Water barrier properties of carboxymethyl cellulose/halloysite nanotubes nanocomposite to be used in food packaging applications

In this research, novel carboxymethyl cellulose (CMC) based nanocomposite film containing 5%wt of halloysite nanotubes (HNT) was fabricated via solvent casting method as a potential biodegradable packaging material. The performances of the nanocomposite packaging material was investigated by assessing the moisture content, moisture uptake, water solubility, water vapor barrier properties and opacity. The incorporation of 5%wt HNT into the film remarkably reduced the moisture uptake by ∼ 28.01% at 97% RH and 31.08% at 40% RH. Water permeability value of CMC/HNT film showed as 7.08 ± 0.26 × 10−11 gm/m2Pas at freezing, 3.37 ± 0.33 × 10−11 gm/m2Pas at refrigeration and 1.14 ± 0.00 × 10−11 gm/m2Pas at ambient environmental conditions respectively. Subsequent to the thermal annealing process, the water vapor permeation ability was drastically declined in the HNT added nanocomposite films at all three different conditions (freezing, refrigeration and ambient) due to enhancing the crystalline structure. Furthermore, the addition of nanofillers into the polymer matrix significantly induced the UV blocking property of the film. These findings disclosed that prepared CMC/5%HNT nanocomposite films can be a potential food packaging material.Keywords: barrier properties, carboxy methyl cellulose, halloysite nanotubes

Assessment of Extremely Cold Subarctic Climate Environment Destruction of the Basalt Fiber Reinforced Epoxy (BFRE) Rebar Using Its Moisture Uptake Kinetics

A quite simple method is proposed for the assessment of extremely cold subarctic climate environment destruction of the basalt fiber reinforced epoxy (BFRE) rebar. The method involves the comparison of experimentally obtained long-term moisture uptake kinetic curves of unexposed and exposed BFRP rebars. A moisture uptake test was carried out at the temperature of 60 °C and relative humidity of 98 ± 2% for 306 days. The plasticization can be neglected because of low-level moisture saturation (<0.41% wt.); the swelling and structural relaxation of the polymer network can be neglected due to the high fiber content of BFRP rebar; moisture diffusion into the basalt fibers can be neglected since it is a much lesser amount than in the epoxy binder. These assumptions made it possible to build a three-stage diffusion model. It is observed that an increase in the density of defects with an increase in the diameter of the BFRP rebar is the result of the technology of manufacturing a periodic profile. The diffusion coefficient of the BFRP rebar with a 6, 10, or 18 mm diameter increased at an average of 82.7%, 56.7%, and 30%, respectively, after exposure to the climate of Yakutsk during 28 months, whereas it was known that the strength indicators had been increased.

Evaluation of the mechanical characteristics of hygrothermally aged 2-D basalt-aramid/epoxy hybrid interply composites

Polymer composites used in outdoor applications are exposed to environmental factors such as temperature and moisture which may affect the mechanical performance of the composites. In this study, the influence of moisture absorption on the mechanical properties of basalt-aramid/epoxy hybrid interply composites were evaluated. Two different types hybrid interply composites were taken for the investigation namely (301 A/03 B/301 A) and (451 A/03B/451 A). Composites were prepared using compression molding process and cut specimens were subjected to three different ageing environments for 180 days. Selected ageing conditions are, (i) ambient temperature ageing (ii) Sub-zero temperature ageing (−10°C) and (iii) Humid temperature ageing (40°C and 60% Relative humidity). Mechanical tests of the aged composites were carried out to analyse the behaviour of the composites. Moisture uptake of the specimens follow Fick’s law of diffusion with saturation absorption of 5.44%, 3.12% and 1.80% for ambient, sub-zero and humid specimens respectively. Results revealed that (301 a/03 B/301 a) aged composites possess higher mechanical properties compared to (451 a/03 B/451 a) aged composites. Highest reduction in properties were observed in ambient aged specimens followed by humid and sub-zero specimens. Scanning electron microscopy (SEM) was employed to observe the damage modes of the fractured specimens. Matrix deterioration, micro cracks and fibre fracture were the major types of failures observed in aged laminates.

Experimental analysis of moisture uptake and dry-out in CLT end-grain exposed to free water

This paper presents the results of a series of laboratory tests of CLT end-grain moisture uptake and dry-out. We put CLT test details (TDs) in direct water contact from the end-grain edge and then left the TDs to dry for two weeks in the laboratory and in an outside shelter. Half of the TDs had their wet sides attached to another CLT detail. Fibre saturation point was quickly reached in the bottom part of the TDs during the seven-day water contact. A tendency of increasing moisture content (MC) was up to 90 mm from the wet edges, but we did not record MC levels above the critical level at that height. However, MC exceeded critical levels at 60 mm from the water level. The measured water absorption coefficient Aw was 3.51×10−3 kg/m2-s0’5. Drying was negligible for the TDs which were in contact with another CLT detail. Thus, moisture dry-out is very complicated in joints where the CLT end-grain is covered, such as the exterior wall to foundation or intermediate ceiling connection. The dry-out of CLT is not expected in a cold and humid outdoor environment once the CLT end-grain has absorbed moisture even with wet edges exposed to air.

Effects of Coefficient of Thermal Expansion and Moisture Absorption on the Dimensional Accuracy of Carbon-Reinforced 3D Printed Parts

Environmental effects—temperature and moisture—on 3D printed part dimensional accuracy are explored. The coefficient of thermal expansion of four different nylon materials was determined for XY and ZX print orientations, with 0°, 45°/−45°, and 90° infill patterns. Unreinforced nylon exhibited a thermal expansion coefficient of the same order regardless of condition (from 11.4 to 17.5 × 10−5 1/°C), while nylons reinforced with discontinuous carbon fiber were highly anisotropic, for instance exhibiting 2.2 × 10−5 1/°C in the flow direction (0° infill angle) and 24.8 × 10−5 1/°C in the ZX orientation. The temperature profile of a part during printing is shown, demonstrating a build steady state temperature of ~ 35 °C. The effect of moisture uptake by the part was also explored, with dimensional changes of ~0.5–1.5% seen depending on feature, with height expanding the most. The effects of moisture were significantly reduced for large flat parts with the inclusion of continuous fiber reinforcement throughout the part.

Torrefaction and Pelleting of Wheat and Barley Straw for Biofuel and Energy Applications

Microwave (MW)-assisted torrefaction and pelleting could enhance biomass fuel properties and energy applications. Plastic wastes are considered as a replacement source binder in pellets to minimize their effect on the environment as pollutants. High-density polyethylene (HDPE), an extractable plastic from recycling waste, was investigated as a binder for torrefied wheat and barley straw pellets. Fuel pellet characteristics, such as durability, density, tensile strength, and water absorption, were used to evaluate the pellets produced from a single pelleting test. The results showed that the addition of HDPE as a binder significantly increased the pellet quality in terms of density (686.12–982.93 kg/m3), tensile strength (3.68 and 4.53 MPa) for wheat and barley straw, and reduced ash content of the pellet from 10.34 to 4.59% for barley straw pellet and 10.66 to 3.88% for wheat straw pellets. The higher heating value (HHV) increased with increasing biochar mix and HDPE binder blend. The highest HHV value observed for barley straw was 28.34 MJ/kg, while wheat straw was 29.78 MJ/kg. The study further indicated that MW torrefaction of biomass-biochar mix with HDPE binder reduced the moisture adsorption of wheat and barley straw pellets, which can significantly improve their storage capability in humid locations. The moisture uptake ratio for MW-torrefied barley straw pellets was 0.10–0.25 and wheat straw pellets 0.11–0.25 against a moisture uptake ratio of 1.0 for untreated biomass. MW torrefaction of wheat and barley straw with biochar and HDPE binder addition during pelleting is a promising technique to improve biomass fuel pellet properties.

Mechanical and Hygroscopic Properties of Molded Pulp Products Using Different Wood-Based Cellulose Fibers

With an increasing interest for molded pulp product (MPP) in the industry, it is important to fully understand how the manufacturing process is different from papermaking. One specific way to differentiate the processes is to compare their resulting products. As the paper industry uses several wood fibers with various pulping processes, it is interesting to compare some of these fibers, to further progress our understanding of the MPP process. In this study, six different wood fibers were used (as received) and analyzed to obtain the sample with the lowest moisture uptake and highest tensile properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and fiber analysis module (MorFi) observations were performed, as well as moisture uptake measurements after sorption and tensile tests. We observed significant differences between the fibers tested. Kraft fibers (bleached softwood kraft pulp (BSKP), bleached hardwood kraft pulp (BHKP), and unbleached softwood kraft pulp (USKP)) showed smoother surfaces and less non-cellulosic molecules, such as hemicellulose, lignin, and pectin, in the SEM images. Bleached chemi-thermomechanial pulp (BCTMP) and recycled pulps (R-NPM and R-CBB) both showed non-cellulosic molecules and rougher surfaces. These results were confirmed with the FTIR analysis. With kraft fibers, MPP mechanical properties were lower than non-kraft fibers. Resulting moisture uptake is in between the recycled fibers (lowest moisture uptake) and BCTMP (highest moisture uptake). The removal of non-cellulosic molecules reduces the mechanical properties of the resulting MPP. The incorporation of non-wood molecules, as found in recycled fibers, also reduces the mechanical properties, as well as moisture uptake, when compared with BCTMP.