Effect of processing parameters on the morphology development during extrusion of polyethylene tape: an in-line Small-Angle X-ray Scattering (SAXS) study

The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness (~50 Å) and bulk crystallinity (~20%), were low for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth

Particulate Fillers in Thermoplastics

The characteristics of particulate filled thermoplastics are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local micromechanical deformation processes determining the macroscopic properties of the composites

Nylon Refrigerant Tubing

Air Conditioning and Refrigeration Center Project 1

Interactions at the PA-6/PA-66 Interface

Refrigerant tubing used in some mobile air conditioning systems has a nylon core, often consisting of nylon 6, nylon 66, or a copolymer thereof. A blend of the homopolymers would be more economical than the copolymer. This paper deals with the structural stability of such blends during processing. The crystallization and melting behavior of laminates and solution cast blends of nylon 6 and 66 were examined. Although they do not co-crystallize readily, their at least partial miscibility in the melt and possible coincorporation as crystal defects causes reductions of the melting points and heats of crystallization and fusion of both polymers. The crystallization temperature of the nylon 6, however, increases with increasing nylon 66 content, up to ca. 60% nylon 66, a feature attributed to nucleation of the 6 by the 66.Air Conditioning and Refrigeration Center Project 1

Melting and Recrystallization of PA-6/PA-66 Blends

The morphology of a number of polyamides (P A) of current and potential use for mobile air conditioning and refrigerant tubing, namely PA-6, PA-66, PA-6/PA-66 blends and PA-6/PA-66 copolymers, as prepared from the melt and from HCOOH solution and the effect of annealing thereof has been examined. In tpe blends the P A -6 crystallizes within the P A -66 spherulites, the P A -66 crystallizing first in a loose lamellar framework. The copolymers also crystallize as large spherulites. When prepared from HCOOH solution at 25??C (77??F) the PA-66 containing samples show a large exothermic peak before the sample melting peak is observed by DSC. This exothermic peak, which cannot be fully explained by either previously known observations, P A recrystallization and/or the morphology changes we describe here, is not seen for PA-6 or for PA-66 prepared from HCOOH solution at 100??C (212??F).Air Conditioning and Refrigeration Center Project 1

Epitaxial crystallization of linear polyethylene in blends with isotactic polypropylene

The structure and morphology of extrusion-oriented ribbons of polypropylene/polyethylene blends is described. The blends with 20%, 30%, and 40% of oriented isotactic polypropylene fibrils show homo- and heteroepitaxial structures. Partial mutual solubility of the blend components influenced the melting and crystallization behavior.European Social Fund (ESF); National budget of Czech Republic, within the framework of project Advanced Theoretical and Experimental Studies of Polymer Systems [CZ.1.07/2.3.00/20.0104