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The effects of heat-assisted vat photopolymerization (HVPP) on the physical and mechanical properties of 3D-printed dental resins, including the morphometric stability of 3D-printed crowns, were investigated. A resin tank was designed to maintain the resin at 30, 40, and 50 ℃ during the 3D printing process. Test specimens were fabricated using a commercial dental resin, with untreated resin serving as the control group. Key properties such as viscosity, curing kinetics, surface microhardness, flexural properties, and dimensional accuracy were evaluated. The viscosity of the resin decreased significantly (P < 0.05) with increasing temperature, thereby enhancing its flow properties. Photo-DSC analysis revealed a 17.58% increase in peak heat flow at 50 ℃, indicating accelerated polymerization. Surface microhardness improved significantly (P < 0.05) with HVPP, though a slight reduction was observed at 50 ℃ compared to that at 30 and 40 ℃. The flexural strength, modulus, and resilience were significantly enhanced (P < 0.05) at higher temperatures, with 50 ℃ yielding the best mechanical properties. However, 3D morphometric analysis showed increased root mean square deviation from the CAD design at elevated temperatures. Our results suggest that HVPP enhances the durability of dental prostheses, although careful optimization of the printing temperature is essential to balance their strength and accuracy. [ABSTRACT FROM AUTHOR]

We describe a new species, Diacheopsis resinae (Myxomycetes), collected from a microhabitat new for myxomycetes: stem wounds of coniferous trees (Norway spruce) where the resin is overgrown with a community of resinicolous fungi. The 80 known collections come from the Vosges (France), the Black Forest (Germany), Swabian Alp (Germany), and several localities in Denmark and Norway. Observations, but as well as metabarcoding of substrate samples with fungal (ITS [internal transcribed spacer]), bacterial (16S rDNA), and myxomycete (18S nuc rDNA) primers from eight trunks, revealed the new myxomycete to co-occur with resin-degrading ascomycetes (Infundichalara microchona, Lophium arboricola, Zythia resinae). The gram-negative bacterial genera Endobacter and Sphingomonas were found to be abundant in the substrate and may be a food source for the myxomycete. Fruit bodies were found mostly during the more humid winter season, with a peak in January/February. Partial sequences of two independent molecular markers (18S nuc rDNA, EF1α [elongation factor 1-alpha] gene) were obtained for 41 accessions, which form a monophyletic cluster in a two-gene phylogeny of Stemonititidales but do not group with other species of Diacheopsis, thus rendering this genus paraphyletic. The new species, although exclusively developing sessile sporocarps and morphologically undoubtedly falling into the genus Diacheopsis, is most closely related to species of Lamproderma, especially L. album, L. zonatum, and L. zonatopulchellum. Within D. resinae, three groups can be differentiated, which show nearly complete reproductive isolation, as judged from a recombination analysis of the two unlinked markers and the allelic combinations of the EF1α gene. [ABSTRACT FROM AUTHOR]

Conventional multi-material multi-layer flexible packaging offers excellent properties. However, it has recycling challenges, necessitating a shift to mono-material multi-layer flexible packaging for example all-polyethylene (PE) packaging which can be tailored through various synthesis and processing methods for different layers. In this work, we study how the key molecular properties (number-average molecular weight (M n), weight-average molecular weight (M w ), molecular weight distribution (MWD), comonomer content (short chain branching)) and machine direction orientation (MDO) process draw ratio (MDX) influence the final morphology and mechanical properties of MDO-PE films which are intended as the outer layer of mono-material all-polyethylene multi-layer flexible packaging. Five PE grades and various blends were extruded and blown into films. Selected blown films were machine direction oriented to obtain the final MDO-PE films. Furthermore, one selected PE blown film was processed at different MDO process draw ratios while keeping other process parameters constant. From the molecular properties point of view, the higher molecular weight fractions provide a higher possibility for uniform stretching whereas lower molecular weight fractions provide a higher natural draw ratio and therefore higher modulus and stiffness enhancement. Further, the results show that increasing MDO process draw ratio leads to more fibrillation and increased crystallinity. Consequently, the tensile modulus and stiffness at the higher draw ratios increase as well and are comparable to conventionally used polymers in outer layers of multilayer flexible packaging. Thus, this work demonstrates that MDO-PE films with enhanced modulus can provide sufficient stiffness for the design of outer layer of mono-material multi-layer all-PE packaging which presents higher potential for mechanical recyclability. [ABSTRACT FROM AUTHOR]

The main objective of this work is to develop a robust cost-effective in-house coded non-dominated sorting differential evolution (NSDE) algorithm to optimize the thermal-cure process through the minimization of part thickness thermal gradients and cure time of glass fibre-vinyl ester-based automotive bonnet and a carbon fibre-RTM6-based aircraft wing flap composite parts. The efficacy of the proposed algorithm was examined with the in-house coded NSGA-II and trial and error process simulations in terms of thermal gradient, cure time, and cure progression at the applied temperature cycles. At first, the NSDE and NSGA-II algorithms were developed for the simultaneous minimization of thermal gradients and cure time. Subsequently, the optimized thermal-cure profiles were obtained from trial-error simulations by manually changing the mould heating parameters. From the results, NSDE algorithm was found to be effective in achieving faster convergence with less cure process and computational time when compared to the NSGA-II algorithm. The NSDE algorithm performed effectively in terms of thermal gradient and cure time with the automated predictions of the mould heating parameters when compared with the trial and error process. From the results, the NSDE algorithm predicted a lower thermal gradient of 0.0008 K and 0.0022 K as well as cure times of 40 min and 35 min for the bonnet and wing flap parts, respectively. [ABSTRACT FROM AUTHOR]

Polyoxamides are a class of polyamides that exhibit superior mechanical, chemical, UV light resistance, and low water absorption properties than their conventional counterparts. In this study, a novel in-situ spray polycondensation techniques is developed and used to impregnate poly (pentamethylene oxamide) (PA52) prepolymer into carbon fibers (CF). The prepolymer impregnated CFs are subjected to solid state polycondensation to increase the molecular of PA52 resin thus obtain prepregs for fabrication of carbon fiber reinforced polyoxamide composites. The effects of preparation parameters on the mechanical properties of PA52/CF composites are studied and reported. The results showed that, PA52/CF composites prepared at molding temperature of 325°C, pressure of 3.0 MPa, and time of 10 min exhibits good tensile strength at break, flexural strength, and interlaminar shear strength (ILSS) of 435 MPa, 364 MPa, and 51 MPa, respectively. SEM results suggest good adhesion between the PA52 and CF which is supported by the high storage modulus results obtained from dynamic mechanical analysis (DMA) results, depicting the potential of in-situ spray impregnation in preparation of carbon fiber reinforced polyoxamide composites. [ABSTRACT FROM AUTHOR]

In this work, the effects of different fiber wettability on resin impregnation during vacuum assisted resin transfer molding (VARTM) process and subsequent interface properties were comprehensively investigated. The fabrics with different surface morphology and wettability were successfully obtained via tuning the concentration of epoxy sizing agents. Results indicate that a low void content of less than 1% is achieved with the improvement of fiber wettability. Additionally, the interlayer property of composites is significantly improved by ∼12%. It is attributed to improved impregnation and capillary number, achieved by optimizing the dual-scale flow of resin in the preform via reducing the contact angle. Achieving equilibrium of dual-scale flow is an important factor in minimizing voids within the CFRP laminate. Furthermore, the introduction of epoxy functional groups significantly enhances interfacial bonding, contributing to an increase in the interlaminar shear strength of CFRP composites. This improvement effectively improves stress concentration by dispersing crack propagation. The findings in this work provide significant information for designing CFRP composites with superior mechanical properties via adjusting fiber wettability. [ABSTRACT FROM AUTHOR]

Polymeric materials in the construction sector, together with inorganic and organic waste, are of great interest. Polymeric concretes have been prepared using a vinylester resin as a matrix and a combination of mineral (slate and granite) and organic (olive pits and hemp fibres) fillers, with the aim of studying the compatibility and the optimal dosages between the components, minimizing the amount of resin used and maximizing the mineral and organic waste. Scanning electron microscopy (SEM-EDX), X-ray diffraction (XRD) and X-ray fluorescence (WDXRF) have been used for the morphological, chemical and mineralogical characterization of the components and samples; hardness, compressive strength and flexural strength tests have been used to determine the mechanical properties. The results allow the adjustment of densification and mechanical behaviour. This will contribute to the valorization of agricultural and quarry waste, reduce the impact on the environment and improve production costs. [ABSTRACT FROM AUTHOR]

Old trees are remarkable for their ability to endure for centuries or even millennia, acting as recordkeepers of historical climate and custodians of genetic diversity. The secret to their longevity has long been a subject of fascination. Despite the challenges associated with studying old trees, such as massive size, slow growth rate, long lifespan and often remote habitat, accumulating studies have investigated the mechanisms underlying tree aging and longevity over the past decade. The recent publication of high-quality genomes of long-lived tree species, coupled with research on stem cell function and secondary metabolites in longevity, has brought us closer to unlocking the secrets of arboreal longevity. This review provides an overview of the global distribution of old trees and examines the environmental and anthropogenic factors that shape their presence. We summarize the contributions of physiological characteristics, stem cell activity, and immune system responses to their extraordinary longevity. We also explore the genetic and epigenetic 'longevity code', which consists of resistance and defense genes, DNA repair genes and patterns of DNA methylation modification. Further, we highlight key areas for future research that could enhance our understanding of the mechanisms underlying tree longevity., (© 2024 John Wiley & Sons Ltd.)