Weight percent gain

The wet environment does cause a slight relaxation of the stress, but the extent of relaxation required to prove Croll s reasoning (13) is far from being achieved. The weight percent gained by the epoxy was found to be 0.1%. The slight stress relaxation by moisture was also found by Dannenberg, who also showed the effect to be reversible. 

To study the rate of reaction and obtain adequate weight percent gain (WPG), reaction periods varying from 1 to 8 hours were used. Effect of sample thickness on overall acetylation levels was examined on 7.5 cm long mango samples of different cross-sections (6x6 mm2, 12.5 x 12.5 mm2, 20 x 20 mm2, 25 x 25 mm2, and 30 x 30 mm2). These samples were acetylated in vapor phase for 3 and 6 hours. 

Figure 2. Relationship between weight percent gain (WPG) and acetyl content. Key O, mango A, chir.

Figure 3 Relationships between the weight percent gains due to allylation and the grafting ratios of styrene on wood meal. Note copolymerized at lOO C for 2 h using BPO 0.041 mol/L as an initiator. (From Ref. 13.)...

Figure 4 IR spectra of allylated wood copolymerized with styrene. WPG, Weight percent gain due to allylation. Note (a) allylated wood (b-d) allylated woods copolymerized with styrene (e) alkalinepretreated woods copolymerized with styrene. (From Ref. 13.)...

Weight percent gain Fiber saturation point... 

Specimens of Sitka spruce Picea sitchensis) and Glehn spruce Picea glehnii) were modified by eight kinds of chemical treatment. Weight percent gain (WPG) resulting from each chemical treatment was determined based on the over-dry weight of the specimen before and after treatment. 

Wood Weight percent gain Percent weight loss after 12 weeks... 

Table 5 Weight Percent Gain (WPG) and Antiswelling Efficiency (ASE) of Formalized Cedar and Beech Blocks, and Their Weight Loss (WL) Due to Decay After 12 Weeks Laboratory Tests with Tyromyces palustris and Coriolus versicolor, and After 9 Months Soil Burial Test...

Green Volume M Oven-Dry Volume (in. ) AV (%) Treatment Oven-Dry Volume After Treatment Weight Percent Gain... 

Treatment Weight Percent Gain Increase in Wood Volume with Treatment (cm ) Calculated Volume of Chemical Added (cm )... 

Reagent Weight Percent Gain Benzene/Ethanol 4 h Soxhlet 20 Mesh (%) Benzene 24 h Soxhlet 40 Mesh (%) Water 24 h Soxhlet 40 Mesh (%) Water 7 d Soaking Blocks (%) 0 1 0 0... 

Similar results are observed on IR spectra of acetylated wood (122). As the weight percent gain increases upon acetylation, the absorption band at 1730 cm increases because of the carbonyl group in the acetyl bond. 

By far, maximum research has been done on the reaction of acetic anhydride with cell wall polymer hydroxyl groups to give an aeetylated fiber. Jute [37 39] and kenaf [40,41] have been reacted with acetic anhydride. Without a strong catalyst, acetylation using acetic anhydride alone levels off at approximately 20 weight percent gain (WPG). The equilibrium moisture content (EMC) and thickness swelling at three relative humidities for fiberboards made from these fibers is shown in Table 7.13. 

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