Studies on the quality of feed stock and performance of agriculture roller mill using roller coated with nano-clay epoxy composite

Studies on the quality of feed stock and performance of agriculture roller mill using roller coated with nano-clay epoxy composite

The roller milling machine is one of the most common machines used to process animal feedstock. The rollers in milling machines are made of mild steel. Recently, polymers have become a very attractive candidate as an alternative to the conventional metallic materials. Metal rollers, when used in milling equipment, have inherent issues, some of which may be overcome by coating them with a polymeric layer. The primary objective of this study is to investigate the potential for coating the metal rollers in agricultural milling machines with a polymeric layer using epoxy material with nano-clay additives to improve the quality of the milled product and milling performance. This work is divided into two stages: In stage 1, the main important mechanical properties that is compatible with the main forces in roller milling machine when nano-clay epoxy composite is used as a coating layer for rollers surfaces. A compressive testing of sorghum seeds was used to determine the maximum load for seed breakage and changing morphology. The compressive test of different percentages of nano-clay epoxy composites was tested as well. Also, tensile testing was conducted for adhesive mild steel single lap joints using an epoxy resin with different concetreations of nano-clay additives. Moreover, the compressive load of sorghum seeds on nano-clay epoxy composite materials as a coated layer over mild steel material was tested. These tests were performed on different percentages of nano-clay additives with epoxy starting from (0, 1, 2, 3, 4 and 5wt. %). Tribological tests were also used to study the effect of different loads and particle sizes as a three body abrasive (3BA) with epoxy and polyester by using block on ring technique. Optical microscopy and scanning electronic microscopy (SEM) was used for all Stage 1 experiments to study the morphological change in the surface of the materials.

In this stage, the results revealed that fluctuating loads were recorded as a result of the nature of the sorghum seeds and the different fracture mechanism observed. Stress increased with a reduction in strain rate in compression test as the nano-clay proportion increased in the epoxy material with greater fracture mechanism. In single lap joints testing of two weight percentage of nano-clay epoxy composite with mild steel, the tensile loading of the composite was shown to be enhanced and the fracturing mechanism was shown to be reduced. This performance was superior to all other nano-clay percentages. The rollers coated layer with two weight percentage of nano-clay epoxy composite coating over mild steel material recorded an acceptable deformation and less fracturing compared with other proportional nano-clay with epoxy material when compressed by sorghum seeds. For the tribology tests, the epoxy material revealed a lower wear rate and fracture mechanism compared to polyester material when epoxy and polyester were tested under different loads and sizes of abrasive particle.

In Stage 2, (0wt. %) of nano-clay in epoxy matrix and the optimum percentage of nano-clay epoxy composite (resulting from Stage 1) was used as a coating material for mild steel rollers in a milling seed machine. The study investigated the influence of the coating process on the surface characteristics of the roller corrugation in terms of roughness profile and its effect on feedstock quality (physical properties of milled sorghum seeds), and milling performance (bulk density, power consumption and production rate). These composites, as a coated layer, were examined with a roller milling machine under two types of coated materials (0wt. % and 2wt. % nano-clay epoxy composite), three levels of roller speed (533, 777 and 980 rpm) and five levels of roller gaps from (0.25 – 0.35 mm) to (0.65 – 0.75 mm). The results were compared with the uncoated rollers under the same parameters. In addition, statistical analysis was performed, using SAS software, to determine the significance of the operating parameters and their impact on the quality of the milled feedstock and milling performance. After testing, scanning electron microscopy (SEM) was used in (Stage 2) to examine the fracture mechanism of the sorghum.

The roughness of the roller surface was enhanced with epoxy coating with (0wt. %) or (2wt. %) of nano-clay epoxy composite compared to uncoated rollers before and after milling. In addition, the results showed that (2wt. %) of nano-clay epoxy composite gave an improved results in geometric mean diameter, specific surface area increase and the number of particles, as well as enhanced bulk density with a reduction of the production rate with an increase in power consumption compared with rollers coated with (0wt. %) of nano-clay epoxy composite and the uncoated rollers. Moreover, the rollers coated with (2wt. %) of nano-clay epoxy composite generated brittleness behaviour fracture of crashed sorghum seeds as well as less distortion compared to (0wt. %) of nano-clay composite due to presence of nano-clay particles which was the reason for high good quality feedstock and improvement in milling performance. Epoxy material with (2wt. %) of nano-clay improved the feedstock quality of milled sorghum when used as a coated layer on roller surfaces due to its remarkable mechanical properties (compression testing, tensile testing as a adhesion material, resistance to fracture as a coated layer on mild steel when compressed by sorghum seeds and in tribology testing) and contributed to changing the main dimensions of the corrugations in the rollers.