Mechanical compatibility tests

The American Society for Testing and Materials (ASTM) provides standards, compatibility testing, and tests for mechanical properties, recommended practices and procedures as well as codes for polymeric materials. The various industry codes and standards are summarized in Table 4.95. 

Figure 13.1 The tensile test of collagen hydrogel, nanofibre mesh, and their composite-containing fibroblast cells demonstrating that the mechanical property of hydrogel can be increased significantly by hybridisation with nanofibres and cells, which meets the mechanical compatibility for specific application.

In vivo testing in animal models is essential for implanted biomaterial devices (e.g., scaffolds) to determine biodegradation, mechanical compatibility, FBR, and biocompatibility of the material with host tissue or device function. 

Daniels PH, Cabrera A. Plasticizer compatibility testing dynamic mechanical analysis and glass transition temperatures. J Vinyl Addit Technol 2015 21(1) 7-11. 

A complete set of intermolecular potential functions has been developed for use in computer simulations of proteins in their native environment. Parameters have been reported for 25 peptide residues as well as the common neutral and charged terminal groups. The potential functions have the simple Coulomb plus Lennard-Jones form and are compatible with the widely used models for water, TIP4P, TIP3P and SPC. The parameters were obtained and tested primarily in conjunction with Monte Carlo statistical mechanics simulations of 36 pure organic liquids and numerous aqueous solutions of organic ions representative of subunits in the side chains and backbones of proteins... 

A compatible blend should have good processing properties along with a smooth surface and cross-section. If needed, further tests on mechanical properties should be carried out on testing samples made from 2-mm films produced by compression molding. 

A series of polyester-based TPU (566TPU series) were synthesized in our lab and used to blend with PVC to manufacture a modified PVC material for medical uses [14]. Morphological studies showed that 566TPU has very good compatibility with PVC. Detailed mechanical and electronic property tests were also conducted. Some of the data are provided in Tables 3 and 4. 

These results showed that TPU, represented here by 566TPU, has the best overall results in modifying PVC among those tested. It has good compatibility with PVC, and the resulting polymeric blends have good mechanical properties suitable for various processing methods. 

This second group of tests is designed to measure the mechanical response of a substance to applied vibrational loads or strains. Both temperature and frequency can be varied, and thus contribute to the information that these tests can provide. There are a number of such tests, of which the major ones are probably the torsion pendulum and dynamic mechanical thermal analysis (DMTA). The underlying principles of these dynamic tests have been covered earlier. Such tests are used as relatively rapid methods of characterisation and evaluation of viscoelastic polymers, including the measurement of T, the study of the curing characteristics of thermosets, and the study of polymer blends and their compatibility. They can be used in essentially non-destructive modes and, unlike the majority of measurements made in non-dynamic tests, they yield data on continuous properties of polymeric materials, rather than discontinuous ones, as are any of the types of strength which are measured routinely. 

Typically, a binary system was selected as the base component of the recipe and the addition of polyelectrolytes to either side (core or receiving bath) was tested to evaluate the change in the capsule properties. The 33 successful multicomponent membrane systems are presented in Table 1. The components of the core material side (21 different chemical compositions) are listed in the first column, while the receiving bath components (20 different chemical compositions) are listed in the second column. With the exception of xanthan and CMC, the first polymer listed on the core side are gelling polymers which form beads with the appropriate ionotropic cation (salt). CMC can also be gelled by ions (alum), although they are considered to be non-compatible for cellular applications. The cations were tested both sequentially, usually with ionotropic cation first, and simultaneously. Walled capsules with adequate mechanical properties were often obtained through the simultaneous application of two polycations. Such a... 

Our screening and testing of multicomponent capsules/beads is incomplete. However, it offers a novel approach for the material selection for immobilization devices, which permits the simultaneous control of permeability, mechanical stability, and compatibility. The alternative multicomponent systems presented herein offer new possibilities for biomaterials, particularly those employed in bio artificial organs. 

Newly developed injectable CNTs will require both in vitro and in vivo testing to determine biocompatibility, blood compatibility, mechanical stability, and safety (Pearce et al., 2007). Here, we review the current articles on toxicity of CNTs and in vivo barriers. 

Martino et al. have demonstrated the use of BN felt separators in engineering tests. They have high porosity ( 90%), and hence, low ionic resistance, in addition to excellent compatibility with other cell materials at the operating temperature of 470 °C. However, this separator is too expensive and has poor mechanical properties and so cannot prevent electrode shape change during cell operation. ... 

In the case of SB, DB and propellants, slow but autocatalytic decomposition of NC and NG takes place even at ambient temperatures. This is retarded by the addition of a stabilizer to these propellants and thus the compatibility and the stability or life of these propellants increases. The silvered vessel test and stabilizer consumption rate are the methods which are generally used to predict safe chemical life of propellants in Europe, USA, India and other countries. The migration of explosive plasticizer (NG) and non-explosive plasticizers ( , DEP) from propellants to inhibitors or vice-versa also affect the ballistics, mechanical properties and life of inhibited propellants. 

Composite propellants consist of an oxidizer (AP/AN/ADN), a metallic fuel such as Al, Mg etc and a binder, usually a polymer which also serves as a fuel. Vacuum stability tests (VSTs) suggest that composite propellants are intrinsically more stable than SB, DB and propellants. However, use of more exotic ingredients such as oxidizers (ADN and hydrazinium nitroformate, HNF), binders [poly([NiMMO)] and poly([GlyN)] are likely to introduce severe compatibility-related problems [30, 31]. Some recent research in this direction indicates that stability of such propellants is largely determined by the chemical and mechanical properties of propellants. However, early evidence of deterioration generally comes from a change in their mechanical properties rather than from chemical investigations [32]. 

Excipient compatibility and stability studies rely on two underlying assumptions. One is that there is no change in reaction mechanism as temperature increases the second is that the excipient is also chemically stable under the conditions of test. However, if the reaction mechanism does change with temperature, it is likely the result will show a disproportionately greater breakdown than would be anticipated from lower temperature studies. Thus the risk is that an excipient is rejected that might in reality be perfectly suitable for the formulation. In many cases this is probably an acceptable risk. 

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