Polymer Flexible Joints

Keywords Polymer flexible joints, repair method of concretes, polymer modified concretes, copolymer dispersion additive, airfield concrete pavements, high deformations. 

Typically, rapid repair of main cracks in slabs is realized using bituminous masses covering only the damages. Unfortunately, this kind of protection is ineffective just after few months of exploitation, because the degraded mass (Fig. 2b, 2c) allows for infiltration of water under slabs [8]. The coming into being hydrodynamic pump effect (due to moving loads - Fig. 3a) destructs sealants in joints (Fig. 3b) and causes uneven settlement of concrete slabs (Fig. 3c). The solution of this problem is the use of special polymer flexible joints. 

Repair of concrete and cement-polymer composites using of polymer flexible joints... 

Figure 11. Three-point bending test on concrete specimens (500x100x100 mm). Tested specimen just after failure and after repair using of polymer flexible joint...

Effectiveness of repair using of polymer flexible joint tested on airfield concrete pavements... 

Calculation of polymer flexible joints. Considered polyurethane mass PM belong to the group of elastomeric materials, thus can be described using theory of the hyperelastic materials. In simple approach of this theory, properties of polymer mass are obtained from uniaxial tension and compression tests according to (Eq. 4), presented in [21], Following equation (Eq. 4), the (Eq. 5) is proposed for calculation of uniaxial deformation of a flexible polymer joint. 

A. Kwiecieh Polymer flexible joints - an innovative repair system protecting cracked masonries against stress concentrations. Proceedings of Protection of Historical Buildings, PROHITECH 09, Mazzolani (ed), Taylor Francis Group, Vol.2, pp. 1033-1038, London,... 

Figure 1.5 Placement of successive polymer segments connected by perfectly flexible joints. In (a), the ith and (i + l)th bond can be moved through angles 0 and 6 so that carbon 3 can lie anywhere on the surface of a sphere. In (b), the pattern is illustrated for a longer portion of chain.

The physical significance of 2 in Equation (73) is somewhat harder to define. At first glance it appears to be the length of the repeating unit, about 0.25 nm for a vinyl polymer. We must remember, however, that the derivation of Equation (73) assumed that the coil was connected by completely flexible joints. Molecular segments are attached at definite bond angles, however, so an actual molecule has less flexibility than the model assumes. Any restriction on the flexibility of a joint will lead to an increase in the dimensions of the coil. The effect of fixed bond angles on the dimensions of the chain may be incorporated into the model as follows. 

The characteristic ratio CL for is related to the ratio Cy, for the mean-square radius of gyration (Eq. [7]). For a random (freely jointed) chain, CL = 6C. Therefore, there is a relation between the persistence length, the mean end-to-end distance, and the mean radius of gyration in the limit of long chains. Through this relation, we appreciate that Rq) can also be used to describe polymer flexibility. 

A shift toward utilizing physicochemical processes, newer materials, and techniques is inevitable [23]. Processes such as wafer bonding [24], stereolithography [25], and self-assembly [2 can enable complex 3D structure fabrication. Smart composite microstructures [27] of carbon, silicon, polymer, etc., can provide for robust structures with flexible joints. For tools, metals such as stainless steel, platinum-tantalum, and nickel-titanium or natural materials such as gelatin and collagen can be used. 

It is worth recalling that any of the molecular force laws given by Eqs. (13-16) are derived within the framework of the freely-jointed model which considers the polymer chain as completely limp except for the spring force which resists stretching thus f(r) is purely entropic in nature and comes from the flexibility of the joints which permits the existence of a large number of conformations. With rodlike polymers, the statistical number of conformations is reduced to one and f(r) actually vanishes when the chain is in a fully extended state. 

A general method has been developed for the estimation of model parameters from experimental observations when the model relating the parameters and input variables to the output responses is a Monte Carlo simulation. The method provides point estimates as well as joint probability regions of the parameters. In comparison to methods based on analytical models, this approach can prove to be more flexible and gives the investigator a more quantitative insight into the effects of parameter values on the model. The parameter estimation technique has been applied to three examples in polymer science, all of which concern sequence distributions in polymer chains. The first is the estimation of binary reactivity ratios for the terminal or Mayo-Lewis copolymerization model from both composition and sequence distribution data. Next a procedure for discriminating between the penultimate and the terminal copolymerization models on the basis of sequence distribution data is described. Finally, the estimation of a parameter required to model the epimerization of isotactic polystyrene is discussed. 

First approaches at modeling the viscoelasticity of polymer solutions on the basis of a molecular theory can be traced back to Rouse [33], who derived the so-called bead-spring model for flexible coiled polymers. It is assumed that the macromolecules can be treated as threads consisting of N beads freely jointed by (N-l) springs. Furthermore, it is considered that the solution is ideally dilute, so that intermolecular interactions can be neglected. 

The main parameters used to describe a polymer chain are the polymerization index N, which counts the number of repeat units or monomers along the chain, and the size of one monomer or the distance between two neighboring monomers. The monomer size ranges from a few Angstroms for synthetic polymers to a few nanometers for biopolymers. The simplest theoretical description of flexible chain conformations is achieved with the so-called freely-jointed chain (FJC) model, where a polymer consisting of N + I monomers is represented by N bonds defined by bond vectors r/ with j= Each bond vector has a fixed length r,j = a corresponding to the... 

Long-term inertness without loss of strength, flexibility, or other necessary physical property is needed for use in artificial organs, prostheses, skeletal joints, etc. Bioerodability is needed when the polymer is used as a carrier such as in controlled release of drugs, removal of unwanted materials, or where the materials purpose is short-lived, such as in their use as sutures and frames for natural growth. 

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