Coextruded samples

Other authors published interesting results on the radius of gyration for coextruded samples polystyrene of relatively high mass (M, p = M = 6 10 ) was used. A strip of polystyrene was inserted into a cylindrical billet of polyethylene, extruded at T = 127 °C at a pressure of 280 kg/cm and with a deformation rate of 0.1-0.2 cm/ mn. The deformation ratio, measured from marks on the sample, attained very large values k = 3, 4, 5, and 10. It is difficult to give a corresponding value of t for this deformation, but an indication is that the recovering was tested as total. The results, obtained only from a comparison to the affine behaviour, are presented in Sect. 5. 

Another product, defatted com germ flour was coextruded at 150 or 170 °C with 5% milk protein to produce a puffed nutrient snack (Peri et al., 1983). The addition of fhe milk profein af fhe lower temperature improved the organoleptic characteristics of fhe exfrudafes but adversely affected the product expansion and consistency of fhe samples at the higher temperature. 

Ultraviolet absorbers were among the first organic stabilizers used. They are colorless compounds that strongly, but selectively absorb ultraviolet radiation and harmlessly dissipate it as heat so that it does not lead to photosensitization. They are also characterized by their very good stability to the absorbed radiation. However, based on the UV absorption mechanism alone, they can only provide limited protection to surface layers and thin samples, for example fibers and films. In accordance with the Beer-Lambert absorption law, the amount of radiation reaching any particular layer diminishes exponentially with the distance from the exposed surface. Thus, the effectiveness of protection via screening of the actinic radiation from the polymer by the UV absorber increases with sample thickness. Protection by UV absorbers is most effective when the additive is concentrated on the surface, such as when it is incorporated in a thin film coextruded over the polymer [75]. 

The effect of draw technique and conditions, and sample Mv on the drawability of UHMW-PP SGC mats has been studied. It was found that these mats also was most deformable by two-stage drawing, as was observed for UHMW-PE SGC mats. Furthermore, the initial EDR also had a major effect on the drawability for the second-stage tensile drawing. Thus, the SGC mats of PP with different Mv s were initially coextruded at 130°C and a low EDR of 6, followed by tensile drawing at optimum temperatures of 150-165°C, depending on the sample Mv. The maximum achievable DR increased slightly with Mv, from 60 for a Mv of 3 x 10 to 80 for a Mv of 36 x 10, Such an increase in drawability with Mv is not so remarkable as found in PE. 

The effect of two -nucleating agents, calcium salt of pimelic acid and quinacridonequinone, on the fractionated crystallization of PP microdroplets was studied. The microdroplets were produced by layer breakup on heating ultrathin films of PP/PS coextruded nanolayer films. Microdroplets produced from un-nucleated multilayered films exhibited fractionated crystallization at 110°, 90°, 60° and 40°C. PP microdroplets nucleated with Ca-Pim exhibited the P-form at 120°C in 200 nm samples while no P-peak was observed in other layer thicknesses. PP microdroplets nucleated with 0.01 wt% QQ and above showed crystallization peak for p-form of PP at 120°C for all layer thicknesses. 

Coextrudate materials were chosen based on the purpose of the sample. The initial coextrasion samples were intended to be new nanocomposite materials with good layer adhesion. These samples had neat PP in evsy... 

For samples that underwent mechanical and thermal testing, the PP nanocomposite layers were separated Ifom the coextrudate layer. Samples had the outermost 1.5 mm of each edge removed and the sample was gently flexed to initiate delamination of the layers. The partially delaminated layers were then slowly peeled apart, making sure to keep track of the layer number of each. Individual layers were soaked in toluene solvent and then air dried to ensure removal of any residual PS. 

Figure 3. TEM micrograph of 20 layer coextrudate made from MB15. An Af 33 was measured for this sample.

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