1. ABOUT THE DATASET -------------------- Title: Data for Design of experiments investigation into the production of all cellulose composites using regenerated cellulosic textiles Creator(s): Ashley Victoria, Peter John Hine, Keeran Ward, Michael Edward Ries. Organisation(s): University of Leeds Rights-holder(s): Copyright 2024 University of Leeds Publication Year: 2024 Description: Data for All cellulose composites (ACCs) can be produced from native and man-made cellulosic fibres; use of the latter provides an additional application for waste-derived regenerated fibers. ACCs were prepared using an ionic liquid dissolution method, utilizing a regenerated cellulose (Tencel) textile, with and without an interleaf cellulosic film. A design of experiments methodology was applied to explore process-property relationships; concentration of the ionic liquid and the processing time and temperature were investigated. It was found that the film remained in-between the textile layers, rather than penetrating the fiber assembly, in contrast to our previous work on cotton-based ACCs. This is due to the structural differences between Tencel and cotton fabric. A multi-response optimization was conducted through a central composite face centered strategy, which captured the film system more strongly. Optimized processing conditions were identified, yielding a Young's modulus and strain-to-failure of 5.3 GPa and 3.5% respectively, validated through in-lab samples. Mechanical Testing Tensile strength, Young's modulus and strain-to-failure were evaluated using an Instron 5584 universal tensile tester according to ASTM D1846. Test specimens were cut using a laser cutter to a gauge length of 30 mm and width of 5 mm and tested using a crosshead speed of 10 mm/min. Density measurement A gravimetric approach was used to determine the densities of the optimized ACCs. The dimensions of cut specimen samples were measured using an RS PRO digital caliper to obtain the specimen volume, and subsequently weighed. For each ACC, three specimens were measured and weighed to obtain an estimation of error. A reference value of 1.5 g/cm3 was used for the density of the cellulosic materials within the ACC, drawing from existing literature; the density of plant fibers is reported to be between 1.4 and 1.5 g/cm3 [44]. Cellulose II is reported to have an approximate density at 1.5 g/cm3, and the density of bulk amorphous cellulose is estimated to be in the range of 1.48 to 1.5 g/cm3. Optical microscopy Cross-sections of the prepared ACCs were observed using an Olympus BH2 microscope in reflection mode. Composite thickness measurements were then extracted from these images utilizing ImageJ software. To enhance image clarity, samples were embedded in epoxy resin using a silicon mold and subsequently polished. To ensure an accurate representation of each sample was presented in this paper, multiple images were obtained from which thickness measurements were taken. For each ACC sample, an average thickness value, along with the corresponding standard error, was calculated from six measurements. Cite as: Victoria, A., Hine, P.J., Ward, K., Ries, M.E., (2024): Data for Design of experiments investigation into the production of all cellulose composites using regenerated cellulosic textiles. University of Leeds. [Dataset] https://doi.org/10.5518/1550 Contact: m.e.ries@leeds.ac.uk 2. TERMS OF USE --------------- Copyright 2024 University of Leeds. Unless otherwise stated, this dataset is licensed under a Creative Commons Attribution 4.0 International Licence: https://creativecommons.org/licenses/by/4.0/. 3. PROJECT AND FUNDING INFORMATION ---------------------------------- Title: Development and Optimisation of All Cellulose Composite Dates: October 2020 Funding organisation: EPSRC Grant no.:EP/SO22473/1 4. METHODS ---------- References can be found in the article itself 2. Materials and Methods 2.1. Materials Regenerated cellulose (Tencel) was used for this work, purchased from Ecological Textiles, Netherlands. The fabric has an areal density of 140 g/m2 and a thread count of 144. Natureflex 23NP cellulose film with a thickness of 23 µm was used as the interleaf cellulosic film layer, supplied by The Futamura Group. The films were used as supplied, as the small additives present in these films do not significantly affect the dissolution process [33, 43]. Ionic liquid [C2MIM][OAc] with a purity of ≥ 95% was purchased from ProIonic and co-solvent dimethyl sulfoxide (DMSO), with a purity of ≥ 99.9%, was purchased from Fisher Scientific. 2.2. ACC Processing ACCs were produced via our previously reported method of partial dissolution with applied heat and pressure [33, 43], using two layers of Tencel textile. A schematic of the process is shown in Fig 1. In this work, the two systems under investigation; processing ACCs with two layers of textile only, and processing with the addition of the interleaved cellulosic film between the layers, are referred to as F0 and F1 respectively. [Fig 1 here] Two Tencel textile layers were stacked aligning the warp yarns at 0°, giving a stacking sequence of (0,0). The stack was then immersed in a solution of [C2MIM][OAc] and DMSO, and subsequently placed in a laboratory heat press and heated under pressure. A fixed processing pressure of 2 MPa was used for all the experiments. Pressure was explored through DoE in our previous work on cotton-based ACCs [43], where it was found to have no significant effect on the resulting ACC properties. A setting of 2 MPa does, however, allow the textile stack to maintain shape during processing. The textile layers were weighed to determine the dry mass of cellulose to be processed, and a solvent to cellulose (S/C) weight ratio of 3:1 was used. This aligns with our previous work where it was found that a 3:1 S/C weight ratio resulted in sufficient matrix production to yield a fully consolidated ACC [33]. This helps to overcome flashing, where excess dissolved cellulose is expelled from the stack when pressure is applied. Additionally, there is no gain from limiting solvent use at laboratory scale when scaling up would involve the use of a solvent bath, exposing the textile substrate to excess solvent. The solvent solution comprised a mixture of [C2MIM][OAc] and DMSO, with the % by weight of [C2MIM][OAc] being one of the process factors studied. In our previous work using cotton textiles, the % weight of [C2MIM][OAc] was explored through the one-factor-at-a-time (OFAT) method, where it was found that adding 20% DMSO allows for ease of application to the textile stack by lowering the viscosity of [C2MIM][OAc][33]. In this work, the % by weight of [C2MIM][OAc] was varied from 30 % to 100 % to explore its influence further. Dissolution time and temperature were also varied as part of the experimental design. After dissolution, the samples were placed in a coagulation bath of distilled water at room temperature and left for 1200 minutes (20 hours) to allow the solvent to be removed. The stack was then dried in the heat press at fixed temperature, pressure, and time of 125 °C, 2 MPa and 60 minutes respectively [33, 34, 43]. 2.3. Mechanical Testing Tensile strength, Young's modulus and strain-to-failure were evaluated using an Instron 5584 universal tensile tester according to ASTM D1846. Test specimens were cut using a laser cutter to a gauge length of 30 mm and width of 5 mm and tested using a crosshead speed of 10 mm/min. 2.4. Materials Characterisation 2.4.1. Density measurement A gravimetric approach was used to determine the densities of the optimized ACCs. The dimensions of cut specimen samples were measured using an RS PRO digital caliper to obtain the specimen volume, and subsequently weighed. For each ACC, three specimens were measured and weighed to obtain an estimation of error. A reference value of 1.5 g/cm3 was used for the density of the cellulosic materials within the ACC, drawing from existing literature; the density of plant fibers is reported to be between 1.4 and 1.5 g/cm3 [44]. Cellulose II is reported to have an approximate density at 1.5 g/cm3, and the density of bulk amorphous cellulose is estimated to be in the range of 1.48 to 1.5 g/cm3 [45]. 2.4.2. Optical microscopy Cross-sections of the prepared ACCs were observed using an Olympus BH2 microscope in reflection mode. Composite thickness measurements were then extracted from these images utilizing ImageJ software. To enhance image clarity, samples were embedded in epoxy resin using a silicon mold and subsequently polished. To ensure an accurate representation of each sample was presented in this paper, multiple images were obtained from which thickness measurements were taken. For each ACC sample, an average thickness value, along with the corresponding standard error, was calculated from six measurements. 2.5. Experimental Design 2.5.1. Full factorial design A 23 full factorial design was used for preliminary exploration of compaction temperature, process time, and % by weight of [C2MIM][OAc] (IL %), and their influence on ACC properties. Here, the three continuous, independent factors each have 2 levels that represent the minimum and maximum settings. Fig 2 outlines the experimental domain within which the experiments would be performed as determined through preliminary screening experiments and insights from previous work [43]. This was to ensure the range over which to collect data was wide enough to capture the data effectively, whilst maintaining ACC quality. Six center points (CPs) runs were included to provide sufficient degrees of freedom, comprising a combination of the mid-points of all factor settings. Table 1 outlines the continuous factors and their coded values. Runs were conducted for both F0 and F1 systems, therefore, the use of the interleaf film is included as a categorical factor. A representation of the full factorial design domain is shown in Fig 2(a). For compaction temperature, a lower limit of 30 °C was chosen to allow accurate maintenance in the laboratory environment, and an upper limit of 120 °C was chosen to avoid damage of the ACCs which was found to occur beyond this point. To determine the range of times to be explored, several preliminary samples were made at 120 °C, and it was found that the Tencel based ACCs were not damaged if processed at a maximum of 180 minutes.