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PHA Properties

 

Properties of PHB:

PHAs can be incorporated into packaging components such as coatings, laminations and biodegradable printing inks. Additionally, PHA structures can include rigid thermoplastics, thermoplastic elastomers and grades useful in waxes, adhesives and binders. Properties range from elastomeric to resins as stiff as nylon 6 or polycarbonate.

(1) PHB is water insoluble and relatively resistant to hydrolytic degradation. This differentiates PHB from most other currently available biodegradable plastics, which are either water soluble or moisture sensitive.

(2) PHB shows good oxygen permeability.

(3) PHB has good ultra-violet resistance but has poor resistance to acids and bases.

(4) PHB is soluble in chloroform and other chlorinated hydrocarbons.

(5) PHB is biocompatible and hence is suitable for medical applications.

(6) PHB has melting point 1750C., and glass transition temperature 150C.

(7) PHB has tensile strength 40 MPa, which is close to that of polypropylene.

(8) PHB sinks in water while polypropylene floats. But sinking of PHB facilitates its anaerobic biodegradation in sediments.

(9) PHB is nontoxic.

(10) Biopol is stable when stored in air and is quite stable when stored even in humid conditions.

(11) PHA is hydrophobic and resists both water and oils, even when hot, so it can be used in applications up to 230 to 240 F. HDT is above 212 F, so it can coat hot-drink cups. PHA has a narrow molecular-weight distribution (which can be fine-tuned) and good printability.

(12) PHA is semicrystalline (up to 60%) with density of 1.20 to 1.25 g/cc, melting points of about 50 to 180 C, and Tg from -20 to +5 C. Melt temperatures are from 176 F to 320 F, not far from its thermal degradation temperature of 338 F. So extruder barrel temperatures are reversed, starting at 365 F and dropping to 329 F at the die.

(13) Molecular weights can be varied between 100,000 and 1,000,000, and elasticity from 5 percent to over 1000 percent at break.

Comparison of Properties of Polypropylene (PP) with PHB

Parameter Polypropylene (pp) PHB
       
1 Melting point Tm [0C] 171-186 171-182
2 Glass Transition Temperature Tg [0C] -15 5-10
3 Crystallinity [%] 65-70 65-80
4 Density [g cm-3] 0.905 – 0.94 1.23 – 1.25
5 Molecular weight Mw (x10-5) 2.2 – 7 1 – 8
6 Molecular weight distribution 5 – 12 2.2 – 3
7 Flexural modulus [GPa] 1.7 3.5 – 4
8 Tensile strength [MPa] 39 40
9 Extension to break [%] 400 6 – 8
10 UV resistance poor good
11 Solvent resistance good poor
12 Oxygen permeability [cm3m-2atm-1d-1] 1700 45
13 Biodegradability - good
14 US Annual production M. tonnes 1.8 not determined
15 Other due to low density floats in aquatic system due to more density goes to the sediment in aquatic system.

 

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