Effect of the Inorganic Filler Contents on Polymer

Effect of the Inorganic Filler Contents on Polymer ANALYSIS OF ZIF 8/PAI AND CMS/PAI MEMBRANES FOR CO2/CH4 GAS SEPARATION Yohannan Subin Sabilon Department of Chemical Engineering, National Institute of Technology Tiruchirappalli, India Zeolitic Imidazolate Frameworks 8 (ZIF 8) nanocrystals and Carbon Molecular Sieves (CMS) particles were prepared by using standard procedures. UV visible spectroscopy and XRD tests were done for the confirmation of the particles prepared and scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis were done to study the morphology of the particles prepared. ZIF 8/PAI and CMS/PAI MMMs were successfully synthesized by using ZIF 8 and CMS inorganic fillers and Polyamideimide (PAI) polymer using phase inversion technique. Various weight contents (1%, 2% and 3%) of the inorganic fillers were incorporated in the polymer matrix. Reinforcing of the polymer matrix with inorganic fillers was done in the form of nano and micro particles respectively. The effect of the inorganic filler contents on the mechanical properties of the polymer was investigated. Hydrophilic nature and porosity determination test, Fourier transform infrared spectroscopy (F TIR) and SEM were done to study the hydrophilicity and morphology of the composite system. Keywords: Carbon dioxide, Methane, Mixed Matrix Membranes, Carbon Molecular Sieves,Zeolitic Imidazolate Frameworks INTRODUCTION Carbon dioxide (CO2) is one of the components of landfill gas, natural gas and biogas. It is also the main combustion product of fossil fuels and a leading contributor to global warming as its a greenhouse gas. In order to obtain fuel with enhanced energy content, to prevent corrosion problems in the gas transportation system and to reduce the climatic impact of CO2 gas it is quite essential to remove CO2 from those gas streams. This has driven the development of different technologies for CO2 gas separation. Among the different types of technologies being used membrane technology has experienced substantial growth, breakthroughs and advances during past decades [10]. Membrane technology offers high energy efficiency, simplicity in design and construction of membrane modules and environment compatibility. Although there are different types of membranes being used the combination of the superior performance of inorganic materials with the handling properties of the polymers is offered by Mixed Matrix Membranes (MMMs). Therefore in our study we will be using MMMs for CO2/CH4 gas separation. In the MMMs the inorganic fillers are added to the polymer matrix. Over the years different inorganic fillers have been used for preparing MMMs for CO2/CH4 gas separation out of which Zeolitic Imidazolate Framework 8 (ZIF 8) is known to show maximum selectivity while Carbon Molecular Sieves (CMS) is known to show maximum permeability [19]. In this study the preparation and characterization of these inorganic fillers is shown. These inorganic fillers were successfully incorporated in the Polyamideimide (PAI) polymer matrix and MMMs were prepared. The characterization and analysis of the ZIF 8/PAI and CMS/PAI MMMs have been done with different loading of inorganic fillers in order to choose the best possible membrane combination for CO2/CH4 gas separation. EXPERIMENTAL SECTION Materials Zinc hydrate crystals and N-methyl 2-pyrrolidone (NMP) required in the preparation of ZIF 8 nanocrystals were purchased from Merck Life Science Private Limited, Mumbai, India. Methanol used for washing during centrifugation was also bought from Titan Biotech Limited, Rajasthan, India. 2-methylimidazole and n-butylamine also required for the preparation of ZIF 8 nanocrystals were bought from Otto Group Hamburg, Germany, Polyamidieimide polymer was also purchased from UTM, Malaysia. Acetone was purchased from Merck Specialities Private Limited, Mumbai, India. All reagents were used without any further purification. Synthesis of ZIF 8 nanocrystals ZIF 8 nanoparticles were synthesized based on the procedure reported by Cravillon et al[3]. The ZIF-8 nanocrystals so formed was sent for UV spectroscopy, XRD, HRTEM and SEM analysis. Synthesis of CMS particles CMS particles were synthesized based on the procedure reported by De. Q. Vu et al[8] The CMS particles were then sent for XRD analysis. Synthesis of ZIF 8/PAI membranes Membranes of 3 different concentrations i.e., 1%, 2% and 3% of ZIF 8 nanocrystals were prepared by solution casting method. 17wt% of polyamideimide polymer solution was prepared by dissolving exactly 5.274g mixture of polyamideimide polymer i.e., Torlon and ZIF 8 nanocrystals in 25ml of NMP solvent in a beaker. A magnetic bead was cleaned and dried using acetone and was placed in the beaker. The 3 beakers containing the 3 different concentration solutions were kept on 3 different magnetic stirrer for complete dissolution. The exact amount of polymer and inorganic filler taken for respective concentrations is given in the table below: Table 1 Composition of ZIF 8/PAI membranes Concentration of ZIF 8/PAI Amount of PAI (g) Amount of ZIF 8 membranes (wt %) nanocrystals (g) 1 5.116 0.158 2 5.169 0.105 3 5.221 0.053 Now 3 glass plates and casting rods were washed and kept for drying. After drying the glass plates and the casting rods were cleaned and dried by using acetone. After complete dissolution the polymer solution in the 3 beakers were casted on 3 different glass plates using casting rods of 750 ÂÂ µm thickness. The glass plates after casting were allowed to dry at room temperature overnight for all the NMP solvent to evaporate. After drying the polymer membrane so formed was peeled off the glass plate. The membrane samples were sent for SEM analysis. Synthesis of CMS/PAI membranes Membranes of 3 different concentrations i.e., 1%, 2% and 3% of CMS particles were prepared by solution casting method. 17wt% of polyamideimide polymer solution was prepared by dissolving exactly 5.274g mixture of polyamideimide polymer i.e., Torlon and CMS particles in 25ml of NMP solvent in a beaker. The exact amount of polymer and inorganic filler taken for respective concentrations is given in the table below: Table 2 Composition of CMS/PAI membranes Concentration of ZIF 8/PAI Amount of PAI (g) Amount of CMS particles membranes (wt %) (g) 1 5.116 0.158 2 5.169 0.105 3 5.221 0.053 A magnetic bead was cleaned and dried using acetone and was placed in the beaker. The 3 beakers containing the 3 different concentration solutions were kept on 3 different magnetic stirrer for complete dissolution. Now 3 glass plates and casting rods were washed and kept for drying. After drying the glass plates and the casting rods were cleaned and dried by using acetone. After complete dissolution the polymer solution in the 3 beakers were casted on 3 different glass plates using casting rods of 750 ÂÂ µm thickness. The glass plates after casting were allowed to dry at room temperature overnight for all the NMP solvent to evaporate. After drying the polymer membrane so formed was peeled off the glass plate. The membrane samples were sent for SEM analysis. TESTING AND CHARACTERIZATION Confirmation tests for inorganic filers UV visible spectroscopy analysis. The ultraviolet-visible spectroscopy (UV-Vis)utilizes light to determine the absorbance or transmission of a chemical species in either solid or aqueous state. The UV Visible Spectroscopy analysis was done for the confirmation of ZIF 8 nanocrystals. XRD analysis. XRD can be done on a number of different kinds of samples. Smallvolume of sample was tapped on microscope slide glass. The intensity of the beam used was 40 kV and 40 mA. The XRD analysis was done for the confirmation of ZIF 8 nanocrystals and CMS particles. Morphological studies of Inorganic fillers and MMMs SEM with EDX analysis. The surface morphology of PAI polymer was observed usingthe JSM-6701F with high resolution field-emission scanning electron microscopy (FE-SEM) with the magnification of 5000ÃÆ'-. For EDX analysis the acceleration voltage was set to 20kV and the working distance was set to 14mm. The detector was moved down to 45mm. The sample was scanned by X-rays for a time of 200s. The elemental analysis of film in order to confirm the presence of carbon was done using an energy dispersive X-ray spectrometer (EDX) with magnification of 3000ÃÆ'- and acceleration voltage of 15 kV. After the scan was completed the spectrum was plotted using the data obtained from the scan. SEM with EDX was done for the confirmation of the CMS polymer film. TEM analysis. The sample preparation was done by sputtering the same with gold.Then the chamber door was opened and the sample was placed in the sample holder. The chamber door was closed and the required input like voltage, acceleration and time for scan were given to the system connected to the TEM analyzer. The scan was started and the results were recorded. TEM analysis was done for the size determination of the ZIF 8 nanocrsytals. FTIR analysis. Fourier transform infrared spectroscopy (FTIR) is a technique whichis used to obtain an infrared spectrum of absorption or emission of a solid, liquid or gas. An FTIR spectrometer simultaneously collects high spectral resolution data over a wide spectral range. Sulfonic acid group functionality of membrane was studied using attenuated -total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy (Thermo scientific Nicolet iS5 FTIR spectrometer). The spectra for all dried membranes were observed from the range from 4000 to 400 cm-1 wavelength. Mechanical strength test The material strength of the membranes prepared were studied by the performing Stress-Strain tests. The Universal Testing Machine was used to perform the tests. The samples of the membranes were cut into dimensions of height 30mm, width 10mm and thickness 0.45mm. The initial gauge length was set at 20mm. The samples were placed in a sample holder one at a time and the tests were performed. The data was recorded and the graphs were plotted for respective samples. Hydrophilic nature and Porosity determination test The hydrophilic or hydrophobic nature of the membranes were studied by immersing a 1cmx1cm membrane samples in different beakers each containing 20ml water. The beakers were kept on a rotary shaker for continuous mixing overnight. After 24 hours the membrane samples were taken out and the weight of the wet membranes were measured using a digital weighing balance. After that the membranes samples were dried in a vacuum oven at 60oC for 6 hours and then the weight of the dry membranes were measured similarly. The amount of water absorbed and the average porosity of the membranes were determined and the results were tabulated. RESULTS AND DISCUSSION Confirmation of ZIF 8 Nanocrystals The UV Visible Spectroscopy analysis was done for the primary confirmation of ZIF 8 nanocrystals. UV of ZIF 8 nanocrystals 12 10 Absorbance 8 6 4 2 0 200 212 224 236 248 260 272 284 296 308 320 332 344 356 368 380 392 404 416 428 440 452 464 476 488 500 512 524 536 548 560 572 584 596 Wavelength Series1 Figure 1 UV visible spectroscopy result of ZIF 8 nanocrystals The penetration depth was found to be directly proportional to the exciting wavelength i.e., 325nm because of decreased absorbance which is in accordance with the reference paper, Liu et aL, (2013)[1]. Therefore we can confirm that its ZIF 8 nanocrystals. The XRD analysis was done for the secondary confirmation of ZIF 8 nanocrystals. Figure 2 XRD result of ZIF 8 nanocrystals When n-butylamine is added as the modulating ligand, nearly instantaneous formation of a solid is observed upon combining the component solutions, and pure-phase ZIF-8 nanocrystals are recovered after 24 h (see XRD pattern in Figure 2). An average size of 18 nm is estimated from the broadening of the Bragg reflections. The XRD results were also in accordance with the reference paper Cravillon et aL, (2011). Hence we can confirm that the particles synthesized were ZIF 8 nanocrystals. Morphology of ZIF 8 Nanocrystals ZIF materials constitute a new distinctive, rapidly developing subclass of crystalline porous coordination polymers (PCPs) or metal organic frameworks (MOFs). The tetrahedral framework structures of ZIFs are constructed from bivalent metal cations and bridging substituted imidazolate anions and frequently possess a zeolite topology. Numerous ZIFs combine the attractive features of MOFs (diversity of framework structures and pore systems, large surface areas, post-synthetically modifiable organic bridging ligands) with high thermal and chemical stability. Figure 3 SEM image of ZIF 8 nanocrystals It is this combination of properties which makes ZIFs very promising candidate materials for many technological applications. Properties and performance of porous materials rely much on their supply as nano and microcrystals of well-defined size and shape, as is well-known for zeolites. SEM images (Figure 3) reveal that the well-defined nanocrystals have a rhombic dodecahedral shape crystal structure. Figure 4 TEM image of ZIF 8 nanocrystals TEM images (Figure 4) show roughly spherical particles being Confirmation of CMS Particles It is not possible to directly measure permeation properties of CMS particles as with CMS films, replicate mixed matrix films prepared with the two different sieves give very similar effective mixed matrix film permeation properties using powder-pyrolyzed sieves versus the film-pyrolyzed sieves. XRD was performed on the CMS films and powder, as shown in Fig. 5. The XRD diffractograms show very similar peaks and d-spacings, suggesting similar planar dimensions between the film-pyrolyzed CMS and the powder-pyrolyzed CMS, thereby confirming that the particles produced were CMS particles. CMS particles Polymer film Figure 5 XRD results of CMS particles and CMS polymer film Surface Morphology of CMS Polymer Film The CMS membrane films have an intrinsic CO2/CH4 selectivity of 200 with a CO2 permeability of 44 Barrers at 35oC. For UltemÂÂ ®-CMS mixed matrix membrane films, pure gas permeation tests show enhancements by as much as 40% in CO2/CH4 selectivity over the intrinsic CO2/CH4 selectivity of the pure UltemÂÂ ® polymer matrix. Likewise, for MatrimidÂÂ ®- CMS mixed matrix films, enhancements by as much as 45% in CO2/CH4 selectivity were observed. Effective permeabilities of the fast-gas penetrants (O2 and CO2) through the mixed matrix membranes were also significantly enhanced over the intrinsic permeabilities of the UltemÂÂ ® and MatrimidÂÂ ® polymer matrices. These encouraging selectivity and permeability enhancements confirm that mixed matrix membrane behaviour is achievable with CMS particles. Figure 6 SEM image of CMS polymer film Fig. 6 shows top surface SEM micrographs of a CMS polymer film. These micrographs show a smooth surface without any defects. Figure 7 EDX result of CMS polymer film The table below shows the EDX analysis of the CMS polymer film. The sharp Silicon peak is present due to the Silicon detector used during the EDX analysis. Table 3 EDX result of CMS polymer film Element Series unn. C norm. C Atom. C Error (3 [wt.%] [wt.%] [at.%] Sigma) [wt.%] Carbon K-series 8.50 23.61 36.45 4.40 Oxygen K-series 9.89 27.46 31.82 4.26 Sodium K-series 1.16 3.22 2.60 0.31 Aluminium K-series 4.56 12.67 8.70 0.74 Silicon K-series 9.37 26.03 17.19 1.28 Calcium K-series 2.52 7.01 3.24 0.31 Total: 36.01 100.00 100.00 The Oxygen peak is due to the oxygen present in the atmosphere during EDX analysis. The Carbon peak denotes the confirmation of the CMS polymer film prepared. As expected it shows a maximum wt % of 23.61. Cross Sectional Morphology of CMS/PAI Membranes Scanning electron micrographs of the CMS fibers are shown in figures 8, 9 and 10 Figure 4.8 SEM image of 1% CMS/PAI membrane Although asymmetry appeared to be present in the CMS fiber morphology, the thicknesses of the layers were markedly different from each other and from those of the precursor fibers (compare with those of the precursor fibers in Figure 6). The original polymeric precursor fibers consisted of a very thin dense skin (1000-2000 Ã…) on a porous core. This skin layer in polymeric fibers has been observed at very high resolution under SEM. In figure 8, high magnification of the wall in the cross section of the PAI CMS fiber reveals a gradual transition from the porous inner core to the denser outer micropore structure. In contrast, high magnification of the PAI CMS fiber shows a uniform dense micropore structure in figure 9. Figure 9 SEM image of 2% CMS/PAI membrane Figures 8, 9 and 10 show SEM micrographs of a mixed matrix film after these modifications. These micrographs demonstrate smaller CMS particles (mostly Figure 10 SEM image of 3% CMS/PAI membrane Cross Sectional Morphology of ZIF 8/PAI Membranes Figures 11, 12 and 13 shows SEM images of ZIF-8/PAI mixed matrix dense films, which indicates good contact of bare ZIF-8 to the PAI matrix without sieve-in-a-cage morphology at each loading. It is noteworthy that the good contact was achieved without any surface treatment of the sieve. This should be due to the hydrophobic nature of ZIF-8, proved by TGA measurements in reference paper Zhang et. al. (2012). Interestingly, in the SEM images of ZIF-8/PAI mixed matrix dense films, as shown in figures 11, 12 and 13, we observe a morphology that has not been previously reported in mixed matrix membranes prepared with other molecular sieves. Other than well-dispersed 10 nm ZIF-8 particles, there also exist many non-ideal large clusters of ZIF-8 with size ranging from 50 nm to several microns, which is more than an order of magnitude larger than single ZIF-8 particles. Also, volume fraction of large ZIF-8 clusters in the matrix increases with increasing ZIF-8 loading. Figure 11 SEM image of 1% ZIF 8/PAI membrane Unlike agglomerations of molecular sieve particles that have been previously reported in mixed matrix membranes prepared with other molecular sieves, the surface of these large ZIF-8 clusters as revealed in figures 11, 12 and 13 looks fairly smooth. Also, almost no defects were observed for these clusters among all the ZIF-8/PAI dense film samples. Since film samples were randomly fractured for SEM analysis, we believe that the mostly non-defective feature of these large ZIF-8 clusters shown in figures 11, 12 and 13 is representative of their interior structures. It is important to understand the formation mechanism of these large ZIF-8 clusters and their impacts on gas transport properties of the mixed matrix membrane to allow extension to practical asymmetric structures. By achieving the desired uniform distribution of individual ZIF-8 particles with the PAI matrix we can achieve outstanding gas separation results. Figure 12 SEM image of 2% ZIF 8/PAI membrane Figure 13 SEM image of 3% ZIF 8/PAI membrane The cross sectional view of the ZIF 8/PAI membranes shows good adhesion between the inorganic filler ZIF 8 and the polymeric membrane PAI. The figures show the SEM images of 1%, 2% and 3% ZIF 8/PAI membranes prepared respectively. FTIR Analysis of ZIF 8/PAI membranes The FTIR results shows that the aluminosilicates are present in the ZIF 8/PAI membranes prepared. The aluminosilicates are present due to the presence of ZIF 8 nanocrystals. FTIR Results Conjugated cyclic Aluminosilicates 120 100 %T 80 Unsaturated aromatic 60 40 20 ketoaldehydes or enols dimer esters and lactones 0 3691 2970 4000 3897 3794 3588 3485 3382 3279 3176 3073 2867 2764 2661 2558 2455 2352 2249 2146 2043 1940 1837 1734 1631 1528 1425 1322 1219 1116 1013 910 807 704 601 498 cm-1 Series1 Series2 Series3 FTIR Analysis of CMS/PAI membranes The FTIR results shows that the carbon bonds are present in the CMS/PAI membranes prepared. The carbon bonds are present due to the presence of CMS particles. FTIR Results Carbon bonds 120 100 %T 80 60 unsaturated aromatic 40 dimer ketoaldehydes or enols 20 0 Conjugated cyclic esters and lactones 3691 2970 4000 3897 3794 3588 3485 3382 3279 3176 3073 2867 2764 2661 2558 2455 2352 2249 2146 2043 1940 1837 1734 1631 1528 1425 1322 1219 1116

Kennedy’s New Frontier Program

In November 1960, majority of the American population voted John F. Kennedy into presidency. Opposite to the tactics used by his opponent com/richard-nixon-and-supreme-court/">Richard Nixon who emphasized his experience during the Eisenhower administration, Kennedy called to incorporate new tactics to leadership and new ways to effectively use their country's rich economic and human resources (â€Å"An Outline of American History† 12-20). In Kennedy's inauguration speech, he spoke of a â€Å"New Frontier. In general, Kennedy's government through the programs incorporated with the New Frontier was dedicated towards creating ways to boost their economy, to strengthen their national defense and to extend international aid towards their allies. In this light, his administration passed several bills and policies that sought to improve their economic status, while giving a close look at the country's housing status, wage level and unemployment level, provision of social services an d improving the defense system and battling to decrease the crime rate. However, his desire to extend the fruits of economic success with the American citizens was thwarted by the mere fact that he won the presidency in such a narrow margin. His opponents from the Conservative Party and southerners resisted the plans that he carried out for his administration. Further, although one of his strongest priorities is to end economic recession and in turn restore economic growth, price increase in the steel indusry has lost him support from business leaders in the country. Moreover, in the area of civil and social rights, Kennedy fell short from providing the citizens with adequate and quality healthcare, education, international aid and space program (â€Å"Kennedy and the New Frontier†). However, despite these shortcomings, hindrances and deficits, he was able to bring judgment with the Cuban Missile Crisis which during that era was one of the most pressing international issues. This earned him a great popularity not only among the Americans, but for people from other countries as well. As such, towards the end of his term, he further initiated some measures that are thought to become beneficial for their country. Unfortunately though, on November 1963, he was assassinated. Despite his death, the liberal reputation he gained through his style and ideas continued. The agendas that he intended to implement before his death continued to become a liberal force of change for the Americans.

Earthworms

An earthworm can grow only so long. A well-fed adult will depend on what kind of worm it is, how many segments it has, how old it is and how well fed it is. An Lumbricus terrestris will be from 90-300 millimeters long. A worm has no arms, legs or eyes. There are approximately 2,700 different kinds of earthworms. Worms live where there is food, moisture, oxygen and a favorable temperature. If they don’t have these things, they go somewhere else. In one acre of land, there can be more than a million earthworms. The largest earthworm ever found was in South Africa and measured 22 feet from its nose to the tip of its tail. Worms tunnel deeply in the soil and bring subsoil closer to the surface mixing it with the topsoil. Slime, a secretion of earthworms, contains nitrogen. Nitrogen is an important nutrient for plants. The sticky slime helps to hold clusters of soil particles together in formations called aggregates. Charles Darwin spent 39 years studying earthworms more than 100 years ago. Worms are cold-blooded animals. Earthworms have the ability to replace or replicate lost segments. This ability varies greatly depending on the species of worm you have, the amount of damage to the worm and where it is cut. It may be easy for a worm to replace a lost tail, but may be very difficult or impossible to replace a lost head if things are not just right. Baby worms are not born. They hatch from cocoons smaller than a grain of rice. The Australian Gippsland Earthworm grows to 12 feet long and can weigh 1-1/2 pounds. Even though worms don’t have eyes, they can sense light, especially at their anterior (front end). They move away from light and will become paralyzed if exposed to light for too long (approximately one hour). If a worm’s skin dries out, it will die. Worms are hermaphrodites. Each worm has both male and female organs. Worms mate by joining their clitella (swollen area near the head of a mature worm) and exchanging sperm. Then each worm forms an egg capsule in its clitellum. Worms can eat their weight each day.

Balustrades, Balusters, and How to Preserve Them

A baluster has come to be known as any vertical brace (often a decorative post) between an upper and lower horizontal railing. The purposes of the baluster  (pronounced BAL-us-ter) include safety, support, and beauty. Staircases and porches often have rails of balusters called balustrades.   A balustrade is a row of repeating balusters, similar to a colonnade being a row of columns. What we call a balustrade today is historically a decorative extension of the Classical Greek colonnade on a smaller scale. The invention of the balustrade is generally thought to be a feature of Renaissance architecture. One example is the balustrade of the 16th century Basilica St. Peters at the Vatican. Todays balusters are constructed of wood, stone, concrete, plaster, cast iron or other metal, glass, and plastics. Balusters can be rectangular or turned (i.e., shaped on a lathe). Today any decorative patterned grille or cutout (patterned after the Roman lattice) between railings are referred to as balusters. Balusters as architectural details are found in homes, mansions, and public buildings, inside and outside. The Baluster Shape: Balustrade (pronounced BAL-us-trade) has come to mean any series of vertical bracings between rails, including spindles and simple posts. The word itself reveals a certain design intention. Baluster is really a shape, coming from the Greek and Latin words for a wild pomegranate flower. Pomegranates are ancient fruits indigenous to the Mediterranean, Middle East, India, and Asia, which is why you find the baluster shape in these areas of the world. Having hundreds of seeds, pomegranates also have long been symbols of fertility, so when ancient civilizations decorated their architecture with objects from nature (e.g., the top of a Corinthian column is decorated with acanthus leaves), the shapely baluster was a good decorative choice. What we call the baluster shape was depicted in pottery and jugs and wall carving in many parts of the world from the earliest civilizations—the potters wheel was invented around 3,500 BC, so wheel-turned shapely water jugs and baluster vases were more easily produced—but the baluster was not used in architecture until thousands of years later, during the Renaissance. After the Middle Ages, from roughly 1300 until 1600, a new interest in Classical design was reborn, including the baluster design. Architects like Vignola, Michelangelo, and Palladio incorporated the baluster design into Renaissance architecture, and today balusters and balustrades are considered the architectural detail itself. In fact, our common word banister is a corruption or mispronunciation of baluster. Preservation of Balustrades: Exterior balustrades are obviously more susceptible to decay and deterioration than interior balustrades. Proper design, manufacturing, installation, and regular maintenance are keys to their preservation. The US General Services Administration (GSA) defines balustrade by its components, consisting of the handrail, footrail and balusters. The handrail and footrail are joined at the ends to a column or post.   The balusters are vertical members that connect the rails. Wooden balustrades are subject to deterioration for a number of reasons, including exposed end grain from the manufacturing process and butt joints that are prone to moisture. Regular inspection and maintenance of a well-designed balustrade are the keys to continued care and preservation. A wooden balustrade in proper condition is rigid and free from decay, the GSA reminds us. It is designed with sloping surfaces to repel water and has properly caulked, tight joints. Exterior cast stone (i.e., concrete) balusters will have moisture problems if not designed and installed properly and if not routinely inspected. Balusters come in many shapes and sizes, and the quality of construction and thickness of the balusters neck may affect its integrity. The variables involved in manufacture are considerable, and it is wise to use a firm with experience in ornamental and custom work rather than a precast concrete firm which manufactures stock structural items, suggests preservationist Richard Pieper. The Case for Preservation: So, why preserve balustrades in public buildings or on your own home? Why not just cover them up, encase them in metal or plastic and protect them from environmental hazards? Balustrades and railings are not only practical and safety features, write preservationist John Leeke and architectural historian Aleca Sullivan, they typically are highly visible decorative elements. Unfortunately, balustrades and balusters are frequently altered, covered, removed or completely replaced even though in most cases they can be repaired in a cost-effective manner. Routine cleaning, patching, and painting will preserve all kinds of balustrades. Replacement should be a last resort only. To preserve historic fabric, the repair of old balustrades and railings is always the preferred approach, Leeke and Sullivan remind us. A broken baluster usually is one in need of repair, not replacement. Sources: Baluster, Illustrated Architecture Dictionary, Buffalo Architecture and History; Classical Comments: Balusters by Calder Loth, Senior Architectural Historian for the Virginia Department of Historic Resources; Securing An Exterior Wooden Balustrade, U.S. General Services Administration, November 5, 2014; Removing And Replacing Deteriorated Cast Stone Balusters, U.S. General Services Administration, December 23, 2014; Preserving Historic Wood Porches by Aleca Sullivan and John Leeke, National Park Service, October 2006; The Maintenance, Repair and Replacement of Historic Cast Stone by Richard Pieper, National Park Service, September 2001 [accessed December 18, 2016]