Magnesium hydroxide nanoparticles grafted by DOPO and its flame retardancy in ethylene-vinyl acetate copolymers

Magnesium hydroxide (MH) nanoparticles have been considered as an excellent nonhalogen flame-retardant. However, the drawbacks of easy aggregation and relatively low flame retardancy limit their applications in polymer materials. In this research, MH nanoparticles were successfully grafted by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) through the bridge of vinyl silane coupling agents (WD70). The grafted MH nanoparticles (MH-WD70-DOPO) were characterized by Fourier transform infrared spectra, ³¹P nuclear magnetic resonance spectra, thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy spectra. MH-WD70-DOPO nanoparticles were incorporated into ethylene-vinyl acetate copolymer (EVA) matrix by melt blending method. The results indicated that MH-WD70-DOPO nanoparticles were much homogenously dispersed in EVA matrix than unmodified MH particles. EVA/MH-WD70-DOPO nanocomposites with 51.32 wt% loading showed higher flame retardancy, better mechanical and processing properties compared with EVA/MH-WD70 sample. These findings could provide a novel method to enhance the flame-retardant efficiency of inorganic hydroxide flame retardants, while keeping good mechanical and processing properties of polymer materials.     

Polycarbonate blends with styrene/acrylonitrile copolymers

Lap shear adhesion between laminated sheets of polycarbonate and styrene/acrylonitrile copolymers exhibits a sharp maximum when the acrylonitrile content of the copolymers is in the range of 25–27% by weight. Observations of shifts in glass transitions of the two phases in melt-mixed polycarbonate/SAN blends suggest partial miscibility of one polymer in the other, and this solubility is at a maximum when the SAN copolymer has an acrylonitrile content in the same range causing maximum adhesion. Mechanical properties of injection-molded blends of polycarbonate with various SAN copolymers were also best when the acrylonitrile content was the same as that giving maximum adhesion. The partial miscibility behavior in blends as a function of acrylonitrile content of the copolymer is explained qualitatively in terms of a simple binary interaction model.     

Emulsion copolymers of alpha-methylstyrene and styrene

This article reports molecular weights and mechanical and processing properties of a series of styrene/alpha-methylstyrene copolymers produced by emulsion polymerization at various temperatures. Molecular weights were measured by solution viscosity, membrane osmometry, light scattering, and gel-permeation chromatography. Molecular weight development is controlled by chain transfer to monomer, but the molecular weight distributions are broader than would be expected for such reactions. This is attributed to polymer branching resulting from chain-transfer events. Molecular weight distributions of copolymers were multimodal. Thermal stability of the copolymers is somewhat lower than that of polystyrene, but addition of conventional antioxidants produces compositions with good stability in thermoplastic processing operations. Copolymers containing 25 wt. % of alpha-methylstyrene have usage temperatures about 12°C higher than that of polystyrene.     

Stabilization of Pd,Pt and Ru nanoparticles by optically active CO/styrene copolymers

Fully isotactic, chiral CO/styrene copolymers were used as stabilizers for palladium, platinum and ruthenium nanoparticles synthesis. The tuning of copolymer/metal ratio and metal concentration were found to be key parameters in order to adjust the size and the agglomeration tendency of the metallic nanoclusters. These new materials were fully characterized by elemental analysis, infrared, solid state ¹³C MAS NMR spectroscopies, and transmission electronic microscopy. Platinum and ruthenium nanoparticles were tested as catalysts in the ethyl pyruvate hydrogenation, giving high activities; in this preliminary work, no enantioselectivity induction was observed.     

Blends of polyurethane carboxylates with styrene vinylpyridinium copolymers

This is a continuation of an ongoing investigation of miscibility enhancement via ionic interactions in urethane-styrene blends. The present study deals with a polyurethane which contains in the hard segments pendant carboxylate groups neutralized by ammonium ions while the polystyrene contains pendant vinyl pyridinium methyl iodide groups. Miscibility of the styrene is seen with the hard segments of the urethane because of ion pair/ion pair interactions. Methanol extraction raises the T_g because it eliminates low molecular weight components, without removing the microions.     

Characterisation and application of polyurethane copolymers grafted with photoluminescent dyes

Photoluminescent dyes (aminofluorene, naphthalimide, naphtholbenzein, or phenosafranine) were grafted to polyurethane using an allophanate linkage. The photoluminescence properties and the shape recovery effects of polyurethane samples were investigated. The polyurethane was composed of 4,4′‐methylenebis(phenylisocyanate), poly(tetramethyleneglycol), and 1,4‐butanediol. The dyes were linked through an extra 4,4′‐methylenebis(phenylisocyanate) and the carbamate moiety of the polyurethane chains. Polyurethanes with various dye contents were characterised, and the shape recovery and photoluminescence properties were compared. In the case of the tensile mechanical properties, the highest maximum stress was 56 MPa, and the strain remained > 1500% for the entire series. The shape recovery improved as the test cycle was repeated, with up to 100% recovery being achieved, but shape retention decreased as the dye content increased. Finally, the photoluminescence of the polyurethanes was demonstrated by a luminescent light‐emission test, together with pH indication capability and the preparation of non‐woven fibre using the electrospinning method.     

The preparation of block copolymers of styrene and methacrylic acid

A new method of preparing block copolymers of styrene and methacrylic acid is described. It is based upon use of the anionically initiated “living chain” method to prepare block copolymers of styrene and methyl methacrylate, with subsequent hydrolysis of the methyl methacrylate block to methacrylic acid.     

Synthesis and photochromic property of nanoparticles with spiropyran moieties via one-step miniemulsion polymerization

Summary  Photochromic nanoparticles with spiropyran moieties were prepared by a facile one-step miniemulsion polymerization. The nanoparticle dispersion was obtained by mixing the monomers, spiropyran-containing molecules and hydrophobe, dispersing them into an aqueous solution with surfactant, subjecting the dispersion to ultrasonification and polymerizing the monomers by using a water soluble initiator. The shape and size of the nanoparticles was determined with the atomic force microscope (AFM) and dynamic light scattering (DLS), and the determined average diameter of the nanoparticles ranges from 30 nm to 60 nm. The absorption and fluorescence spectra for the nanoparticles dispersions reveal that the spiropyran molecules were successfully incorporated in the polymer nanoparticles. Moreover, the nanoparticle dispersions were found to exhibit enhanced photo-reversibility, photo-stability and relatively fast photo-responsive property compare to the same species in aqueous solution.     

Solution styrene butadiene copolymers with lithium alkyl initiators

This paper is a review of the alkyllithium system of the copolymerization of butadiene and styrene. The alkyllithium system offer a very versatile tool by which a wide variety of styrene butadiene copolymers can be made to fit a particular application. Included are discussions of block and non-block copolymers of styrene butadiene, copolymers with functional groups, and copolymers with varying microstructure. In addition, wear and tractuion on a series of styrene butadiene copolymers with varying content and microstructure are presented.     

用ES共聚物对PE—PS共混物增容的研究

准无规乙烯－苯乙烯共聚物是由一种限定几何结构的催化剂制备,对聚乙烯－聚苯乙烯共混物的增容是非常有效的。     

Characterization of plasma-polymerized allyl alcohol polymers and copolymers with styrene

Pulsed plasma was used to initiate chemical copolymerization of allyl alcohol and styrene. In this way the concentration of OH groups at the surface of the copolymer layer could be adjusted from 0 (styrene homopolymerization) to 31 OH groups/100 C atoms (allyl alcohol homopolymerization). The copolymerization kinetics correspond to those of a pure chemical (radical) copolymerization. Thus, the variation of OH group density is only possible in a small range of comonomers ratio, otherwise styrene homopolymerization dominates.     

Novel amphiphilic carbon black composite nanoparticles from TEMPO-terminated polymer and TEMPO-terminated block copolymer grafted carbon black

The purpose of this study was to modify the surface characteristics of CB so as to prevent the aggregation of CB to provide the dispersibilities in either H₂O or organic solvent. In this study, five kinds of hydrophilic TEMPO-terminated polymer, hydrophobic TEMPO-terminated polymer and amphiphilic TEMPO-terminated block copolymer were synthesized. The five kinds of TEMPO-terminated polymers were: (1) poly(4-acetoxystyrene) (PAS-T), (2) poly(4-hydroxystyrene) (PHS-T), (3) polystyrene (PS-T), (4) poly(4-acetoxystyrene)-block-polystyrene (PAS-b-PS-T), (5) poly(4-hydroxystyrene)-block-polystyrene (PHS-b-PS-T). These TEMPO-terminated polymers with desired molecular weights and specific structures were synthesized by using the method of living radical polymerization in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO). These TEMPO-terminated polymers and TEMPO-terminated block copolymers were grafted onto the surface of CB through a reaction of polymer radicals trapped by CB, so as to obtain the TEMPO-terminated polymer/CB and TEMPO-terminated block copolymer/CB composite nanoparticles. Various variables such as reaction time, reaction temperature, amount of TEMPO-terminated polymer, molecular weight of TEMPO-terminated polymer and amount of CB all of which influenced the grafting efficiency were investigated. Besides, the stability of the composite nanoparticles, which dispersed in H₂O or organic solvent, was investigated by laser light scattering. The amphiphilic composite nanoparticles, PHS-T/CB and PHS-b-PS-T/CB, which dispersed well in both H₂O and organic solvent, were synthesized successfully in this work.     

Synthesis of structured nanoparticles of styrene/butadiene block copolymers via RAFT seeded emulsion polymerization

The structured nanoparticles of styrene (St) and butadiene (Bd) block copolymers were prepared by RAFT seeded emulsion polymerization of butadiene. It was confirmed that the block copolymers of PSt-b-P(St-co-Bd) was formed with controlled molecular weight and rather low PDI at low composition of the P(St-co-Bd) segment. With more incorporation of butadiene, the branching reaction of polybutadiene became obvious, leading to higher PDI and positive deviation of M_n from the theoretical predication. At the gel point, the composition of the P(St-co-Bd) segment was estimated to be 0.72. After this, the gel fraction increased quickly. The morphology of structured nanoparticles could be largely tuned simply by the copolymer composition. With the composition of the P(St-co-Bd) segment increased from 0.37 to 0.92, the morphology within the structured particles changed from the polybutadiene domains-in-polystyrene matrix, perforated concentric-spherical layer, concentric-spherical multi-layers, bi-continuous, to broken layers of polystyrene in polybutadiene matrix. It was found that the morphology of the block copolymer within nanoparticles was dependent on d/L values, which was in excellent agreement with the theoretical prediction.     

The microstructure of butadiene and styrene copolymers synthesized with n-BuLi/THF/t-AmOK

A study of the microstructure of copolymers, synthesized by B–S anionic copolymerization, initiated with n-BuLi/THF/t-AmOK in cyclohexane at 50°C, has been performed. Moreover, the mean sequence length in the B–S copolymer chain has been determined. The result showed that the microstructure of copolymers were sharply influenced by various ratios of modifier (THF, t-AmOK) to initiator (n-BuLi). By selecting a proper ratio of K/Li and THF/Li, B–S copolymers with unique randomness, having composition almost indentical to the initial monomer ratio at different stages of conversion and very low vinyl content, have been obtained. The formation mechanism of the copolymer chain structure is discussed.     

Rheological characterization of styrene acrylonitrile copolymers

The relationship between copolymer composition, molecular weight distribution, and rheological properties of random styrene acrylonitrile copolymers synthesized by radical polymerization in bulk was investigated. From differential scanning calorimetry analysis, glass transition temperature was obtained and increases with the acrylonitrile content. The knowledge of the glass transition is a key factor to compare the different copolymers in an iso‐free volume condition for melt rheology. Owing to time temperature superposition, a large frequencies window ranging from the terminal zone until the glassy plateau can be obtained. Thus, the mechanical spectroscopy was used to estimate the rubbery plateau modulus and the Newtonian viscosity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1316–1321, 2000     

苯乙烯/马来酸酐接枝聚乙烯蜡的研究

用溶液法制备了马来酸酐和马来酸酐/苯乙烯双单体接枝的聚乙烯蜡,考察了反应时间、温度、引发荆、单体用量对产物接枝率的影响.结果表明二叔丁基过氧化物是一种优良的接枝反应引发剂,在ω(引发剂)=0.4%、ω(马来酸酐)=6.0%、ω(苯乙烯)=4.0%、反应温度143℃、反应时间2.5 h的条件下,聚乙烯蜡接枝率为3.4%.并对产品进行了红外光谱分析、热分析表征.     

Synthesis and characterization of copolymers of styrene andN-methylolacrylamide

Copolymers of styrene (ST) and N-methylolacrylamide (NMA) were synthesized by emulsion polymerization for different initial weight ratios of ST/NMA. Fast reaction rates and high conversions are achieved regardless of the ST/NMA ratio. NMA content in copolymers, as deduced by DSC, FTIR and Kjeldhal analysis, is higher as the initial ST/NMA ratio decreases. Glass transition temperature of copolymers increases as the ST/NMA ratio decreases and it decreases with reaction time for a fixed ST/NMA ratio. The latter results and FTIR spectra as well as Kjeldhal analysis as a function of reaction time indicate that NMA reacts initially in the aqueous phase, after which ST, because of its overall larger concentration, is incorporated preferentially in the polymer.     

Spectrophotometric determination of the styrene content of alpha-methylstyrene — styrene copolymers

Summary The electronic absorption spectra of polystyrene and poly (alpha-methylstyrene) show a great difference in the extinction coefficient values at 226nm. On basis of this fact, it is shown that the styrene content of styrene — alpha-methylstyrene copolymers can be determined by ultraviolet spectrophotometry. The relationship between the extinction coefficient at 226nm and the polystyrene content in the mixture shows a linear dependence.     

Preparation of grafted copolymers via oxidized polypropylene

A new and novel class of oxidized polypropylene containing bound peroxide functionalities can be used as polymerization initiators to produce polypropylene‐grafted copolymers. Upon heat treatment, the peroxide functionalities in the oxidized polypropylene act as a source of free radicals, reacting with the unsaturated double bonds of the monomer and initiating polymerization. The grafting reaction is carried out in the solid state in a reactor. The advantage of grafting via this new class of oxidized polypropylene is the elimination of expensive and environmentally unfriendly organic peroxides. A number of monomers have been grafted using oxidized polypropylene, including vinyl acetate, vinyl pyrrolidinone, methacrylic anhydride, and maleic anhydride. Oxidized polypropylene‐grafted copolymers are effective compatibilizers for PP/ETP blends and good coupling agents in glass‐ reinforced formulations. Preparation, characterization, and mechanical properties of terpolymers prepared from sequential grafting of oxidized polypropylene are also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007