Envirocare additives

Figure 2. FTIR spectra of samples after air-oven ageing without (lower trace) and with (upper trace) Envirocare additive.

Figure 3 shows failure data for samples of a transparent LLDPE mulch film formulated with Envirocare additives and exposed in a circulating air oven at 50°C. Failure was taken as the point of embrittlement of the film it can be varied by choosing the appropriate amount of additive and can be accelerated significantly and controllably. 

It is important to emphasize that the TDPA and Envirocare additive packages do not change the mechanism or products of the degradation of polymers. They simply accelerate the normal reactions, leading to the same final products in shorter times. 

Figure 5. Embrittlement times for 25 nm LLDPE transparent mulch film with six different Envirocare additives exposed outdoors in soil contact in Pontecchio Marconi, Italy (110 kLy yr ). Data are times (dark bars) and absorbed energy (light bars) for embrittlement.

Figure 6. Embrittlement and disappearance times for 25 pm transparent LLDPE mulch films with four Envirocare additives exposed in soil contact in Bologna, Italy (110 kLy yf ).

Mulch films containing Envirocare additives have been tested extensively in field trials in different countries and for different crops. Successful results have been obtained for instance, in the following applications ... 

Field trials of films with longer required lifetime are ongoing for crops like strawberries (6-10 months), pineapple (10 months), tomato (6 months) and watermelon (6 months). In addition to mulch films, other agricultural applications where the use of Envirocare additive is beneficial have been identified. Hence field trials are running in solarization films, small tunnel films, seeding bags and banana bags. 

Biodegradability of polyethylenes modified by TDPA and Envirocare additives has been assessed by a variety of laboratory-scale and field-scale composting tests. Most recently, an extensive commercial-scale composting trial of TOP A additives has been carried out in the municipal composting plant of Vienna Neustadt, Austria, directed by Dr. B. Raninger (Leoben University). 

The major benefit for the user of degradable films is convenience. After use, the plastic film or thicker part does not need to be recollected, transported to a collection center and disposed of by burial, landfill or incineration. A second important benefit is that TDPA and Envirocare additives can be used with commodity plastics, with standard processing equipment and, last but not least, with standard processing conditions without affecting the mechanical or the optical properties of the plastic. 

Ciba has also developed a silver-based additive called Irgaguard B, together with a number of other additives that impart selective biodegradability to polyolefin agricultural films, under the Envirocare name. 

Because of the complexity of degradation and stabilization, a basic understanding is necessary to develop the additive system appropriate for a given application and location. Many different Envirocare films have been evaluated in the Application Centre of Ciba SC in Bologna, Italy, where the variables that affect the film durability have been simulated. 

To model the complexity of real life conditions, films were laid on plastic boxes filled with soil, one part of the film being exposed to the light and another being covered by the soil. The boxes were exposed outdoors in Pontecchio Marconi (BO), Italy. This set-up simulates mulch film applications and allows the monitoring of the film degradation both on the surface and under the soil. The contribution of different parameters, like different additive systems based on Envirocare , different pigments and different film thickness has been evaluated. 

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