Bio‐Based Rubbers by Concurrent Cationic and Ring‐Opening Metathesis Polymerization of a Modified Linseed Oil

Bio‐based rubbers prepared by tandem cationic polymerization and ROMP using a norbornenyl‐modified linseed oil, Dilulin?, and a norbornene diester, NBDC, have been prepared and characterized. Increasing the concentration of the NBDC in the mixture results in a decrease in the glass transition temperature. The new bio‐based rubbers exhibit tensile test behavior ranging from relatively brittle (18% elongation) to moderately flexible (52% elongation) and with decreasing values of tensile stress with increasing NBDC content. Thermogravimetric analysis reveals that the bio‐based rubbers have maximum decomposition temperatures of over 450 °C with their thermal stability decreasing with increasing loadings of NBDC.

     

Syndiotactic Polystyrene/Organoclay Nanocomposites: Synthesis via In Situ Coordination‐Insertion Polymerization and Preliminary Characterization

Summary: Syndiotactic polystyrene (sPS)/organophilic clay nanocomposites were obtained by in situ coordination‐insertion polymerization of styrene. Two cationic surfactants (alkylammonium and alkylphosphonium) were used for the intercalation of montmorillonite (MMT). For each organically modified clay, three protocols were performed using an MAO‐activated hemi‐metallocene catalyst, in order to compare the influence of experimental conditions on the composite microstructure and on its thermal stability. The microstructures of nanocomposites were investigated by wide angle X‐ray scattering and DSC. Partially exfoliated or intercalated materials were obtained in all cases and a decrease of crystallinity is observed. Thermal properties were also studied by DSC and thermogravimetric analysis. The presence of clay does not have a strong influence on the sPS thermal transitions but the thermal decomposition process of the material was slowed down in the presence of few organoclay percents, particularly in the degradation beginning. The influence of these two organically modified clays on the thermal stability of the material is discussed.

Gel and suspension formed from the combination of cloisite with toluene (left) and styrene (right), respectively.     

Cationic Ring Opening Polymerization of Glycolide Catalysed by a Montmorillonite Clay Catalyst

The ring opening bulk polymerization of glycolide catalyzed by Maghnite-H⁺ was reported. Maghnite-H⁺ is a montmorillonite sheet silicate clay, exchanged with protons. The effect of the amount of Maghnite-H⁺ and the temperature on polymerisation was studied. Increasing Maghnite-H⁺ proportion and temperature produced the increase in glycolide conversion. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. Mechanism studies showed that monomer inserted into the growing chains with the acyl–oxygen bond scission rather than the break of alkyl–oxygen bond.     

Poly(vinyl alcohol) and Polyamide‐66 Nanocomposites Prepared by Electrospinning

Summary: PVA and PA‐66 nanocomposite fibers with montmorillonite were prepared by electrospinning. Mixing of the components was conducted in two ways: polymer and montmorillonite were mixed with solvent, or monomer was polymerized in the presence of montmorillonite and was then dissolved in a solvent. Polymer/montmorillonite solutions were then electrospun on a non‐woven substrate. To the unaided eye, the coated area was either continuous coating or well‐defined spots. Characterization of the fiber structure and the particle size and distribution by SEM and elemental analysis showed the nanosized filler to be dispersed through the fiber network of the polymer/nanocomposite regardless of the preparation method. However, the clay particles within the fibers were smaller with the polymerization method than mixing in solvent. Only the PA‐66‐based nanocomposites exhibited large enough coating area on the substrate for measurements of contact angles and the time required for water penetration. Contact angles and the time required for water penetration were increased for most of the PA/nanoclay composites relative to the uncoated substrate.

SEM image of a typical fiber structure of a PVA/nanocomposite obtained by electrospinning under alkaline conditions.     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

Corn oil‐based composites reinforced with continuous glass fibers: Fabrication and properties

Novel thermosetting composites have been successfully developed using glass fibers to reinforce regular corn oil (COR) and conjugated corn oil (CCOR) resins prepared by cationic copolymerization with styrene (ST) and divinylbenzene (DVB). The dependence of morphology and physical properties of the composites on the contents of glass fibers and DVB was determined by scanning electron microscopy, dynamic mechanical analysis, thermogravimetric analysis and tensile testing. The glass fiber loading and polymer matrix composition play an important role in improving the mechanical properties and thermal stability of the resulting composites. As the glass fiber content increases from 0 to 45 wt %, the COR‐based composites show an increase in Young's modulus from 4.1 to 874 MPa and tensile strength from 1.7 to 8.4 MPa. Furthermore, the composites exhibit good damping properties and are suitable for applications where reduction of both unwanted noise and vibration is important. Compared with the composites from COR, the CCOR‐based composites exhibit slightly higher thermal stabilities and mechanical properties, due to higher reactivity of CCOR with comonomers. Increasing the DVB content improves the crosslink density of the polymer matrix, leading to a significant improvement in the thermal stabilities and mechanical properties of the resulting composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3345–3353, 2006     

聚丙烯/蒙脱土纳米复合材料的结构及物理性能研究

采用化学反应法制备了Ziegler-Natta/有机改性蒙脱土复合催化剂,并通过丙烯单体原位插层聚合法制备出聚丙烯/蒙脱土(PP/MMT)纳米复合材料,研究了复合材料的微观结构、热性能以及加工稳定性等。结果表明,原位聚合法制备的复合材料为剥离型纳米复合材料,其中MMT片层以纳米尺寸均匀分散在PP基体中,MMT平均厚度小于10nm;随MMT含量的提高,复合材料的热稳定性提高;原位聚合制备的PP/MMT纳米复合材料在长时间剪切过程中部分MMT会发生自聚集,控制剪切时间可以有效防止MMT的自聚集;原位聚合制备的PP/MMT复合材料(粉料)中,PP以α晶型为主,纳米MMT的引入并不会诱导生成聚丙烯β晶型,复合材料中β晶型的出现与退火条件有关。     

Polymerization Kinetics and Characterization of Dual Cured Polyurethane‐Acrylate Nanocomposites for Laminates

Summary: Four different types of montmorillonites have been dispersed by sonication at 50 °C into a propoxylated aromatic epoxy diacrylate oligomer to achieve interlayered or exfoliated nanocomposites. A thermally‐induced crosslinking reaction, forming a polyurethane network in the presence of 7 wt.‐% of a montmorillonite, has been promoted by addition of an allophanate modified polyisocyanurate based on hexamethylene diisocyanate. The kinetic behavior of the network formation has been studied at 25, 40 and 60 °C by following the disappearance of the isocyanate vibrational band found at 2 270 cm^?1. A tight crosslinked polyurethane acrylate network has been achieved by a subsequent dual UV curing promoted by a photoinitiator mixture (0.6 wt.‐%) added to the reactive mixture because of further reactions occur to the acrylate double bonds. The photopolymerization kinetic has been investigated on the different thermally treated polyurethane nanocomposite networks by Real Time FTIR spectroscopy monitoring the changes of the IR band at 810 cm^?1 assigned to the acrylate double bond vibrations. The influence of the different montmorillonite clays on the final nanocomposite morphology has been investigated by using XRD and SEM. Finally, the use of these mixtures as internal layer between two modified surface PET films has been also studied for the laminate production. The based‐PET laminate films have been characterized by determining the bending resistance and optical properties as a function of different nanofillers.

Bending resistance of the dual cured nanocomposite laminates containing 7 wt.‐% as a function of nanofiller types.     

Rubbery Thermosets by Ring‐Opening Metathesis Polymerization of a Functionalized Castor Oil and Cyclooctene

Rubbery thermosets prepared by ROMP of a modified castor oil containing norbornene moieties and cyclooctene have been synthesized and characterized. The thermosets range from 55 to 85 wt.‐% oil and are flexible, slightly transparent and have a sand‐like hue. Increasing concentration of the modified castor oil in the feed ratio results in an increase in the extracted (unreacted or oligomeric) components in the final thermoset. Thermogravimetric analysis reveals that all of the specimens have temperatures of maximum degradation around 500 °C. DMA and TGA analysis on solvent‐extracted specimens show that the presence of the soluble fractions helps to plasticize the materials and give added thermal stability.

     

原位聚合制备PET/ATO纳米复合材料及其结晶行为

将锑掺杂二氧化锡(ATO)纳米颗粒均匀分散于乙二醇(EG)介质中,通过EG与对苯二甲酸(TPA)原位聚合制备了聚对苯二甲酸乙二酯(PET)/ATO纳米复合材料.利用SEM、DSC、XRD、FTIR和TGA等方法,研究了ATO在PET基体中的分散性、PET/ATO复合材料的结晶行为和热性能.利用原位聚合制备的PET/ATO复合材料,ATO颗粒在PET基体中分散均匀,尺寸100～150 nm,纳米ATO颗粒的加入导致PET的特性粘数增大.在PET基体中,纳米ATO颗粒起到异相成核的作用,提高了PET的结晶速率和结晶度,减小了PET的晶粒尺寸,同时也使PET热稳定性提高.随着ATO含量增加,熔融纺丝得到的PET纤维的电阻下降.加入1%ATO的PET纤维的体积电阻率为4.9×109 Ω·cm,具有很好的抗静电效果.     

Polysulfone/Clay Nanocomposites by in situ Photoinduced Crosslinking Polymerization

PSU/MMT nanocomposites are prepared by dispersing MMT nanolayers in a PSU matrix via in situ photoinduced crosslinking polymerization. Intercalated methacrylate‐functionalized MMT and polysulfone dimethacrylate macromonomer are synthesized independently by esterification. In situ photoinduced crosslinking of the intercalated monomer and the PSU macromonomer in the silicate layers leads to nanocomposites that are formed by individually dispersing inorganic silica nanolayers in the polymer matrix. The morphology of the nanocomposites is investigated by XRD and TEM, which suggests the random dispersion of silicate layers in the PSU matrix. TGA results confirm that the thermal stability and char yield of PSU/MMT nanocomposites increases with the increase of clay loading.

     

Preparation of Polystyrene/Clay Nanocomposites by Free‐Radical Polymerization in Dispersion

Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na‐MMT clay was pre‐modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading.

     

Organoclay Nanocomposites from Ethylene–Acrylic Acid Copolymers

Summary: A study of the structure–property relationships for nanocomposites prepared by melt compounding from ethylene–acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2–50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations.

TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A.     

Production of Thermoplastic Starch/MMT‐Sorbitol Nanocomposites by Dual‐Melt Extrusion Processing

A “green” processing method, dual‐melt extrusion, was used to prepare thermoplastic starch/montmorillonite nanocomposites without organic reactions in the solution. XRD demonstrates that sorbitol enlarged the interlayer distance of MMT during the first step. MMT‐sorbitol, formamide and starch were used to obtain TPS/MMT nanocomposites in the second step. XRD and TEM reveal that TPS intercalated the layers of MMT. With increasing MMT content, improvements in thermal stability, tensile strength, Young's modulus and energy break, and a slight decrease of elongation at break, appeared. The effect of water content on the tensile strength and elongation at break was also studied.

     

High-Performance and Biobased Polyamide/Functionalized Graphene Oxide Nanocomposites through In Situ Polymerization for Engineering Applications

In this study, biobased polyamide/functionalized graphene oxide (PA-FGO) nanocomposite is developed using sustainable resources. Renewable PA is synthesized via polycondensation of hexamethylenediamine (HMDA) and biobased tetradecanedioic acid. Furthermore, GO is functionalized with HMDA to improve its compatibility with biobased PA and in situ polymerization is employed to obtain homogeneous PA-FGO nanocomposites. Compatibility improvement provides simultaneous increases in the tensile strength, storage modulus, and conductivity of PA by adding only 2 wt% FGO (PA-FGO2). The tensile strength and storage modulus of PA-FGO2 nanocomposite are enhanced dramatically by ≈50% and 30%, respectively, and the electrical conductivity reached 3.80 × 10^–3 S m⁻¹. In addition, rheology testing confirms a shear-thinning trend for all samples as well as a significant enhancement in the storage modulus upon increasing the FGO content due to a rigid network formation and strong polymer-filler interactions. All these improvements strongly support the excellent compatibility and enhanced interfacial interactions between organic–inorganic phases resulting from GO surface functionalization. It is expected that the biobased PA-FGO nanocomposites with remarkable thermomechanical properties developed here can be used to design high-performance structures for demanded engineering applications.     

乳液聚合法制备聚苯乙烯／蒙脱土插层复合材料

利用乳液聚合法制备了聚苯乙烯／蒙脱土插层复合材料,XRD,FTIR等表明,聚苯乙烯已插层进入蒙脱土层间,TGA,DSC表明,复合材料的热稳定性提高了,其热分解温度和玻璃化转变温度的提高是由于聚苯乙烯插层进入蒙脱土层间,并和蒙脱土产生相互作用的结果,初步提出了乳液聚合插层机理。     

Epoxy‐Based Azopolymers with Enhanced Photoresponsive Properties Obtained by Cationic Homopolymerization

Azopolymers are highly versatile materials due to their unique photoresponsive properties. In this contribution, a novel azo‐modified epoxy network is synthesized by cationic homopolymerization with boron trifluoride monoethylamine (BF₃.MEA) complex as initiator. The effect of the addition of a fixed content of amino‐functionalized azo chromophore, Disperse Orange 3, into the polymer matrix is studied in detail. First of all, the thermal curing cycle is optimized by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) measurements. Then, the resulting bulk azo‐modified epoxy networks are characterized by means of thermogravimetric analysis (TGA), FTIR, DSC, UV–vis spectroscopy, and rheological measurements. Finally, the optical response of thin films of these materials is determined. The results evidence that azo‐modified epoxy networks obtained by cationic polymerization with optimized curing cycle display high T _g values, high maximum photoinduced birefringence, fast writing speed, and exceptionally high remnant anisotropy. Therefore, this material is a promising candidate to be used for optical storage applications.     

Photoinitiated Cationic Polymerization of p-methylstyrene by Methoxy Trityl Salts

Photoinitiated cationic polymerization of p-methylstyrene has been investigated in dichloromethane at 25°C, using stable, soluble, and nonhygroscopic di, tri and pentamethoxy trityl carbocationic salts, having non-nucleophilic anions such as SbF₆ ^?, AsF₆ ^?, PF₆ ^?. The reactivity of these salts falls in the order: trimethoxy > dimethoxy > pentamethoxy. The effects of counter ion structure, salt concentration, photolysis time and photolysis wavelength on the polymerization rate are presented.