Tensile elongation values, with

An important application of Eq. (3.39) is the evaluation of M, . Flory et al.t measured the tensile force required for 100% elongation of synthetic rubber with variable crosslinking at 25°C. The molecular weight of the un-cross-linked polymer was 225,000, its density was 0.92 g cm , and the average molecular weight of a repeat unit was 68. Use Eq. (3.39) to estimate M. for each of the following samples and compare the calculated value with that obtained from the known fraction of repeat units cross-linked ... 

Tensile elongation of PVA is extremely sensitive to humidity and ranges from < 10% when completely dry to 300—400% at 80% rh. Addition of plasticizer can double these values. Elongation is independent of degree of hydrolysis but proportional to the molecular weight. Teat strength increases with increasing relative humidity or with the addition of small amounts of plasticizer. 

Likewise, the mechanical properties of the copolymers were nearly identical or even somewhat enhanced towards the polyimide homopolymer in terms of the modulus and tensile strength values [44,47]. For most of the block copolymers, the elongations to break were substantially higher than that of PMDA/ODA polyimide (Table 4). The shape of the polyimide stress-strain curve is similar to that of a work-hardened metal with no distinguishable yield point... 

As a result, zones A, B, and C have comparatively a basic, neutral, and acidic character, respectively. Increasing the DC electric current leads to the overall acidification of the gel sample (see Fig. 6, curve 4) due to the easy ionization of the acidic groups. Consequently, this narrows the zones B and C and expands zone A. Polybetaine hydrogel membranes of isopropyl-2-[2 -(trimethylammonium)ethyl phosphoryl] ethyl fumaramate and 2-hydroxyethyl methacrylate effectively enhance the water content in comparison with poly(2-hydroxyethyl methacrylate) [224]. The content of water in hydrogel membranes increases, but the amount of adsorbed BSA decreases with the increase of the betaine content in the feed. The values of the tensile strength and tensile elongation of the hydrogel reach 68.4 g mm and 239%, respectively. 

There is only one hint in the literature, by Starkweather (10), that deals with copolymerization with butadiene. The polymers described there have poor tensile strength values and elongations. 

The dominant feature of all commodity plastics is their relatively low tensile strengths. These lie in the region of 10-37 MPa for the poly(a-olefins) and only assumes higher values with PVC and with PMMA (Table 36-5). On the other hand, the poly(alkanes) have quite a high elongation at break, which predestines their use as packaging films (see also Table 36-1). In contrast, the elongations at break of PVC and PS are very low. 

---