PAPERmaking! Vol9 Nr3 2023

PAPER making! The e-magazine for the Fibrous Forest Products Sector

Produced by: The Paper Industry Technical Association

Publishers of: Paper Technology International ®

Volume 9 / Number 3 / 2023

PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ® FROM THE PUBLISHERS OF PAPER TE Volume 9, Number 3, 2023 CONTENTS:

FEATURE ARTICLES: 1. Corrugated : Creep Performance of Corrugated Fibreboard Boxes.

2. Tissue : Angle of the Perforation Line on Partitioning Efficiency of Toilet Papers. 3. Decarbonisation : Hydrogen, Ammonia, and Methanol as Carbon-Neutral Fuels. 4. Maintenance : Data-driven Predictive Maintenance: a Paper Making Case. 5. Water Treatment : Biomass Fly Ash / Fenton Process for Wastewater Treatment. 6. Pulping : Synergies between Fibrillated Nanocellulose and Hot-Pressing of Papers. 7. Wood Panel : Quantifying the Carbon Stored in Wood Products. 8. Packaging : The Perceived Environmental Friendliness of Product Packaging. 9. Winter Driving : How to Demist your Windscreen in Double Quick Time. 10. Office Productivity : Top Tips to Improve Your Office’s Productivity . 11. Computing : Windows 10 Tips and Tricks that Help you get Stuff Done Faster. 12. Thinking Skills : How to Think Clearly: 7 Tips for Success.

SUPPLIERS NEWS SECTION: News / Products / Services :

Section 1 – PITA Corporate Members: ABB / ARCHROMA / PILZ / VALMET Section 2 – PITA Non-Corporate Members PCF MAINTENANCE / VOITH Section 3 – NON-PITA SUPPLIER MEMBERS GTEC / INVENT Advertisers: ABB & PCF MAINTENANCE

DATA COMPILATION: Events : PITA Courses & International Conferences / Exhibitions

Installations : Overview of equipment orders and installations between June and Oct. Research Articles : Recent peer-reviewed articles from the technical paper press. Technical Abstracts : Recent peer-reviewed articles from the general scientific press. The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International ® and the PITA Annual Review , both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating .

Contents

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PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ® FROM THE PUBLISHERS OF PAPER TE Volume 9, Number 3, 2023

Influence of different box preparations on creep performance of corrugated fibreboard boxes subject to constant and cycling relative humidity environments ELI M. GRAY-STUART 1 , KELLY WADE 2 , GABE P. REDDING 1 , KATE PARKER 2 & JOHN E. BRONLUND 1 To understand the effect of load and relative humidity (RH) on box creep in cool storage conditions, standard tests are performed. However, these test conditions are oversimplified compared with actual shipping conditions. Our aim is to develop test conditions that more closely mimic those encountered during refrigerated conditions to investigate their influence on creep performance and box lifetime. We compared three box preparations: (i) empty boxes used as a control, (ii) filled boxes, and (iii) boxes with only two side panels exposed to the atmosphere. A controlled environment test facility was used to subject sets of 24 boxes to 30% of their ultimate failure load under different cyclic and constant relative humidity conditions. Results indicate that filled boxes had substantially reduced performance in terms of secondary creep rate and lifetime. The fill in the box contributed to out-of-plane displacement of the side panels which manifested earlier than in the control, resulting in a higher creep rate. Boxes with only two exposed panels had lower moisture uptake and performed substantially better than the control. These findings demonstrate how creep performance and box lifetime depend on the box conditions including fill and the area of the box that is exposed for moisture transfer. Alternative box preparations which mimic supply chain conditions are worthy of investigation in creep analysis as they will help predict more accurately box performance in the cold supply chain. Contact information: 1 Department of Chemical and Bioprocess Engineering, Massey University, Palmerston North, New Zealand 2 SCION, Rotorua, New Zealand Packag Technol Sci. 2022;35:497 – 504.

https://onlinelibrary.wiley.com/doi/10.1002/pts.2646 Creative Commons NonCommercial-NoDerivs License,

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International ® and the PITA Annual Review , both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating .

Article 1 – Corrugated Fibreboard & Creep

Page 1 of 9

Received: 26 May 2020 Revised: 1 February 2022 Accepted: 20 February 2022 DOI: 10.1002/pts.2646

RESEARCH ARTICLE

Influence of different box preparations on creep performance of corrugated fibreboard boxes subject to constant and cycling relative humidity environments

Eli M. Gray-Stuart 1 John E. Bronlund 1

| Kelly Wade 2 | Gabe P. Redding 1 | Kate Parker 2 |

1 Department of Chemical and Bioprocess Engineering, Massey University, Palmerston North, New Zealand 2 SCION, Rotorua, New Zealand Correspondence E. M. Gray-Stuart, Department of Chemical and Bioprocess Engineering, Massey University, Palmerston North 4474, New Zealand. Email: e.m.gray-stuart@massey.ac.nz

Abstract To understand the effect of load and relative humidity (RH) on box creep in cool stor- age conditions, standard tests are performed. However, these test conditions are oversimplified compared with actual shipping conditions. Our aim is to develop test conditions that more closely mimic those encountered during refrigerated conditions to investigate their influence on creep performance and box lifetime. We compared three box preparations: (i) empty boxes used as a control, (ii) filled boxes, and (iii) boxes with only two side panels exposed to the atmosphere. A controlled envi- ronment test facility was used to subject sets of 24 boxes to 30% of their ultimate failure load under different cyclic and constant relative humidity conditions. Results indicate that filled boxes had substantially reduced performance in terms of second- ary creep rate and lifetime. The fill in the box contributed to out-of-plane displace- ment of the side panels which manifested earlier than in the control, resulting in a higher creep rate. Boxes with only two exposed panels had lower moisture uptake and performed substantially better than the control. These findings demonstrate how creep performance and box lifetime depend on the box conditions including fill and the area of the box that is exposed for moisture transfer. Alternative box prepara- tions which mimic supply chain conditions are worthy of investigation in creep analy- sis as they will help predict more accurately box performance in the cold supply chain.

Funding information Massey University

INTRODUCTION

they can also fail due to compressive creep (Figure 1) when a lower magnitude constant load is applied over an extended period. There are three distinct regions of creep deformation, primary, secondary, and tertiary. Primary creep occurs when the load is applied and the top and bottom flaps of the box are compressed and the load is trans- ferred to the perimeter of the box 3 and the rate of box displacement is much greater than in secondary creep. During secondary creep, the

Paper and board packaging accounts for 40% of the total packaging market. 1 Corrugated fibreboard boxes are a critical packaging element for local and international trade. Corrugated fibreboard boxes are cost effective and robust with good top-to-bottom compression strength. 2 Boxes fail when an applied load exceeds their compressive strength;

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2022 The Authors. Packaging Technology and Science published by John Wiley & Sons Ltd.

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FIGURE 1 Box displacement over time for a box subjected to constant compression in cyclic humidity conditions. The vertical dashed lines separate the primary, secondary, and tertiary creep regions, respectively

would yield different conclusions regarding secondary creep rate and box lifetime than creep tests performed on empty boxes. Cyclic RH creep tests can provide useful information about the performance of boxes for manufacturers. 14,21,22 In practice, the RH rarely exhibits uniform cycles especially in refrigerated conditions. 23 – 25 As boxed products move through a supply chain, they can experience periods of relatively constant RH interspersed with periods of variable RH. Thus, a secondary aim of this work was to explore how cycle-interval tests consisting of periods of constant RH in between controlled RH cycles would influence the box lifetime and secondary creep rate. This approach could allow manufacturers to simulate in a controlled testing facility the RH profiles experienced by their boxes in a supply chain and potentially economise this testing by focussing on the most harmful conditions experienced by the boxes.

box panels begin to bulge and the load is transferred to the corners of the box. 3 – 6 The cyclical nature of the displacement during secondary creep in Figure 1 is a result of hygroexpansion as the paper is the swelling and shrinking as the RH changes. 5 In the tertiary region, box failure is initiated as a result of local buckling near the corners which leads to hinge formation and ultimately catastrophic failure of the box. 3,7,8 It has been previously reported that the box compression strength is affected by humidity 2,9 – 11 ; likewise, failure rate due to creep is usually faster at higher relative humidities and previous research has reported higher secondary creep rates, shown to be closely related to shorter lifetimes 6,12 – 16 under cycling RH conditions compared with constant RH. 6,17,18 However, findings by Hussain et al. 3 challenge this notion that box performance is worse when RH is cycling as opposed to constant. They measured creep rates for a single type of box across a range of different cycling times under dif- ferent constant vertical loads. They found that boxes subject to a 20% BCT or higher at constant 90% RH failed earlier than boxes at these loads exposed to cycling conditions between 50% and 90% RH. This finding was attributed to creep time constants logarithmically shifting to shorter times as a result of the high applied load. Shorter creep time constants mean larger creep rates. High loads and high moisture contents produced large enough creep rates to quickly dissipate stress gradients leading to more creep than cyclic conditions. Compressive creep tests are conventionally done on single empty boxes, 3,18 and only recently, some researchers have put plastic balls inside the box to prevent them from inward buckling. 19 In reality, boxes are often palletised and contain product which may impart out- of-plane loading on the box panels thus promoting bucking of panels. 20 This can lower the top-to-bottom compression strength 20 and may accelerate failure due to creep. 21 Furthermore, during trans- port and storage, boxes are usually packed tightly on a pallet and only have one or two external side panels exposed to the ambient atmo- sphere. This is in contrast to having all four panels exposed in a tradi- tional creep test. The primary aim of this work was to see whether performing the compressive creep tests with boxes under conditions more aligned with those experienced in the refrigerated supply chain

| MATERIALS AND METHODS

2.1

Materials

For this study, single walled C-flute regular slotted containers were used. The inner and outer liners were 200 and 250 gsm Kraft liner- board made from New Zealand grown radiata pine with a 160 gsm semichem medium. The boxes were manufactured in New Zealand and obtained as flat packs with the manufacturer's flap preglued. They were stored in a controlled environment at 50% RH and 23 C. The outer dimensions of the assembled boxes were 385 248 295mm (length width height).

2.2

Box compression tests

Box compression tests (BCTs) were conducted to determine the applied load for the creep tests. BCTs were conducted in accordance to Australian and New Zealand standard (AS/NZS 1301.800s:2006). A Wiedemann universal tester was used for this testing. Boxes were compressed at a crosshead speed of 10 mm/min until failure. The

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was used for this work. Four different compressive creep conditions were performed for this study as detailed in Table 1. Boxes were sub- jected to 30% of the BCT for in all trials to represent highly loaded boxes, for example, those on the lowest layer of a pallet. The box conditioning protocol used by Hussain et al. 3 was employed for this study. Prior to preparing the boxes, they were con- ditioned for 48 h at 23 C and 50% RH as they would be for BCT. Once the boxes had been prepared, they were placed in a press in the test room. All boxes were initially subjected to two 24-h humidity cycles, consisting of 12 h at 70% RH and then 12 h at 90% RH with no load applied. Each press was equipped with a load cell and linear variable differential transformer (LVDT) which enabled the applied load and displacement to be measured, while the relative humidity and temperature in the test room was measured and recorded using multiple sensors. All data were recorded at 5-min intervals. Table 1 outlines the RH conditions for the four trials. Trials (A) and (C) were stopped at the end of a 12-h 90% RH cycle, and trial (B) was stopped at the end of a 5-day constant 90% period. This was to ensure the moisture content of the boxes would be at their maximum for the respective trials. All trials were run for between 21 and 25 days.

highest load prior to failure was recorded as the BCT load. Ten repli- cate samples were used for the BCTs, and boxes were conditioned for 48 h at 50% RH and 23 C prior to testing.

2.3

Box preparation

Three preparations of boxes were used in this study: control, filled, and foil boxes. Empty boxes were used as the control. The filled boxes contained 20 ± 0.2 kg of Chelsea ® standard granulated white sugar. Sugar was chosen as it has a similar bulk density (900 kg m 3 ) to the product normally contained in the boxes and is shelf stable. This left a headspace of ≈ 80 mm between the product and the top of the box that ensured that the box would take the applied load and not the contents. Sugar is hygroscopic; to prevent unintended issues with moisture, the sugar was packed in two black plastic (LDPE) rubbish bags which were then sealed with foil tape. The foil boxes had two adjoining external side panels, without the manufacturer's joint, cov- ered in aluminium foil to represent a box on the corner of a pallet. The foil was secured with aluminium tape. All boxes were sealed with standard brown packing tape holding the top and bottom flaps in place. The test facility had 24 presses available and for each trial eight replicates of three different box preparations were set up. Figure 2 shows how the boxes looked with the foil coating applied to two adja- cent panels.

2.5

| Box lifetime and secondary creep rate

The R code developed by Hussain et al. 3 was used to determine sec- ondary creep rate and box lifetime. Briefly, a method was developed to detect the peaks in the box displacement versus time data. For boxes which did not fail, a linear regression was fitted through the peaks of the data between 20% and 80% of the experimental time

2.4

Creep tests

Cyclic RH creep tests often use a range of at least 40% RH, with cycling between 50% and 90% of RH being commonly used. 6,15,26 In these trials, low and high RH levels of 70 and 90% at a temperature of 4.5 C were chosen. The rationale for this approach is that refrigerated storage and transport is particularly common for horticultural and agri- cultural exports. RH in refrigerated conditions is typically between 70% to 90% and the typical temperature range is 0 – 8 C and product dependent 27,28 ; the boxes used in this study are made for refrigerated product. The WHITE (Weight Humidity Intervals Temperatures Exper- iments) room test facility at the Scion Te Papa Tipu Innovation Park

TABLE 1

Creep testing conditions

Trial RH conditions A Cycling; 24 h cycles (12 h at 70% RH, 12 h at 90% RH) B Cycle/interval; 5 times 24 h cycles (12 h at 70% RH, 12 h at 90% RH), 5 days constant RH at 90%

C Constant RH at 90% D Constant RH at 70%

FIGURE 2 Assembled box with two normal panels (A) and aluminium foil covering two adjacent panels (B), the top flaps of the box were sealed with tape after the aluminium foil was applied

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packaging weight) on the boxes on the bottom layer of a pallet. It is important to acknowledge that the load distribution on a box in creep and compression tests is simplified compared with a real-world sce- nario. The stacking configuration, box misalignment, and the pallet itself all influence the load distribution. 29 – 31

period. Secondary creep rate is given by the absolute value of this gra- dient divided by the height of the boxes (295 mm). Figure 3 illustrates peak detection method used to calculate the secondary creep rate. For boxes which failed, a numerical differentiation method was used to see when the steepest gradient occurred and thus give the time at which a box failed. The secondary creep rate for boxes which failed used the same peak detection method; however, 10% to 90% of the time period was used in order to get a suitable secondary creep rate value as the time period to failure was often much shorter than boxes which did not fail.

3.2

Moisture content

The moisture content of the board at the end of the creep tests is given in Table 2. Across the four different conditions used, the aver- age moisture content was highest for the filled boxes followed by the control, the nonfoil side from the foil covered box and the foil covered panels. Aluminium foil provides a complete barrier to moisture and restricts the direct vapour access to the covered panels, so the mois- ture content will be lowest for the covered panels. It takes a long time for the board to reach equilibrium moisture content as can be seen from the difference between the constant 90% RH condition and the two cycling trials where the boxes were only held at 90% RH for 12 h and 5 days, respectively. From the sorp- tion and desorption isotherms for corrugated fibreboard presented in the literature, 3,32,33 the equilibrium moisture content for sorption at 90% RH and desorption at 70% RH are similar. We hypothesise that even during the cycling RH in trial A the mean moisture content of the panels has a narrower range than the equilibrium moisture con- tent at 70% and 90% RH, respectively. In all trials, the highest moisture content was measured for the filled boxes (Table 2). This indicates that the actual moisture content of boxes in the supply chain could be higher than what is measured from empty boxes in compressive creep tests. However, this differ- ence may not be significant enough to influence box behaviour. Hav- ing product inside the box might result in the inner liner having a higher moisture content. In an empty box, moisture from the inner liner desorbs into the air space and is adsorbed by the top and bottom

2.6

Moisture content

At the end of the trials, the moisture content of the boxes was mea- sured. The trials concluded with the 90% RH cycle apart from the con- stant 70% RH trial. The four side panels from each box were cut out and weighed immediately after the test; they were then dried at 105 C for 72 h to obtain the dry weight. The % moisture content of the board at the end of the trial was given by (wet weight-dry weight)/wet weight.

| RESULTS AND DISCUSSION

3.1

Box compression tests

The mean BCT value measured was 4.41 kN (450 kg force) with a standard deviation of 0.186 kN (18.9 kg force); 30% of the BCT value was chosen for the creep tests as it gives a load of 1.32 kN (135 kg force), which is close to the gross maximum load that these boxes would experience when palletised in the supply chain. The boxes used in this study are typically palletised with an interlock pattern six high, which is an equivalent total load of 1.23 kN (125 kg force plus

FIGURE 3 Example of box displacement data over time for a box from trial A. The black dots indicate peaks and the solid grey lines are linear regressions through the peaks and a rolling mean respectively, taken within the second and eighth data quantiles represented by the outermost dotted vertical lines

TABLE 2 Moisture content (% wet basis) of the board at the completion of the trials, mean with standard deviation in brackets

Trial

Control

Filled boxes

Foil sided bare

Foil sided covered

13.4 (0.25) b

14.0 (0.34) a

13.3 (0.32) b

12.2 (0.27) c

14.2 (0.28) a,b

14.5 (0.22) a

14.1 (0.36) b

13.1 (0.31) c

14.9 (0.25) a

15.0 (0.40) a

14.7 (0.59) a

14.7 (0.55) a

11.0 (0.21) a,b

11.1 (0.13) a

11.0 (0.20) a,b

10.8 (0.14) b

Note : For each trial, means followed by a common letter are not significantly different by the HSD test at 5% level of significance.

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faster rate. The overall strength and response to loading of these panels could be altered by this imbalance in moisture content between the inner and outer liners and result in the panels bowing inwards. This inward deflection would not occur under supply chain condi- tions as the product in the box would provide support and prevent this from happening. This is shown in Figure 4C,D which shows the uncovered and foil covered panels of the same box which failed in trial (B). The mean box lifetime for the filled boxes was around half that of the control boxes in trials (B) and (C). The boxes with foil coated panels had the longest lifetime and lowest creep rate across all trials. The mean and median box lifetimes were similar with the largest dif- ference being 2.4 days for the control boxes in trial B. If the number of box failures is low the box lifetime in is not a useful metric. However, the box failure rate provides a good indica- tion of relative box performance across different preparations and test conditions. The failure rate of boxes which experienced 12-h cycling was lower than those at constant 90% RH (Table 3), this finding is in line with Hussain et al. 3 but in contrast to several previous studies It is noteworthy that no foil boxes under cycling conditions failed while a significant number of foil boxes failed when exposed to constant 90% RH and the cycle/interval conditions. These results support the notion that exposure to constant high RH% can be worse for box perfor- mance than cycling conditions with a load greater than 20% BCT. Furthermore, this shows that if one wants to mimic the conditions a box will experience in the supply chain, periods of constant high RH should not be omitted and may and increase creep rate more so than continuous cycling. Further research in this area will undoubtedly be of some benefit to the packaging industry.

flaps. If there is a product occupying most of the internal space, the rate of mass transfer from the inner liner to the air space and box flaps will be reduced. This will result in the inner liner of the panels having a higher moisture content as there is less moisture transfer to the air space and box flaps than in an empty box. As can be seen Table 2, some preparations affect the moisture content under some test conditions. The moisture content and its var- iation in fibreboard during cycling for different box preparations is something which has not previously been investigated. The response of moisture content in relation to changes in RH is further compli- cated by the adsorption and desorption phenomena which is also worth pursuing in future studies. Given the correlation between box performance and moisture content such information could help understand vulnerability of boxes to creep.

3.3

Box failure and lifetime

Boxes were examined at the end of the trials to assess the failure they experienced. Failure was observed in all trials and preparations except for constant RH 70% and the foil covered boxes with the 12-h cycling time where there were no failures; 100% failure was observed for the control and filled boxes in trial B. The type of fail- ure exhibited by the control and filled boxes was as previously described 26,34 where buckling occurs in the corners which results in hinge formation leading to out-of-plane displacement on the larger side panels (Figure 4A,B). An interesting observation was that boxes with the foil coating behaved differently to the control and filled boxes where the panels with foil buckled inwards. Having foil on the outer liner likely results in the inner liner gaining moisture at a

FIGURE 4 Manifestations of box failure as a result of creep deformation observed in this study: (A) and (B) show all panels of a control box in which it can be seen that creases and hinges form at the corners of the box which leads to buckling and global failure; (C) and (D) show the panels of a foil box, where similar creases and hinge formation is observed while the foil coated panels moved inward, this was observed for all foil boxes which failed

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TABLE 3

Box lifetime results for each trial in this study

Trial

Preparation Median life time (days)

Mean life time (days)

CV (%)

Number of boxes Number of failures Failure rate

Control

11.4

14%

Filled

12.7

12.3

75%

Foil

n/a

Control

12.4

100%

Filled

5.5

5.6

100%

Foil

16.0

15.9

83%

Control

7.2

9.6

50%

Filled

3.4

5.4

101

88%

Foil

11.1

10.4

71%

D Control

n/a

Filled

n/a

Foil

n/a

TABLE 4 30%BCT

Mean secondary creep rate for all trials with boxes at

rate of the filled boxes is significantly different from the control and foil boxes, while there is no difference between the control and foil box preparations. These results show that the internal pressure from the box fill can have a significant negative impact on box performance and creep rate under certain conditions. At constant 70% RH, the box fill had less of an influence on creep rate, there was a significant dif- ference between the filled and control boxes but not the filled and foil boxes. The reason why the filled boxes performed worse at higher humidities could be due to the mechanical properties of paper decreasing with increasing moisture content. A likely mechanism is that at higher moisture contents the stiffness of the panels decrease to a point where the internal pressure from the box fill can increase the rate of panel bulging relative to the control and in turn increase the creep rate. These results give merit to having different box prepa- rations in creep tests as box performance is significantly affected when presented in a way that is more representative of supply chain conditions. There is no significant difference in the creep rates of the foil and control boxes within the same trial. In constant RH conditions, the foil does not prevent the box panels from reaching the same moisture content as the uncoated panels so the creep rate will be similar. How- ever, under cycling conditions, the foil has a significant effect on the moisture content of those panels as the 12 h cycle time is not long enough for them to reach equilibrium. While the difference in creep rate is not statistically significant, Figure 5 shows that the maximum creep rate observed for the foil boxes is lower than the median for the control. Extrapolation box performance from creep tests on nor- mal boxes could result in creep rate and box lifetime being under- predicted as box performance is influenced by uneven distribution of moisture content. When boxes are palletised, boxes on the side of the pallet have only one panel exposed to the ambient conditions and boxes within the pallet can have all surfaces in contact with other boxes and no ambient exposure. The findings here demonstrate that the creep rate and box life- time are highly dependent on how the box is prepared. Notably the boxes with product performed considerably worse, having a shorter

Trial

Condition Creep rate per day CV (%)

Log creep rate

2.82E 04 a 8.90E 04 b 1.31E 04 a 8.12E 04 a 1.57E 03 b 5.23E 04 a 9.36E 04 a 2.88E 03 b 7.05E 04 a 1.78E 05 b 2.92E 05 a 2.28E 05 a,b

A Control

74%

8.17 7.02 8.94 7.12 6.45 7.56 6.97 5.85 7.26

36%

Filled

24%

Foil

B Control

24%

Filled

20%

52%

Foil

88%

C Control

Filled

56%

61%

Foil

D Control

25%

10.9 10.4

Filled

32%

Foil 10.7 Note : For each trial, the secondary creep rate for each box preparation was compared with a post hoc Tukey HSD test. Means that do not share a letter are significantly different. 22%

3.4

Secondary creep rate

The mean creep rate for each trial is shown in Table 4, and the creep rate data are presented in a box and whisker plot in Figure 5. A post hoc Tukey HSD test was performed to determine if there were signifi- cant differences in the mean creep rate of the box preparations within each trial and to compare the effect the RH conditions had on each box preparation (Table 5). The coefficient of variation (CV) for creep rate is higher than found in most previous studies 3,26,32 ; however, it is worth noting that CV was positively correlated with %BCT in the study by Hussain et al. 3 and the load used in this study is at the upper end of this range. The control in trials A and C have a notably higher CV of 74% and 88% and the failure rate of boxes in these tests was 14 and 50%, respectively. This tends to skew the variation in creep rate as the boxes which fail, especially if they fail early on, usually have a considerably higher creep rate. For trials A, B, and C, the creep

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FIGURE 5 Secondary creep rate from all trials, box length depicts the interquartile range and the median is the horizontal line in the box, whiskers represent the maximum and minimum ranges of the data, except the outliers (black circles) which exceed 1.5 times the interquartile range

TABLE 5

Comparison of secondary creep rate for box preparation

chain conditions where boxes contain product and do not have uni- form exposure to the ambient conditions. It is acknowledged that dynamic loading and vibration are two other phenomena which fur- ther impair box performance and are important in real world scenarios, 24 the stiffness of pallet deckboards also influence box com- pression strength. 31 However, these aspects have not been consid- ered here due to cost and complexity and because the primary aim of this work was to isolate humidity effects on box performance.

as function of trial conditions

Box preparation

Trial condition Secondary creep rate (day 1 )

9.36E 04 a

Control

Constant 90% RH

8.12E 04 a 2.29E 04 b 1.80E 05 b

Alternate

Cycling

Constant 70% RH Constant 90% RH

CONCLUSIONS

3.69E 03 a

Filled boxes

1.57E 03 b 9.72E 04 c 3.10E 05 d

Alternate

The secondary creep rate and lifetime of boxes containing product was significantly shorter than the control and foil-covered boxes. This was attributed to the internal pressure imparted on the panels by the product; this can result in out-of-plane displacement of the side panels manifesting much earlier leading to a higher creep rate and shorter lifetime. Conversely, boxes which had two panels covered with foil had lower moisture uptake and performed better than the control in cycling conditions. The resultant lower moisture content of the coated and uncoated panels of this box preparation means the box remains stronger for longer. Furthermore, the foil acts as a barrier so the panels are not subjected to as larger changes in moisture con- tent so the MC% will remain closer to the mean value. These results show that future studies should consider mimicking the actual surface available for moisture transport as it has a significant influence on the box lifetime. The lifetime of the filled boxes in the cycle-RH interval tests was shorter than those which experienced only cycling conditions, but those exposed to constant 90% RH had the shortest lifetime. The results presented here further support the findings

Cycling

Constant 70% RH Constant 90% RH

8.00E 04 a

Foil boxes

5.23E 04 a 1.31E 04 b 2.30E 05 b

Alternate

Cycling

Constant 70% RH

Note : Outliers identified using the interquartile range (IQR) criterion have been removed. Means that do not share a letter are significantly different.

lifetime and higher creep rate than the other two preparations. Fac- tors such as the internal pressure from the product 20 and the distribu- tion of moisture content of the box panels can significantly affect box performance. Including these enables the box performance to be quantified in conditions which are more representative of supply

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GRAY-STUART ET AL .

of Hussain et al. 8 that conditions of constant high humidity can result in poorer box performance than cycling when the load is greater than 20% BCT and therefore that this factor plays an important role in box failure. ACKNOWLEDGEMENT Open access publishing facilitated by Massey University, as part of the Wiley - Massey University agreement via the Council of Australian University Librarians. DATA AVAILABILITY STATEMENT The data that support the findings of this study are available from the corresponding author upon reasonable request. Open access publishing facilitated by Massey University, as part of the Wiley - Massey University agreement via the Council of Australian University Librarians.

15. Leake C, Wojcik R. Humidity cycling rates: how they influence container life spans: Corrugated containers. Tappi Journal . 1993;76(10):26-30. 16. Urbanik T. A more mechanistic model of the compression strain-load response of paper. Journal of Pulp and Paper Science . 2002;28(6): 211-216. 17. Habeger Jr CC, Coffin D. The role of stress concentrations in acceler- ation creep and sorption-induced physical aging. 1999. 18. Van Hung D, Nakano Y, Tanaka F, Hamanaka D, Uchino T. Preserving the strength of corrugated cardboard under high humidity condition using nano-sized mists. Composites Science and Technology . 2010; 70(14):2123-2127. doi:10.1016/j.compscitech.2010.08.011. 19. Sherman NNL. Investigation into the effect product can have on box failure during creep tests. 2012. 20. Peleman D, Singh J, Saha K, Roy S. Evaluation of a bulge reduction technology for corrugated fiberboard containers under static compression. Journal of Applied Packaging Research . 2020;12(1):6. 21. Coffin DW. The creep response of paper. in 13th Fundamental Research Symposium, Cambridge. 2005. 22. Morgan DG. A mechanistic creep model and test procedure. Appita: Technology, Innovation, Manufacturing, Environment . 2004;57(4):299 doi:10.1016/B978-012226570-9/50076-4. 23. Nevins AL. Significant Factors Affecting Horticultural Corrugated Fibreboard Strength: A Thesis Presented in Partial Fulfilment of the Require- ments for the Degree of Doctor of Philosophy in Food Engineering at Mas- sey University, Palmerston North, New Zealand . Massey University; 2008. 24. Eagleton DG. Creep Properties of Corrugated Fibreboard Containers for Produce in Simulated Road Transport Environment . Victoria University of Technology; 1995. 25. Ruiz-Garcia L, Barreiro P, Robla JI, Lunadei L. Testing ZigBee motes for monitoring refrigerated vegetable transportation under real conditions. Sensors . 2010;10(5):4968-4982. doi:10.3390/s100504968. 26. Kutt H, Mithel B. Studies on compressive strength of corrugated containers. Tappi . 1968;51(4):A79. 27. Gray-Stuart E. Unpublished data — Pallet transfer trial of dairy products in refrigerated shipping container. 2018. 28. Lukasse L and Leentfaar G, Humidity control and fresh air exchange in reefer containers: lowest feasible relative humidity, temperature and energy consumption. 2020. 29. Singh SP. Instability of stacked pallet loads due to misalignment. Journal of Testing and Evaluation . 1999;27(5):349-354. doi:10.1520/JTE12236J. 30. Baker MW. Effect of pallet deckboard stiffness and unit load factors on corrugated box compression strength. Virginia Tech . 2016;29(4-5): 263-274. doi:10.1002/pts.2201. 31. Quesenberry C, Horvath L, Bouldin J, White MS. The effect of pallet top deck stiffness on the compression strength of asymmetrically supported corrugated boxes. Packaging Technology and Science . 2020; 33(12):547-558. doi:10.1002/pts.2533. 32. Byrd V, Koning Jr J. Corrugated fiberboards: edgewise compression creep in cyclic relative humidity environments [Southern pine pulps]. Tappi [Technical Association of the Pulp and Paper Industry], 1978. 33. Popil RE, Hojjatie B. Effects of component properties and orientation on corrugated container endurance. Packaging Technology and Science . 2010;23(4):189-202. doi:10.1002/pts.889. 34. Niskanen K. Mechanics of Paper Products . Walter de Gruyter; 2011. How to cite this article: Gray-Stuart EM, Wade K, Redding GP, Parker K, Bronlund JE. Influence of different box preparations on creep performance of corrugated fibreboard boxes subject to constant and cycling relative humidity environments. Packag Technol Sci . 2022;35(6):497-504. doi:10.1002/pts.2646

ORCID Eli M. Gray-Stuart

https://orcid.org/0000-0002-0820-3131 https://orcid.org/0000-0002-7556-7752

John E. Bronlund

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PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ® Volume 9, Number 3, 2023

Angle of the Perforation Line to Optimize Partitioning Efficiency on Toilet Papers JOANA COSTA VIEIRA 1 , ANDRÉ COSTA VIEIRA 2 , MARCELO L. RIBEIRO 3 , PAULO T. FIADEIRO 1 & ANA PAULA COSTA 1 Currently, tissue product producers try to meet consumers’ requirements to retain their loyalty. In perforated products, such as toilet paper, these requirements involve the paper being portioned along the perforation line and not outside of it. Thus, it becomes necessary to enhance the behavior of the perforation line in perforated tissue papers. The current study aimed to verify if the perforation line for 0° (the solution found in commercial perforated products) is the best solution to maximize the perforation efficiency. A finite element (FE) simulation was used to validate the experimental data, where the deviations from the experiments were 5.2% for the case with a 4 mm perforation length and 8.8% for a perforation of 2 mm, and optimize the perforation efficiency using the genetic algorithm while considering two different cases. In the first case, the blank distance and the perforation line angle were varied, with the best configuration being achieved with a blank distance of 0.1 mm and an inclination angle of 0.56°. For the second case, the blank distance was fixed to 1.0 mm and the only variable to be optimized was the inclination angle of the perforation line. It was found that the best angle inclination was 0.67°. In both cases, it was verified that a slight inclination in the perforation line will favor partitioning and therefore the perforation efficiency. Contact information: 1 Fiber Materials and Environmental Technologies (FibEnTech-UBI), Universidade da Beira Interior, R. Marquês D’Ávila e Bolama, 6201 -001 Covilhã, Portugal 2 Center for Mechanical and Aerospace Science and Technologies (C-MAST-UBI), Universidade da Beira Interior, R. Marquês D’Ávila e Bolama, 6201 -001 Covilhã, Portugal 3 Department of Aeronautical Engineering, University of São Paulo, Av. João Dagnone, 1100-Jardim Santa Angelina, São Carlos 13563-120, SP, Brazil Eng 2023, 4, 80 – 91.

https://doi.org/10.3390/eng4010005 Creative Commons Attribution 4.0 License

Article 2 – Tissue Perforation Optimisation

Page 1 of 13

Article Angle of the Perforation Line to Optimize Partitioning Efficiency on Toilet Papers Joana Costa Vieira 1, * ,Andr é Costa Vieira 2 , Marcelo L. Ribeiro 3 , Paulo T. Fiadeiro 1 and Ana Paula Costa 1

1 Fiber Materials and Environmental Technologies (FibEnTech-UBI), Universidade da Beira Interior, R. Marqu ê s D’ Á vila e Bolama, 6201-001 Covilh ã , Portugal 2 Center for Mechanical and Aerospace Science and Technologies (C-MAST-UBI), Universidade da Beira Interior, R. Marqu ê sD’ Á vila e Bolama, 6201-001 Covilh ã , Portugal 3 Department of Aeronautical Engineering, University of S ã o Paulo, Av. Jo ã o Dagnone, 1100-Jardim Santa Angelina, S ã o Carlos 13563-120, SP, Brazil * Correspondence: joana.costa.vieira@ubi.pt Abstract: Currently, tissue product producers try to meet consumers’ requirements to retain their loyalty. In perforated products, such as toilet paper, these requirements involve the paper being portioned along the perforation line and not outside of it. Thus, it becomes necessary to enhance the behavior of the perforation line in perforated tissue papers. The current study aimed to verify if the perforation line for 0 ◦ (the solution found in commercial perforated products) is the best solution to maximize the perforation efficiency. A finite element (FE) simulation was used to validate the experimental data, where the deviations from the experiments were 5.2% for the case with a 4 mm perforation length and 8.8% for a perforation of 2 mm, and optimize the perforation efficiency using the genetic algorithm while considering two different cases. In the first case, the blank distance and the perforation line angle were varied, with the best configuration being achieved with a blank distance of 0.1 mm and an inclination angle of 0.56 ◦ . For the second case, the blank distance was fixed to 1.0 mm and the only variable to be optimized was the inclination angle of the perforation line. It was found that the best angle inclination was 0.67 ◦ . In both cases, it was verified that a slight inclination in the perforation line will favor partitioning and therefore the perforation efficiency.

Keywords: FE model; optimization; perforation efficiency; perforation line angle; tissue toilet paper

Citation: Vieira, J.C.; Vieira, A.C.; Ribeiro, M.L.; Fiadeiro, P.T.; Costa, A.P. Angle of the Perforation Line to Optimize Partitioning Efficiency on Toilet Papers. Eng 2023 , 4 , 80–91. https://doi.org/10.3390/ eng4010005

1. Introduction At the present time, there is a need for products that result in the use of less disposable material by environmentally conscious consumers. In the tissue paper converting industrial process, this has encouraged manufacturers to produce products with the ability to be partitioned [1]. In the production of finished tissue paper products, such as facial papers, paper towels and toilet papers, transversal perforation lines are used to facilitate the separation of the roll into individual “sheets” or services needed by the consumer. This feature of perforation allows the consumer to conveniently dispense a certain amount of the product according to their convenience [2]. Perforation takes place in the tissue paper converting machine when the sheet of paper passes through a nip between a stationary anvil and the perforator blades. These blades are usually mounted on a rotating cylinder and have alternately spaced teeth and notches. Both the anvil and the perforator are skewed in the machine direction (MD) to decrease the impact of the blade against the anvil by reducing vibration and keeping the cut line perpendicular to the MD of the tissue paper sheet. It is important that the perforator blades produce the desired cut in the finished product, so that consumer acceptance is as intended. The quality of the product cannot be affected by this operation due to poor distribution or the type of perforations. On the other hand, there has to be a balance between the number of cuts, the dimension of the cuts, the number of

Academic Editor: Antonio Gil Bravo

Received: 23 November 2022 Revised: 19 December 2022 Accepted: 20 December 2022 Published: 1 January 2023

Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Eng 2023 , 4 , 80–91. https://doi.org/10.3390/eng4010005

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