Polyethylene temperature dependence

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaUties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiUty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiUty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

Free mono- and multilayer films may be adhesive- or extmsion-bonded in the laminating process. The bonding adhesive may be water- or solvent-based. Alternatively, a temperature-dependent polymer-based adhesive without solvent may be heated and set by cooling. In extmsion lamination, a film of a thermoplastic such as polyethylene is extmded as a bond between the two flat materials, which are brought together between a chilled and backup roU. 

Boothroyd et al. [74] recently determined the temperature dependence of the Kuhn length for polyethylene with the aid of small-angle neutron scattering. In the temperature range between 100 and 200°C, dlnC /dT = - 1.1 x 10 3 K 1... 

In the temperature range between 400 and 550 K, NSE spectra on the same undiluted polyethylene melt were recorded. These data were analyzed with respect to the entanglement distance. The result for the temperature-dependent entanglement distance d(T) is shown in Fig. 30. An increase in the tube diameter from about 38 to 44 A with rising temperature is found. 

Fig. 30. Temperature dependence of the entanglement distance for polyethylene. > = 1 o O = 0.5. The dotted lines give a best fit for the data. The solid line represents the prediction by the scaling model of Graessley and Edwards (see text). (Reprinted with permission from [60]. Copyright 1993 American Chemical Society, Washington)...

Simulation programs for the ESR line shapes of peroxy radicals for specific models of dynamics have been developed for the study of oxidative degradation of polymers due to ionizing radiation [66]. The motional mechanism of the peroxy radicals, ROO, was deduced by simulation of the temperature dependence of the spectra, and a correlation between dynamics and reactivity has been established. In general, peroxy radicals at the chain ends are less stable and more reactive. This approach has been extended to protiated polymers, for instance polyethylene and polypropylene (PP) [67],... 

Booij, K. Hofmans, H.E. Fischer, C.V. van Weerlee, E.M. 2003, Temperature-dependent uptake rates of nonpolar organic compounds by semipermeable membrane devices and low-density polyethylene membranes.Ewiran. Sci. Technol. 37 361-366. 

The application of thermomorphic solvent systems as a new recycUng concept was investigated in various C - C bond-forming reactions. Therefore methods for a systematic choice of solvent combinations were developed. In addition to common organic solvents more unusual solvents Hke cycHc carbonates, pyrroUdones, polyethylene glycols and lactones were used in the investigations. The phase behaviour of the new solvent systems was determined by cloud titrations. From these experiments information about the temperature dependency and an appropriate composition for the reactions could be obtained. The results were used in the development of an expert system for the solvent selection. 

For polyethylene (PE) and PEP systematic temperature-dependent measurements in the Rouse regime were performed. Furthermore data on the temperature-dependent end-to-end chain distance (Rl) also exist. Table 3.2 displays... 

In an extension of this work, the reuse of the polymeric catalyst was addressed and several new PE-poly(alkene) glycol copolymers were prepared [68]. Commercially available oxidized polyethylene (CO2H terminated, both high and low molecular weight) was converted to the acid chloride and reacted with Jeffamine D or Jeffamine EDR, and subsequently converted to the tributylammonium bromide salt with butyl bromide. These new quaternary salts were shown to catalyze the nucleophihc substitution of 1,6-dibromohexane with sodium cyanide or sodium iodide. While none of the polymeric quaternary salts catalyzed the reaction as well as tetrabutylammonium bromide, the temperature-dependent solubility of the polymers allowed removal of the polymer by simple filtration. 

A similar continuity in the Tj s through the melting temperature was previously reported for linear polyethylene. (17) We have now investigated the temperature dependence of this quantity, for this polymer, in more detail and have also studied a low density (branched) polyethylene. The results for the poly-ethylenes are summarized in Fig. 8. The new data reported here substantiate the conclusion previously reached for linear polyethylene. A similar conclusion can now be reached for the baclc-bone carbons of low density (branched) polyethylene. The melting temperature for this particular sample, under the crystallization conditions studied, is less than 110°C. (33) Thus, the spin-lattice relaxation parameters for the bac)cbone carbons are the same for both the linear and branched polymers over the temperature range studied here. Changes that occur in Tq as the temperature is reduced below 0°C involve other considerations and will be discussed in detail elsewhere. (22)... 

D. Axelson As we have already pointed out, the correlation time is frequency-independent. The longest correlation time that we have measured is about 10" s. Whether the results correlate well with the glass temperature depends on the value one accepts for linear and branched polyethylene. Those values have been a controversial matter. 

Fig. 22 Images and data representing development and application of DLS on a chip a one iteration in the design of a microfluidic DLS fabricated from aluminum with the surface anodized black to reduce surface reflections b image of a microfluidic chip that integrates polymer synthesis with DLS. The machined channels have been covered by a Kapton sheet fixed with adhesive c data for temperature depended micelle formation of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic P85) at 2% by volume in water. (Derived from [106] with permission)...

Polyethylene is, depending on the molecular weight, a waxy or solid, crystalline substance. Following the above-mentioned procedure, a high molecular crystalline product with a melting range around 130 C is obtained. At room temperature it is insoluble in all solvents. At higher temperatures (100-150 °C) it can be dissolved in aliphatic and aromatic hydrocarbons.Viscosity measurements can be performed in xylene,tetralin or... 

Figure 30 Temperature dependence of the permeability (P) of polyethylene glycol molecules for A-isopropylacrylamide (NIPAAm) grafted films. Polyethylene glycol with four kinds of masses (1 x 10, 1x10, 2x10, 7x10" ) are contained in the solution.

Over 100 stationary phases of various types have been described in the literature for packed columns, which are slowly being abandoned. However, for bonded phase capillary columns the choice of stationary phase is limited because the generation of the film at the surface of the column requires a different principle than impregnation. Generally, two families of compounds are used to modify the polarity polysiloxanes and polyethylene (silicones) glycols. Very special phases such as cyclodextrins can be used for enantiomeric separations. Stationary phases can be used between a minimum temperature under which equilibrium is too slow to occur and a maximum temperature above which degradation of the polymer occurs. The maximum temperature depends on the film thickness and the nature of the polymer. 

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