D. Curto

The rheological behaviour of HDPE/LDPE blends

The rheological behaviour of three types of HDPE/LDPE blends at several compositions (various weight percentages of LDPE) has been studied with the aid of a capillary rheometer and three different capillaries.In particular, entrance effects and shear viscosities have been determined over a wide shear rate region and at different temperatures. Thus activation energies could also be evaluated. Synergistic effects are evidenced when the relevant properties of the homopolymers parents are not too different from one another.

Recycling of degraded polyethylene: Blends with nylon 6

Abstract Recycled polyethylene can be used for blending with nylon to obtain blends with mechanical properties better than those of blends with virgin polyethylene. Moreover, the mechanical properties of these blends are very close to and, in some cases, better than those of the pure nylon and those of blends made with functionalized polyolefines. The carbonyl groups of the photo-oxidized polyethylene react with amino end-groups of nylon 6, giving rise to graft copolymers which act as interfacial agents between the two incompatible phases. Large degrees of photo-oxidation of the polyethylene and intense mixing improve the properties of the blends.

Molecular Weight Dependency of Rheological Characteristics of Linear Low Density Polyethylene

Five samples of linear low density polyethylene, polymerized with l‐butene as comonomer and having different molecular weights but similar molecular weight distributions, have been characterized in shear and nonisothermal elongational flow. From the experimental data, generalized relationships have been found for the zero shear viscosity, the shift factors of the whole viscosity curve, the critical shear rate, the melt strength and the breaking‐stretching ratio. It is then possible to predict with very good confidence values for the most important rheological characteristics of any LLDPE of similar polydispersity from the sole knowledge of the weight average molecular weight, in the range of temperature and flow conditions of industrial interest.

The rheological behavior of HDPE/LDPE blends 4. Instability phenomena in capillary flow

SummaryExperimental data, relative to instability phenomena in capillary flow, have been collected for HDPE/LDPE blends already characterized from a rheological viewpoint. The data comprise morphological observations as well as the determination of critical parameters as a function of the blend composition and of the processing conditions.

Extensional flow of HDPE/LDPE blends

Elongational viscosity data, obtained through the converging flow analysis by Cogswell, are presented for two types of HDPE/LDPE blends at various compositions and different temperatures. The results relative to the homopolymer parents compare favourably with literature data obtained also with different and more sophisticated techniques. Those relative to blends show peculiar features for the two cases: when the newtonian viscosity of the LDPE is higher all the blends show a behaviour typical of the LDPE with a maximum in η el /η0 enhanced at small percentage of HDPE; when the newtonian viscosity of the LDPE is similar to that of the HDPE there is only a gradual change in the properties.

Shear Behaviour of Molten Linear Low Density Polyethylene

The rheological behaviour of molten polyethylene has been widely studied especially with respect to the different structure of the high density and low density samplesI–I0. In particular it is well known that the presence in the LDPE of long chain branching alters dramatically the whole flow curve, the activation energy, the die-swell, the instability phenomena, etc.