36
Fuels & Lubes International Quarter Three 2015
used to measure engine oil viscosity because engine
temperatures are higher, whereas KV40 is used for
industrial oils.
HTHS viscosity is measured to see how engine oils
will hold up in the engine environment. ASTM D4683,
“Standard Test Method for Measuring Viscosity of
New and Used Engine Oils at High Shear Rate and
High Temperature by Tapered Bearing Simulator
Viscometer at 150 C,” was developed because the
viscosities of engine oils under these conditions are
related to fuel efficiency. It is measured in centipoise
(cP) or millipascals times seconds (mPa•s).
THE RIGHT TEST MAKES A DIFFERENCE
As with any product, the right test makes all the
difference when determining how a VM will behave
in the real world. Daniella Baxter, who works in the
Technology Deployment group of Infineum, discussed
the company’s field trial for heavy-duty oils that
has been operating in the U.S. for several years. It
tests SAE 15W-40 and SAE 10W-30 engine oils with
VMs of different chemistries: two HSD stars with
different shear stability indices, an amorphous OCP
and a semi-crystalline OCP. In measuring viscosity
performance, all four VMs kept the engine oils in grade
when KV100 and HTHS 150 were measured. Infineum
also measured low-temperature pumpability, using
a mini-rotary viscometer (MRV), MRV TP-1, for both
fresh oil and 35,000-mile (56,327 kilometres) aged
oils. The semi-crystalline OCP at 35,000 miles failed
行车性能，她总结说。
低温性能配方
Chevron Oronite粘度改进剂技术小组负责人 Alex Boffa及联名
作者，高级研究科学家John Fang说，低温性能配方的关键是基础
油、VM、其他添加剂与倾点下降剂（PPD）的正确搭配。配方不对的
油品，不管VII是非晶的或固体的晶体形态，在低温台架测试或现场行
车试验中表现很差，他说。他还说，较高的结晶度可以使固体VII不那
么容易粘结，更易于生产。在油品中，VM聚合物经溶解稀释后的特性
与固态不同，他解释说。无论是固体的非晶还是结晶形态，重要的是
避免在低温下基础油或VM中有蜡析出而导致不希望出现的反应。例
如，经优化的OCP在固态下结晶度低，Fang说。但是，当溶解在油品
中时，高敏感性的流变试验显示可忽略的屈服应力，这表明在聚合物
链之间没有互动的网格。
Fang还介绍了经优化的OCP的开发与评估，这涉及到一系列的结
构性质研究来证明可靠的低温性能和增稠率、积碳和长期剪切耐用
性的优势。可靠的低温性能是重点。该性能可以通过MRV试验、倾点
和Scanning Brookfield来测试；对于不同PPD范围和基础油类型的
废油，则可以通过CEC L105来测试。经优化的OCP的另一个好处是
当发动机处于高温区间时积碳较少，这是因为增稠率高而减少了聚合
物的使用。
延长换油期的性能
至于长期的剪切稳定性，Fang将经优化的OCP与一种星形HSI聚合
物进行了比较。两者都经过延长的剪切周期，以期在ASTM D7109的
Kurt Orbahn试验中经过90个周期后达到同样的KV100。两者均通
过了测试，然后将周期数增加到720个周期，为90周期的八倍，此时经
优化的线性OCP只增加了5%，而HSI则出现了严重的变质。Fang指
John Fang
Daniella Baxter
