Weld line morphology of injection molded polypropylene

The weakness of plastics at weld lines provides serious difficulties for the design and long term durability of injection molded parts. The goal of this work was to identify the cause of weld line weakness in polypropylene (PP) systems. The morphology of weld lines in a high molecular weight PP has been studied. It was found that the PP contains a hindered phenolic antioxidant additive that is not soluble in the polymer at the standard processing conditions. Transmission electron microscopy (TEM) pictures reveal the additive existing as a dispersed phase in the bulk polymer. Even though very small concentrations of this additive are normally used, (0.1–0.5%) large quantities were found at weld lines in a band approximately 100 nm wide and penetrating about 10 μm into the surface of the part, hindering strength development at the weld line. X-ray photoelectron spectroscopy (XPS) results confirm enhanced concentrations of antioxidant on the flow front and mold wall surface of short shot samples. The mechanical properties (Izod impact, tensile strength) are measured for samples molded at various processing conditions, varying amounts of antioxidant additive and with and without weld lines. The results are consistent with the presence of the additive playing a key role in strength development at PP weld lines.     

International trade of animal feed: its relationships with livestock density and N and P balances at country level

International trade of food and feed has facilitated the specialization and agglomeration of agricultural production systems in many countries. Confined animals in specialized production systems are increasingly supplied with soybean and maize, imported from other countries. This has increased animal productivity but has also contributed to spatially decoupled crop and animal production systems. We analyzed the changes in the trade of soybean and maize at the global level in the period 1961–2011, and related these to the changes in livestock density and nutrient balances in the whole food system for 11 selected countries. Export of soybean and maize remained dominated by few countries (mainly USA, Argentina and Brazil) during the period 1961–2011, while the number of importing countries increased. Increases in the import of maize and soybean are positively related with changes in livestock density and N and P balances of national food systems. Imported soybean accounted for 12–36% of the calculated N balance at country level, and imported maize for 0–26%. There were large differences between importing countries; increases in the N surplus ranged from 75 to 306 kg N/ha and in the P surplus from 2 to 49 kg P/ha when the mean livestock density increased 1 LU/ha. This variation is related to differences in nutrient management regulations and to spatial variations in livestock density within countries. Our study contributes to the understanding of the complex relationships between the international trade of animal feed, livestock density and environmental impacts associated with N and P balances.     

Nitrogen excretion factors of livestock in the European Union: a review

Livestock manures are major sources of nutrients, used for the fertilisation of cropland and grassland. Accurate estimates of the amounts of nutrients in livestock manures are required for nutrient management planning, but also for estimating nitrogen (N) budgets and emissions to the environment. Here we report on N excretion factors for a range of animal categories in policy reports by member states of the European Union (EU). Nitrogen excretion is defined in this paper as the total amount of N excreted by livestock per year as urine and faeces. We discuss the guidelines and methodologies for the estimation of N excretion factors by the EU Nitrates Directive, the OECD/Eurostat gross N balance guidebook, the EMEP/EEA Guidebook and the IPCC Guidelines. Our results show that N excretion factors for dairy cattle, other cattle, pigs, laying hens, broilers, sheep, and goats differ significantly between policy reports and between countries. Part of these differences may be related to differences in animal production (e.g. production of meat, milk and eggs), size/weight of the animals, and feed composition, but partly also to differences in the aggregation of livestock categories and estimation procedures. The methodologies and data used by member states are often not well described. There is a need for a common, harmonised methodology and procedure for the estimation of N excretion factors, to arrive at a common basis for the estimation of the production of manure N and N balances, and emissions of ammonia (NH₃) and nitrous oxide (N₂O) across the EU. © 2015 Society of Chemical Industry     

P-equilibrium fertilization in an intensive dairy farming system: effects on soil-P status,crop yield and P leaching

In the coming decade, European dairy farms are obliged to realize a balance between phosphor (P) inputs to their farmland (in inorganic fertilizers and manure) and outputs (in crop products), the so-called P-equilibrium fertilization. The objective of the present study is to analyze the long-term effects of P-equilibrium fertilization on soil-P status (total soil-P and available soil-P), crop yield and P leaching on dry sandy soil, using data from experimental dairy farm ‘De Marke’, where P-equilibrium fertilization has been applied since 1989. For grassland, P availability is expressed in P-Al and for arable land in Pw. Total and available P status were monitored in the upper topsoil (layer 0–0.2 m). Total soil-P was also monitored in the lower topsoil (layer 0.2–0.4 m) and in the subsoil (0.4–0.6 m). From 1989 to 2006, Pw and P-Al (means of all farmland) decreased by 26 and 25%, respectively. In the same period, mean total-P content of the farmland decreased by 16%. There was a large variation in initial P status (1989) of the various plots. The rate of decline in all soil-P indicators was positively correlated to their initial values. In plots with the lowest initial values, P status did not change, while in plots with high initial values it tended to stabilize at lower levels. At equilibrium-P fertilization, Pw is estimated to stabilize at 20. This is lower than the recommended P status of Dutch soils used for maize cropping. P-Al is estimated to stabilize at 30–40, which corresponds to the current recommendations for grassland. The data show that at P-equilibrium fertilization, soil available-P status is higher in a maize-ley rotation than in permanent grassland. The decline in total P and available P did not affect crop yield, nor did it affect the P concentration in groundwater, but at ‘De Marke’, P emission to groundwater is generally low. The results obtained suggest that P-equilibrium fertilization can be compatible with efficient crop production.     

Rational rotation functions and the special points of rational algebraic motions in the plane

For any given motion, there may be special points which generate trajectories which differ from the trajectory of a generic point of the plane. We first extend previous results on kinematic mappings to include rotation functions which are ratios of two polynomials, then we develop a classification of the special points of all rational algebraic planar motions. A theorem is derived which relates the number of special points to the characteristics of the rotation curve and the rotation functions of the motion. A procedure and formulas for determining these points are given, and several examples are presented showing how to determine these special points.     

Polysulphone and poly(phenylene sulphide) blends: 2. Mechanical behaviour

This paper reports the mechanical behaviour of injection moulded blends of polysulphone (PSF) and poly(phenylene sulphide) (PPS). The blends prepared by melt-extrusion and subsequent injection moulding are phase separated. Depending on moulding conditions, thermal history, and composition, tensile behaviour ranged from brittle to ductile, with or without cold drawing. Cold drawing was observed in compositions as-moulded with up to 50% by weight PPS. Upon annealing for 2h at 160°C, ductile failure was maintained for blends containing up to 35% by weight PPS. All other compositions failed in brittle fashion. Flexural strength and modulus, before and after annealing, exhibited negative deviation from the rule of mixtures. All the blends were found to be notch sensitive.     

Calculated rates of soil acidification of intensively used grassland in the Netherlands

The major processes involved in acidification of soils under intensively managed grassland are the transformation and subsequent leaching of applied nitrogen (N), assimilation of excess cations in herbage and acidic atmospheric deposition. Carbonates from fertilizers and excess cations in purchased concentrates are the most important proton (H⁺) neutralizing agents applied to grassland. In this study, the effects of grazing, cutting and N application on the net proton loading from each of the main processes were calculated, using a simple model.On mown swards, simulated excess cation uptake by the sward released 4.5–9.3 kmol_c H⁺ ha^–1 yr^–1. The total proton loading on mown grassland decreased from about 8.0 to 5.3 kmol_c ha^–1 yr^–1 when fertilizer N input as CAN-27 increased from 0 to about 400 kg ha^–1 yr^–1. Contributions from atmospheric deposition ranged from 2.2 kmol_c ha^–1 yr^–1 when herbage yield exceeded 10 Mg ha^–1 yr^–1 to 3.0 kmol_c ha^–1 yr^–1 when herbage production was only 5.5 Mg ha^–1 yr^–1.On grazed swards, transformation of organically bound N from urine and dung to nitrate (NO ₃ ^- ) and the subsequent leaching of excess NO ₃ ^- was the main source of protons. Application of 400 kg N ha^–1 yr^–1 to grazed swards increased the proton loading from transformed N from 3.9 to 16.9 kmol_c ha^–1 yr^–1. The total proton loading on grazed swards exceeded that of mown swards when the input of fertilizer N exceeded 150 kg ha^–1 yr^–1.Underestimation of the amount of N immobilized in the soil biomass and lost by denitrification may have resulted in a slight overestimation of the amount of N lost by leaching and thereby also the simulated total proton loading.     

Efficiency, economics, and environmental implications of phosphorus resource use and the fertilizer industry in China

Phosphorus (P) is an essential nutrient for crop production and is often in short supply. The necessary P fertilizers are derived from deposits in the lithosphere, which are limited in size and nonrenewable. China is one of the world’s largest consumers and producers of P fertilizers. Thus, P resource use efficiency in China has an important impact on the worldwide efficiency of P resource use. This study examined the P fertilizer industry in China in terms of P resource use efficiency, economics, and environmental risk, and explored options for improvement through scenario analysis. P resource use efficiency decreased from a mean of 71% before 1995 to 39% in 2003, i.e., from every 10 kg P in rock material, only 3.9 kg P was used to produce fertilizer, 5.6 kg of the residues were discarded at the mining site, and 0.5 kg was manufacturing waste. The decreased efficiency was caused by increased P rock mining activities, especially from small, inefficient miners. Enhanced mining was supported by local governments and by the growing P fertilizer industry, where high-analysis P fertilizers have fourfold higher gross margins than traditional low-analysis fertilizers. Although the growing fertilizer industry is contributing significantly to the development of some regions, the economic efficiency is still lower than in other countries, e.g., in the USA. The P resource is depleting quickly, and the environmental consequences of inefficient use are serious. The amount of accumulated phosphor gypsum was estimated to be 110 Tg, the amount of deteriorated land reached 475 km², and the consumption of ground water was 1.8 billion m³ per year. The low efficiency and serious environmental risk could be attributed to the numerous small inefficient miners, which were supported by intervention of governmental subsidies and taxes after 1995. This study proved that there is a great deal of room for improvement in the resource use efficiency up to 77% by integrated measures, which need broad cooperation of miners, fertilizer plants, and agriculture.     

Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle

In 1995 a working group was assembled at the request of OECD/IPCC/IEA to revise the methodology for N₂O from agriculture for the National Greenhouse Gas Inventories Methodology. The basics of the methodology developed to calculate annual country level nitrous oxide (N₂O) emissions from agricultural soils is presented herein. Three sources of N₂O are distinguished in the new methodology: (i) direct emissions from agricultural soils, (ii) emissions from animal production, and (iii) N₂O emissions indirectly induced by agricultural activities. The methodology is a simple approach which requires only input data that are available from FAO databases. The methodology attempts to relate N₂O emissions to the agricultural nitrogen (N) cycle and to systems into which N is transported once it leaves agricultural systems. These estimates are made with the realization that increased utilization of crop nutrients, including N, will be required to meet rapidly growing needs for food and fiber production in our immediate future. Anthropogenic N input into agricultural systems include N from synthetic fertilizer, animal wastes, increased biological N-fixation, cultivation of mineral and organic soils through enhanced organic matter mineralization, and mineralization of crop residue returned to the field. Nitrous oxide may be emitted directly to the atmosphere in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff. Nitrate leaching and runoff and food consumption by humans and introduction into sewage systems transport the N ultimately into surface water (rivers and oceans) where additional N₂O is produced. Ammonia and oxides of N (NO_x) are also emitted from agricultural systems and may be transported off-site and serve to fertilize other systems which leads to enhanced production of N₂O. Eventually, all N that moves through the soil system will be either terminally sequestered in buried sediments or denitrified in aquatic systems. We estimated global N₂O–N emissions for the year 1989, using midpoint emission factors from our methodology and the FAO data for 1989. Direct emissions from agricultural soils totaled 2.1 Tg N, direct emissions from animal production totaled 2.1 Tg N and indirect emissions resulting from agricultural N input into the atmosphere and aquatic systems totaled 2.1 Tg N₂O–N for an annual total of 6.3 Tg N₂O–N. The N₂O input to the atmosphere from agricultural production as a whole has apparently been previously underestimated. These new estimates suggest that the missing N₂O sources discussed in earlier IPCC reports is likely a biogenic (agricultural) one.     

Controlling nitrous oxide emissions from grassland livestock production systems

There is growing awareness that grassland livestock production systems are major sources of nitrous oxide (N₂O). Controlling these emissions requires a thorough understanding of all sources and controlling factors at the farm level. This paper examines the various controlling factors and proposes farm management measures to decrease N₂O emissions from intensively managed grassland livestock farming systems. Two types of regulating mechanisms of N₂O emissions can be distinguished, i.e. environmental regulators and farm management regulators. Both types of regulators may influence the number and size of N₂O sources, and the timing of the emissions. At the field and farm scales, two clusters of environmental regulating factors have been identified, i.e. soil and climate, and three levels of management regulators, i.e. strategic, tactical and operational. Though the understanding of these controls is still incomplete, the available information suggests that there is large scope for diminishing N₂O emissions at the farm scale, using strategies that have been identified already. For example, model calculations indicate that it may be possible to decrease total N₂O emissions from intensively managed dairy farms in The Netherlands in the short term from a mean of about 19 to about 13 kg N per ha per year by more effective nutrient management, whilst maintaining productivity. There is scope for a further reduction to a level of about 6 kg N per ha per year. Advisory tools for controlling N₂O emissions have to be developed for all three management levels, i.e. strategic, tactical and operational, to be able to effectively implement emission reduction options and strategies in practice. Some strategies and best management practices to decrease N₂O emissions from grassland livestock farming systems are suggested.