Polymer Science, Series B最新文献

This article focused on preparing high-ortho phenolic resin using phenol and formaldehyde as precursors and using zinc acetate as catalysts. High ortho-phenolic fibers were produced through wet spinning, solution thermal curing (STC), microwave thermal curing (MTC), and heat treatment techniques. The structural and mechanical properties of the fibers were evaluated using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), micro-infrared imaging (Micro-FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TG), mechanical testing and scanning electron microscopy (SEM). The high-ortho phenolic fibers experienced a reduction in hydroxymethyl groups and an augmentation in methylene groups upon microwave curing, which enhanced cross-linking. Through the escalation of solution cross-linking bath and heat treatment, the hydroxymethyl groups within the phenolic molecules underwent a reaction to form methylene groups. Methylene groups facilitated the increase of intramolecular crosslinking degree, thereby enhancing the stability of the fibers structure. As a result, the mechanical properties of the fibers were improved and reached an optimal level under microwave heat curing, with an elongation of 3.1% and a tensile strength of 107 MPa.

Reducing the stress defects of grain caused by high temperature curing is of great significance to the safety and performance of propellant. Here, a series of alkenyl polyethylene glycol copolymers (APEG) were designed and synthesized using polyethylene glycol (PEG) samples and allyl glycidyl (AGE) and glycidol as raw materials. The APEG copolymers were cured at room temperature with nitrile oxide prepared in situ from p-benzenedinitrile oxide and triethylamine. The chemico-physical properties of the precursors and cured systems were discussed. The results showed that the tensile strength, the elongation at break and hardness decreased from the case of PEG 400 to the case of PEG 4000 and increased from the case of PEG 4000 to the case of PEG 6000. And the elongation at break of the cured APEGs decreased, the tensile strength increased with the increase of curing agent’s contents. The in situ IR of this cured system was analyzed and k = 0.1888 g/(mol min) at 27°C. The initial thermal decomposition of this cured system was also discussed. The activation energy and reaction order were calculated respectively as 163.886 kJ/mol and 0.96. The results suggested that the prepared binder could be cured rapidly at room temperature and had greater heat release during high temperature decomposition. Based on the excellent room curing performance and great heat release of this work, The APEG copolymers provide a feasible strategy to solve the problems caused by the high temperature curing.

It has been shown that adamantane-containing diamines are highly reactive under conditions of single-stage high-temperature cyclization in a sulfolane–toluene mixture of solvents. Polyimides with the reduced viscosity of 1.3‒1.4 dL/g have been synthesized on their bases, the films of which have exhibited good thermal properties and low yellowness index (1.1‒1.2).

To extend the service life of concrete in harsh environments, this paper introduces a silicone-modified polyurethane with self-repairing capabilities. The integration of silicone and disulfide bonding into the polyurethane molecular chain endows the material with a self-repairing ability and hydrophobicity. The incorporation of silicone significantly enhances the polyurethane’s hydrophobicity, while the introduction of disulfide bonds enables damage repair under mild conditions, and the repair efficiency can reach 90%. This combination of hydrophobicity and self-repairing properties holds paramount importance in protecting concrete and ensuring its prolonged use.

In the description of multicenter ion-coordination polymerization of isoprene on the catalytic system GdCl₃· n(i-C₃Н₇OH)‒Al(i-C₄H₉)₃ the inverse kinetic task for the scheme of a process with slow initiation has been solved. The task of determining the number of active centers of polymerization was solved by deconvolution of experimental MWDs through superposition of Flory distributions. It has been shown that four types of active centers participate in polymerization, the kinetic difference of which in the process of formation of polymer fractions with their characteristic average molecular weights and the most probable MWD, is associated with their difference in the concentrations of pre-reaction catalytic centers and the rate constants of reactions occurring on them. For each type of active centers, partial conversions of monomer consumption and rate constants of initiation, chain propagation, and chain transfer to the monomer are determined.

In light of the persistent challenges in herbicide release control, this study aims to investigate the factors influencing the release rate of herbicides from polymer–montmorillonite clay composites. Understanding these factors can provide valuable insights for the development of improved controlled release systems, offering enhanced precision and efficiency in herbicide delivery. Polymer-montmorillonite clay composites carrying 2,4-dichlorophenoxy acetic acid as controlled release systems were prepared by in-situ polycondensation. The intercalated polymeric 2,4-dichlorophenoxy acetic acid composites were characterized using various analytical techniques. Release studies were conducted in aqueous media at different pH levels over an extended period of approximately 80 days. The results revealed the significant influence of various factors on the release rate of the herbicide, including polymer structure, medium composition, percentage of polymer grafting onto clay, clay-to-polymer ratio, and swelling behavior. These findings have important implications for the development of controlled release systems for herbicides. Understanding the factors influencing release rates enables the optimization of composite design and formulation for efficient herbicide delivery. Moreover, this research provides a foundation for future investigations aimed at enhancing the release performance and overall effectiveness of polymer-montmorillonite clay composites. Potential avenues for further research include exploring tailored polymer structures, modifying the clay matrix, and optimizing the clay-to-polymer ratio.

Silicone-modified polyurethane has low silicon content and instability of the synthesis process limits its application expansion. In this study, the waterborne organosilicon acrylic polyurethane prepolymer emulsion with high silicon content (WSi_hAPU) were prepared by using hydroxy-terminated polydimethyl siloxane as soft segments. Waterborne organosilicon acrylic polyurethane (WSiAPU) can be controlled by simple mixing the ratio of WSi_hAPU and waterborne acrylic polyurethane (WAPU) in different proportions, and the WSiAPU films were freely regulate their silicon content range at 0–11.6%. Series WSiAPU emulsions had excellent storage stability, which can be diluted mechanically to a concentration of 0.1% and stored for up to 6 months. The structure and properties of the WSiAPU samples, their films by UV cured and the fabric subtract coating WSiAPU composites were characterized by the X-ray Photoelectron spectroscopy (XPS), the water contact angle (WCA) and water absorption rate (WAR), etc. This resulted in an increase in the hydrophobicity of WSi_hAPU and WSiAPU. The WCA and the WAR of the WSiAPU films increased to 108.79° and decreased to 6.44%, and the WAR of the WSiAPU treated fabric substrates Cotton was reduced from 705.12 to 4.12%. This resulted in an increase in the hydrophobicity of WSi_hAPU and WSiAPU.

Liquid hydridopolycarbosilanes (LHPCS) is commonly used to produce ceramic matrix composites by polymer impregnation pyrolysis (PIP) process. Allyl-substituted hydridopolycarbosilanes (AHPCS) with different allyl contents of 10, 15, 20, 25 and 30 mol % (AHPCS-10%, AHPCS-15%, AHPCS-20%, AHPCS-25%, AHPCS-30%) were synthesized by Grignard coupling reaction. tert-Butyl peroxybenzoate (TBPB) + cobalt 2-ethylhexanoate (Co) were used as the redox initiation system for AHPCS curing and was compared with Karstedt catalyst and TBPB initiator. Based on differential scanning calorimetry analyses, the TBPB + Co initiation system significantly decreased the exothermic peak temperature of the free radical polymerization to 80°C. According to thermogravimetric analysis, the residual at 1000°C of cured AHPCS-20% in flowing nitrogen reached to 86.0%. Ceramized AHPCS were obtained by heat treated cured AHPCS at 1500°C for 2 h. Based on the X-ray diffraction patterns and transmission electron microscope photographs of the ceramic products, β-SiC was the main component of the ceramized AHPCS. Ceramized AHPCS-15% was the highest ceramic yield of 88.1% in the ceramized AHPCS. Thermogravimetric analyses revealed high thermal oxidation resistance of the ceramic AHPCS in flowing air up to 1000°C. Therefore, AHPCS under TBPB + Co initiation system with low-temperature curability and high ceramic yield, and its ceramic products have excellent thermal oxidation resistance, showing potential as SiC ceramic precursors for aerospace field.

Electrically conductive composite textile and textile combining electrically conductive and magnetic properties have been obtained on the basis of biocompatible non-toxic materials: commercial non-woven textiles, electrically conductive polypyrrole and magnetite (Fe₃O₄). The composite textile has been formed from two-layer fibers, where the fibers of the original textile are coated with a polypyrrole shell, and the textile combining electrically conductive and magnetic properties have had a three-layer structure, where magnetite particles are deposited on top of the polypyrrole shell. The composite textiles have retained the structure of the original fabric with free interfiber space: the specific surface area of the materials and their mechanical properties have been similar in value. The composition of materials, their electrically conductive, magnetic, and redox properties have been investigated. The interaction of the composite textile and the textile combining electrically conductive and magnetic properties with electromagnetic radiation in the frequency range of 4–8 GHz have been investigated in comparison with a commercial radio-absorbing material based on carbonyl iron.

β-ocimene (3,7-dimethyl-1,3,6-octatriene), a dimer of isoprene, which can be found in various essential oils such as ocimium plant genus, holds the potential to serve as a source material for creating elastomers entirely derived from bio-based sources. Due to its structural similarity to myrcene (C₁₀H₁₆), this conjugated diene, offers the possibility of undergoing polymerization using the same method employed for myrcene. This involves the utilization of neodymium trisborohydride as a pre-catalyst activated by boron derivatives in the presence of triisobutyl aluminum. This innovative approach has led to the successful production of 1,4-cis polyocimene, a significant achievement in the field of polymer chemistry. Detailed analysis through the application of ¹³C NMR and DEPT 135 spectroscopy has shed light on the microstructure of the resulting polyocimene. It has been revealed that the polymer exhibits a predominant microstructure of 1,4‑cis (comprising up to 83.38% of the structure) along with the presence of 1,2-trans isomer (constituting 16.62%). The findings also highlight that the molecular weight distributions of the polymer are relatively broader (PDI > 2). This catalytic system enables the production of polymers that can be used as promising starting materials for bio-based thermoplastic elastomers.