exam Flashcards

Question

Polyethylene Terephtalate (PET)

Answer 1

* Each disperesed monomer droplet is a bulk reactor * good heat transfer * Resulting particle size ~50-500 microns * Monomer soluble initiater, low surfactant level * High MW typically produced

Answer 2

* Each micelle is a mini-bulk reactor * Water soluble initiator/high levels of surfactant (1-5%) * High surface are = excellent heat transfer * Resulting particle size \<1 microns * Low concentratioin of initiator = high MW * Less termination than conventional bulk free radical polymerization

Answer 3

* What dictates structure * Intermolecular * Intramolecular interactions * Find each other in solid state becase a segmetns want to be with A segments and be want to be in be segments * Commercial applications * Shoes * Tires * Adhesives

Answer 4

* Made in concentrates sulfuric acid * Actually a liquid crystalline polymer

Answer 5

All PSAs have G' below 3\*10⁶

Answer 6

A manufactured fiber in which the fiber forming substance is any long-chain synthetic polymer composed of at least 85% by weight of acrylonitrile units (-CH₂-CH[CN]-)_x

Answer 7

A manufactured fiber in which the fiber forming substance is a long-chain synthetic polyamide in which less than 85% of the amide-linkages are attached directly (-CONH-) to two aliphatic groups

Answer 8

Document that describes a claimed invention that provides the legal owner with the right to exclusively make, use, or sell the claimed invention for a certain period of time.

Answer 9

An invention that is intentionally kept secret and not disclosed to the public, buy may be practiced.

Answer 10

* The abrupt and irreversible transformation from a viscous liquid to an elastic gel or rubber * The instant at which the weight average molecular weight diverges to infinity

Answer 11

* Fiber reinforced polymers (FRPs) * Metal matrix composites (MMC)

Answer 12

* Outstanding corrosion resistance * Excellent fatigue and fracture resistance * Lower toling cost alternatives * Lower thermal expansion properties * Simplification of manufacturing by parts integration

Answer 13

* Open molding * Vacuum bag molding * Pressure bag molding * Autoclave molding * Resing transfer molding (RTM)

Answer 14

* Increased rate of reactions * Higher yields * Uniform heating * Environmentally friendly * Greater reproducibility of chemical reactions

Answer 15

* Lack of scalability * Limited applicability * Safety hazards * Health hazards

Answer 16

* their inorganic backbone of silicon and oxygen atoms and have resulted in their widespread use as high performance elastomers and fluids, surface modifiers, adhesives, and biomedical materials. * The siloxane backbone, which contains long Si-0 bonds (1.64 A compared to 1.54 A for a C-C bond), the absence of substituents on every other skeletal atom (oxygen), and a wide bond angle at oxygen (Si-0-Si 143" compared to C-C-C 109"), possesses unique dynamic flexibility. * This leads to materials that retain elasticity and do not become brittle even at very low temperatures. For example, poly(dimethylsiloxane), the most common polymer, has a glass transition temperature (Tg) of - 123 "C, and for poly(methylhydrosi1oxane) the Tg value is even lower (- 137 "C). * In addition, Si -0 bonds are stronger than C-C bonds (bond energies: Si-0 ca. 450 kJmol-', C-C ca. 348 kJmol-I) and are more stable to oxidation and UV radiation. This results in higher thermooxidative stability

Answer 17

* Polysiloxanes also have a variety of other useful properties such as hydrophobicity and their exceptionally high permeability to gases. * Indeed, snails can live submerged beneath the surface of low molecular weight poly(dimethylsiloxane) fluids for up to 72 h by breathing oxygen that diffuses through the material. * Other applications in the biomedical field that take advantage of the high permeability of polysiloxanes include uses as soft contact lenses and artificial skin. * However, the leakage of silicone-based materials through polysiloxane membranes in breast implants has raised considerable public concern. * Nevertheless, claims of health problems arising from the consequential presence of silicones in the body appear unproven to date

Answer 18

* One of the most remarkable features of the all-silicon backbone is that it leads to the delocalization of σ electrons, a phenomenon that is virtually unknown in carbon * This can be understood in terms of the nature of the molecular orbitals associated with the Si-Si σ bonds. * These are more diffuse than those associated with C-C σ bonds, since they are constructed from higher energy 3s and 3p atomic orbitals. * This leads to significant interactions between the adjacent Si -Si σ bonds along a polysilane chain, a situation analogous to that for the x bonds in π-delocalized polymers such as polyacetylene. * Thus a band model rather than a localized model is more appropriate

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