Shear strength, of polymers

Method of test for shear strength of polymer-modified mortar ... 

Liu K, Piggott MR, Shear strength of polymers and fibre composites, Part 2 carbon/epoxy pultrusions, Composites, 26(12), 841-848, 1995. 

The interfacial shear strength of polymer composites reinforced with lignocellulosic fibers has been evaluated using (9.2) for the critical length obtained in CLP curves. Transformation of this equation provides a simple way to determine the IFSS of a system composed of a given lignocellulosic fiber embedded into a polymeric matrix. 

Harris, J.S., Ward, I.M. and Parry, J.S.C. (1971) Shear strength of polymers under hydrostatic pressure surface coatings prevent premature fracture. J. Mater. Sci., 6,... 

Polyimides of 6FDA and aUphatic diamines with good low temperature processkig and low moisture swelling are known to be useful as hot-melt adhesives (109). Aluminum strips bonded by this polymer (177°C/172 kPa (25 psi) for 15 min) exhibited a lap-shear strength of 53 MPa (7690 psi) at room temperature and 35 MPa (5090 psi) at 100°C. The heat- and moisture-resistant 6F-containing Pis useful ki electronic devices are prepared from... 

The polysulfide base material contains 50—80% of the polyfunctional mercaptan, which is a clear, amber, sympy Hquid polymer with a viscosity at 25°C of 35, 000 Pa-s(= cP), an average mol wt of 4000, a pH range of 6—8, and a ntild, characteristic mercaptan odor. Fillers are added to extend, reinforce, harden, and color the base. They may iaclude siUca, calcium sulfate, ziac oxide, ziac sulfide [1314-98-3] alumina, titanium dioxide [13463-67-7] and calcium carbonate. The high shear strength of the Hquid polymer makes the compositions difficult to mix. The addition of limited amounts of diluents improves the mix without reduciag the set-mbber characteristics unduly, eg, dibutyl phthalate [84-74-2], tricresyl phosphate [1330-78-5], and tributyl citrate [77-94-1]. 

St. Clair et. al. investigated a series of maleimide and nadimide terminated polyimides and developed LARC-13 [8,9]. Changing the terminal group from maleimide to nadimide, the value of the lap shear strength of a titanium lap shear joint increased from 7 to 19 MPa [9]. They also added an elastomeric component to the adhesive formulation. The introduction of 15 wt% of a rubbery component, ATBN (amine terminated butadiene nitrile polymer) and ADMS (aniline terminated polydimethyl siloxane) enhanced the adhesive properties as follows 19 MPa to 25 MPa (ATBN) titanium T-peel strength 0.2 kN/m to 1.4... 

Desaeger, M. and Verpoest, I. (1993). On the use of the microindentation test technique to measure the interfacial shear strength of fiber reinforced polymer composites. Composites Sci. Technol. 48, 215-226. 

In using Eq. (6.10) to predict / , of a given composite system it is important that the said failure mechanisms all exist. If any one mechanism is apparently absent the corresponding toughness term must be excluded from the / t equation. It is also worth emphasizing that / , varies linearly with reciprocal of the frictional shear strength of the interface, i.e. l/tf, with the lower limit of (1 — Ff)/fm when if approaches infinity. This relationship has been shown to apply to many carbon fiber polymer matrix composites (CFRPs) (Harris et al., 1971 Beaumont and Phillips,... 

The isophthaloyl based polymer in Table 12 gave unoriented thin film tensile strength, modulus and elongation at room temperature of 114.4 MPa, 3.55 GPa and 4.4%, respectively [35], The relatively high modulus for the amorphous film was unexpected. Titanium-to-titanium tensile shear strengths of the isophthaloyl based polymer after 1000 hours of exposure at 200 °C in air were 34.1 MPa at 23 °C, 22.2 MPa at 150 °C and 7.6 MPa at 177 °C [35]. The strength at 177 °C was surprising since the Tg was only 182 °C. DSC and WAXS analyses revealed that the adhesive was amorphous. 

Figure 4. Effect of EME 58 (58 wt% mercaptoester unit co-polymer) coupling agent concentration on the lap shear strength of acrylic/steel joints following 7 day immersion in 57°C water. See Appendix 4 for acrylic resin formulation and Appendix 5 for shear strength procedure.

Differences in the frictional properties of most plastics can be explained in terms of the ratio of shear strenghth to hardness. Shooter and Tabor observed that the coefficients of friction for polytetrafluoroethylene are 2—3 times lower than anticipated by this calculation. It is believed that this discrepancy is caused by the inherently low cohesive forces between adjacent polymer chains and is responsible for the absence of stick-slip. The large fluorine atoms effectively screen the large carbon-fluorine dipole, reducing molecular cohesion so that the shear force at the interface is low. The shear strength of the bulk material is higher because of interlocking molecular chains. 

The shear strength of coatings metallized by employing composition-graded films is dependent on the extent and strength of chemical bonding between the substrate surface and the plasma polymer film. 

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