The Canadian Journal of Chemical Engineering

Utracki, Leszek A.

doi: 10.1002/cjce.5450800601pmid: N/A

Most polymer blends are immiscible and need to be compatibilized. The compatibilization must accomplish: (i) optimization of the interfacial tension; (ii) stabilize the morphology against high stresses during forming; and (iii) enhance adhesion between the phases in the solid state. Compatibilization is accomplished either by addition of a compatibilizer or by reactive processing. This review will focus on the three aspects: description of the interphase, compatibilization by addition and reactive compatibilization.

Deyrail, Yves; Michel, Alain; Cassagnau, Philippe

doi: 10.1002/cjce.5450800602pmid: N/A

Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene‐methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break‐up times of PC fibers were taken into account. Shear rate and quenching‐time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching.

Mighri, Frej; Huneault, Michel A.

doi: 10.1002/cjce.5450800603pmid: N/A

This paper reviews the dispersion mechanisms in viscoelastic systems under relatively high shear rate conditions. In particular, two non‐Newtonian deformation and breakup mechanisms were revealed by flow visualization in a transparent Couette shearing setup. The first one is the dispersed droplet elongation perpendicular to the flow direction. This was observed only for viscoelastic drops and had been associated to normal force buildup in the droplet. The second deformation/breakup mechanism was observed in very high viscosity ratio polymer systems. It consists in erosion at the drop surface. Clouds of very small ribbons and sheets were developed around the drop then stretched and finally broken into very small droplets, rapidly distributed in the matrix.

Serra, Christophe; Schlatter, Guy; Bouquey, Michel; Muller, René; Terrisse, Jean

doi: 10.1002/cjce.5450800604pmid: N/A

The influence of extrusion parameters on the morphology of non‐reactive blends has been investigated by means of online light‐scattering measurements. A light‐scattering device was especially designed to be mounted on a twin screw extruder at different locations along the barrel. The obtained light‐scattering patterns were interpreted with respect to the variation of the processing parameters. Preliminary results show that there is little effect of the rotational speed, position along the screw and feed throughput on the morphology but a quite noticeable effect of the blend composition. These results were confirmed by SEM micrographs.

Yin, Z; Koulic, C; Pagnoulle, C; Jérôme, R

doi: 10.1002/cjce.5450800605pmid: N/A

Poly(methyl methacrylate) (PMMA) containing 50 wt% of anthracene (anth) labeled reactive PMMA chains (thus end‐capped by an anhydride (anh) or an isocyanate (NCO)) has been melt blended with polystyrene containing 33 wt% of chains end‐capped by an aliphatic amine (PS‐NH2) at 180°C. Conversion of anth‐PMMA‐anh and anth‐PMMA‐NCO into PMMA‐b‐PS copolymers has been determined by SEC with a UV detector. The interfacial reaction mainly occurs in the initial mixing stage (⩽1.0 min), although at a rate which depends on the reactive groups attached to PMMA. Moreover, this interfacial reaction rate controls how the phase morphology is developed.

Huitric, Jacques; Moan, Michel; Klopffer, Marie‐Hélène

doi: 10.1002/cjce.5450800606pmid: N/A

We have studied the effect of the amount Φc of a reactive compatibilizer on the rheological properties of a polyethylene/polyamide blend, under steady shear and transient extensional flows. Here, we propose to describe the viscosity η(γ) and the first normal stress coefficient γ1(γ) using a Carreau‐type power‐law model, which is a three‐parameter model. A single model is sufficient to express the behavior of γ1(γ) On the other hand, the complete η(γ) curve is described by the superposition of two Carreau models, in relation to the presence of two relaxation mechanisms. Moreover, the extentional viscosity ηE(ϵ), estimated using the end pressure drop observed in capillary flow experiments, is expressed by a two‐parameter power‐law model.

Chopra, Divya; Kontopoulou, Marianna; Vlassopoulos, Dimitris; Hatzikiriakos, Savvas G.

doi: 10.1002/cjce.5450800607pmid: N/A

A rheological study of the phase behaviour and the dynamics in the immiscible region of a model partially miscible Upper Critical Solution Temperature (UCST) blend was carried out by using a series of nearly monodisperse polydimethylsiloxane (PDMS) of varying molecular weights blended with polyethylmethylsiloxane (PEMS). The complete phase diagram was established through steady shear rheology, optical microscopy and light scattering. The UCST, interfacial tension and morphology of these blends are very sensitive to the molecular weight of the constituents. Partial miscibility was observed only when the Mw of PDMS was sufficiently low. The viscoelastic behaviour in the phase separated region can be modeled successfully using the Palierne model.

Covas, José A.; Carneiro, Olga S.; Maia, João M.; Filipe, Susana A.; Machado, Ana V.

doi: 10.1002/cjce.5450800608pmid: N/A

Intermeshing twin‐screw extruders have been recently identified as useful in special application niches such as the extrusion of PVC dry blends (counter‐rotating machines) and compounding operations (co‐rotating machines). Thus, it is of interest to study the mechanical and/or chemical effects that occur along the screw axis of the extruders, since they will dictate the characteristics and performance of the final material. This work aims at illustrating the usefulness of a simple experimental tool recently developed for the study of the physical, chemical and morphological evolution along the extruder of polymer based systems, data being presented and discussed for a number of composites and blends.

Michel, Alain; Cassagnau, Philippe; Dannoux, Morgane

doi: 10.1002/cjce.5450800609pmid: N/A

The alcoholysis of PET with diols in the presence of dibutyltinoxide was carried out in a twin‐screw extruder with residence times of 1 min and without solvent. The reaction led to scissions of PET chains and to the synthesis of oligoester α,ω‐diols with average number molecular weights of about 1000 g·mol—1 characterised by conventional techniques such as NMR, SEC and MALDI‐TOF. The alcoholysis kinetics was studied with a rheological tool under selected conditions, and it was shown that this reaction is quite compatible with the residence times in an extruder. This study clearly shows that the oligoesters synthesised by reactive extrusion have characteristics similar to the oligoesters synthesised by batch processes over many hours. Furthermore, the melting temperature of these oligoesters can be controlled between room temperature and 220°C by using diols with different structures for the alcoholysis.

Mehrabzadeh, Mahmood; Kamal, Musa R.

doi: 10.1002/cjce.5450800610pmid: N/A

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.