Weld-lines degrade the mechanical and optical properties of products. This is because the polymer molecules near the weld-line highly orient owing to the elongational flow and the molecular orientation is fixed by solidification of the polymer melts before it returns to a random condition. Birefringence experiments were carried out for welding flows of a low density polyethylene (LDPE) past a spider supporting a mandrel. The die used in the present study has a spider with a glass window. The birefringence in the polymer melts was measured by the photoelastic method. The purpose of the present study is to elucidate the effect of the die temperature, spider shapes and a viscoelastic property of polymer melts on the anisotropy of the molecular orientation in the stress relaxation process downstream of the spider. The birefringence pattern in the welding flow of LDPE was measured at the die temperature T_d=190, 205°C and the polymer melts temperature T_p=190°C for flow rates of 0.7, 1.0, 2.2, 2.9, 4.6 cm³/s. The results showed complete relaxation of birefringence depended on the flow rate. In case that the die temperature was high (205°C), the distance necessary for the relaxation of molecular orientation was short. Moreover, the welding flow was numerically calculated using the single-mode Giesekus model as a constitutive equation, and the results were compared with the experimental data. The numerical predictions agreed with the experimental results.

View full abstract

Swinging track, velocity, and acceleration of a fabric at a turn-round motion were studied precisely with a dynamic drape tester made in trial using moving image processing system. Following conclusions were obtained. (1) Dynamic drape behavior of fabric is explained by some parameters measured by the moving image processing system. (2) These parameters have different information from conventional static drape coefficient, revolving drape increase coefficient, revolving drape coefficient at 200rpm, and dynamic drape coefficient at swinging motion, and have high correlation with fabric bending and shearing vibrational properties. (3) These parameters have strong correlation with subjective value about beautifulness of dynamic drape behaviors of fabrics.

View full abstract