On the Network Strength of Meta-Aramid Fiber Suspension and Its Relationship to Formation

Because of poor surface hydrophilicity, meta-aramid fibers readily form flocs by intertwining or interlacing, and this severely affects the uniformity of meta-aramid paper. To investigate the flocculation mechanism of meta-aramid fiber suspensions, the critical flocculant concentration, shear, and compressive network strength of meta-aramid fiber suspensions were examined. A hand sheet former was used to study the influence of the yielding properties of suspensions on the uniformity of meta-aramid paper, and the relationship between the formation index and rheological properties was determined. The results showed that the critical gel concentration ranged from 0.37 to 0.68 g/L, which was much lower than that of plant fiber suspensions. In addition, the compressive yield stress ( P y ) and shear yield stress ( τ y ) of the meta-aramid fiber suspensions were found to increase linearly and exponentially, respectively, with an increasing concentration, and the uniformity index of the paper sheets was found to depend on a power of τ y ⋅ P y . This provides an effective method for predicting paper sheet uniformity.

Taguchi based fuzzy logic model for optimisation and prediction of surface roughness during AWJM of DRCUFP composites

From last two decades, plant fiber reinforced polymer/polyester composites have been effectively used in structural and automotive applications. Researchers and manufacturers are looking forward for an effective utilization of these composites. However, despite the outstanding properties in terms of load bearing capacity and environmental sustainability of plant fibers the uptake of these composites are limited due to its poor machinability characteristics. Hence in this paper, Taguchi based fuzzy logic model for the optimization and prediction of process output variable such as surface roughness during Abrasive Water Jet Machining (AWJM) of new class of plant fiber reinforced polyester composites i.e., Discontinuously Reinforced Caryota Urens Fiber Polyester (DRCUFP) composites has been explored. Initially machining experiments has been carried out using L27 orthogonal array obtained from Taguchi Design of Experiments (TDOE). Finally, Taguchi based fuzzy logic model has been developed for optimisation and prediction of surface roughness. From the extensive experimentation using TDOE it was observed that the optimum cutting conditions for obtaining minimum surface roughness value, water pressure (A): 300 bar, traverse speed (B): 50 mm, stand of distance: 1 mm, abrasive flow rate: 12 g/s, depth of cut (C): 5 mm and Abrasive Size:200 microns. Further from FLM, it is observed that minimum water pressure (A): 100 bar, traverse speed (B): 50 mm, stand of distance: 1 mm, abrasive flow rate: 8 g/s, depth of cut (C): 5 mm and abrasive size:100 microns gave higher surface roughness values (3.47 microns) than that at maximum water pressure (A): 300 bar, traverse speed (B): 150 mm, stand of distance: 4 mm, abrasive flow rate: 12 g/s, depth of cut (C): 15 mm and abrasive size:200 microns the surface roughness values (3.25 microns).

Scientific Analysis and Conservation Treatment on the Buddhist Scriptures of Paper Relics Excavated from Sum Tolgoi, Mongolia

This study analyzed the composition and structure of materials with Buddhist paper scriptures excavated from architectural sites in ‘Sum Tolgoi’ of the 17th century and carried out conservation treatment base on the result of the analysis. The scriptures were covered in dust and foreign sub stances, and were so crumpled that it was impossib le to identify the form. The damage, loss, and discoloration have been identified. Buddhist scriptures written in Tibetan used indigo and ink sticks on paper as a result of UV-Vis analysis, and ink sticks as black character materials from scriptures written ancient Mongolian. SEM-EDS and Micro-XRF analyses revealed that the outlines were drawn with red lines using a mix of Minium (Pb3O4) and Cinnabar (HgS), or Cinnabar (HgS) alone, and the contents of the scriptures were written with silver paint. Silver chloride (AgCl) and Calcium (Ca) were identified in the silver paint component of the characters, while Calcium and Orpiment (As2S3) were identified in the yellow lines. Concerning the paper ground, Buddhist scriptures written in ancient Mongolian were characterized by herbal plant fiber and bast fiber, and those written in Tibetan, by bast fiber. Radiocarbon dating indicates that the paper for the scriptures was produced b etween the 15th and 17th centuries. Conservation treatment of the scriptures was carried out based on the experiment on the production of pre-coated paper and how to coat that to prevent the second damage due to the deformation and fragility of the excavated paper. The scriptures were preserved and mounted, and a neutral box was made to identify the contents of the scriptures recorded on both sides after the treatment. This conservation treatment is the result of a study that applied new conservation treatment materials and methods according to the principle of conservation treatment reversibility.

Safety Risks of Plant Fiber/Plastic Composites (PPCs) Intended for Food Contact: A Review of Potential Hazards and Risk Management Measures

Plant fiber/plastic composites (PPCs), with the benefits of low cost and easy processing, have been widely used in the production of various food contact products. They are generally considered to be economical and environmentally friendly because of their natural raw materials (plant fibers) and recommended to be one of the ideal alternatives to traditional petrochemical-based plastics. However, in addition to plastic resins and plant fibers, some indispensable additives are involved in the production process of PPCs, which may pose food safety risks. To date, excessive migration of hazardous substances (such as melamine) has been reported in some products made of PPCs, and the safety and applicability of PPCs as food contact materials need to be further studied. In this paper, the main raw materials of PPCs used for food contact are taken as the pointcut to analyze the possible hazards, sources of hazards, and existing risk management measures in various countries. The conclusion shows that PPCs used for food contact may have potential safety risks at present. However, systematic research on migration methods and safety assessment are still insufficient, and further studies are needed regarding the main safety risks and migration patterns.

Preparation and Freeze-Thaw Resistance of Geopolymer-Based Natural Plant Fiber Composites

Slag, alkaline activator solution and straw fibers were used to manufacture geopolymer-based natural plant fiber composites. In this study, three influences of water glass modulus, fiber content and water-binder ratio on bending strength were studied by orthogonal experiment and single factor analysis. The results indicate that the order of the factors affecting the bending strength is: water-binder ratio > fiber content > water glass modulus. When the water-binder ratio is 0.4, the fiber content is 12%, and the water glass modulus is 1.9, the bending strength of composite is up to 9.1MPa, which exceeds the standard requirements (9MPa) for qualified products specified in the standard (GB/T 24312-2009). The SEM and appearance of specimens indicate that the geopolymer-based natural plant fiber composites have good freeze-thaw resistance.

Eco-Friendly Chitosan@Silver/Plant Fiber Membranes for Masks with Thermal Comfortability and Self-Sterilization

The surgical masks have been essential consumables for public in the COVID-19 pandemic. However, long-time wearing masks will make wearers feel uncomfortable and massive discarded non-biodegradable masks lead to a heavy burden on our environment. In this paper, we adopt degradable chitosan@silver (CS@Ag) core-shell fibers and plant fibers to prepare an eco-friendly mask with excellent thermal comfort, self-sterilization, and antiviral effects. The thermal network of CS@Ag core-shell fibers highly improves the in-plane thermal conductivity of masks, which is 4.45 times higher than that of commercial masks. Because of the electrical conductivity of Ag, the fabricated mask can be electrically heated to warm the wearer in a cold environment and disinfect COVID-19 facilely at room temperature. Meanwhile, the in-situ reduced silver nanoparticles (AgNPs) endow the mask with superior antibacterial properties. Therefore, this mask shows a great potential to address the urgent need for a thermally comfortable, antibacterial, antiviral, and eco-friendly mask.