Phenol peels testing

Squeamish patients will overwhelm the doctor with complaints, worries, questions and reproaches. It is better to test a patient s mental and physical resistance by first suggesting a painless peel without complications and then progressing onto a medium-depth peel before considering a phenol peel. Individual tolerance can be tested in this way, and the patients themselves gradually learn what a peel is and what it can do for them. 

Stable blends of UCAR Acrylic Latex 152 and phenolic dispersion BKUA-2260 were prepared by preneutralizing the acrylic latex with ammonia and adding the phenolic. Acetone-water solutions of acrylic-CK-1834 phenolic were prepared by adding the acrylic latex to an acetone solution of CK-1834 at the level necessary to yield a 15% solids solution. Indicated surfactants were then added to this solution. Metal adhesion samples were assembled wet and peel tested at 2"/tnin. after 1 week of drying at room temperature. 

Periocular skin is particularly delicate and prone to ectropion. After discussing what ectropion is, 1 discuss the risk factors for its occurrence. These include blepharoplasties and previous resurfacing procedures. 1 perform a simple snap test to determine the elasticity of the lower eyelids in patients who wish to reduce the wrinkling in that area. Lower eyelids which quickly return to the normal position after being pulled down may tolerate straight phenol without forming an ectropion. Patients whose eyelids very slowly return to full apposition should not receive phenolic peels of any kind on the lower lids. Loss of elasticity in the lower lid is common following blepharoplasty and in elderly patients. 

It is vital to understand that each kind of test evaluates only one factor. The shear test cannot assess durability, and the peel test cannot ensure complete cross-linking of the resin. Perhaps the worst violation of this principle is the use of ultrasonic inspections to over-rule failure to pass the coupon tests for parts that are deemed too expensive to scrap. There are never any written specifications allowing this, but there are also no written instructions prohibiting material review boards from making such decisions. Fortunately, since the introduction of phosphoric-acid bonding and phenolic-based adhesive primers, the processes have become more robust than the testing techniques and such decisions have not created a safety problem. 

Note that studies made with the original unmodified polyphenylene oxide etched in the above solution for 3 min at 65 °C have revealed that chromic acid solution becomes ineffective after its first use. The evaluation was made with AF-30 nitrile-phenolic adhesive and modified T-peel tests. If it is desired to avoid this possible problem, vacuum blasting, followed by an acetone wipe, can be used. ... 

Adhesion depends on a number of factors. Good adhesion is defined by most customers as substrate failure. The major adhesive manufacturers possess equipment that allows them to make bonds with customer substrates under conditions that closely simulate actual packaging lines. These bonds are peeled either automatically or by hand to gauge adhesion. The most important factors influencing adhesion are the wet-out of the substrate, partieularly by the polymer component of the adhesive system, and the specific adhesion with the substrate. Choice of resin is critical for both. Rosin, rosin esters and terpene phenolics are eommonly added for these purposes in EVA and EnBA-based systems. Adhesion at low temperatures is also influenced by the overall toughness of the system at the test temperature. 

Brown and Kaplan presented a more complex solution of phenol (at varying concentrations between 60% and 95%) mixed with saponified cresol in oil at concentrations of up to 10%. The application technique included a patch test behind the ear. This test made it possible to assess the necrotic effect of the solution on the patient. If the necrosis was too severe, the test was repeated with increasing concentrations of oil until the right solution for the patient was found. They recommended applying the solution area by area, leaving 2 hours between applications. The peel took 2 days to complete. 

Brown and Kaplan made use of the buffering property of oils in phenol solutions. Their formulation contained up to 95% phenol combined with oils. A patch test behind the ear had to be carried out before the facial peel. If there was skin necrosis, they reduced the strength of the phenol by gradually adding oil in small quantities until the right dose was found for the patient s skin. To increase the strength of the mixture, on the other hand, soap (saponified cresol) was added or the concentration of phenol was increased. 

As shown in Table 3 in an elevated temperature shear test, acrylic/BKUA-2260 systems perform extremely well, while elevated temperature peel shows some fall off in performance. Since the BKUA-2260 is self-crosslinking at elevated temperature and has the ability to co-cure with certain acrylic and vinyl-acrylic latexes, the elevated temperature performance of bonds depends, to some extent, on the previous thermal history of the bond. The shear test involves a slow heat up to test temperature and allows the bond to cure partially. Mechanical properties of thermally cured films of UCAR Latex 154/BKUA-2260 show 10 fold modulus increases over the uncured films. Vinyl-acrylic latexes that do not have the ability to co-cure with the phenolic do not exhibit the same high elevated temperature shear values. 

Figure 8.1 Test peel patches on day 4, left cheek, in Fitzpatrick skin type I treated with tour formulae (1) 48% phenol. 0% croton oil (2) 35% phenol, 0.4% croton oil (3) 35% phenol, 2.2% croton oil, and (4) 35% phenol, 0% croton oil. Each formula was tested with 50, 20 or 5 rubs with small semi-diy Q-tips (cotton buds). Results showed (1) phenol Is not all-or-none (2) croton oil increases depth of injury (3) In this study there was little observable difference between 0.4% and 2.2% croton oil (4) mbbing increases depth of injury, and (5) human experimental models have inherent variables...

Based on quantifiably reproducible experimental test peel patch studies on the right cheek and, later, left cheek test peel patches (reported below), using 48% phenol with 0.0% croton oil, 35% phenol with 0.4% croton oil, 35% phenol with 2.2% croton oil, and 35% phenol with 0.0% croton oil (see Fig. 8.1), a lowering of the threshold affect to create injury (Fig. 8.2) to between 5 and 20 rubs can be seen when croton oil is added. This is down from the 20 to 50 rubs required when croton oil is excluded. The early appearance of coagulation is not a true indicator of depth of peel, nor is the immediate density of frost as evidenced by the reported superficial results from 88% USP Phenol which can produce an immediate, dense, white frost. The length of time a given formula is applied, the concentration of phenol and croton oil, the volume of acid, the vigor and abrasiveness of the application and... 

Figure 8.3 African-American with truncal congenital Becker nevus treated with one formula (Stone II 60% phenol, 0.2% croton oil) over twelve test patches, six In each of two rows. (A) Immediately after peel applications (from left to right) of 1, 5, 10, 20, 50, and 100 rubs (B) top row covered with waterproof tape, bottom row covered with Aquaphor ointment (C) at 48 hours tape removed, thymol Iodide powder applied. Threshold effect between 10 and 20 rubs seen at 10 days (D) and 73 days (E) post peel...

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