One  of  the  most  concerns  associated  with  many  commercially  available  composites  is  that  they  used  of  non-degradable resins and fibers that primarily made using non-degradable, petroleum-based chemicals as feed stock. These conditions will create a serious problem in term of waste disposal after end of their life. Unlike petroleum, plant  based  protein  and  starches  are  yearly  renewable.  These  resins  are  increasingly  developed  for  various applications  as  replacements  for  non-degradable  petroleum  based  resins. In  addition,  these  resins  may  be  easily composted  after  their  life.  In  this  study,  Soybean  Pulp  Hemi-cellulose  (SPH)  was  modified  by  cross-linking  it with  glutaraldehyde  (GA).  The  modified  SPH  resins  were  characterized  for  its  surface  morphology,  tensile  and mass  losses  or  biodegradability  properties.  The  effect  of  GA  on  the  surface  morphology,  tensile  and biodegradability  of  the  SPH  resins  were  discussed.  The  SPH  resins  showed  improved  surface  morphology  and ductility.  However,  the  increasing  the  GA  content reduces the Young’s modulus of the SPH resins. The SPH resins exhibited fracture stress point and Young’s modulus maximum of and 3.02 MN/m2,  respectively,  and biodegradability  of  40.42%  after  30  days  placed  on  the  open  air.  These  properties  seem  to  be  sufficient  for developing green composites from the SPH resins reinforced with natural fiber for indoor structural application

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[32] J.Trop.Life.Science.    Vol I. No 1. Oct, 2010      Development  of  Green  Resin  Using  Solid  Waste  Protein  Soybean  Curd  “Tofu” Production   Sujito1*  1 Department of Physics, Faculty of Mathematics and Natural Sciences, University of Jember, Jember, Indonesia     Abstract  One of the most concerns associated with many commercially available composites is that they used of non-degradable resins and fibers that primarily made using non-degradable, petroleum-based chemicals as feed stock. These conditions will create a serious problem in term of waste disposal after end of their life. Unlike petroleum, plant  based  protein  and  starches  are  yearly  renewable.  These  resins  are  increasingly  developed  for  various applications as replacements for non-degradable petroleum based resins. In addition, these resins may be easily composted after their life. In this study, Soybean Pulp Hemi-cellulose (SPH) was modified by cross-linking it with glutaraldehyde (GA). The modified SPH resins were characterized for its surface morphology, tensile and mass  losses  or  biodegradability  properties.  The  effect  of  GA  on  the  surface  morphology,  tensile  and biodegradability of the SPH resins were discussed. The SPH resins showed improved surface morphology and ductility. However, the increasing the GA content reduces the Young’s modulus of the SPH resins. The SPH resins exhibited fracture stress point and Young’s modulus maximum of and 3.02 MN/m2, respectively, and biodegradability of 40.42% after 30 days placed on the open air. These properties seem to be sufficient for developing green composites from the SPH resins reinforced with natural fiber for indoor structural applications.   Keywords: Green Resin, Soybean Pulp Hemi-cellulose (SPH), Mechanical Properties, Biodegradation.     Introduction   Fiber  reinforced  composite  materials  have replaced  metals  in  many  applications.  Initially developed  for  the  aerospace  applications because of their light weight and the ability to manipulate the properties in various directions as desired, composites technology has matured in the past few decades. Currently they are being used  in  a  multitude  of  applications  from automotive  parts  to  circuit  boards  and  from sporting  goods  to  household  appliances.  At present  they  are  also  being  used  in  civil  and structural  applications  including  buildings  and bridges. One of the major concerns associated with most commercially available composites is that  they  use  non-degradable  fibers  and  resins that are primarily made using petroleum as feed stock.  In  most  cases,  non-degradability  is required.  However,  their  non-degradability  has also created a serious problem in terms of waste disposal.  Since  composites  are  fabricated  by combining  two  dissimilar  materials  they  are  difficult  to  be recycled or reused. While a small        fraction  of  the  composites  is  incinerated  to recover the energy value or crushed into powder and used as filler, most composites end up in landfills, at the end of their useful life, making that  land  unusable  for  several  decades  at  the least. Both incineration and landfill disposal are environmentally  unsound,  wasteful  and expensive.  Further,  at  the  current  rate  of consumption of the oil, by some estimates, the world reserves are expected only for the next 50 years or less [1]. In  response  to  the  concerns  mentioned above there have been efforts to develop non-petroleum  based  composites  that  are environment friendly and fully sustainable, using plant  based  fibers  and  resins.  Biodegradable resins produced from renewable resources such as  plants,  animal  and  microbes  through biochemical  reactions  offer  a  convenient  and environment friendly solution to the problem of plastic waste. Various biodegradable resins such as starch, wheat gluten, whey protein, and soy protein  have  been  explored  for  application  in making composites [2-6]. Compare with others, soy  protein  offers  several  advantages  over synthetic  resins  [7].  First,  the  soy  protein purification process is benign and environment friendly. Second, these proteins can form ductile and viscous polymers that can be used as resins. Third, the cost of raw materials is low. Fourth, *Corresponding address:   Sujito   Department of Physics, University of Jember,   East Java, Indonesia   Email: sujito.fmipa@unej.ac.id    Sujito, 2010  [33] J.Trop.Life.Science.    Vol I. No 1. Oct, 2010   soybean  is  an  annual  crop  and  is  abundantly available worldwide. In the 1930s, Henry Ford pioneered the use of soy protein for plastic and fibers [8]. Ford used soy plastic for various car parts such as gear shift knobs, horn buttons and window  frames  in  an  effort  to  produce  an  all agricultural car. However, these efforts are stop it because of World War II. At present, because of  the  increased  environment  awareness  and stringent  environmental  laws,  most manufactures  are  looking  towards  greener  and more  environment  friendly  alternatives  for conventional polymers and composites [9].  Soybean products are available commercially as  defatted  soy  flour  (SF),  soy  protein  isolate (SPI),  and  soy  protein  concentrate  (SPC). Chemically, SF, which requires less purification, contains  about  55%  protein  and  32% carbohydrate, SPC contains 70% protein and 18% carbohydrate,  while  SPI  contains  90%  protein and  4%  carbohydrate.  Soy  protein  consists  of various polar and reactive amino acids such as cystine, arginin, lysine, and hystidine which can be used for cross-linking it and improving the tensile  and  thermal  properties.  Several researchers  [10-12]  have  shown  that glutaraldehyde (GA) react with the amine groups in protein, particularly in an alkaline pH, to form intermolecular  cross-links.  Although  GA  can readily  react  with  the  amine  groups,  there  has been no agreement on the reaction of protein with  GA.  Different  mechanisms  have  been proposed  for  explaining  the  reaction  between GA and proteins. Blass  et al. [12] have shown that monomeric GA binds reversibly to proteins. Habeeb  and  Hiramoto  [11]  reported  that  GA reacted  extensively  with-amino  group  of glycine and the - and-amino groups of lysine, while  it  only  partially  reacted  with  amino groups  of  histidine  and  tyrosine.  Chabba  and Netravalli  [13]  cross-linked  SPC  using  GA  to form  suitable  resin  system.  As  a  result  of  the cross-linking,  the  strength  of  the  SPC  resin increased  significantly  while  the  moisture absorption decreased. In  the  mean  time,  large  quantities  of  solid wastes,  named  Soybean  Pulp  Hemi-cellulose (SPH)  were  discarded  during  protein  soybean curd “tofu” production. In Indonesia, about 1.2 million  tons/year  SPH  were  produced  and discarded as organic wastes. Only few amounts of SPH wastes were utilized as feed supplement. Investigation showed that fresh SPH contain 75-  80% of water content, but dried SPH consist of carbohydrates as hemi-cellulose 50-55%, protein 25-30% and lipid 10-15% so that this could be reasonably  recovered  and  utilized  by  isolating the  protein  from  the  SPH  to  produce  fully sustainable and biodegradable green resins.  Based on the above descriptions, modified of soy protein from the SPH using GA as cross-linking  agent  and  glycerin  as  a  plasticizer,  to produce  fully  biodegradable  and  sustainable resin, mechanical and biodegradation properties of these resins will be carried out.   Experimental Methods   Soybean protein hemi-cellulose (SPH) from the  solid  waste  “tofu”  production  around Jember was modified with GA. GA was used as cross-linking agent to obtain better mechanical and physical properties [12]. To process SPH to be resin, SPH powder was mixed with distilled water in ratio of 1:8 and 15% glycerin (by SPH weight)  was  added  as  plasticizer.  The  mixture was homogenized by using a magnetic stirrer for 30 minutes. After homogenizing, the pH of the mixture  was  adjusted  to  11  using  0.2  m/liter NaOH  solution.  To  obtain  modified  soybean protein hemi-cellulose (MSPH), 30%, 40% and 50% of GA (by weight of SPH) was added. The mixture  of  MSPH  was  then  pre-cured  for  30 minutes at 700C, poured on Teflon coated sheets and  dried  at  room  temperature.    The  final MSPH resin curing was done for the pre-cured, the dried MSPH resin sheets in a hot press at 1200C for 30 minutes.  Surface  morphology  of  MSPH  resins  were characterized  by  using  Dino  Lite  Optical Microscope. Tensile properties of MSPH resin sheets  were  characterized  in  accordance  with ASTM D 638. Conditioned resin sheets were cut into rectangular specimens of 20 mm x 180 mm x  10  mm  dimensions.  Three  thickness measurements were carried out along the length of  each  specimen  and  the  average  of  these values was used for calculating the fracture stress and Young’s modulus. The tests were performed on  tensile  tester,  model  TM  113  Universal  30 KN.  In the mean time, biodegradability of the SPH resins was evaluated by characterizing the mass changes after placed in the open air during 30 days. The mass changes of the SPH resins were calculated using equation (1) below.  100% xmm mdDif i      (1) dD = Degree of degradation. mi   = Mass of SPH resin before composting. mf   = Mass of SPH resin after composting. Full Article : Development of Green Resin Using Solid Waste Protein Soybean Curd “Tofu” Production   [34] J.Trop.Life.Science.    Vol I. No 1. Oct, 2010   Results and Discussion  Figure  1  shows  typical  Optical  Microscope photomicrographs of the surface morphology of the SPH resin containing 15% glycerin and (a) 30%  GA,  (b)  40%  GA,  and  (c)  50%  GA.  As shown in the photomicrograph, the SPH resin with 50% GA showed lower roughness at the surface  morphology  as  compared  to  the  SPH resin  with  30%  GA.  The  improved  of  the surface morphology of SPH resins is attributed to  the  cross-linking  between  GA  and  SPH.  It was,  however,  difficult  to  assess  the  average degree  of  cross-linking  because  of  the complexity of the chemistry. The cross-linking was  judged  based  on  the  improved  tensile strength and moisture absorption after the GA modification as well as the significant increase in the viscosity immediately following the addition of GA to the SPH solution.                        (a)                                           (b)                                                 (c) Figure  1. Photomicrograph  showing the  surface  morphology  of MSPH resin containing (a) 15% glycerin and 30% GA; (b) 15% glycerin and 40% GA; and (c ). 15% glycerin and 50% GA.    Figure 2. Typical stress versus strain plot for the MSPH resins with 15% glycerin and 30%, 40% and 50% GA .  Figure 2 shows the typical stress versus strain plot for the SPH resins containing 15% glycerin obtained  from  the  Universal    tensile  tester model 113 30 KN.  This  result  was  agreed  with  the  theoretical predictions. As shown in the Figure 2 above, for small values of the strain, the stress-strain graph is a straight line; the stress is proportional to the strain . In general, this is called the linear region for material. Beyond the linear limit a, the stress is no longer linearly proportional to the strain. However, from a to the elastic limit or yield point b, the SPH resins still returns to its original dimensions when the applied force F is removed. The deformation up to b is said to be elastic.  When  the  applied  force  is  further increased,  the  strain  increases  rapidly.  In  this region,  if  the  applied  force  is  removed,  the object does not return completely to its original dimensions; it retains a permanent deformation. The  point  c  on  the  stress-strain  graph  is  the ultimate tension strengthy of the MSPH resins. Beyond  this  point  fracture  occurs  at  point  d. From b to d the MSPH resins is said to undergo plastic  deformation.  In  general,  if  the  ultimate tension strength and fracture points c and d are close together, the material is brittle; if they are far apart the material is said to be ductile. Figure 3 shows stress associated with a given strain for the MSPH resin containing 15 % of glycerin and 30%, 40% and 50% GA. It is clear from Figure 3 that increasing GA content from 30%  to  50%  leads  to  increase  in  the  fracture stress and the fracture strain points from 1.281 MN/m2  to  2.401 MN/m2 and  10.0 % to  and 18.3 % , respectively. It should be noted from Figure 3 that increasing the GA contents on the SPH resins leads to increase in distance between ultimate  tension  strength  point  c  and  fracture stress  point  d. This  means  that  increasing  the GA  contents  on  the  SPH  resins  to  cause increasing ductility of the SPH resins.   Figure 3. Stress versus strain plots for modified SPH resin with containing  15%  of  glycerin  and  30%,  40%,  and  50%  of glutaraldehyde (GA).   Sujito, 2010  [35] J.Trop.Life.Science.    Vol I. No 1. Oct, 2010   Tensile  properties  such  as  tension  strength (),  strain  and  Young’s  modulus  (E)  of  SPH resins are summarized in Table 1. It is evident from these data that increasing the GA content from 30% to 50% increases UTS of the SPH resin  from  1.30  MN/m2  to  2.09  MN/m2, however,  Young’s  modulus  of  the  SPH  resin decreases  from  3.02 MN/m2  to  2.82  MN/m2. These confirms that the GA is an good cross-linking  although  in  the  special  case  further increasing  GA  content  does  not  improve  the tensile  property.    Table 1. Values of tension strength (y), strain (y ), and Young’s Modulus (E) of SPH resins    Table  2  summarizes  the  effect  of  the  GA mass loss or degree of degradation of the SPH resins after 30 days placed on the open air. It is evident  from  Table  2  that  increasing  the  GA content  reduces  the  mass  loss  of  SPH  resins. The  SPH  resin  with  containing  30%  GA  was lost 40.42% of mass after 30 days placed in the open air.   Table 2. Mass loss (degrees of degradation) of SPH resins after composting   Very  limited  information,  however,  is available on the biodegradability of green resins in soil or other environments. Takagi and Ochi [14] examined weight loss of biodegradable resin as a function of composting time. They found that the weight loss rate was very slow in the initial period of up to 15 days but accelerated after that. The weight loss of the biodegradable resin after 30 days composting was found 15%. One important point to be noted is the use of the  biodegradable  resins  in  making  green composites  has  considerable  advantages  in enhancing their biodegradability.  Conclusions  It  has  been  successfully  developed  resin  from modified  SPH  with  GA  to  give  better mechanical  properties.  As  the  petroleum supplies  dwindle  and  get  costlier,  plant  based biodegradable resin will become cost effective. It is also expected that the SPH resin may be used in  development  of  fully  biodegradable composites with good mechanical properties so it  can  be  use  in  many  applications,  likes  for packaging  and  panels  for  indoor  and  outdoor applications, secondary structural applications in automotive and housing.   Acknowledgments  The author thank to Sumarji, MT., Department of  Mechanical  Engineering,  Faculty  of Engineering  University  of  Jember  for  helping the tensile test measurements. Thanks also to my students  Naning,  Bobby  and  Mahrus  for providing SPH powders.   References [1]   Stevens ES Green Plastics, Princeton University Press, Princeton, 2002. [2]  Miller KS, Chiang MT, Krochta JM. Heat curing of whey protein films, J. Food Sci. 1997; 62(6): 1189-1193. [3]   Lodha P, Netravali AN. Characterization of interfacial and mechanical properties of green composites with soy protein isolate and ramie fiber, J. Mater. Sci. 2002; 37: 3657-3665.  [4]    Nam  S,  Netravali  AN.  Interfacial  and  mechanical properties  of  ramie  fiber  and  soy  protein  “green” composites,  ICCE-9,  San  Diego,  California,  ed.  D. Hui, 2002; 551-552. [5]      Genadios  A,  Weller  CL.  Edible  films  and  coatings from wheat and corn proteins, Food Technol 1990; 44 (10): 63-69. [6]  Takagi  H,  Winoto  CW,  Netravali  AN.  Tensile properties  of  starch  based  “green”  composites reinforced  with  randomly  oriented  discontinuous MAO  fibers,  International  Workshop  on  “Green” Composites, Japan, 4-7.  2002. [7]    Liang  F.  Wang  Y,  Sun  XS.  Curing  process  and mechanical  properties  of  protein  based  polymer,  J. Polym. Eng. 1998; 19(6): 162-163. [8]    Johnson LA, Myers DJ. Industrial uses for soybeans in Practical Handbook of Soybean Processing and Utilization, ed.  D.  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Development of Green Resin Using Solid Waste Protein Soybean Curd “Tofu” Production

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