The rapid development of aerospace technology has put demands on the high tough thermosetting resins. Polytriazole (PTA) resins are a kind of high performance thermosetting resins as matrices of ...structural composites for aerospace parts. It is necessary to develop polytriazole resins with high toughness. In this paper, propargyl‐terminated polypropylene glycols (PtPGs) with various molecular weights (PtPG400, PtPG600, PtPG725) were synthesized and characterized. A series of PtPG‐toughened polytriazole (PPTA) resins were prepared by the “Click” reaction of PtPG and N,N,N′,N′‐tetrapropargyl‐4,4′‐diaminodiphenylmethane (TPDDM) with 1,1‐bisazidomethyl‐4,4′‐biphenyl (BAMBP). The curing behavior of the PPTA resins and the thermal, mechanical, as well as water absorption of the cured PPTA resins were investigated. The results show that the PPTA resins have excellent processing properties and can be cured and molded at 80°C. The molecular weight and the amount of PtPG have a significant influence on the mechanical properties of PPTA resins. When PtPG600 with the molar ratio of alkyne groups 1.0% is formulated, the impact strength of the cured PPTA‐600‐1.0 resin reaches 63.6 ± 8.2 kJ·m−2 and KIC 2.57 MPa·m−1/2, which are 57.4% and 41.2% higher than those of PTA resin respectively. The glass transition temperature (Tg) and water absorption of the cured PPTA‐600‐1.0 resin are 223.8°C and 0.22% respectively.
Toughened polytriazole resins with heat resistance and low water absorption
Phosphorus-containing flame retardants synthesized from renewable resources have had a lot of impact in recent years. This article outlines the synthesis, characterization and evaluation of these ...compounds in polyesters and epoxy resins. The different approaches used in producing biobased flame retardant polyesters and epoxy resins are reported. While for the polyesters biomass derived compounds usually are phosphorylated and melt blended with the polymer, biobased flame retardants for epoxy resins are directly incorporated into the polymer structure by a using a phosphorylated biobased monomer or curing agent. Evaluating the efficiency of the flame retardant composites is done by discussing results obtained from UL94 vertical burning, limiting oxygen index (LOI) and cone calorimetry tests. The review ends with an outlook on future development trends of biobased flame retardant systems for polyesters and epoxy resins.
In polymer science and industry, the important role of thermosetting resin is well-recognized. However, most thermosets suffer from the overdependence on petroleum resource and in addition are linked ...to environmental concerns. The development of sustainable thermosetting resins thus has become an objective of contemporary research. Addressing this need generally requires renewable feedstocks, satisfied comprehensive properties, and long service life or recyclability. Herein, a systematic overview regarding recent advances in sustainable thermosetting resins is provided. Firstly, the origins and access of bio-based platform compounds successfully applied in the bio-based thermosetting resins are being discussed. Subsequently, the synthesis, structure-property relationships, and methodologies for the functionalization of three typical bio-based thermosets, including benzoxazine, epoxy resin and unsaturated polyester, are being reviewed. Finally, strategies for the recycling of bio-based thermoset waste products are being presented. The objective of this work is not only to summarize the recent progress on sustainable thermosets, but also help us understand them more deeply and widely in a short time, so as to promote their faster development.
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The flame retardant polypropylene containing the micro‐envelope core‐shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine‐formaldehyde resin and sodium silicate ...through in situ polymerization was prepared with polyamide 6, added as a carbon‐forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine‐formaldehyde resin and the micro‐envelope core‐shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char‐forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core‐shell flame retardant that sodium silicate and melamine‐formaldehyde resin‐coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL‐94 reached the V‐0 level.
A comprehensive review of the publications about rosin-based chemicals has been compiled. Rosin, or colophony, is a natural, abundant, cheap and non-toxic raw material which can be easily modified to ...obtain numerous useful products, which makes it an excellent subject of innovative research, attracting growing interest in recent years. The last extensive review in this research area was published in 2008, so the current article contains the most promising, repeatable achievements in synthesis of rosin-derived chemicals, published in scientific literature from 2008 to 2018. The first part of the review includes low/medium molecule weight compounds: Especially intermediates, resins, monomers, curing agents, surfactants, medications and biocides. The second part is about macromolecules: mainly elastomers, polymers for biomedical applications, coatings, adhesives, surfactants, sorbents, organosilicons and polysaccharides. In conclusion, a critical evaluation of the publications in terms of data completeness has been carried out with an indication of the most promising directions of rosin-based chemicals development.
The use of natural fiber reinforcements for the production of ecofriendly composites has arisen considerable interest both in thermoplastic and thermoset based materials. In the latter case, the ...matrix is often an epoxy based polymer, which allows remarkable performance, but that cannot be considered eco-friendly since it is non-biodegradable and is produced from non-renewable sources. This strongly impairs the environmental friendly character of the resulting composite material. The aim of this work was to study the characteristics and performance of a thermoset bioepoxy resin, which is partly based on natural components, to be used in hemp reinforced laminates. The permeability of the hemp fabric as well as the rheological and thermal behavior of the resin were studied in view of their fabrication by resin infusion techniques. The results showed that laminated composites could be easily obtained with a vacuum assisted resin transfer molding process. Static, dynamic and vibration-damping tests were performed to evaluate limits and potentials of such biocomposites.
A polyacrylate-based wetting agent, BYK-358N, was used to improve the interfacial bonding between the bamboo fibers and epoxy matrix. Fourier transform infrared spectrometer and differential scanning ...calorimetry were used to study the curing process of epoxy resin. The wettability of the treated bamboo fiber, which by the untreated and wetting agent treated epoxy, was studied using the surface tension of epoxy and bamboo fiber. The analysis of dynamic contact angle and interfacial shear stress confirmed that the composite interface was improved. Finally, Vacuum-assisted resin transfer molding was used to prepare bamboo fiber reinforced epoxy resin (BF/EP) composites, and the tensile properties were measured. The results showed that the addition of the wetting agent could effectively improve the interface compatibility of BF/EP composites. The interfacial shear stress of BF/EP composites treated with 1% wetting agent was 24.36 MPa, tensile strength was 111.54 MPa, and Young's modulus was 3.90 GPa, which was 165.7%, 99.7%, and 66.7% higher than that of untreated BF/EP composites.
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Biodegradable materials based on poly (lactic acid) (PLA) and a phenolic free modified rosin resin were obtained and studied to control the biodegradability under composting conditions of the ...materials. The resin was blended in concentrations of 1, 3, 5, 10, and 15 parts per hundred (phr) of base polymer using industrial plastic processing techniques. Additionally, to study the effect of the resin on the compatibility of the PLA, the physical performance, water absorption, mechanical behavior, thermal stability, and microstructure of the materials were assessed. The resin incorporation decreased the resistance to thermal degradation of the resultant material, and the composting disintegration rate was slowed down with the increasing content of the resin. The water diffusion was delayed, and the diffusion and corrected diffusion coefficients decreased with the rising content of UP. The mechanical properties tend to decrease while a saturation effect was observed for contents higher than 3 phr of resin. The optimal amount of resin that can be added to achieve good interaction with PLA matrix, complete miscibility, and good material cohesion is 3 phr.
In vitro and in vivo studies have clearly identified that some components of restorative composite resins, adhesives, and resin-modified glass ionomer cements are toxic. The mechanisms of ...cytotoxicity are related firstly to the short-term release of free monomers occurring during the monomer–polymer conversion. Secondly, long-term release of leachable substances is generated by erosion and degradation over time. In addition, ion release and proliferation of bacteria located at the interface between the restorative material and dental tissues are also implicated in the tissue response. Molecular mechanisms involve glutathione depletion and reactive oxygen species (ROS) production as key factors leading to pulp or gingival cell apoptosis. Experimental animal approaches substantiate the occurrence of allergic reactions. There is a large gap between the results published by research laboratories and clinical reports.
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