Chapter 8
Evaluation of Mechanical Properties of Recycled Commingled Post Materials 1
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Liqun Cao , R. M. Ramer , C. L. Beatty Downloaded by UNIV OF TEXAS AT AUSTIN on August 26, 2017 | http://pubs.acs.org Publication Date: November 13, 1992 | doi: 10.1021/bk-1992-0513.ch008
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Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 Florida Department of Transportation, 2006 Northeast Waldo Road, Gainesville, FL 32609 2
As plastics are being more widely used in industry, much more plastic wastes needs to be recycled for both economical and environmental reasons. A s a result, recycled plastics are becoming an economic source of engineering materials for construction and highway applications. However, the effective utilization of recycled plastics requires that the property changes that occur due to recycling be documented. Commingled post-consumer plastic scrap is currently melt– extruded into post and board shapes. The Florida Department of Transportation ( F D O T ) has been seeking the possible use of recycled plastics for highway applications such as guard rail posts, interstate highway boundary fence posts, sign posts, barricade sign substrates, etc.[1]. A l l of these applications require the study of mechanical properties since such materials must meet state specifications. The project has been divided into the studies of the mechanical properties, paint adhesion and environmental effects, etc. In this report, the commingled post mechanical properties such as flexure strength, tensile and compressive strength, and dynamic mechanical properties will be discussed.
EXPERIMENTAL MATERIALS Commingled posts studied were supplied by different companies. The posts are labeled according to a pre-established code by suppliers. The labels and dimensions are in Table 1. 0097-6156/92/0513-0088$07.25/0 © 1992 American Chemical Society Andrews and Subramanian; Emerging Technologies in Plastics Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1992.
8. C A O E T A L .
Mechanical Properties of Recycled Commingled Materials
Downloaded by UNIV OF TEXAS AT AUSTIN on August 26, 2017 | http://pubs.acs.org Publication Date: November 13, 1992 | doi: 10.1021/bk-1992-0513.ch008
FLEXURAL TEST The flexural tests on recycled commingled posts were conducted on the Foray Compression Test System. A l l the post samples indicate cross sections are distinctly different and contain two parts: the skin part which has relatively higher density and the core area which contains the voids. The pictures of sections from the molding end, center and the other end of post B2-2, which are labeled B22-a, B2-2-center, B2-2-b, respectively, are shown in Figure 1. The cross section pictures of post c-1 are shown in Figure 2. The fixture for the flexure test, a four point bending unit, is shown in Figure 3. The distance between the lower points used for supporting samples was 18", and the distance of the upper two points of the fixture used to compress samples was 6". The lengths of the flexure test samples are 30". Post label designations are as described. The first part of the sample code indicates code number of the post and the second part of sample code indicates the sample is from either molding end portion of the post "END" or the center of the post "CENTER". In order to study the stress-strain relation in detail, since the instrument can not print strain and displacement data, two video cameras were employed during the flexure tests of sample E-7-center, E-7-end, E-9center and E-9-end. The tests were done at F D O T . One camera was focused on the central point of the flexural sample on the testing machine with a line scale (for deflection) mounted beside the flexed sample. The other camera was focused on the load display screen. The video images recorded during the tests were timed and then analyzed by video image analyzing software, J A V A (Jandel Corp.). Two sets of data were recorded: center point position vs time (indicated by the stop watch) and compression load vs time (also indicated by stop watch). The two stop watches were simultaneously started. The video were subsequently analyzed to get the displacement and strain data that was needed. TENSILE TESTS The flexural tests of recycled commingled posts provided the actual information on the mechanical capability of the posts. The flexural load to failure (i.e. the flexural strength) is indeed a structural property rather than a material property since the flexure property is not only dependent on the mechanical properties of the post material but also on the type of cross section. In order to evaluate the material properties and predict the flexural properties of the recycled commingled posts, detailed studies focused on tensile mechanical properties from remolded samples, samples from skin areas and compression properties of the samples from the core area with voids.
Andrews and Subramanian; Emerging Technologies in Plastics Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1992.
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EMERGING TECHNOLOGIES IN PLASTICS RECYCLING
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Table 1 The Recycled Commingled Posts Labels
Length (in.)
B2-1 B2-2 C-l C-14 E-7 E-9 BC
— — 95 95 77.5 94.5 —
Cross section area (in.2) 26.25 26.25 28.27 28.27 41.25 28.27 12.96
Type of cross section
M
u
H
n
rectangular (3.5 x7.5 ) rectangular (3.5"x7.5") cylinder (d = 6") cylinder (d = 6") rectangular (7.5 x5.5 ) cvlinder (d = 6") square (3.6 x3.6") n
F i g u r e 1: C r o s s S e c t i o n s o f Post B2-2 molding end, c e n t e r , and the o t h e r end.
Andrews and Subramanian; Emerging Technologies in Plastics Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1992.
8. CAO ET AL.
Mechanical Properties of Recycled Commingled Materials
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