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Press Felts Coated with Electrospun Nanofbres

Hakala T., Heikkilä P.

Fibres & Textiles in Eastern Europe

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2011

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Vol. 19, no. 1 (84)

89-93

EN

Press felt specimens were coated with nanofbres using the electrospinning process. The coating weight of the nanofbre layer and the spinning distance were varied in order to study the homogeneity and coverage of the nanofbre web. The specimens were studied by scanning electron microscopy (SEM) and laser proflometry to understand how the nanofbre web attaches to the press felt, and how nanofbres improve the surface smoothness. The surface pore size, thickness, weight per unit area and air permeability of the specimens were measured. The surface smoothness improved and the air permeability decreased slightly. The adhesion of the nanofbre web to the press felt and the mechanical strength of the nanofbre web were poor. The study showed, however, that the combination of electrospinning and felt structures has the potential to enhance press felt performance.

2

Simulation of a rapid nip pressure strike and its effect on press felt samples

Hakala T., Harlin A.

Autex Research Journal

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2008

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Vol. 8, no. 3

84--91

EN

Special technical textiles are used in papermaking to support, transfer, and dewater the paper web. These textiles, paper machine cloths, have many essential functions connected to their position on the paper or board machine. Mechanical wet pressing uses press felts, whose porosity and resiliency are important for effective dewatering. Water is squeezed out by two overlapping paper machine rolls, which form a nip. After squeezing, the porous felt should be void and return to its original thickness to ensure efficient dewatering. Friction forces are also present at the nip, since abrasive interfaces occur between the cloths and the rolls by pressure, heat, and movement. Thus in time, the harsh papermaking process wears out the press felt, deteriorating its quality. At high machine speed, defects in press felts, rolls, or other parts of the nip environment can cause runnability problems such as noisy run, that is, vibration in the pressing section, decreasing paper quality and output capacity. This study sought for a new way to simulate the ambiguous nip phenomenon on laboratory scale and to find out a way to predict this noisy run problem. A dynamic test method, the Hopkinson Split Bar, was used to define the ease with which strike energy passed through from the upper roll to the lower roll and the damping of strikes by new and worn felt samples. In our study, the elasticity of the press felt was strongly linked with the ageing time. Decreased elasticity lets a nip impulse more easily through the press felt.

3

Laboratory ageing test device for press-felt clothes of paper machine

Hakala T., Wilenius T., Harlin A.

Autex Research Journal

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2007

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Vol. 7, no. 1

70--79

EN

The main part of the de-watering process in a paper machine (PM) is carried out by means of mechanical pressing, which considerably influences the paper quality and energy efficiency of the paper machine. This paper discusses a method for controlled press-felt mechanical degradation. For our research, a special test device was designed and developed to simulate press-felt ageing in the pressing section of paper machines. All the described methods and tests were carried out in the Institute of Fibre Materials Science at Tampere University of Technology.