Pecan pith

Figure 2. Pullout forces of polyester cords for various tannin-containing adhesive dips as a function of percent resorcinol. 1, pecan pith sulfite extract 2, purified pine bark tannin 3, pine bark sulfite extract 4, peanut skin tannin.

At this time, it is not possible to pinpoint the reason for the poor performance of the pecan pith extract in bonding to nylon. The tannin is predominantly a prodelphinidin (S J jS -hexahydroxyflavan) instead of pro-cyanidin (Hemingway, R. W., Southern Forest Experiment Station, unpublished results), but that would not seem to be a reasonable cause for such a large difference in behavior. A comparison of elemental composition and carbohydrates obtained after hydrolysis shows much lower amounts of carbohydrates in the pecan pith extract (Table II). The low proportion of carbohydrate obtained after hydrolysis is consistent with comparatively high Stiasny polyphenol content of 87% for the pecan pith extract. 

The pecan pith extract was the best of the tannin extracts examined in bonding to polyester cord. Pullout forces using this extract to totally replace resorcinol were nearly twice as high as in the standard dip. The purified pine bark extract also gave very good results. One commonality in these two extracts... 

Chen (46) used sodium hydroxide extracts from southern pine Pinus spp.) bark, peanut Arachis hypogea) hulls, and pecan Carya illinoensis) pith as 20% replacements for phenol-formaldehyde resins in plywood adhesives. Bond quality was highly dependent on veneer moisture content and assembly time. Exterior quality bonds (U.S. Product Standard PS-1-74) in southern pine plywood were obtained if the veneer moisture content was 7.0% with 60-minute assembly times. Phenol-formaldehyde resin replacements could be increased to 40% by peanut hull and pecan pith extracts when the extraction solutions containing 5% of sodium hydroxide were used (45). Southern pine veneer (0.32 cm) was spread at a rate of 41.5 to 42.5 g/lOOOcm of double glue line and the layups were stored in a... 

Chen C M 1980 Phenol-aldehyde resin composition containing pecan pith extract and an aldehyde. U S Pat No 4201699... 

Chen C M 1980 Organic phenol extract compositions of pecan pith agricultural residues and method. U S Pat No 4201851... 

Four types of condensed tannins were studied in the adhesive dips 1) extracts from pecan nut pith obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, 2) purified tannins from southern pine bark, 3) extracts from southern pine bark obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, and 4) tannins extracted with acetone-water solutions from peanut skins. 

The sulfite extract of the pecan nut pith was obtained by extracting the finely ground red powder (509 gm) with sodium sulfite (20.4 gm) and sodium carbonate (2.0 gm) in 2549 mL of water. Approximately 1 hr was required to reach reflux temperature, and the suspension was heated at reflux for 2 hr. The suspension was cooled, the volume adjusted to a constant by addition of water, and it was filtered twice through glass wool. Aliquots (100 mL) of the recovered liquor were freeze-dried to determine the extract yield. The remainder was also freeze-dried to recover a dark brown solid. 

Table II. Elemental Composition and Carbohydrate Content of Sulfite Extracts from Pecan Nut Pith and Southern Pine Bark...

Authors Hamed and Chung are grateful to the Southern Forest Experiment Station, USDA Forest Service, for a cooperative grant (19-86-037) supporting this work. We thank Boise Cascade Corporation for supplies of southern pine bark, the Robertson Corporation for supplies of pecan nut pith, Associates Research Management Corporation for peanut skins, and Gen Corporation for resins and cord materials. 

These acid-catalyzed rearrangement reactions were also extended to a study in which pecan (Caraya illinoensis) nut pith tannins were reacted with phloroglucinol and acetic acid at lOO C for extended periods of time (727). Besides the formation of the anticipated 4-arylflavan-3-ols, these conditions also catalyze the formation of a unique series of novel [l]-benzofuro[2,3- ]chromenes, e.g. (121), and spirobidihydro[l]benzo-furans, e.g (122). The formation of products of type (121) demonstrates the susceptibility of the C(3)-hydroxyl group in 4-arylflavan-3-ols to inversion of configuration under acidic conditions, while that of the spiro compounds of type (122) is a further manifestation of the lability of the C(4)-C(10) bond in condensed tannin constituent unit. 

Southern pine bark, oak bark, pecan nut pith, and peanut hulls were selected as candidate materials in the study. Not only is there reason to believe that these may contain useful and extractable... 

Method Pine Bark Pecan Nut Pith Oak Bark Peanut Hulls... 

The unreacted free formaldehyde decreased rapidly at the first 30 minutes of reaction and then the rate of decrease slowed down gradually. However, there were few exceptions, i.e. peanut hull extracts obtained from 2% sodium hydroxide extraction at 185°C, and pine bark oak bark and pecan nut pith extracts reactivated with sulfonation. The paraformaldehyde was not dissolved completely even though the reactant had reached the prescribed reaction temperature of 60°C. It seemed that the paraformaldehyde dissolving rate at 60°C was greater than the rate of the reaction of formaldehyde toward the extracts, therefore, the unreacted free formaldehyde in solution increased with increase of the time. 

Table, 4. Unreacted formaldehyde (as percent of original amount) for different times and temperatures of reaction between paraformaldehyde and pecan nut pith extracts of various treatments.

Control Resin, B), Copolymer Resin of Southern Pine Bark Extracts, C), Copolymer Resin of Peanut Hull Extracts No. 1, D), Copol3mier Resin of Peanut Hull Extracts No. 2, E), Copolymer Resin of Pecan Nut Pith Extr. No. 1, and F), Copol3nner Resin of Pecan Nut Pith Extracts No. 2,... 

It is obvious that several of the copolymer resins provided superior bond quality in comparison to the commercial control, especially at the short press time of 2 minutes. It was also noted that the copol3nner resins containing pecan nut pith or peanut hull extracts seem to be more tolerant of press time and its interaction with assembly time. 

It can be seen from the figures that two of the five copolymer resins, namely those having 40% by weight of their standard phenol replaced by the extracts of (a) peanut hulls and (b) pecan nut pith, exhibited better bonding qualities than the resorcinol resin catalyzed commercial phenol-formaldehyde resin. Specifically, those... 

Dependence of Bond Quality on Press Time and Assembly Time, A) Commercial P-F Resin, B) Copolymer Resin with 60% Phenol Replaced by Peanut Hull Extracts, C) Copolymer Resin with 60% Phenol Replaced by Pecan Nut Pith Extracts. 

The copolymer resins with 60% by weight of phenol replaced by the extracts of peanut hulls and pecan nut pith were synthesized and evaluated in gluing southern pine plywood. 

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