Evaluation of Used Milking Machine Inflations
Synthetic Rubber v. Silicone Rubber
By Dr. Richard Heckmann

Objective:
Analyze the surface of two types of milking machine inflations; one composed of silicone rubber and the second a synthetic rubber following use. The silicone rubber inflation had been used for approximately 6,000 cow milkings while the formulated rubber product had been used for 1,200 cow milkings.

Duplicate samples of each were attached to specimen studs, coated with gold in a mini-coater sputter apparatus and viewed with a high resolution scanning electrom microscope (SEM) for accurate evaluation of the inflation surface. The SEM was operating at 5 KV and representative pictures were taken at 2200x, 600x, and 220x for both specimens and viewed at other magnifications. Permanent records were recorded on the micrographs with a digital data keyboard entry system attached to the SEM. An X-ray microprobe scan (EDAX) was completed on each sample to determine elemental composition. The EDAX unit is attached to the SEM.

Results: (figures shown below)
Figures 1 to 10 represent the results of the SEM and X-ray probe scans of the two types of inflations for cow milking machines. Figure 1A, 1B, and 1C represent scanning electron micrographs taken at three magnifications; 220x, 600x, and 2200x of the surface of the used (1200 cow milkings) formulated rubber milking machine inflations. Note the deep cracks and depressions (arrows) in the surface of the inflation that could harbor harmful virus and disease causing bacteria. The size of the cracks and spaces can be measured using the micron bar (100, 50, 10 µm) at the right hand side of the caption. These pictures were prepared using an SEM at 5 kv. Following the 1A, B, C micrographs are the "full page" prints of the preparation. Figures 2A, 2B, and 2C represent another sample from the same set of inflations as used for 1A, 1B, and 1C. Bacteria are visible for 2C. Again the full page prints follow the composite represented by 2A, 2B, and 2C.

The silicone rubber inflations are represented by Figure 3A, 3B, and 3C with the second sample labeled 4A, 4B, and 4C. The second series (4A, 4B, and 4C) are highly representative of the inflation surface after extensive use. This inflation had been used for 6,000 cow milkings and showed no cracks, depressions, or tears. Appeared similar to when it was formulated and extruded. The full page SEM micrographs following the composite for each sample. Three magnification levels were used again; 220x, 600x, and 220x with a 5 kv operating voltage. The next series, 5A, 6A, 7A, represent a comparison between the two inflations. Figure 5A and 5B are at 220x magnification with 5A representing formulated rubber and 5Bsilicone rubber. Note the difference in the number of breaks and depressions in the surface of the two products. Figures 6A and 6B represent 600x magnification while 7A and 7B represent 2,200x magnification. As was the case for Figures 5A and 5B, the A figure is formulated rubber while B is silicone rubber.

Summary:
Results of this project show that a silicone rubber inflation is much better than a formulated synthetic rubber inflation even after 5 times more cow milkings. The surface of formulated rubber inflation after 1,200 cow milkings is riddled with cracks, holes, and depressions. The "breaks" in the rubber inflation can harbor harmful bacteria and alter microorganisms as well as chemicals used in udder washes.

Based on these data, the silicone rubber inflation is the best product.

References:
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