Polymethylmethacrylate polymer blends

Many research groups have been working on radiation processing of polymer blends, to stabilize the phases and improve performance. The polymers that have been used in the radiolytic studies of blends include polyethylene (PE), polypropylene (PP), ethylene propylene rubber (EPR), polyvinyl chloride (PVC), polystyrene (PS), and polymethylmethacrylate (PMMA). 

Figure 14.5. DSC thermograms for aged polymer blends (a) polyvinylchloride/poly isopropyl methacrylate, immiscible blend, aged at a temperature of 60°C, and (b) polyvinyl chloride/polymethylmethacrylate, miscible blend, aged at 80°C. Time of aging, t in hours, is shown alongside each curve. Broken lines represent the un-aged samples for comparison.

Different polymer blends like PE (polyethylene)/PS (polystyrene) [10-11] and PMMA (polymethylmethacrylate)/PS [12-13] have been produced using supercritical C02-assisted extrusion. Fully intermeshing twin-screw extruders have been used in these studies. A decreased shear thinning behavior on dissolution of supercritical CO2 into blends was observed. The obtained reduction in viscosity ratio resulted in a finer dispersion of the minor phase, which is desirable to create a good polymer blend. The effect of supercritical CO2 on the dispersion of the minor phase for a PMMA/PS blend can be seen clearly in Fig. 12.5. 

As of 1995, more than 30 different polymer blends were being used in the manufacture of membranes for hemodialysis and hemofiltration (Klinkmann and Vienken, 1995). The various membrane types used for renal replacement therapy can be divided into membranes derived from cellulose (83 percent of 1991 worldwide total) and from synthetic materials (the remaining 17 percent) (Klinkmann and Vienken, 1995). Synthetic membranes have been constructed from such materials as polyacrylonitrile (PAN), polysulfone, polyamide, polymethylmethacrylate, polycarbonate, and ethyl-vinylalchohol copolymer (Klinkmann and Vienken, 1995). In the United States, use of cellulosic materials for membrane construction predominates at around 95 percent of the total number of membranes used (Klinkmann and Vienken, 1995). 

There are, however, a number of instances in which interfacial diffusion has been demonstrated experimentally between differing polymers they include the following polyvinylchloride and polycaprolactone polyvinylchloride and polymethacrylate polyvinylchloride and styrene-acrylonitrile copolymer polyvinyUdene fluoride and polymethylmethacrylate. Nevertheless, the thermodynamic incompatibility of so many polymers is a fundamental problem in the making of polymer blends. ... 

Polycarbonate, PC. PC was introduced in 1958. To improve its processability, impact behavior, and solvent resistance, PC must be modified. The first blends with polyolefins, PO, or with ABS were developed in 1960. These were rapidly followed by alloys with polysiloxanes in 1961, PAES in 1965, PET in 1966, POM in 1968, PSF -n ABS in 1969, PES -n ABS in 1970, PBT in 1971, PA or PPE + SBR in 1973, PPS in 1974, PS in 1976, styrene-maleimide (SMI) in 1977, polyaramid (PARA) in 1979, etc. Owing to the chemical nature of the statistical segment, PC can be readily compatibilized or modified, becoming a frequent component of polymer blends. Its affinity to acrylates has been widely explored. However, only in 1986 was its miscibility with polymethylmethacrylate, PMMA, disclosed [Kambour, 1986]. These blends were found to be suitable for glazing materials and optical disks. Another miscible blend of PC (with aliphatic polyester of neopentyl glycol) was discovered in 1991 [Lundy et al., 1991]. Commercial PC/PA blends are relatively recent. In 1992 Toray Industries introduced Toray-PC and Rohm Haas Paraloid. Both blends contain about 30 % of PARA and PA, respectively. 

As will be noted no molecular anisotropies and no effects due to size and size distribution of the particles of the discrete phase are recognized. Through E = 2(1 + p)G Eq. (2.5) can be used to predict also the complex tensile modulus. A good example for the applicability of Eq. (2.5) is furnished by the experimental data obtained by Dickie et al. [75]. For the dynamic tensile modulus of a physical mixture (polymer blend) of 75% by weight polymethylmethacrylate (PMMA, continuous phase) and 25% butylacrylate (PBA, discrete phase) within experimental error correspondence of calculated and measured data was obtained (Fig. 2.13,... 

In particular, blends of PVDF with a series of different polymers (polymethylmethacrylate [100-102], polyethylmethacrylate [101], polyvinyl acetate [101]), for suitable compositions, if quenched from the melt and then annealed above the glass transition temperature, yield the piezoelectric [3 form, rather than the normally obtained a form. The change in the location of the glass transition temperature due to the blending, which would produce changes in the nucleation rates, has been suggested as responsible for this behavior. A second factor which was identified as controlling this behavior is the increase of local /rans-planar conformations in the mixed amorphous phase, due to specific interactions between the polymers [102]. 

There are several ways of isolating molecules, in addition to dilution in appropriate solvents. For instance, extremely long PDA chains can be diluted in their monomer single crystal by exploiting the peculiar polymerization mechanism [91] of this class of polymers. In the case of CPs blended with non-conjugated macromolecules (polyethylene, polymethylmethacrylate, etc.) or inclusion crystalline compounds [92], the interaction between molecule and environment is usually strongly suppressed, but at the expense of the sample optical density, in a way that may easily challenge the common sensitivity of time-resolved techniques. 

Since the volume fraction (f) of the conducting network near threshold is small (the percolation threshold is at 1% PANI, or less), the conductivity increases smoothly and continuously over many orders of magnitude as the concentration of conducting polymer in the blend increases above threshold [61,279-281], The low percolation threshold and the continuous increase in o-(f) above threshold are particularly important. As a result of this combination, conducting polyblends can be reproducibly fabricated with controlled levels of electrical conductivity while retaining the desired mechanical properties of the matrix polymer (such as polyolefins, polymethylmethacrylate, polyesters, ABS, polyvinylbuteral, etc,) [282,283],... 

Blends of isotactic and atactic polymethylmethacrylate (PMMA) in solution have been used to form semipermeable membranes, for both hemodialysis and hemofiltration. Details of the polymer properties are not available (18). 

We have applied the ultrafast confocal microscope to map excited state dynamics in thin films of poly(9,9-dioctylfluorene) (PFO, see chemical structure in figure 2(a)), blended with polymethylmethacrylate (PMMA, 10% wt. PFO in PMMA). PFO is a blue-emitting polymer, with an absorption maximum at 385 nm (see Fig. 2(a)), while PMMA is transparent at our pump wavelength and it does not interact with PFO [6] so that it is optically inert. Figure 2(b) shows the macroscopic AT/T spectrum of PFO measured at x = 1 ps at 570 nm probe wavelength we observe a photo-induced absorption (PA) due to photo-generated polarons [7],... 

This chlorine atom attack accounts for the decrease in the molecular weight of polymethylmethacrylate, monomer production at abnormally low temperature and the delay in the dehydrochlorination of polyvinylchloride. This delay in dehydrochlorination is general for blends of polyvinylchloride and any polymer containing hydrogen atoms that can be abstracted by chlorine atoms. 

In this section, examples of films made from polyvinylidene fluoride (PVDF) are discussed. Although most of the pol5winylidene fluoride film is in the form of coating on metal substrates, stand-alone PVDF films and sheets are produced by extrusion and film blowing.1 ] ] Blends of PVDF and a number of other polymers such as polymethylmethacrylate (PMMA) are miscible. Films made from these blends have excellent piezoelectric properties. 

Nonolefinic thermoplastic polymers that in principle may be blended with polyolefins include polyamides (nylons) such as polyamide 6, polyamide 66, polyphenylene sulfide (PPS), polyphenylene ether (PPF), and polyphenylene oxide (PPO) polyesters such as polyethylene terephthalate (PET), polybutylene terephtha-late (PBT), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polycarbonates, polyethers, and polyurethanes vinyl polymers such as polystyrene (PS), polyvinyl chloride (PVC), polymethylmethacrylate (PMMA), and ethylene... 

Valenza, A., Lyngaae-Jorgensen, J., Utracki, L.A., and Sammut, P. (1991) Rheological characterization of polystyrene/polymethylmethacrylate blends. Part 2. Shear flow. Polym. Networks Blends, 1 (2), 79-92. 

Another technique, known as the dry powder mixing method, has been employed by Cooper et al. to produce nanotube-reinforced polymethylmethacrylate (PMMA) composites [61]. Like most of the currently used fabrication methods for nanotube-based polymer composites, this technique is a combination of several protocols including solution-evaporation, sonication, kneading, and extrusion. More specifically, these workers used ultrasonic techniques to blend carbon nanotubes with PMMA particles, and the blend was later extruded to orient the nanotubes. Yang et al. [62] prepared small-scale batches of ABS nanocomposites without the use of solvents or ultrasonic techniques with good dispersion of the nanotubes. 

Characterization of Polystyrene/Polymethylmethacrylate Blends," Polym. Networks Blends, 1, 79 - 92. 

Time of flight static secondary ion mass spectroscopy (SSIMS) has been applied to perfluorinated polymers, polystyrene, polyacylacrylates (including poly cyclo-hexylmethacrylate, polybenzyl methacrylate, polyphenyl methacrylate, poly n-hexyl methacrylate, poly n-butyl methacrylate, polymethylmethacrylate, poly n-propyl methacrylate, polyisopropyl methacrylate and poly secbutyl methacrylate). Blends of polystyrene and polyvinyl chloride, bisphenol A and polystyrene, polycarbonate and polystyrene and tetramethyl bisphenol A and polycarbonate have also been studied by this technique. 

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