Superior Dimensional Stability Research Articles

Tailoring the mechanical properties of macro-porous PVA hydrogels for biomedical applications

Polyvinyl alcohol (PVA) is a biocompatible biopolymer with superior dimensional and mechanical stability when compared to naturally available biomaterials such as collagen and gelatin. Furthermore, PVA in hydrogel form behaves non-linearly during mechanical loading, generating a response like soft biological tissues. Generally, PVA hydrogels are fabricated using freeze-thaw cycles (FTCs) and changing the number of FTCs gives control over its mechanical properties. Porosity of the hydrogel is another important factor which determines its mechanical properties and is also evident in biological soft tissues. Incorporating macro-pores in PVA hydrogels substantially reduces the stiffness of the material and can mimic some porous tissues such as lung, liver, bone marrow, kidneys, urethra and penile tissues (corpus cavernosa). Within this study, we developed macro-porous PVA hydrogels using the freeze-thaw process followed by particulate leaching of sacrificial 3D-printed and milled PVA (m-PVA) filler particles. This fabrication method enables control over the porosity in macro-porous PVA hydrogels, which is crucial not only for tuning mechanical properties but also for mimicking the structure of spongy tissues, such as liver tissue and corpus cavernosum in the penile tissue, for example. We investigated the level of porosity in the specimen using optical microscopy to understand the distribution of the pores and the pore size. The tunability of the mechanical properties of PVA hydrogels is, a key finding of this study and is achieved using three factors: (i) weight percentage of sacrificial fillers, (ii) number of FTCs and (iii) concentration of PVA. These macro-porous PVA specimens have wide ranging biomedical applications as biological soft tissue analogues, or tissue engineering scaffolds, where the PVA hydrogel can be tuned to match the mechanical properties of these soft biological tissues.

Convenient synthesis of phthalonitrile‐containing mono‐benzoxazines with exceptional thermal stability and improved curing activity

AbstractSimple synthesis and high performance are eternal pursuit for polymers. To lower the curing temperature, lower the melt viscosity and improve the processability of high performance phthalonitrile resins, a solvent‐free method was applied to synthesize three from different phenols. Their chemical structure was confirmed by FTIR and NMR spectra, the curing behavior was investigated by DSC and rheology. It was found that the polymerization of phthalonitrile groups could be effectively promoted by benzoxazine moieties and the curing temperature of phthalonitrile groups dropped to around 240°C. Consequently, owing to the high curing reactivity, polymers obtained at relatively low curing temperature possessed high crosslinking density and extremely high thermal stability. P‐apn‐200, which was cured at 200°C, showed 5 wt% weightloss temperature (Td5) of 472°C and char yield (Yc) of 75.77% at 800°C. Moreover, the polymers obtained after curing at 280°C showed superior dimensional stability, CN‐apn‐280 showed extremely low linear expansion coefficient (CTE) of 10.7 ppm/°C. And mP‐apn‐280 showed HR capacity of 3.99 J/g‧K, peak HRR of 4.0 W/K and total HR of 0.8 kJ/g.

UV-Mediated Facile Fabrication of a Robust, Fully Renewable and Controllably Biodegradable Poly(lactic acid)-Based Covalent Adaptable Network.

A robust and fully biobased covalent adaptable network (CAN) that allows recyclability, biocompatibility, and controlled biodegradability is reported. The CAN was fabricated through a simple photo-cross-linking method, wherein low-molecular-weight poly(lactic acid) (∼3 kDa) was modified with end 1,2-dithiolane rings through a one-step Steglich esterification reaction with thioctic acid (TA). These incorporated 1,2-dithiolane rings undergo photoinduced ring-opening polymerization, thus enabling the cross-linking of poly(lactic acid) with abundant dynamic disulfide bonds. The resultant CAN demonstrates excellent transparency, effective UV-blocking capabilities below 320 nm, robust tensile strength (∼39 MPa), and superior dimensional stability at 80 °C, alongside attractive biocompatibility. Moreover, owing to the dynamic exchange and redox-responsiveness of disulfide bonds, the material can be recycled by hot-pressing and a reduction-oxidation process while also being capable of controllably biodegrading at the end of its lifecycle. Furthermore, it exhibits reconfigurable shape memory properties with fast recovery. This study elucidates a straightforward approach to fabricating multifunctional and sustainable polymer materials with potential applications in diverse fields such as packaging, coating, and biomedicine.

Nanoindentation creep: The impact of water and artificial saliva storage on milled and 3D-printed resin composites.

This study evaluated the effects of artificial saliva and distilled water on the nanoindentation creep of different 3D-printed and milled CAD-CAM resin composites. Disk-shaped specimens were subtractively fabricated from polymer-infiltrated ceramic network (EN) and reinforced resin composite (B) and additively from resin composite (C) and hybrid resin composite (VS) using digital light processing (DLP). Specimens from each material were divided into two groups according to their storage conditions (artificial saliva or distilled water for 3 months). Creep was analyzed by nanoindentation testing. Statistical analysis was done using two-way ANOVA, one-way ANOVA, Bonferroni post hoc tests, and independent t-test (α = 0.05). The main effects of material and storage conditions, and their interaction were statistically significant on nanoindentation (p<0.001). Storage condition had the greatest influence (partial eta squared ηP 2 =0.370), followed by the material (ηP 2 = 0.359), and the interaction (ηP 2 = 0.329). The nanoindentation creep depths after artificial saliva storage ranged from 0.34 to 0.51µm and from 0.50 to 0.87µm after distilled water storage. One of the additively manufactured groups had higher nanoindentation creep depths in both storage conditions. All specimens showed comparable performance after artificial saliva storage, but increased nanoindentation creep after distilled water storage for 3 months. The subtractive CAD-CAM blocks showed superior dimensional stability in terms of nanoindentation creep depths in both storage conditions. Additively manufactured composite resins had lower dimensional stability than one of the subtractively manufactured composites, which was demonstrated as having higher creep deformation and maximum recovery. However, after artificial saliva storage, one of the additively manufactured resins had dimensional stability similar to that of subtractively manufactured.

Alginate versus addition silicone: What is the best material for removable partial dentures?

Objective: The objective of this study was to create a narrative literature review article, covering two different types of materials: silicone and alginate, with the aim of seeing which is the best material to compose a removable partial denture. Methodology: The searches were carried out in PUBMED Central, Web of Science, VHL/BIREME, Brazilian CAPES, Scielo and using the Google Academy portal. A total of 24 articles were acquired that address the benefits and harms of using silicone and alginate in removable partial dentures, in addition to their differences. We consult periodicals and books, aiming to obtain more reliable information on the topic. In order to carry out a literature review, the vision of Mattos (2015) was used to structure the article. Results: During the study, it was seen that addition silicone is widely considered the best material due to its high precision, excellent ability to reproduce details and superior dimensional stability, however alginate is more economical and easier to use, it is more suitable for preliminary impressions and situations where extreme precision is not essential.

High-performance zero thermal expansion in Al metal matrix composites

Zero thermal expansion (ZTE) composites reinforced by negative thermal expansion (NTE) compounds exhibiting superior dimensional stability and high thermal conductivities, are urgently needed in the modern industrial field. Unfortunately, conventional strategies for achieving ZTE composites often compromise thermal conductivity by incorporating high-content NTE particles. This study reports an overlooked factor enhancing NTE: the in-situ thermal mismatch stresses within the composites, which provide a significant driving force for lattice distortion. The 50 vol.% Cu2P2O7/Al-Si composite achieves isotropic ZTE, low density, and high thermal conductivity due to pressure-enhanced NTE and a tight interface structure. Synchrotron X-ray diffraction and Density Functional Theory (DFT) calculations have revealed the key mechanism of in-situ residual thermal stress in the composite contributing to the enhancement of NTE in Cu2P2O7. This work proposes a novel design approach for high-performance ZTE materials.

Enhanced interfacial, mechanical, and anti-hygrothermal properties of carbon fiber/cyanate ester composites with the catalytic sizing agents of titanium epoxy

The mechanical properties of composites are closely related to the interfacial behavior, especially under the hygrothermal circumstance. A catalytic sizing agent of titanium epoxy is designed to enhance interfacial, mechanical, and anti-hygrothermal properties of high modulus carbon fiber (HMCF)/cyanate ester composites simultaneously. The mechanisms of interface enhancement and low hygroscopicity of composites are investigated. The titanium epoxy is synthesized and its catalytic effect on the curing of cyanate ester is proved. The interfacial properties of HMCF composites with catalytic sizing agents are improved to 95.5 MPa, which is attributed to the interphase with high crosslinking density and sufficient triazine rings and oxazolidinone structure due to preferential curing induced by interfacial catalysis, stimulating the smooth transition of interphase modulus. Further, the formed interphase exhibits few interface defects and low content of hydroxyl groups, which changes the moisture diffusion path and reduces saturated water absorption of composites to only 0.36 %, resulting in the release of interfacial wet stress concentration and high retention of mechanical properties in hygrothermal environment. The resultant composites with high stiffness, excellent temperature resistance, superior dimensional stability and low moisture absorption are expected to be applied to high-orbit space, aerospace, precision instruments.

The impact of base design and restoration type on the resin consumption, trueness, and dimensional stability of dental casts additively manufactured from liquid crystal display 3D printers.

To evaluate the effects of two base types and three restoration designs on the resin consumption and trueness of the 3D-printed dental casts. Additionally, the study explored the dimensional stability of these 3D-printed dental casts after 1 year of storage. Various types of reference dental casts were specifically designed to represent three types of dental restoration fabrications, including full-arch (FA), long-span (LS), and single-unit (SU) prostheses. The reference casts were digitized with a dental laboratory scanner and used to create flat and hollow base designs (N = 18) for the 3D-printed study casts. The 3D-printed study casts were digitized and evaluated against their corresponding references immediately after 3D printing and again after 1 year of storage, with the trueness quantified using the root mean square error (RMSE) at both time points. Volumes of resin used were recorded to measure resin consumption, and the weights of the 3D-printed study casts were also measured. The data were analyzed using two-way ANOVA and a Tukey post hoc test, α = 0.05. Volumetric analysis showed the flat-base design had significantly higher resin consumption with weights for the FA group at 42.51 ± 0.16g, the LS group at 31.64 ± 0.07g, and the SU group at 27.67 ± 0.31g, as opposed to 26.22 ± 1.01g, 22.86± 0.93g, and 20.10 ± 0.19g for the hollow designs respectively (p < 0.001). Trueness, assessed through two-way ANOVA, revealed that the flat-base design had lower RMSE values indicating better trueness in the LS (54 ± 6 µm) and SU (59 ± 7 µm) groups compared to the hollow-base design (LS: 73 ± 5, SU: 99 ± 11 µm, both p < 0.001), with no significant difference in the FA group (flat-base: 50 ± 3, hollow: 47 ± 5 µm, p= 0.398). After 1 year, the flat-base design demonstrated superior dimensional stability in the LS (flat base: 56 ± 6 µm, hollow base: 149 ±45 µm, p < 0.001) and SU groups (flat base: 95 ± 8 µm, hollow base: 183 ±27 µm, p < 0.001), with the FA group showing no significant difference in the base design (flat base: 47 ± 9, hollow base: 62 ± 12 µm, p = 0.428). The hollow-base design group showed lower resin consumption than the flat-base design group. However, the flat-base designs exhibited superior trueness and less distortion after 1 year of storage. These findings indicate that despite the higher material usage, flat-base designs provide better initial accuracy and maintain their dimensional stability over time for most groups.

Balancing dielectric properties and dimensional stability of poly(amide-imide) films via introducing a micro-crosslinked structure

With the rise of 5G communication technology and the development of microelectronics industry, establishing a balance between dielectric constant (Dk) and coefficient of thermal expansion (CTE) becomes significant for polyimide. Herein, a series of poly(amide-imide) (PAI) films were fabricated by using pyrophthalic dianhydride, 4,4′-diaminodiphenyl ether and 4,4′-diaminobenzanilide containing an amide structure as constitutional units; and then 1,3,5-tris(4-aminophenoxy)benzene (TAPOB) as the crosslinker was introduced to form the crosslinked structure within PAI films. The results indicated that well-designed crosslinked network could effectively balance the relationship between dimensional stability and the dielectric properties of PAI films. With the addition of just 0.1 mmol TAPOB, the Dk of corresponding PAI films decreased to 3.37 (at 105 Hz), compared with unmodified PAI films. Furthermore, the CTE of such PAI film revealed a 50.6 % reduction, revealing the superior dimensional stability. This work provides a novel strategy to design high-performance polyimide films for a practical application in flexible printed circuit board.

Poly(fluorenyl-indolinedione) based hydroxide conducting membrane for anion exchange membrane water electrolyzers

Anion exchange membranes (AEMs) serve as the heart of anion exchange membrane water electrolyzers (AEMWE) for green energy conversion electrochemical devices, directly determining the ultimate performance of the electrochemical devices. Conductivity in trade-off with stability (chemical and dimensional stability) is a major target in the development of alkaline membranes. We prepared chemically stable polyisatin-aromatics without ether linkages along the backbone by superacid-catalyzed alkylation. The alkali-stable dimethylpiperidinium cations were covalently linked to the polymer backbone through the aliphatic chain to give comb-type polyelectrolytes. Incorporating the fluorene structural units along the polymer skeleton is expected to improve conductivity and stability. The effect of polymer backbone structure and conformation on AEM properties is systematically elucidated. The results indicate the PipPFTI-25 AEM with 25 mol% dimethylfluorene fragments in the backbone has lower IEC (∼1.36 mmol g−1) but achieves high ionic conductivity (84.6 mS cm−1 at 80 °C). PipPFTI-25 exhibited superior dimensional and alkali stability, mainly reflected in the swelling ratio of less than 10 % while the OH− conductivity remained at 70 % after immersion in 2 M NaOH solution at 80 °C for 1680 h. The AEMWE with PipPFTI-25 operating at 60 °C in 1 M KOH achieves a current of 838 mA cm−2 at 2.5 V. This work demonstrated the feasibility of poly(fluorenyl-indolinedione) AEMs for electrolyzer applications.

Self-healing poly(oxime–carbamate) films with tunable mechanical properties derived from rosin

Thermoset polymers with superior dimensional stability and creep resistance have been widely used in various electronic and energy devices. However, they are difficult to reprocess and recycle, and with the gradual decrease in nonrenewable resources, there is an urgent need for new sustainable materials as alternatives to thermoset polymers. Polymer materials with self-healing properties can provide high durability and sustainability for devices. In this work, we prepared a series of rosin-based poly(oxime–carbamate) films by reacting rosin acrylate/glycidyl methacrylate ester with toluene 2, 4-diisocyanate using dimethylglyoxime as the chain extender and triethanolamine as the crosslinking agent. The introduction of rosin with a rigid tricyclic phenanthrene structure in the prepared films resulted in excellent tensile strength (4.9 ± 0.03 MPa) while maintaining high elongation at break (973.2 % ± 4.8 %) and toughness (20.9 ± 0.1 MJ m−3). The good self-healing properties of the prepared films (90.6 % ± 1.5 %, 60 °C for 3 h) were attributed to the introduction of dynamic oxime–carbamate bonds. In particular, the tunable mechanical and self-healing properties of the films can be achieved by varying the molar ratio of rosin acrylate/glycidyl methacrylate ester to dimethylglyoxime. Furthermore, the prepared rosin-based films exhibited good adhesion, welding, and anticorrosion properties. Considering the reversible exchange mechanism of dynamic oxime–carbamate bonds and their use in self-healing and recycling applications, a new strategy for developing sustainable high-performance biobased self-healing coatings is presented.

Using an aromatic amide as nucleating agent to enhance the crystallization and dimensional stability of poly(3-hydroxybutyrate-co-3-hydroxyhexanate)

Biosynthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has emerged as a promising biodegradable polymer with a great potential to compete with traditional petroleum-based plastics, however, the poor crystallization ability makes it challenge to transform into high-performance products via common melt-processing methods. Herein, we demonstrate that N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide (TMB) can serve as an efficient nucleating agent to significantly enhance the crystallization and resulting storage stability of PHBHHx. The results indicate that PHBHHx with small amounts of TMB (0.3–0.5 wt%) can crystallize completely even under a rapid cooling rate of 100 °C/min and the isothermal crystallization time is greatly reduced. As a result, the crystallinity of the injection-molded PHBHHx products is increased from 24.5 % to 39.5 %, without secondary crystallization after being stored at room temperature for 6 h. The products exhibit superior dimensional stability and the post-shrinkage can be decreased to as low as 0.1 %. Our work offers a feasible method to develop high-performance PHBHHx materials with remarkably enhanced crystallization ability.

Influence of A-Site Deficiency and B-Site Composition on the Electrical and Crystallographic Properties of (La0.25Sr0.25Ca0.45)yTi0.95Ni0.05-xMnxO3-δ Solid Oxide Fuel Cell Anode

(La,Sr)TiO3-δ has attracted specific attention over the past years due to its superior dimensional stability, high conductivity, and significant tolerance against sulfur poisoning and carbon depositions. To increase the catalytic activity and chemical stability, many different doping levels and stoichiometries for LaxSr1-xTiO3-δ (LST) have been investigated [1, 2]. Doping of B-site with Mn has been shown to promote electroreduction under SOFC conditions [3]. Furthermore, Mn is known to accept lower coordination numbers in perovskites, especially for Mn3+ (3d4), and so may enhance oxide-ion migration [4]. In addition, MnO is clearly stable under fuel conditions unlike Co or Ni oxides [4].In this research influence of A-site deficiency and B-site chemical composition on electrical performance of La0.25Sr0.25Ca0.45Ti0.95Ni0.05-xMnxO3-δ (x=0-0.05) (LSCTNM-x) hydrogen electrode has been studied. The crystal structure and microstructure have been studied using X-ray diffraction and SEM to confirm the phase purity and visualize the microstructure of studied electrode layers. To understand the influence of MIEC material composition on electrical conductivities of LSCTNM, the DC four-probe conductivity measurements of porous electrode layers has been performed. Conductivities have been measured at two different atmospheres: 1% H2 + 1.7% H2O + 97.3% Ar and 98.3% H2 + 1.7% H2O. It has been shown that all materials with LSCTNM compositions behave like semiconductor and the conductivity is significantly dependent on composition. The maximal total electrical conductivity of porous electrode layers was characteristic for the LSCTNM materials with 10% A-site deficiency, in 98.3% H2 + 1.7% H2O atmosphere. Keywords: solid oxide fuel cell; conductivity; perovskite; fuel electrode; MIEC.[1] X. Li, H. Zhao, X. Zhou, N. Xu, Z. Xie, N. Chen, Electrical conductivity and structural stability of La-doped SrTiO3 with A-site deficiency as anode materials for solid oxide fuel cells, international journal of hydrogen energy 35 (2010) 7913-7918.[2] A. Gondolini, E. Mercadelli, G. Constantin, L. Dessemond, V. Yurkiv, R. Costa, A. Sanson, On the manufacturing of low temperature activated Sr0.9La0.1TiO3-δ-Ce1-xGdxO2-δ anodes for solid oxide fuel cell, Journal of the European Ceramic Society, 38 (2018) 153–161.[3] P. Holtappels, J. Bradley, J.T.S. Irvine, A. Kaiser, M. Mogensen, Electrochemical characterization of ceramic SOFC anodes, J. Electrochem. Soc. A 148 (2001) 923–929.[4] S. Tao, J.T.S. Irvine, A redox-stable efficient anode for solid-oxide fuel cells, nature materials, 2 (2003) 320-323.

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks

BackgroundTo study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale.MethodsSeven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials.ResultsThe nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 μm and increased after 3 months storage in distilled water to between 0.28 and 3.46 μm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found.ConclusionThe PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Die-embedded packaging using Corning® multi-layered glass

Die-embedded (DE) packaging technologies in recent years have ventured into advanced packaging structures, such as fan-out wafer level packages (FOWLPs) or package-on-packages (PoPs). They offer higher density at lower costs, despite many challenges, such as the die-shift and warpage problems often observed during the molding process, caused by the high shrinkage and high coefficients of thermal expansion (CTEs) of the molding materials. This in turn makes it difficult to accurately mount the high-density fine-pitch bumps and adversely affects the overall yield, especially in processes using large-size substrates. Glass, known for its superior dimensional and thermal stability and its low or tunable CTEs, can be advantageous in reducing die-shift and warpages as opposed to other alternative material solutions for the molding process. In this paper, we propose a packaging solution based on a glass substrate incorporating a plurality of precisely dimensioned cavities, with a chip positioned in each cavity to prevent them from shifting during processing. Corning® Adaptive Formed Glass (AFG), a laminate glass with a unique clad/core/clad structure, allows for effectively forming cavities with high dimensional precision and positional accuracies as well as surface flatness through a wet etch process. Using a 0.5mm thick laminate Corning® AFG glass, we successfully designed and fabricated three types of DE packages with lab scale tools at Korea Electronics Technology Institute (KETI): single- and double-sided DE packages, and package-on-packages (POPs). High etching selectivity over 20:1, which was achieved by carefully designing the core and clad glass compositions, enabled a wet-etch cavity forming process with accurate cavity depths and flat bottom surfaces (&lt; ± 2.5μm) with relative ease. A double-sided DE package with a total thickness of 600μm was fabricated with two 125μm-thick IC chips, one embedded on each side of the substrate, and connected by metallized through glass vias (TGVs). A POP measured at 5.1×5.1×1.27 mm3 was also successfully demonstrated by using two built-in double-sided DE packages joined by flip-chip bonding, equivalent to stacking four layers of conventional single-sided DE packages. The double-sided DE packages and POPs presented in this paper are believed to be the world’s first demonstration on glass. The work also manifests the immense potential of Corning® AFG glass in enabling higher density IC packaging and large-size panel-level (or wafer-level) packaging.

Novel shear thickening gel/high‐performance fiber reinforced flexible composites: Multi‐velocity impact and functional properties

AbstractShear thickening gel (STG) is a promising substrate used for flexible protective materials, which has superior dimensional stability without gel side leakage and delamination when sustaining long‐standing time. STG/high‐performance fiber flexible composites exhibit high‐energy absorption capacity for multi‐velocity impact. This article reveals the shear thickening mechanism of STG that lays a theoretical foundation for the performance analysis of STG composites. The preparation methods of STG/high‐performance fiber flexible composites, including impregnation, hand lay‐up, filling, and lamination methods, are compared. The energy absorption principle of STG/high‐performance fiber flexible composites on multi‐velocity impact and the destruction morphology was analyzed. The coupling effects and functional applications of STG functional composites with nanoparticles, magnetic particles, and conductive particles are summarized. It provides more suitable conditions for designing new multifunctional protective equipment and manufacturing advanced intelligent, protective devices.

Material Extrusion Additive Manufacturing with Polyethylene Vitrimers.

Polyethylene (PE) is one of the most widely used polymers in conventional polymer manufacturing processes. However, it remains a challenge to use PE in extrusion-based additive manufacturing (AM). Some of the challenges that this material presents include low self-adhesion and shrinkage during the printing process. These two issues lead to higher mechanical anisotropy when compared to other materials, along with poor dimensional accuracy and warpage. Vitrimers are a new class of polymers that have a dynamic crosslinked network, allowing the material to be healed and reprocessed. Prior studies on polyolefin vitrimers suggest that the crosslinks reduce the degree of crystallinity and increase the dimensional stability at elevated temperatures. In this study, high-density polyethylene (HDPE) and HDPE vitrimers (HDPE-V) were successfully processed using a screw-assisted 3D printer. It was demonstrated that HDPE-V were able to reduce shrinkage during the printing process. This shows that 3D printing with HDPE-V will provide better dimensional stability when compared to regular HDPE. Furthermore, after an annealing process, 3D-printed HDPE-V samples showed a decrease in mechanical anisotropy. This annealing process was only possible in HDPE-V due to their superior dimensional stability at elevated temperatures, with minimal deformation above melting temperature.

The role of H-phase in thermal hysteresis and shape memory properties in Ni50Ti30Hf20alloy

Ni50Ti30Hf20 high temperature shape memory alloy was aged at 550 °C for 10 h and 450 °C for 50 h which corresponds to the peak hardening state with equal gain in strength caused by different size/volume fraction ratio of nano-precipitation of H-phase. In order to determine the effect of such structures on the martensitic transformation, thermal cycling and shape-memory properties were measured. It is shown that finer precipitates with higher volume fraction provide superior dimensional stability, good thermal cycling stability and small transformation hysteresis.

Safety and performance enhanced boehmite-coupled polyethylene nanocomposite separator for lithium-ion batteries by synergetic effects of silane treatment and electron irradiation

Separators are among the key components affecting both the safety and performance of batteries. Herein, boehmite-coupled high-density polyethylene (HDPE) nanocomposite separators with enhanced safety and performance are prepared via silane treatments and electron irradiation. The silane treatment of boehmite nanoparticles (BNPs) leads to the homogeneous dispersion of the BNPs in HDPE owing to the spacer alkyl groups in silane. Electron irradiation induces chemical coupling between the silane-treated BNPs and HDPE, as well as the crosslinking of HDPE. Electron irradiation also oxidizes HDPE, improving the electrolyte affinity of the separators. Consequently, the safety and performance of the separators are significantly improved, and the degree of improvement depends on the type of silane. A nanocomposite separator comprising octadecyl-functionalized BNPs exhibits superior dimensional stability (puncture strength of 0.74 N μm−1 and thermal shrinkage of 3.2% at 140 °C for 30 min). In addition, a nanocomposite separator comprising aminopropyl-functionalized BNPs demonstrates excellent ionic conductivity (1.61 mS cm−1). A lithium-ion cell assembled with the nanocomposite separator has an exceptional rate capability (discharge capacity at 20 C maintains 72.9% of the capacity at 0.5 C) and cyclic stability (discharge capacity retention of 96.2% with a Coulombic efficiency of 99.5% after 100 charge/discharge cycles at 0.5 C).

Comparison of Linear Dimensional Stability among Three Different Types of Interocclusal Recording Materials: An In-vitro Study

Introduction: In routine dental practice, clinicians often face difficulty in selecting accurate interocclusal recording materials due to the introduction of numerous options in the market. Therefore, it is crucial to choose the appropriate material and use it correctly for the success of any prosthesis. Aim: To evaluate and compare the linear dimensional stability of three different types of interocclusal recording materials: polyvinyl siloxane bite registration paste (orangebite), polyether bite registration paste (ramitec), and bite registration wax (aluminium filled). Materials and Methods: An in-vitro study was conducted in the Department of Prosthodontics and Crown and Bridge, with microscopic evaluation performed at the Department of Oral and Maxillofacial Pathology and Microbiology at Maratha Mandal’s NGH Institute of Dental Sciences and Research Centre, Belagavi, Karnataka, India in September 2020 for a period of four days. A stainless steel die was used to make impressions, and materials were manipulated according to the manufacturer’s instructions. A total of 30 samples (10 for each material) were created. Three minutes after the respective setting time of each material, discs were separated from the die. The distance between two parallel lines was measured using a stereomicroscope at different time intervals: one hour, 24 hours, 48 hours, and 72 hours. Statistical analysis was performed using Analysis of Variance (ANOVA) and the Mann-Whitney test. Results: In the intragroup comparison of dimensional changes at different time intervals, all three materials showed statistically insignificant results (p&gt;0.05). However, statistically significant results (p≤0.05) were found when comparing the materials at different time points. Polyether bite registration material exhibited better dimensional stability than polyvinyl siloxane and bite registration wax at one hour, 24 hours, 48 hours, and 72 hours. Conclusion: Polyether demonstrated superior dimensional stability compared to polyvinyl siloxane and bite registration wax. The dimensional stability was influenced by both the material used and the duration of time