Level Of Cross-linking Research Articles

Highly Deformable Phototunable Viscoelastic Fluid Interface Modulates Cellular Adaptive Wetting Behavior

AbstractEmerging evidence shows that the viscoelastic cues of the e Ixtracellular matrix (ECM) regulate cellular functions and fates. However, as cells are viscoelastic, force dissipation occurs within themselves as well as the ECM side, implying the existence of reciprocal viscous regulation between the two. Here, a fluid‐based scaffold with tunable viscoelasticity has been developed to investigate its impact on the cell adhesion process. The platform is based on the water–perfluorocarbon interface decorated with diacetylene‐based phospholipid membranes (IPLMs), whose viscoelasticity can be systematically manipulated by photocrosslinking. Further introduction of a cell‐adhesive peptide and fluorescent tag allows cell adhesion at the highly deformable fluid interface and confocal observation of dynamic cell–model ECM interactions. The viscoelasticity‐tunability is confirmed by fluorescence recovery after photobleaching, interfacial rheology, and atomic force microscopy nanoindentation. Cells seeded at the IPLM exhibit so‐called adaptive wetting, where the interface first deforms toward the out‐of‐plane direction before cellular dimensional changes, followed by cellular flattening and interfacial restoration. Furthermore, the quantification of these parameters reveals a biphasic response against the crosslinking levels, which indicates that the cell‐ECM viscosity balance determines adaptive wetting phenotypes. The platform may enable the prediction of dynamic adhesion responses in physiological and pathological processes.

Large-Scale Quantitative Cross-Linking and Mass Spectrometry Provides New Insight on Protein Conformational Plasticity within Organelles, Cells, and Tissues.

Many proteins can exist in multiple conformational states in vivo to achieve distinct functional roles. These states include alternative conformations, variable PTMs, and association with interacting protein, nucleotide, and ligand partners. Quantitative chemical cross-linking of live cells, organelles, or tissues together with mass spectrometry provides the relative abundance of cross-link levels formed in two or more compared samples, which depends both on the relative levels of existent protein conformational states in the compared samples as well as the relative likelihood of the cross-link originating from each. Because cross-link conformational state preferences can vary widely, one expects intra-protein cross-link levels from proteins with high conformational plasticity to display divergent quantitation among samples with differing conformational ensembles. Here we use the large volume of quantitative cross-linking data available on the public XLinkDB database to cluster intra-protein cross-links according to their quantitation in many diverse compared samples to provide the first widescale glimpse of cross-links grouped according to the protein conformational state(s) from which they predominantly originate. We further demonstrate how cluster cross-links can be aligned with any protein structure to assess the likelihood that they were derived from it.

The Potential Role of Cigarette Smoke, Elastic Fibers, and Secondary Lung Injury in the Transition of Pulmonary Emphysema to Combined Pulmonary Fibrosis and Emphysema.

Combined pulmonary fibrosis and emphysema (CPFE) is a distinct syndrome associated with heavy smoking. The fibrotic component of the disease is generally believed to be superimposed on previously existing pulmonary emphysema, but the mechanisms responsible for these changes remain poorly understood. To better understand the pathogenesis of CPFE, we performed a series of experiments that focused on the relationships between lung elastic fibers, cigarette smoke, and secondary lung injury. The results indicate that even brief smoke exposure predisposes the lung to additional forms of lung injury that may cause alveolar wall fibrosis. The proinflammatory activity of smoke-induced structural alterations in elastic fibers may contribute to this process by enhancing secondary lung inflammation, including acute exacerbations of chronic obstructive pulmonary disease. Furthermore, the levels of the unique elastin crosslinks, desmosine and isodesmosine, in blood, urine, and sputum may serve as biomarkers for the transition from pulmonary emphysema to interstitial fibrosis. While the long-term effects of these inflammatory reactions were not examined, the current studies provide insight into the potential relationships between elastic fiber injury, cigarette smoke, and secondary lung injury. Determining the mechanisms involved in combined pulmonary emphysema and fibrosis and developing a sensitive biomarker for this type of lung injury may permit timely therapeutic intervention that could mitigate the high risk of respiratory failure associated with this condition.

Apurinic/apyrimidinic endonuclease 1 has major impact in prevention of suicidal covalent DNA-protein crosslink with apurinic/apyrimidinic site in cellular extracts.

DNA-protein crosslinks (DPC) are common DNA lesions induced by various external and endogenous agents. One of the sources of DPC is the apurinic/apyrimidinic site (AP site) and proteins interacting with it. Some proteins possessing AP lyase activity form covalent complexes with AP site-containing DNA without borohydride reduction (suicidal crosslinks). We have shown earlier that tyrosyl-DNA phosphodiesterase 1 (TDP1) but not AP endonuclease 1 (APE1) is able to remove intact OGG1 from protein-DNA adducts, whereas APE1 is able to prevent the formation of DPC by hydrolyzing the AP site. Here we demonstrate that TDP1 can remove intact PARP2 but not XRCC1 from covalent enzyme-DNA adducts with AP-DNA formed in the absence of APE1. We also analyzed an impact of APE1 and TDP1 on the efficiency of DPC formation in APE1-/- or TDP1-/- cell extracts. Our data revealed that APE1 depletion leads to increased levels of PARP1-DNA crosslinks, whereas TDP1 deficiency has little effect on DPC formation.

One-pot fabrication of bio-inspired shape-morphing bilayer structures

Soft bilayer structures capable of shape morphing in response to external stimuli have been commonly adopted in the design of soft robots, flexible electronics and many other smart systems. However, existing methods to fabricate such structures generally require multiple steps and may end up a weak interface between the two layers. Here, we report a one-pot fabrication strategy to generate elastomer-based shape-morphing bilayer structures with a seamless interface. Our strategy leverages on a recently developed bioinspired polymer-NaCl particle composite system which can undergo significant osmotic swelling in water. Bilayer structures are readily formed after the precipitation of NaCl particles in liquid polymers under gravity and the crosslinking of the polymers. The shape-morphing behavior of the fabricated bilayer structures can be well controlled by tuning the particle precipitation kinetics, NaCl content, and crosslinking level of the polymer matrix. More importantly, the bilayer structures fabricated using this strategy exhibit more complex shape-morphing responses than typical bilayer structures. Considering the wide applicability of NaCl particle-induced osmotic swelling of polymer composites, our one-pot bilayer formation strategy will greatly benefit many shape-morphing applications with a simplified fabrication workflow and enhanced configurational versatility.

Probing the influence of composition and cross-linking degree on single-chain nanoparticles from poly(tetrahydrofuran-ran-epichlorohydrin) copolymers: Insights from neutron scattering, calorimetry, and dielectric spectroscopy

The industrial sector has made significant strides in the development of multicomponent and multiphasic polymer materials, including polymer blends, composites (such as nanocomposites), and various copolymers. Random copolymers, characterized by their statistical arrangement of repeating units, are particularly noteworthy due to their tunability from amorphous to semicrystalline states. In this study, we focus on poly(tetrahydrofuran-ran-epichlorohydrin) (P(THF-ran-ECH)) copolymers, which serve as precursors for single-chain nanoparticles (SCNPs). These SCNP-based materials are of particular interest as they bridge the gap between traditional polymers and colloids. This research comprehensively investigates how the type and degree of internal cross-linking influence the structure and dynamics of P(THF-ran-ECH) copolymers and their SCNPs. Techniques such as quasielastic neutron scattering (QENS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS) were employed to study copolymers with varying compositions and levels of cross-linking. By analyzing two samples with different epichlorohydrin (ECH) contents (13 mol% and 27 mol%), we aim to control crystallization and explore its effects on dynamic behavior. Our results show that both the composition and the degree of cross-linking significantly impact the dynamics of the SCNPs, with SCNPs exhibiting slower dynamics compared to their precursor copolymers. Furthermore, semicrystalline samples display faster dynamics in SCNPs than amorphous samples. These findings provide valuable insights for the design and optimization of advanced multicomponent polymer systems.

Developing and analyzing photo-crosslinkable cinnamoyl-modified pullulan hydrogels for drug delivery applications

A hydrogel created by modifying pullulan with cinnamoyl groups (Pul-CM) through an esterification process was developed as an effective vehicle for delivering the well-known drug model, caffeine. Initially, pullulan biopolymer was expanded, followed by the addition of cinnamoyl groups using cinnamoyl chloride. These modifications were confirmed through various spectroscopic and instrumental techniques, verifying their proposed chemical structures. The newly created Pul-CM hydrogel demonstrated the ability to crosslink without initiators when exposed to UV light for sufficient durations. This crosslinking is attributed to the creation of cyclobutane rings that link the pullulan chains via a [2π+2π] cyclization process facilitated by the cinnamoyl groups' –CH=CH– bonds. The progress of Pul-CM crosslinking was tracked by the reduction in the UV spectral peak associated with the cinnamate groups, followed by an examination of the gel's efficiency and its swelling behavior under UV light. Furthermore, these hydrogel derivatives show significant promise as drug delivery systems, offering adjustable drug release rates by altering the hydrogel's crosslinking level through either cinnamoyl modification or the duration of UV light exposure.

Reducing Filamin A Restores Cortical Synaptic Connectivity and Early Social Communication Following Cellular Mosaicism in Autism Spectrum Disorder Pathways.

Communication in the form of nonverbal, social vocalization, or crying is evolutionary conserved in mammals and is impaired early in human infants that are later diagnosed with autism spectrum disorder (ASD). Defects in infant vocalization have been proposed as an early sign of ASD that may exacerbate ASD development. However, the neural mechanisms associated with early communicative deficits in ASD are not known. Here, we expressed a constitutively active mutant of Rheb (RhebS16H), which is known to upregulate two ASD core pathways, mTOR complex 1 (mTORC1) and ERK1/2, in Layer (L) 2/3 pyramidal neurons of the neocortex of mice of either sex. We found that cellular mosaic expression of RhebS16H in L2/3 pyramidal neurons altered the production of isolation calls from neonatal mice. This was accompanied by an expected misplacement of neurons and dendrite overgrowth, along with an unexpected increase in spine density and length, which was associated with increased excitatory synaptic activity. This contrasted with the known decrease in spine density in RhebS16H neurons of 1-month-old mice. Reducing the levels of the actin cross-linking and adaptor protein filamin A (FLNA), known to be increased downstream of ERK1/2, attenuated dendrite overgrowth and fully restored spine properties, synaptic connectivity, and the production of pup isolation calls. These findings suggest that upper-layer cortical pyramidal neurons contribute to communicative deficits in a condition known to affect two core ASD pathways and that these mechanisms are regulated by FLNA.

Influence of BaTiO3 substitution on structural and thermal response of lead borosilicate glass for ultrasonic applications

An extensive examination of the impact of BaTiO3 doping on the mechanical and thermal characteristics of lead-borosilicate glasses is provided in this work. The glass density increases noticeably (from 6020 for BaTiO3 to 2533 kg/m3 for SiO2), and the molar volume decreases, suggesting a denser and more compact structural arrangement. The mechanical properties exhibited a notable improvement upon the addition of BaTiO3. Specifically, the longitudinal ultrasonic velocity (VL) increased from 3927 to 4458 m/s, and the shear velocity (VS) increased from 2317 to 2630 m/s, indicating a reinforced glass network. The bulk modulus increased from 35.71 to 58.06 GPa, and Young’s modulus increased from 57.2 to 92.98 GPa. These significant increases in elastic moduli were attributed to tighter atom packing and higher levels of cross-linking within the glass matrix. Furthermore, the glass structure’s increased rigidity and connectedness were further indicated by the Debye temperature (θD), which increased from 296.8 to 347.3 K. The influence of BaTiO3 on the thermal analysis is demonstrated, which revealed that increasing BaTiO3 content raises both the glass transition and crystallization temperatures. The results of the experiment demonstrate how much BaTiO3 doping can improve the physical characteristics of lead-borosilicate glasses, enabling them to be used in sophisticated optical and structural applications.

Performance and Impact of Crosslinking Level of Hierarchical Anion-Exchange Membranes on Demineralization of a Complex Food Solution by Electrodialysis.

Promising results were recently reported for hierarchical ion-exchange membranes, fabricated by the UV crosslinking of a thin functional coating on a porous substrate, on model NaCl solution demineralization by electrodialysis (ED). Hierarchical anion-exchange membranes (hAEMs) have never been tested with complex solutions to demonstrate their potential use in the biofood industry. The impact of three different crosslinking densities of the ion-exchange coating (EbN-1, EbN-2 and EbN-3) on the performances of whey demineralization by ED was investigated and compared with commercial AMX. The results showed that by increasing the coating crosslinking density, the membrane conductivity decreased, leading to an increase in the global system resistance during whey demineralization (from +28% to +64%). However, 18% sweet whey solutions were successfully treated until 70% demineralization for all membranes. The energy consumption (averaged EbN value of 14.8 vs. 15.1 Wh for AMX) and current efficiency (26.0 vs. 27.4%) were similar to the control. Potential fouling by non-protein nitrogen was detected by ATR-FTIR for hAEMs impacting some membranes properties and ED performances. Overall, EbN-1 obtained results were comparable with the benchmark and can be considered as an alternative membrane for whey demineralization by ED and other applications in the demineralization of complex products from the food industry.

Comparative investigation of various protein or protein-based powders addition on texture properties of egg white and yolk gels

ABSTRACT The objective of this research was to investigate and compare the effects of various protein or protein-based powders (WPC, SPI, BSA and hemoglobin) addition on transform of texture properties in egg white (EW)/egg yolk (EY) gels. Results showed that the highest hardness value (38.5 N) was detected in BSA-treated EW gels, while the lowest values (46.6 N) were obtained in hemoglobin-treated EY gels. Additionally, significantly increased value of free –SH groups was obtained in SPI/BSA/hemoglobin-treated EW/EY solutions, and increased value of protein solubility was obtained in EY solutions treated by WPC/SPI/BSA/hemoglobin relative to those of the control. The EW solutions treated by BSA/hemoglobin reached significantly higher H 0 values than those of other groups. SDS-PAGE analysis showed that the hemoglobin-treated EW solution had slightly intense bands of ovoinhibitor, ovotransferrin and ovalbumin, and the EY solutions treated by WPC/SPI/BSA had higher level of covalent crosslinking. The EW gels treated by WPC/hemoglobin exhibited relatively more ordered protein secondary structures (α-helix and β-sheet) than those of the SPI group. SEM results suggested that WPC/BSA-treated EW gels developed uniform, porous and fiber-like structure, while SPI/BSA-treated EY gels developed rougher structure.

Intra-organ cell specific mitochondrial quantitative interactomics.

Almost every organ consists of many cell types, each with its unique functions. Proteomes of these cell types are thus unique too. But it is reasonable to assume that interactome (inter and intra molecular interactions of proteins) are also distinct since protein interactions are what ultimately carry out the function. Podocytes and tubules are two cell types within kidney with vastly different functions: podocytes envelop the blood vessels in the glomerulus and act as filters while tubules are located downstream of the glomerulus and are responsible for reabsorption of important nutrients. It has been long known that for tubules mitochondria plays an important role as they require a lot of energy to carry out their functions. In podocytes, however, it has been assumed that mitochondria might not matter as much in both normal physiology and pathology1. Here we have applied quantitative cross-linking mass spectrometry to compare mitochondrial interactomes of tubules and podocytes using a transgenic mitochondrial tagging strategy to immunoprecipitate cell-specific mitochondria directly from whole kidney. We have uncovered that mitochondrial proteomes of these cell types are quite similar, although still showing unique features that correspond to known functions, such as high energy production through TCA cycle in tubules and requirements for detoxification in podocytes which are on the frontline of filtration where they encounter toxic compounds and therefore, as a non-renewing cell type they must have ways to protect themselves from cellular toxicity. But we gained much deeper insight with the interactomics data. We were able to find pathways differentially regulated in podocytes and tubules based on changing cross-link levels and not just protein levels. Among these pathways are betaine metabolism, lysine degradation, and many others. We have also demonstrated how quantitative interactomics could be used to detect different activity levels of an enzyme even when protein abundances of it are the same between cell types. We have validated this finding with an orthogonal activity assay. Overall, this work presents a new view of mitochondrial biology for two important, but functionally distinct, cell types within the mouse kidney showing both similarities and unique features. This data can continue to be explored to find new aspects of mitochondrial biology, especially in podocytes, where mitochondria has been understudied. In the future this methodology can also be applied to other organs to uncover differences in the function of cell types.

Influence of Crosslinking Concentration on the Properties of Biodegradable Modified Cassava Starch-Based Films for Packaging Applications.

Chitosan/modified cassava starch/curcumin (CS/S/Cur) films with a crosslinker were developed via the solvent casting technique for the application of food packaging. The effects of citric acid (CA) as a natural crosslinker were assessed at different concentrations (0-10.0%, w/w, on a dry base on CS and S content). To measure the most favorable film, chemical structure and physical, mechanical, and thermal properties were investigated. Successful crosslinking between CS and S was seen clearly in the Fourier Transform Infrared (FTIR) spectra. The properties of the water resistance of the CS/S/Cur films crosslinked with CA were enhanced when compared to those without CA. Furthermore, it was found that the addition of CA crosslinking would improve the mechanical properties of composite films to some extent. It had been reported that the CA crosslinking level of 7.5 wt% of CS/S/Cur film demonstrated high performance in terms of physical properties. The tensile strength of the crosslinked film increased from 8 ± 1 MPa to 12 ± 1 MPa with the increasing content of CA, while water vapor permeability (WVP), swelling degree (SD), and water solubility (WS) decreased. An effective antioxidant scavenging activity of the CS/S/Cur film decreased with an increase in CA concentrations. This study provides an effective pathway for the development of active films based on polysaccharide-based film for food packaging applications.

High-Performance Dopamine-Based Supramolecular Bio-Adhesives.

The need for wound closure or surgical procedures has been commonly met by the application of sutures. Unfortunately, these are often invasive or subject to contamination. Alternative solutions are offered by surgical adhesives that can be applied and set without major disruption; a new class of supramolecular-based adhesives provides potential solutions to some of these challenges. In this study, a series of polymers utilizing dopamine as a self-assembling unit are synthesized. It is found that these motifs act as extremely effective adhesives, with control over the mechanical strength of the adhesion and materials' tensile properties enabled by changing monomer feed ratios and levels of cross-linking. These materials significantly outperform commercially available bio-adhesives, showing yield strengths after adhesion at least two times higher than that of BioGlue and Tisseel, as well as the ability to re-adhere with significant recovery of adhesion strength. Promisingly, the materials are shown to be non-cytotoxic, with cell viability > 90%, and able to perform in aqueous environments without significant loss in strength. Finally, the removal of the materials, is possible using benign organic solvents such as ethanol. These properties all demonstrate the effectiveness of the materials as potential bio-adhesives, with potential advantages for use in surgery.

Association between CTX-1 and Fibulin-1 Serum Levels with Pathogenesis of Multiple Myeloma Cancer.

Multiple myeloma (MM) is the second most prevalent blood cancer after non-Hodgkin lymphoma. It is identified by the excessive production of abnormal monoclonal immunoglobulins, which can result in various clinical symptoms such as destructive bone lesions, renal dysfunction, anemia, and immunodeficiency. The current study aims to evaluate the serum levels of carboxy-terminal collagen crosslinks 1 (CTX-1), Fibulin-1, vitamin D3, LDH, and albumin in MM patients and their significance for early diagnosis. This study included 30 healthy controls (11 males, 19 females) and 60 patients with multiple myeloma (37 males and 23 females), aged between 40-60 years. Five-milliliter blood samples were collected and stored at -20°C. Afterward, enzyme-linked immunosorbent assay (ELISA) kits were used to estimate the concentrations of CTX-1, Fibulin-1, and vitamin D3. Additionally, LDH and albumin levels were determined using the automated biochemistry analyzer. This study revealed that the majority of patients with multiple myeloma are between the ages of 51 and 60 years. The serum concentrations of CTX-1, Fibulin-1, and LDH were significantly increased in the multiple myeloma patients compared to the healthy control group. In contrast, the serum level of vitamin D3 was significantly decreased in patients with MM. Our results indicate that the incidence of multiple myeloma is higher in males than in females. Additionally, the serum concentrations of CTX-1 and Fibulin-1 were significantly higher in the multiple myeloma patients compared to the healthy control group, indicating their potential for early detection and as therapeutic targets.

Fatty alcohols as sustainable compatibilizer agents for the compound of natural rubber/silica: The curing, rubberiness and tensile strength behaviours

Fatty alcohols are derived from palm oil production and, stearyl and lauryl alcohols are examples of them. The stearyl and lauryl alcohols have the potential to be used as rubber additives for the compounding and vulcanizing processes. These materials are relatively new as rubber additives and, they were added into silica-filled natural rubber (NR) compound. The aim of using them is to increase the grade of silica dispersion inside the NR matrix. Initially, the NR was filled by (precipitate) silica at 30 parts per hundred of NR, whilst the fatty alcohols were added into the silica-filled NR with variable concentrations from 1 to 4 phr, separately. The compounds of NR/silica/stearyl alcohol and NR/silica/lauryl alcohol have been vulcanised at 150 °C by implementing a semi-efficient rubber composition. From the vulcanization behaviour, it was observed that both fatty alcohols have the role of compatibilizer and plasticising agents for the compound of NR/silica. Those fatty alcohols decreased the viscousness but increased the curing rate index (CRI). The more concentration of fatty alcohols was supplied, the less viscousness and the higher the CRI. Those fatty alcohols also shifted the crosslinking level and tensile strength. It also observed that the break elongation or rubberiness has been shifted up. Tensile strength has been shifted to a maximal value with a 2 phr of stearyl alcohol or 3 phr of lauryl alcohol addition.

Effect of vulcanisation on the properties of natural rubber-modified asphalt

Natural rubber (NR), a bio-based polymer, has significant potential for economic and environmental sustainability when used as an asphalt modifier in flexible pavements. In this study, natural rubber-modified asphalt (NRMA) was produced and the effects of vulcanisation on NRMA were investigated. The results showed that vulcanisation can improve the stiffness and elasticity of NRMA, thereby strengthening its resistance to deformation at high loads and temperatures. Specifically, vulcanisation increased the rutting factor of NRMA by 1.5, increased the elastic recovery by 60%, and decreased the temperature-sensitivity factor by 6.75%. In addition, the softening-point difference (SPD) of vulcanised natural rubber-modified asphalt (VNRMA) was significantly reduced by 36.8%, and the thermal-storage stability was improved. The micromorphology and changes in chemical bonds that occurred in VNRMA revealed that vulcanisation not only deepened the level of crosslinking between NR and asphalt, but also refined the NR particles, making NR more uniformly dispersed within the asphalt phase. By creating new chemical bonds, vulcanisation reinforced the NR network structure and change the main modification method for asphalt using NR from physical to chemical modification. This improved the rheological and mechanical properties of NRMA. The results of this study provide new solutions for NRMA applications and help improve its performance and application scope.

Enhancing the Quality of Low-Salt Silver Carp (Hypophthalmichthys molitrix) Surimi Gel Using Psyllium Husk Powder: An Orthogonal Experimental Approach.

Low-salt surimi production is crucial as it addresses health concerns related to sodium intake while maintaining the quality and shelf-life of seafood products. This research focused on optimizing the gelation conditions for silver carp surimi with the addition of psyllium husk powder at low salt concentrations (0.5% and 1%, w/w) to investigate the effects of psyllium husk powder concentration, temperature, and time on gel strength and water-holding capacity. The quality was assessed in terms of gel strength and water-holding capacity. Following a single-factor exploration, a three-level orthogonal experiment was designed to evaluate the influence of these three variables using a combined scoring system. Results indicated that psyllium husk powder levels between 0.1% and 0.3% (w/w) enhanced gel strength and water-holding capacity. The optimal conditions were identified as follows: 1% (w/w) NaCl with 0.2% (w/w) psyllium husk powder for 2.5 h at 35 °C, and 0.5% (w/w) NaCl with 0.3% (w/w) psyllium husk powder for 3 h at 35 °C. Texture profile analysis revealed that psyllium husk powder increased the hardness of the surimi gel, promoting myosin cross-linking and denser gel structure. Compared to traditional surimi gel, which relies on ionic bonds, the optimized gel showed higher levels of disulfide cross-linking and enhanced hydrophobic interactions, resulting in a stronger gel structure. Sensory evaluation suggested that surimi gels with psyllium husk powder were perceived as better than those without psyllium husk powder. The study concludes that selecting the appropriate psyllium husk powder quantity and thermal processing conditions based on salt concentration can significantly improve the quality of low-salt surimi gels. Error analysis using one-way ANOVA was performed on all experimental data and (p < 0.05) indicated the significant difference.

Enhancing the tire performances of truck tire tread based on rubber compounds containing biobased processing oil by adjusting sulfur contents

The mechanical properties of the rubber compounds such as modulus and tensile strength are very important to rubber products especially for tire applications. However, the presence of palm oil (PO) as a biobased processing oil in eco-friendly truck tire tread compounds encounters the low mechanical properties because PO molecules can consume sulfur as a curing agent. Therefore, this study focuses on incorporation of sulfur in varying contents on the properties of rubber compounds. The PO-added natural rubber compounds with different sulfur contents of 2.50, 2.75, and 3.00 parts per hundred rubber (phr) were prepared by taking the use of distillated aromatic extract (DAE) in natural rubber compound with 2.50 phr sulfur as a reference. The levels of crosslinking of the PO-added natural rubber compounds increased as the sulfur content increased, resulting in improvement in mechanical properties. Results showed that an additional incorporation of 0.25 phr sulfur content led to superior mechanical properties. Furthermore, PO improved the abrasion resistance by 38%, reduced heat buildup by 17%, and lowered tan δ at 60°C by 21%, when compared to the compound as a reference. Based on the results, the additional incorporation of sulfur not only improved the mechanical properties, but also enhanced tire performances especially low rolling resistance as reflected by energy-saving tires. Thus, PO can be an alternative to DAE in the natural rubber compounds for the application of truck tire treads when the additional incorporation of sulfur was applied.

Identifying the Influences on Network Formation in Structural Isomers of Multifunctional Epoxies Using Near-Infrared Spectroscopy.

The network formation of four epoxy-rich formulations of the structural isomers of triglycidyl aminophenol and diaminodiphenyl sulfone has been monitored by using two complementary techniques, near-infrared spectroscopy and resin temperature monitoring. The differences between these networks have been described using the concentration of epoxide, primary amine, secondary amine, and tertiary amine functional groups and the actual temperature of the resin compared to the oven temperature during the cure schedule. It was found that initially, the 3,3'-diaminodiphenyl sulfone (33'DDS) formulations were more reactive and primary amines were completely consumed before the 4,4'-diaminodiphenyl sulfone (44'DDS) formulations. Secondary amines were formed more quickly in 33'DDS formulations compared to 44'DDS. The triglycidyl-meta-aminophenol (TGmAP) formulations consumed secondary amines and produced tertiary amines faster than the triglycidyl-para-aminophenol (TGpAP) formulations, indicating higher levels of cross-linking occurred earlier in the curing reaction. Etherification occurred much earlier in the TGpAP formulations than in the TGmAP formulations. Results suggest that internal cyclization occurs in the three meta isomer-containing formulations, and a corresponding lack of this effect in TGpAP/44'DDS results in a more homogeneous cross-linked network.