Creep and shrinkage behavior of improved ultrathin polymeric films

Abstract

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.

Viscoelastic characteristics of magnetic tapes with PEN substrates

“…TTS has been used in past research to predict longterm creep behavior at ambient temperature. [7][8][9]11 This analytical technique utilizes creep measurements at elevated temperature levels to predict behavior at longer time periods. In this research, data sets acquired at 30, 50, and 70…”

“…Jeong et al 14 also measured the b* relaxation in PEN and attributed this relaxation to out-of-plane motion of the naphthalene rings or their aggregates, and Higashioji and Bhushan 11 have noted this mechanism as a major contributor to creep behavior of PEN film in the À20 to 80 C range. They also noted that Gillmor and Green 15 suggested an interlayer slippage mechanism for the naphthalene rings.…”

Creep anomaly in electrospun fibers made of globular proteins

“…In contrast, viscoelastic polymers undergo creep, a timedependent viscoplastic response, in which molecular motion (reptation) results in monotonic elongation of the material over time [1][2][3]. A material's creep response can be dictated by specific structural features (e.g., degree of polymer matrix heterogeneity) and presents a great challenge in engineering applications, where designers try to increase the creep resistance of polymers [4,5] and composite materials [6][7][8][9]. In biopolymers [10], biofibers [11], and soft biological tissues [12], creep response may indicate structural and biochemical changes [13].…”

Modeling of creep and shrinkage behavior of polymeric films used in magnetic tapes

“…Crystallization occurs during the drawing and heat‐setting processes at a temperature above the T g of the film. The typical crystallinities in PET and PEN films are 40–50% and 30–40%, respectively 3. The crystalline and amorphous structure of the film is highly oriented along the direction of higher draw ratio [as shown in Fig.…”

“…To minimize stretching and damage during use, the substrates should be a high‐modulus and high‐strength material with low creep and shrinkage characteristics. If the substrates creep or shrink a lot, then long‐term reliability problems are encountered, and thus it is required to minimize these deformations 1, 3, 4…”