Synthesis and thermal polymerization of new polyimides with pendant phthalonitrile units

New polyimides with pendant phthalonitrile units were synthesized via the conventional two-step polymerization approach. The chemical structure of the PIs was confirmed by IR and ¹H NMR spectra. The thermogravimetric analysis and differential scanning calorimetry revealed that the thermal properties of the new PIs along with their solvent-resistance can be promoted after thermal treatment at 300 °C. This promotion can be attributed to the nitrile cure reaction of the phthalonitrile units indicated by the decrease in nitrile absorptions at around 2231 cm⁻¹ of the IR spectra.     

Improving water solubility of poly(acrylic acid‐co‐styrene) copolymers by adding styrene sulfonic acid as a termonomer

Acrylic acid is often used to make water‐soluble polymers while styrene is often modified to add special functions to polymers. However, when styrene and acrylic acid are copolymerized, the resulting polymer is much less water soluble. To regain water solubility, the effect of styrene sulfonic acid on solubility of poly(acrylic acid‐co‐styrene) copolymers was investigated. Even though acrylic acid polymers are known for their water solubility, the presence of styrene units within acrylic acid copolymers reduces the solubility of the copolymer substantially at the natural pH of the solutions. By adding styrene sulfonic acid as a termonomer, polymers that are water soluble at the natural pH of the polymerization could be obtained. The solubility of the polymer after removal of the solvent and by redissolving at different concentrations and pH levels is also reported. Solubility increases at higher pH especially with low styrene concentration in the copolymer. It was found that incorporation of as little as 5 mol % of styrene into poly(acrylic acid) reduced the aqueous solubility to less than 0.5 g dL^?1 at pH 7. Upon adding 7 mol % styrene sulfonic acid as a termonomer, the water solubility increased to 5 g dL^?1 at pH 7. At higher levels of styrene, more styrene sulfonic acid was needed, especially at low pH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

一种新的丙烯酸高级酯制备方法

用熔融酯化方法制备了丙烯酸高级酯 ,研究了单体量比、催化剂、阻聚剂、反应时间、反应温度等因素对该酯化反应的影响。确定用该法制备丙烯酸高级酯的适宜工艺为 :n(丙烯酸 )∶n(十八醇 ) =1 2∶1 0 ,m(对甲苯磺酸 )∶m(总单体 ) =1 0∶10 0 0 ,m(对苯二酚 )∶m(总单体 ) =0 5∶10 0 0 ,采用分段升温方法 ,于 110～ 140℃回流条件下反应 6h ,高级酯相对单体总质量的收率可达 90 %以上。测定了丙烯酸高级酯的熔点、沸点和元素组成 ,用红外光谱和核磁共振谱表征并证实其结构特征与用常规溶剂酯化法制备的产物并无明显差异     

Reactive Alder‐ene blend of diallyl bisphenol A novolac and bisphenol A bismaleimide: synthesis,cure and adhesion studies

A novel, addition‐curable novolac resin (ABPF) was synthesized by the reaction of diallyl bisphenol A with formaldehyde using p‐toluene sulfonic acid as the catalyst. The synthesis conditions were optimized to obtain soluble polymer of desirable molecular weight distribution which was characterized by FT‐IR, NMR and SEC. ABPF was reactively blended with bisphenol A bismaleimide (BMIP) and cured through an Alder‐ene reaction at high temperatures. The cure characteristics of BMIP–ABPF blend with a maleimide:allyl phenol stoichiometry of 1:1 were studied using FT‐IR, DSC and DMA, which evidenced the multi‐step cure reactions taking place in the system. Cure optimization was evaluated by DSC, DMA and adhesive property tests. The moderately crosslinked blend was conducive for achieving the optimum adhesive properties on aluminium substrates. Retention of the adhesive properties was greater than 100% at 150 °C. © 2001 Society of Chemical Industry     

Solid state carbon-13 NMR studies of silica-filled TBBS-accelerated, sulfur vulcanized, cis-1,4 polyisoprene

The network formation of silica-filled, TBBS accelerated sulfur vulcanization of cis-1,4 polyisoprene (Natsyn 2200) was studied by solid state ¹³C NMR spectroscopy, and equilibrium swelling measurements. Samples with varying silica levels at different stages of cure were analyzed. It was observed that silica retards the cure reaction, and results in an overall lower cure state. Silica also has an influence on the vulcanization chemistry causing an enhancement of the cis-trans isomerization, chain scission, and the formation of monosulfidic linkages. It was also determined that the polysulfidic linkages decreased as silica level was increased. Intermolecular crosslinks decreased, while intramolecular structures (including pendant side groups and cyclic sulfur structures) increased. Cross link density, as determined by swelling measurements, decreased as the silica level was increased. Received: 1 October 1997/Revised version: 1 December 1997/Accepted: 2 December 1997     

Degree of cure of epoxy/acrylic photopolymers: Characterization with raman spectroscopy and a modified phenomenological model

This study characterizes the degree of cure c, of a two‐part epoxy/acrylic photopolymer used in stereolithography, SLA. The use of solid free form fabrication has added a whole new list of thermosets with a chemical reaction—curing reaction—targeted for these specific manufacturing processes. The studied thermosetting system exhibits a fast curing reaction triggered by a UV‐light source. An innovative stepwise method to quantify the degree of cure using Raman spectroscopy is reported. This method abates the Raman noise and compensates for the weak signal of fast measurements. The Raman data processing algorithm BEADS was implemented. The technique presented here was capable of following the degree of cure of the individual components of the photopolymer. Based on the epoxy/acrylic monomers concentration (75%/25%), the degree of cure for the whole system was quantified. The experimental results were modeled using a modified phenomenological kinetics equation. This model includes the dependency of the rate of cure on the light intensity, and cure state. Based on the analysis reported here, the proposed model accurately fits the initiation, propagation, and termination phases of the cure cycle. The technique and methods presented here can potentially be integrated to in situ process monitoring with instant parameter feedback, and numerical modeling of residual stresses in additive manufacturing of thermosets. POLYM. ENG. SCI., 58:228–237, 2018. © 2017 Society of Plastics Engineers     

Grafting of acrylic acid onto corona-treated polyethylene surfaces

Peroxides formed on the surface by corona treatment of low-density polyethylene film can be used to initiate grafting of polar vinyl monomers such as acrylic acid. Different types of peroxides are probably formed on the surface, but at least hydroperoxides could be detected by XPS analysis. The grafting reaction was carried out directly after corona treatment, by placing the corona-treated film above a solution of acrylic acid heated to 100°C. The grafting reaction takes place in a vapor phase of the monomer. After extracting the reacted films with hot methanol and drying, surface analysis by XPS, IR, and contact angle measurements were carried out. Effect of degree of corona treatment and reaction time have been studied. The conclusion from this work is that acrylic acid in vapor phase can successfully be grafted onto corona-treated polyethylene film by this method. © 1992 John Wiley & Sons, Inc.     

Sulfated zirconia and iron- and manganese-promoted sulfated zirconia: do they protonate alkanes?

Because of their high activities for alkane conversion, sulfated zirconia and iron- and manganese-promoted sulfated zirconia have been the objects of much recent attention as a possible next generation of solid acid catalysts for alkane conversion. These catalysts have been suggested to be superacidic on the basis of measurements with adsorbed Hammett indicator bases, but published data determined with other adsorbed bases indicate only moderately strong acid sites. The indicator methods are limited by the opaqueness of the materials and by the inability of the methods to probe a possible set of minority sites that might be responsible for the reactivity and catalytic activity for alkane conversions. Another approach to the challenge of estimating the acid strengths of the reactive and catalytic sites is to investigate the reactivities and catalytic activities of the materials for reactions which, for initiation, require donation of protons from a solid acid to a very weakly basic reactant such as an alkane. Such a test reaction is the acid-catalyzed dehydrogenation of alkanes proceeding by the Haag–Dessau mechanism (Olah type chemistry). This review includes a summary of results for conversion of ethane, propane, and n-butane that are consistent with the postulate that iron- and manganese-promoted sulfated zirconia and sulfated zirconia are capable of protonating light alkanes to give carbonium-ion transition states at temperatures as low as 200°C. The data support the postulate that these proton-donation reactions are important at low alkane conversions and in initiating alkane conversions, although conventional carbenium ion reactions predominate at high conversions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Curing of acrylated epoxy resin based on bisphenol-S

The acrylated diglycidyl ether of bisphenol-S was prepared by reacting diglycidyl ether of bisphenol-S (DGEBS) with acrylic acid using dimethyl benzylamine as a catalyst. The acrylated epoxy resin thus obtained was characterized by IR, ¹³C-NMR, and DSC. The curing reaction of the acrylated epoxy resin with dicumyl peroxide was investigated by differential scanning calorimetry at three different heating rates. The overall curing kinetics were found to be approximately second order, independent of the scan rate. The TGA was used to investigate the thermal decomposition of acrylated epoxy resin and to determine the kinetic parameters such as activation energy, preexponential factor, and reaction order. Such information can be used for quick estimation of polymer lifetimes.     

甲基丙烯酸聚乙二醇单酯的合成与表征

以聚乙二醇单甲醚-400与甲基丙烯酸直接酯化反应,以甲苯为带水剂、对甲苯磺酸为催化剂,合成甲丙烯酸聚乙二醇单酯。通过实验确定酯化反应的最佳条件：甲基丙烯酸与聚乙二醇单甲醚-400的摩尔比为2．5：1,反应温度115℃,阻聚剂对苯二酚为0．78％（以醇酸总质量计）,反应时间为9h,催化剂对甲苯磺酸为3％（以醇酸总质量计）,产率为87．5％。产品结构经IR和^1HNMR,^13CNM表征,证明为目标产物。     

高活性Br(o)nsted离子液体催化酯化反应

制备了两种基于4-二甲氨基吡啶(DMAP)的、对水和空气稳定的、带-SO3H官能团的Br(o)nsted酸离子液体,它们具有高的催化活性、很好的稳定性、可以循环使用、对环境友好,用于催化十三烷二酸与醇反应制备一系列二元酸酯,收率达到80%,二元酸酯选择性达到100%,且催化剂易与产物二元酸酯分离.     

Study of the Catalytic Activity–Semiconductive Properties Relationship For BaTiO<Subscript>3</Subscript> and PbTiO<Subscript>3</Subscript> Perovskites,Catalysts for Methane Combustion

Abstract  

The electrical conductivity of barium and lead perovskites used as catalysts for the total oxidation of methane, has been measured under nitrogen, methane–nitrogen mixture, air and methane–air mixture (reaction mixture) at the catalytic reaction temperature. The two compounds appeared to be p-type semiconductors under air with positive holes as the main charge carriers but became n-type when contacted with methane–nitrogen mixture. Their conductivities differ by 1.5 orders of magnitude as n-type semiconductors and by three orders of magnitude when being p-type semiconductors. These results explained the difference in the catalytic activity encountered on the two solids. The alkane activation was proposed to be related in both cases to the p-type semiconducting properties of the solids, likely through hydrogen abstraction by a surface O⁻ species, forming a CH₃^• radical. The overall reaction mechanism on both perovskites can be assimilated to a Mars and van Krevelen mechanism.     

Elastomers Formed In-Situ in Epoxy Resins: Chemistry and Toughening

The chemistry of the in-situ formation of elastomer particles in epoxy resins is described. Under normal synthetic conditions, if one polymerizes an acrylic monomer in an epoxy resin, the resulting polymer is soluble in the epoxy resin or it grossly phase separates, depending upon the solubility parameter difference between the acrylic polymer and the epoxy resin. This work shows that with the use of a specifically tailored material (which we believe operates as a “polymeric surfactant”) in the reaction mixture, a free-flowing, stable suspension of acrylic elastomer particles in epoxy resin can be obtained. Thus, the reaction product of isocyanatoethylmethacrylate and EPON^TM 1009 can be used as the polymeric surfactant in a reaction mixture containing hexyl acrylate, azo-bis(isobutyronitrile) and the diglycidyl ether of bisphenol A. The resulting dispersion is stable to settling even after exposure to 150°C. When properly formulated, the resulting modified epoxy resins are improved in their fracture resistance after cure over a similar resin without the elastomeric particles. The effect of the following parameters on the fracture resistance of the cured epoxy resin are discussed: chemistry of the polymeric surfactant, chain extension in the cure of the epoxy resin, type of acrylic monomer and the level of the elastomer. The physical properties of several adhesive formulations based upon these modified epoxy resins are also discussed.     

Cure study of an acrylic resin to develop natural fiber composites

In the present study a new environmentally friendly acrylic resin was characterized to develop a high‐performance biocomposite for future work. Differential scanning calorimetry measurements were used to determine onset of curing reaction as well as the degree of cure at a certain temperatures. Swelling equilibrium data for an acrylic resin were generally analyzed using the Flory–Rehner equation for a perfect network, to obtain a measurement of the molar mass between two crosslinks and the crosslink density of polymer, and to establish the effect of temperature and time on these parameters. The crosslink density of cured resin at 180°C and 10 min indicates the completion of a major part of the reaction under those conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 757–762, 2004     

Synthesis,characterization, and flocculation performance of anionic polyacrylamide P (AM‐AA‐AMPS)

In this study, a kind of anionic polyacrylamide (P(AM‐AA‐AMPS)) was synthesized using acrylamide (AM), acrylic acid (AA), and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) under ultraviolet (UV) irradiation. The conditions of the polymerization reaction such as monomer mass ratio, solution pH value, EDTA concentration and urea concentration were investigated by using the single factor approach and an L₁₆ (4⁵) orthogonal array. The structure and morphologies of the copolymer were determined by nuclear magnetic resonance spectrometer (NMR), infrared spectrometer (IR) and scanning electron microscope (SEM). The results show P(AM‐AA‐AMPS) with the intrinsic viscosity of 1.5 × 10³ mL g^?1 was synthesized at optimal conditions: mass ratio, m(AM) : m(AA) : m(AMPS) of 70 : 10 : 10, pH value of 9.0, EDTA concentration of 0.10% and urea concentration of 0.20%. In addition, P(AM‐AA‐AMPS) had better flocculation efficiency than commercial PAM in sludge dewatering experiment; the minimum filter cake moisture content could be reduced to 65.1%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Activation and Deactivation of Pt Containing Sulfated Zirconia and Sulfated Zirconia Studied byin SituIR Spectroscopy

In situinfrared spectroscopy (IR), thermogravimetric measurements (TG) and temperature-programmed evolution of gases (TPE) have been used to study activation and regeneration of sulfated zirconia with and without Pt (SZ, Pt/SZ). Isomerization and cracking ofn-heptane was used as test reaction. The first activation of Pt/SZ is independent of the atmosphere, air or He and N₂, in each case the catalyst was active. But it was necessary to regenerate the catalyst in air to obtain the initial activity and selectivity. When regeneration was done in helium or nitrogen the catalyst lost its acid properties and only hydrogenolysis ofn-heptane to propane andn-butane was observed. This can be explained by a loss of a part of sulfates between 400 and 500 °C measured by TG and TPE. In the IR spectrum the intensity of the SO band at 1400 cm^?1decreased and shifted to lower wavenumbers whereas the band of terminal Zr-OH groups at 3740 cm^?1, which was absent in the first spectrum after activation increased. The activation conditions of SZ are independent of the atmosphere, no loss of sulfate groups was observed. The reason for deactivation of SZ is coke formation during alkane conversion.     

Surface grafting polymerization of vinyl monomers on poly(tetrafluoroethylene) films by plasma treatment

Poly(tetrafluoroethylene) films were surface modified by argon plasma treatment followed by graft polymerization. Peroxidе groups were introduced on the surface of poly(tetrafluoroethylene) films after plasma treatment and the consequent contact with air when the films were taken out of the reactor. Grafting polymerization initiated by the surface peroxide (hydroxide) groups was performed on the poly(tetrafluoroethylene) film surface by using acrylic acid, 4-vinylpyridine and 1-vinylimidazole as monomers. Copolymers were obtained with grafting yield from 0.436 to 0.457 mg/cm² for poly(acrylic acid), from 0.299 to 0.390 mg/cm² for poly(4-vinylpyridine) and from 0.212 to 0.256 mg/cm² for poly(1-vinylimidazole), respectively. The free surface energies of the copolymers were determined. The chemical structures and the copolymer surfaces were characterized by IR, XPS and SEM analyses. High energy resolution X-ray photoelectron spectroscopy (XPS) confirmed the grafting of acrylic acid, 4-vinylpyridine and 1-vinylimidazole. The surface hydrophilicities of modified polytetrafluoroethylene films were significantly enhanced after plasma treatment and grafting modification. It is worth emphasizing that in this work acrylic acid, 4-vinylpyridine and 1-vinylimidazole were used as the reactive monomers for grafting on the poly(tetrafluoroethylene) film by plasma treatment. We believe that this vinyl monomers may be employable as functional groups, permitting a potentially wide range of applications: as ionomers, membranes, carriers for immobilization of biomolecules, for complex formation with heavy metals as catalysts.     

Kinetic study of phenolic resin cure by IR spectroscopy

The cure reaction of a commercial phenolic resin (FRD‐5002, Borden Chimie S.A.) has been studied by IR spectroscopy (Fourier transform IR). A phenomenological approach was used to characterize the kinetic of reaction. Various kinetic models, including homogeneous reactions, diffusion‐controlled reactions, phase boundary movement, and nucleation and growth‐type kinetic, have been tested. Kinetic analyses using integral procedures on isothermal data indicate that the cure reaction data can be described above 140°C using the homogeneous first‐order reaction model. The activation energy has been found to be about 49.6 kJ mol⁻¹. At lower temperature, a diffusive mechanism was active, and the kinetic of reaction was well described by the Jander kinetic model. Because of the simple kinetic control active above 140°C, a mechanistic model for the resol cure at these temperatures has been also proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2703–2715, 1999     

A new,nonphosgene route to poly(bisphenol a carbonate) by melt‐phase interchange reactions of alkylene diphenyl dicarbonates with bisphenol A

This article describes a new, nonphosgene method for the synthesis of poly(bisphenol A carbonate) (PC). The method involves three steps: the reaction of an aliphatic diol with phenyl chloroformate to form an alkylene diphenyl dicarbonate, the reaction of the alkylene diphenyl dicarbonate with bisphenol A to produce an aromatic–aliphatic polycarbonate, and the thermal treatment of the polycarbonate at 180–210°C under a stream of nitrogen with Ti(OBu)₄ to give PC and a cyclic alkylene carbonate. The method furnished low to moderate molecular masses of PC upon the complete elimination of the aliphatic moieties. The approach may be considered a new method, based on polycarbonate thermochemical degradation, for the synthesis of cyclic aliphatic carbonates. The obtained polymers were characterized by intrinsic viscosity and IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The thermal treatment step was conducted in a glass reaction tube at 180–210°C under a stream of nitrogen, and the reaction was completed by heating to 250°C. In the thermal treatment step, semisolid effluents composed of cyclic alkylene carbonates were formed and subsequently eliminated from the reaction mixture. Heating to 250°C under nitrogen or under a dynamic vacuum furnished the pure aromatic PC residue. This intrachange reaction provides a flexible method for the synthesis of polycarbonates with alkylene diols containing two or three methylene groups, from which the pure PC homopolymer can be prepared. The potential of this approach was demonstrated by the successful synthesis of PC homopolymer from five different polycarbonates with a bisphenol A unit linked to 1,2‐propylene, 1,3‐propylene, 2‐methyl‐1,3‐propylene, 2,2‐dimethyl‐1,3‐propylene, and 1,3‐butylene as the alkane chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Anti-infrared/ultraviolet property of fullerene-containing polyacrylate film

Abstract

High-optical quality polyacrylate films containing a small load of C₆₀ were prepared by blending the soluble polyacrylate with the fullerene C₆₀ derivative poly-[2-(acrylamido)-2-methylpropane sulfonic acid] (PAMPS)-C₆₀. TEM was used to observe the morphological structure of the fullerene-containing polyacrylate solution. The anti-infrared/ultraviolet property was characterised by UV–VIS and FTIR in the wavelength range of 190–5000 nm. Experimental results demonstrated an improved anti-IR/UV property of polyacrylate as well as good diaphaneity. In the visible spectrum, its transmittance was greater than 80%. In the UV region, the transmittance decreased to 10% (<300 nm). Meanwhile, the transmittance was 55·7% in the near IR wave range (4000–14000 cm^?1) and 31% in the middle IR wave range (2000–4000 cm^?1), respectively. This new nanocomposite material has great potential to serve as an anti-IR/UV thin coating to implement heat insulation in many applications.