Penetration behavior

The penetration behavior of resins into the wood surface also is influenced by various parameters, like wood species, amount of glue spread, press temperature and pressure and hardening time. The temperature of the wood surface and of the glue line and hence the viscosity of the resin (which itself also depends on the already reached degree of hardening) influence the penetration behavior of the resin [79]. 

HS Huang, RD Schoenwald, JL Lach. (1983). Corneal penetration behavior of betablocking agents. II Assessment of barrier contributions. J Pharm Sci 72 1272-1279. 

SCHOENWALD, R. D. AND HuANG, H.-S., Comeal penetration behavior of beta-blocking agents I Physicochemical factors., J. Pharm. Sci.,... 

In this model, whether kq is a function of the solvent viscosity depends upon the relative magnitudes of Mint) and Mext). If Mint) Mext),then kq will depend upon viscosity if Mint) > Mext), the structural fluctuations in the protein allowing penetration of the quencher determine the magnitude of M and change in bulk viscosity may not affect this rate. Simulation of protein penetration behavior suggests that the penetration rate should be extremely sensitive to the size and charge of the quencher.(65)... 

Epidermis Complete removal of the dermis may be achieved by several mechanical, thermal, and chemical techniques. Most commonly, the epidermal-dermal junction is split by heating the skin to 60 C for 30-120 s [83, 84], Pitman et al. [85] could show that such a treatment does not impair the barrier function. The use of ethylene diamine tetraacetic acid, sodium bromide, or ammonia fumes has also been reported [80, 83, 86], It may, however, be suspected that the use of sufficiently strong acids or bases may change the buffer capacity of skin, which would especially influence the penetration behavior of ionizable drugs. 

Figure 12. Typical nail penetration behavior of a 18650 lithium-ion cell with shutdown separator. This test simulates internal short circuit of a cell. Key (a) cell passed nail penetration test (b) cell failed nail penetration test.

Liposomes applied on the skin were also investigated for their delivery proprieties to the pilosebaceous units [15,23 28]. The in vitro skin penetration behavior of carboxyfluorescein incorporated in multilamellar liposomes (phosphatidylcholine cholesterol phosphatidylser-ine) and in another four nonliposomal systems (HEPES pH 7.4 buffer 5% propylene glycol 10% ethanol and 0.05% sodium lauryl sulfate) was studied by Lieb et al. [25]. Using two fluorescent techniques the authors found a higher accumulation of the probe within skin follicles when delivered from liposomes [25], Further, in an interesting setup of in vitro and in vivo experiments in mice, Hoffman s group observed liposomal delivery of the active Lac-Z gene and its expression mostly in the hair follicles [26,28]. 

Fig. 7.3 Penetration behavior elastic, plastic, hydrodynamic, explosive.

Figure 5. TMA Penetration Behavior of PS/PiBM Diblock Copolymer and Carboxylated Ionomer (5 mole percent-COC K ) Obtained after hydrolysis.

The results show a significant correlation between the penetration behavior and the degree of condensation (molecular size, viscosity) of the resins. The higher the degree of condensation, the lower is the penetration possibility, expressed as Average penetration depth (AP). The portion of filled tracheids in the radial direction on both sides of the bondline ( Filled interphase region , FIR) however, did not depend statistically on the viscosity of the resin mix. 

Semek and Resnik [27] investigated the penetration behavior of four melamine-urea-formaldehyde (MUF) resins with different contents of melamine and different molar masses, also adding slightly different amounts of extender to the resin mix. The lower the viscosity of the resin mix, the deeper was the penetration into the wood surface. 

This difference in flow behavior was examined for the three different UF resins. The average penetration behavior is shown in the results of Tables 2 and 3. Due to less deeper penetration the size of the interphase decreases as expected. It is defined as the sum of the deepest penetration on both sides of the bondline in each photograph examined, multiplied by the width investigated (1.4 mm). The maximum penetration depths are in the range of 335 pm for UF 1,300 pm for UF II and 177 pm for UF III, all numbers expressed as the sum for the penetration into both plies. 

For phenolic resins various studies concerning the influence of the degree of con-densahon on the penetration behavior and on bond strength have been performed [3]. 

Johnson and Kamke [15] used three PF resins with different degrees of conden-sahon in order to investigate the penetration behavior into the cell lumens and also the big vessels of hardwood (yellow poplar). The higher the molar mass, the less was the penetration into the wood flakes. Adhesive penetration into hardwood is likely to be dominated by flow into vessel elements. 

The objective of the work reported here was to expand the investigations of several of the authors [3] concerning the influence of the degree of condensation of UF adhesive resins on the penetration behavior into beech. Since this hardwood species exhibits a completely different wood structure compared to softwood (like fir), it can be expected that penetration of adhesives will occur to a different extent. The structure of beech is characterized mainly by big vessels instead of the rather narrow tracheid cells as it is the case with fir. The resins and adhesive mixtures used in the study reported here were the same as before [3]. The investigation of the... 

Figure 9 again presents difference in the penetration behavior between earlywood (upper ply) and latewood (lower ply). In the left lower comer two vessels (one fully... 

However, from the graph in Fig. 4 it is also evident that even using the same adhesive mix, variations in the penetration behavior occur. This is indicated by the bars showing the standard deviations of AP nevertheless, a statistically significant difference in AP is shown between the three adhesive types used in the investigations. 

The differences in the penetration behaviors have been addressed several times in the literature. Brady and Kamke [22] reported that fractures were abundant along the surface of earlywood flakes, opening additional flow paths. Rays were found to be a more important flow path into fir tissue. Most of the radial penetration of adhesive is probably through the ray cells and between the longitudinal tracheids... 

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