• Elastomers and Composites
• /
• v.49 no.4
• /
• pp.323-329
• /
• 2014

In order to select polymer matrix for MIF (Molded-In Foaming) process, in this study, we investigated rheological properties of commercial polymers, SBC (Styrene-Butadiene Copolymers, K-resin KK38) and SBS (Styrene- Butadiene-Styrene, KTR 101 and KTR 301). In time sweep test, the rheological properties ($G^{\prime}$, $G^{{\prime}{\prime}}$, ${\eta}^*$) of SBS at 155 and $170^{\circ}C$ display almost constant value as a function of time from 0 s to 1800 s. On contrast, the rheological properties of SBS at 185 and $200^{\circ}C$ exponentially increase as a function of time. It could be due to gelation of SBS at high temperature conditions. These increment of rheological properties are not observed in SBC. From LAOS (large amplitude oscillatory shear) test, the nonlinear rheological properties of SBS at 155 and $200^{\circ}C$ after 1800 s are compared. The nonlinear rheological properties at $155^{\circ}C$ show simple strain thinning behavior such as linear homopolymer, however, the nonlinear rheological properties at $200^{\circ}C$ show 2 times strain thinning behavior (Payne effect). It well match with the gelation of SBS at $200^{\circ}C$. From rheological studies, it is confirmed that the proper polymer matrix for MIF process (low rheological properties at initial time and high rheological properties after process) is SBS KTR 301.

• Elastomers and Composites
• /
• v.51 no.1
• /
• pp.24-30
• /
• 2016

Sole in the footwear usually modified with foaming agent on the polymer resin to improve the lightweightness and crush-cushion effect. In this study, we investigated rheological properties for polymer resin filled with the different type and concentration of foaming agent, capsule type foaming agent and organo-chemical foaming agent, under the time sweep test. Curing times of each polymer resin with different kind of foaming agent are delayed than reference material (epoxy resin with curing agent). In case of adding capsule type foaming agent, however, there is appropriate concentration to reduce the curing time, relatively. When foaming agent is activated, foaming force inflates the sample in contrast to condensation force of curing and then axial normal force develop to the (+) direction. Interestingly, by increase concentration of foaming agent, there is a specific point to break down the axial normal force development. The reason for this phenomenon is that coalescence of foams induce the blocking of axial normal force development.