Molecular weight affected

Electrical Properties. Erom a chemical standpoint, HDPE is a saturated aUphatic hydrocarbon and hence a good insulator. Its electrical characteristics are given in Table 1. Because polymer density and molecular weight affect electrical properties only slightly, HDPE is widely used for wire and cable insulation. 

The correction to the coefficient of in the dynamic dilution (cubic) term in the potential (compare Eq. 22 for the pure star case) arises from the way the difference in arm molecular weights affects the fraction of unrelaxed arm at the same timescale. 

Crystallinity and molecular weight affect polymer degradability and consequently erosion-based release Hydrophobic drugs typically have slower release rates Increased interactions may lead to slower release High drug loading may cause increased release rates due to channeling effects... 

How does one use osmotic pressure measurements to determine the molecular weight of a solute How does polydispersity in molecular weight affect such a measurment ... 

The application of stress relaxation is shown in Figure 3. The relaxation modulus (G) is determined after a step strain as a function of time. A step strain is applied to the sample causing a stress. The modulus is measured as the stress relaxes. The stress relaxation modulus shows how molecular weight affects the relaxation process as a function of time as depicted in Figure 4. 

Godbey, W.T., Wu, K.K. and Mikos, A.G. (1999a) Size matters Molecular weight affects the efficiency of poly (ethylenimine) as a gene delivery vehicle. J. Biomed. Mater. Res., 45, 268-275. 

Not only do the chemical structure and the molecular weight affect the processability but also the method of synthesis, in particular the imidation step. Thermally imidized polyimides are always less tractable than solution imidized polyimides. That is because thermally imidized polyimides can undergo cross-linking, and because thermal treatment (about 300 °C) favour chains packing and provide higher molecular order than that achievable by solution imidation. Therefore, solution imidation is always preferable when thermoplastic polyimides are to be developed. 

Molecular weight affects mainly the viscosity, so that, for some applications, such as adhesives that should be applied at relatively low temperatures, control of the molecular weight must be applied in the synthesis step [69,154]. Controlled molecular weight polymers can be prepared by upsetting the stoichiometry... 

Molecular weight affects mainly the a relaxation. Although the temperature of the a peak is often taken as a value for the glass transition temperature, Tg, the two temperatures are not equivalent because the first is strongly dependent on frequency. 

This determines molecular weight. Changes in molecular weight affect solution viscosity. Therefore, the product DP is commonly specified by the viscosity of a water solution as low, medium, or high. 

Besides the membrane thickness, the copolymer molecular weight affects also the lateral mobility of polymer chains within the membrane. Using fluorescence recovery after photobleaching (FRAP), Lee et al. [131] discovered that entanglements are responsible for the reduced mobility of copolymers with sufficiently high MW. 

If, therefore, the deviations are real, the question arises what property of the gas, other than its molecular weight, affects the chemical constant as Simon argues, there might be forces of cohesion which are still unknown. 

Figure 3.24 How crystallinity and molecular weight affect flex life (nonstandard test, 45 cycles per minute, 180-degree bend).i >...

In the two-phase model, the mass-transfer parameter needs to be determined using actual polymerization reactor data because the specific interfacial area is strongly dependent upon the geometry of the reactor internals. Moreover, the formation of bubbles of volatile species contributes to the total vapor-liquid contact area, and the liquid holdup on a rotating disk can change with the melt viscosity or polymer molecular weight, affecting the mass-transfer coefficient. 

The molecular weight and molecular weight distribution of polymers affects the volume fraction of chain ends and hence the free volnme of the polymer and, consequently, determines the chain mobility and crystallisation. It also determines the number of acidic end gronps that can participate in hydrolysis and their possible catalytic effect. Overall, the molecular weight affects both the chemical and physical properties of a polymer." ... 

This method was used to make microspheres of p(CPP-SA) 20 80 and 50 50 and copolymer of bis(p-carboxyphenoxy)propane, and dodecanedioic acid [p(CPP-DD)] 20 80 and 50 50 (Mathiowitz et al., 1988, 1990a,b ). Molecular weight affected the ability to make good, reproducible microspheres, with low-molecular-weight polymers being easier to process. Cross-sections of the microspheres revealed a porous stracture with increased density toward the external surface of the sphere. These microspheres lost their physical integrity during erosion studies and occasionally left empty shells. CrystaUine polymers, such as p(SA) did not produce smooth microspheres, while, amorphous polymers, such as p(CPP-SA) 50 50 produced microspheres with smooth external surfaces. 

HDPE is a very good insulator and is therefore widely used for wire and cable encapsulation. Polymer density and molecular weight affect electrical properties very little. HDPE is only slightly permeable to organic compoimds, both in liquid and gas phases. Permeability to water and inorganic gases is also low. 

Polyol (soft segment) molecular weight affects the modulus, E, of an elastomer. The theory of rubber elasticity predicts that Young s modulus of an elastomer is inversely proportional to the molecular weight of network chains, M. ... 

Molecular weight affects have been recognized in a number of experiments... 

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