Glassy polymers polypropylene

Annealing can reduce the creep of crystalline polymers in the same manner as for glassy polymers (89,94,102). For example, the properties of a quenched specimen of low-density polyethylene will still be changing a month after it is made. The creep decreases with time, while the density and modulus increase with time of aging at room temperature. However, for crystalline polymers such as polyethylene and polypropylene, both the annealing temperature and the test temperatures are generally between... 

A method for the detailed atomistic modelling of amorphous glassy polymers has been developed [50] and applied to atactic polypropylene. 

A method for the detailed atomistic modelling of amorphous glassy polymers has been developed [50] and applied to atactic polypropylene. This method has been described in Sect. 5.4. The quasi-static modelling of chain dynamics [51] has been described in Sect. 5.4.2. 

Glassy polymers with highercohesiveness, like polycarbonate and cross-linked epoxies, preferentially exhibit shear yielding [7], and some materials, such as rubber-modified polypropylene, can either craze or shear yield, depending on the deformation conditions [8]. Application of a stress imparts energy to a body which... 

Particularly evident is the lack of systematic reports on polymer-mixed solvents data (VLE or LLE) in the open hterature, especially in form of full-phase equilibrium measurements. Most experimental studies for mixed solvent systans have been reported by Chinese and Japanese investigators - and only a few by other investigators. Data are often reported simply as soluble/nonsoluble or as theta temperatures (critical solution temperature at infinite polymer molecular weight). Several reported polymer-mixed solvent data concern supercritical fluid applications (e.g., polypropylene/pen-tane/C02, and PEG/C02/cosolvent ) and bioseparations, especially for systems related to the partitioning of biomolecules in aqueons two-phase systems, which contain PEG and dextran. A recent review for data on solnbihty of gases in glassy polymers is also available. ... 

Some of the prominent glassy polymers that we consider in the second family that can exhibit rubbery behavior above their Tg are polystyrene (PS), polypropylene (PP), polyvinylchloride (PVC), and polymethyl methacrylate (PMMA). These are shown in Fig. 2.1 in Chapter 2. 

After a brief overview of the phenomenology of plastic flow of glassy polymers, we start with an account of recent computational simulations of the strain-producing segmental relaxations in unit plastic events consisting of thermally assisted shear transformations in polypropylene and polycarbonate. With the... 

Figure 5.3 Computer simulations performed by Greenfield and Theodorou [141 for free volume clusters before and after 10 Monte Carlo steps within (a) glassy polymer and (b) rubbery polymer. Reprinted with permission from Macromolecules, Geometric analysis of diffusion pathways in glassy and melt atactic polypropylene by M. L Greenfield and D. N. Theodorou, 26, 5461-5472. Copyright (1993) American Chemical Society...

Shear bands have been observed in polypropylene under compression at low temperature, which is the first observation of this mechanism of deformation in such a highly crystalline polymer. There are previous reports of craze formation in poi)q)ropylene, but not shear bands which are normally associated with glassy polymers. Two discrete sets of shears band at 35° to 42° to the compression axis have beat seen. It appears to be associated with sliding between lamellae and along spherulite boundaries. 

Qiu J, Wang Z, Yang L, Zhao J, Niu Y, Hsiao BS (2007) Deformation-induced highly oriented and stable mesomorphic phase in quenched isotactic polypropylene. Polymer 48 6934-6947 Rebollar E, Perez S, Hernandez JJ, Martin-Pabiani I, Rueda DR, Ezquerra TA, Castillejo M (2011) Assessment and formation mechanism of laser-induced periodic surface structures on polymer spin-coated films in real and reciprocal space. Langmuir 27 5596-5606 Reiter G, de Gennes PG (2001) Spin-cast, thin, glassy polymer films highly metastable forms of matter. Eur Phys J E 6 25... 

A wide variety of well-known polymers are currently rubber modified, always with the intent of improving the toughness of the material either at ambient temperature, or, often, at sub-ambient. Most well known is high impact polystyrene (HIPS) which, in terms of composition, is polystyrene containing 5-10% polybutadiene rubber. ABS (acrylonitrile/butadiene/styrene) is similar to HIPS except the glassy polymer is the more heat and solvent resistant poly(styrene-co-acrylonitrile). Poly(vinyl chloride) (PVC), polypropylene (PP), epoxy resins, and nylons are all available in rubber-... 

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