Absorption of polymers

Infrared Spectra of Grafted Bamboo. It has been demonstrated that the occurrence of graft copolymerization of methyl methacrylate onto bamboo can be accertained by the presence of characteristic absorptions of polymer branches in the infrared spectrum (17-19), in addition to the weight increased in bamboo samples. In this study, similar procedures were conducted for the grafting of acrylonitrile. The formation of graft copolymer could easily be detected by the... 

A useful initial concentration for solution viscometry of most synthetic polymers is about 1 g/l(X) cm solvent. High-molecular-weight species may require lower concentrations to produce a linear plot of c (r /f o — 1) against c (Fig. 3-7), which does not curve away from the c axis at the high concentrations. At very low concentrations, such plots may also curve upward. This effect is thought to be due to absorption of polymer on the capillary walls and can be eliminated by avoiding such high dilutions. 

In conclusion, then, the available evidence concerning the structure of dimeric units suggests that many H bonding compounds form cyclic dimers (carboxylic acids, lactams, alcohols, phenols, and some steri-cally hindered amides) but that some form open dimers (most amides). This conclusion is reassuring to the many quantitative studies which have been based upon the tacit assumption that the v, absorption of monomeric species is not coincident with terminal O—H absorption of polymers. 

B. Strehmel, unpublished results about Two-Photon Absorption of Polymers Bearing Distyrylbenzene and Aliphatic Units in the Main Chain, University of Potsdam, 2001. 

Fig. 23. Chemical structures and measured two-photon absorptivities of polymer samples based on a PPV backbone...

According to the rule of ultra-violet absorbers selection the most effective stabilizers must absorb not only in the field of absorption of polymer itself, but in the field of its luminescence [24] that is the condition for realization of suppression mechanism of polymer excited state. 

A noted phenomenon is caused by water absorption of polymer concrete (Figure 1.8). The penetration of water into polymer concrete leads to a softening of its structure and consequently to loss of strength and an almost threefold increase in the deformability of the material. 

Water penetration of the test samples occurs in several ways. Samples that are placed in mediums with humidity of 50%-60% and 85%-95% swell gradually and are not stabilized in weight within one year. The samples stored in water are saturated with it in half a year and their subsequent storage in these conditions does not lead to increase in weight. By this time, the stress-strain parameters in compression are stabilized. Note that these parameters continue to decrease for the samples in 50%-60% and 85%-95% humidity because water absorption of polymer concrete continues. 

Morye S.S., Hine P.J., Duckett R.A., Carr D.J.. Ward I.M (2000), ModeUing of the energy absorption of polymer composites upon ballistic impact. Compos Sci Technol, VoL 60, pp.2631-2642... 

Table 5.2 Detergent resistance, hydrolytic stabOity and water absorption of polymers ...

Tawe 44ft Selecting Water Absorption of Polymers... 

Transport in the reverse direction, i.e. intestinal absorption of polymers after oral administration, has been demonstrated to depend on the molecular weight Large molecules are mostly unable to undergo intestinal absorption In a study with I-labelled PVP, its absorption was found to be independent of the amount of I-PVP infused, suggesting the existence of a readily saturated absorption mechanism The presence of a mucus layer on the luminal side of the epithelial cells may contribute to a selective exclusion of macromolecules (see below)... 

The parenteral route represents the only efficient entry of a polymer into the body. This can be accomplished, e.g. by intraperitoneal, subcutaneous, intramuscular or intravascular injection of a polymer solution. However, these ways are by no means equivalent. The absorption of polymers from the cavities, such as the peritoneal or pleural, is hindered by the serose, lining the inner surface of cavities. Therefore, especially large molecules may remain there for several days The absorption is slow and takes place mainly in the lymphatic capillaries. Therefore, a rapid increase of the polymer concentration is observed in the lymphatic system, particularly in the regional lymph nodes while an increase in the concentration in the central compartment and consequently rapid distribution throughout the body is protracted and delayed i59> Owing to this behavior, which is quite different from the absorption of small molecules, a lowering in the systemic toxicity and excretion rate of basic antibiotics bound to the polyanions was observed... 

Tang (134) studied the effect of the interaction between carbon black and the polymer on electrical behavior. The absorption of polymer on the carbon black surface may be physical or chemical. The latter is caused by free-radical reaction between the polymer and carbon black, and it can occur during radiation or the preparation of the composite. In carbon-black-lilled high density polyethylene, the cross-linked network of the pol5uner restricts the freedom of movement of carbon black. The free-radical reaction enhances the binding force between the polymer and carbon black. 

---