Amorphous Resin Research Articles

Paleoenvironmental changes recorded in the Santa Marta Formation (Santonian–Campanian, Upper Cretaceous), James Ross Island, Antarctica, inferred from palynofacies analyses

The Santa Marta Formation (Santonian–Campanian; James Ross Island, Antarctic Peninsula) is part of one of the most complete sedimentary sequences in the Southern Hemisphere. Paleoenvironmental changes recorded in the formation are reflected in the stratigraphic distribution of sedimentary organic matter in the Lachman Crags and Herbert Sound members. Fifty-three samples from the Lachman Crags section and ten samples from the Herbert Sound section were prepared using standard non-oxidative methods for palynofacies. Analyses were performed using transmitted white light and fluorescence microscopy to identify the groups and subgroups of sedimentary organic matter: non-opaque non-biostructured and biostructured opaque particles, membrane fragments, degraded and non-degraded cuticles, spores, pollen grains, fungal spores, Botryococcus, Palambages, dinoflagellates cysts, amorphous organic matter, pseudoamorphous (product of disintegration of macrophyte tissues) and resins. Three palynofacies associations are distinguished: terrestrial, opaque, and marine palynomorphs. Based on stratigraphically restricted cluster analysis (CONISS), three intervals have been identified: Interval 1, at the base of the Lachman Crags section, conspicuously dominated by the terrestrial palynofacies association. Interval 2, the middle portion of the Lachman Crags section, is marked by alternating terrestrial and opaque palynofacies associations. Interval 3, which coincides with the Herbert Sound section, is distinguished by an abrupt increase in marine elements. The composite section shows progressive transgression, accompanied by a decrease in continental elements, culminating in an open marine environment towards the top of the section.

Improving inherent thermal conductivity of epoxy resins based on contribution components of thermal conductivity: A molecular dynamics study

The inherent thermal transport properties of epoxy resin are vital factors to be studied in applications. In the present work, we constructed the amorphous crosslinking structure, the step crosslinking structure and the ordered crosslinking structure based on molecular dynamics theory, and used the reverse nonequilibrium molecular dynamics (RNEMD) method to calculate the thermal conductivity (TC) of different structures. Based on the numerical verification of the reliability of the method, the contribution of bonding to the TC was enhanced by increasing the molecular arrangement orderliness to reduce phonon scattering, taking the composition of the TC contribution as the guide. Meanwhile, the contribution of non-bonding interaction to the TC was enhanced by using compression process to achieve TC increase in the epoxy resin intrinsic structure, followed by exploring the effect of cross-linking degree on the TC of different structures. The results showed that the TC of amorphous epoxy resin decreased with the increase of crosslinking degree, and the relative high-frequency VDOS increased, but the influence of crosslinking degree on TC was minor in the range. For amorphous epoxy resin four-sided pressurization varied in the range of 0–7 Gpa, the non-bond energy percentage increased in the range of 0–60%, and the increase of non-bond energy made its contribution to TC increased significantly. The epoxy resin achieved 215% improvement in intrinsic TC by changing the molecular arrangement orderliness. The ordered structure TC varied from 0.3 to 3.5 W/(m⋅K) in the pressure variation range of 0–7 GPa. As the structure becomes more ordered, the TC increased significantly with the degree of cross-linking. The study provided the theoretical basis for the realization of resin preparation and resin thermal property evaluation with regulated intrinsic TC.

Review of thermal conductivity in epoxy thermosets and composites: Mechanisms, parameters, and filler influences

Rapid development of energy, electrical and electronic technologies has put forward higher requirements for the thermal conductivities of epoxy resins and their composites. However, the thermal conductivity of conventional epoxy resins is relatively low, which could cause major heat dissipation issues. Therefore, the thermal conductivity enhancement of epoxy resins has long been a hot research topic in both academia and industry. In recent years, many promising advances have been made at the technical and mechanistic levels. This review includes the different approaches, the thermal conduction mechanisms implied, and the main research progresses. The research and academic achievements are mainly focused on the development of intrinsically liquid crystal epoxy resins and their composites, and the addition of fillers on amorphous epoxy resins. Finally, the challenges and prospects for thermal conductive epoxy resins are provided. Notably, this review can provide a more comprehensive understanding of thermally conductive epoxy resins and a guideline for the cutting-edge development direction of thermally conductive epoxy resins.

Validation of a 1D dynamic thermal finite difference model for the rotational molding of an amorphous polycarbonate resin

AbstractThis study focuses on the heating stage of the rotational molding process. When the mold wall reaches the tacky temperature, free flowing powder starts to adhere, melt, and sinter. In this work, a new modeling strategy is proposed. Compared with the models found in the literature, the model combines the use of a tacky temperature for the adherence of powder, changing boundary conditions, and thermophysical properties as function of temperature and the degree of sintering. The changing boundary conditions are introduced to take into account both wall to air and wall to powder contact. The calculation of the temperature evolution is done by applying the thermal finite difference principle to elements with a fixed polymer mass. The modeling of a uniaxial rotating cylinder is chosen as a case study. The validation is done for an amorphous polycarbonate resin. The performance of the model is evaluated not only by the comparison of temperature‐time data as is the case in most literature, but also by the decrease in free flowing powder weight as function of time, visual data from an in‐mold looking camera, and through thickness analysis of the molded pieces at various moments in the heating process.

Influence of Thin Fluorine Resin Film on DUV LED Packaging Devices

Amorphous fluorine resin is a promising material that can be used for the encapsulation of deep-ultraviolet light-emitting diodes (DUV LEDs) to promote the light output, due to its light characteristics which mean it shows no absorption in the DUV wavelength region. However, obvious decay and high cost are the problems faced by fluorine resin. In this study, thin-fluorine-resin-film-packaged DUV LEDs were fabricated by the drip-coating method and the characteristics were tested. The results show that the light output power increased from 4.95 mW to 5.44 mW at 40 mA, and the cost of fluorine resin can be reduced to ~10%. In addition, no degradation during the aging was observed. However, when the light output power reached 12 mW or higher, >10% decay was observed after aging for 1000 h. In conclusion, thin-fluorine-resin-film-packaged DUV LEDs can achieve 10% light output power enhancement by using less fluorine resin material, and the material is more applicable to low-power DUV LEDs.

The first discovery of amber resin in Lichi Mélange, Eastern Taiwan

Amber is fossilized tree resin produced by the metabolism of vascular plants that has experienced various geological processes, including burial, compression, and heating. Therefore, most of the previously reported amber pieces were unearthed from sedimentary rocks. The record of amber in tectonic active regions, e.g., Taiwan, is extremely poor and has not been scientifically certified, leading to a poor understanding of the history of prehistoric flora in this region. This study reports a 1-cm yellow-brown amorphous resin interspersed in sandstone blocks in the Lichi Mélange at the southernmost tip of the Coastal Range in eastern Taiwan, representing the first official record of amber from the mélange unit and as well as in Taiwan. The results, in addition to the affirmation of the amber, show that the amber is composed of sesquiterpenes and triterpenoids, indicating a possible origin of dipterocarp trees that are absent in the paleobotanic record and modern flora in Taiwan. Furthermore, infrared spectra analysis shows its compositional similarity to the amber from Sumatra, Indonesia, which boasts modern dipterocarp forests. Petrographic analysis of the surrounding sandstone suggests that the amber was deposited into the continental margin and allocated to Taiwan through the arc-continental collision in ∼6–7 Ma. In summary, this study represents the first report of amber unearthed in the mélange unit and Taiwan. It shows that amber is a durable and reliable information carrier in accordance with biogeographic and tectonic evidence.

Fundamental understanding of the thermal properties of amorphous epoxy resin coatings filled with quartz-feldspar powder sourced from quarry waste

In the present work, a novel coating modified with quartz-feldspar powder (QFP) was prepared in order to overcome the well-known technical problems related to the thermal behavior of epoxy resin (ER) coatings. The degradation of floor coatings is often caused by thermal shock and depends on the difference in the thermal expansion between the ER coating and the substrate. The thermal expansion is strongly related to the thermal gradient. Therefore, the specimens were tested using differential scanning calorimetry in order to analyze the regions of the viscoelastic behaviors, the glass transition temperature, the specific heat capacity, the slopes of heat capacity, and the energy required to change the temperature of the material. The application of QFP reduced the value and slope of the specific heat capacity of the composite. The modification of the coating inhibits the growth of temperature, which in turn can reduce the risk of delamination caused by thermal shock. It also improves the adhesion of the coating the concrete substrate. The novelty of the article involves a detailed description of the influence of QFP waste on the thermal behavior of ER, as well as its effect on the thermal shock degradation of industrial floor coatings.

Electron irradiation damage of amorphous epoxy resin at low electron doses.

The mechanisms of electron irradiation damage to epoxy resin samples were evaluated using their electron diffraction patterns and electron energy-loss spectra. Their electron diffraction patterns consisted of three indistinct halo rings. The halo ring corresponding to an intermolecular distance of ∼6.4 Å degraded rapidly. Such molecular-scale collapse could have been caused by cross-linking between molecular chains. The degree of electron irradiation damage to the samples changed with the accelerating voltage. The tolerance dose limit of the epoxy resin estimated from the intensity of the halo ring was found to be improved at a higher accelerating voltage. Changes in low-loss electron energy-loss spectra indicated that the mass loss of the epoxy resin was remarkable in the early stage of electron irradiation.

Preparation of All Amorphous PMMA Resins Based on the Graft Architecture with a Flexible Main Chain for Simultaneous Enhancement of Thermal and Mechanical Toughness

AbstractThis study shows the design of poly(methyl methacrylate) (PMMA)‐based glassy polymers with simultaneous improvement of thermal resistance and mechanical toughness, based on the graft architecture with a low glass transition (Tg) flexible main chain. The microphase‐separated structure of the flexible main chain and the glassy graft chains in this design may be key to these improved properties. Notably, the graft copolymer depicts the ductile fracture, and the microscopy observation for the fractured sample exhibits the presence of abundant void formation with relatively homogenous size and interval throughout the sample. The void formation could originate from the preferential fracture of aggregated flexible components distributed throughout the sample, indicating the effective role of the flexible main chain on the suppression of the internal stress. The novelty of the present study is on the use of simple graft architecture for enhancing the toughness of glassy resins. This idea is indeed distinct from the conventional approach to improve toughness by adding plasticizer or rubber particles, therefore opening a new method for the creation of high‐functional glassy polymers.

Elucidating atomistic mechanisms underlying water diffusion in amorphous polymers: An autonomous basin climbing-based simulation method

Conventional molecular simulations of diffusive molecules in amorphous polymers lead to discrepancies in understanding diffusion mechanisms at low temperatures due to the short timescales of the simulations. This work proposes a combined scheme of the autonomous basin climbing (ABC) method accompanied with kinetic Monte Carlo and reactive molecular dynamics (MD) simulations to investigate water molecules’ diffusion pathways in amorphous epoxy resins across a wide range of temperatures. The ABC method, along with a reactive force field, provides an accurate potential energy surface sampling approach to elucidate diffusion mechanisms affected by hydrogen bonding interactions between water molecules and an epoxy network. The simulation framework allows the capture of thermal effects on the diffusion coefficients and offers a predictive simulation tool for predicting diffusion coefficients of water molecules in amorphous polymers. The simulation results show that the activation energy of the diffusion coefficient is in agreement with experimental data. The proposed simulation framework not only estimates kinetic properties of water diffusion in epoxy resins that are consistent with experimental observations, but also provides a predictive tool for studying the diffusion of small molecules in other amorphous polymers.

Casein phosphopeptide amorphous calcium phosphate and universal adhesive resin as a complementary approach for management of white spot lesions: an in-vitro study

BackgroundWhite spot lesion (WSL) is the most common consequence during and after orthodontic treatment. This study was conducted to investigate the ability of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) coupled with universal adhesive resin to treat white spot lesions.Material and methodsForty-five extracted premolars were sectioned to create 90 specimens. Seventy-five specimens were demineralized to generate artificially created WSLs. Different strategies have been applied for the management of the artificially created WSLs. Six experimental groups were employed: Group I: sound enamel (control), Group II: demineralized enamel (artificially-created WSLs), Group III: ICON resin-treated WSLs, Group IV: CPP-ACP-treated WSLs, Group V: universal adhesive resin-treated WSLs, and Group VI: CPP-ACP followed by universal adhesive resin-treated WSLs. Assessment of color stability using a spectrophotometer, surface microhardness using a Vickers tester, and surface roughness using a profilometer was done. The surface topography of representative specimens from each experimental group was inspected using a scanning electron microscope. Collected data were analyzed using one-way ANOVA followed by Tukey’s post hoc test at p ≤ 0.05.ResultsWhite spot lesions treated with CPP-ACP and subsequently coated with universal adhesive resin (Group VI) exhibited a significantly lower ΔE than both CPP-ACP (Group IV) and universal adhesive resin-treated (Group V) groups (p ≤ 0.05), but it was not significantly different from the ICON resin-treated group (Group III). For surface microhardness, WSLs treated with CPP-ACP and consequently coated with universal adhesive resin (Group VI) recorded the highest mean that was significantly different from both ICON resin (Group III) and universal adhesive resin-treated (Group V) groups (p ≤ 0.05). All the tested strategies (ICON resin, CPP-ACP, universal adhesive resin, and CPP-ACP followed by universal adhesive resin) significantly lowered the surface roughness of the WSLs (p ≤ 0.05), while no significant difference was detected among them.ConclusionsCombining a considerable caries remineralizing program using CPP-ACP with subsequent universal adhesive resin infiltration could be a promising approach to manage WSLs efficiently through increasing surface microhardness and restoring esthetic while developing a smoother surface.

Fundamental Understanding of the Thermal Properties of Amorphous Epoxy Resin Coatings Filled with Quartz-Feldspar Powder Sourced from Quarry Waste

Fundamental Understanding of the Thermal Properties of Amorphous Epoxy Resin Coatings Filled with Quartz-Feldspar Powder Sourced from Quarry Waste

Stress Evaluation and Structural Analysis of Epoxy Resin by X-ray Measurement

X-ray diffraction measurements were performed on epoxy resin, an amorphous resin material, under tensile loading conditions using synchrotron radiation, and possibility of stress evaluation was examined based on the shift in the diffraction profile. The difference between static loading and fatigue of epoxy resin was investigated from the viewpoint of microstructure using PDF (Pair Distribution Function) analysis, which is the structural analysis in terms of interatomic distance.

Study on the Soft Magnetic Properties of FeSiB/EP Composites by Direct Ink Writing

Fe-based amorphous alloy has excellent soft magnetic properties; traditionally, Fe-based amorphous alloy such as soft magnetic devices was fabricated by insulation enveloping and suppression molding methods. In this process, the aging of organic envelope materials and the crystallization of Fe-based amorphous alloy were usually occurring, accompanying with low magnetic induction and poor mechanical properties. The direct ink writing (DIW) technique can make complex-shaped parts and needs no heating treatment after forming, which can avoid the effect of traditional molding process. In the present study, varying mass fraction FeSiB/EP composite parts were prepared by the DIW technique with the Fe-based amorphous alloy powder and epoxy resin, in which microscopic morphology, magnetic properties, and mechanical properties of FeSiB/EP soft magnetic composites were studied. The results indicate that the slurry with iron powder mass fraction of 92.3, 92.6, and 92.8 wt% has good printing performance and self-support ability, which is suitable for DIW. The density of the printed parts is about 4.317, 4.449, and 4.537 g/cm3, which is almost similar with the iron powder. The tensile strength and elongation of printing parts are significantly improved compared with the pure epoxy resin. From the photos of microscopic morphology of printing parts, it can be seen that FeSiB powders are evenly dispersed in EP, no pores, and defects, with the proportion increasing of powders; the insulation coating thickness decreases; and the magnetic performance improves. The optimal sample is 92.8 wt% FeSiB/EP, in which saturation magnetic induction strength is 137.9759 emu/g and coercivity is 4.6523 A/m.

Large volume tomography using plasma FIB-SEM: A comprehensive case study on black silicon

The xenon plasma focused ion beam and scanning electron microscopy (PFIB-SEM) system is a promising tool for 3D tomography of nano-scale materials, including nanotextured black silicon (BSi), whose topography is difficult to measure with conventional microscopy techniques. Advantages of PFIB-SEM include high material removal rates, precise control of milling parameters and automated slice-and-view procedures. However, there is no universal sample preparation procedure nor is there an established ideal workflow for the PFIB-SEM slice-and-view process. This work demonstrates that specimen preparation, including the orientation of the volume of interest, is critical for the quality of the final reconstructed 3D model. It thoroughly explores three unique configurations incrementally optimized for higher total throughput. All three sampling configurations are applied to a resin-embedded BSi sample to determine the most favourable workflow and highlight each approach's advantages and disadvantages. The reconstructed 3D models of the BSi surface obtained are shown to be qualitatively closer to the topography measured directly by SEM. The height distribution data extracted from the rendered 3D models reveal a higher structure depth compared to that obtained from an atomic force microscopy measurement. Furthermore, the work demonstrates how samples with different rigidity react to long-term ion-beam interaction, as both amorphous (resin) and crystalline (Si) material is present in the tested specimen. This study improves the understanding of sample-beam interaction and broadens the utility of the 3D PFIB-SEM for more complicated sample structures.

Dithienothiazine Copolymers – Synthesis and Electronic Properties of Novel Redox-Active Fluorescent Polymers

Dithienothiazine copolymers are efficiently obtained by Suzuki polymerization or in situ lithiation–Negishi polymerization in good to excellent yields. Gel permeation chromatography was applied to characterize the dispersities and degrees of polymerization of these novel materials. Thermogravimetric analysis shows that the copolymers are stable towards side-chain cleavage up to 200 °C. The materials are deep red to black amorphous solids or resins and their absorption and emission spectra in solution reveal broad absorption bands in the visible and orange to deep red luminescence upon UV excitation. According to the optical band gaps these novel copolymers qualify as a new class of low band gap organic semiconductors.

Crystalline Lamellar Structure of Thermosetting Urea–Formaldehyde Resins at a Low Molar Ratio

Reducing formaldehyde emission from cured urea–formaldehyde (UF) resins forced us to synthesize UF resins at a low formaldehyde to urea (F/U) molar ratio (≤1.0), resulting in low emission and poor adhesion by forming crystalline domains instead of building a three-dimensional network in cured resins. For the first time, we report a crystalline lamellar structure of thermosetting UF resins at a low molar ratio and compare it with highly amorphous UF resins at a high F/U molar ratio (1.6). Films of crystalline and amorphous UF resins were prepared using a spin-coater and characterized using atomic force microscopy. In addition, transmission electron microscopy, gel permeation chromatography, and X-ray diffraction were also employed for their characterization. The results showed that 1.0 UF resins had a low molecular weight with a lamellar structure of the crystalline domain, whereas 1.6 UF resins exhibited a high molecular weight with an amorphous structure and had a lower surface roughness. Fourier transform infrared and carbon-13 nuclear magnetic resonance spectroscopy also proved that linear molecules and hydrogen bonding were responsible for the formation of crystalline lamellar structures in thermosetting UF resins at a low molar ratio.

Enhancing adhesion of thermosetting urea-formaldehyde resins by preventing the formation of H-bonds with multi-reactive melamine

ABSTRACT Contemporary urea-formaldehyde (UF) resins with low-molar-ratio contain highly crystalline domains induced by the hydrogen (H) bonds between their linear molecules, which inhibits cross-linking, and results in poor adhesion. In this study, a novel way of controlling the crystallinity of such resins by preventing the formation of H-bonds using multi-reactive melamine during synthesis was reported. FTIR and 1H-NMR spectroscopy confirmed the shifting of the carbonyl (C = O) peak, and N-H signal. XRD patterns revealed the conversion of crystalline to amorphous domains by adding 20% melamine, resulting in a decrease in crystallinity from 52 to 22%. The amorphous UF resins cured faster, have higher molecular weight and cross-linking density, and also followed the autocatalytic reaction model with excellent theoretical fitting. In addition, a 33% increase in adhesion strength, and a 62% reduction in formaldehyde emission was recorded. Hence, the addition of 20% melamine into the UF resins leads to better adhesion and less formaldehyde emission.

Effects of nanoclay modification with transition metal ion on the performance of urea–formaldehyde resin adhesives

As a way of reducing the formaldehyde emission and improving the adhesion of urea–formaldehyde (UF) resins, this study investigated the addition effects of pristine nanoclay (PNC) or modified nanoclay (MNC) with transition metal ion (TMI) on the performance of UF resin adhesives. Instead of a conventional simple mixing (SM) of MNC with UF resin (coded as MNC-SM), this study explored adding PNC or MNC into either the alkaline (ALK) or acidic (ACD) reaction during the synthesis of UF resins, which were coded as PNC-ALK, PNC-ACD, MNC-ALK, and MNC-ACD, respectively. For the first time, we report that the MNC-ALK resins result in almost amorphous UF resins with 25% crystallinity, which consequently increases the cross-linking, and improve the adhesion strength and decrease formaldehyde emission of modified UF resins. It is believed that the intercalated or exfoliated MNCs facilitate the formation of more cross-linking in the modified UF resins, leading to a better cohesive strength.

Pharmacological effects of the isomeric mixture of alpha and beta amyrin from Protium heptaphyllum: a literature review

Protium heptaphyllum Aubl. belongs to the Burseraceae family. It is commonly called 'almecegueira' and is known to produce an amorphous resin which has constituents such as α- and β-amyrin, taraxastan-3-oxo-20-ol and sitostenonein. The α- and β-amyrin from P.heptaphyllum have pharmacological activities in several systems, such as central and peripheral nervous system, gastrointestinal tract and immunological system. In this study, our objective was to review pharmacological activities and to gather more information on the mixture of α- and β-amyrin obtained from P.heptaphyllum to guide future preclinical and clinical studies using this compound. This review consisted of searches performed using scientific databases such as PubMed, SciELO, LILACS, SciFinder and Science Direct. Some uses of α- and β-amyrin have been partially confirmed by previous studies demonstrating analgesic, anti-inflammatory, anticonvulsant, antidepressive, gastroprotective, hepatoprotective, antipancreatitic, anticholytic, antihyperglycemic and hypolipidemic effects. It is noteworthy that there are no α- and β-amirin toxicity tests described in the literature as recommended in the international guidelines, and such tests are one of the research stages to proceed in clinical and preclinical trials if this compound was to be used.