Tính
kháng mài mòn tốt là một trong những đặc tính nổi bật của vật liệu đàn hồi PU.
Tuy nhiên, đặc tính này bị ảnh hưởng đáng kể bởi tác động tích trữ nhiệt bề mặt,
quá trình này có sự khác biệt đáng kể trong trường hợp mài mòn khô và mài mòn ướt.
Tài liệu sau đây sẽ phân tích chi tiết về vấn đề này.
…
Resistance
to wear is usually considered a measure both of resistance to tear and
resistance to abrasion. It is generally recognized that most abrasion tests have
little practical importance in predicting service but are useful in grading
materials of similar hardness. Abrasive wear, acutely in the case of
polyurethanes, is considerably affected by heat build-up on the surface and the
degree of surface heating. This latter is related to the coefficient of
friction of the polyurethane, the relative speed between the two faces, the
applied load, and whether the abrading surfaces are dry or wet. The abrasion
resistance properties of polyurethane elastomers are good but not exceptional
when compared with other rubbers and plastics under dry abrasive conditions.
This is primarily due to their relatively high hysteresis, hence surface heat
build-up effects, which for an instant of time, over a localized or micro
region, drastically soften the polyurethane such that it tears away from the
abrading surface. In extreme cases the entire surface of the polyurethane melts
for a fraction of time and a small fragment of elastomer is torn off, rolled
into a bead which then sticks to the semi-melted polyurethane elastomer
surface. This gives rise to a special failure characteristic phenomenon of
polyurethanes, as such surfaces can be identified by a multitude of small
melted sticky beads adhering to their surface.
These
comments apply to abrasion of dry surfaces and must be modified when
considering abrasion under wet conditions. In these cases the water or other
fluid lubricates the surfaces and reduces the coefficient of friction. Further,
any heat generation that does occur is more easily dissipated. It is under
these conditions that the polyurethanes are outstanding, since then their
inherent abrasion resistance is not diminished by the adverse effect of heat
build-up.
…
Trích
đăng từ sách Polyurethane Elastomers, C. Hepburn, Elsevier Science Publisher,
1992, trang 373 – 375
(vtp-vlab-caosuviet)
