THE EFFECTS OF IMPACT MODIFIERS ON THE PROCESSABILITY AND THE TOUGHNESS OF POLY VINYL CHLORIDE PROFILES

THE EFFECTS OF IMPACT MODIFIERS ON THE PROCESSABILITY AND THE TOUGHNESS OF POLY VINYL CHLORIDE PROFILES. Extruded Poly Vinyl Chloride (PVC) door profile and window profiles often fail at the bend. This research aims to reduce such problem by enhancing the toughness of the PVC profiles while still maintaining their load bearing function and stiffness. Three impact modifiers namely methacrylate-butadiene-styrene (MBS), chlorinated polyethylene (CPE) and nano-scaled nitrile butadiene rubber (NBR) were employed in the PVC profiles at 1-11 phr. The processability assessed by rheometric study revealed only a slight increase in the torque required to process the melt PVC dosed with CPE and nano NBR while that required for the PVC with MBS was raised quite significantly. Although the PVC modified with MBS melted faster at a lower temperature, a rapid rise of temperature was observed during processing. The heat was probably due to the higher friction and shear induced by the rather viscous PVC melt dosed with MBS. Mechanical tests in terms of impact energy, stiffness and hardness revealed that the toughening efficiency of all three impact modifiers were close at low content, but at around 9 and 11 phr, the MBS and the CPE enhanced the impact energy quite rapidly by four folds while their corresponding hardness and stiffness were lowered considerably

On the Feasibility of Interoperable Schemes in Hand Biometrics

Personal recognition through hand-based biometrics has attracted the interest of many researchers in the last twenty years. A significant number of proposals based on different procedures and acquisition devices have been published in the literature. However, comparisons between devices and their interoperability have not been thoroughly studied. This paper tries to fill this gap by proposing procedures to improve the interoperability among different hand biometric schemes. The experiments were conducted on a database made up of 8,320 hand images acquired from six different hand biometric schemes, including a flat scanner, webcams at different wavelengths, high quality cameras, and contactless devices. Acquisitions on both sides of the hand were included. Our experiment includes four feature extraction methods which determine the best performance among the different scenarios for two of the most popular hand biometrics: hand shape and palm print. We propose smoothing techniques at the image and feature levels to reduce interdevice variability. Results suggest that comparative hand shape offers better performance in terms of interoperability than palm prints, but palm prints can be more effective when using similar sensors

Basic longitudinal texture and fracturing process in thermoset polymers

The “basic longitudinal texture”, which is present everywhere on the fracture surfaces of glassy thermosets and is the finest texture observed on such surfaces, consists of low ridges and shallow grooves that are aligned parallel with the direction of crack propagation. The periodicity of the basic longitudinal texture, i.e., the average lateral separation between the ridges (or grooves), has been found to be characteristic of materials. This and other properties were measured for a series of rigid epoxy specimens made from diglycidyl ether of bisphenol-A and methylhexahydrophthalic anhydride. For the series of epoxies studied, the glass transition temperatures varied from 76 to 143 °C, the room temperature Young's modulus varied from 2.29 to 2.97 G Pa, the room temperature yield stress in compression varied from 99 to 128 M Pa, the room temperature Knoop hardness numbers varied from 133.5 to 163.5, the rubbery modulus at 200'C varied from 12.8 to 21.6 MPa, and the periodicity of the basic longitudinal texture varied from 205 to 368 nm. Only properties of the liquid state, namely glass transition temperature and the rubbery modulus, correlated well with periodicity of the basic longitudinal texture. This suggests that the basic longitudinal texture is the remnant left on the fracture surfaces of a liquid state that must have developed during fracture. This suggests in turn that liquefaction is an intrinsic part of the brittle fracture of polymer network glasses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44718/1/10853_2005_Article_BF01197652.pd

The toughness of epoxy-poly(butylene terephthalate) blends

Blends containing 5% poly(butylene terephthalate) (PBT) in an anhydride-cured epoxy with three different PBT morphologies were studied. The three morphologies were a dispersion of spherulites, a structureless gel and a gel with spherulites. The average fracture toughnesses, K Ic , and fracture energies, G Ic , for those morphologies were 0.83, 2.3 and 1.8 MPa m 1/2 and 240, 2000 and 1150 J m −2 , respectively. These values should be compared with the values of 0.72 MPa m 1/2 and 180 J m −2 , respectively, for the cured epoxy without PBT. The elastic moduli and yield strengths in compression for all three blend morphologies remained essentially unchanged from those of the cured epoxy without PBT, namely, 2.9 GPa for the modulus and 115 MPa for the yield strength. The fracture surfaces of the cured spherulitic dispersion blends indicate the absorption of fracture energy by crack bifurcation induced by the spherulites. The fracture surfaces of the cured structureless gel blends indicate that fracture energy was absorbed by matrix and PBT plastic deformation and by spontaneous crack bifurcation. But phase transformation of the PBT and anelastic strain of the matrix below the fracture surfaces may account for most of the large fracture energy of the cured structureless gel blends.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44733/1/10853_2004_Article_BF00366876.pd

The basic longitudinal texture in the brittle fracture of glassy polymers.

An investigation of the factors affecting the periodicity of the basic longitudinal texture in rigid glassy polymers was conducted on a series of epoxy resins made from diglycidyl ether of bisphenol-A cured with an anhydride. The basic longitudinal texture occurs on fracture surfaces and consists of relatively short, low ridges and shallow grooves extending exactly in the direction of crack propagation. This texture was observed over the entire fracture surface irrespective of the fracturing conditions such as temperature or crack speed. The basic longitudinal texture has been hypothesized to arise from an unstable growth of the crack as a quasi-air-liquid interface or meniscus, which tends to develop into a pattern of parallel fingers reaching ahead of the crack. The separation between the ridges and grooves, or the periodicity, was found to correlate with the one-second flexural modulus in the rubbery state. But it is uncorrelated with the Young's modulus, the power-law coefficient and exponent in the pre-yielding region and only weakly correlated with the yield stress and yield strain in the yielding region of the stress-strain behavior in the solid state. As the one-second flexural modulus in the rubbery region increases from 12.8 MPa to 21.6 MPa, the periodicity decreases nearly linearly from about 370 nm to 200 nm. This strong correlation supports the existence of a quasi-air-liquid zone as hypothesized in the crack fingering hypothesis. The liquefaction is believed to be stress-induced and occurs ahead of the crack fingers in glassy polymers. The thickness of the liquefied zone is expected to equal roughly the periodicity. A model for the periodicity is proposed.Ph.D.Materials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103395/1/9034410.pdfDescription of 9034410.pdf : Restricted to UM users only

Time Stamp Detection and Recognition in Video Frames

Time stamp superimposed on the video frames can be used as indices for video indexing and retrieval systems. Some applications use it for speed detection of objects. In this paper, we propose a time stamp detection approach based on edge detection method. Furthermore, we apply temporal properties of video frames so that time stamp can be located quickly. We also propose our digit recognition module to test the performance. Experimental results show that our approach can detect time stamp location accurately. The proposed approach can discriminate between date and time, and it can extract time with sub-second of precision. The recognition rate is also high enough to be used practically. 1