Long‐term mechanical and viscoelastic behavior of constitutive polymeric materials used for magnetic tapes

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Viscoelastic characteristics of magnetic tapes with poly(ethylene naphthalate) substrates were studied using experimental techniques. Measurements were made using samples cut from commercially available tapes, and solvents were used to remove front and/or back coat layers to obtain substrates and dual-layer samples. Experimental results allowed for fundamental compliance and viscosity parameters to be determined using a Kelvin-Voigt model. Rates of creep-compliance were also predicted, and comparisons were made with results for tapes that used poly(ethylene terephthalate) and aromatic poly(amide) substrates.Dynamic mechanical analysis (DMA) was used to help make correlations between viscous characteristics measured from the creep-compliance results and molecular characteristics of the substrates. Time-temperature superposition (TTS) was used to predict creep-compliance over extended time periods, and a rule-of-mixtures method was used to predict the compliance of constitutive layers.

“…[6][7][8] The procedure calls for the magnetic tape to be modeled as a multiple layer polymer composite laminate as shown in Figure 4.…”

Section: Viscoelastic Analysis Methodsmentioning

confidence: 99%

Section: Experimental and Analytical Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Viscoelastic characteristics of magnetic tapes with PEN substrates

Weick

2008

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“…1,4 -9 This includes the creep, shrinkage, and dynamic behavior analysis of polymeric substrates, tapes, and stripped tapes (without back coating). Weick and Bhushan 8,9 modeled the magnetic tape as a three-layer composite: front layer, substrate, and back coat. By applying the rule of mixtures, the viscoelastic behavior of each individual layer was obtained, and the strain distribution was predicted through the thickness of the tape.…”

Section: Introductionmentioning

confidence: 99%

Technique development and measurement of Poisson's ratio, lateral creep behavior, and thermal and hygroscopic expansion of individual layers in magnetic tapes

Bhushan

2003

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An experimental technique was developed to measure the Poisson's ratio (lateral contraction over longitudinal elongation), lateral creep, and both thermal and hygroscopic expansion of thin polymeric films. A so-called profile-matching method was developed to measure the lateral and longitudinal deformation with the help of a laser scan micrometer. A thermomechanical analyzer was used to measure the coefficient of thermal expansion (CTE). The laser scan technique was also used to measure the coefficient of hygroscopic expansion (CHE). The measurements were performed on magnetic tapes, substrates, and tapes with front coat or back coat, or with both coats stripped. A model based on the rule of mixtures was developed to determine the Poisson's ratio, lateral and longitudinal deformation behavior, and thermal expansion of the front coat and back coat. To investigate the mechanical degradation of the substrates during tape manufacturing, the data for substrate with the front and back coats removed from the tape, were compared with the data for the never-coated virgin film. The relationship between the molecular structure and the degradation mechanism of the substrates is discussed. The magnetic tapes used in this research include two metal particle (MP) tapes and two metal evaporated (ME) tapes that use polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates. Longitudinal and lateral deformation tests were performed at 25 Ϯ 0.5°C and 50 Ϯ 2%RH, and thermal expansion was measured from 15 to 70°C. The CHE was measured at 25 Ϯ 0.5°C and 15-80%RH.

Creep and shrinkage behavior of improved ultrathin polymeric films

Higashioji

Bhushan

2002

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Long-term creep-deformation and shrinkage characteristics of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly-(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN), and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes, and thinner tensilized-type PET, PEN, and ARAMID have recently been used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 m. More dimensional stability is required for advanced magnetic tapes, and the study of creep and shrinkage behavior is important for estimating the dimensional stability. Creep measurements were performed on all available substrates at 25, 40, and 55°C for 100 h. Based on these data, master curves were generated using time-temperature superposition to predict dimensional stability after several years. The amount of creep deformation is considerably smaller for ARAMID and tensilized-type PET than for PEN, although Standard PET shows the largest amount of creep. In addition, creep measurements under high humidity also show similar trends. Shrinkage measurements at 55°C for 100 h show that the shrinkage of ARAMID is lower than that of PET and PEN. The relationship between the polymeric structure and dimensional stability are also discussed. Based on the creep and shrinkage behavior, ARAMID and tensilized-type PET seem to be suitable for advanced magnetic tapes.