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Melt Flow Index (melt + flow_index)
Selected AbstractsSimple method to determine flow characteristics of injectable hydrogelsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010Sundar Babu Nadarajan Abstract This article presents a simple inexpensive method to measure flow and viscoelastic properties of calcium alginate hydrogels or gel solutions and is particularly suitable for quality control in small laboratory settings. This method can be considered an extension of the Melt Flow Index (MFI) method, which is routinely used in the polymer industry to indirectly determine the molecular weight of polymers. Results of alginate gels at various crosslinking densities obtained with this new test are compared to complex viscosity data obtained from a standard cone and plate rheometer, and demonstrate very good correlation. A mathematical model describing the apparent viscosity of the alginate gels in this test has also been developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Flammability and mechanical properties of Al(OH)3 and BaSO4 filled polypropyleneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010S. Tan Abstract The flammability and mechanical properties of Al(OH)3/BaSO4/polypropylene (PP) composites were investigated. The flow, morphological, and thermal properties were also analyzed by melt flow index (MFI), Scanning electron microscopy (SEM), and Differential scanning calorimeter (DSC) studies, respectively. Total filler amount was fixed at 30 wt % to optimize physical characteristics of the composites. In addition to the flame retardant filler Al(OH)3, BaSO4 was used to balance the reduction in impact strength at high filler loadings. Substantial improvement in mechanical properties was achieved for 20 wt % Al(OH)3 (i.e., 10 wt % BaSO4) composition while maximum flammability resistance was obtained for 30 wt % Al(OH)3 composite. SEM studies showed that the presence of aggregated Al(OH)3 particles led to low interfacial adhesion between them and PP matrix ending up with decreased mechanical strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Toughening of recycled polystyrene used for TV backsetJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Xiaoting Fu Abstract The recycled polystyrene (rPS) was toughened with ethylene-octylene copolymer thermoplastic elastomer (POE) and high-density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene-butadiene-styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5,10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle-ductile transition was observed as the SBS content was around 3,5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril-like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m2 and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Continuous Soluble Ziegler-Natta Ethylene Polymerizations in Reactor Trains, 3 , Influence of Operating Conditions upon Process PerformanceMACROMOLECULAR REACTION ENGINEERING, Issue 2 2008Marcelo Embiruçu Abstract The behavior of continuous solution ethylene/but-1-ene polymerizations through Ziegler-Natta catalysts is analyzed, based on a previously developed mathematical model. In order to do that, dynamic simulations are carried out and process responses are analyzed as functions of process operating policies and flowsheet configuration, at conditions that resemble the actual operation of industrial sites. It is shown that system responses are highly nonlinear and very sensitive to disturbances of the operating conditions and that catalyst decay is of fundamental importance for proper understanding of process behavior. Results indicate that mixing conditions inside the reactor vessels exert a significant impact upon the final polymer quality and can be manipulated for in-line control of final resin properties. Finally, it is shown that the development of feed policies, based on the use of lateral feed streams, allows the simultaneous control of melt flow index, stress exponent and polymer density of the final polymer resin. [source] Functionalization of high density polyethylene with maleic anhydride in the melt state through ultrasonic initiationPOLYMER ENGINEERING & SCIENCE, Issue 4 2003Yuncan Zhang Grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) performed in the melt state through ultrasonic initiation by a laboratory-scale ultrasonic extrusion reactor was studied in this paper. The effect of sonic intesity on the amount of grafted MAH, viscosity-average molecular weight and melt flow index of the grafted product was investigated. The results show that the ultrasonic waves can obviously decrease the molecular weight of the grafted product and cause the increase of the amount of grated MAH, implying that the grafting reaction consists of the chain scission and the grafting reaction of the produced macroradicals with MAH. The percentage of grafting of the product amounts to 0.6%; its melt-flow index is between 0.5 and 2.0 g/10 min, depending upon ultrasonic intensity, MAH content and grafting temperature. Compared with the method of peroxide initiation, in this method the crosslinking reaction can be prevented easily through the allocation of ultrasonic intensity. The mechanical properties of the improved HDPE/GF composite produced by ultrasonic initiatives are higher than in those produced by peroxide initiatives. [source] Facile synthesis and characterization of star-shaped polystyrene: self-condensing atom transfer radical copolymerization of N -[4-(,-bromoisobutyryloxy)phenyl]maleimide and styrenePOLYMER INTERNATIONAL, Issue 10 2008Yun Cao Abstract BACKGROUND: Generation of stars around in situ formed cores provides a facile approach to star-shaped polymers. Therefore the self-condensing atom transfer radical copolymerization (SCATRCP) of N -[4-(,-bromoisobutyryloxy)phenyl]maleimide (BiBPM) and a large excess of styrene (St) was investigated. RESULTS: BiBPM and St formed a charge transfer complex (CTC), which underwent the SCATRCP, leading to the branched core initiating the atom transfer radical polymerization of St, finally giving star-shaped polystyrene (PS). Kinetic and structural study showed that a higher dosage of BiBPM resulted in an enhanced polymerization rate, a higher degree of branching and a larger number of short PS arms. Differential scanning calorimetry suggested that the glass transition temperature of the star-shaped PS decreased with molecular weight. Melt rheometry showed that even a slightly branched architecture of the PS led to a significantly lower viscosity; both the melt flow index and the activation energy increased with the degree of branching. CONCLUSION: Due to the preferential consumption of BiBPM and formation of a CTC, even a very low dosage of BiBPM could lead to star-shaped PS, which, in comparison with linear analogues, could possess much better melt fluidity. Copyright © 2008 Society of Chemical Industry [source] The Characteristics of Polyethylene Film for Stretch and Cling Film ApplicationsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004C.M. Small Part I. A range of polyethylene films were prepared from metallocene linear low density polyethylene (m-LLDPE), linear low density polyethylene (LLDPE) and ultra low density polyethylene (ULDPE) resins, containing 0 and 8% polyisobutylene (PIB). FTIR, DSC and mechanical analysis techniques were used to investigate the effect of co-monomer type, density and melt flow index (MFI) on the mechanical performance, orientation and crystallinity of these films. The study established that co-monomer type and MFI were the greatest factors influencing mechanical performance and crystallinity. Crystallinity was found to be the most influential factor governing PIB migration in these films and this in turn was related to polymer type, density and MFI, High MFI, octene co-monomer films exhibited the highest orientation, tear resistance and tack strength and would therefore be suitable for stretch film applications. Ultra low-density polymers gave relatively low tack strength and poor overall mechanical performance. Part II. A range of ethyl vinyl acetate (EVA)/m-LLDPE/EVA co-extruded films was manufactured, with vinyl acetate (VA) co-monomer content of 6, 12 and 18% and PIB content from 0,20%. The films were aged at 45d,C for up to 28 days, to enable tack (cling) development. The results show that film tack strength improved significantly with ageing. Increased VA concentration in the surface layer also showed significant improvement in film tack strength. The film tensile strength, elongation and tear properties in both machine direction (MD) and transverse direction (TD) were not significantly affected by increase in PIB concentration. However, increased VA content showed slight improvement in MD mechanical performance of the films, TD properties were relatively unaffected. Films with 12 to 18% VA in the surface layers produced high surface tack film and the mechanical performance of these films were comparable to mono-layer polyethylenes. These films are suitable for stretch wrap applications and have reduced the overall concentrations of tack additives, though high VA films were more difficult to process. [source] | ||||||||||