Abstract Rheological properties (melt flow index and melt stability), mechanical properties (tensile strength, flexural strength and impact) of polyamide (PA6) polypropylene (PP) blends were investigated. Influence of potential compatibilizors: 4,4′-diphenyhnethane carbodiimide (OCDI), 4,4′-diphenylmethane bismaleimide (BMI) and 2,2′-(1,4-pheaylene)-bisoxazoline (OX) on mechanical properties and thermostability of initial and glass reinforced polymer blends was also investigated too. We tried to study the structure of glass fiber reinforced composites by mercury intrusion porosimitry. The influence of compatibilizors on molecular weight of PA6 was studied by GPC, on chemical structure of blends was investigated by NMR and IR-spectroscopy. Addition of OCDI and OX (chain extenders) preserves the product formation as the react with the active and carbonyl groups of PA6. BMI has lower reactivity. Grafting of BMI to PP chains improves compatibility in PA6/PP blend and increases PP adhesion to glass fiber. 相似文献
Izod impact strength of PP impact copolymer/Styrene-Butadiene-Styrene blends were evaluated at varied sub-zero temperatures and demonstrated 12 times enhancement in impact strength of 40% SBS containing blend over pure PP-cp at ?40°C. SBS content played a vital role in morphology development as it changes from droplet morphology to elongated ellipsoid to a seemingly networked structure leading towards different fracture mechanisms. Rheological properties of blends evaluated on capillary rheometer showed pseudoplastic behavior at varied shear rates (50 ? 104 s?1) at 220°C and good agreement between experimental shear viscosity and theoretical values as per log additivity principle at high shear rates. 相似文献
Summary
Poly(methyl methacrylate) (PMMA) was produced via free radical polymerization. Polymer samples were sonicated and melt compounded to form 1%, 0.5%, and 0.25% PMMA/soot samples. Soot containing unpurified carbon nanotubes was provided by NASA Ames Research Center. The composites were compression molded and exposed to ionizing radiation in air from a Cesium-137 source. The PMMA/soot samples were characterized before and after exposure to radiation. Differential Scanning Calorimetry (DSC) was used to determine glass transition temperatures. Mechanical properties of composites were characterized via Dynamic Mechanical Analysis (DMA) and microhardness measurements. The glass transition temperatures from this study, when compared to similar studies conducted by Harmon et. al on purified single-wall and multi-wall carbon nanotube composites indicate that soot composites possess lower radiation resistance. 相似文献
Crosslinked particles containing butyl acrylate, methyl methacrylate, and allyl methacrylate are prepared by free‐radical emulsion polymerization. The glass transition temperatures of the polymers are varied by the crosslinking densities in the latex particles. Aqueous acrylate dispersions with polymers of different glass transition temperatures are electrospun with PVA as the matrix polymer. The effects of crosslinking density and Tg on the structure and mechanical properties of the fibers are studied. Crosslinking of unreacted allyl groups is induced by UV irradiation to stabilize the fibers by interparticle crosslinking. Both the ability to undergo interparticle crosslinking and the E modulus depend on the merging of the particles during the electrospinning process.
The anomalous behavior of the glass transition temperature ( T g) in low silica calcium aluminosilicate glasses has been related to the structural modifications observed by neutron and X-ray diffraction. The diffraction data indicate that Al and Si are in tetrahedral sites and that Ca atoms are in distorted octahedral sites. By subtracting the correlation functions for glasses at constant SiO2 or constant Al2O3 content, we have shown that Si and Al atoms are introduced in a different way within the glass structure. Si is present in various Q n sites, while Al resides in Q3 and Q4 sites for glasses with high CaO content and enters fully polymerized Q4 sites with increasing SiO2 or Al2O3 content. The higher proportion of Al in Q3 positions at high CaO content yields a depolymerization of the network. The lower connectivity will contribute to a decrease of the viscosity, which may be at the origin of the decrease of T g for glasses at low silica content. 相似文献
The effect of structure, composition, and cure on the water absorption and Tg of amine-cured epoxies was investigated. Water absorption is considered to depend on the polar group concentration and type, and on the amount of free volume in the polymer network. The contribution of polar groups in terms of their hydrogen bonding capabilities is reflected by the effect of meta (with respect to the diglycidylamino group) chloro, bromo, and methyl substituents on the water absorption of bis[N,N-bis(2,3-epoxypropyl)-4-aminophenyl]methane cured with 4,4′-diaminodiphenylsulphone. The observed water absorptions are in line with the expected electronic effects of the substituents on the basicity of the amine group. Substituents in the ortho position adversely affect the hydrogen bonding capability of the amine group and limit the extent of reaction by steric interference. Examination of four O-glycidyl systems (Epon 825, Epon 1153/114, Epon 1031, and Dow XD-7342) cured with 4,4′-diaminodiphenylsulphone has revealed quite a good linear relationship between the equilibrium water absorption and Tg for a particular hardener concentration irrespective of the epoxy compound employed. Networks ranged from those of low Tg (110°C) and water absorption (1.3%) to those of high values (300°C and 6.1%) for these parameters. Differences in slope for low (50-65%) and high (100%) stoichiometric amounts of hardener are attributed to differences in the relative importance of OH/epoxy and NH2 or NH/epoxy reactions. The theoretical polar group concentrations and polar group type are much the same for these different systems and thus, free volume is considered to be a function of Tg and to play an important part in determining the level of water absorption. 相似文献