Resilience poly

Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. 

The alcohol swells the poly (ethyl methacrylate) beads, rapidly promoting diffusion of the plasticizer into the polymer. As a result of the polymer-chain entanglement, a gel is formed. The conditioner is applied to the denture and provides a cushioning effect alcohol and plasticizer are slowly leached out, and the material becomes rigid. To ensure resiliency, the conditioner must be replaced after a few days. Some materials exhibit high flow over a short period compared with others with low initial flow the latter remain active longer. 

About 1.5 billion pounds of rxv-l, 4-poly(l, 3-butadiene) were produced in the United States in 2001. This polymer has a lower Tg and, therefore, higher resilience hut poorer tear resistance and tensile strength than does natural ruhher. For this reason, cis-... 

Because of its chemical inertness, no direct way of curing poly(thiocarbonyl fluoride) has been found. However, creep has been reduced and strength at elevated temperatures improved by milling into the polymer a free-radical generator, such as dicumyl peroxide or azobisisobutyronitrile, and a free-radical acceptor, such as N,N -m-phenylenebismaleimide or triacryloylhexahydro-s-triazine, and curing with heat and pressure (65). A better method is to mill in divinylbenzene and a small amount of benzoyl peroxide and cure with heat and pressure (66). The divinylbenzene forms a crosslinked matrix that mechanically traps poly(thio-carbonyl fluoride) molecules. Since the elastomer is in effect filled with poly(di-vinyl benzene), the final composition is less resilient than untreated poly(thio-carbonyl fluoride). 

And so we arrive at the basis for the strength of many polymers, especially plastics—molecular entanglement Picture hitting a glass windowpane with a hammer. The same blow to an equivalently shaped piece of Lexan (polycarbonate) or Ludte poly[methyl methacrylate]), both transparent plastics, does not break the polymer. In fact, the plastic glass is somewhat resilient, causing the hammer to bounce off of it. 

Examples of copolymers with practical use between two different carbonates are poly[2,2-propanebis(4-phenyl)carbonate]-Woc/c-poly[2,2-propanebis[4-(2,6-dimethylphenyl)]carbonate], poly [1,1-cyclohexane bis(4-phenyl)carbonate]-co-[2,2-propane bis(4-phenyl)carbonate], and poly [1,1-dichloroethylene bis(4-phenyl)carbonate]-co-[2,2-propane bis(4-phenyl)carbonate]. Examples of copolymers between a carbonate and an ester are poly[4,4 -(1-methylethylidene)bis[phenol]-co-1,3-benzenedicarboxylic acid-co-carbonic acid], poly[4,4 -(1-methylethylidene)bis[phenol]-co-1,4-benzenedicarboxylic acid-co-carbonic acid], etc. Other known copolymers include poly[2,2-propanebis(4-phenyl)carbonate]-b/oc/(-poly(ethylene oxide), poly[2,2-propanebis(4-phenyl)carbonate]-Woc/c-polysulfone, poly[2,2-propanebis(4-phenyl)carbonate]-b/oc/c-poly(dimethylsiloxane), poly[2,2-propanebis(4-phenyl)carbonate]-b/oc/c-poly(methyl methacrylate), etc. These copolymers have in general good thermal resilience and decompose similarly to other polycarbonates [23]. 

A number of polyamide copolymers are known to have practical uses. The copolymers include those with different amides such as poly(caprolactam-co-laurolactam), poly(2,2,4-trimethyl-1,6-hexandiamine-co-2,4,4-trimethyl-1,6-hexandiamnie-co-1,4-benzendicarboxylic acid), poly(s-caprolactam-co-hexamethylene diamine-co-terephthalic acid), poly(hexamethylenediamine-co-terephthalic acid-co-isophthalic acid), etc. The addition of longer alkyl chains in an aromatic polymeric amide may improve some mechanical properties, but thermal resilience is in general reduced. For example, poly(hexamethylenediamine-co-m-xylylenediamine-co-isophthalic acid-co-terephthalic acid) starts decomposing at about 310° C, significantly lower than Nomex , for example. The same decrease in the decomposition temperature is seen for other mixed copolymers such as nylon 12 copolymers that include cycloaliphatic and aromatic segments. 

Some copolymers of poly(imides) found practical applications, typically due to their good thermal resilience. One such copolymer is poly(3,3, 4,4 -benzo-phenone-tetracarboxylic dianhydride-co-m-phenylene-4,4 -oxydianiline) with the structure indicated below ... 

Host outstanding properties of these products were high resilience and good resistance to stress decay. Resilience Is Illustrated In Figure 1 which shows the stress-strain relationship of a poly[(plvalolactone-b-lsoprene-b-plvalolactone)-g-plvalo-lactone] fiber as It was stretched 300% and then allowed to relax. The shaded area Is the work lost as the fiber was loaded and then unloaded. This area amounts to 13% of the total, which shows that work recovered was 87%. Such high resilience compares very favorably with that of chemically-cured natural rubber. 

The creation of the autocatalytic high MW aminic polyols based on N-methyl substituted poly amines, represents an important development in the area of poly ether polyols for low-fogging flexible PU foams. The VORANOL VORACTIV polyols developed by DOW represent a revolutionary group of autocatalytic polyols with reduced volatile organic compounds (VOC) emissions in PU products, especially in high resilience foams for bedding and automotive seating [149, 150]. 

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