why do polymers have low melting points

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ABSTRACT: Empirically validating new 3D-printing related algorithms and implementations requires testing data representative of inputs encountered emph{in the wild}. An ideal benchmarking dataset should not only draw from the same distribution of shapes people print in terms of class (e. g. , toys, mechanisms, jewelry), representation type (e. g. , triangle soup meshes) and complexity (e. g. , number of facets), but should also capture problems and artifacts endemic to 3D printing models (e. g. , self-intersections, non-manifoldness). We observe that the contextual and geometric characteristics of 3D printing models differ significantly from those used for computer graphics applications, not to mention standard models (e. g. , Stanford bunny, Armadillo, Fertility).

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We present a new dataset of 10,000 models collected from an online 3D printing model-sharing database. Via analysis of both geometric (e. g. , triangle aspect ratios, manifoldness) and contextual (e. g. , licenses, tags, classes) characteristics, we demonstrate that this dataset represents a more concise summary of real-world models used for 3D printing compared to existing datasets. To facilitate future research endeavors, we also present an online query interface to select subsets of the dataset according to project-specific characteristics.

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The complete dataset and per-model statistical data are freely available to the public.
Ethene can be polymerised in slightly different ways to make low-density polyethene (LDPE) and high-density polyethene (HDPE). These polymer A polymer is a large molecule formed from many identical smaller molecules (monomers). have different properties because of the structure of their molecules. Some polymer chains have side branches. Low-density polyethene (LDPE) is like this. The side branches stop the polymer molecules from lining up regularly.

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Its structure is not crystalline. the material is less strong, and has a lower melting point, than HDPE High-density polyethene (HDPE) does not have side branches. The polymer molecules line up regularly to give a crystalline structure. the material is stronger, and has a higher melting point, than LDPE By carefully controlling the amount of branching, it is possible to make polymers with various amounts of crystallinity. This means it is possible to make a polymer with the exact properties that are required for a particular purpose. Now try a – higher.

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