Melt-crystallised films

Two-dimensional FTIR spectroscopy was used to study the N-H stretching and amide I/amide II region of melt-crystallised nylon 11 thin films on Teflon substrates. The samples were dynamic mechanically oscillated at room temp, at a frequency of 11 Hz. A two-dimensional correlation analysis on the dynamic spectra indicated that the N-H stretching region split into two peaks. Analysis... 

A biaxially drawn film is shown in Figure 4.53. It has a 42% crystallinity and, again, is different from the melt-crystallised sample. Its glass transition... 

Figure 4.53. Apparent heat capacity of drawn PET film by quasi-isothermal MTDSC, compared to data on semicrystalline, melt-crystallised PET as shown in Figure 4.50 [63].

In crystallization experiments where one wants to study a short-lasting transient effect, with statistically relevant data, it is sometimes possible to translate the problem from the time domain to a spatial domain. In crystallization experiments this can be done very elegantly by using a scaled-down version of an industrial melt extruder. With appropriate extrusion rates one can obtain an unoriented melt just after the molten pol mier has been extruded from the extrusion die. Further down the extruded film the poljmier solidifies and crystallises. When mounted on an elevation platform it is now possible to choose the distance after the extrusion die where the x-ray beam intercepts the crystallising film. (Fig. 19). The distance from the die can be translated into a crystallization time. This method... 

A melt-crystallisation method had been employed by Ohkoshi and coworkers to prepare blends of atacticP(3HB) with PLA. The atacticP(3HB) [ataP(3HB)] is synthesized by the polymerisation of racemic p-butyrolactone and is a completely amorphous polymer. The solvent-casted film of ataP(3HB)/PLA blends were inserted between two Teflon sheets (0.2 mm)... 

Orientation. Most articles made of HDPE, including film, fiber, pipes, and injection-molded articles, exhibit some degree of molecular and crystal orientation (21). In some cases, orientation develops spontaneously for example, during melt flow into a mold and its subsequent crystallisation. When blown HDPE film and fiber are manufactured, orientation can be introduced dehberately by stretching. 

A further approach is used by Bayer with their polyesteramide BAK resins. A film grade, with mechanical and thermal properties similar to those of polyethylene is marketed as BAK 1095. Based on caprolactam, adipic acid and butane diol it may be considered as a nylon 6-co-polyester. An injection moulding grade, BAK 2195, with a higher melting point and faster crystallisation is referred to as a nylon 66-co-polyester and thus presumably based on hexamethylene diamine, adipic acid and butane diol. 

The heat flow into (endothermic) or out (exothermic) of a sample as a function of temperature and time is measured using the technique of DSC. In particular, it is used to study and determine the temperature of thermal transitions. For polymers, these include Tg, the glass transition temperature, Tc, the (exothermic) temperature of crystallisation for polymers that can crystallise, and Tm, the (endothermic) melting temperature. A DSC measurement requires only a small amount of sample 2-20 mg of a film, powder, fibre or liquid samples can be analysed in a DSC pan. 

Starch can be destructured in the presence of more hydrophobic polymers such as aliphatic polyesters. Aliphatic polyesters with low melting points are difficult to process by conventional techniques such as film blowing and blow moulding. Films such as polycaprolactones (PCL) are tacky as extruded and have a low melt strength (over 130 °C). Also, the slow crystallisation of the polymer causes the properties to change with time. Blending starch with aliphatic polyesters improves processability and biodegradability. 

Iron dicarbide, FeC2.—A substance of this composition has been prepared 1 by allowing melts of iron, containing from 6 to 10 per cent, of carbon, to cool. Crystallisation begins at 2380° to 2000° C., a pale yellow carbide separating out, with a silvery reflex. It is slowly attacked by nitric acid, and, when immersed in dilute copper sulphate solution, becomes coated with a film of metallic copper. 

Most of the poly(etherketone-carborane)s so far prepared are non-crystalline and thus readily soluble in organic solvents such as chloroform or NMP, from which tough, coherent films and coatings can be obtained by solvent evaporation. However, we have found two polymers of this type, both derivatives of p-carborane, which display significant levels of crystallinity.8 Thus, the semi-aliphatic polymer derived from bis(4-phenoxyphenyl)-p-carborane (3) and hexadecanedioic acid (6) undergoes solvent-induced crystallisation on contact with NMP, and then shows a crystal melting point of 122 °C. 

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