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Hemp hurd fiber, a low-value waste stream from the hemp industry, has potential downstream applications as an alternative to non-renewable plastics for single-use food service ware and packaging applications. Packaging paper substrates made from chemically pulped hemp hurd, mixed in varying ratios with bleached thermomechanical radiata pine pulp were developed and tested. Handsheets were characterized using several mechanical property tests including tensile strength, tearing resistance, burst strength, short-span compression, ring crush, together with Gurley air resistance, contact angle, and Cobb60 tests. Generally, addition of hemp hurd fibers significantly improved handsheet mechanical properties. Hot-pressing of the handsheets so as to approximate molded fiber thermoforming further enhanced their performance, with pure hemp hurd handsheets having the highest mechanical properties and barrier performance. A prototype was successfully thermoformed from hemp fiber, demonstrating overall feasibility of this fibre source for molded fibre objects. [ABSTRACT FROM AUTHOR]

Chemical crosslinking is an established method for improving the wet performance of paper. In the chemical crosslinking process, covalent bonds are formed between cellulosic surfaces. The formed intra- and interfiber bonds increase the paper's wet strength and reduce its water absorptivity. The majority of published studies concern crosslinking treatments with glyoxal, citric acid (CA), or with 1,2,3,4-butanetetracarboxylic acid (BTCA). The most severe disadvantage of the crosslinking treatments with glyoxal, CA, and BTCA is that the formed crosslinks make the fibers and the paper more brittle. This downside effect has largely impeded the utilization of crosslinking in paper and paperboard making. In the present study, handsheets made from Nordic bleached softwood kraft pulp (NBSK) were crosslinked with methylated 1,3-dimethylol-4,5-dihydroxyethylene urea (mDMDHEU), which is commonly used in cotton fabric finishing. Similar to using glyoxal and citric acid, crosslinking with mDMDHEU notably increased the handsheet wet strength and decreased the water absorption. Compared to the use of glyoxal or CA, the crosslinking with mDMDHEU did not make the handsheets that brittle. These results suggest that mDMDHEU could be a more viable crosslinking agent for improving the wet performance of paper products. [ABSTRACT FROM AUTHOR]

The overall usefulness of the bursting energy absorption (BEA) was studied for a better analysis of paper strength properties. Additionally, the changes of the BEA during more complex deformations of paper products, e.g., preliminary or simultaneous tensile and burst, were determined. For the purpose of the research, an experimental setup was designed. The results showed that the correlation between BEA and bursting strength was linear, but the proportionality strongly depended on paper grade. Thus, a more accurate method to characterize the bursting resistance (BR) of paper was proposed. The BR parameter is described by the three following parameters: average bursting strength, average bursting energy absorption, and the slope of the fitted linear regression curve (relationship between the bursting energy absorption and the bursting strength). This method revealed new mechanical behaviors of papers related to their preloading. [ABSTRACT FROM AUTHOR]

During the embossing process, a fiber sandwich is compressed between embossing tools. The use of ultrasound causes a short-term increase in the material temperature in addition to causing plastic deformation. The combination of the material compression and an increase in material temperature leads to structural changes, which can be observed by the change in mechanical properties of the cardboard. This work investigated the influence of an ultrasonically induced temperature increase on the structural changes of cardboard. Using three-parameter combinations, different temperature levels were achieved with a material densification of less than 5%. Subsequently, the samples were subjected to selected physical and visual analyses to characterize the change in the fiber structure. With the increase of 124 °C material temperature there was a decrease of about 15% in the splitting resistance and 10% in the bending stiffness. [ABSTRACT FROM AUTHOR]

Hydroxypropyl methylcellulose (HPMC)-coated papers without plasticizer and plasticized with polyols were prepared, and the effects of coating weight, different plasticizers (glycerol (GLY), sorbitol (SOR), and polyethylene glycol (PEG)), and plasticizer contents (20% to 50%) on the physical and mechanical properties of the resulting biopolymer-coated papers were studied. Coating weight was the most important factor affecting mechanical properties. Conversely, increasing coating weight led to a decrease in gloss and to an increase in tensile strength (TS), elongation at break (%E), and tearing resistance of coated papers. The application of unplasticized HPMC coatings (3 g/m²) on paper reduced water vapor permeability (WVP) and water absorption capacity by 25% as compared with uncoated paper. All plasticizers significantly (p < 0.05) increased WVP and Cobb60 values of the films. With the exception of PEG, no effect was found with plasticizers on TS and %E of coated papers compared with those without plasticizer. HPMC-coated papers with PEG as a plasticizer showed significantly lower TS and higher %E and tearing resistance than the other plasticized films (p < 0.05). HPMC coating improved tensile properties and tearing resistance of paper and could be regarded as a reinforcement layer. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the influence of acetylation on properties of paper made using the chemi-mechanical pulp (CMP) process. Industrial unbleached CMP pulp was provided (before and after refining), and paper handsheets were made. After drying, the specimens were acetylated on a heated cylinder at 120 °C, with acetic anhydride without catalyst. Physical and mechanical properties including water absorption, porosity, printability, brightness, D-folding, breaking length, tear resistance, and burst strength of samples were measured and compared between treated samples and the controls. The results showed that acetylation intensity was increased by increasing reaction time. Water absorption exhibited a significant reduction due to acetylation. Brightness, D-folding, and burst showed an increasing trend as a function of the degree of acetylation. Tear resistance was decreased by acetylation. The refining process improved acetylation and decreased porosity. The results indicated that most of the important factors were significantly influenced and improved by both acetylation and the refining process. [ABSTRACT FROM AUTHOR]