Browsing by Author "Ndiritu, F. G."

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“Effect of AC Helmholt magnetic field on the mass of Rosecoco deans”
(Taylor and Francis Online, 2011-06-09) Kamweru, P. K.; Ndiritu, F. G.; Kinyanjui, T. K.; Muthui, Z. W.; Ngumbu, R. G.; Odhiambo, P. M.
Plastic bags mostly made of polyethylene (PE) cause pollution as solid waste due to their non-degradability nature. Initiation of a degradative process by enhanced photo-oxidation is a possible method for an accelerated degradation. This paper presents temperature treatment effects on PE films where photodegradation was initiated using ultraviolet (UV) irradiation in the ranges of 200–300 nm and 300–400 nm for 2 hr. Effects of temperature of 40°C and 55°C on non-UV-irradiated and UV-irradiated PE films processed by conventional methods were investigated and evaluated after 50 hr, 150 hr, and 350 hr of temperature exposure. The effects of UV wavelength range irradiation on the degradation were deduced. Measuring the dynamic moduli using a dynamic mechanical analyzer monitored the degradation. The decrease in average storage modulus was 62% with treatment at 55°C, higher than the 16% drop at 40°C for unirradiated samples after 350-hr exposure. Cross-linking in UV-exposed samples, characterized by an increase in dynamic modulus (stiffening), was observed followed by a reduction of storage modulus. Temperature treatment at 55°C together with 300–400-nm UV range irradiation resulted in the largest increase, i.e., 22% after 150 hr, followed by the largest reduction of storage modulus, i.e., 74.6% for a cumulative 350-hr exposure.
Structural Properties of High Density Polyethylene Matrix Composites Reinforced with Open Air and Furnace Rice Husks Ash
(Academic Journals expand your Knowledge, 2021) Jonathan, M. K.; Osamong, G. A.; Butembu, S.; Kamweru, P. K.; Gichumbi, J. M.; Ndiritu, F. G.
In this work, rice husks ash (RHA) was introduced to pure and recycled high density polyethylene (HDPE) matrix, at varying ration (0-50%) to formulate rice husks ash High density polyethylene (RHA- HDPE) composite. RHA was obtained by burning fresh rice husks either by open-air burning (oRHA) or furnace calcination at 700°C (fRHA). The composite samples were made by melt-mixing the HDPE in an oven at a temperature of 150°C and adding different percentages of RHA in presence of maleic anhydride compatibilizer. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were carried out to determine the structural properties of the samples, and both suggest occurrence of composting chemical changes. For all RHA-HDPE samples, a broad band was noted between 970-070cm-1. This was highly contributed by the RHA and associated to Si-O-Si stretching modes. Other peaks are associated with Si-O-C interaction and O-Si-O bending vibrations in the samples. Scanning electron Microscopy (SEM) micrographs for HDPE indicated a smooth and uniform surface with a number of voids. On addition of RHA, the particles filled these voids making the sample surface rough. This roughness is seen to increase with increased percentage of RHA. The studies conclude that the cheaply obtained oRHA is as good as the fRHA in making RHA-HDPE composite.
Study of Humidity and UV wavelength effects on degradation of photo irradiated polyethylene films using DMA
(2012-03-12) Kamweru, P. K.; Ndiritu, F. G.; Kinyanjui, T. K.; Muthui, Z. W.; Ngumbu, R. G.; Odhiambo, P. M.
Plastic bags, mostly made of polyethylene, cause pollution as solid waste due to their nondegradable nature. Accelerated degradation, as a solution to mitigate the menace, can be achieved through moisture enhanced photolysis. This study evaluated the effect of three relative humidity environments, i.e., 25%, 40%, and 60% RH, at a constant temperature of 55°C. The effect was studied for ultraviolet (UV) irradiated and nonirradiated samples of polyethylene (PE) films processed under conventional ways. Photodegradation was initiated using ultraviolet irradiation in the ranges (200–300) nm and (300–400) nm for two hours and the effects of subsequent humidity treatment analyzed. Dynamic mechanical analysis was used to measure the dynamic storage modulus to monitor degradation. For nonirradiated samples, there was essentially no change in storage modulus at the three relative humidity environments after 550 hrs. Irradiation in the (300–400) nm range showed faster degradation than for the (200–300)nm range with the highest drop in storage modulus being 67% after 550 hrs. Raising the humidity from 25% to 40% and 60% RH resulted in 41%, 62%, and 67% drop of storage modulus, respectively, at the 550 hrs.
Study of Humidity and UV Wavelength Effects on Degradation of Photo-Irradiated Polyethylene Films Using DMA
(2011-06-09) Kamweru, P. K.; Ndiritu, F. G.; Kinyanjui, T. K.; Muthui, Z. W.; Ngumbu, R. G.; Odhiambo, P. M.
Plastic bags, mostly made of polyethylene, cause pollution as solid waste due to their nondegradable nature. Accelerated degradation, as a solution to mitigate the menace, can be achieved through moisture enhanced photolysis. This study evaluated the effect of three relative humidity environments, i.e., 25%, 40%, and 60% RH, at a constant temperature of 55°C. The effect was studied for ultraviolet (UV) irradiated and nonirradiated samples of polyethylene (PE) films processed under conventional ways. Photodegradation was initiated using ultraviolet irradiation in the ranges (200–300) nm and (300–400) nm for two hours and the effects of subsequent humidity treatment analyzed. Dynamic mechanical analysis was used to measure the dynamic storage modulus to monitor degradation. For nonirradiated samples, there was essentially no change in storage modulus at the three relative humidity environments after 550 hrs. Irradiation in the (300–400) nm range showed faster degradation than for the (200–300)nm range with the highest drop in storage modulus being 67% after 550 hrs. Raising the humidity from 25% to 40% and 60% RH resulted in 41%, 62%, and 67% drop of storage modulus, respectively, at the 550 hrs.
Study of Temperature and UV wavelength Range Effects on degradation of Photo Irradiated polyethylene films using DMA
(2011-06-09) Kamweru, P. K.; Ndiritu, F. G.; Kinyanjui, T. K.; Muthui, Z. W.; Ngumbu, R. G.; Odhiambo, P.M.
Plastic bags mostly made of polyethylene (PE) cause pollution as solid waste due to their non-degradability nature. Initiation of a degradative process by enhanced photo-oxidation is a possible method for an accelerated degradation. This paper presents temperature treatment effects on PE films where photodegradation was initiated using ultraviolet (UV) irradiation in the ranges of 200–300 nm and 300–400 nm for 2 hr. Effects of temperature of 40°C and 55°C on non-UV-irradiated and UV-irradiated PE films processed by conventional methods were investigated and evaluated after 50 hr, 150 hr, and 350 hr of temperature exposure. The effects of UV wavelength range irradiation on the degradation were deduced. Measuring the dynamic moduli using a dynamic mechanical analyzer monitored the degradation. The decrease in average storage modulus was 62% with treatment at 55°C, higher than the 16% drop at 40°C for unirradiated samples after 350-hr exposure. Cross-linking in UV-exposed samples, characterized by an increase in dynamic modulus (stiffening), was observed followed by a reduction of storage modulus. Temperature treatment at 55°C together with 300–400-nm UV range irradiation resulted in the largest increase, i.e., 22% after 150 hr, followed by the largest reduction of storage modulus, i.e., 74.6% for a cumulative 350-hr exposure.
Use of Magnetic Fields Reduces α-chaconine, α-solanine, and Total Glycoalkaloids in Stored Potatoes (Solanum tuberosum L.)
(Wiley Periodicals LLC., 2022) Irungu, F. G.; Tanga, C. M.; Ndiritu, F. G.; Mwaura, L.; Moyo, M.; Mahungu, S. M.
This work aimed to assess the suitability of magnetic fields (MF) to reduce glycoal- kaloids (GAs) in stored potatoes. The effects of the source of magnetic fields (direct current [DC] and alternating current [AC]), magnetic field intensity (1, 2, and 3 mT), and storage type (dark store—herein referred to as the control store and a commercial store with varying light intensity) on quantities of GAs were investigated. Subjecting tubers to increasing levels of MF intensities and placing them in the control store led to a significant (p < .05) decrease in α-chaconine and an increase in α-solanine. However, storage of potatoes in the commercial store after exposure to increasing MF intensities led to a significant (p < .05) decrease in α-solanine and an increase in α- chaconine. The use of AC MF with an intensity of 2 mT resulted in a significant (p < .05) reduction in α-chaconine, α-solanine, and TG. Novelty impact statement: Magnetic fields are an emerging non-thermal technology that has wide potential in food processing applications. The findings in the current work revealed that magnetic fields can be used to reduce quantities of toxic glycoal- kaloids in potatoes during storage, and thus improve their postharvest quality. The results offer practical insights on postharvest management of potatoes to ensure re- duction of losses and thus positively impact food and nutritional security.