Shredding and sieving thermoplastic composite scrap: Method development and analyses of the fibre length distributions

Vincent, Guillaume Almire; Bruijn, Thomas de; Wijskamp, Sebastiaan; Rasheed, Mohammed Iqbal Abdul; Drongelen, Martin van; Akkerman, Remko

doi:10.1016/j.compositesb.2019.107197

Cited by 42 publications

(28 citation statements)

References 17 publications

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“…Even though they used a different material, different shredders and also a slightly different technique to analyze the fiber length–a similar tendency was observed. Vincent et al 36 found no effect of feedstock size on the particle size and fiber length distribution when shredding a carbon fiber‐reinforced PPS using a two‐shaft shredder. However, it needs to be taken into account, that the shredder was not equipped with a screen, so that the material left the cutting chamber after one cutting step and no particle‐to‐particle‐interaction occured.…”

Section: Resultsmentioning

confidence: 99%

“…The quality of the regrind depends on the plate thickness, especially in relation to the gap width and thus it also depends on the machine design 34 . Another research study dealing with the regrind size and the fiber length after shredding has been published by Vincent et al 36 They investigated the effect of different screen sizes, the rotor number, feedstock size and rotor blade width of the fiber length distribution of PPS with carbon fiber reinforcement using a twin‐shaft and a four‐shaft shredder. To analyze the fiber length of the ground continuous fiber‐reinforced scrap, they used the particle form as well as the orientation of the fiber fabric in the particle.…”

Section: State Of Researchmentioning

confidence: 99%

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Influence of process parameters on the formation of inhalable fiber dust during shredding for mechanical recycling of fiber‐reinforced organo sheets

Tölle

Hopp

2022

J of Applied Polymer Sci

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Shredding is a major process step in mechanical recycling, as the plastic scrap needs to be cut into small pieces for further processing. It will be melted and finally injection‐molded to form new plastic parts. Also for fiber‐reinforced thermoplastics, the mechanical recycling process is an ecofriendly process because all resources are reused. One challenge during the shredding of fiber‐reinforced plastics is the fiber dust formation. The fiber dust disturbs the following production processes, and the fiber fragments can be alveolar and thus potentially toxic. Therefore, it is a major aim of this research to optimize the cutting process by investigating the effect of different shredding parameters on the alveolar fiber dust formation. Three different continuous fiber‐reinforced thermoplastic organo sheets (PP with glass fibers, PA6 with glass fibers, PA66 with carbon fibers) are shredded while the parameters of throughput, rotational speed, screen size and feedstock size are varied. The results show no clear effect of the throughput either on the amount of fine particles nor on the number of short fibers after removal of the plastic matrix for all materials. Reducing the screen size in the cutting mill leads to a large increase in the amount of fine particles and on the number of short fiber fragments. Additionally, the rotational speed has a large impact on the amount of fine particles. With increasing rotational speed, the number of fine particles rises, whereas there is no major effect on the fiber length distribution. The investigations relating the rotational speed are valid for all materials, throughput, screen sizes and feedstock sizes. Decreasing the feedstock size leads to an increasing amount of fine particles with no change in fiber length distribution for the glass fiber‐reinforced organo sheets. For the carbon fiber‐reinforced materials, it does not lead to any change in the amount of fiber dust but to an increase in shorter fibers. Thus this parameter seems to be material dependent. Images taken by a scanning electron microscope show alveolar fiber dust fragments in the ground material of all samples.

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Section: Resultsmentioning

confidence: 99%

Section: State Of Researchmentioning

confidence: 99%

Influence of process parameters on the formation of inhalable fiber dust during shredding for mechanical recycling of fiber‐reinforced organo sheets

Tölle

Hopp

2022

J of Applied Polymer Sci

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“…Some batches of shredded flakes were sieved with a multi-stage vibrating sieve. The fibre length distribution (FLD) of the output flakes, as well as the shredding and sieving process, were previously characterised in [10,32] . The FLDs of the categories of flakes used in this study are shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Characterisation and improvement of the quality of mixing of recycled thermoplastic composites

Vincent

Bruijn

Wijskamp³

et al. 2021

Composites Part C: Open Access

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A low-shear mixer was used to blend thermoplastic composite scrap material into a molten mixed dough, which was then compression moulded. This process is a key step in a novel recycling solution for thermoplastic composites. A study was carried out to characterise the quality of mixing (QoM) of the blended doughs to understand how to improve the QoM of mixed doughs towards further improvement and implementation of the recycling solution. In order to achieve this, the effect of mixing parameters and fibre length on the QoM were studied. This study used shredded C/PPS flakes, originating from consolidated laminate scrap. These flakes are about 20 mm in size, and contain woven fabric reinforcement, making them far different from regular pellets, and therefore more difficult to mix. The QoM was characterised by means of image analysis of a large set of cross-sectional microscopy images, based on which the scale and intensity of segregation of the fibre clusters were evaluated. Bundle size distribution was determined by applying Delaunay triangulations to cluster the fibre centres. These methods were found to be suitable for characterising the QoM of such doughs. Increasing the mixing time and mixing speed were identified as key ways to improve the mixing process. With the current mixing machine, it is also suggested not to use fibres longer than 15 mm on average in order to limit intra-dough variability. For doughs made of fibres longer than 15 mm, improvements on the mixing device could sufficiently increase the QoM.

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“…Instead, an estimated fibre length reduction in the case of shredded flakes was calculated. The FLD prior to processing was measured from the flakes 29 and is shown in Figure 16 as a solid line. Based on that, each fibre length was assumed to be attrited similarly to the measured 20 mm long fibres (Figure 15), i.e.…”

Section: Fibre Attritionmentioning

confidence: 99%

Process- and material-induced heterogeneities in recycled thermoplastic composites

Vincent

Bruijn

Wijskamp

et al. 2020

Journal of Thermoplastic Composite Materials

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A novel recycling solution for thermoplastic composites (TPCs) was recently implemented. The processing steps comprise shredding of TPC offcuts to flakes of a few centimetres, melting and blending of the flakes in a low-shear mixer, extrusion of a molten mixed dough and subsequent compression moulding in a press. This material and process are similar to the compression moulding of long-fibre thermoplastics (LFTs) that have been in the market for decades, such as glass mat thermoplastics (GMT) or direct-LFT. However, the input material in this recycling route consists of multi-layered woven flakes, which is very different from the pellets or chopped rovings of other LFTs. Process- and material-induced heterogeneities such as fibre orientation, percolation, variation of fibre fraction, or fibre attrition may be different for this new material. The development of this recycling technology and future industrial applications require more confidence in the material and process. The objective of this study is to characterise these heterogeneities for this recycling solution, and compare them to those generated in regular LFTs. It was found that the process- and material-induced heterogeneities of the recycled TPCs are similar to other LFTs, for the aspects listed here: fibre orientation, percolation, variation of fibre fraction and fibre attrition. In comparison to GMT, the effect of the mixing step is particularly noticeable on the local variation of fibre fraction within the panels. Industrial applications of this recycling route will benefit from this similarity, as it improves the confidence in the material and process combination.

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Shredding and sieving thermoplastic composite scrap: Method development and analyses of the fibre length distributions

Cited by 42 publications

References 17 publications

Influence of process parameters on the formation of inhalable fiber dust during shredding for mechanical recycling of fiber‐reinforced organo sheets

Influence of process parameters on the formation of inhalable fiber dust during shredding for mechanical recycling of fiber‐reinforced organo sheets

Characterisation and improvement of the quality of mixing of recycled thermoplastic composites

Process- and material-induced heterogeneities in recycled thermoplastic composites

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