Biodegradation properties and thermogravimetric analysis of 3D braided flax PLA textile composites

Recent advances in the development and application of bio-based (natural fiber and biopolymer) composites are gaining broad attention because the resulting polymer completely degrades and does not release harmful substances. In this study, natural fiber 3 D braided yarn textile PLA (Polylactic acid) bio-composites are developed by film sequencing followed by hot-press compression molding. Bio-deterioration and thermal stability of the composites are analysed for storage, machining, transportation, and in-service uses in different environmental conditions (compost and thermal). Composite samples with different fiber wt.% (0, 22, 44) are exposed to compost soil. Tensile testing is performed under different configurations to characterise the tensile properties. Prepared bio-composite specimens are evaluated for weight loss and reduction in tensile properties over soil burial time, to observe the rate of biodegradation of braided yarn textile bio-composites. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) is employed to analyse the biodegradability of the composites. To study the thermal stability of the prepared bio-composites thermogravimetric (TG) analysis is carried out. Results showed that biodegradability, tensile properties and thermal stability of the composites are enhanced significantly with the reinforcement of 3 D braided yarn fabric.

NUMERICAL SIMULATION OF THERMOLUMINESCENCE QUARTZ PARTICLE

One of the widely used methods for studying minerals is the thermoluminescent (TL) method, which is used to date Quaternary sedimentary rocks. Usually, the difficulty in using TL dating is the lack of information about the structure of the mineral used in the experiment. For reliable interpretation of experimental data, the authors applied the digital twin method. In this case, all stages of the transformation of the mineral used are modeled from its burial in sedimentary rocks to the stimulation of the TL-signal splash in it under laboratory conditions on special installations, taking into account the unevenness heat transfer inside the sample of this mineral. The paper presents the results of numerical simulation of the TL signal from a spherical particle of natural quartz. The modeling was carried out in two stages. At the first stage, the influence of the burial time of quartz in the sedimentary rocks on its TL signal was determined. For this, the problem was posed of the accumulation of the crystal lattice quartz, information about the time of its presence in the natural radiation field. At the second stage, the TL signal from a spherical particle was simulated, which was heated in an experimental setup from the surface according to a linear law. It was found that, firstly, the burial time of quartz affects the shape of the TL-curve and, therefore, the mineral is applicable for dating. Secondly, it is necessary to control the heating mode of the quartz sample, since at high heating rates, heat transfer irregularities are significant for particles with a large radius. It also affects the shape of the TL signal and, as a result, can make it difficult to obtain age definitions or distort them. To assess the effect of non-uniformity of heat transfer, a dimensionless similarity parameter was proposed, which connects the radius of the particles and the heating rate.

Effect of Rubberwood Content on Biodegradability of Poly(butylene succinate) Biocomposites

Poly(butylene succinate) (PBS) biocomposites incorporated with rubberwood powder (RWP) were fabricated with various RWP weight fractions (i.e., 0 to 40% wt) by injection moulding process. The soil burial test was employed to examine the biodegradability of such biocomposites under outdoor environment for 60 days. The physical appearance, percentage weight loss, chemical structure, and mechanical properties before and after the soil burial test were determined. Apparent changes in physical appearance of the biocomposites from optical micrographs were detected in terms of surface morphology and colour. The percentage of crystallinity of PBS/RWP biocomposites was studied by the X-ray diffraction (XRD) technique, and the XRD pattern revealed a decrease in percentage of crystallinity due to enhancing RWP weight fractions. This may be attributed to a presence of rubberwood powders providing more disordered molecular chain arrangement of PBS matrix and also an agglomeration of the rubberwood powder content at greater concentration as seen in SEM micrographs. With increasing RWP weight fractions and burial time, the results exhibited a considerable change in chemical structure (essentially ester linkage due to biodegradation mechanism of PBS), relatively greater percentage weight loss, and a substantial decrease in flexural properties. Consequently, the results indicate that incorporating RWP enhances biodegradability of PBS/RWP biocomposites; that is, the biodegradation rate of biocomposites increases with increasing RWP weight fractions and burial time.

Effect of Soil Burial on Tensile Properties of Polypropylene/Plasticized Cassava Starch Blends

Polypropylene (PP)/plasticized cassava starch (PCS) blended with and without compatibilizer (polypropylene-graft-maleic anhydride (PP-g-MA)) via melt blending were prepared for soil burial which lasted for 90 days. Plasticized starch loadings of 0, 10, 20, 30, 40, and 50 wt.% were used, while pp-g-ma was used at 10 wt.% based on starch weight. The PP/PCS and PP/PCS/PP-G-MA blends were evaluated for their tensile properties. It was observed that the tensile strength, elongation at break, and young’s modulus decreased with increases in soil burial time as well as starch content for PP/PCS blends. Similar treads for the tensile properties were observed for PP/PCS/PP-g-MA, but with higher properties as compared to uncompatibilized blends. However, the tensile properties for both PP/PCS and PP/PCS/PP-g-Ma decrease with increases in starch loading and also as the burial period progressed.

Chemotaxonomical identification of Holocenic bogwood recovered after 2007 Niigataken Chuestsu-oki Earthquake

A Holocenic coniferous bogwood salvaged from the 70 to 100 m-deep seabed after the 2007 Niigataken Chuetsu-oki Earthquake was analyzed anatomically and chemically. The main anatomical features of the wood were the presence of (i) large window-like pits in cross field and (ii) smooth-walled cells of ray tracheid. Feature (i) allowed identification of the wood as genus Pinus. Feature (ii) is characteristic of section Quinquefoliae, but possible decay by the long burial (3400–3210 cal BP) left the identification inconclusive. Chemical analysis showed that the major volatile components of the bogwood were cadinane-type sesquiterpenes. In contrast, those of modern pine samples were longifolene and monoterpenes from Pinus densiflora and Pinus thunbergii, nerolidol from Pinus parviflora and P. parviflora var. pentaphylla, and monoterpenes from Pinus koraiensis. Thus, none of the modern pines contained cadinane-type sesquiterpenes as major components. As organic components of wood are known to undergo diagenetic transformation under geological conditions, recent samples were subjected to heat treatment at 180°C for 24 h to simulate the long burial time. As a result, nerolidol, the main component of P. parviflora and P. parviflora var. pentaphylla was converted to cadinane-type sesquiterpenes. Therefore, it is highly likely that the bogwood sample was P. parviflora or P. parviflora var. pentaphylla, section Quinquefoliae subsection Strobus, agreeing with the anatomical feature of section Quinquefoliae.

Infrared spectroscopic study of modern and ancient ivory from sites at Jinsha and Sanxingdui, China

Ancient ivory, from the Chengdu Jinsha and Guanghan Sanxingdui sites in China, has been buried for several thousand years. In order to determine the degradation mechanisms and to provide a scientific basis for protecting them, these ancient ivory samples have been compared with modern ivory using infrared spectroscopy in the frequency range 400–4000 cm–1. By combining chemical analysis data we compare the crystallinity and crystal chemistry of the apatite component, as well as the structural characteristics of the ivory. These investigations showed that the ancient ivory consists almost entirely of hydroxyl-carbonate apatite as the predominant phase. Compared with the modern ivory, the PO43– and CO32– bands are stronger, the PO4RF values are obviously greater, and an extra OH– band at 3569 cm–1 is observed in the ancient ivory. These results indicate that there is a greater degree of apatite crystallinity in the ancient ivory and also imply that there has been incorporation and recrystallization of CO32– in the apatite during burial. Positive correlations have been found between the apatite crystallinity, CO32– and OH– ion contents, and burial time. The organic matter in ancient ivory has been lost or decomposed as the organic bands (e.g. at 1238 cm–1 and 1337 cm–1) have disappeared. This may be the main reason that ancient ivory is easily dewatered and readily friable after being unearthed.

Taphonomy, palaeoecological implications, and colouration of Cambrian gogiid echinoderms from Guizhou Province, China

Based on rich material (381 specimens examined) from two Cambrian echinoderm faunas, the early Cambrian Balang fauna and middle Cambrian Kaili fauna in Guizhou Province, South China, the taphonomy of gogiid echinoderms is described in detail, and the preservation of stereomic microstructure and organic remains of Cambrian gogiid echinoderms is reported here for the first time. Taphonomic considerations include entombment patterns, decay sequences, individual-specific diagenetic histories, unusual burial postures, selective disarticulation patterns, and post-mortem elongation. In particular, five categories of gogiid entombment patterns are proposed to describe the multi-directional orientations recorded at the burial time of articulated gogiids. Gogiid-bearing slabs of Guizhou material primarily (70%) display the type 2 entombment pattern (articulated gogiids preserved with fan-shaped brachioles); thus, most Guizhou gogiids were buried with brachioles preserved in feeding posture during obrution events. Balang gogiid faunas contain the oldest evidence of palaeoecological interactions among echinoderms and other indigenous taxa. In addition to pre-burial and post-burial decay, other potential causes for unusual disarticulation patterns exhibited by the gogiids from the lower Cambrian Balang Formation include pre-burial bio-disturbance and post-burial bioturbation based on ichnogenera, including Rusophycus and Planolites. Chemical analyses reveal that carbon, calcium, manganese and iron are the major elements responsible for the variety of colours exhibited by Guizhou gogiids. Three-dimensional stereomic microstructure (mean stereom pore size = 8.4–8.7 μm; average trabecular thickness = 4.5–4.6μm) occurs on the external surfaces of thecal plates in two gogiid species. Stereom preservation in calcite suggests that the dissolution of calcareous echinoderm plates, yielding characteristic mouldic preservation, is sub-Recent (after lithificaiton and exposure of gogiid-bearing, marine sedimentary successions on or near the land surface).