Thermal oxidation of polyolefins by mild pro-oxidant additives based on iron carboxylates and lipophilic amines: Degradability in the absence of light and effect on the adhesion to paperboard

Marine and inland pollution by non-degradable plastic bags and other plastic articles is a topic of great concern. Natural degradation processes based on oxidation of plastic pollutants could possibly contribute to limit the extent of pollution. Thermal degradation of polyolefins in the absence of light by non-polluting pro-oxidants has not been presented before. In this study, we show that two amines, stearyl amine and [(3-(11-aminoundecanoyl) amino) propane-1-] silsesquioxane (amino-POSS) in combination with ferric stearate (FeSt3) tremendously accelerate the thermal oxidation of polyolefins compared with reference samples. Both amines and FeSt3 are to a large extent based on renewable resources. Polyethylene and polypropylene samples containing less than 100 ppm of iron and 1% of amine were extremely brittle after 10 days in a circulation oven in the absence of light. No significant degradation could be seen with samples containing iron but no amine. In a different application, the initial oxidation of polyethylene can be used in order to increase its adhesion to cardboard. Excellent adhesion between polyethylene and cardboard is important for liquid packaging based on renewable resources. Amino-POSS has been chosen for food packaging applications due to its expected lower leakage from polyethylene (PE) compared with stearyl amine. Film samples of PE/amino-POSS/FeSt3 blends were partly oxidized in a circulation oven. The oxidation was documented by increased carbonyl index (CI) and melt flow index (MFI). The limited extent of oxidation has been proved by unchanged tensile strength and only moderate changes in elongation at break when compared to reference polyethylene films containing no FeSt3 or amino-POSS. The PE/amino-POSS/FeSt3 blends were compression moulded to paperboard. The adhesion of non-aged blends to paperboard decreased with increasing amino-POSS content which is in good compliance with an earlier reported lubricant effect of high amounts of POSS in PE. Thermal ageing of PE/amino-POSS/FeSt3 films prior to coating however led to a significant increase in adhesion. Improved physical interlocking due to increased MFI and interaction between C=O of the blends and OH of paperboard can explain the adhesion improvement. The films were not brittle after thermal ageing, which makes their use in industrial packaging feasible. A mechanism explaining the role of amines during thermal oxidation of polyolefins in the presence of iron is proposed.publishedVersio

Mixing of cellulose nanofibrils and individual furnish components: Effects on paper properties and structure

Thermo-mechanical pulp (TMP) handsheets with different fractions of cellulose nano fibrils (CNF) and ground calcium carbonate (GCC) were made. CNF and retention chemicals were added in three different ways; to GCC, to long fibre fraction (LFF) or to complete furnish. The different addition strategies affected dewatering time, tensile strength and permeability, however opacity was not affected. Depending on filler and CNF levels, adding CNF to GCC produced the most beneficial effects on paper properties; CNF had a lower impact on dewatering times and permeability and GCC reduced strength less than for competing strategies. Adding CNF to LFF produced the least beneficial results using the same metrics. Scanning electron microscopy (SEM) analysis of the sheets reveal that sheets produced using the different strategies are structurally different; adding CNF and retention chemicals to GCC appears to have increased GCC clustering, whereas adding CNF and retention chemicals to LFF appears to have increased the fraction of GCC adsorbed on the fiber walls. CNF and retention chemical addition to complete furnish showed GCC clustering and adhering to the fiber walls, of which clustering appeared the most common

The formation and characterization of sustainable layered films incorporating Microfibrillated Cellulose (MFC)

Microfibrillated cellulose (MFC), TEMPO-pretreated MFC, and hybrid polymer/MFC mix were used for the production of layered films with interesting properties for application in food packaging. The series of samples were prepared from MFC (base layers) using a dispersion-casting method. The same procedure as well as a bar coating technique was applied to form top layers of different basis weights. The barrier properties and formation of the layered films were investigated in relationship to the preparation procedures, combination of layers, and areal weight (basis weight). Characterization was done with respect to oxygen transmission rates (OTR), water vapor transmission rates (WVTR), tensile properties, and contact angles (CA) with water. The produced layered films yielded OTR values of 4 mL m-2 day-1 and fulfilled oxygen barrier requirements for a modified atmosphere packaging (MAP). Hornification of the MFC films, however, occurred during drying, which may result in a loss of the film’s beneficial properties.publishedVersio

Thermal oxidation of polyolefins by mild pro-oxidant additives based on iron carboxylates and lipophilic amines: Degradability in the absence of light and effect on the adhesion to paperboard

Marine and inland pollution by non-degradable plastic bags and other plastic articles is a topic of great concern. Natural degradation processes based on oxidation of plastic pollutants could possibly contribute to limit the extent of pollution. Thermal degradation of polyolefins in the absence of light by non-polluting pro-oxidants has not been presented before. In this study, we show that two amines, stearyl amine and [(3-(11-aminoundecanoyl) amino) propane-1-] silsesquioxane (amino-POSS) in combination with ferric stearate (FeSt3) tremendously accelerate the thermal oxidation of polyolefins compared with reference samples. Both amines and FeSt3 are to a large extent based on renewable resources. Polyethylene and polypropylene samples containing less than 100 ppm of iron and 1% of amine were extremely brittle after 10 days in a circulation oven in the absence of light. No significant degradation could be seen with samples containing iron but no amine. In a different application, the initial oxidation of polyethylene can be used in order to increase its adhesion to cardboard. Excellent adhesion between polyethylene and cardboard is important for liquid packaging based on renewable resources. Amino-POSS has been chosen for food packaging applications due to its expected lower leakage from polyethylene (PE) compared with stearyl amine. Film samples of PE/amino-POSS/FeSt3 blends were partly oxidized in a circulation oven. The oxidation was documented by increased carbonyl index (CI) and melt flow index (MFI). The limited extent of oxidation has been proved by unchanged tensile strength and only moderate changes in elongation at break when compared to reference polyethylene films containing no FeSt3 or amino-POSS. The PE/amino-POSS/FeSt3 blends were compression moulded to paperboard. The adhesion of non-aged blends to paperboard decreased with increasing amino-POSS content which is in good compliance with an earlier reported lubricant effect of high amounts of POSS in PE. Thermal ageing of PE/amino-POSS/FeSt3 films prior to coating however led to a significant increase in adhesion. Improved physical interlocking due to increased MFI and interaction between C=O of the blends and OH of paperboard can explain the adhesion improvement. The films were not brittle after thermal ageing, which makes their use in industrial packaging feasible. A mechanism explaining the role of amines during thermal oxidation of polyolefins in the presence of iron is proposed

Mechanical, thermal and swelling properties of cellulose nanocrystals/PVA nanocomposites membranes

Cellulose nanocrystals (CNC) have strong reinforcing properties when incorporated in a compatible polymer matrix. The study was conducted to investigate the effect of addition of different proportions of CNC on the mechanical, thermal and swelling properties of poly(vinyl alcohol) (PVA) nanocomposite membranes for biogas separation. The incorporation of CNC in PVA increased the crystallinity at all investigated relative humidities. No apparent trend is observed for mechanical properties for dry membranes (0% RH) with addition of CNC in PVA matrix. However, at 93% RH the elastic modulus increased 25 times with addition of CNC compared to pure PVA membranes. Moreover, tensile strength also showed twice the values at 53% RH and 93% RH after the addition of CNC. Membranes containing higher CNC content absorbed 9% less moisture. Swelling, thermal and mechanical properties indicate a good potential of CNC/PVA nanocomposite membranes for use in CO2 separation membranes

Cellulose nanocrystal/PVA nanocomposite membranes for CO2/CH4 separation at high pressure

Biogas can be used as an alternative energy source in place of conventional fossil fuels. However, for this to happen, it is necessary to optimize biogas production as well as improve the biogas quality. Crystalline nanocellulose (CNC) has excellent mechanical properties as well as a high moisture uptake ability. These properties make CNC a promising candidate to be used as an additive in polyvinyl alcohol (PVA)-facilitated transport membranes (FTMs). The overall objective of this work is to develop CNC/PVA nanocomposite membranes for enhancing the biogas quality through CO2 capture. The effects of CNC concentration and the pH of the casting solution are investigated to optimize CO2/CH4 separation. Membrane characterization shows that the addition of CNC affects the degree of swelling, crystallinity and thickness of the resulting membranes, while permeation testing showed that the permeance and selectivity for CO2 increased with the addition of CNC. Membranes produced with 1% CNC and a casting suspension at pH 10 gave the best results under the given set of conditions. The maximum permeance achieved by the formulated nanocomposite membranes was 0.29 m3(STP)/(m2-h-bar), while the selectivity of CO2 over CH4 was 43. It was also observed that increasing the feed gas pressure deteriorated the membrane performance

Decoupling the effect of membrane thickness and CNC concentration in PVA based nanocomposite membranes for CO2/CH4 separation

The effect of the viscosity of the casting suspension on membrane morphology and thickness has been investigated for polyvinyl alcohol (PVA)/crystalline nanocellulose (CNC) nanocomposite membranes used for CO2/CH4 separation. Different concentrations of CNC suspended in dissolved PVA affected the viscosities of resulting suspensions. A methodology was developed to make equal viscosity suspensions with variable CNC content. SEM micrographs show that by increasing the concentration of CNC in PVA, the thickness of the selective layer increased. However, equal thickness was achieved by water dilution for viscosity adjustment. The overall objective of this work was to find the real optimum concentration of CNC in PVA for CO2/CH4 separation independent of the membrane thickness. Furthermore, the effect of the relative humidity (RH) and feed pressure on the selectivity and permeability of the membranes were also investigated as part of this study. For 1.5% CNC in PVA with pH 9 in the casting suspension, tested at feed pressure of 5 bar, CO2/CH4 selectivity was up to 39 and the achieved permeance was 0.27 m3 (STP)/(m2 h bar). Above this concentration of CNC, the CO2 permeation and selectivity decreased. It was also observed that increasing pressure caused a decrease in the performance of the membranes for CO2 capture in terms of both permeation and selectivity. Moreover, increasing RH causes increasing in CO2 permeation and selectivity

Mechanical properties of cellulose nanofibril films: effects of crystallinity and its modification by treatment with liquid anhydrous ammonia

The influence of cellulose crystallinity on mechanical properties of cellulose nano-fibrils (CNF) was investigated. Degree of crystallinity (DoC) was modified using liquid anhydrous ammonia. Such treatment changes crystal allomorph from cellulose I to cellulose III, a change which was reversed by subsequent boiling in water. DoC was measured using solid state nuclear magnetic resonance (NMR). Crystalline index (CI) was also measured using wide angle X-ray scattering (WAXS). Cotton linters were used as the raw material. The cotton linter was ammonia treated prior to fibrillation. Reduced DoC is seen to associate with an increased yield point and decreased Young modulus. Young modulus is here defined as the maximal slope of the stress–strain curves. The association between DoC and Young modulus or DoC and yield point are both statistically significant. We cannot conclude there has been an effect on strainability. While mechanical properties were affected, we found no indication that ammonia treatment affected degree of fibrillation. CNF was also studied in air and liquid using atomic force microscopy (AFM). Swelling of the nanofibers was observed, with a mean diameter increase of 48.9%

Some factors affecting the grades of technology students

In this study factors that affect the grades of Norwegian technology students have been investigated. The total data set contained 355.706 individual exams from 63 different engineering master programs during the 2010 to 2014 period. Regression analysis showed that the single factor having the largest impact on students’ grades at university was their average grade from high school. Students who had on average one unit better grade from high school got on average 1.4 to 1.7 units better grades in the first year at university and even on their master thesis they got 0.76 units better grades. Strong correlations in the awarded grades for single students were also observed between the different years of five-year integrated study programs. These findings show that the universities are consistent in the evaluation of the student’s work. When we adjusted for the effect of grades received in high school and earlier stages of university studies, we still found significant variation between study programs on how the master thesis were graded. The effect was as high as 0.4 grade units away from the average level. Such differences may both be explained by local cultures in grading, but could also reflect the quality of the student supervision during the master thesis work. In 2014 new grade descriptions was implemented in the STEM area and new instructions distributed to the examiners. A significant reduction in the average grade was found, but the effect was not strong, only -0.14 grade units

Some factors affecting the grades of technology students

publishedVersio