FIGURE 5.9 Mechanical properties of PVA-based composite laminates.

FIGURE 5.9 Mechanical properties of PVA-based composite laminates.

Young's modulus (57 MPa). PVA/SCB also resulted in a harder film with a reduced EB (7%) than PVA/OR and PVA/AP composites, but with a relatively high UTS (8 MPa) and Young's modulus (171 MPa). This behavior is related to the fibers' composition and type. Both AP and SCB have a fibrous shape that confers hardness to the composites when processing allows for orientation as in the Brabender device, while in casting films, the random distribution of the fibers was a source of fragility.

Composites containing urea presented a higher EB, as expected, because of the increased percentage of plasticizer additives. PStORU presented a high EB (148%), and a decreased UTS (1 MPa) and Young's modulus (2 MPa) in comparison with PStOR.

A 500-mg composite sample containing PVA, OR, starch and glycerol (PORSt), and the corresponding amounts of PVA (165 mg) and fillers composed by OR, starch, and glycerol (ORSt) (335 mg) were dried up to constant weight and ground. The resulting powders were mixed with 25 g of compost soil in the sample chamber of a closed-circuit Micro-Oximax respirometer system. Sample chambers were placed in the water bath thermostated at 25°C and connected to the Micro-Oxymax respirometer. The total CO2 evolution was recorded every 6 h. Experiments were carried out over a period of 21 days. In this test, the large CO2 production from the compost soil did not allow us to separate that produced by PVA; the limited amount of PVA used also was a factor. The CO2 productions for one replicate of soil, PVA, PORSt, and ORSt are shown in Figure 5.10.

PVA and soil production are almost exactly overlapping, thus suggesting a very low mineralization of PVA. PVA resistance to degradation under soil burial conditions will be discussed in greater detail in the following sections of this chapter. In

0 "" : i I---1--1-\-1-\-1--i----' - ""

Was this article helpful?

0 0
Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook

Post a comment