Fluorinated Hyperbranched Polymers as Additives in Cationic Photopolymerization

Summary: Different fluorinated hyperbranched polymers (HBP) were synthesized starting from fluorinated oxetanes and employed as additives in cationic photopolymerization of epoxy monomers. As previously observed for other hydroxyl containing HBP, they interact with the polymeric carbocation through a chain transfer mechanism inducing an increase in the final epoxy conversion. High gel content values (>96%) for the photocured films confirm that the HBP additive is tightly crosslinked to the polymeric network. In the presence of this fluorine‐containing HBP it is possible to influence the bulk properties, as well as, the surface properties. The fluorinated HBP tends to migrate to the surface inducing an increase of hydrophobicity.

The hyperbranched polymer used in this work.     

Phenolic Hyperbranched Polymers as Additives in Cationic Photopolymerization of Epoxy Systems

Summary: A phenolic group containing hyperbranched polyester (HBP) was synthesized and employed as chain transfer agent in cationic photopolymerization of a biscycloaliphatic epoxy monomer ( CE ). The epoxy group conversion increases by increasing the amount of HBP in the photocurable resin, due to a chain transfer reaction involving the phenolic‐OH groups. HBP acts as a plasticizer inducing decrease of the T_g values together with an increase of the toughness properties. Meanwhile gel content increases together with the E′ values. By increasing the amount of HBP in the photocurable resin an increase of the density is evident indicating a decrease of free volume. Therefore an improvement of the gas barrier properties might be expected; at the same time an increase of the thermal stability is evident.

     

Synthesis of Fluorinated Hyperbranched Polymers and Their Use as Additives in Cationic Photopolymerization

Summary: A fluorine containing hyperbranched polymer was synthesized by modifying an aromatic‐aliphatic hyperbranched polyester with a semifluorinated alcohol via a Mitsunobu reaction and was subsequently used as an additive in cationic photopolymerization of an epoxy resin. The remaining OH groups of the fluorinated hyperbranched polymer interact with the polymeric carbocation through a chain‐transfer mechanism inducing an increase in the final epoxy conversion. The fluorinated HBP induces modification of bulk and surface properties, with an increase in T_g and surface hydrophobicity already reached at very low concentration. The HBFP additive can, therefore, protect the coatings from aggressive solvents, increases hardness, and allows the preparation of a low energy surface coating.

Synthesis of fluorinated hyperbranched polyester.     

Cationic photopolymerization of oxetane‐functionalized hyperbranched polymers

An aliphatic–aromatic pehenolic hyperbranched starting material (HBP‐OH) with phenolic end groups was 85% functionalized by a Mitsunobu reaction with oxetane groups (OXT‐HBP). This new hyperbranched polyester was used, at a concentration of 5–20 wt %, as an additive for the cationic photopolymerization of a commercial oxetane‐based resin, 4,4′‐bis[(3‐ethyl‐3‐ethyl‐3‐oxetanyl) methoxymethyl]biphenyl (OXBP). HBP‐OXT acted as a multifunctional crosslinker, copolymerizing with the oxetane ring of the OXBP resin, reacting through chain transfer with the remaining phenolic OH groups, or doing both. The result was an increase in the glass‐transition temperature due to the increase in the crosslinking density. An increase in the weight residue at a high temperature was found in the presence of HBP‐OXT and was attributed to the presence of phenolic groups, which are commonly used as antioxidant additives. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 293–299, 2005     

超支化聚酯在环氧树脂改性中的研究进展

综述了超支化聚酯(HBPE)在环氧树脂改性中的研究进展,首先对端羟基/端羧基/端环氧/端氨基HBPE的制备方法进行了总结;随后对不同端基的HBPE在环氧树脂的增韧改性及其增韧机理的研究进展进行了介绍;然后介绍了不同端基的HBPE对环氧树脂固化性能的影响研究.最后分析了HBPE在环氧树脂改性领域中需要关注的问题,指出未来...     

超支化环氧树脂的合成及应用研究进展

从超支化环氧树脂独特的结构特点出发，详细介绍了超支化环氧树脂的分类、合成方法及合成路线，列举了超支化环氧树脂合成的最新思路和进展；介绍了超支环环氧树脂在环氧树脂增韧、复合材料中的应用，阐述了增韧机理并列举了应用实例；最后总结了超支化环氧树脂合成和应用的发展方向，力求为广大科研工作者提供帮助和借鉴。     

Use of Hydroxyl Functionalized (Meth)acrylic Cross‐Linked Polymer Microparticles as Chain Transfer Agent in Cationic Photopolymerization of Cycloaliphatic Epoxy Monomer, 2

This study is related to the use of hydroxyl functional acrylic cross‐linked polymer microparticles (CPM, also named microgels) as a chain transfer agent in cationic photopolymerization of cycloaliphatic epoxy monomer. All CPM were based on butyl acrylate and were consequently rubbery at ambient temperature. The effect of the stabilizing acrylate monomer used during the CPM synthesis was evaluated with respect to the viscoelastic properties of the photopolymerized cationic‐type epoxy films. The viscoelastic properties were correlated to the photopolymerized film morphology observed by transmission electron microscopy. Two acrylate monomers used as stabilizing agents during CPM synthesis were compared: cardura acrylate (CA) and lauryl acrylate (LA). CA was a good stabilizer for CPM in epoxy monomer before photocure and the CPM were well dispersed into the network after reaction. In contrast, LA was a poor stabilizer resulting in large CPM aggregation. The blend of these two types of CPM led to intermediate morphology, probably because of the flocculation of the CPM stabilized with LA. Conversely, CPM synthesized with a blend of the two stabilizing acrylate monomers induced in epoxy matrix a specific bi‐continuous morphology and consequently unique viscoelastic properties.

TEM micrographs of a photopolymerized film with 15 wt.‐% CPM(BA + 20%HEA)‐20%CA + 15% CPM(BA + 18%HEA)‐27%LA used as chain transfer agents.     

超支化聚酯的合成及改性环氧树脂的研究

以季戊四醇为核,2,2-二羟甲基丙酸为增长单体,对苯甲磺酸为催化剂,合成了超支化聚酯,通过FI-IR图谱对超支化聚酯进行结构表征,证明得到端基为羟基的超支化聚酯。采用超支化聚酯做增韧剂,研究其对环氧/四氢苯酐固化体系的增韧作用,探讨了超支化聚酯的分子量(代数)、超支化聚酯的含量、固化温度等因素对环氧树脂固化体系力学韧性的影响。     

Investigation on the effect of the presence of hyperbranched polymers on thermal and mechanical properties of an epoxy UV‐cured system

The use of hydroxyl‐functionalized hyperbranched polymers (HBPs) (Boltorn^® H20, H30 and H40) was investigated with respect to a UV‐cured epoxy system. Their presence induced an increase of the final epoxy conversion, which was interpreted on the basis of a chain‐transfer reaction. A decrease of the T_g values in the photocured films was observed when the amount of HBP additive in the photocurable formulation was increased. When the amount of HBP in the photocurable resin was increased, the density of photocured films increased, indicating a decrease on the free volume. Moreover, a clear increase in toughness was observed and attributed to the plasticization effect induced by the presence of HBP. This effect is particularly interesting for epoxy thermosets, which are characterized by good mechanical properties, although they are brittle and fragile. By increasing the toughness properties of these photocured resins it may be possible to broad their applications. Copyright © 2005 Society of Chemical Industry     

Synthesis,Characterization, and Properties of Multifunctional Epoxy Maleimide Resins

Summary: Novel multifunctional formaldehyde resins bearing diaminodiphenylmethane groups are synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), o‐cresol (o‐Cz), and cyclohexanone (CH_x) with formaldehyde (FA) (at a molar ratio of monomers/formaldehyde, 1/1), in the presence of acid catalyst (HCl). The obtained resins are epoxidated with a large excess of epichlorohydrin and transformed into multifunctional epoxy resins. The multifunctional epoxy maleimide resins are obtained by reaction of the epoxy resins with carboxy phenyl maleimide in the presence of triethylamine as a catalyst. The resultant resins are characterized by IR and NMR spectroscopy, elemental, and thermal analysis. The curing and thermal behavior of these epoxy maleimide resin/DDM systems are investigated using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The activation energies of the curing reactions are situated in the range of 53–90 kJ · mol^?1. The cured products have good thermal properties, and activation energies of degradation reactions have values between 42–74 kJ · mol^?1.

The curing reaction of multifunctional epoxy maleimide resins with DDM.     

超支化聚酯在环氧树脂改性中的应用

超支化聚合物是一类具有三维树形结构的高度支化的大分子。由于其独特的结构和性能以及可实现工业化生产的潜力,超支化聚合物已经成为高分子材料领域研究的热点之一,并且得到了越来越多的关注。作为一类非常重要的超支化聚合物,超支化聚酯(HBPE)引起了研究人员的极大兴趣。目前,HBPE已经在众多领域获得应用,特别是在环氧树脂改性中的研究发展迅速。综述了HBPE作为改性剂在环氧树脂中的应用研究进展,同时对HBPE在环氧树脂和其他热固性树脂改性中的应用研究方向作了展望。     

The Effect of the Degree of Branching in Hyperbranched Polyesters Used as Reactive Modifiers in Epoxy Thermosets

The effect of the degree of branching (DB) of a hyperbranched polyester (GBPEX) added as a modifier of new thermosets obtained from diglycidylether of bisphenol A has been studied. The use of ytterbium triflate as cationic initiator allows the hydroxyl chain‐ends in the GBPEX to become covalently linked to the matrix through the monomer activated propagation mechanism. The curing process has been studied by DSC and rheology. The DB of the modifier does not affect appreciably the thermal stability and the chemical reworkability but shrinkage exhibits a significant reduction on increasing the DB. Thermomechanical characteristics are also improved with increasing the DB of the modifier.

     

Cationic photopolymerization of 3‐benzyloxymethyl‐3‐ethyl‐oxetane

The cationic photopolymerization of 3‐benzyloxymethyl‐3‐ethyl‐oxetane (MOX104) initiated by triphenylsulfonium hexafluoroantimonate under UV light was conducted. The kinetics were investigated by real‐time Fourier transform IR spectroscopy and the mechanical and thermal properties of poly(MOX104) were examined by dynamic mechanical analysis and TGA. To adjust the properties of the polymer, different initiator concentrations and comonomer composition were applied. The results showed that the conversion of MOX104 was improved significantly from 17% to almost 90% by adding a certain amount of 3,4‐epoxycyclohexane carboxylate or diglycidyl ether of bisphenol A epoxy resin, while not much effect was observed by adding 1,4‐butanediol diglycidyl ether. Moreover, the glass transition temperature, decomposition temperature and Young's modulus of poly(MOX104) were improved by adding different amounts of diglycidyl ether of bisphenol A epoxy resin. © 2016 Society of Chemical Industry     

Synthesis and Characterization of Novel Azido Polymers: Hyperbranched Poly‐3‐azidomethyl‐3‐hydroxymethyl Oxetane

In the past thirty years, azido polymers have attracted wide attention in the field of energetic materials. Currently, the synthesized azido polymers have linear structure. In the present research, hyperbranched poly‐3‐azidomethyl‐3‐ hydroxymethyl oxetane (HBPAMHMO) was synthesized using an AB₂ monomer, and its physical and chemical properties were studied. The results showed that the molecular weight of HBPAMHMO increased along with the increasing ratio of r ([monomer]₀/[initiator]₀), together with very narrow PDI (from 1.12 to 1.34), and moreover, the degree of branching increased along with the increase in polymerization temperature. As compared to linear azido polymer with similar structure, it has lower glass transition temperature, sensitivity, higher combustion heat and mechanical properties, suggesting a great prospect for numerous applications.     

阳离子型超支化聚丙烯酰胺的合成与反应中影响产物黏度因素的探讨

以季戊四醇为支化剂,按一定的比例加入丙烯酰胺(AM)并加入阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)增加其阳离子性,合成了具有阳离子性的超支化聚丙烯酰胺。对产物进行了红外光谱(FTIR)分析,并使用旋转粘度计和一定计算测得了聚合物的增比黏度。而后探讨了反应温度、反应时间和引发剂用量对产物粘度的影响。     

Improved thermosets obtained from diglycidyl ether of bisphenol A/4,4′‐diaminodiphenylsulfone based on a new epoxy‐terminated hyperbranched polymer

A new hyperbranched polymer (HBP) with a flexible aromatic skeleton and terminal epoxy groups was synthesized to improve the toughness of diglycidyl ether of bisphenol A. The HBP was characterized using nuclear magnetic resonance, Fourier transfer infrared spectroscopy and gel permeation chromatography. The effect of HBP on the thermomechanical and mechanical properties of modified epoxy systems was studied. For evaluating the efficiency of the modified epoxy systems, composite samples using glass fiber cloth were molded and tested. Using dynamic mechanical analysis, a slight reduction in glass transition temperature (T_g) with increasing HBP content was observed. Analysis of fracture surfaces revealed a possible effect of HBP as a toughener and showed no phase separation in the modified resin systems. The results showed that the addition of 15 phr HBP maximized the toughness of the modified resin systems with 215 and 40% increases in impact and flexural strengths, respectively. T_g and heat resistance of cured modified resin systems decreased slightly with an increase in HBP content and, at 15 phr HBP, only a 2.6% decrease in thermomechanical properties was observed. Meanwhile, a molded composite with HBP showed improved mechanical properties and retention rate at 150 °C as compared to that made with neat resin. © 2015 Society of Chemical Industry     

Use of Single‐Walled Carbon Nanotubes as Reinforcing Fillers in UV‐Curable Epoxy Systems

CNT were dispersed in an epoxy matrix and cured by means of UV light. An increase on elastic modulus and T_g values was measured by DMTA analysis and attributed to the constraint effect of CNT on polymer chain mobility. Excellent scratch resistant coatings characterized by high critical load, small cracks and high recovery were obtained in the presence of a very low CNT content (0.025 wt.‐%). TEM analysis showed some isolated CNT and some cluster agglomerations of size of about 250 nm. It was shown that it was possible to decrease the surface resistivity of the cured samples by three orders of magnitude in the presence of 0.1 wt.‐% of SWCNT content.

     

脂环族环氧树脂及其在阳离子UV固化中的应用

脂环族环氧树脂除具有传统环氧树脂的特性外,其粘度低、工艺操作性好,耐热性高,固化收缩小,电性能好,耐紫外线及耐候性好等独有特点,使得其在紫外光固化涂料和油墨、电力绝缘材料、复合材料、胶黏剂、电子灌封等各个行业的应用需求逐年增加,是一种应用前景很好的树脂。