Preparation of single pulp fibres for dynamic mechanical

Preparation of single pulp fibres for dynamic mechanical

Report on a Short Term Scientific Mission
Preparation of Single Pulp Fibres for Dynamic Mechanical Analyses Using a
Microrobotic Platform
Applicant:
Dr. Stephan Daus
Paper Technology Specialists (PTS)
Pirnaer Str. 37
01809 Heidenau - Germany
Tel: + 49-3529-551674
Email: stephan.daus@ptspaper.de
Host:
Prof. Pasi Kallio
Micro and Nanosystems Research Group
Department of Automation Science and Engineering
University of Technology (Tampere)
Tel: + 358-500-525546
Email: pasi.kallio@tut.fi
Program:
Arrival
15/08/2012
Departure:
24/08/2012
Start of the Work: 16/08/2012
End of the Work: 24/08/2012
Special Event: 21/08/2012 participation in the Summer Seminar of the Micro- and
Nanosystems Research Group.
Background
Almost all stages of the paper production process, e .g during pressing, drying, calendaring and
printing, dynamic processes with frequent loading and relaxing at different relative humidity play
a crucial role. Imitation of the load on fibres and paper during the paper production process
can be considered as one of the major advantages of dynamic mechanical analysis (DMA). This
instrument measures E-Moduli in dependence on loading, i.e. different amplitudes,
frequencies and humidity.
Until now DMA usually measures paper as a whole bulk material even though basic paper
properties (tensile, tear and burst index) strongly depend on single fibre properties. This is
mainly due to difficulties in handling of single fibres with dimensions of 2 mm and about 20
µm thickness and lack of accessibility of a versatile device for the measurement.
Nevertheless, current research at the PTS aims at the development of a DMA method for the
measurement of single pulp fibre properties. Therefore an alumina device has already been
developed which allows the adhesive bonding, placing and measurement of single pulp fibre
in a DMA instrument (Figure 1). One of the major drawbacks of the current device is the
rather limited number of samples to be prepared and statistical errors can not be ruled out.
The use of a microrobotic platform as it exists in the Micro- and Nanosystems Research
Group at the TU Tampere to prepare a large number of samples was the goal of this short
term scientific mission.
Adhesive
Fibre
Figure 1: Device for the fixation of single pulp fibre s.
Results
A microrobotic platform for the manipulation and mechanical characterization was used for
the preparation of pulp single fibres and subsequent fixation over a well defined gap on spring
plates (Figure 2).
The teleoperated process consisted of the following steps:
a) Disintegration of pulp in an excess of water.
b) Selection, grasping and stretching of single pulp fibres (Figure 3, left)
c) Positioning and release of the pulp fibre over a well prepared spring plate. The preparation
included the mounting of one droplet of an Aquaseal UV curable adhesive and following
release from the grippers (Figure 3, right)
d) Curing of the glue by UV light.
Figure 2: Microrobotic platform, equipped with a rotary Microgrippers (1) and (2), an XYtable (3) and a rotary table (4).
Figure 3: Stretching of Single pulp fibre and positioning over adhesive droplets on spring
plates (left); fixing of single pulp fibres in the adhesive (right).
Following that procedure 82 single fibres were fixed on spring plates using the teleoperated
microrobotic platform. The samples are sent to the PTS Heidenau for the following
determination of E-Moduli by dynamic mechanical analysis. Due to the large number of
prepared samples a significant reduction of statistical errors of the measurements will be
possible.
Methods
Microrobotic platform
For Fixing of the fibres a microrobotic platform from the host institute was used. For the
present task the microrobotic platform consisted of two microgrippers (1) and (2) (SmarAct
Co.) and a 2DOF XY-table (6) (SmarAct Co.) with a rotary table mounted on it. The rotary
table was used for placing of the fibre suspensions and fibre orientation so that it was possible
to grasp pulp fibre s. The visualisation system consists of a top view camera, and a side view
camera. The process of grasping and fixing of the fibres was teleoperated.
Fixing of Soft Wood Craft Pulp fibres on spring plates
Fibres of an unbeaten soft wood craft pulp were fixed over a 1 mm gap on spring plates of
100 µm thickness. The geometry of the spring plates is depicted in Figure 1. Therefore the
pulp was disintegrated in 10 mL of distilled water and 1 mL was transferred to the rotary
table. After positioning and orientation pulp fibres were taken out from the solution using the
grippers of the microrobotic platform and transferred to the spring plate. Before fixing, one
droplet of Aquaseal UV was placed on the edges of the 1 mm gap on the spring plates. The
fibres were than released over the droplets and the adhesive was cured using an UV light
immediately.
Acknowledgement
The author of this report greatly acknowledges Prof. Pasi Kallio and the Micro- and
Nanosystems Research Group of the TU Tampere to allowing to carry out the experiments.
Special thanks go to Pooyah Saketi for teaching how to operate the microrobotic platform.
All participants acknowledge the Association of European Fibre and Paper Research
Organisations (EFPRO) for the travel grant.