Agriculture Reference
In-Depth Information
c.
Degradation
Degradation is any undesirable change in a physical property or the ap-
pearance of the PPE material. Examples include swelling, shrinkage, loss of
puncture and tear resistance, and an increase in stiffness due to exposure to
pesticides. The degradation effects of a pesticide on PPE materials can be as-
sessed in the laboratory or in the field.
In a typical degradation test, a specimen from the PPE or, in some cases
(e.g., a glove), the entire item is immersed in the pesticide for some period of
time. At predetermined intervals, the specimen is removed, tested, and ob-
served. In the laboratory, strength, puncture, and tear properties are commonly
measured using a machine with which the specimen is stretched and the force
required to stretch the specimen recorded. Significant increases or decreases
(
20%) in any of the properties would be indicative of poor resistance to the
pesticide formulation. Losses in these properties would generally result from
the sorption of one or more components of the pesticide formulation by the
glove material.
±
Increases in properties are often associated with the extraction of compo-
nents from the glove material by the pesticide formulation. The stiffening of
polyvinyl chloride (P VC) gloves due to extraction of plasticizer is an example.
Care must be taken when testing clothing materials that derive their
physical properties from a supporting fabric but their barrier properties from
the coating. The supporting fabric may not be affected but the barrier coating
may be degraded by the chemical.
Sorption or extraction may also be evidenced by changes in the weight
and/or dimensions of the test specimen. Measurement of such effects are rela-
tively easy to perform in either the laboratory or the field. For this reason,
until recently most chemical resistance charts published by suppliers of po-
lymeric materials and polymer-based PPE were based on weight change or
swelling measurements. Again, weight or dimensional changes of
±
20% for
rubber materials or
3 % for plastic materials should be considered significant
and indicative of poor resistance to the pesticide formulation.
±
B.
ARM AND HAND PROTECTION
1.
Introduction
As discussed in previous section, there are scores of polymeric materials
from which gloves are fabricated. All of these materials are subject to
some degree of chemical attack by pesticide formulations. The degree to
which the pesticide formulation will attack any given polymeric material is
dependent on the duration of the exposure, the temperature, the condition of
the material, and the specific interactions between the polymer and the particu-
