Poly weight loss

Aliphatic—aromatic poly(amide—imides) based on N,1S7-bis(carboxyalkyl)-benzophenone-3,3, 4,4 -tetracarboxyhc diimides have shown a 10% weight loss at 400°C (14). 

Polyquinolines have also been obtained by a post-polymerization thermal treatment of poly(enamino nitriles) (93). The resulting polymers show excellent thermal stabiUty, with initial weight losses occurring between 500 and 600°C in air (tga) under nitrogen, initial weight loss occurs at about 600°C and there is a 20% weight loss up to 800°C. 

A measure of the heat resistance can be obtained by the weight loss at various temperatures. Table 18.12 gives details of the weight loss of three poly-pyromellitimides after various heating times at 325°C. 

The chemical name for such materials is poly(bisbenzimid-azobenzophenan-throlines) but they are better known as BBB materials. Such polymers have a Tg in excess of 450°C and show only a low weight loss after aging in air for several hundred hours at 370°C. Measurements using thermal gravimetric analysis indicate a good stability to over 600°C. The main interest in these materials is in the field of heat-resistant films and fibres. 

IX lists the results of some of these experiments, comparing the nitrile materials with polyethylene, the most widely used plastic container material, and poly (vinyl chloride), which is being used for a number of food packaging applications. Note that in all instances there is an order of magnitude difference between the Lopac container and the other two. For flavorants, which are usually present in very low concentrations, this dilute solution test is probably more significant than a standard permeability test which only measures weight losses of the pure ingredient. 

Convincing evidence for a surface erosion process is shown in Fig. 8, which shows the concomitant release of the incorporated marker, methylene blue, release of the anhydride excipient hydrolysis product, succinic acid, and total weight loss of the device. According to these data, the release of an incorporated drug from an anhydride-catalyzed erosion of poly (ortho esters) can be unambiguously described by a polymer surface erosion mechanism. 

Figure 5 Weight loss of lysine based poly (phosphoester urethanes) at 7 days in 0.1M pH 7.4 phosphate "buffer at 37°C.

Figure 4 Weight loss vs. temperature for poly( -carborane-siloxane)s in air.

Fig. 6. Comparison of the percentage average weight loss of Dutch Gouda cheeses treated with either a poly(HAMCL) latex coating (solid line, 12 cheeses in total) or a commercial cheese coating (dashed line, 6 cheeses) as a function of time...

It has been determined from X-ray diffraction measurements that polycarbonate containing Bisphenol AF moiety are all amorphous.6 The (Tg) of poly(carbonate)s increases with an increase in hexafluoroisopropylidene unit from 149°C for Bisphenol A poly(carbonate) (3) to 169°C for Bisphenol AF poly(carbonate) (2) (Table 9.3).6 Thermooxidative stability is also improved by the introduction of fluorine atoms into the isopropylidene units. The 10% weight-loss temperature (DT10) increases from 429 to 460°C and the residual weight (RW) at 500°C goes from 37 to 57% by perfluorination of the isopropylidene units. 

Thermooxidative stability of the fluorine-containing poly(ether ketone) (11) and poly(sulfide ketone) (13) from 15 is very high. The 5% weight-loss temperatures (DT5) are 391 and 436°C for poly(ether ketone) and poly(sulfide ketone) analogues having no fluorine atoms, whereas those of poly(ether ketone) (11) and poly(sulfide ketone) (13) are higher than 500°C. 

PVA films buried in soil were tested after 120 days and showed only very limited signs of biodegradation, and even field tests with PVA sheets buried for 2 years in different natural soil sites showed only limited (10%) weight loss. No traces of colonising microorganisms were detected on the incubated material. Degradable polymers like poly(hydroxy butyrate), PCL or starch are usually extensively... 

The most common synthetic biodegradable polymers for suture material and their corresponding weight loss in aqueous solution are listed in Table 3.10. Of these, poly(glycolic acid), PGA, poly(lactic acid), PLA, and copolymers of these two polyesters are the most widely used for resorbable sutme material. PGA is a tough. 

Amount of deposited material - The difference in weight loss between coated and untreated silica corresponds to the weight of the plasma-polymerized film deposited on the surface. For the plasma-treated silicas, decomposition of the coating starts at 265°C for poly acetylene, 200°C for polypyrrole, and 225°C for poly thiophene, and is complete at 600°C. Between 265 and 600°C, PA-silica shows 6 wt% weight loss, and PPy- and PTh-silicas show 4.5 wt% and 5 wt% loss, respectively. 

---