Chemical peroxide treatment

Fig. 9 Ozone bleaching (Z) of a beech sulfite pulp, followed by a peroxide stage (P). SM starting material, Z ozone treatment, ZP ozone - peroxide treatment. Left differential MWD and carbonyl DS. Right ADSco plots showing the differences in carbonyl content between the bleached sample and the respective starting material. Reprinted with permission from Biomacromolecules (2002) 3 969. Copyright (2002) American Chemical Society...

Effects of various chemical treatments such as sodium hydroxide, isocyanate, permanganate, and peroxide on the tensile properties of sisal fiber-reinforced low-density polyethylene (LDPE) composites were investigated. Sodium hydroxide treated fiber composites showed better tensile properties than xmtreated composites, and the enhancement was attributed to their rough surface topography and increased aspect ratio. It was reported that long chain structured cardanol derivative of toluene diisocyanate (CTDIC) treatment reduces the hydrophilic nature of the sisal fiber resulting in improved compatibility and dispersion. It was also reported that peroxide treatment of fiber showed maximum interfacial interactions [33]. 

Extensive work was carried out by Joseph et al. on many treatments of natural fiber (alkali, permanganate, peroxide (DCP and BPO), isocyanate) for improving the mechanical properties of sisal fiber LDPE composites. The results showed that in every case the mechanical properties were increased with chemical treatment but peroxide treatment showed the best results (Table 22.12) [58, 59]. 

The work carried out by Kalaprasad and Thomas [34] shows different chemical surface modifications such as alkali, acetic anhydride, stearic acid, permanganate, maleic anhydride, silane, and peroxides improving the interfacial adhesion and compatibility between the fiber and matrix. A polyethylene thermoplastic matrix with sisal and glass hybrid composites was developed. The results showed that in all treatments, tensile strength increased about 10-30% and peroxide treatment showed maximum tensile strength and Young s modulus [34]. 

Thiazolo[3, 4 >l,2][l,4]diazepino[8,9-a]benzimidazoles. — [CgNS-CaNz-C -CrN2], l-(3 -Bromopropyl)-2-(4"-thiazolyl)benzimidazole (339) isomerizes above 100 °C to 6,7-dihydro-5/f-thiazolio[3, 4 -l,2][l,4]diazepino[8,9-a]-benzimidazole bromide (340), the structure of which is established by its spectral properties and chemical behaviour. Treatment with alkali cleaves its thiazolium ring the resulting thiol (341 R = SH) is isolable as the 5 >methyl derivative (341 R = SMe) and is oxidized by hydrogen peroxide... 

The common chemical methods for extraction of PHB are solvent extraction, chemical digestion using sodium hypochlorite, sodium hypochlorite and chloroform, surfactants, surfactant hypochlorite digestion, surfactant chelate digestion, chelate hydrogen peroxide treatment, selective dissolution of nonpolymer cell mass by proton etc. 

The theoretical treatments of controlled degradation are based on its radical character [189, 191, 192, 202] and chemically (peroxide) initiated degradation, or pure chain random scission, where Saito s integral is valid [202a]. 

Peroxide treatment Natural fibres are immersed in a solution of dicumyl (or benzoyl) peroxide in acetone for about half an hour, then decanted and dried [123]. Recent studies have highlighted significant improvements in the mechanical properties. In a study of polyethylene hybrid composites, sisal and glass fibres were proposed to reinforce the matrix in terms of tensile strength and modulus. Among different chemical treatments, benzoyl peroxide treated fibres revealed to be more successful. This was attributed to the peroxide-initiated grafting of polyethylene on to the fibres [124]. 

The radicals are then involved in oxidations such as formation of ketones (qv) from alcohols. Similar reactions are finding value in treatment of waste streams to reduce total oxidizable carbon and thus its chemical oxygen demand. These reactions normally are conducted in aqueous acid medium at pH 1—4 to minimize the catalytic decomposition of the hydrogen peroxide. More information on metal and metal oxide-catalyzed oxidation reactions (Milas oxidations) is available (4-7) (see also Photochemical technology, photocatalysis). 

Many electroless coppers also have extended process Hves. Bailout, the process solution that is removed and periodically replaced by Hquid replenishment solution, must still be treated. Better waste treatment processes mean that removal of the copper from electroless copper complexes is easier. Methods have been developed to eliminate formaldehyde in wastewater, using hydrogen peroxide (qv) or other chemicals, or by electrochemical methods. Ion exchange (qv) and electro dialysis methods are available for bath life extension and waste minimi2ation of electroless nickel plating baths (see... 

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