Addition‐cure phenolic resins based on propargyl ether functional novolacs: synthesis,curing and properties

Thermosetting phenolic resins, bearing varying extents of propargyl ether groups (PN resins), have been synthesized by the Williamson reaction of a novolac with propargyl bromide and the products characterized. The resin precursors were cured through Claisen rearrangement of the propargyl ether groups and thermal polymerization. The activation energy for thermal cure is substantially lower than that of model bispropargyl ether compounds but is quite independent of the degree of functionalization. The isothermal cure profile, extrapolated from non‐isothermal DSC kinetics studies is consistent with the results from DMA studies. The mechanical properties of glass composites of the resins, of varying propargyl contents, reveal good consolidation of the interphases, evident from the initial gain in both interlaminar shear strength (ILSS) and flexural strength. The benefits of better resin–reinforcement interactions are not retained on crosslinking the resin further, wherein the composite fails by a combination of fibre debonding and brittle fracture of the matrix. Although the resins show better thermal stability than cured resoles, a higher extent of propargylation is detrimental for the thermal stability. Resins with moderate propargylation show good mechanical and thermal properties. © 2001 Society of Chemical Industry     

Structure and properties of amine‐hardened epoxy/benzoxazine hybrids: Effect of epoxy resin functionality

Bifunctional, trifunctional, and tetrafunctional epoxy resins (EP) were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was 100/0, 75/25, 50/50, and 25/75 wt %, respectively. Information on the structure of the hybrid systems was received from differential scanning calorimetry, dynamic‐mechanical thermal analysis, atomic force microscopy, and fractographic studies. The flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. The thermal degradation and fire resistance of the hybrids were also studied. It was found that the polymerized BOX was built in the network in from of nanoscale inclusions and acted as antiplasticizer. Incorporation of BOX enhanced the flexural modulus and strength and reduced the glass transition temperature of the parent EP. The fracture toughness and energy were practically not improved by hybridization with BOX. The charring and flame resistance were improved with increasing amount of BOX in the EP/BOX hybrids. The relative improvement in the latter was most prominent for the bifunctional EP/BOX systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

苯并嗯嗪树脂阻燃改性研究进展

苯并嗯嗪是一类经开环聚合得到的新型酚醛树脂,具有良好的耐热性、阻燃性,并且在固化时不释放出小分子物质。苯并嗯嗪虽然具有较好的阻燃性能,但仍不能满足某些应用场合需要。本文介绍了舍磷、含硅以及含其他官能团的阻燃剂用于苯并嗯嗪体系的阻燃效果。     

Dual‐Cure Thermoset Amide‐ and Acrylate‐Functionalized Latexes

A dual‐cure latex is prepared by mixing an amide‐functionalized latex with a latex that has both acetoacetoxy and unsaturated acrylic functionalities. The amide‐functionalized latex provides a thermal cure with the acetoacetoxy groups of the other latex via Michael addition. The partially polymerized triacrylates in the acrylate‐functionalized latex provide active sites for photocuring. Thermoset latex films are prepared by blending amide‐ and acrylate‐functionalized latexes in varying amounts. The effect of the photosensitizer (camphorquinone) concentration on thermal and mechanical properties is studied. The highest tensile modulus and elongation is observed in a 50:50 wt% amide/acrylate‐functionalized latex blend.

     

Condensation–addition‐type resole resins with phenyl ethynyl functions: Synthesis,characterization, and thermal properties

Novel phenolic resins bearing methylol and phenyl ethynyl functions and curing by both condensation and addition mechanisms were synthesized by the reaction of 3‐(phenyl ethynyl) phenol (PEP) with formaldehyde under alkaline conditions. Resins with varying relative concentration of the two functional groups were synthesized and characterized. The resins underwent a two‐stage cure, confirmed by both DSC and DMA analyses. The low‐temperature cure due to methylol condensation led to early gelation of the system. The ultimate curing through addition reaction of phenylethynyl group required heating at 275°C. The cured resins exhibited better thermal stability and anaerobic char yield in comparison to a conventional resole. The thermal stability and char‐yielding property showed a diminishing trend with enhanced methylol substitution. Resin with F/P ratio less than unity offered excellent thermal stability and anaerobic char yield. The thermal degradation of the cured resins occurred in two kinetic steps. Methylene groups favored the initial degradation, whereas the higher temperature carbonization process was independent of the network structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3371–3377, 2001     

New thermosetting resin from bisphenol A‐based benzoxazine and bisoxazoline

Bisphenol A‐based benzoxazine was prepared from bisphenol A, formaline, and aniline. Curing reaction of bisphenol A‐based benzoxazine with bisoxazoline and the properties of the cured resin were investigated. Consequently, using triphenylphosphite as a catalyst, for the first time the ring‐opening reaction of benzoxazine ring occurred at 170°C, and then the phenolic hydroxyl group generated by the ring‐opening reaction of the benzoxazine ring reacted with the oxazoline ring at 200°C. The melt viscosity of the molding compound was kept 0.1–1 Pa · s at 140°C even after 1.5 h, and increased rapidly at 180°C. It was realized that the molding compound showed good flowability below 140°C, curing reaction proceeded above 180°C rapidly. The cured resin from bisphenol A‐based benzoxazine and bisoxazoline showed good heat resistance, water resistance, electrical insulation, and mechanical properties, compared with the cured resin from bisphenol A‐type novolac and bisoxazoline. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1551–1558, 1999     

Functionalization of lignin: Synthesis of lignophenol‐graft‐poly(2‐ethyl‐2‐oxazoline) and its application to polymer blends with commodity polymers

Lignophenol (LP)‐graft‐poly(2‐ethyl‐2‐oxazoline) (POZO) was prepared to reuse lignin, an industrial waste material, and to produce novel LP‐based polymer blends with poly(vinyl chloride) (PVC), poly(bisphenol A carbonate) (PC), polyvinylpyrrolidone (PVP), and polystyrene (PSt) as commodity polymers. The resulting graft polymer was soluble in various types of organic solvents such as chloroform, THF, acetone, and methanol, unlike LP. The miscibility of LP‐graft‐POZO with commodity polymers was measured by differential scanning calorimetry (DSC) to determine the glass transition temperatures (T_g). In the cases of the blends of LP‐graft‐POZO with PVC, PC, and PVP, the T_g values decreased during the second scan. Moreover, in the cases of the blends with PVC and PVP, the T_g values were not detected during the third scan. Therefore, it was inferred that LP‐graft‐POZO was miscible with PVC, PC, and PVP while forming single phases; in particular, the blends of LP‐graft‐POZO with PVC and PVP exhibited a secondary miscibility because the T_g values were not detected. Furthermore, the blend of LP‐graft‐POZO with PC exhibited better thermostability than LP and LP‐graft‐POZO. These results indicated that LP blended with POZO could be used as a polymer additive and as an adhesive to combine different polymers, organic–inorganic polymers, etc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polybenzoxazine‐based composites as high‐performance materials

Polybenzoxazines are newly developed thermoset polymers exhibiting versatility in a wide range of applications including in the electronics and aerospace industries. When combined as composites, the attractive characteristics of both components are apparent. The chemistry of benzoxazine synthesis offers wide molecular design flexibility and thus facilitates preparation of various polybenzoxazine‐based composites. This article reviews recent developments in the preparation and thermal curing of benzoxazine composites with a focus on structure–property relations of cured materials. Copyright © 2010 Society of Chemical Industry     

New type of phenolic resin: Curing reaction of phenol‐novolac based benzoxazine with bisoxazoline or epoxy resin using latent curing agent and the properties of the cured resin

In this study, we aimed to reduce the cure time, and to lower the cure temperature of the benzoxazine compound. Therefore, curing reaction of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent and the properties of the cured resins were investigated. The cure behavior of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent was monitored by differential scanning calorimetry and measurements for storage modulus (G′). The properties of the cured resin were estimated by mechanical properties, electrical insulation, water resistance, heat resistance, and flame resistance. As a result, it was confirmed that by using the latent curing agent, cure time of benzoxazine and bisoxazoline or epoxy resin was reduced, and cure temperature was lowered. And it was found that the curing reaction using phenol‐novolac based benzoxazine (Na) as the benzoxazine compound could proceed more rapidly than that using bisphenol‐A based benzoxazine (Ba) as the benzoxazine compound. However, the cured resins from Ba and bisoxazoline or epoxy resin using the latent curing agent showed good heat resistance, flame resistance, and mechanical properties compared with those from Na and bisoxazoline or epoxy resin using the latent curing agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cure kinetics and rheology characterization of soy‐based epoxy resin system

A novel soy‐based epoxy resin system was synthesized by the process of transesterification and epoxidation of regular soy bean oil, which has the potential to be widely usable in various composite manufacturing processes. Cure kinetics and rheology are two chemical properties commonly required in process modeling. In this work, the cure kinetics and rheology of the soy‐based resin system were measured by means of differential scanning calorimetry (DSC) and viscometer. DSC was used to measure the heat flow of dynamic and isothermal curing processes. The cure kinetics models of the different formulations were thus developed. A Brookfield viscometer was used to measure the change in viscosity under isothermal conditions. A novel neural network‐based model was developed to improve modeling accuracy. The models developed for cure kinetics and rheology for soy‐based epoxy resin system can be readily applied to composite processing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3168–3180, 2006     

一种高性能刹车片胶粘剂的研究

研究了一种盘式刹车片胶粘剂,可以在140℃／5min定位,180℃后处理0.5小时破坏达到95％以 上,从常温到400℃均达到刹车片材料破坏,而且成本只是相当于普通酚醛树脂。几乎可以用于各种刹车片 的粘接。     

2010年我国热固性工程塑料进展

根据2010年国内公开发表的文献,综述了我国热固性树脂及塑料的开发研究状况。2010年我国热固性工程塑料的研究开发重点是大品种树脂的高性能化改性和新型结构热固性树脂的开发。利用纳米粒子、液晶聚合物等对传统热固性工程塑料的改性取得了较多的成果,对互穿网络聚合物、梯度材料、特种功能材料的研究也有逐渐增多的趋势。     

New thermosetting resin from poly(p‐vinylphenol) based benzoxazine and epoxy resin

Poly(p‐vinylphenol) (VP) based benzoxazine was prepared from VP, formaline, and aniline. The curing behavior of the benzoxazine with the epoxy resin and the properties of the cured resin were investigated. Consequently, the curing reaction did not proceed at low temperatures, but it proceeded rapidly at higher temperatures without a curing accelerator. The reaction induction time or cure time of the molten mixture from VP based benzoxazine and epoxy resin was found to decrease, compared with those from conventional bisphenol A based benzoxazine and epoxy resin. The curing reaction rate of VP based benzoxazine and epoxy resin increased more than that of conventional bisphenol A based benzoxazine and epoxy resin. The properties of the cured resin from neat resins and from reinforced resins with fused silica were evaluated. The cured resins from VP based benzoxazine and epoxy resin showed good heat resistance, mechanical properties, electrical insulation, and water resistance compared to the cured resin from VP and epoxy resin using imidazole as the catalyst. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 555–565, 2001     

Phenolic resins with phenyl maleimide functions: Thermal characteristics and laminate composite properties

Phenolic resins bearing varying concentrations of phenyl maleimide functions were synthesized by copolymerizing phenol with N‐(4‐hydroxyphenyl)maleimide (HPM) and formaldehyde in the presence of an acid catalyst. The resins underwent a two‐stage curing, through condensation of methylol groups and addition polymerization of maleimide groups. The cure characterization of the resin by dynamic mechanical analysis confirmed the two‐stage cure and the dominance of maleimide polymerization over methylol condensation in the network buildup process. The kinetics of both cure reactions, studied by the Rogers method, substantiated the earlier proposed cure mechanism for each stage. Although the initial decomposition temperature of the cured resin was not significantly improved, enhancing the crosslink density through HPM improved thermal stability of the material in a higher temperature regime. The anaerobic char yield also increased proportional to the maleimide content. Isothermal pyrolysis and analysis of the char confirmed that pyrolysis occurs by loss of hydrocarbon and nitrogenous products. The resins serve as effective matrices in silica‐ and glass fabric–reinforced composites whose mechanical properties are optimum for moderately crosslinked resins, in which failure occurs through a combination of fiber debonding and resin fracture. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1664–1674, 2001     

Gelation via cationic chelation/crosslinking of acrylic‐acid‐based polymers

The gelation characteristics of acrylic‐acid‐based polymers in the presence of a range of cationic species, namely Ca²⁺, Mg²⁺ and Al³⁺, were investigated using in situ rheological measurements during photo‐polymerisation. Fourier transform mechanical spectroscopy was used to identify the gel point, using the Winter–Chambon criteria which allow the gel point to be pinpointed by establishing the sample spanning network and quantitatively determining stiffness, relaxation exponent, gel stiffness and fractal dimensions. The results showed that the gelation processes were greatly influenced by the type of cationic species that was used in the syntheses. At the gel point, more open network clusters were formed when Al³⁺ cations were used instead of Ca²⁺ cations or Mg²⁺ cations, all relating to chloride salts. Although the concentrations of the chelating/crosslinking aluminium species affected the kinetics of the gelation, the critical gel characteristics were hardly affected. Also the solubility of the chosen aluminium salt was shown to dictate the crosslinking rates and the properties of the critical gels. The extents of the reactions and the types of network formed at the gel point and beyond indicated that reactions between the Al³⁺ ions and COOH sites, from growing poly(acrylic acid) molecular chains, differ from those exhibited by Mg²⁺ and Ca²⁺ ions. All of the chelation/crosslinking reactions met the criteria of low mutation number (N_mu), such that in all cases N_mu ? 1. © 2019 Society of Chemical Industry     

Mechanical properties of blends of HDPE and recycled urea‐formaldehyde resin

The mechanical properties of blends of high‐density polyethylene (HDPE) with a recycled thermosetting filler, urea‐formaldehyde grit (UFG), were evaluated in the range of 0–23% of filler by volume. Ethylene‐acrylic acid (EAA) copolymers and an ionomer based on EAA were evaluated as compatibilizers. The observed tensile modulus of the ionomer‐treated blends was raised to three times the modulus of virgin polyethylene, whereas the modulus of the untreated blends reached double that of polyethylene. The ionomer‐treated blends also showed a higher tensile strength than the blends without filler treatment. The improvement in the properties was assigned to an increased interaction between the filler and the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3220–3227, 2000     

A novel gastric release PEG‐enclatherated polymethacrylate‐based memblet system

A novel polymethacrylate‐based membranous system referred to as a “memblet” was developed for potential application in controlled gastric drug delivery. A polymethacrylate‐based latex, Eudragit® E100, was enclatherated with a 60% w/v and a 30% w/v solution of polyethylene glycol 4000 to form hydrogel formulations A and B, respectively. The hydrogels were subsequently compressed into memblets that were characterized for thermal, rheological, morphological, mechano‐chemical properties, and in vitro gastric drug release analysis. Molecular mechanics (MM) simulations were performed to corroborate the experimental findings. Critical yield values of 15.39 and 5.239 Pa were obtained for hydrogel A and B, respectively. The viscoelastic region was found to be <10.67 and 2.542 Pa for hydrogels A and B, respectively. The storage modulus was greater than the loss modulus for hydrogel A while the inverse was true for hydrogel B. Thermal, mechanical, and surface morphology evaluation revealed that the converse was true for the dried membrane structure with hydrogel B having superior characterization profiles than hydrogel A. Notably, the lower PEG concentration (30% w/v) displayed better characterization profiles than a higher concentration (60% w/v). Through MM simulations, desirable agreement between the theoretical and experimental results was achieved over the given concentration range of PEG. Based on the gastric drug release analysis, memblets formulated with hydrogel B displayed superior control of drug release. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

The degradation kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate), a member of the Nodax family of polymers, were investigated using transient constant shear rate and dynamic time sweep rheological tests. The rate of chain scission at several times and temperatures was correlated with viscosity data and verified using molecular weight determination of the degraded samples. The experimental results show that the molecular weight and the viscosity of Nodax decrease with time over the range of temperatures that were studied (155–175°C). The degradation kinetics, which exhibited first‐order behavior, were determined as a function of the flow history and thermal history. An apparent activation energy of 189 ± 5 kJ/mol for thermal degradation was found by modeling variations in the rate with temperature using an Arrhenius law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 66–74, 2005     

Synthesis and thermal properties of combined liquid crystalline epoxy resins

Liquid crystalline epoxy resins were prepared by the curing reaction of epoxy and amine compounds with a mesogenic group in the mesomorphic temperature range. Some epoxy resins exhibited a typical liquid crystalline phase. Curing reaction of a mesogenic epoxy compound with an aliphatic amine compound containing cyano biphenyl group was faster than that of another epoxy resins confirmed by thermally controlled Fourier transform infrared measurements. The glass transition temperature of the liquid crystalline epoxy resin containing cyano biphenyl group increased with increasing curing reaction time. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1979–1990, 1998