series.

Fig. 2: Automated sample preparation system; typical polymer concentrations are 0.005 g/cm³ (0.5%) and 0.01 g/cm³ (1%).

Stability of Emulsions

Problem Statement

In an emulsion, one liquid (e.g., oil) is mixed into another liquid (e.g., water) in the form of tiny droplets. Additives and specific manufacturing conditions usually prevent the system from demixing. Despite having the same composition, batch B was unstable, meaning the oil droplets enlarged and, after a prolonged resting period of several days, settled to the bottom as large drops (Fig. 1). This demixing led to problems in further processing.

Solution

At Analytik Service Obernburg, freshly prepared batches A and B were comparatively analyzed using a laser particle size analyzer (Fig. 2).

• Industries: Chemistry, Paint Manufacturers, Fiber Manufacturers, Medical Technology
• Analysis Objectives: Process Optimization, Failure Analysis
• Materials: Emulsions
• Analytical Methods: Laser Particle Sizer
• Complementary Methods: Light Microscopy, IR Spectroscopy, NMR Spectroscopy
• Related Issues: Particle Size Distribution

Results

The poor sample (B), in its as-received state, shows a very broad droplet size distribution (red curve) with a pronounced maximum at 20 µm. If this emulsion is measured with activated ultrasound, the droplets can be reduced in size, forming a stable distribution with a maximum at 2 µm (yellow curve). The good (stable) emulsion shows the same distribution with and without ultrasound (green curve). The main proportion of droplets in the distribution is significantly below 1 µm, with a small secondary maximum at 2 µm.

In a further step, various changes were made to the manufacturing process, and the corresponding emulsions were measured for droplet size using ultrasound. The results are shown in Fig. 3. A significant variation in the relative proportions of droplets larger than 1 µm can be observed.

If the various emulsions are stored for several days, separation and the formation of distinct layers can be observed (Fig. 4). The height of these layers corresponds to the expectations derived from the droplet size distribution measurement results.

Advantages

The described method allows for the quantification of an emulsion’s quality long before demixing occurs. Furthermore, the method is suitable for measuring the size distribution of particles in powders or dispersions.

Fig. 1: Emulsions of varying stability

Fig. 4: Demixing of various emulsions after storage

Fig. 2: Droplet size distribution of two emulsions.

Fig. 3: Droplet size distribution of various batches for process optimization

Accelerated Testing of Abrasion and Wear on Technical Textiles

Problem Statement

Technical textiles, such as seat covers, are subject to a high degree of wear due to friction and abrasion. This can lead, for example, to undesirable color changes or even fabric damage. Therefore, wear tests are stipulated for such components as part of the initial sample release inspection. Passing these tests ensures that no negative changes occur within the vehicle’s service life. To detect possible changes without lengthy ongoing tests, it is necessary to simulate wear in an accelerated manner and subsequently examine the abraded samples for optical changes.

Solution

A Martindale testing device is used to simulate abrasion and wear of technical textiles. The abrasion resistance test is carried out according to DIN EN ISO 12947, on which common automotive standards such as BMW GS 97034-6 Procedure B or VW 50105 are based. In this process, the fixed flat sample is subjected to stress by an abrasive fabric under defined parameters (pressure, movement, frequency, medium) for a defined period.

• Industries: Automotive Suppliers, Textile
• Analysis Objectives: Initial Sample Release Inspection, Verification against Abrasion and Wear
• Materials: Fabrics, Plastic Finished Parts, Painted Components
• Analytical Methods: Martindale
• Complementary Methods: Color Measurement, Grey Scale ABREX, Crockmeter, Taber

Results

After the stress test, the evaluation is performed according to the specified standards. As a rule, the grey scale according to DIN EN 20105-A02 and DIN EN 20105-A03 is also evaluated.

Advantages

Abrasion and wear testing devices make it possible to investigate wear on technical textiles in the laboratory. Additionally, by simultaneously exposing them to various media, their influence on abrasion and wear behavior can be simulated in an accelerated manner. Based on the results of these tests, the suitability and quality of materials can be assessed.

Silicone Coating of Fabrics – Analysis & Durability Testing

Problem Statement

Fabrics are often coated with silicone for protection or to increase gas tightness. The coating thickness is typically determined by the applied weight. However, this area weight only provides an average value and says nothing about the local distribution or adhesion of the coating.

Solution

In such cases, Analytical Services Obernburg employs a special imaging mode of scanning electron microscopy (SEM). In this

• Industries: Fabric Manufacturers, Fiber Manufacturers
• Analysis Objectives: Coating Thickness, Penetration Depth
• Materials: Coated Fabrics
• Analytical Methods: Scanning Electron Microscopy (SEM/EDX)

Fig. 1: Front (left) and reverse (right) sides of a single-sided silicone-coated airbag fabric.

Fig. 2: Cross-section of a single-sided silicone-coated fabric

Cleaning Performance Test

Problem Statement

Special cloths, already impregnated with a cleaning and care product, are often used for surface cleaning. Sealed in foil, these are only removed shortly before use. In one instance, individual cleaning cloths showed distinct dark spots immediately after opening the packaging. It was suspected that these could be grease stains.

Solution

Analytik Service Obernburg utilizes microscopic techniques for the analysis of such stains. The filamentous structure of the very dark contamination clearly indicates a fungal infestation. Consultation with the client revealed that the cleaning medium had recently been changed to a new product, and the new medium no longer contained alcohol. To prevent this, a cleaning solution with fungicidal agents or subsequent sterilization was recommended.

• Industries: Automotive Suppliers, Chemistry, Electronics, Paints and Coatings, Plastics Processors, Mechanical Engineering, Medical Technology
• Analysis Objectives: Failure Analysis
• Materials: Contaminants of all types
• Analytical Methods: Light Microscopy, Scanning Electron Microscope
• Complementary Methods: IR Spectroscopy
• Related Issues: Inclusions

Fig. 1: Dark spots on cleaning cloth, showing a filamentous structure at higher magnification.

Fig. 2: Particle deposits on the cleaning cloth (material contrast)

Fig. 3: Elemental composition of the particle deposits.

Defect Analysis

Problem Statement

In textile fabrics, for example, contamination, adhesion issues, and damage can lead to complaints. If such problems occur, identifying the root cause is essential.

Solution

In such cases, Analytical Services Obernburg frequently employs scanning electron microscopy (SEM). This provides images with high resolution and depth of field. In conjunction with X-ray microanalysis (EDX), it also allows for the characterization of the elemental composition of the smallest defect areas.

• Industries: Fiber Manufacturers, Weaving Mills, Coaters
• Analysis Objectives: Failure Analysis
• Materials: Fabrics
• Analytical Methods: Scanning Electron Microscopy (SEM-EDX), Light Microscopy

Fig. 1 Example – Fabric with Dark Stripe

Fig. 2: Scanning electron micrographs of the topography contrast (left) and material contrast (right) of a PVC-coated fabric in cross-section.

Analyses on Yarns & Textiles

Introduction

Spin finish, also known as spin oil or spinning auxiliary, is an essential component in the production of yarns and subsequently fabrics for technical or textile applications. These are liquid or pasty formulations applied to the surface of fibers to improve their physical properties and thus facilitate the processing step. The determination of spin finish is therefore crucial for the quality and efficiency of the product and subsequent processing steps.

Methods

There are various methods for determining spin finish, which can be used depending on requirements and available resources:

1. Wet Chemical Extraction Method: This traditional gravimetric method involves the extraction of the spin finish from the fibers with a suitable solvent and the subsequent gravimetric determination of the extract. Although this method is precise, it requires the use of chemicals.

Time Domain Nuclear Magnetic Resonance (TD-NMR):

This modern method utilizes nuclear magnetic resonance to determine the spin finish content. The advantage of this method lies in its high accuracy and repeatability, as well as rapid results delivery. The gravimetric method serves as the basis for this quantification. Once established, however, it provides an unbeatably fast and solvent-free method.