Influence of Domain Size on Toughness of Poly(styrene‐block‐butadiene) Star Block Copolymer/Polystyrene Blends

Abstract

Summary: The toughness of poly(styrene‐block‐butadiene) star block copolymer/polystyrene (PS) blends have been investigated using the essential‐work‐of‐fracture approach. The blends show a co‐continuous or layer‐like structure of polystyrene‐rich and polybutadiene‐rich domains arising from the used extrusion process. A tough‐to‐brittle transition at a critical domain size of polystyrene‐rich domains of about 50 nm and a maximum in the non‐essential work of fracture at 20–30% PS (co‐continuous morphology) have been found.

Crack Toughness Behaviour of Multiwalled Carbon Nanotube (MWNT)/Polycarbonate Nanocomposites

“…The slope of the linear-fit plot of specific work of fracture against the ligament length represents bw p and has an equivalence to the J integral. [28] The equivalence between the EWF concept and R-curve concept using the J integral has been shown by Mai and Cotterell. [29] They found that EWF ¼ J Ic , the critical J value as a measure of the stable-crack initiation toughness, and bw p ¼ 1 4 (dJ/da) (for DENT specimens) where dJ/da is the slope of the J-R curve (a: actual crack length).…”

Molecular‐Weight‐Controlled Brittle‐to‐Semiductile‐to‐Ductile Transition in S‐(S/B)‐S Triblock Copolymers

“…The conceptual equivalence between bw P and dJ / da estimated from J R curves based on elastic/plastic fracture mechanics concept was shown by Mai et al [24] The energyrelated resistance against stable crack initiation (EWF or w e ) in PYFM concept has a theoretical significance for qualitative assessment. It was already reported that in case of heterogeneous polymer systems like filled polymers and nanostructured blend systems [25][26][27] the value of the resistance against stable crack initiation is strongly dominated by the matrix i.e. the major phase.…”

Strain Field Analysis and Kinetics of Crack Propagation of Binary Triblock Copolymer Blends

“…The slope of the linear-fit plot of specific work of fracture against the ligament length represents bw p and has an equivalence to the J-integral concept. [8] The equivalence between EWF concept and R-curve concept using the J integral has been shown by Mai and Cotterell. [14] They found that EWF ¼ J Ic , the critical J value as a measure of the stable-crack initiation toughness, and bw p ¼ 1/4dJ/da (for DENT specimens) where dJ/da is the slope of the J-R curve (a-actual crack length).…”

“…Recently, two miscible triblock copolymers were combined to create thermoplastic elastomers (TPE) with increased tensile strength without any change in their elasticity by Lach et al [5] where novel morphologyproperty correlation could be established. The effects of the microphase morphology on the strength and stiffness of blends containing amorphous block copolymers have been reported in a few studies, [3,[6][7][8][9] but these were mainly blends with homopolymers. Recently, mechanical and fracture behaviour of partially miscible block copolymer blends of styrene-butadiene (SB) star block and styrene-b-styreneco-butadiene-b-styrene (S-SB-S) triblock copolymers have been studied.…”

“…[7] Similarly, the crack initiation and crack propagation behaviour in case of other microphase-separated blend systems like four-arm star SB block copolymer/homopolystyrene blends have been reported to have a correlation with the polystyrene (PS)-domain thickness which is in the range of 26-63 nm. [8] Despite all these developments, the correlation between the macroscopic fracture mechanical behaviour and morphology needs to be explored further to understand their practical utility for an objective application.…”