Morphology and permeability in extruded polypropylene/ethylene vinyl‐alcohol copolymer blends

Abstract

ABSTRACTstudies of ~he morphology of extruded polyrner blend syst~ms have shawn that it is feasible to produce a laminar structure of an ethylene vinyl-alcohr-l copolymer (EVOH) dispersed phase in a po1yprapylene (PP) m~trix phase. The laminar structure forms in the core of the extrudate when a 5lit die 1s incorporated into the extrusion process.Morphological studies, including a study of morphology d~vel opment inside the die and studies of the effect of processing conditions on the morphology of the final product, :evealed that the laminar structure is a resul t of die design. Processing conditions influence main1y the shape and dimensions of the laminnr core region of the extrudate.Oxygen permeation tests have shown that the blend e:,hibits lower oxygen permeability than pure PP, when EVOH is incorporated as a dispersed phase into the system. Oxygen transmission rates obtained with a blend system can be as low as those obtained with a mUlti-layer coextrusion product, although only at h~gh EVOH concentrations. Comparison of experimental data with theoretical permeation predictions shows that, up to 20wt% EVOH, the reduction in oxygen transmission rate is on1y minor, and follows the prediction for a homogeneous system. At 25wt%, a considerable decrease in oxygen transmission rate is noticeable, and the tr'end for higher EVOH contents is towards the behavior of a multi-layer system .

Oxygen barrier property of polypropylene-polyether treated clay nanocomposite

“…The deviation of oxygen permeability increased with clay ratios, indirectly supported by the WAXS and TEM results. Lohfink et al suggested that the oxygen permeability of PP-g-MA was greater than pure PP [45], although it should be noted that 10% of PP-g-MA was present in their nanocomposites.…”

Laminar morphology development using hybrid EVOH-nylon blends

“…The morphology of the blends seems to be dependent mainly on the composition of EVOH and nylon 6 (L) in the E / NL hybrid dispersed phase. Many studies on the laminar morphology [9][10][11][12][13][14][15] have reported that the number and size of layers are largely dependent on the concentration of dispersed phase. Under the constant concentration of the hybrid dispersed phase (18.5 wt %), a larger portion of one component (EVOH or nylon 6 (L)) in the E / NL hybrid dispersed phase results in an increasing number of stacked pronounced layers of the component and a small number of short layers of the other component.…”

“…In particular, EVOH is having dispersed lamellae of impermeable polyrelatively brittle, expensive, and absorbs moismers. Many workers [9][10][11][12][13][14][15] have studied laminar ture. On the other hand, it is also well recognized morphology and barrier properties of blends, that nylon has good barrier properties against hywhere EVOH or nylon has been chosen as the drocarbon solvent and exhibits outstanding levels barrier layer.…”

Study of blends of nylon 6 with EVOH and carboxyl-modified EVOH and a preliminary approach to films for packaging applications

“…Literature reports have shown that, by a proper combination of chemical physical properties and technology of processing, it is possible to realize monolayer films made by polymer blends with a multilayer-type internal structure. [2][3][4] This can be achieved by stretching the dispersed phase during processing (film blowing) or by varying the geometry of the extrusion die so that it will assume a laminar structure inside the matrix polymer. In some cases, as reported for extruded polypropylene/ethylene-co-vinyl alcohol (PP/EVOH) blends, the oxygen permeability can approach those obtained with a multilayer coextruded film 3 Similar results were reported for polythe first and second heating runs, respectively; crystal-(ethylene terephthalate) blends.…”