Forms from the Melt

Crystalline Fbrms Cast from Solution Spherulitic Morphology 

When films of PS-PEO block copolymers were cast from solution, wide variations in texture were reported by Crystal et al. (1969, 1970). In these 

In each case, the basic crystalline subunit is the folded-chain lamella, with a thickness of about 180 A. However, as the content of PS increases. 

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A suspension of crystals formed from the melt may be contacted by weU-mixed mother Hquor or the crystals may be moved countercurrently to hquor flow ia a vertical or horizontal column. In column crystallizers, crystals are moved ia a specific direction by gravity or rotating blades. The crystals are melted by the addition of heat when they reach a designated end of the crystallizer a portion of the melt is removed as product and the remainder is returned to the system to flow countercurrently to and to wash the product crystals. 

The p-form which crystallises more slowly than the a-form from the melt. 

PE crystallizes into the orthorhombic form from the melt, which results in folded chain crystals (FCCs) [14,15]. In this case, the critical nucleus should... 

One of the authors (MH) showed that the formation of an ECSC or an FCC is related to the order of the crystalline phase [20,33,34], that is, an ECSC and an FCC are formed from the melt into a disordered hexagonal and an ordered orthorhombic phase, respectively. It is natural to consider that the surface diffusion process should be controlled by the order of the crystalline phase. This is the reason why H shows a significant difference between ECSC and FCC. 

When the fold type nucleus is formed from the melt, the chain conformation within the melt should be a random coiled one. Therefore, the chain conformation within the melt of ECSCs should be a random coiled one. The crucial difference between the melts of ECSCs and FCCs at small At is only that of ve. 

There are three situations that appear to be relevant here. First, we may think of a solid polymer formed from the melt second, the much more compliant elastomers that initially come to mind when we think of rubber elasticity and third, polymer gels formed in polymer solutions. In each case the details of the physical chemistry of the macromolecules is crucial to the understanding of the structure that is formed. In this section we will concentrate on organic macromolecules because the rheology of these molecular systems is often the reason for their use. 

The so ealled a phase of the fatty alcohols is a thermotropic type smectic B liquid crystal with a hexagonal arrangement of the moleeules within the double layers. It is initially formed from the melt during the manufaeturing proeess and normally transformed into a erystalline modifleation on eooling. However, the erystallization of the gel matrix ean be avoided if the a phase ean be kept stable as it eools to room temperature. This ean be achieved by eombining appropriate surfaetants, such as myristyl or lauryl alcohol and cholesterol, a mixture of whieh forms a lamellar liquid... 

The shape of moving boundary of crystals was different if the composition of melt mixture was changed. When pure benzene was compressed, the shape of moving boundcu y of crystal was roundish. The fringe shape made 1 90.0 mole percent benzene was slightly sharp, and the crystals formed from the melt 80.0 and 70.0 mole percent benzene had sharper moving boundary. But the details of these difference are not clear and future studies are expected. 

In addition to the observations on the three diagnostic liquids required to establish the reproducibility of films formed from the melt, contact angle (6) measurements (Table III, last column) were made on... 

Description Liquid LC is continuously polymerized in a VK-tube (1) in the presence of water, stabilizer and modifying additives at elevated temperatures. The polymerization process has proven to be very reliable, easy to operate and economical. Prepolymerization is available to reduce reactor volume for large capacity units. The polycaproamide chips are formed from the melt using strand cutters and are conveyed to the extraction column (2). 

In both, layer and suspension crystallization solid material forms from the melt starting with a nucleus through which a solid/liquid interface is created. As crystallization proceeds the mass of solidified substance steadily increases which causes the interface to move. The impurity components remaining in the melt thereby enrich in front of the solid/liquid interface, forming a concentration boundary layer. The concentration profile in this boundary layer changes as the interface advances which is in literature referred to as moving boundary problem. ... 

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