Polyethylene interfacial free energy

The qualitative thermodynamic explanation of the shielding effect produced by the bound neutral water-soluble polymers was summarized by Andrade et al. [2] who studied the interaction of blood with polyethylene oxide (PEO) attached to the surfaces of solids. According to their concept, one possible component of the passivity may be the low interfacial free energy (ysl) of water-soluble polymers and their gels. As estimated by Matsunaga and Ikada [3], it is 3.7 and 3.1 mJ/m2 for cellulose and polyvinylalcohol whereas 52.6 and 41.9 mJ/m2 for polyethylene and Nylon 11, respectively. Ikada et al. [4] also found that adsorption of serum albumin increases dramatically with the increase of interfacial free energy of the polymer contacting the protein solution. 

In dishwashing, one must consider soil and surfactant adsorption to both polar and nonpolar surfaces. Metals (aluminum, stainless steel, carbon steel, cast iron, silver, and tin), siliceous surfaces (china, glass, and pottery), and organics (polyethylene, polypropylene, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and wood) present a wide variety of surface characteristics. They span the range of high interfacial free energy (metals and many ceramics) to low interfacial free energy (hydrocarbon polymers) surfaces [27,28],... 

We cite here just a few of the large number of examples that exist in the literature which show essentially the same result, t These considerations apply to a lamellar crystallite of very large, or in effect unlimited, lateral dimensions. However, these concerns do not apply to a nucleus of critical size. Estimates of the interfacial free energies involved indicate that for polyethylene, for example, the nucleus will consist of from 20 to 100 sequences in the undercooling range in which crystallization is usually conducted. 

There is only a slight variation of the listed values with molecular weight. In calculating AG for polyethylene, the equlibrium value, should be used for M > 20000. Then, except for the lowest molecular weights, the values of cr cTeii determined from the droplet experiments are independent of chain length. The interfacial free energy product obtained for isotactic poly(propylene) is greater than that of linear polyethylene. 

In a different approach, the results from droplet experiments that involved both the -alkanes and linear polyethylene were combined.(226) The a value of 9.6 erg cm obtained for n-octadecane, assuming a spherical nucleus, was identified with CTun, the lateral or side interfacial free energy of polyethylene. A value of cTen of 168 ergcm was then obtained by this procedure. However, there is a serious question as to whether the identification between o and cTun is valid. Moreover, as was pointed out earlier the results for octadecane are anomalous. The value of o increases monotonically for n >25, and extrapolates to cr 20-23 erg cm for high molecular weight polyethylene. There is thus the additional problem of what value to use for a in following this procedure. 

The conclusion that the value of (Te is independent of whether or not lamellar crystalUtes are formed is similar to the conclusion reached in analyzing both the growth and overall crystallization rates of high molecular weight n-alkanes (see Sects. 9.14.1 and 9.14.2). In these instances, as well as with low molecular weight fractions of linear polyethylene, the same interfacial free energy for nucleation is involved, irrespective of whether extended or folded chain crystaUites are formed. It becomes clear that it is not necessary to postulate that a nucleus is composed of regular folded chains in order to form lamellar-Uke crystaUites. 

An alternative possibility arises from considerations related to the development of crystalline structure in polyethylene [22], The main feature of this structure is the periodic folding of the polymer chains in the crystal. Theoretically this is explained within the context of the kinetics of crystal nucleation and growth from solution. According to Cormia, Price, and Turnbull [22], the fold-surface energy in polyethylene crystals is comparable to the end-interfacial energy of rodshaped nuclei. These surface free energies are of the order of 10 to... 

Ethylene-vinyl acetate copolymer, terpene-phenol resins, polyethylene oxide, PMMA and some of their blends were solution cast on basic (aluminium oxide) and acidic (hydroxylated glass) substrates. Fourier transform infrared reflection absorption spectroscopy (IRRAS) was used to determine both the nature and the free energy of interfacial adduct formation in the polymer/metal systems. A correlation between IRRAS and adhesive strength may be used to predict both the acid-base work of adhesion and the density of interfacial interacting sites. 14 refs. 

It is not always realized that hydrophobic interactions can quite readily take place between one hydrophobic and one hydrophilic molecule or particle, immersed in water, see Eq. 5.50. This is demonstrated in Table 8.2. Here the LW, the AB and the total interfacial (IF) free energies are shown of the interaction of polyethylene (PEO, which is one of the most hydrophilic materials known) with hydrophobic, mildly hydrophobic and hydrophilic entities. It clearly shows that, in water, PEO will bind to the more hydrophilic substrata (i.e., Teflon, octane, talc). PEO will not bind (in water) to the only slightly hydrophobic smectite, hectorite, and it is even more strongly repelled (on a macroscopic scale) by the very hydrophilic surfaces of muscovite and glass. It should be noted that these considerations only apply to interactions on a macroscopic level. Even when a macroscopic repulsion exists on a macro-... 

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