Thermal Properties of Green Polymers and Biocomposites Part 10 pdf

Chapter 8 BIO- AND GEO-COMPOSITES CONTAINING PLANT MATERIALS 1. BIOCOMPOSITES CONTAINING CELLULOSE POWDER AND WOOD MEAL The polyurethanes (PU’s) which were prepared from saccharides and lignin showed excellent mechanical and thermal properties [1-10]. They are biodegraded by microorganisms when placed in soil [11]. In this section, composites that are prepared from the above PU’s and ground plant particles or powder, such as cellulose powder (CP) and wood meal (WM) are described. Mechanical and thermal properties of the above composites are also cosidered. 1.1 Preparation PU composites can be prepared according to the scheme shown in Figure 8-1 [7]. As shown in Figure 8-1, cellulose powder or wood meal is mixed with polyols containing molasses. The suspensions with various mixing ratios from 10, 20, 30, 40, 50, 60, 70, 80 and 90 wt % of cellulose powder or wood meal in molasses polyol (MLP) are first prepared [7]. MDI is added to the suspension under stirring and PU composites are prepared. After drying at room temperature, the sample is cured at 393 K for 2 hrs. 306 Chapter 8 MDI Suspension Molasses Polyol Wood Meal Cellulose Powder PU Composites NCO/OH = 1.2 Filler Contents = 10 - 90 wt% Figure 8-1. Preparation scheme of polyurethane composites (PU composites) [7]. 1.2 Thermal and mechanical properties Figure 8-2 shows change of the density ( ρ ) of PU composites prepared from cellulose powder and wood meal with the powder content. The density reaches a maximum when the content of plant particles in the composites is from ca.50 % to 70 %. 0.0 0.4 0.8 1.2 0 20406080100 Plant Powder Content / % ȡ / g cm -3 Figure 8-2. Change of the apparent density ( ρ / g cm -3 ) with cellulose powder and wood meal contents in MLP. ٨ : wood meal ٤ : cellulose powder. Apparent density ( ρ ) was measured using a digital solar caliper and an electronic balance. Size of the composite sample was 40- 60 mm (length), 20-30 mm (width) and 20-30mm (thickness). Figure 8-3 shows change of σ with cellulose and wood meal contents in PU composites. As seen from the figure, σ increases with increasing plant powder contents in PU composites, reaches a maximum, and then decreases. Bio- and Geo-composites Containing Plant Materials 307 0 5 10 15 20 25 30 35 0 20406080100 Plant Powder Content / % ı c / MPa Figure 8-3. Change of compression strength ( σ c ) with cellulose powder and wood meal contents in MLP. Ɣ: wood meal, ż: cellulose powder Compression measurements were carried out using a Shimadzu Autograph AG 2000-D at room temperature. Test specimens were a rectangular solid, and the added stress was less than 10 MPa min -1 . Compression stress ( σ ) was defined at the final point of linear compression in the stress-strain curve. Static Young’s modulus (E) was calculated using the initial stage of compression curves. Conditions in detail accorded with the Japanese Industrial Standard (JIS Z-2101). 0 5 10 15 20 25 30 35 0 0.2 0.4 0.6 0.8 1 1.2 ȡ / g cm -3 ı c / MPa Figure 8-4. Change of compression strength ( σ ) with density ( ρ ) of PU composites obtained from cellulose powder and wood meal. ٨: wood meal, ٤: cellulose powder. Figure 8-4 shows change of σ with ρ of PU composites obtained from cellulose powder and wood meal. As seen from the figure, σ increases with increasing ρ of PU composites. The above results suggest that the mechanical properties of PU composites from plant powder have a strong relationship with the density of composites: that is to say, the highest mechanical properties are observed when the density of PU composite becomes the highest value. 308 Chapter 8 Figure 8-5. DTG curves of wood meal-MLP type PU composites. Measurements; TG-DTA (Seiko Instruments TG/DTA 220), sample mass = ca. 5 mg, heating rate = 20 K min -1 , N 2 gas flow rate = 100 ml min -1 . Mass residue (MR) was indicated as [(m T – m 300 )/m 300 ] x 100, (%), where m T is mass at temperature T and m 300 is mass at 300 K. Mass residue was evaluated at 723 K. Figure 8-5 shows derivative thermal degradation (DTG) curves of PU composites from wood meal. As seen from Figure 8-5, DTG curves show the presence of two kinds of thermal degradation temperatures (T d ’s) corresponding to DT d1 and DT d2 . DT d2 seem to be specific to the degradation of wood meal, since the DT d2 peak becomes prominent when wood meal contents in PU composites are over 60 % and it is clear when wood meal content is 100 %. Figure 8-7 shows change of MR at 723 K with increasing wood meal content in PU composites, suggesting that wood meal obviously decomposes at 723 K. As mentioned above, the compression strength ( σ ), as well as the compression modulus (E), are almost constant in the region of plant powder content lower than 50 %. When the plant powder content exceeds 60 %, σ and E increase prominently with increasing plant powder content, reaching a maximum at plant particles/powder content = ca. 70 %, and then decrease with increasing plant powder content. The DTG curves of the prepared PU composites show two kinds of thermal degradation temperatures: DT d1 and DT d2 . The DT d1 decreases with increasing plant powder content. The DT d2 increased slightly with increasing plant powder content. Bio- and Geo-composites Containing Plant Materials 309 500 600 700 800 020406080100 Wood Meal Content / % D T d / K D T d2 D T d1 Figure 8-6. The change of DT d1 and DT d2 of wood meal-MP type PU composites with wood meal contents. ٨: DT d1 , ً: DT d2 0 10 20 30 40 50 0 20406080100 Wood Meal Content / % MR / % Figure 8-7. Change of mass residual amount (MR, %) at 723 K and wood meal content in PU composites. 2. BIOCOMPOSITES CONTAINING COFFEE GROUNDS Polyurethane (PU) composites that are prepared from ground plant particles, such as coffee grounds, mixed with a molasses-polyol (MP) solution consisting of molasses and polyethylene glycol (PEG 200) are described in this section. Mechanical and thermal properties of the above composites are also considered. 310 Chapter 8 2.1 Preparation PU composites containing coffee grounds (CG) as fillers can be prepared according to the scheme shown in Figure 8-8 [7,8]. CG are first mixed with polyol containing molasses or lignin. The suspensions with various mixing ratios from 10, 20, 30, 40, 50, 60, 70, 80 and 90 wt % of CG in molasses polyol (MLP) are prepared. Lignin-based polyol such as kraft lignin-based polyol (KLP) can also be used. Acetone may be added to each mixture in order to control the viscosity of the suspension. MDI is added to the suspension under stirring and PU composites are prepared. After drying at room temperature, the sample is cured at 393 K for 2 hrs. Coffee Grounds Molasses Polyol Suspension PU Composites reacted with MDI mixed added NCO/OH = 1.2 Filler Contents = 10 - 90 wt % Figure 8-8. Preparation scheme of polyurethane composites (PU composites) containing coffee grounds (CG) in molasses polyol (MLP) [7]. 2.2 Thermal and mechanical properties Figure 8-9 shows the change of density ( ρ ) of PU composites with CG contents. The density reaches a maximum when CG content in MLP is ca. 70 %. Figures 8-10 and 8-11 show the change of compression strength ( σ ) and modulus of elasticity (E) of PU composites with CG contents in MLP and KLP. As seen from the figure, compression strength ( σ ) and modulus of elasticity (E) increase with increasing CG contents in PU composites and reach a maximum when CG content is ca. 70 % in KLP type PU composites and ca. 80 % in MLP type PU composites. Bio- and Geo-composites Containing Plant Materials 311 0 0.2 0.4 0.6 0.8 1 1.2 0 20406080100 Coffee Grounds Content / % ȡ / g cm -3 Figure 8-9. Change of density ( ρ ) with coffee grounds (CG) content in polyols such as MLP and KLP. ٨: MLP type PU composites, ٤:KLP type PU composites 0 10 20 30 40 0 20 40 60 80 100 Coffee Grounds Content / % ı / MPa Figure 8-10. Change of compression strength ( σ ) with coffee grounds (CG) content in polyols such as MLP and KLP. ٨: MLP type PU composites, ٤:KLP type PU composites. 312 Chapter 8 0 200 400 600 800 0 20406080100 Coffee Grounds Content / % E / MPa Figure 8-11. Change of modulus of elasticity (E) of PU composites with coffee grounds content. ٨ MLP type PU composites ٤ KLP type PU composites. 0 10 20 30 0.4 0.6 0.8 1.0 ȡ / g cm -3 ı / MPa 0 200 400 600 800 E / MPa Figure 8-12. Change of compression strength ( σ ) and compression elasticity (E) of PU composites containing CG with apparent density ( ρ ). ٨: σ, ٤: E. Figure 8-12 shows the change of compression strength ( σ ) and compression elasticity (E) of PU composites with apparent density ( ρ ). As clearly seen from the figure, σ and E increase almost linearly with increasing ρ , showing the strong dependency of mechanical properties of the PU composites on ρ. Figure 8-13 shows TG and DTG curves of PU composites prepared from CG. As seen from Figures 8-14 and 8-15, TG and DTG curves show the presence of three kinds of thermal degradations corresponding to T d1, T d2 and Bio- and Geo-composites Containing Plant Materials 313 T d3, DT d1 , DT d2 and DT d3 . T d2 , T d3 , DT d2 and DT d3 seem to be specific to the degradation of CG, since those peaks are prominent when CG content is 100 %. Figure 8-13. TG-DTG heating curves and derivative curves of MLP type PU composites containing various amounts of coffee grounds. 500 600 700 800 0 20406080100 Coffee Grounds Content / % T d / K T d3 T d2 T d1 Figure 8-14. Change of T d with coffee grounds content in MLP type PU composites. Figure 8-16 shows the change of MR with CG contents in PU composites. The results show that CG parts in the composites degrade at 723 K, which is more easily than polyurethane parts of the composites, since thermal degradation proceeds more efficiently with increasing CG contents. 314 Chapter 8 500 600 700 800 0 20406080100 Coffee Grounds Content / % D T d / K D T d1 D T d3 D T d2 Figure 8-15. Change of DT d with coffee grounds content in MLP type PU composites. 0 10 20 30 40 50 0 20406080100 Coffee Grounds Contens / % MR / % Figure 8-16. Change of mass residue (MR) at 723 K with coffee grounds content in MLP type PU composites. 3. GEOCOMPOSITES In two major components of plant materials such as cellulose and lignin, lignin is a promising biomass, which is obtained as a by-product of pulp and paper industries and has not been effectively utilized until now. Lignin is usually considered as a polyphenolic material having an amorphous structure, which arises from an enzyme-initiated dehydrogenative polymerization of coniferyl, sinapyl and p-coumaryl alcohols [12-14]. Therefore, the basic lignin structure is classified into two components; the aromatic part and the C3 chain part having propane-unit structure. The only usable reaction site in lignin is the OH group, which is the case for both phenolic and alcoholic hydroxyl groups. Molasses is also obtained as a by- [...]... water is added and an excess amount of water was excluded from the sand using a corking hand gun In this stage, the mass of sand increases ca 16 %, (4) the surface of the sand is flattened, (5) a pre-determined amount of PEG 200, a small amount of foaming agent, foaming controlling agent and DBTDL are added to predetermined amount of KLP under stirring, (6) the mixture is stirred for 1 min and then MDI... surface of the sand and the mass of PU is negligible for ρ of composites When compression strength (σ) of KLPPU, LSPPU and MLPPU is plotted against content of lignin or molasses in PEG, σ increases slightly in the initial stage and then decreases linearly with increasing lignin and molasses contents as shown in Figure 8-24 The curves decrease in a similar manner in two series of KL and LS with TEG and. .. residue at 773 K was calculated and compared with that of 723K, the difference was almost negligible The major part of the residue is silicate sand, and the residual carbon which is obtained by thermal decomposition of polyurethane foams is less than 7 % in Chapter 8 320 the geocomposites The mass residue of KLTPU, LSTPU and MLTPU samples was smaller than that of KLPPU, LSPPU and MLPPU samples A C B 1.8... construction and packaging In this section, new types of PU geostabilizers derived from kraft lignin (KL), sodium lignosulfonate (LS) and molasses (ML) are described Preparation of geocomposites which are prepared by the reaction of PU-based geostabilizers in sand and the mechanical and thermal properties of the above geocomposites are considered in this section 3.1 Preparation Three kinds of polyol were... bottom (lmax) and the minimum length (lmim) are measured, as shown in Figure 8-17 Permeation length of prepolymer in the sand was defined as the average of lmax and lmim Figure 8-18 shows change of permeation distance of geocomposites as a function of KL, LS and ML contents in PEG and TEG solutions Permeation distance is defined as shown in equation 8.2 Measurement method is found in the caption of Figure... pieces of geocomposites of the KL series are prepared as follows [15,16]: (1) ca 0.270 kg of silicate sand (Japanese Industrial Standard, JIS No 4) was dried in an oven controlled at 300K for 30 minutes, (2) dried silicate sand is filled in a polypropylene (PP) cylinder with diameter 4.0 x 10- 2 m and length 2.1 x 10- 1 m equipped with a lid coated with fluorine type removing agent, (3) 100 ml of water... amount of solution is 0.030 kg, (7) before drastic foaming starts, the solution is quickly poured into the sand, (8) an injection syringe equipped with an oring is inserted in the PP cylinder and the content was compressed using a corking hand gun, (9) the sand containing prepolymers stands for 24 hours under compression at 300K, (10) solidified sand is taken from the cylinder and non-reacted sand was... change of permeation distance of LSTPU and LSPPU with LS contents in TEG and PEG solutions Figure 8-18 shows change of permeation distance of geocomposites with KL, LS and ML contents in PEG and TEG solutions Permeation distance of the above samples increases in initial stage by adding lignin As shown in Figure 8-18, water insoluble KL shows quite different behaviour compared with water soluble LS and. .. 1.2 0 10 20 30 KL Content in Polyol Solution / % 0 10 20 30 LS Content in Polyol Solution / % 0 10 20 30 ML Content in Polyol Solution / % Figure 8-23 Apparent density of geocomposites as a function of KL, LS and ML content in TEG and PEG solution : KLTPU, : KLPPU, G: LSTPU, : LSPPU, : MLTPU, : MLPPU Measurements; Sample pieces for mechanical tests with a diameter 4.0 x 10- 2 m and length 8.0 x 10- 2... reasonable, since the content of PU is small Figure 8-22 shows mass residue of KLTPU, KLPPU, LSTPU, LSPPU, MLTPU and MLPPU at 723 K as a function of lignin or molasses content in PEG The amount of mass residue (MR) ranges from 50 to 60 % in KLTPU, LSTPU and MLTPU, and no large difference is observed for the three series of samples The amount of MR ranges from 80 to 90 % in KLPPU, LSPPU and MLPPU Even when mass . lignosulfonate (LS) and molasses (ML) are described. Preparation of geocomposites which are prepared by the reaction of PU-based geostabilizers in sand and the mechanical and thermal properties of the above. 4.0 x 10 -2 m and length 2.1 x 10 -1 m equipped with a lid coated with fluorine type removing agent, (3) 100 ml of water is added and an excess amount of water was excluded from the sand using. calculated and compared with that of 723K, the difference was almost negligible. The major part of the residue is silicate sand, and the residual carbon which is obtained by thermal decomposition of