PMMA, fracture toughness

These effects have been found by Creton et al. [79] who laminated sheets of incompatible polymers, PMMA and PPO, and studied the adhesion using a double cantilever beam test to evaluate fracture toughness Fc. For the original laminate Fc was only 2 J/m, but when interface reinforced with increasing amounts of a symmetrical P.M.M.A.-P.S. diblock copolymer of high degree of polymerisation (A > A e), the fracture toughness increased to around 170 J/m, and then fell to a steady value of 70 J/m (Fig. 9). 

Fig. 31 Fracture toughness, Kic, at about 10 jims 1 for PMMA as a function of temperature (From [46])...

Jia etal. 1999 (23) MWCNT CVD Untreated tubes Treated tubes In situ polymerization Improved In situ polymerization CNT Loading levels 1 to 10 wt% Tensile Strength, fracture toughness and hardness increased with CNT loading from 0 to 7 wt% using treated tubes and improved method Tensile Strength Untreated tubes Treated tubes In situ poly. Improved In situ poly. Wt% MPa Wt% MPa 0 54.9 3 66.8 1 21.2 5,7 71.7 3 20.3 10 47.2 FTIR and SEM studies revealed CNT participation in PMMA polymerization and presence of a strong interface between CNTs and PMMA ... 

Fig. 10. Fracture toughness K, as function of crack speed a in PMMA at room temperature as reported by different authors...

Fig. 3.21 Fracture toughness Kj versus crack speed d in PMMA at room temperature as measured in different tests ...

As an example, Fig. 8 shows the fracture toughness for PMMA and Fig. 9 the fringe pattern transition at the critical temperature, whereas Fig. 10 shows the lateral face of the sample with the crack-tip above and below the critical temperature. It has also been shown that neither the bulk modulus nor the craze stress varies near the critical temperature (Fig. 11 and 12). It seems that the local material property varying near that particular temperature is the craze stiffness, as shown in Fig. 13. 

Fig. 8. Fracture toughness K, (at about lOjim/s crack velocity) for PMMA over a wide temperature range. Note the sharp increase of K, below the critical temperature = —20 C, below which multiple crazing occurs at the crack tip. Above the critical temperature, Kj remains almost constant versus temperature. From Ref courtesy of Chapman and HaU, Ltd.

Analysis of the fracture toughness of PMMA and of the shape of a single craze at a... 

Fig 8. Dynamic fracture toughness (from MSM and DKC) and fracture energy for PMMA... 

Table 1, Round robin results for fracture toughness testing of a modified GF-PMMA...

Fig. 32. Maximum achievable fracture toughness of interfaces between A and B polymers reinforced with block copolymers or end-grafted chains as a function of the degree of polymerization N of the reinforcing block. (A) PS-b-PMMA between PPO and PMMA ( ) dPS-COOH chains in a HIPS matrix grafted on an epoxy interface ( ) dPS-COOH chains in a PS matrix grafted at an epoxy interface (O) PS-b-PVP chains at the interface between PS and PVP. Data from [22,36,38,40]...

Fig. 40. Fracture toughness gc of interfaces between glassy homopolymers as a function of their width a7. a ( ) PS/PS interfaces ( ) PS/PPMS interfaces (A) PS/PBrxS interfaces, b ( ) PS-r-PVP/PS interfaces, ( ) PS-r-PMMA/PS and PS-r-PMMA/PMMA interfaces. Data from [67,69,70]...

Figure 8 Adhesion of PMMA to PPO. Effect on fracture toughness, Gc, of interfacial density, E, of a reinforcing diblock copolymer (after Ref 81).

Cho Choi, S. R., Salem, J. A. Fracture toughness of PMMA as measured with indentation cracks. J. 

Zho Zhou, J., Wang, Y., Xia, Y. M. Mode-I fracture toughness measurement of PMMA with the Brazilian disk test. J. Mater. Sci. 41 (2006) 5778-5781. 

---