Chemistry Reference
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intensity of methyl group of HV (0.89 ppm) and total integral intensity the
same group and HB group (1.27 ppm). This value is 21 mol%.
5.2.3 MOLECULAR WEIGHT DETERMINATION
The viscosity-averaged molecular weight (MW) was determined by the
viscosity (h) measurement in chloroform solution at 30 °C. The calcula-
tions of MW have been made in accordance with Mark-Houwink equation
[17]:
[h] = 7.7
∙
10
-5
∙М
0.82
5.2.4 FILM PREPARATIONS OF PHAS, PLA AND THEIR
BLENDS
The films of parent polymers (PHB, PHBV and PLA) and their blends
with the thickness about 40μm were cast on a fat-free glass surface. We
obtained the set of films with different MW = 169±9 (defined as PHB
170), 349±12 (defined as PHB 350), 510±15 kDa (defined as PHB 500)
and 950±25 kDa (defined as PHB 1000) as well as the copolymer PHBV
with MW=1056±27 kDa (defined as PHBV). Additionally we prepared the
set of films on the base of PLA with same thickness 40 μm and MW=67
(defined as PLA 70), MW=150 and 400kDa. Along with them we obtained
the blend PHB/PLA with weight ratio 1:1 and MW = 950 kDa for PHB,
and MW = 67 kDa for PLA (defined as PHB+PLA blend). Both com-
ponents mixed and dissolved in common solvent, chloroform and then
cast conventionally on the glass plate. All films were thoroughly vacuum-
processed for removing of solvent at 40 °C.
5.2.5 HYDROLYTIC DEGRADATION IN VITRO EXPERIMENTS
Measurement of hydrolytic destruction of the PHB, PLA, PHBV films
and the PHB-PLA composite was performed as follows. The films were
incubated in 15 mL 25 mM phosphate buffer, pH 7.4, at 37 °C or 70°С
in a ES 1/80 thermostat (SPU, Russia) for 91 days; pH was controlled
