Shrink force

A drop of water in a body of oil will take the shape which gives the least surface area—this is a sphere. Further, the water drop will squeeze itself in as tightly as possible to reduce its size and therefore its surface as much as possible. The measure of this drop shrinking force is called surface tension... 

Pressure, P, with coaxial forces acting inwards by the shrinking force, Fs, of the SMP strip as shown in Figure 1.7 can be estimated as... 

Handling systems are not able to pick out parts which shrink on the mold cores at high-shrinking forces. Stripper plates are used more and more for this job. During the drop-out process, the handling clutch takes the piece out of the mold. Core-trains and racketeers require special attention in respect to mold construction. 

Alternately, a third bubble may be inflated and passed through an oven to anneal the tubular film. This method may be preferred if excessive heat is required to anneal or crystallize the material. Shrink forces for some polymeric... 

The application of EVA to the manufacture of shrinkable tubes is based on the memory ability. Apart from the increase in gel fraction as the result of radiation crosslinking, variation in crystallinity is an important feature, which characterizes percentage stretch. For example, the ordered phase in ethylene -vinylacetate (13 % vinyl acetate) changes its value from 24 % to about 21 % [95 1]. The consequence of this drop is larger elasticity and stronger shrinking force. 

Two types of shrink testing were conducted on these films, and these methods are as follows (1) fixed length shrink force testing, and (2) free shrink testing. A TA Instruments ARES-LS rheometer and a TA Instruments Q800 Dynamic Mechanical Analyzer (DMA) were employed, respectively, to perform these two shrink tests. The rotational rheometer (ARES-LS) was used to conduct the fixed length shrink force test. In this test, the length of the film was fixed and the normal force was... 

The DMA was used to conduct the free shrink test. During this test, the length (strain) of the film was measured as a fimction of temperature. A small force of 0.01 N (minimal based upon instrument capability) was apphed to the sample to get rid of wrinkle. After these two tests, the shrink force-temperature profile from the fixed length test and sample recovered strain (length change/initial length)-temperature profile from the free shrink test were point-wise mapped relative to the common temperature for each coordinate pair and displayed on a fictive stress-strain curve. 

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