A new method to prepare more representative coated glass fibres for screening and development of sizings at the laboratory scale
Topic(s) : Material science
Co-authors :
James THOMASON (UNITED KINGDOM), Roya AKRAMI (UNITED KINGDOM), Liu YANGAbstract :
Size is a surface coating applied to glass fibres during manufacture, and it is perhaps the most critical component in a glass reinforced composites enabling both the uninterrupted manufacturing of the fibres and a high level of final composite performance. Despite the critical need of the composite industry to fully understand all aspects of the materials it uses; commercial glass fibres are often supplied with only two sizing related details. The first is the chemical "compatibility" of the sizing with a general class of matrix polymer. The second is a value for the Loss of Ignition (LoI), a measurement of the amount of size present on the fibres. This paucity of information on the physical and chemical nature of the sizing on a glass fibre product is an issue for many users of glass fibres, be they interested in quality control for manufacturing through to the fundamentals of the fibre-matrix interphase.
Conventional lab-scale sizing research and development, outside of the glass fibre manufacturing companies, commonly involves sample preparation by dip coating of fibre samples in a test size formulation. Although this enables investigation of chemicals that might be used in sizing formulations, this process lacks any connection with the high speed and high shear of real-world sizing application during glass fibre manufacture. Moreover, when used with sizes containing a normal concentration of components this method usually results in an unrealistically thick size layer on the fibres with a significantly higher LoI than industrial sized fibres. This makes useful evaluation of size performance and the related composite interface performance from lab-scale prepared samples highly uncertain. Consequently, there is a pressing need for the development of a lab-scale sizing process that more closely mirrors the results of the industrial process.
This paper presents a novel, but simple, glass fibre coating technique that produces a size layer similar to industrial sized samples with an average layer thickness one tenth that obtained by dip-coating. Thermogravimetric analysis and electron microscopy results show how the size layer on lab-coated fibres had a morphology much more comparable to the size layer on industrial samples. The average size layer thickness could be easily controlled in a range from 0.1 - 0.6 µm (LoI 1 – 5 %) , compared to 1.3 µm (LoI 11 %) obtained on dip coated samples when using the same sizing formulation. Microbond tests results of interfacial shear strength in two different polypropylenes indicate that the lab-sized fibres exhibited comparable values to the industrial-sized fibres and similar or enhanced values compared to the dip coated fibres. These findings highlight the considerable potential of this novel lab-scale coating technique as a viable alternative to dip coating in laboratory research, as it provides a more realistic representation of industrial-scale sizings.
Conventional lab-scale sizing research and development, outside of the glass fibre manufacturing companies, commonly involves sample preparation by dip coating of fibre samples in a test size formulation. Although this enables investigation of chemicals that might be used in sizing formulations, this process lacks any connection with the high speed and high shear of real-world sizing application during glass fibre manufacture. Moreover, when used with sizes containing a normal concentration of components this method usually results in an unrealistically thick size layer on the fibres with a significantly higher LoI than industrial sized fibres. This makes useful evaluation of size performance and the related composite interface performance from lab-scale prepared samples highly uncertain. Consequently, there is a pressing need for the development of a lab-scale sizing process that more closely mirrors the results of the industrial process.
This paper presents a novel, but simple, glass fibre coating technique that produces a size layer similar to industrial sized samples with an average layer thickness one tenth that obtained by dip-coating. Thermogravimetric analysis and electron microscopy results show how the size layer on lab-coated fibres had a morphology much more comparable to the size layer on industrial samples. The average size layer thickness could be easily controlled in a range from 0.1 - 0.6 µm (LoI 1 – 5 %) , compared to 1.3 µm (LoI 11 %) obtained on dip coated samples when using the same sizing formulation. Microbond tests results of interfacial shear strength in two different polypropylenes indicate that the lab-sized fibres exhibited comparable values to the industrial-sized fibres and similar or enhanced values compared to the dip coated fibres. These findings highlight the considerable potential of this novel lab-scale coating technique as a viable alternative to dip coating in laboratory research, as it provides a more realistic representation of industrial-scale sizings.