Papers by Keyword: Cross-Linking

Abstract: The growing demand for sustainable alternatives to petroleum-based polymer materials has driven the development of bio-based materials. Among them, chitosan stands out as a promising biopolymer due to its biodegradability and biocompatibility. However, its hydrophilicity, causing high water absorption, limits its practical applications. In this study, tannic acid was employed as a cross-linking agent, and chitin nanofibers (ChNFs) were introduced as a reinforcing agent to enhance the properties of the chitosan-based films. The incorporation of ChNFs significantly improved the tensile stress of the films without compromising their transparency. Furthermore, the cross-linked chitosan films with ChNFs exhibited excellent UV-blocking capabilities. This highlights their potential as an alternative to conventional petroleum-based polymers.

Abstract: Hydrogels are cross-linked polymeric structures, which consist of up to approximately 90% water, the remainder is polymer chain. Retention of large volumes of water in the intermolecular space is related to the presence of hydrophilic functional groups in the network. The unique hydrogels properties, such as porosity, and biological and mechanical properties, make them suitable for a wide range of applications, especially in the medical sector. Furthermore, ease of modification and good printability are expected in 3D bioprinting technologies. Nevertheless, to maintain their structure and softness, hydrogels must be stored in suitable conditions to prevent water vaporization. The water removal from the hydrogel network results in weight reduction, structural and volumetric changes. It is a considerable challenge for the printouts manufactured by 3D bioprinting technology, where hydrogel products are exposed to drying during the production process, which may affect their shape change and shrinkage. The paper presents a crosslinking process of a hydrogel-based on sodium alginate and the shrinkage of dried hydrogels depending on the crosslinking procedure. An investigation focused on the alginate hydrogel water content, as well as shrinkage of alginate hydrogel degree depending on the concentration of the cross-linking (CaCl₂) solution and the duration of the process. For longer cross-linking time or using higher cross-linking agent concentration, the cross-linking was more efficient. However, it is necessary to optimize the parameters for the bioprinting process.

Abstract: A new type of polymer emulsion was prepared by the copolymerization of DAAM and VAc monomer with high solid content and storage stability. By addition of ADH (ketonic hydrazide cross-linking reaction), the polymer emulsion can be cross-linked at room temperature. It was found that the degree of cross-linking of the polymer reaches 71.85%, and the resistance to boiling water reaches 180min at the maximum of DAAM of 2% and DAAM / ADH = 1/1.

Abstract: Wood plastic composite (WPC) has been rapidly developed because of its environmental friendliness and sustainability. In order to improve the interfacial compatibility between plant fiber and polypropylene (PP) matrix, three different cross-linking modification methods were used to treat corn straw fiber (CSF). These methods were glutaraldehyde/chitosan (GA/CS) crosslinking modification, KH560/chitosan crosslinking modification and glutaraldehyde/polyvinyl alcohol (GA/PVA) crosslinking modification. The characterization and the mechanical analysis of WPC showed that different cross-linking methods have different morphology on the surface of CSF. Compared with CSF-PP, the bending strength of GA/CS-CSF-PP and GA/PVA-CSF-PP were increased by 11.1% and 16.7%, respectively. This study provided appropriate methods to improve the interface compatibility between plant fiber and resin matrix.

Abstract: A peroxide induced reaction was applied as a cross-linking method for Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biomaterial gate dielectrics. PHBV was effectively cross-linked with a peroxide inducer at a relatively low temperature (90°C). The cross-linked microstructures improve the thermal stability compared with uncross-linked PHBV. This peroxide induced cross-linking method was compatible with plastic substrates for flexible electronic applications. The cross-linked PHBV thin films displayed smooth surfaces.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper studies the effect of different doses of ionizing beta radiation on the micro-mechanical properties of commercially available polyamide. The measured results indicate, that electron beam irradiation is very effective tool for improvement of surface properties of PA6. In terms of micro-mechanical properties, the values of micro-hardness of surface layer increased by 24% at radiation dose of 132 kGy, stiffness of surface micro layer by 26% (132 kGy) as a result of different loads (0.5N and 2N). Improvement of micro-mechanical properties of radiated polyamide has a great significance also for industry. The modified polyamide shifts to the group of materials that have considerably better properties. Its micro-mechanical properties make polyamide ideal for a wide application in areas where higher resistance to wear, creep are required. Commonly manufactured PA6 can hardly fulfil these criteria.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behavior. This paper describes the effect of electron beam irradiation on the nanoindentation creep of unfilled and glass fiber filled polypropylene (25%). nanoindentation creep were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (0, 30, 45 and 60 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nanoindentation creep measured by the DSI method. The unfilled and filled polypropylene tested showed significant changes of indentation creep. The measured results indicate, that electron beam irradiation is very effective tool for improvement of creep properties of unfilled and filled polypropylene. The nanoindentation creep after irradiated unfilled Polypropylene was decreased up to 16 % (filled polypropylene was decreased up to 9%) compared to non-irradiated surface. These changes were examined and confirmed by Gel content.

Abstract: The characteristics of 3D cross-linking, mechanical properties and biocompatibility of new copolymers of polyetherurethane and polysiloxane are presented. New copolymers are shown to be highly durable, strong and stable, thus being prospective for various applications including biomedical implants.

Abstract: Glutaraldehyde cross-linked silk sericin films were successfully prepared. FTIR was applied to characterize the chemical structure of films. Compared to pure silk sericin, cross-linked silk sericin film with 3% glutaraldehyde was found a new peak at 1620 cm^-1 and the peak intensity of cross-linked film decreased markedly, which indicating cross-linking reaction has been occurred. Thermal and swelling behavior of cross-linked films was investigated. The cross-linking reaction increased the thermal decomposition temperature. The swelling ratio of glutaraldehyde cross-linked silk sericin films went up with increasing glutaralehyde loading to 3wt%.

Abstract: This study investigated a novel crosslinking agent for epoxidized natural rubber (ENR). The result showed that it was possible to thermally crosslink ENR with maleic anhydride (MA). No additional catalyst was needed. FT-IR spectra revealed that after heating the ENR mixed with MA, there was the formation of the ester linkages. The crosslinking of ENR via these newly formed linkages was confirmed by the formation of gel once the heated rubber sample was immersed in toluene. The rheographs indicated that the crosslinking can take place at 80 °C and the curing rate and degree of crosslinking were dependent of the MA content. The cured ENR with MA showed higher decomposition temperature and better tensile strength than the uncured one.