Tensile strength prediction

For the 19 original materials, tensile strength predictions were not obtained by WLF theory for compounds K, M and R and by the Arrhenius relation for compounds J, K, L, P, S, T, W and X. These cases are associated with either a small change on namral ageing, small changes from accelerated ageing, anomalous behaviour or too great an extrapolation needed from the WLF master curve. 

B. Igne, C. A. Anderson, and J. K. Drennen, Radial Tensile Strength Prediction of Relaxing and Relaxed Compacts by Near-Infrared Chemical Imaging, Int.. Pharm., 418,297 (2011). 

Li Z M, Yang W, Xie B H, Shen K Z, Huang R and Yang M B (2004) Morphology and tensile strength prediction of in situ microfibrillar poly(ethylene terephthalate)/polyethylene blends fabricated via slit-die extrusion- hot stretching-quenching, Macromol Mater Eng 289 349-354. 

An area of great interest in the polymer chemistry field is structure-activity relationships. In the simplest form, these can be qualitative descriptions, such as the observation that branched polymers are more biodegradable than straight-chain polymers. Computational simulations are more often directed toward the quantitative prediction of properties, such as the tensile strength of the bulk material. 

Strength predictions of composites are ia general quite complex and somewhat limited. This is particularly tme of compressive and shear strengths, which are needed, together with the tensile strengths, ia composite failure prediction. 

The latter equation contains constants with well-known values and can therefore be used to predict the fracture stress of most polymers. For example, the bond dissociation energy Do, is about 80 kcal/mol for a C-C bond. For polystyrene, the modulus E 2 GPa, A. 4, p = 1.2 g/cm, = 18,000, and we obtain the fracture stress, o A1 MPa, which compares well with reported values. Polycarbonate, with similar modulus but a lower M. = 2,400 is expected to have a fracture stress of about 100 MPa. In general, letting E 1 GPa, p = 1.0 g/cm, and Do — 335 kJ/mol, the tensile strength is well approximated by... 

Only a small amount of work has been done up to now concerning the prediction of bond strengths and other properties based on the results of the analysis of the resin. Ferg et al. [59] worked out correlation equations evaluating the chemical structures in various UF-resins with different F/U molar ratios and different types of preparation on the one hand and the achievable internal bond as well as the subsequent formaldehyde emission on the other hand. These equations are valid only for well defined series of resins. The basic aim of such experiments is the prediction of the properties of the wood-based panels based on the composition and the properties of the resins used. For this purpose various structural components are determined by means of - C NMR and their ratios related to board results. Various papers in the chemical literature describe examples of such correlations, in particular for UF, MF, MUF and PF resins [59-62]. For example one type of equation correlating the dry internal bond (IB) strength (tensile strength perpendicular to the plane of the panel) of a particleboard bonded with PF adhesive resins is as follows [17]... 

In an isotropic material subjected to a uniaxial stress, failure of the latter type is straightforward to predict. The tensile strength of the material will be known from materials data sheets and it is simply a question of ensuring that the applied uniaxial stress does not exceed this. 

Because many plastics are relatively flexible, analysis should consider how much deflection might result from the loadings and elevated temperatures the products might see in service. The equations for predicting such deflections should use the modulus of the material its tensile strength is not pertinent. Usually, the most effective way to reduce de-... 

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