Cross-linked Systems Research Articles

Biofabrication of Cell-Laden Gelatin Methacryloyl Hydrogels with Incorporation of Silanized Hydroxyapatite by Visible Light Projection.

Gelatin methacryloyl (GelMA) hydrogel is a photopolymerizable biomaterial widely used for three-dimensional (3D) cell culture due to its high biocompatibility. However, the drawback of GelMA hydrogel is its poor mechanical properties, which may compromise the feasibility of biofabrication techniques. In this study, a cell-laden GelMA composite hydrogel with a combination incorporating silanized hydroxyapatite (Si-HAp) and a simple and harmless visible light crosslinking system for this hydrogel were developed. The incorporation of Si-HAp into the GelMA hydrogel enhanced the mechanical properties of the composite hydrogel. Moreover, the composite hydrogel exhibited low cytotoxicity and promoted the osteogenic gene expression of embedded MG63 cells and Human bone marrow mesenchymal stem cells (hBMSCs). We also established a maskless lithographic method to fabricate a defined 3D structure under visible light by using a digital light processing projector, and the incorporation of Si-HAp increased the resolution of photolithographic hydrogels. The GelMA-Si-HAp composite hydrogel system can serve as an effective biomaterial in bone regeneration.

Mucoadhesive properties of nanogels based on stimuli-sensitive glycosaminoglycan-graft-pNIPAAm copolymers

Mucoadhesive formulations capable of situ gelation are promising for improving ocular drug delivery. Here we investigated two types of nanogels based on anionic glycosaminoglycans with grafted thermo-responsive poly(N-isopropylacrylamide) chains. One type of nanogels were formed by thermo-induced gelling of heparin-graft-poly(N-isopropylacrylamide) and chondroitin sulfate-graft-poly(N-isopropylacrylamide) copolymers. Another type of nanogels was based on the same copolymers, but terminal groups of thermosensitive macromolecular chains were modified to form covalent disulfide cross-links. All types of nanogels were studied towards their ability to encapsulate and release model drug – dexamethasone. Mucoadhesivity of both thermo-gelled and covalently cross-linked polymeric systems, as well as their ability to interact with dexamethasone, was assessed by microscale thermophoresis (MST). Mucoadhesion properties were also evaluated by isothermal titration calorimetry (ITC), which were in good correlation with MST data. The presence of disulfide linkages and thiol groups were shown to favor improved binding of cross-linked nanogels to mucin. Moreover, in vivo intraocular pressure studies showed that presence of polymers in solution can alter the ocular absorption of carbonic anhydrase inhibitor from eyedrops. The pharmacological effect was in line with mucoadhesive properties of these copolymers.

Prediction of Viscoelastic Properties of Enzymatically Crosslinkable Tyramine-Modified Hyaluronic Acid Solutions Using a Dynamic Monte Carlo Kinetic Approach.

The present study deals with the mathematical modeling of crosslinking kinetics of polymer–phenol conjugates mediated by the Horseradish Peroxidase (HRP)-hydrogen peroxide (H2O2) initiation system. More specifically, a dynamic Monte Carlo (MC) kinetic model is developed to quantify the effects of crosslinking conditions (i.e., polymer concentration, degree of phenol substitution and HRP and H2O2 concentrations) on the gelation onset time; evolution of molecular weight distribution and number and weight average molecular weights of the crosslinkable polymer chains and gel fraction. It is shown that the MC kinetic model can faithfully describe the crosslinking kinetics of a finite sample of crosslinkable polymer chains with time, providing detailed molecular information for the crosslinkable system before and after the gelation point. The MC model is validated using experimental measurements on the crosslinking of a tyramine modified Hyaluronic Acid (HA-Tyr) polymer solution reported in the literature. Based on the rubber elasticity theory and the MC results, the dynamic evolution of hydrogel viscoelastic and molecular properties (i.e., number average molecular weight between crosslinks, Mc, and hydrogel mesh size, ξ) are calculated.

Constitutive modeling of elastomers during photo- and thermo-oxidative aging

In this study, we proposed a micro-mechanical model to describe the effects of temperature and UV radiation on the constitutive behavior of cross-linked polymeric systems such as elastomers. Specifically, the focus of this model is to predict the effects of photo-oxidative aging on the mechanical response of cross-linked systems and their inelastic responses such as permanent set and Mullins effect. With regard to experimental studies on the nature of chemical reactions during aging, chain scission and bond creation should be considered as two competing phenomena that happens simultaneously, though at different rates. Consequently, cross-link density across the matrix might increase or decrease in the course of photo-oxidative aging, depending on the rate of reactions. The rates are functions of temperature, UV radiation intensity and time. In view of the competition between these two mechanisms, the elastomer can be damaged differently during aging which may lead to a harder or softer matrix, or even in more complicated cases, change between hardening and softening in due time. Therefore, strain energy of the polymer matrix should be calculated with regard to time, temperature and UV radiation intensity. Using this experimental analysis, we proposed a new micro-mechanical model. Since separating the effects of thermo-oxidation and photo-oxidation seemed impossible, the proposed model is a generalized micro-mechanical model for both thermo-oxidative and photo-oxidative aging. Therefore, the model has two sets of parameters. One that its components only are a function of temperature and another that are a function of both temperature and UV radiation intensity. To validate the model, comprehensive set of experimental data has been conducted. The proposed model shows promising result with great precision.

Albumin-Based Nanoparticles for the Delivery of Doxorubicin in Breast Cancer.

Simple SummaryDoxorubicin (Dox) is a chemotherapeutic agent usually employed for the treatment of breast cancer. However, its use is limited because of the toxicities associated, and hence a proper delivery vehicle is necessary. In this sense, albumin-based nanocarriers are in the limelight for the successful delivery of chemotherapeutics because of safety, biocompatibility, and specific cancer-targeting properties. Herein, we have developed a nanocarrier system based on albumin, which selectively affects the tumor cells, and hence can revolutionize breast cancer therapy. The developed nanoparticles could be further used for the delivery of other hydrophobic drugs like SN38, which broadens the use of this system in the treatment of breast cancer.Albumin-based nanoparticles are an emerging platform for the delivery of various chemotherapeutics because of their biocompatibility, safety, and ease of surface modification for specific targeting. The most widely used method for the preparation of albumin nanoparticles is by desolvation process using glutaraldehyde (GLU) as a cross-linker. However, limitations of GLU like toxicity and interaction with drugs force the need for alternative cross-linkers. In the present study, several cross-linking systems were evaluated for the preparation of Bovine Serum Albumin (BSA) nanoparticles (ABNs) encapsulating Doxorubicin (Dox). Based on the results obtained from morphological characterization, in vitro release, and therapeutic efficacy in cells, N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP)-modified ABNs (ABN-SPDP) was chosen. Since ABN-SPDP are formed with disulfide linkage, the drug release is facilitated under a highly reducing environment present in the tumor sites. The cytotoxicity studies of those ABN-SPDP were performed in three different breast cell lines, highlighting the mechanism of cell death. The Dox-encapsulated ABN-SPDP showed toxicity in both the breast cancer cells (MCF-7 and MDA-MB-231), but, remarkably, a negligible effect was observed in non-tumoral MCF-10A cells. In addition to the hydrophilic Dox, this system could be used as a carrier for hydrophobic drugs like SN38. The system could be employed for the preparation of nanoparticles based on human serum albumin (HSA), which further enhances the feasibility of this system for clinical use. Hence, the albumin nanoparticles developed herein present an excellent potential for delivering various drugs in cancer therapy.

Lignin-Based Polymer Electrolyte Membranes for Sustainable Aqueous Dye-Sensitized Solar Cells.

In the quest for sustainable materials for quasi-solid-state (QS) electrolytes in aqueous dye-sensitized solar cells (DSSCs), novel bioderived polymeric membranes were prepared in this work by reaction of preoxidized kraft lignin with poly(ethylene glycol)diglycidylether (PEGDGE). The effect of the PEGDGE/lignin relative proportions on the characteristics of the obtained membranes was thoroughly investigated, and clear structure–property correlations were highlighted. In particular, the glass transition temperature of the materials was found to decrease by increasing the amount of PEGDGE in the formulation, indicating that polyethylene glycol chains act as flexible segments that increase the molecular mobility of the three-dimensional polymeric network. Concurrently, their swelling ability in liquid electrolyte was found to increase with the concentration of PEGDGE, which was also shown to influence the ionic transport efficiency within the membrane. The incorporation of these lignin-based cross-linked systems as QS electrolyte frameworks in aqueous DSSCs allowed the preparation of devices with excellent long-term stability under UV–vis light, which were found to be superior to benchmark QS-DSSCs incorporating state-of-the-art carboxymethylcellulose membranes. This study provides the first demonstration of lignin-based QS electrolytes for stable aqueous DSSCs, establishing a straightforward strategy to exploit the potential of lignin as a functional polymer precursor for the field of sustainable photovoltaic devices.

Self-crosslinkable hyaluronate-based hydrogels as a soft tissue filler

With increasing interest in aging and skin care, the use of fillers to increase the volume of soft tissue volume is increasing globally. However, the side effects caused by the residual chemical crosslinking agents present in these fillers limit the effective application of commercialized filler products. Therefore, the development of a novel crosslinking system with a non-toxic chemical crosslinking agent is required to overcome the limitations of commercial hyaluronate (HA)-based fillers. In this paper, a new injectable hydrogel with enhanced mechanical properties, tissue adhesion, injectability, and biocompatibility is reported. The HA derivatives modified with catechol groups (HA-DA) were crosslinked by self-oxidation under in vivo physiological conditions (pH 7.4) without chemical crosslinkers to form hydrogels, which can be further accelerated by the dissolved oxygen in the body. The fabricated HA-DA filler showed excellent mechanical properties and could be easily injected with a low injection force. Further, the HA-DA filler stably attached to the injection site due to the tissue adhesion properties of the catechol groups, thus leading to an improved displacement stability. In addition, the HA-DA filler showed excellent cell viability, cell proliferation, and biocompatibility. Therefore, the HA-DA hydrogel is a novel soft tissue filler with great potential to overcome the limitations of commercial soft tissue fillers.

Preparation and characteristics of crosslinked fluorinated acrylate modified waterborne polyurethane for metal protection coating

The use of coatings to protect metals from corrosion is currently a common practice. In this study, a double bond-terminated waterborne polyurethane prepolymer was firstly synthesized from polycaprolactone polyol, toluene diisocyanate, dimethylolpropionic acid and hydroxyethyl methacrylate. Then, waterborne polyurethane prepolymer was modified with styrene, butyl acrylate, glycidyl methacrylate, and dodecafluoroheptyl methacrylate though soap-free emulsion polymerization method in order to obtain the crosslinked fluorinated acrylate modified waterborne polyurethane (CFWPUA). The CFWPUA emulsion was used as the matrix resin to prepare the coating with a bar coater, which possesses the characteristics of external hydrophobic surface constructed by long fluorinated side-chains and internal double cross-linking system. The results of infrared spectrum analysis proved the successful synthesis of modified waterborne polyurethane. The energy-dispersive X-ray spectroscopy results showed that the long fluorine side-chains partially migrate to the surface of the coating during the curing process, which leads to the occurrence of fluorine enrichment on the surface. When the glycidyl methacrylate content is 5 wt% and the dodecafluoroheptyl methacrylate content is 7.5 wt%, the water absorption rate of the membrane reduces to 7.9%, the water contact angle of the coating reaches 102.5°, and the gel content is 91%, which proved the successful construction of the double cross-linking system and prevents the penetration of water molecules. The pencil hardness of CFWPUA coating can reach 3H and flexibility and adhesion properties are at the highest level. Most importantly, in the electrochemical impedance spectroscopy test, the modified waterborne polyurethane coating effectively protects Q235 metal substrate from corrosion in the 3.5 wt% NaCl solution, the impedance modulus of CFWPUA coating could be maintained at about 107 Ω·cm2 for a long time, the resistance of CFWPUA coating slowly decreased from 2.124 × 107 Ω·cm2 to 9.605 × 106 Ω·cm2 within 10 days of immersion, two-time constant was generated after 12 days of immersion, which is slightly superior compare to commercial waterborne fluorocarbon coating. The modified waterborne polyurethane coating prepared here shows a potential practical application in the field of metal anti-corrosion.

Enhanced durability performance of cracked and uncracked concrete by means of smart in-house developed superabsorbent polymers with alkali-stable and -unstable crosslinkers

For the past two decades, research on the use of superabsorbent polymers (SAPs) in cementitious materials has proven that these innovative materials have the potential to become a suitable admixture in the concrete industry. Not until recently, most of the applications studied made use of SAPs originally designed to be used in other industries, such as in food, agricultural and hygiene products. In this paper, an innovative “in-house” developed SAP (SAPX) is presented, designed with a double crosslinking system specifically for applications in concrete structures. Its efficiency is compared with two commercially available SAPs (SAP1 and SAP2) for different applications. The “in-house” developed SAP promoted an immediate sealing effect of cracked concrete specimens as reflected by a reduction of 72% in the water permeability of specimens with cracks up to 250 µm compared to specimens without SAPs. A superior performance was also found against frost attack in salt scaling after 28 cycles of freezing and thawing. Although no complete mitigation of shrinkage was noticed, SAPX promoted a significant reduction in the shrinkage strain at early ages and up to 28 days. In terms of mechanical properties, SAPX reduced the strength to a comparable extent as SAP1 and less than SAP2. To conclude, SAPX showed a better performance compared to the already commercialized SAPs and has a high potential towards large-scale production to be exploited for concrete applications.

Cellular therapy for myocardial ischemia using a temperature-responsive biodegradable injectable polymer system with adipose-derived stem cells

ABSTRACT Adipose-derived stem cell (AdSC) has been attracting attention as a convenient stem cell source. Not only AdSC can differentiate into various tissue cells, but it can also accelerate cell proliferation, anti-inflammation, and angiogenesis by secreting paracrine factors. Studies have demonstrated AdSC treatment of ischemic heart. However, an improvement in the remaining live AdSCs administered at the injected site while maintaining paracrine factor secretion is desired to achieve effective regenerative medicine. We previously reported the ABA-type tri-block copolymer of poly(ɛ-caprolactone-co-glycolic acid) and poly(ethylene glycol) (tri-PCG), exhibiting temperature-responsive sol-to-gel transition as biodegradable injectable polymer (IP) systems. Moreover, we recently reported that the biodegradable temperature-triggered chemically cross-linked gelation systems exhibited longer gel state durations using tri-PCG attaching acryloyl groups and a polythiol derivative. In this study, we explored this IP-mediated AdSC delivery system. We investigated the cell viability, mRNA expression, and cytokine secretion of AdSCs cultured in the physical or chemical IP hydrogels. Both of these IP hydrogels retained a certain number of viable cells, and RT-PCR and ELISA analyses revealed that mRNA expression and secretion of vascular endothelial growth factor of the AdSCs cultured in the chemical hydrogel were higher than the physical hydrogel. Moreover, AdSCs injected with the chemical hydrogel into ischemic heart model mice showed longer retention of the cells at the injected site and recovery from the ischemic condition. The results mean that the IP system is a promising candidate for a stem cell delivery system that exhibits the recovery of cardiac function for myocardial infarction treatment.

Study on swelling and drug releasing behaviors of ibuprofen-loaded bimetallic alginate aerogel beads with pH-responsive performance

Bimetallic alginate aerogel beads were prepared by ionotropic gelation method with Ca2+-Ba2+ bimetallic solution and ibuprofen was loaded as a model drug. The swelling and drug releasing behaviors of the beads, especially the influence of barium, were investigated in artificial gastric and intestinal fluids. The results showed that these beads presented higher encapsulation efficiency due to the special structure of aerogel, and barium was beneficial for the more stable structure and drug releasing behavior. The lower swelling capacity of bimetallic beads was observed than monometallic beads. A rapid high-level releasing of ibuprofen was achieved in artificial intestinal fluid, which was up to 96.9% within 1 h, while ibuprofen releasing was avoided in artificial gastric fluid effectively. The drug releasing mechanism of these beads was explored in detail. In the bimetallic crosslinking system, Ba2+ presented a special effect on alginate beads with more sensitive pH response performance. Thus, these beads had more widely potential as a site-specific delivery system, especially for intestinal therapy.

Influence of Fillers and Ionic Liquids on the Crosslinking and Performance of Natural Rubber Biocomposites

This work concerns the effect of fillers and ionic liquids on the cure characteristics of natural rubber (NR) compounds, as well as the mechanical and thermal properties of the vulcanizates. Three types of white filler were applied, such as cellulose, nanosized silica and hydrotalcite, to modify the performance of NR composites. Additionally, ionic liquids (ILs) with bromide anion and different cations, i.e., 1-butyl-3-methylimidazolium (Bmi) and 1-butyl-3-methylpyrrolidinium (Bmpyr), were used to improve the cure characteristics of NR compounds and functional properties of the vulcanizates. The type of filler and the structure of ILs were proved to affect the rheometric properties and cure characteristics of NR compounds as well as the performance of the NR vulcanizates. Owing to the adsorption of curatives onto the surface, silica reduced the activity of the crosslinking system, prolonging the optimal vulcanization time of NR compounds and reducing the crosslinking degree of the elastomer. However, silica-filled NR exhibited the highest thermal stability. Hydrotalcite increased the crosslink density and, consequently, the mechanical properties of the vulcanizates, but deteriorated their thermal stability. ILs beneficially influenced the cure characteristics of NR compounds, as well as the crosslink density and mechanical performance of the vulcanizates, particularly those filled with silica. Cellulose did not significantly affect the vulcanization of NR compounds and crosslink density of the vulcanizates compared to the unfilled elastomer, but deteriorated their tensile strength. On the other hand, cellulose improved the thermal stability and did not considerably alter the damping properties of the vulcanizates.

Rationally designed protein cross-linked hydrogel for bone regeneration via synergistic release of magnesium and zinc ions

The development of recombinant protein cross-linked injectable hydrogels with good mechanical strength and effective drug loading capacity for bone regeneration is extremely attractive and rarely reported. Here, we report the fabrication of a smart hydrogel delivery system by incorporating a rationally designed T4 lysozyme mutant (T4M) to mediate the localized delivery and synergistic release of Mg2+ and Zn2+ for bone repair. Apart from its intrinsic antibacterial properties, T4M bears abundant free amine groups on its surface to function as effective covalent crosslinkers to strengthen the hydrogel network as well as exhibits specific binding affinity to multivalent cations such as Zn2+. Moreover, the integrin receptor-binding Arg-Gly-Asp (RGD) sequence was introduced onto the C-terminus of T4 lysozyme to improve its cellular affinity and further facilitate rapid tissue regeneration. The final composite hydrogel displays excellent injectability, improved mechanical properties, antibacterial activity, and unique bioactivities. The effective loading of Mg2+/Zn2+ in the hydrogels could mediate the sequential and sustained release of Mg2+ and Zn2+, thereby resulting in synergistic enhancement on bone regeneration through modulation of the MAPK signaling pathway. We believe that the strategy proposed in this paper opens up a new route for developing protein cross-linked smart delivery systems for tissue regeneration.

ACID-LABILE CORE CROSS-LINKED MICELLES FOR pH-TRIGGERED RELEASE OF DOXORUBICIN

A acid-labile core cross-linked micelle system of amphiphilic triblock copolymer of poly(oligo(ethylene glycol) methyl ether methacrylate)-block-poly(styrene-alt-maleic anhydride)-block-poly(styrene) (POEGMA-b-PSMA-b-PS) was prepared. The POEGMA-b-PSMA-b-PS triblock copolymers were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization. Doxorubincin (DOX) was entrapped into micellar structure with POEGMA block as a shell and PSMA-b-PS block as a core. Then, core cross-linking was carried out by amidation reaction between 2,2-bis(aminoethoxy)propane and maleic anhydride group inner core. DOX loading content and efficiency were calculated to be 18 and 90 (wt. %), respectively. Core cross-linked micelles illustrated good stability under physiological condition but disassociated rapidly under acidic pH. The DOX release experiments indicated a rapid DOX release at pH 5.0 compared to pH 7.4.

Hot-Melt Adhesive Based on Dynamic Oxime–Carbamate Bonds

Polyurethane hot-melt adhesives featured with high adhesion strength and environmental friendliness possess broad applications in many fields. However, their practical application is hindered by existing drawbacks such as low adhesion strength and poor recyclability for thermoplastic polyurethane and reactive polyurethane hot-melt adhesives, respectively. Achieving high adhesion strength and efficient recycling for hot-melt adhesives simultaneously is challenging. Herein, reversible covalent bonds (oxime–carbamate) were introduced to construct a three-dimensional dynamically cross-linked polyurethane system which has the merits of favorably reworkable thermoplastic polyurethane hot-melt adhesives and high adhesive reactive polyurethane hot-melt adhesives to accomplish efficient bonding–debonding conversion on demand. Such a structure provided a high cross-linked covalent network and a fast reversible adhesive property, and hence improved the overall performance of holt-melt adhesives. As a result, the adhesive exhibited an impressive initial and ultimate adhesion strength of 5.96 ± 0.61 MPa (5 min curing) and 9.02 ± 1.36 MPa (10 days curing), respectively. More remarkably, favorable repeated adhesive capability was realized even after it was completely broken four times, while still retaining all above 4.40 ± 0.92 MPa. In addition, this adhesive also possessed excellent solvent resistance and good durability. Our work emphasized the importance of molecular design and a general method for strong and efficient adhesive systems.

Development and Evaluation of an Acidic Shear-Tolerant Nanosheet-Enhanced Cross-Linked Gel System for Hydrofracturing

Acidic fracturing fluids, such as zirconium cross-linked carboxymethyl hydroxypropyl guar gum (CMHPG), can not only adapt to formations treated with CO2 but also protect such formations from the da...

3D Bioprinting of Reinforced Vessels by Dual-Cross-linked Biocompatible Hydrogels.

3D bioprinting offers a powerful tool to fabricate vessel channels in tissue engineering applications, but inadequate strength of the vascular walls limited the development of this strategy and reinforced channels were highly desired for vascular constructions. Herein, we demonstrated a dual cross-linking system for 3D bioprinting of tubular structures, achieved by a combination of photo-cross-linking and enzymatic cross-linking. Photo-cross-linking of gelatin methacryloyl (GelMA) was achieved with a photoactive conjugated polymer PBF under 550 nm irradiation. Enzymatic cross-linking utilized cascade reactions catalyzed by glucose peroxidase and horseradish peroxidase that can cross-link both methacrylate and tyrosine moieties of GelMA. After removing the 3D-printed sacrificial layer (Pluronic F-127), the obtained perfusable channels showed great biocompatibility that allowed endothelial cells to adhere and proliferate. Our dual cross-linking strategy has great potential in 3D bioprinting of tubular structure for biomedical applications, especially for artificial blood vessels.

Review on the Conceptual Design of Self-Healable Nitrile Rubber Composites.

The search for suitable strategies to manufacture self-healable nitrile rubber (NBR) composites is the most promising part in the industrial field of polar rubber research. In recent years, some important strategies, specifically, metal–ligand coordination bond formation, ionic bond formation, and dynamic hydrogen bond formation, have been utilized to develop duly self-healable NBR composites. This paper reviews the continuous advancement in the research field related to self-healable NBR composites by considering healing strategies and healing conditions. Special attention is given to understand the healing mechanism in reversibly cross-linked NBR systems. The healing efficiency of a cross-linked NBR network is usually dependent on the definite interaction between functional groups of NBR and a cross-linking agent. Finally, the results obtained from successful studies suggest that self-healing technology has incredible potential to increase the sustainability and lifetime of NBR-based rubber products.

Enabling reprocessability of ENR-based vulcanisates by thermochemically exchangeable ester crosslinks

ABSTRACT A reprocessable elastomeric vulcanisate based on Epoxidised Natural Rubber with 50 mol-% epoxide content (ENR-50) was evloved by applying a self-assembled network based on thermochemically exchangeable ester crosslinks to the system. Hydrolysed Maleic Anhydride (HMA) as crosslinking substance in the presence of 1,2-DiMethylImidazole (DMI) as esterification accelerator and Zinc Acetate Dihydrate (ZAD) as transesterification catalyst was employed to generate the exchangeable ester crosslinking system. A sulphur-cured ENR-50 vulcanisate possessing a permanent sulphide crosslinking network was prepared as reference. Based on the results from cure characteristic and chemical structure analyses, the ENR-50 crosslinked with HMA behaves as a dynamic network because of a transesterification reaction catalysed by ZAD, promoting an exchangeable crosslinking network in the system. This dynamic network contributes to an intermolecular rearrangement of the ester crosslinking bonds at elevated temperatures, enabling interfacial self-adhesion and so reprocessability of the vulcanisates. The obtainable vulcanisates can be reprocessed, yielding relatively high retention of mechanical properties compared to their pristine counterpart. The interfacial self-adhesion and reprocessability of the vulcanisates have shown to significantly be improved with a higher loading of ZAD and elevated temperatures. This concept essentially shows a prospect towards developing e.g. novel recyclable and self-healing systems for elastomers.

Research and development of ultra-high temperature delayed crosslinking acid system

The average burial depth of carbonate reservoirs in Shunbei area exceeds 7300 meters, and the bottom hole temperature is as high as 160°C. The commonly used cross-linked acid system cannot meet the needs of acid fracturing. Therefore, this article uses AM, AMPS, acrylamide (AM) modified monomers, acrylic acid (AA) modified monomers to synthesize thickener SBCH-1, the organic zirconium crosslinking agent SBJL1 was synthesized with zirconium oxychloride, isopropanol, citric acid and diethanolamine. And other auxiliary agents are selected, and the final formula is determined as: 220% HCl+0.8% SBCH-1 thickener +0.8% SBJL-lcrosslinking agent +0.8% SBYC-1 crosslinking retarder +2% SBHS-1A high temperature corrosion inhibitor +2% SBHS-1B high temperature corrosion inhibitor +1% SBTW-4 iron ion stabilizer +1% SBZP-2 drainage aid +1% SBPR-1 demulsifier. The viscosity of the system stabilized above 200mPa⋅s after continuous shearing at 160°C, 170s-1 for 30min.