Variation in Rubber Chemistry and Dynamic Mechanical Properties of the Milking Liner Barrel with Age

Variation in liner barrel length (% of original length) with age (number of milkings); Δ = before tensioning; × = after tensioning.

Variation in proportion of weight (%) of the dioctyl phthalate (DOP) plasticizer, the N′-1,3 dimethylbutyl-N′ phenylpara-phenylene diamine antidegradent (6PPD), and milk-derived products (MDP) along the length of the liner after 2,500 milkings. The area 40 to 60mm below the mouthpiece is the part that wraps around the teat end during liner collapse.

Variation in a) calcium content (%) and b) phosphate content (%) with liner length after 4,000 milkings determined by energy dispersive x-ray spectrometry.

Variation in a) ratio of P to Ca and b) sulfur content (%) with liner length after 4,000 milkings determined by energy dispersive x-ray spectrometry.

Scanning electron micrographs of a) liner surface showing the calcium/phosphate deposits 30mm from the top of the liner (bar = 100μm) and b) liner surface showing calcium/phosphate deposits 100mm from the top of the liner after 4,000 milkings (bar = 100μm).

Mass uptake (change in mass from original) of butterfat by unused liner rubber in vitro at 20, 35, and 85°C over time.

Mass uptake (% mass change) of butterfat by 3 different acetylonitrile compound liners (A, B, and C) at 70°C over time.

Tensile behavior of new (0 milkings) and used (4,400 milkings) liners.

Variation in elastic modulus (E) and hysteresis (tan delta) of unused liner rubber for strain sweeps (% double-strain amplitude, DSA) at 10Hz and 40°C determined by dynamic mechanical thermal analysis.

Variation in rubber stiffness (E) along the barrel for liners of different age at 10Hz and 40°C determined by dynamic mechanical thermal analysis on rubber with 0.5mm of the inner rubber surface removed.

Variation in rubber stiffness (E) along the barrel of a liner (distance from mouthpiece) used for 4,000 milkings relative to a new liner (value = 100) determined by dynamic mechanical thermal analysis.

Variation of liner rubber stiffness (E) and loss modulus (E″) with temperature; strain 0.13% determined by dynamic mechanical thermal analysis.

Model of forces imposed on the teat considering the liner as a membrane; R1 = radius of the teat apex; R2 = radius of collapsed liner on teat.