Polymethylmethacrylate experiments

Other polymers, such as polycarbonate and polymethylmethacrylate, are hard, tough, and transparent. These materials are ideal for applications that are likely to experience severe impact. We find these polymers in bus shelters, motorcycle helmet visors, and jet fighter canopies. 

The first reports on the drag reduction phenomenon are found in publications by Blatch (1906), Forrest (1931), as well as by Brautlecht (1933), who measured the flow behaviour of paper pulps. In independent studies made by Mysels (1949) and Toms (1948) this phenomenon was observed in the turbulent flow of gasoline in pipes when aluminum soaps were added and, in Toms experiments, when polymethylmethacrylate in monochlorobenzene was used. The reduction of friction is therefore often termed the Toms effect . This flow behaviour is also known in the literature as the Non-Newtonian- , visco-elastic- , Texas- or Texas-Toms-effect , due to the contributions made by Texan researchers. It is also more generally known, and this term will be used in this paper exclusively, as the drag-reduction effect of flow additives. 

This was corroborated by experimental results obtained in single particle experiments carried out for polypropylenes. It was possible to show that the relative attrition behavior under pure sliding friction stresses was identical to that observed in a pipe bend whereas deviations to that under pure normal impact conditions were found. For polymethylmethacrylate and polystyrene on the other hand, the relative attrition behavior in the pipe bend corresponds to that of the normal impact experiments. 

An SFM based lithography technique by means of mechanical interactions as applied to surfaces of polystyrene (PS) and polymethylmethacrylate (PMMA) is described in Sect. 6. Similarly, some results of SFM-based poling experiments performed on a piezoelectric polymer are elucidated in Sect. 7.6. 

Surface fluorination of several polymers other than polyethylene has been attempted to show the effectiveness of this technique in generating perfluorinated surfaces. Results of formamide contact angle experiments are summarized in Table (3). It appears from these results that under the conditions studied, polypropylene and nylon 6,6 can be perfluorinated but polymethylmethacrylate does not perfluorinate in the time scale shown. The C, XPS spectra and the respective chemical compositions are shown in Figure (7) and Table (3). Even though PMMA shows high... 

We have conducted experiments on different polymers [21, 22] (polystyrene, polyisoprene, polymethylmethacrylate) and used data in the literatiure on polystsTene [20] and polyWtadiene [23] in order to check the scaling laws predicted by relation (5-3). 

Experimental data for polymer solutions have been reported by Osaki, Tamura, Kurata, and Kotaka (60), by Booij (12), and by Macdonald (50). Osaki et al. used polystyrene in toluene, polymethylmethacrylate in diethylphthalate, and poly-n-butylmethacrylate in diethylphthalate. Booij s data were for aluminum dilaurate in decalin and a rubbery ethylene-propylene copolymer in decalin. Macdonald s experiments were performed on several polystyrenes in several Aroclors and on polyisobutylene in Primol. Shortly after the original publication of the Japanese group, Macdonald and Bird (51) showed that a nonlinear viscoelastic constitutive equation was capable of describing quantitatively their data on both the non-Newtonian viscosity and the superposed-flow material functions. Other measurements and continuum model calculations have been described by Booij (12 a). 

The velocity of sound propagation in a material is simply related to the stiffness constants and density. It is a very convenient method in practice and gives simple and unambiguous results in the case of oriented glassy polymers, as in the work of Treloar on polymethylmethacrylate. From a single experiment, two of the five elastic constants may be determined. The principle of the method is shown in Fig. 1. 

In a series of related publications, Hennig has reported the measurements of elastic constants for oriented polymers which are either amorphous or of low crystallinity. In his earliest work." Hennig showed that in polyvinyl chloride and polymethylmethacrylate the relationship 3/Eo = S33 + 2S11, where is the modulus of the isotropic polymer, holds to a good approximation. Results for the anisotropy of the linear compressibility y in polyvinyl chloride, polymethylmethacrylate, polystyrene and polycarbonate were also reported. In this experiment Hennig measured the linear compressibility parallel to the draw direction 7ii, and that in the plane perpendicular to the draw direction Vi. For uniaxially oriented polymers yn = 2Si3 + S33 = S i -I-Si2-I-S 3. It was... 

From Fig. 16 it can be seen that stiffnesses were only slightly dependent on orientation, the largest change being an increase of 30 o in Young s modulus in the axial direction for polymethylmethacrylate. Static loading experiments on strips cut at various angles to the stretch direction enabled some check values to be obtained. The trend was similar to that in the ultrasonic measurements, but absolute values of stiffness were lower, presumably due to a frequency dependent effect. The authors comment that despite the small effect of orientation on low strain... 

Among guest-host systems, the most studied system is Disperse Red-doped polymethylmethacrylate (PMMA) (Fig. 49.3) [13]. The early poling experiments on this system were accomplished by using parallel-plate electrodes and different doping levels. The maximum x value obtained with parallel-plate poling was 5 pm/V. Subsequent experiments employed corona poling, and it was possible to achieve a x l value of 13.4 pm/V in thus poled samples [14]. Table 49.2 shows d i = 0.5x ) values of various NLO chromophores in a PMMA polymer host [13-17]. 

In the first room-temperature, spectrally-resolved, single-molecule experiments, Trautman, Macklin and coworkers observed spectral shifting [17]. The sample consisted of dil (an indocarbocyanine dye) dispersed on polymethylmethacrylate... 

The present experiments were performed on polymethylmethacrylate (PMMA) and novolak resin (Su-8). Experimental set-up is schematically given on Fig. 16. Polymer films were... 

The time-dependence is important for technical applications. Figure 8.8 shows isochronous stress-strain curves of polymethylmethacrylate (pmma) with a glass temperature of about 100°C. These curves are obtained in retardation experiments, where the strain in a specimen kept at constant stress after a fixed loading time is measured. Different from ordinary stress-strain curves, each value of the stress requires its own experiment. The deformation becomes larger the longer the loading time is. 

The H-shaped tnicrochannel used in the experiments is shown in Fig. 4. The fabrication is based on the adhesive lamination techniques. In this method, two polymethylmethacrylate (PMMA) plates (75 mm x 25 mm) were bonded by a layer or layers of double-sided adhesive tapes to form a closed microfluidic channel with inlet and outlet holes. The channel structure was cut through the adhesive tape (Arclad 8102 transfer adhesive. Adhesives Research Inc.). Thus the adhesive tapes define the depth of the channel. The two liquids flow side by side in the straight tnicrochannel in the direction from left to right from the syringe pump. The two liquids are introduced from inlet 1 and inlet 2 outlet 1 and outlet 2 are for collection of the products or wastes. Across the microchan-nel, platinum electrodes (Aldrich-Sigma, Singapore) were inserted for the application of the electric field. 

The development of this technique was based on early experiences with the use of injection techniques. As a result of a perceived putative efficacy, attention was directed to the identification of inert, biocompatible substances that might safely function as bulking agents at the LES. An early report in 2001 by Feretis described a technique of endoscopic submucosal injection of polymethylmethacrylate microspheres suspended in gelatin into the LES of ten patients. At 7 months follow-up, there was a significant fall in 24-hour acid exposure (24.5% to 7.2%) that was, in addition, supported by a comparable improvement in symptom scores. 

Fig.3. A typical plot of a /R vs. P/a for a hemisphere made of polymer C on a film of polymethylmethacrylate. Closed circles ( ) represent the data obtained fi m the loading experiments, whereas the open circles (O) represent the data obtained from the unloading experiments.

In these experiments, we investigated polystyrene (PS) doped with phthalocyanine and polymethylmethacrylate (PMMA) doped with tetra-4-/err-butyl phthalocyanine. Both sample materials have also been investigated by heat release and specific heat measurements [29]. The samples had optical densities of about 0.4 at a typical thickness of 3 mm. The samples were prepared by bulk polymerisation of the solution of the dye in the monomer. 

The a-transition, which involves motion in long segments of the main polymer chain, is related to the Tg. The P-transition involves rotation of short-chain ester side groups and, therefore occurs below the Tg. The frequency dependence of the p-Tg can be used to calculate the activation energy for the molecular motion, which provides important information for characterising the structure and predicting the performance of polymeric materials. In a DETA experiment, the calculated activation energy for the P-transitions in polymethylmethacrylate (PMMA) was 17.7 kcal/mol. This correlates well with the values calculated from DMTA and creep experiments. 

The materials of construction of the vessel or pipe and all internals (impeller or mixers, shaft, baffles, bearings, seals, and lid) must be compatible with the fluids and any solids that are to be mixed. For most mixing experiments the ability to see clearly what is happening inside the mixer is exfiemely useful, if not essential. Vessels or pipes made of a transparent material such as polymethylmethacrylate (PMMA Perspex or Lucite) or glass are ideal, provided that measurements are to be made at temperatures and pressures within the modest limits allowed by such materials (the glue used to seal PMMA vessels tends to fail at about 50°C). PMMA vessels up to about 1 m in diameter can be manufactured relatively simply. 

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