Rheological,thermal, and curing properties of natural rubber‐g‐poly(methyl methacrylate)

Graft copolymers of NR and PMMA (i.e., NR‐g‐PMMA) were prepared with the bipolar redox initiation system, using various percentages of molar ratios of NR/MMA at 95/5, 90/10, 80/20, 70/30, and 60/40. It was found that the Mooney viscosity, shear stress, and shear viscosity of the NR‐g‐PMMA increased with an increase in the molar ratio of MMA used in the graft copolymerization. This may be attributed to an increasing trend of the chemical interaction between polar functional groups within the grafted PMMA molecules. Furthermore, a decreasing trend of storage moduli was observed with increasing molar ratios of MMA. The glass transition temperature was obtained from the tan δ curves. We found a slightly increasing trend of the T_g's with an increase in molar ratios of MMA used in the grafting reaction. The NR‐g‐PMMA was later compounded using TBBS as an accelerator. With an increase in molar ratios of MMA in the grafting reaction, we observed an increasing trend of minimum torque, maximum torque, cure time, and scorch time, but quite similar levels of torque difference and crosslink density. Furthermore, the tensile strength of the NR‐g‐PMMA gum vulcanizate increased with an increase in molar ratios of MMA, whereas the elongation at break decreased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1600–1614, 2006     

Influences of the grafting percentage of natural rubber‐graft‐poly(2‐hydroxyethyl acrylate) on properties of its vulcanizates

The graft copolymerization of 2‐hydroxyethyl acrylate (HEA) monomer onto natural rubber (NR) latex was successful using cumene hydroperoxide and tetraethylene pentamine as redox initiators. The grafting of poly(2‐hydroxyethyl acrylate) (PHEA) on the NR particles was confirmed by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy and TEM. The NR‐g‐PHEA with various grafting percentages (0%, 8.7%, 14.3% and 18.7%) was compounded on a two‐roll mill with a sulfur vulcanization system. The effects of grafting percentage on the cure characteristics, dielectric properties, thermal properties and physical properties of NR‐g‐PHEA vulcanizates were investigated. It was found that increased grafting caused NR‐g‐PHEA vulcanizates to have reduced water contact angle, scorch time and cure time, while the dielectric constant and dissipation factor increased. The NR‐g‐PHEA vulcanizate with 8.7% grafting exhibited the highest delta torque (M_H ? M_L), crosslink density, tensile strength, moduli at 100%, 200% and 300% strains, and hardness, with insignificant loss of elongation at break in comparison to the other cases. © 2018 Society of Chemical Industry     

Thermal stability,aging properties,and flame resistance of NR‐based nanocomposite

Polymer/clay nanocomposites have some unique properties due to combination of flame resistance and improved mechanical and thermal stability properties which are important to enhance the material quality and performance. The objective of this work was to investigate the effect of organically modified montmorillonite (org‐MMT) on the thermal and flame retardant as well as hardness and mechanical properties of the nanocomposites based on the natural rubber (NR). It was shown that by the addition of 3 wt % of org‐MMT to NR, its aging hardness rise was decreased more than 55% and the ignition time was delayed about 150%. The reduction in heat release rate peak value was equal to 54% compared to the pristine NR. Addition of org‐MMT improved the thermal stability of the NR. Furthermore, nanocomposites which were calendared before curing showed much more thermal stability and fire resistance than those which contained similar amount of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Compounding of poly(dimethyl siloxane) to reduce tack in natural rubber

Tack in natural rubber latex was reduced by compounding poly(dimethyl siloxane) (PDMS) emulsion in concentrated latex. Sheet and dipped film surfaces were examined with Fourier transform infrared spectroscopy using attenuated total reflection (FTIR–ATR) and by contact angle measurements. Autohesive tack and tensile properties were also determined. For both sheet and dipped film, FTIR–ATR showed that the PDMS concentration was higher at the glass surface than at the air surface. The contact angle of ethylene glycol on the rubber decreased with increasing PDMS content. Autohesive tack for sheet and dipped film also decreased with increasing PDMS amount; however, annealing for 1 week at 70°C in air did cause tack to rise in the sheets. The rubber surface could be made nonadhesive by addition of sufficient PDMS. PDMS caused a decrease in tensile strength for the sheet, especially after annealing; however, PDMS did not cause a substantial decrease in percentage elongation for the sheets, except at relatively high PDMS contents. The tensile strength and percentage elongation for dipped film was not affected by PDMS over the much more limited PDMS concentration range studied. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 519–526, 2001     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

Use of natural rubber‐g‐polystyrene as a compatibilizer in casting natural rubber/polystyrene blend films

Natural rubber/polystyrene (NR/PS) blend films with weight ratios of 70/30, 60/40, and 50/50 were prepared using polystyrene grafted natural rubber copolymers (NR‐g‐PS) as the compatibilizer. Copolymers with molar ratios of 90/10, 80/20, and 70/30 were synthesized via emulsion copolymerization using tert‐butyl hydroperoxide/tetraethylene pentamine as an initiator. The copolymers were subsequently added into the blends at 0, 5, 10, 15, 20, 25, and 30 phr. The mixtures were cast into films by the solution‐casting method using toluene as the casting solvent. Mechanical and morphological properties of the prepared films were investigated. The film prepared from 80/20 NR‐g‐PS showed higher tensile and tear strength, as well as finer domain size of the dispersed phase, than those prepared from 90/10 and 70/30 NR‐g‐PS. However, the mechanical properties of the films were decreased at high loading of the copolymers. In addition, themogravimetric analysis revealed that weight loss was decreased upon introduction of the compatibilizer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 826–831, 2005     

Pervaporation membranes from natural rubber latex grafted with poly(2‐hydroxyethyl methacrylate) (NR‐g‐PHEMA) for the separation of water–acetone mixtures

NR‐graft‐PHEMA latexes were synthesized by the use of graft emulsion polymerization. By increasing the HEMA monomer concentration, we found that the grafting percentage (GP) also increased. In addition, GP increased significantly at low initiator concentrations before it leveled off at moderate concentrations, and a slight decrease was observed at high initiator concentrations. NR‐g‐PHEMA latexes were prepared as pervaporation membranes for the separation of water–acetone mixtures. From the equilibrium swelling, the nonideal behavior of membrane swelling in water–acetone mixtures was found such that there appeared the maximum swelling degree at a certain concentration of liquid mixtures. Moreover, the water concentration at maximum swelling shifted to high water concentration with increasing amount of graft‐PHEMA. The sorption study suggested the preferential sorption of water on the membranes. Also, the sorption isotherms implied that there was a coupling between water and acetone molecules. Pervaporation separation of water–acetone mixtures was studied with NR‐g‐PHEMA membranes. As the feed water concentration increased, the partial water fluxes increased in contrast to the partial fluxes of acetone. From the permeation ratio, θ_w, the strong coupling of acetone on the water transport was observed, particularly for the membrane with high graft‐PHEMA under acetone‐rich conditions. As the feed temperature increased, the total permeation across the membranes was enhanced. The partial fluxes of water and acetone as a function of temperature followed the Arrhenius relationship by which the activation energies for permeation were estimated as 3.53 kJ/mol for water and 21.95 kJ/mol for acetone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

环状膦酸酯阻燃PTT纤维及其性能研究

采用自制的环状膦酸酯(MBEP)、三聚氰胺和溴化环氧树脂,按一定配方与聚对苯二甲酸丙二醇酯(PTT)共混造粒、纺丝制备阻燃PTT纤维,研究了阻燃剂对纤维阻燃性能和纺丝性能的影响。结果表明,添加质量分数3．0%的MBEP和4．0%的三聚氰胺时,PTT树脂的阻燃性能较好,极限氧指数达28%以上,磷氮协同阻燃效应明显,其纺丝性能良好,得到的阻燃PTT纤维断裂强度达约3．0 cN/dtex。     

4,4′,4′′–三膦酸甲酯三苯胺的合成及应用

以三苯胺为原料，通过亲电取代反应制备得到中间体4,4′,4′′–三碘代三苯胺（TITPA），该中间体与亚磷酸三甲酯在Pd(PPh3)2Cl2催化下经Arbuzov重排得到目标产物4,4′,4′′–三膦酸甲酯三苯胺（TPTPA）。通过1HNMR、13CNMR、31PNMR、高分辨质谱和元素分析对目标产物进行了结构表征，并考察了催化剂种类与用量、反应温度、反应时间对目标化合物产率的影响。结果表明，最佳合成条件为： n（Pd(PPh3)2Cl2）∶n（TITPA）= 0.18∶1.00，反应温度150℃，反应时间5h。在该条件下，目标产物TPTPA的收率可达82.5%。接着，TITPA用于PVC的阻燃改性。结果表明，当TPTPA添加量为10%（以PVC树脂的质量为基准，下同），样品的极限氧指数可达29.6%、UL94垂直燃烧达V-0级，且力学性能保持良好。。     

Thermal behavior and flame retardancy of flexible poly(vinyl chloride) treated with Al(OH)3 and ZnO

Al(OH)₃ as flame retardant and smoke suppressant for flexible poly(vinyl chloride) was evaluated alone and with ZnO, using thermal analytical techniques, limiting oxygen index and smoke density rating tests. The thermal behavior and flammability of the samples treated with Al(OH)₃ and ZnO were studied by differential thermal analysis and thermogravimetric analysis. The activation energy was calculated by using the Vyazovkin model‐free kinetic and Kissinger methods. The results showed that the flame‐retardant and smoke‐suppressant properties of the samples treated with Al(OH)₃ and ZnO were related to the content of ZnO and the thermal effect during the process of thermal degradation of the samples. Copyright © 2005 Society of Chemical Industry     

Study of the effect of natural rubber‐graft‐o‐aminophenol on the thermal stability and mechanical properties of nitrile rubber

The grafting copolymerization of natural rubber and o‐aminophenol was carried out by using two‐roll mill machine. The prepared grafted antioxidant, NR‐graft‐o‐AP, analyzed by using Infrared and ¹H‐NMR Spectroscopy techniques. The thermal stability, mechanical properties, and ultrasonic attenuation coefficient were evaluated for NBR vulcanizates containing the commercial antioxidant, PBN, and the prepared grafted antioxidant, NR‐graft‐o‐AP, and the control vulcanizate. Results of the thermal stability indicate that the prepared NR‐graft‐o‐AP can protect NBR vulcanizate against thermal treatment much better than the commercial antioxidant, PBN, and control mix, respectively. The prepared grafted antioxidant improves the mechanical properties of NBR vulcanizate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

基于磷杂菲衍生物多组分无卤阻燃天然橡胶的制备及性能

将磷杂菲/三嗪双基协同阻燃剂（TGD）、甲基膦酸二甲酯（DMMP）、可膨胀石墨（EG）及氢氧化铝（ATH）复配添加到天然橡胶（NR）中制备阻燃NR硫化胶,考察了TGD/DMMP/EG/ATH复配阻燃剂对NR硫化胶的阻燃性能、热稳定性及物理机械性能的影响。结果表明,TGD/DMMP/EG/ATH复配阻燃剂可有效提升NR硫化胶的阻燃性能和热稳定性,并降低燃烧过程中的热释放速率。当TGD/DMMP/EG/ATH复配阻燃剂的用量为60份（质量）时,NR硫化胶的极限氧指数可达28.4%,残炭质量分数可达25.61%,热释放速率可降低95%,总热释放量可降低21%。TGD/DMMP/EG/ATH复配阻燃剂对NR硫化胶的物理机械性能影响不大。     

Development of a biodegradable rice straw‐g‐poly(methyl methacrylate)/sodium silicate composite flame retardant

Natural fiber composites have been prepared by grafting hydrophobic monomer methyl methacrylate (MMA) onto chemically modified rice straw (RS) using complex initiating system [CuSO₄/glycine/ammonium persulfate (APS)] in an aqueous medium with and without the additive, sodium silicate (SS). The chemically modified RS, RS‐g‐PMMA, and RS‐g‐PMMA/SS composite have been characterized by FT‐IR, and their morphology was studied by scanning electron microscopy (SEM). The thermal behavior and tensile properties of the samples have been studied, and the flame retardant properties have also been evaluated by limiting oxygen index (LOI) test and cone calorimetry. The biodegradation and water absorbency have been carried out for its ecofriendly nature and better commercialization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of a novel intumescent flame retardant and its application in EVM

A novel phosphorous-nitrogen structure containing intumescent flame retardant, 4,4-diaminodiphenyl methane bi(2,2-dimethyl-1,3-propanediol) phosphoramidate (DBDPP) was synthesized and characterized. Thermal stability and flammability properties of ethylene vinyl-acetate copolymer rubber(EVM)/DBDPP composites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) test and UL-94 measurement, respectively. The results showed that the addition of DBDPP enhanced the thermal stability and flame retardancy of EVM significantly. The weight of residues improved greatly with the addition of DBDPP. SEM investigations revealed that a strong charred layer was formed from EVM/DBDPP composites during combustion. It is confirmed that the char structure was a critical factor for flame retardancy of EVM rubber. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization and thermal properties of poly(n‐butyl acrylate‐g‐styrene) graft copolymers

Poly(butyl acrylate‐g‐styrene) graft copolymers were prepared by free‐radical polymerization using a polystyrene macromonomer carrying a methacryloyloxy group at the chain end and they were characterized by size‐exclusion chromatography, and Fourier transform infrared spectroscopy. Glass transition temperatures and degradation behavior were determined by thermal analysis. Only a single glass transition temperature was observed for the resulting graft copolymers, indicating the miscibility between the poly(styrene) phase and poly(butyl acrylate) (pBA) phase in the graft copolymer. The incorporation of polystyrene segments in the graft copolymer improved the thermal stability of pBA and enhanced the apparent activation energy for the thermal degradation of pBA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 783–789, 2001     

Thermal polymerization of a brominated flame retardant in a glass‐fiber‐reinforced polypropylene—quantitative analysis

Pentabromobenzylacrylate (PBBA) is a possible candidate for use as a fire retardant (FR) in polypropylene (PP) composites. While PBBA imparts FR properties to the PP composite, it also affects adversely its mechanical properties. The FR may undergo thermal polymerization or grafting to the PP chains during processing. To study the effect of the different forms of FR (monomer, polymerized, or grafted) on composite properties, we have quantified the extent of FR polymerization and extent of grafting onto the PP chains. Fourier transform infrared microscopy was used in this work to determine the extent of polymerization and the spatial distribution of the FR. The latter was found to be homogeneous throughout the composite. Thermal polymerization of the FR during extrusion is varied mainly by the addition of an antioxidant. The grafting process of the FR onto PP depends on the degree of thermal polymerization, and therefore on the addition of antioxidant. The limiting value for grafting achieved at full polymerization is ～10% w/w. The grafted FR was found to have a significant effect on PP crystallinity, and hence it is expected to affect the mechanical properties as well. Bromine analysis indicates the FR has reacted with filler surfaces as well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1506–1515, 2003     

Fire and thermal properties of PA 66 resin treated with poly‐N‐aniline‐phenyl phosphamide as a flame retardant

In this study, a halogen‐free phosphorous‐nitrogen synergistic flame retardant, poly‐N‐aniline‐phenyl phosphamide (PDPPD), was synthesized. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis data confirmed the structure of PDPPD. The essential FR PA66 was polymerized with PA66 pre‐polymer and PDPPD pre‐polymer, prepared from PDPPD and adipic acid. The limit oxygen index and UL‐94 test results of FR PA66 reached 28% and V‐0, respectively, when the contents of PDPPD pre‐polymer were 4.5 wt%. The thermo‐gravimetric and differential scanning calorimetry results demonstrated that the initial decomposition temperature of FR PA66 was 43 °C lower than that of pristine PA66 from 385 to 342 °C; however, the peak decomposition temperature was 36 °C higher than that of pure PA66 from 437 to 473 °C, when the contents of PDPPD pre‐polymer reached 4.5 wt%. Flame retardant mechanism was studied by cone calorimeter testing and SEM‐EDX, confirming that the heat release rate (HRR), total heat release (THR), and total smoke product (TSP) decreased slightly, and PDPPD followed the gas phase flame retardant mechanism. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of composition on the dynamic and mechanical properties of natural rubber–poly(methylmethacrylate) blends

The miscibility of the components in natural rubber–poly(methylmethacrylate) blends for potential use as reinforced rubbers was evaluated using the glass transition temperatures, peak widths of the loss tangent peak at the glass transition and the complex heat capacity data obtained from dynamic mechanical thermal analysis (DMTA), and modulated differential scanning calorimetry (MDSC). In addition, the effect of the poly(methylmethacrylate) content on the dynamic mechanical and the physical properties such as tensile behavior and hysteresis loss was studied. DMTA and MDSC data clearly indicated that the blends were phase‐separated. Nevertheless, the glass transition temperature of the natural rubber component in the 30–50 wt % NR/PMMA blends has shifted to higher temperatures compared to the natural rubber treated under the same condition, indicating some limited extent of mixing of components in these blends. The physicomechanical properties including moduli at 100, 300, and 500% and tensile strength of the NR/PMMA blends were determined. Incorporation of PMMA into NR matrix improved the strength properties of the NR/PMMA blends prepared reasonably akin to interpenetrating polymer networks (IPN) polymerization method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and physical properties of poly(l‐lactic acid)‐poly(dimethyl siloxane) multiblock copolymers prepared by direct polycondensation

Multiblock copolymers consisting of poly(l ‐lactic acid) and poly(dimethyl siloxane) were prepared by the polycondensation of oligo(l ‐lactic acid) (OLLA) with dihydroxyl‐terminated oligo(dimethyl siloxane) and dicarboxyl‐terminated oligo(dimethyl siloxane). Copolymers with number‐average molecular weights of 18,000?33,000 Da and various content ratios of oligo(dimethyl siloxane) (ODMS) unit were obtained by changing the feed ratio of these oligomers. A film prepared from the copolymer with an ODMS content ratio of 0.37 exhibited two independent peaks at ?107°C and 37°C in the mechanical loss tangent for temperature dependence, suggesting the formation of microphase separation between the OLLA and ODMS segments. The film had a tensile strength of 3.2 MPa and a high elongation of 132%. The film also exhibited a high strain recovery even after repeated straining. The incorporation of dimethyl siloxane units as multiblock segments was confirmed to improve the flexibility of poly(l ‐lactic acid). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40211.     

一种环状膦酸酯对ABS阻燃及热稳定性的影响

以白行合成的环状膦酸酯（DMDP）为阻燃剂,研究了DMDP阻燃ABS树脂的阻燃性能和热性能。实验结果表明,DMDP的加入可以提高ABS树脂的极限氧指数（LOI）;热重分析表明无论是空气还是氮气氛围,DMDP于ABS树脂前分解,有利于促进ABS树脂成炭,提高高温残余量。