A. Valenza

On the compatibilization of PET/HDPE blends through a new class of copolyesters

Polyethyleneterephthalate (PET) and polyethylene are incompatible polymers and their blends show, in general, poor properties. Compatibilization is then a necessary step to obtain blends with good mechanical and barrier properties. In this work different compatibilizing agents were used, i.e. a maleic anhydride elastomer and some new products containing graft-copolymers having polyester segments grafted onto polyethylene backbone chains. Both the functionalized elastomer and the new products drastically improve the morphology and the ductility of the blend. In the case of the modified elastomer the compatibilizing action has been attributed to the formation of H-bonds whereas the copolymers contained in the new products act as compatibilizing agents as they contain polyester segments and polyethylene segments with thermodynamic affinity with PET and polyethylene, respectively.

Effects of mixing time and blend composition on properties and morphologies of polyamide 6/polycarbonate blends

SummaryThe role of the mixing time and the composition of polyamide 6/polycarbonate, PA6/PC, mixtures was investigated by torque and thermal measurements as well as by Molau test and morphological analysis.PA6 and PC are clearly incompatible over the whole range of composition showing well segregated phases. However, at high PA6 content and long time of mixing no more phase separation is observed. This has been attributed to chemical reactions between PA6 and PC molecules, that give rise to some block copolymers, which act as interfacial agents between the two polymers.The copolymer extracted from 75/25 PA6/PC blend, mixed for 45 min., shows Tg at about 65°C and two endotherm peaks at 127 and 211°C.

Processing and Properties of Polycarbonate/Liquid Crystal Polymer Blends

Abstract Rheological and mechanical properties, structural characteristics, extrusion and injection molding behavior of blends of polycarbonate (PC) with a thermotropic, wholly aromatic copolyesteramide have been investigated. The processability of polycarbonate is remarkably improved by addition of small contents of liquid crystal polymer. All the flow curves of the blends lie between those of the pure components. In the processing conditions adopted, the LCP particles are easily elongated in the flow direction. In this direction the elastic modulus rises remarkably with LCP content. The modulus-composition curve is, however, lower than that expected on the basis of an additive rule due to the incompatibility and poor adhesion between the two phases. Finally, injection molding of this extrusion grade PC has been easily performed by adding small contents of LCP. The impact strength values of the injection molding samples of these blends are only slightly lower than that of the pure PC.

The Rheological Behavior of HDPE/LDPE Blends. V. Isothermal Elongation at Constant Stretching Rate

Elongational viscosity data taken on high density‐low density polyethylene blends are presented. The low density polyethylene shows the typical strain hardening while the high density polyethylene shows a Troutonian behavior but at high stretching rate. The blends show an intermediate behavior strongly dependent on the composition and stretching rate.

Shear characterization of CaCO3-filled linear low density polyethylene

Shear properties of CaCO3-filled linear low density polyethylene have been determined over a wide range of filler loading. The viscosity rises with the filler loading especially at low shear rates and a yield value appears for CaCO3-contents larger than 5%. The decrease of the die-swell ratios of the filled samples indicates a reduction of the melt elasticity.

A comprehensive experimental study of the rheological behaviour of HDPE: II. Die-swell and normal stresses

Die-swell data have been obtained for six high-density-polyethylene (HDPE) samples. The data are presented in the form of generalized relationships taking into account both molecular and operational parameters.Data obtained from annealed samples have been used to calculate the first normal-stress difference by using Tanners approach. An analytical expression has been found correlating the normal-stress difference with the shear-stress taking into account the molecular characteristics.

High energy radiation cure of resin systems for structural adhesives and composite applications

Abstract Radiation cure polymerisation of a commercial diglycidyl ether of bisphenol F epoxy resin has been achieved using a 60Co irradiation source, compounding the monomer with few percentage of an onium salt catalyst. The cure process has been monitored by a gamma-calorimetric technique and systems irradiated at doses corresponding to different positions in the gamma-calorimetric curve have been characterised via solubility tests and dynamic mechanical torsion analysis. Changes in both the measured gel fractions and tan δ values were associated with the progress of polymerisation and crosslinking reactions and these were dose dependent. Furthermore, systems irradiated at lower doses exhibited a latent thermal reactivity, undergoing further crosslinking by high temperature treatments, thus suggesting that synergy by the combination of radiation and thermal cure can help to achieve the desired applicative properties of these systems. These results have been discussed in the light of the most accredited radiation-induced polymerisation mechanisms for epoxy resins.

Reactive Blending of Polyamide 6 and Polycarbonate

Abstract In this work structure and mechanical properties of blends of bisphenol-A polycarbonate with polyamide 6 with different molecular weights and different terminal groups are presented. The results show the important role played in the change of the morphology and in the improvements of the mechanical properties by the increasing content of NH2 terminal groups. These results are attributed to the reactions during melt mixing of such groups with polycarbonate.

Extrusion Characteristics of Lubricated Linear Low Density Polyethylene

Abstract Extrusion runs were carried out on a sample of linear low density polyethylene and on samples of LLDPE lubricated with different processing aid. Different action mechanisms were ascertained and explained on the basis of the structure of the three lubricants.

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.