Rubber Phase (rubber + phase)

Distribution by Scientific Domains

Selected Abstracts

Effects of addition of acrylic compatibilizer on the morphology and mechanical behavior of amorphous polyamide/SAN blends

D. Becker
Abstract Amorphous polyamide (aPA)/acrylonitrile-styrene copolymer (SAN) blends were prepared using methyl methacrylate-maleic anhydride copolymer MMA-MA as compatibilizer. The aPA/SAN blends can be considered as a less complex version of the aPA/ABS (acrylonitrilebutadiene-styrene) blends, due to the absence of the ABS rubber phase in the SAN material. It is known that acrylic copolymer might be miscible with SAN, whereas the maleic anhydride groups from MMA-MA can react in situ with the amine end groups of aPA during melt blending. As a result, it is possible the in situ formation of aPA-g-MMA-MA grafted copolymers at the aPA/SAN interface during the melt processing of the blends. In this study, the MA content in the MMA-MA copolymer and its molecular weight was varied independently and their effects on the blend morphology and stress,strain behavior were evaluated. The morphology of the blends aPA/SAN showed a minimum in the SAN particle size at low amounts of MA in the compatibilizer, however, as the MA content in the MMA-MA copolymer was increased larger SAN particle sizes were observed in the systems. In addition, higher MA content in the compatibilizer lead to less ductile aPA/SAN blends under tensile testing. The results shown the viscosity ratio also plays a very important role in the morphology formation and consequently on the properties of the aPA/SAN blends studied. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Morphological, mechanical, and rheological studies of PVC/ABS blends in the presence of maleic anhydride

Pegah Mohammad Hosseinpour
A novel method of enhancing compatibility in PVC/ABS blends is the use of ABS-grafted-(maleic anhydride) (ABS- g -MAH) as a compatibilizer. In this study, maleic anhydride was grafted onto ABS (initiated by peroxide) in an internal mixer. Grafting degree was determined by a back-titration method, and certain amounts of the resultant ABS- g -MAH were added to PVC/ABS blends during their melt blending in the mixer. The weight ratio of PVC to ABS was kept at 70:30. Evaluation of compatibilization was accomplished via tensile and notched Izod impact tests, scanning electron microscopy (SEM), and rheological studies. According to the SEM micrographs, better dispersion of the rubber phase and its finer size in properly compatibilized blends were indications of better compatibility. Besides, in the presence of a proper amount [5 parts per hundred parts of PVC (php)] of ABS- g -MAH, PVC/ABS blends showed significantly higher impact strengths than uncompatibilized blends. This result, in turn, would be an indication of better compatibility. In the presence of 5 php of compatibilizer, the higher complex viscosity and storage modulus, as well as a lower loss modulus and loss factor in the range of frequency studied, indicated stronger interfacial adhesion as a result of interaction between maleic anhydride and the PVC-SAN matrix. J. VINYL ADDIT. TECHNOL., 2010. 2010 Society of Plastics Engineers [source]

Sorption and Diffusion of Propylene and Ethylene in Heterophasic Polypropylene Copolymers

Michael Bartke
Abstract Summary: Sorption experiments of ethylene and propylene in different polypropylene powder samples, both homopolymer and heterophasic copolymers with different rubber content, have been carried out in a high-pressure magnetic suspension balance at 10 bars pressure and 70,C. The gross solubilities measured can be well correlated with the rubber content of the polymer samples. Solubility of ethylene and propylene in the rubber phase differ from solubility in the amorphous fraction of the homopolymer, especially the concentration ratio of propylene to ethylene differs significantly between rubber phase and amorphous fraction of the homopolymer. From the slope of monomer uptake, information on kinetics of mass-transfer can be gained. No significant differences were observed in terms of mass-transfer for ethylene and propylene. With increasing rubber content, effective diffusion coefficients increased slightly. By combined sorption studies with powder samples and compressed films, information about both effective diffusion coefficients and the effective length scale of diffusion could be gained. It could be shown, that the particle radius is not the characteristic length of diffusion in the studied powder samples. Mass transfer of nearly all samples could be described by a constant diffusion length of 120 to 130 m, independently on particle size. This indicates that the effective scale of diffusion in polymer particles is in between microparticle and macroparticle scale used in classical particle modeling. [source]

Evaluation of the interfacial state in high impact polystyrene through dynamic mechanical analysis as a function of the synthesis conditions,

R. Daz de Len
High impact polystyrene was synthesized using two series of styrene/butadiene (SB) tapered block copolymers with a polystyrene (PS)/polybutadiene (PB) composition of 30/70 and 10/90 wt%. During the synthesis, concentration of initiator, SB and transfer agent were varied. From dynamic mechanical analysis, the corresponding , relaxation of the rubber phase was detected at low temperature (near ,100C) and that of the glassy PS phase at high temperature (near 100C). Also, another relaxation at temperature near 40C was identified, which was associated to the , relaxation of the glassy PS phase. The variations found in the , relaxation of the rubber phase, were attributed to changes in the morphological structure as a consequence of variation in initiator, SB or transfer agent concentrations and in SB composition. , relaxation showed a strong dependency with the interfacial state between the rubber and the glassy phase, where an increase in the amount of graft PS at the interface, which promotes the interfacial adhesion between phases, causes an increase in the magnitude of , relaxation of the PS phase. The results were attributed to variations in the interfacial area as a result of the change in the particle size and to the contribution of molecular chains of each phase in participating in the relaxation process. POLYM. ENG. SCI., 47:1827,1838, 2007. 2007 Society of Plastics Engineers [source]

Improved toughness in HIPS obtained from different styrene/butadiene-graded block copolymers through modification of the polydispersity index of the PS block,

Graciela Morales
The polymerization of styrene in the presence of graded block copolymers with a polystyrene/polybutadiene composition of 40/60, 30/70, and 20/80 and with a polydispersity index (Mw/Mn) in the polystyrene block varying from 1.1 to 1.6 was studied. As the polydispersity index of the polystyrene block increases, an improvement of up to 50% in the Izod impact toughness of the produced high-impact polystyrene was achieved. The rubber particle morphology type, the size, and the volume fraction of the rubber phase particles could be modified through changes in the composition of the graded block copolymer. The changes that occurred in the rubber phase were mainly generated by the variation in the interfacial tension between the phases, and this variation was principally attributed to an increase in the polydispersity index of the polystyrene block in the precursor copolymer. POLYM. ENG. SCI., 46:1333,1341, 2006. 2006 Society of Plastics Engineers [source]

Effects of rubber-rich domains and the rubber-plasticized matrix on the fracture behavior of liquid rubber-modified araldite-F epoxies

Keqin Xiao
The fracture behavior of a bisphenol A diglycidylether (DGEBA) epoxy, Araldite F, modified using carboxyl-terminated copolymer of butadiene and acrylonitrile (CTBN) rubber up to 30 wt%, is studied at various crosshead rates. Fracture toughness, KIC, measured using compact tension (CT) specimens, is significantly improved by adding rubber to the pure epoxy. Dynamic mechanical analysis (DMA) was applied to analyze dissolution behavior of the epoxy resin and rubber, and their effects on the fracture toughness and toughening mechanisms of the modified epoxies were investigated. Scanning electron microscopy (SEM) observation and DMA results show that epoxy resides in rubber-rich domains and the structure of the rubber-rich domains changes with variation of the rubber content. Existence of an optimum rubber content for toughening the epoxy resin is ascribed to coherent contributions from the epoxy-residing dispersed rubber phase and the rubber-dissolved epoxy continuous phase. No rubber cavitation in the fracture process is found, the absence of which is explained as a result of dissolution of the epoxy resin into the rubber phase domains, which has a negative effect on the improvement of fracture toughness of the materials. Plastic deformation banding at the front of precrack tip, formed as a result of stable crack propagation, is identified as the major toughening process. [source]

Kinetics of the phase selective localization of silica in rubber blends

Hai Hong Le
The Fourier transformed infrared (FTIR) spectroscopy on the rubber-filler gel has been used as a tool for the quantitative characterization of the phase selective silica localization in styrene butadiene rubber (SBR)/natural rubber (NR) blends. The so-called rubber-layer L was introduced to describe the selective wetting behavior of the rubber phases to the filler. SBR/NR blends filled with silica were the focus of the experimental investigation. NR shows a higher wetting rate than SBR. Silane addition does not affect the wetting of NR but slowdowns the wetting of SBR. With increasing chamber temperature the value of the rubber-layer L of all mixtures increases owing to the different thermal activated rubber-filler bonding processes. Using the wetting concept the kinetics of silica localization in the phases of heterogeneous rubber blends was characterized. Because of the higher wetting rate of the NR component, in the first stage of mixing of NR/SBR blends more silica is found in the NR phase than in the SBR phase. In the next stage, silica is transferred from the NR phase to the SBR phase until the loosely bonded components of NR rubber-layer are fully replaced by SBR molecules. POLYM. COMPOS., 31:1701,1711, 2010. 2010 Society of Plastics Engineers. [source]