Brittleness polymers

In bulk-crystallized polymers, lamellae are often organized into spheruHtes, spherical stmctures which grow outward from a point of nucleation, typically to about 0.01 mm in diameter. SpheruHtes are in some ways similar to the grain stmcture in metals. They can make a polymer brittle and also reduce transparency. 

Styrene polymers brittle fracture of, 23 363 burning of, 23 403 extrusion of, 23 398 glass-reinforced, 23 311 tensile strengths of, 23 359 Styrene product, factors in the quality of, 23 338-339 Styrene vapors, 23 403 Styrenic block copolymers, 24 102, 703-704... 

Dibutyl phthalate is a plasticizer added to the poly(vinyl chloride) used in vinyl upholstery and garden hoses. Since plasticizers are more volatile than the high molecular weight polymers, they slowly evaporate with time, making the polymer brittle and easily cracked. Plasticizers like dibutyl phthalate that contain hydrolyzable functional groups are also slowly degraded by chemical reactions. 

The immediate direct quenching prevents the growth of large spher-ulites, which cause polymer brittleness and degrade mechanical properties of the solid state polymerized polymers. The method has been exemplified with poly(amide)s (PA)s and poly(butylene terephthalate) (PBT). 

PEDOT-PSS/PVAc composites showed brittle mechanical property. A decrease in tensile strength was observed for each composition in comparison to the PVAc and tensile strength decreased with increasing PEDOT-PSS content in the composition. However, afterward PI.00 sample yield decreases, leading to more brittle fractures due to a high value of PEDOT, which has a typical mechanical property of conductive polymers (brittleness). 

Traditionally—and that started with metals—one distinguishes two types of mechanical behavior of polymers brittle and ductile. It will be clear to us after discussion of the free volume concept in Subsection 24.1.3 that brittle behavior will dominate at low temperatures when the free... 

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The decrease in creep compliance (i.e. increase in Young s modulus), as well as the increase in yield stress, can be viewed as advantages for many industrial applications. Unfortunately, these changes are counterbalanced by a catastrophic decrease in ductility/toughness, as schematized in Fig. 12.3. Thus, the consequence of structural relaxation can be understood as an increase in the polymer brittleness. 

Sprodbruch, Trennbruch brittle polymer sprodes Polymer brittleness... 

As it has been noted above, the main feature of polymers is that they consist of long chain macromolecules. Therefore, it is to be expected that polymer chains structure and their characteristics will be influenced essentially on bulk polymers properties. One of such polymer chain structural factors is availability in it of bulk side groups, which results to bulk polymers brittleness enhancement [40], A side groups effect on plasticity level for heterochain polymers was considered in Ref. [41], where brittleness increase was explained by side groups nonparticipation in local or macroscopic plasticity processes. 

At low temperatures, all plastics tend to become rigid and brittle. This happens mainly because, at lower temperatures, the mobility of polymer chains is greatly reduced. In the case of the amorphous polymers, brittle failure occurs at a... 

Plasticisers are incorporated into the more rigid plastics, particularly PVC, to make them more flexible. The types of compounds used as plasticisers also act as impact improvers due to their ability to reduce polymer brittleness. Plasticised PVC pipe is used extensively for transferring beer from the keg to the dispenser. Plasticisers are also used to some extent in cellulose acetate and polyethylene terephthalate, in film, sheet and pipe form. 

Addition of plasticizer occasionally makes polymers brittle or harder, which is called antiplasticizing . Materials such as polyvinyl chloride (PVC) [151,152], polysulfone [153], polyethylene ether [154], and polyamide 66 [155] sometimes exhibit both types of behavior. This is because an increased degree of order (crystallinity) results from the increased polymer chain mobility by the addition of plasticizer. Further increases of plasticizer can finallyreduce crystallinity. 

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