Polymers for Advanced Technologies
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Flame retardancy of polypropylene (nano)composites containing LDH and zinc borate Polypropylene (PP)/organically‐modified layered double hydroxides (LDH) and PP/organo‐LDH/zinc borate (BZn) (nano)composites were prepared by the melt blending method. The structures and morphologies of (nano)composites were characterized by X‐ray diffraction and TEM. The flammability properties and thermal stability were studied using TGA, cone calorimeter, limiting oxygen index (LOI), and the UL94 protocol. The basal spacing of organo‐LDH increases to 3.89 nm from 0.76 nm in pristine LDH. When 10% of the organo‐LDH was melt blended with PP, the basal spacing of the LDH increases to 4.01 nm. The onset temperature and thermal decomposition temperature of the PP/organo‐LDH and PP/organo‐LDH/zinc borate (nano)composites have no significant change compared to pristine PP, but the amount of non‐volatile residue remaining at 600°C is significantly higher than that in pure PP. The cone calorimetric results show a 38% reduction in the peak heat release rate for PP/10%BZn and 48, 50 and 63% reductions for PP/organo‐LDH/10%BZn (nano)composites at 3, 5 and 10% organo‐LDH loading. The limiting oxygen indices of all samples increase by a slight amount and all samples can obtain a UL‐94 HB rating. The char content of PP/LDH/BZn and PP/BZn/organo‐LDH (nano)composites is much greater than that of PP/LDH, PP/BZn and PP/organo‐LDH. Copyright © 2011 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 22 Số 7 - Trang 1131-1138 - 2011
Synthesis, characterization and water absorbency properties of poly(acrylic acid)/sodium humate superabsorbent composite Abstract A novel poly(acrylic acid)/sodium humate superabsorbent composite was synthesized by aqueous solution polymerization of acrylic acid using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of sodium humate. The effects on water absorbency such as initial monomer concentration, degree of neutralization of acrylic acid, amount of crosslinker, initiator and sodium humate, etc. were investigated. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with a sodium humate content of 20% exhibited an absorption of 1268 g H2 O/g sample and 93 g H2 O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. Swelling rate and water retention tests were also carried out. The results show that sodium humate, as a kind of functional filler, can enhance comprehensive properties of superabsorbent composite and reduce the product cost significantly. Copyright © 2005 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 16 Số 9 - Trang 675-680 - 2005
A study on the micro‐injection molding of multi‐cavity ultra‐thin parts Abstract In this study, we report the micro‐injection molding of ultra‐thin parts (100, 250, and 500 µm). The results show that the flow resistance increases as the cavity becomes thinner. The melt front is not symmetric when filling a four‐cavity ultra‐thin part and filling the eight‐cavity mold under a low temperature. If we increase the mold temperature or cavity thickness, the melt front becomes symmetric. Finally, we construct the operation windows of molding for three kinds of plastics (PS, PMMA, PC) and provide a molding range based on mold temperature and injections speed. Meanwhile, the relationship between the thickness and the operation windows are also investigated. The thinner the cavity is, the smaller the operation window is. We need to increase the injection speed significantly for molding the ultra‐thin parts with micro‐features on both surfaces which are 60 µm in thickness. Furthermore, we succeed in molding 30 µm ultra‐thin parts in this experiment. Copyright © 2009 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 22 Số 6 - Trang 891-902 - 2011
The interfacial enhancement of LLDPE/whisker composites via interfacial crystallization Abstract Interfacial interaction plays a key role in the preparation of high performance polymer composites. In this work, in order to explore the possibility to enhance the interfacial interaction via interfacial crystallization of polymer matrix onto the filler surface, interfacial crystallization structure and mechanical properties of linear low density polyethylene (LLDPE)/whisker composites were investigated. The composites were firstly prepared by melt compounding, followed by processing in both traditional and dynamic injection molding. DSC, WAXD, SEM were used to characterize the interfacial crystallization structure. And the mechanical properties were measured by tensile testing. An imperfect shish‐calabash structure, with whisker served as shish, and irregular LLDPE spherulite as imperfect calabash, was formed during common injection molding processing. Such a structure was considered as the main reason for the strong interfacial adhesion and the obviously improved tensile strength and modulus. Furthermore, introducing shear could cause the formation of relatively perfect shish‐calabash structure, leading to the stronger interfacial adhesion. Copyright © 2011 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 23 Số 3 - Trang 431-440 - 2012
UV curable waterborne polyurethane acrylate dispersions based on hyperbranched aliphatic polyester: effect of molecular structure on physical and thermal properties Abstract A novel waterborne hyperbranched polyurethane acrylate for aqueous dispersions (WHPUDs) based on hydroxy‐functionalized hyperbranched aliphatic polyester Boltorn™ H20 was investigated. The effects of structural composition and crosslinking density have been studied in terms of swellability by water, thermal degradation, viscosity changes as well as transmission electron microscopy (TEM) morphology. The swell ratio showed an increasing trend with the higher concentration of ionic group, which is due to the increased total surface area of particles. The results of thermogravimetric analysis (TGA) for cured WHPUD films indicated good thermal stability with no appreciable weight loss until 200°C. The activation energies were evaluated and were found in the range 154–186 kJ mol−1 . It was observed that an increase in hard segment content provoked the increases in thermal degradation temperature and activation energy of waterborne dispersions. The transmission electron photographs revealed that the average particle sizes of aqueous dispersions were in the range 30–125 nm. Owing to the enlargement of the stabilization site, the particle size decreased as the content of carboxyl group and degree of neutralization increased. The viscosity of WHPUDs increased rapidly with increasing the degree of neutralization. Moreover, water showed a favorable viscosity reduction effect. Copyright © 2004 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 15 Số 11 - Trang 669-675 - 2004
Preparation and properties of polycarbonate/polyhedral oligomeric silsesquioxanes (POSS) hybrid composites Abstract Octaphenylsilsesquioxane (PH‐POSS) and octa(γ‐methacryloxypropyl)silsesquioxane (MA‐POSS) were successfully synthesized by hydrolytic condensation of phenyltrichlorosilane and γ‐methacryloxypropyltrimethoxysilane, and characterized by Fourier transform infrared (FT‐IR), 1 H and 29 Si nuclear magnetic resonance (NMR), and matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrum. Morphology, degradation behavior, thermal, and mechanical properties of hybrid composites were studied by transmission electron microscopy (TEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), surface contact angle (SCA), tensile, and impact testing. Domains of PH‐POSS and MA‐POSS dispersed in the matrix with a wide size distribution in a range of 0.1–0.5 µm, while PH‐POSS exhibited a preferential dispersion. Because of the possible homopolymerization of MA‐POSS during the melt blending, the glass transition temperature of polycarbonate (PC)/MA‐POSS composites remained nearly unchanged with respect to PC/PH‐POSS composites that showed a depression of T g due to the plasticization effect. It is interesting to note that the incorporation of POSS retarded the degradation rates of PC composites and thus significantly improved the thermal stabilities. SiO fractions left during POSS degradations were a key factor governing the formation of a gel network layer on the exterior surface. This layer possessed more compact structures, higher thermal stabilities, and some thermal insulation. In addition, percentage residues at 700°C (C 700 ) significantly increased from 10.8% to 15.8–22.1% in air. Fracture stress of two composites showed a slight improvement, and the impact strength of them decreased monotonically with the increase of POSS loading. Copyright © 2011 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 23 Số 4 - Trang 765-775 - 2012
Dielectric spectroscopic analysis of polyvinyl chloride nanocomposites loaded with Fe<sub>2</sub>O<sub>3</sub> nanocrystals Iron oxide (α‐Fe2 O3 ) nanocrystals powder was successfully synthesized via the sol‐gel method. The microstructural examination of the synthesized nanocrystals confirmed the formation of α‐Fe2 O3 (hematite) structure using X‐ray diffraction and Fourier transform infrared. The synthesized nano‐hematite powder with different weight percentage up to 5 wt% was introduced to polyvinyl chloride (PVC) to fabricate PVC/Fe2 O3 nanocomposites using the solution‐cast technique. The dielectric spectroscopic analysis for the investigated samples has been studied at room temperature and at different temperatures up to 120°C. The real part of the permittivity (ε′ ) exhibited a significant dependence on filler concentrations throughout whole temperature range. However, the dependency of both of the loss tangent (tanδ ) and AC conductivity (σ ac δ for the investigated nancomposites referred to the α‐relaxation around 70°C, which is close to glass transition temperature of the investigated PVC. The dependency of the dielectric strength on Fe2 O3 nanofiller concentration was observed with enhancement in the dielectric strength reach to 20.5% for PVC/0.7 wt% Fe2 O3 nanocomposite higher than the recorded value for the pristine PVC.
Polymers for Advanced Technologies - Tập 29 Số 9 - Trang 2477-2485 - 2018
Preparation and characterization of cationic polystyrene latex particles of different aminated surface charges Abstract Functionalized polystyrene latex particles were obtained either by seed particle functionalization or by the shot‐growth procedure using 2,2′‐azobis (2‐amidino‐propane) dihydrochloride as an initiator and vinylbenzylamine hydrochloride as a cationic monomer. The capabilities of both processes to produce functionalized particles in terms of functionalization yields coming from surface amino group titrations were compared. Different titration methods were performed and a new technique was introduced using fluorescamine.
Polymers for Advanced Technologies - Tập 6 Số 7 - Trang 480-488 - 1995
Preparation of silica/polymer hybrid microspheres and the corresponding hollow polymer microspheres with functional groups Abstract Monodisperse functional silica/polymer core–shell hybrid microspheres were prepared by a two‐stage reaction with silica grafting of 3‐(methacryloxy)propyl trimethoxysiliane (MPS) as core and polymer as shell having various functional groups such as chloromethyl, pyridyl, carboxylic acid, hydroxyl, and ester. MPS‐modified silica core was synthesized by the Stöber method and subsequently grafted with MPS as the first‐stage reaction. The functional polymer shell was then encapsulated over the MPS‐modified silica by distillation precipitation copolymerization of divinylbenzene (DVB) as a crosslinker and comonomers with different functional groups, including chloromethylstyrene (CMSt), vinyl pyridine (VPy), methacrylic acid (MAA), 2‐hydroxyethylmethacrylate (HEMA), ethyl methacrylate (EMA), ethyleneglycol dimethacrylate (EGDMA), and trimethylol propanetrimethacrylate (Trim), in neat acetonitrile with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator. The encapsulation of the functional polymer shell onto the MPS‐modified silica core particles was driven by the capture of oligomer radicals the vinyl groups on the surface of the MPS‐modified silica cores during the second‐stage distillation precipitation copolymerization in the absence of any stabilizer or surfactant. The functionality and the shell thickness of the inorganic/polymer core–shell hybrid particles were controlled by the amount of DVB crosslinker and the functional comonomers during the copolymerization. The corresponding hollow polymer microspheres with various functional groups, including chloromethyl, pyridyl, carboxylic acid, and ester groups were further developed after the selective removal of silica core with hydrofluoric acid. The functional core–shell silica/polymer hybrid microspheres and the corresponding functional hollow polymer microspheres were characterized with transmission electron microscopy (TEM) and Fourier transform infrared spectra (FT‐IR). Copyright © 2008 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 19 Số 12 - Trang 1922-1930 - 2008
Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6 Abstract A hyperbranched polyamine was prepared using an A2 + B3 approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.
Polymers for Advanced Technologies - Tập 22 Số 12 - Trang 2237-2243 - 2011
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