Acrylic mold shrinkage

Titanium hydroxide, 129 Wollastonite, 129 Wood flour, 129 Mold and spores, 412,413 Mold growth, 27, 412-416 Mold propagation, 26,412 16 Mold shrinkage, 105, 131 Nucleation, effect of, 131 Plastic crystalllinity, effect of, 131 Moldable thermoset acrylic polymer, 80 Molecular weight distribution (MWD), 63, 636, 649-651... 

POM/TPU, with SAN, ABS, AES, PC, PA, PAr, PPE, HIPS, acrylics, imidized acrylics, or SMA For lower mold shrinkage, good stiffiiess, elongation, toughness, etc. Flexman 1992... 

A main disadvantage of acrylate polymerization is shrinkage. However, this shrinkage process is well defined since it is directly related to the number of double bonds converted. In the lens applications the quartz molds are adjusted for this shrinkage. 

The tendency of thick sections of DMC structural parts to crack has been overcome by using low-profile polyester resins (or low-shrink resins). These are prepared by making a blend of a thermoplastic (e.g., acrylic) polymer-styrene system with a polyester-styrene system. Moldings of this blend cured at elevated temperatures exhibit negligible shrinkage and minimal warpage and have very smooth surface, to which paint may be applied with very little pretreatment. 

Reactive adhesives such as epoxy and acrylic resins may induce shrinkage stresses that reduce often the bonding strengths. Therefore, the volume shrinkage should be measured by standards such as JIS K6911, in which adhesives are cured in a mold and the dimension of the adhesive is measured to calculate the shrinkage ratio. 

Initial development of UV-curable materials for imprint lithography predates NIL and was inspired in the 1980s by the need to make reliable replicas in a short amount of time, and at a low cost, for LaserVision videodiscs. " Researchers at the Philips Research Laboratories in the Netherlands coined the production process of videodisc replication as photopolymerization process or 2P process." The 2P process requires the use of photosensitive materials that become extremely hard, with low shrinkage, once exposed to UV radiation (typically 300-400nm). The 2P process is based on free radical chemistry, and UV-curable materials consist of liquid monomers, usually acrylates or acrylate oligomers, to which a suitable photoinitiator is added. A little over a decade later, Haisma et extended this work to mold-assisted nanolithography and is the first reported work of UV-NIL with 100 nm features. 

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