The Effect of Ultraviolet Light on the Color of Unbleached Pulps: Literature Survey

A literature survey was prepared which covered the published information on the effects of ultraviolet light on the color of unbleached pulps. Experiments were conducted with eight types of unbleached pulp which were converted into optical test pads under varying pH conditions, using sulphuric acid and caustic soda as well as alum and sodium aluminate for adjustment of the hydrogen ion concentration. The optical test pads were exposed to ultraviolet irradiation. Thereafter, reflectance measurements were taken, covering the range of visible light. From the limited number of experiments which were conducted we can conclude that: 1. Unbleached coniferous kraft, unbleached hardwood, sulphite, and unbleached hardwood soda pulps brightened when exposed to ultraviolet light. 2. Unbleached hardwood H.S.S.C. (70% yield), unbleached hardwood N.S.S.C. (78% yield), unbleached coniferous sulphite, unbleached hardwood cold soda, and unbleached hardwood chemi-groundwood pulps yellowed when exposed to ultraviolet light. 3. Adjusting the pH four with sulphuric acid increased the reflectance of most pulps while adjusting the pH to ten with sodium hydroxide decreased the reflectance of the pulps. This was observed before irradiation with ultraviolet light. 4. When papermakers\u27 alum was used to adjust the pH of the sheets to four, the reflectance values before irradiation decreased slightly in most cases. There was a larger drop in the reflectance value when the pH of the pulp is adjusted to the pH ten with sodium aluminate. 5. Both means of adjusting the pH to ten, namely sodium hydroxide and sodium aluminate, decreased the initial brightness of the pulp. However, there was little correlation between the effects of the two compounds used to adjust the pulp pH to four, namely sulphuric acid and papermakers\u27 alum. 6. Experimental results showed that none of the compounds used in pH control stabilized consistently the color of unbleached pulp exposed to ultraviolet irradiation

Increasing the Hardwood Content on the Furnish by Separate Refining

Introduction It is an old papermaker\u27s adage that paper is made in the beater. This means that the performance and the physical properties of the paper are determined by the type and the extent of the mechanical action to which the fibers are subjected before they are joined to form paper. The terms used to describe the function of refining; free beaten, wet beaten, et al are all traditionally vague, by reason of the complicated structure of the fibers and the even more complicated changes these fibers undergo during the refining process

The Influence of Single, Two, and Three Stage Bleaching on Fading Characteristic of Deinked Stock

A literature survey on the various bleaching methods used on deinked stock and the factors which influence the fading characteristic of deinked stock is compiled. Mention is also made of various additives which have an influence on the fading of a sheet. A description of the experimental work with caustic deinked stack of various groundwood content follows. Results indicate that the groundwood content has more effect upon fading of deinked stock than the number of stages of bleaching, although the increase in the number of stages of bleaching does reduce the amount of fading in a sheet. A greater effect by the number of stages of bleaching is obtained in the higher groundwood range

Ultrastructural characterization (morphological and topochemical) of wood pulp fibres

Different electron microscopy techniques including SEM (scanning electron microscopy), FE-SEM (field emission-scanning electron microscopy), TEM (transmission electron microscopy) and Immuno-gold TEM (immuno-gold transmission electron microscopy) were applied in order to gain a better understanding of the influence of the native softwood fibre cell wall ultrastructure including morphology and topochemistry (i.e. lignin and glucomannan distribution) during mechanical pulping. In thermomechanical pulp (TMP) processing, wood fibres undergo structural changes (cell wall delamination and fibrillation) that are regulated by the native fibre micro- and ultrastructure. In addition, novel information was obtained on the fibre cell wall architecture. In contrast, the stoneground wood (SGW) process inflicted severe damage to the fibre structure resulting in transverse and longitudinal fibre breakage. However, juvenile wood SGW fibres showed improved properties (strength and light scattering) compared to mature wood. Ultrastructural aspects of fibre processing and development explained the differences in physical properties observed. During the SGW process, the native morphological fibre cell wall ultrastructure and microfibrillar organization governed the manner of juvenile wood fibre development similar to TMP fibres. Ultrastructural studies on Norway spruce and Scots pine TMPs revealed fundamental features that governed the different behaviour exhibited by the two wood species. Specific ultrastructural characteristics of pine TMP fibre cell walls were explored in relation to both morphology and topochemistry and that regulating the different pine fibre development mechanisms compared to spruce. The negative behaviour shown by Scots pine during TMP processing was most likely attributable to the observed fibre development mechanism. Histochemical techniques were applied to study wood resin associated problems during mechanical and kraft pulping. Studies provided information on the spatial micro-morphological distribution/redistribution of lipophilic extractives that were visualized on single fibre and cell wall fractions. Results from histochemical staining and chemical analysis performed on Norway spruce and Scots pine TMPs showed that there were morphological and chemical differences in the redistribution of extractives between the two species. This may further contribute to the effects of extractives on pulp- and paper properties and processing. Localization of lipophilic birch wood extractives involved in pitch problems was performed using histochemical techniques. Correlated information from gas chromatography-mass spectrometry and specific staining methods gave details on how extractives are removed during processing as well as information on the mechanisms of removal

Low Shrinkage Bleaching of Unbleached Neutral Sulphite Semichemical Pulp

The main objective of this research project was the investigation of the most feasible method for the bleaching of a soft-cooked unbleached neutral sulphite semichemical aspen pulp cooked to a 70 percent yield. Furthermore, treatment of unbleached, laboratory bleached and commercially bleached neutral sulphite semichemical pulp with a new chemical, sodium borohydride, was also carried out. The results of our experimental work showed that, the best bleaching procedure was when 15 percent chlorine as hypochlorite was used in the first stage, followed by a hydrochloric acid soaking stage with a final treatment of 2.6 percent hydrogen peroxide. With the above procedure brightness values over 80 percent were obtained with the yields in the 90 percent range based on the weight of the pulp. Sodium borohydride treatment of the three pulps showed that, with regards to ultra-violet light and heat stability the chemical, sodium borohydride, had no effect on the unbleached and the bleached lignin-containing pulps. Treatment of the commercially bleached, lignin-free, pulp however showed that the chemical had a marked effect in improving the heat and light stability of the pulp. It was noted that with all three types of pulp the chemical sodium borohydride did procedure a bleaching effect

The Effects of Fiber Furnish on Physical Properties of Paper

This experiment was designed to determine the effects of fiber furnish on the physical properties of paper. To do this various pulps and combinations of these pulps were formed into handsheets and their physical properties determined. The tests performed on the handsheets were tear, fold, tensile, stretch and tensile energy absorption. The findings of this report indicates possibilities of a linear relationship between percent of pulp in a sheet and the fold and tensile. Stretch values increase by various degrees as more of the higher stretch fiber is added. The TEA follows the stretch values very closely

Impact of Delayed Completion of Previously Initiated Therapy and Provider Type on Outcomes of Root Canal Treatment

Objective:if the provider type influences long-term outcomes in instances where NSRCT has been previously initiated. The primary purpose of this study was to determine if the period of time between previously initiated therapy and the completion of non-surgical root canal treatment (NSRCT) influences long-term outcomes. The secondary purpose of this study was to determineMaterials/Methods: Enrollment and claims data from Delta Dental of Wisconsin from2002-2014 was analyzed. Teeth that received NSRCT within 6 months after completionof pulpal debridement or pulpotomy procedures (identified by Codes of DentalProcedures and Nomenclature) and within a continuous insurance coverage period wereincluded. Teeth that did not receive definitive restorations within 180 days followingcompletion of NSRCT were excluded. Teeth were followed from the time of treatment tothe presence of a CDT code representing untoward events, which include retreatment,apicoectomy, or extraction. The impact of tooth location, age at time of NSRCTcompletion, and provider type on the outcome was also examined using Univariate andMultivariable Cox proportional hazards models. A total of 7,488 NSRCTs were includedin the analysis. Results:. Molar teeth were associated with a greater risk of an untoward event than anterior teeth with an adjusted hazard ratio of1.52 (p\u3c0.029). An increase in the risk of failure was observed in teeth from patients that were 55 and older with an adjusted hazard ratio 2.15 (p\u3c0.001). A significantly lower adjusted hazard ratio of 0.68 (p\u3c0.001) was observed when treatment was initiated by a general dentist and completed by an endodontist when compared to treatment that was both initiated and completed by a general dentist.Conclusion: Delayed completion of NSRCT after previously initiated therapy was not associated with unfavorable outcomes.No statistically significant difference was found among the varying time intervals between initiation and completion of NSRCT Improved outcomes were noted when previously

FTIR-DRIFTS-based prediction of β-carotene, α-tocopherol and L-ascorbic acid in mango (Mangifera indica L.) fruit pulp

Mango fruits contain substantial vitamins and dietary fibre. Vitamins vary among and within fruits depending on cultivar type and ripening stage. Conventional techniques of vitamins analysis are based on High Pressure Liquid Chromatography, which are costly and laborious. This study evaluated the potential of Fourier transform infrared-diffuse reflectance spectroscopy (FTIR-DRIFTS) technique in predicting β-carotene, α-tocopherol and L-ascorbic acid in pulps of four mango cultivar types (‘Apple’, ‘Kent’, ‘Ngowe’, and ‘Tommy Atkins’). Combination of ran dom forest (RF) and first derivative spectra developed the predictive models. Factorial ANOVA examined the interaction effect of cultivar type, site (‘Thika’, ‘Embu’ and ‘Machakos), and fruit canopy position (sun exposed/within crown) on β-carotene, α-tocopherol and L-ascorbic acid contents. RF Models gave R2 = 0.97, RMSE = 2.27, RPD = 0.72 for β-carotene; R2 = 0.98, RMSE = 0.26, RPD = 0.30 for α-tocopherol and R2 = 0.96, RMSE = 0.51, RPD = 1.96 for L-ascorbic acid. Generally cultivar type affected vitamin C, F (3, 282) = 7.812, p < 0.05. Apple and Tommy Atkins had higher mean vitamins than Ngowe and Kent. In Machakos, within canopy fruits had higher β-carotene than sun-exposed fruits, F (5, 257) = 2.328, p = 0.043. However, interactions between fruit position, site and cultivar did not affect α-tocopherol and vitamin C. In Thika, Tommy Atkins at fully ripe stage had higher vitamin C than at intermediate maturity stage, F (2, 143) = 7.328, p = 0.01. These results show that FTIR-DRIFTS spectroscopy is a high-throughput method that can be used to predict mango fruit vitamins of in a large data set

The Effect of Varying Drying Temperatures on the Recyclability of Thermomechanical Pulps

There has been conflicting data regarding the effects of recycling on pulps. Strength properties go down for chemical pulps after being recycled, but the strength properties go up for mechanical pulps after recycling. The objective of the thesis will be to study the effects of varying the drying temperature on the recycled fiber properties of thermomechanical pulp. A never-dried thermomechanical pulp furnish was obtained, from which three samples were separated out. Pulp sample one was air dried at approximately 77°F, sample two was dried at a temperature of 155°F, and the third sample was dried at a temperature of 250°F. Handsheets were made, dried, conditioned and tested for each of the three pulp samples. The paper was then soaked, disintegrated and dried at the same temperature as before. This continued to three recycles. It was imperative that the pulps remained free of contaminants and dried at the same temperature each time. Strength properties were tested and the following key results were obtained. Density of all three samples increased slightly due to the unravelling of the fibers. The breaking length decreased for the samples dried at 155 and 250°F up to the second recycle, the sample that was dried at 250°F had the largest decrease in breaking length. The 250°F sample had an initial breaking length of 3.36km and this dropped to a value of 2.82 (km) after the second recycle. This is in comparison to an initial of 2.97 (km) and a value of 2.81 (km) after the second recycle for the 155°F sample. The air dried sample did not show an increase or decrease in overall breaking length strength. Upon examination of the wet breaking length data, it was shown that because of the 250°F samples underwent crystallization and did not absorb as much water as the 155°F or air dried sample, they had the highest wet breaking strength. The value of the wet breaking length for 250°F after three recycles was .132 (km) as compared to .122 (km) and .0859 (km) for the 155°F and the air dried samples, respectively. Scott Bond test showed a slight decrease in bond strength up through the second recycle and the zero span test showed that the fiber strength increased slightly. This explains that the loss of breaking length strength for the samples is due to loss of bond area and strength and not loss of fiber strength. The data supports the hypothesis that drying at higher temperatures does have the greatest negative effect on the recyclability of thermomechanical pulp. However, and more importantly, the data also shows that as the number of recycles increases, the effect of temperature on the sheet properties decreases

The Retention of Wet Strength Resins as Determined by the Kjeldahl Method

True wet strength is not a gauge of water proofness of paper, but is a measure of the residual strength of the paper gauged by the mullen, tear, burst, and fold, after the paper has been completely soaked in water and the resistance to water penetration has been completely broken (1). To increase the wet-strength of paper, a number of different resins may be applied, and these resins may be broadly classified as anionic or cationic in nature. Of these resins, three particular resins will be discussed, cationic melamine-formaldehyde, anionic urea-formaldehyde, and cationic urea-formaldehyde