Flexure adhesion

Figure 4.49 Polymer-cement ratio vs. flexural adhesion of latex-modified mortars to ordinary cement mortar.

The surface weight of conversion layers is 0.05-5 g/m. With higher surface weights the flexibility of the layers decreases, which has an adverse effect on the flexural adhesion of the organic coating. 

Fig. 22. Adhesion rating based on flexural sti engths of laminates of poly(styrene) with glass treated with various silane coupling agents vs. solubility parameter of the organo-functional group of the coupling agent. From ref. [117], by permission.

The lap shear test involves measuring the adhesive shear strength between two surface fluorinated polyolefin sheet tokens that are adhesively secured with a reinforcement resin. The tokens are individually reinforced with steel backing plates to eliminate flexural distortion in the shear joint. Lap shear tests carried out with various reinforcing polyester-type resins, contrasting fluorination and oxyfluorination as surface treatment, are shown in Table 16.8. 

Consideration of the relationship between the effects of radiation on homopolymers and copolymers raises the question of the variation from homopolymer behaviour with sequence length. Every copolymer has a distribution of sequence lengths for each comonomer. At what minimum sequence length does methyl methacrylate not show the high scission of PMMA The future will probably see the development of processes for making polymers with controlled mini-block sequences to maximize a number of properties such as scission yield, adhesion, flexural strength, Tg.. 

ISO 5893 2002 Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of traverse) - Specification ISO 6237 2003 Adhesives - Wood-to-wood adhesive bonds - Determination of shear strength by tensile loading... 

Madhukar, M.S. and Drzal, L.T. (1991). Fiber-matrix adhesion and its effects on composite mechanical properties II. Longitudinal (0°) and transverse (90°) tensile and flexural behaviour of graphite/epoxy composites. J. Composite Mater. 25, 958-991. 

The presence of the cement hydrate/polymer comatrix in LMM and LMC confers superior properties, such as high tensile and flexural strengths, excellent adhesion, high waterproofhess, high abrasion resistance and good chemical resistance, when compared to ordinary cement mortar and concrete. The degree of these improvements however depends on polymer type, polymer-cement ratio, water-cement ratio, air content and curing conditions. Some of the properties affected by these factors are discussed below [87, 88, 93-95]. 

Most latex-modified mortars and concretes have good adhesion to most substrates (tile, stone, brick, steel and aged concrete) compared to conventional mortar and concrete. In general, bond strength in tension and flexure increases with an increase in the polymer-cement ratio,... 

Halogenated butyl rubbers have particularly advantageous adhesion behavior, flexural strength, service life and impermeability to air and water (40). The specific structure of the halogenated butyl rubber depends on the conditions of halogenation. 

Sample preparation and measuring apparatus has been discussed and hence this section will deal with the principal item, the tensile machine, together with grips and extensometer. The tensile machine is in fact very often a universal machine in that, apart from tensile tests, it can also be used for flexural, compression, tear and adhesion tests. The basic elements of a tensile machine are shown diagrammatically in Figure 8.10. 

Both fiber-matrix interphase-sensitive mechanical tests (interlaminar shear strength, 90° flexure) and interphase-insensitive tests (0° flexure) were conducted on high volume composite samples fabricated from the same materials and in the same manner as discussed above to see if the interphase and its properties altered the composite mechanical properties and in what manner. A summary of the data is plotted as a bar graph in Fig. 7. The first set of bars represents the difference in fiber-matrix adhesion measured between the bare fibers and the sized fibers by the ITS. The composite properties plotted on the figure also show increased values for the epoxy-sized material over the bare fiber composite. 

Fig. li. The change in failure at the single-fiber level as shown by the embedded single-fiber test is mirrored by the failure behavior at the macroscopic level. The increase in adhesion also tracks the same between the ITS results and 0° flexure data. 

Petterson13 has shown that the use of only 50 percent of the stoichiometric amount of hexamethylenediamine imparts to a cured DGEB A adhesive the maximum butt-joint strength, bulk tensile strength, and flexural moduli, whereas higher proportions of the diamine give lower properties. 

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