Polymer PMMA

These effects have been found by Creton et al. [79] who laminated sheets of incompatible polymers, PMMA and PPO, and studied the adhesion using a double cantilever beam test to evaluate fracture toughness Fc. For the original laminate Fc was only 2 J/m, but when interface reinforced with increasing amounts of a symmetrical P.M.M.A.-P.S. diblock copolymer of high degree of polymerisation (A > A e), the fracture toughness increased to around 170 J/m, and then fell to a steady value of 70 J/m (Fig. 9). 

Evaluation of molecular weights after ultrasonic scission of high molecular weight polymers (PMMA and PS) in the presence of a radical trap has been claimed to provide evidence of the termination mechanism.1,1 However, scission gives radicals as shown in Scheme 5.10. 

The polymer PMMA has been used to describe many aspects of steady burning rate theory. This is because it behaves so ideally. PMMA decomposes to its base monomer although it melts, its transition to the vaporized monomer is smooth its decomposition... 

In addition to traditional radical initiated addition polymerizations, cation and/or anion catalyzed addition polymerizations are of great commercial importance, since PE, PP and PS are most frequently produced using this type of polymerization technique (Table 5). In addition to the vinyl monomers, vinyli-dene monomers, in which neither R nor R is hydrogen, can form commercially important polymers. PMMA is a typical example of this type of thermoplastics. 

On the basis of the aforementioned considerations, Peppas et al. carried out an evaluation of the interaction parameters which are operative in ternary systems consisting of water, protein (BSA, y-Ig and FGN), and polymers (PMMA, PE, PVC, PS, PVA, PVDF, PDMS and PEO). Their results are cited, with some simplification, in Tables 3, 4 and 5. 

Furthermore, the number of hydrogen atoms in a unit volume of 6FDA/TFDB is much smaller than for transparent polymers PMMA, PS, and PC, and these hydrogen atoms are only bonded to benzene rings. 

For decades such adsorption had been assumed to involve dipole interactions and interacting sites were termed "polar." It is quite clear in the above studies that dipoles in the polymers and in the solid surfaces do not contribute measurably to adsorption. Even from carbon tetrachloride, the solvent most favorable to adsorption, the amount of basic polymer (PMMA) that adsorbed onto basic calcium carbonate was only 2.5% of the amount that adsorbed on the same area of silica surface. Similarly, the amount of acidic polymer (CPVC) that adsorbed onto the acidic silica from any of the six solvents was less than 0.2% of the amount that adsorbed from carbon tetrachloride or dichloromethane onto the same area of basic calcium carbonate. It is concluded that adsorption of organic acids or bases from neutral organic solvents onto inorganic solids is governed entirely by acid-base interactions and is quite independent of dipole phenomena. It is therefore proposed that heats of adsorption are actually enthalpies of acid-base interaction and should therefore be subject to the Drago correlation ... 

Figure 14.24 Templation of a covalent polymer (PMMA) by a supramolecular metallogel of iron(III) benzene tricarboxylate (BTC) (reproduced by permission of The Royal Society of Chemistry).

Fig. 18 TEM images of polymer sheets a PE-PMMA purified polymer (PMMA contents 23wt%), b homo-PE/homo-PMMA blended polymer (homo-PE/homo-PMMA = 75/25 wt ratio)...

MALDI spectra of a monoclonal antibody (above) and of a polymer PMMA 7100 (below). Reproduced (modified) from Hillenkamp F.H. and Kras M., Meth. Enzymol., 193, 280-295, 1990 and from Finnigan MAT documentation, with permission. 

Binary solutions of CTAATFA-CH2Q2 (60 40 vA ), PET/solvent and PMMA/solvent were prepared and mixed in various ratios to obtain ternary solutions. After a lapsed time of 2 weeks, the solutions were observed visually and microscopically. The results are summarized in Table X. In agreement with Rory s prediction, the anisotropic phase is rich in CTA and the isotropic phase rich in PMMA or PET. However, at least within experimental error and in the timeframe of these experiments, the flexible polymer (PMMA or PET) was not completely excluded from the anisotrq>ic phase, contrary to results reported for other combinations of a flexible and a rigid polymer (20-22). 

As discussed above, the critical concentration of CTA is lowered in the presence of a flexible polymer (PMMA or PET). However, when the ternary mixtures of CELLOH were prepared (23), die very low critical concentration of CELLOH in TFA-CH2CI21 not been observed (8) and presently no results are available for a ternary mixture containing 6% cellulose. 

Fig. 19. Craze stress cr as a function of temperature T in different polymers PMMA (x...

Glassy polymers, PMMA and PS, are suitable for many applications, but they are brittle when subjected to impact loads. The same things happens with thermoset polymers such as epoxy or phenolic resins. To solve this problem, impact-resistant polymers have been developed that basically consist of a matrix of the brittle polymer in which a second elastomeric... 

In the present section it will be shown that microhardness can conveniently detect the glass transition temperature Tg by following // as a function of temperature. We will illustrate the temperature dependence of hardness in case of two amorphous polymers - PMMA and poly(vinyl acetate) (PVAc) - and two semicrystalline... 

It should he noted that the first pair of polymers (PMMA and PVAc) are not capable of crystallizing and, therefore, are always present in the amorphous state, which is not the case with the second pair. PET and PEEK are high-melting semicrystalline polymers distinguished by relatively low crystallization rates and... 

Figure 3.5 shows the temperature variation of H for the four above mentioned polymers, namely PMMA, PVAc, PET and PEEK. In the case of the two amorphous polymers (PMMA and PVAc) H decreases with T and the Tg value can he clearly identified with a hend in the 7/ vs T plot. However, the two semicrystalline materials quenched into the amorphous state (PET and PEEK) show an apparent maximum just before the glass transition takes place. Also, in the case of PET tested immediately after quenching it is observed that H increases with T above room temperature. These phenomena will be discussed in Section 3.3 in the light of the physical ageing undergone by the above polymers. It is seen that H follows an exponential decrease as a function of T given by (see eq. (2.5))... 

Figure 4. Diagram of the three chromophores DPNA, DMANS, DPDNDAB, and the polymer PMMA...

White and coworkers [316] reported an influence of alkali halides on the thermal decomposition of polymers (PMMA and PHEMA). In case of Kapton... 

Fig. 2 X-ray absorption spectra calculated for the polymers PMMA and PTFE. PMMA is mainly used in deep x-ray lithography, namely the LIGA process, while PTFE is mainly used in SR direct photoetching, namely the TIEGA process...

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