Smith G.T. Cutting Tool Technology: Industrial Handbook

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Figure 208. ‘Wetability’ related to a droplet’s spherical cap, plus an automatic (aqueous) coolant mixing device.

Cutting Fluids 413

1. Physical removal of all deposits: swarf; debris; oil and

food contamination in the uid-system – using say,

coolant extraction equipment (Fig. 209a and b),

2. Treatment of the uid-system with an appropriate

system-cleaner – normally added to either the old

cutting uid – prior to draining, or more eectively,

to clean water and pumped-around the system for

the specied time-period, as recommended by the

uid’s manufacturer,

3. Removal of: all guarding; swarf conveyors; etc.; as

necessary to allow eective cleaning of inaccessible

areas – if ‘maintenance window’ time-frames per

mit,

. Flush the uid-system – pumping around it with

clean water,

5. Rell the



uid-system with fresh emulsion at the

correct dilution.

NB O

nce the fresh cutting uid is in-situ, it should

be inspected and checked on a regular basis, as

this proactive activity will considerably prolong its

working-life.

Maintenance of the Fluid During Use

e following on-going maintenance procedures to

the cutting uid during use, will assist in prolonging

its overall eectiveness and life:

•

Checking of the dilution regularly using a refrac-

tometer (Fig. 206), to ensure that the dilution

remains relatively constant – within the recom-

ended range

•

Never wait until the uid level falls below the pump

before topping-up, while regular top-ups to the re-

ired level with fresh uid assists

n controlling

bacterial growth,

•

Restrict the amount of swarf build-up, as large vol-

umes of swarf can encourage both corrosion and

bacterial growth,

•

Do not allow the cutting-uid’s sump to be used as

a ‘dustbin’ for example: cigarette ends; uneaten food

remnants; paper cups; general rubbish; etc.,

22 ‘Dilution control’ – if the emulsion is:

under-diluted, never add water, but rather pour in a weaker

emulsion;

Over-diluted, do not add concentrate, but rather pour in a

strong emulsion.

–

•

Avoid excessive leakage of oil from the machine

(i.e. tramp-oil’), especially during maintenance

overhauls/procedures.

ore sophisticated condition monitoring is of course

possible and may be tting where the consequences of

uid failure are serious, such as in a large centralised

system. Some cutting uid manufacturers oer this as

a service. While at another extreme, one UK cutting

uid manufacturer, actually achieves

‘on-line condi-

tion monitoring’ of emulsion b

y continuous control

of a

n automotive company’s engine production line

from a distance of over 100 km away.



e monitoring

and operational procedure is typically as follows: on

the production line, as the cutting uid’s character

stics change – when being continuously monitored,

the uid manufacturer (i.e. from the ‘HQ’), can au-

omatically ‘dope’ the system by discharging from a

centralised and strategically positioned stillage, ap-

ropriate chemicals, or uids – as necessary. While at

this remote monitoring station (HQ), they watch and

monitor on-line for say, the dilution ratio to change

– and as the newly-discharged ‘doping’ takes eect in

real-time, thereby keeping the emulsion at its opti

um performance.

Cutting Fluid Testing

ese testing procedures are important to undertake,

as they dene the

urrent status of the cutting uid.

Many aqueous-based cutting uid tests can be un-

ertaken, with the following ones normally being the

most oen employed:

•

Testing for concentration levels (e.g. using a re-

fractometer

– Fig. 206) – this being an important

23 ‘Refractometer operation’ (Fig. 206):

Place a few drops of cutting uid on the instrument’s prism,

Close the lid over these droplets,

Hold the instrument up to the light and view through the

eyepiece.

NB In the eyepiece, the light and dark interface is visually-

apparent and a measurement is obtained against the engraved

optical graticule – which is calibrated in % readings. Some

types of refractometer’s can be simply read-o from the eye-

piece numerical value – as shown in Fig. 206, while other ver-

sions obtain the actual % reading when the ‘interface value’

reading is compared against a specic calibration chart – to

obtain the dilution level. Such refractometers can be utilised to

obtain dilutions for a range of aqueous-based cutting uids.

–

414 Chapter 8

Figure 209. Typical coolant extraction/reclamation units.

Cutting Fluids 415

preventative measurement for water-mixed cutting

uids. ere are a variety of techniques currently

available, but in all cases, the results should be

treated with a certain amount of caution. As previ

usly mentioned, Fig. 207 graphically depicts how a

range of methods of assessment can give quite ap-

reciably diering results. For semi-synthetic prod-

cts, the concentration measurement by means of

a refractometer is very popular, although they tend

to be more accurate and precise only when fresh

mixtures are assessed. e more the contamination

from the machine tool’s lubricating system, the less

accurate and precise will be the results. A refrac

ometer being

a p

ortable hand-held instrument can

be transported and used anywhere within the pro-

uction plant – as necessary. It is also important to

ensure that only adjustable refractometers are used,

as prior to taking a reading, they must be set to

zero,

•

Testing for pH level – this is a simple, yet important

test, which should be undertaken on water mixed

with cutting uids – this being a measure of the

pH value. e pH value, or to be more specic, the:

hydrogen ion concentration, is a measure of the

acidity, or alkalinity of a solution. Aqueous-based

cutting uids tend to be alkaline, with a typical pH

range of between 8 to 9.5 (i.e see Fig. 202b, for these

values on the pH scale). us, a change in the pH

value indicates a disturbance of the hydrogen ion

equilibrium. is ‘disturbance’ in turn, suggests a

deterioration in the uid’s properties, due to either

biological, or chemical action, or both, but more

specically, indicating that heavy contamination

has occurred. e simplest manner of obtaining

a measure of pH, is by using

‘pH indicator strips’

hich once dipped in the cutting uid, the strips

will now change colour. is colour change in

the ‘strip’ is then visually

ompared and matched

against a coloured and graduated scale, to obtain a

pH reading. More exact measurements can be ob

ained by means of an electronic equipment for a

pH measurement reading

. Yet another technique

used to determine the pH value, is by means of ‘ti-

24 ‘pH readings’ , are in accordance with many countries na-

tional Standards, such as that found in Germany, namely:

DIN51369.

tration’

, which is a quantitative analysis method

to determine alkalinity. In contrast to the pH value,

which can only can only give the degree of alkalin-

ty, the ‘titration method’ a

lso establishes the alka-

linity level, but it also determines the rate of change

of this alkalinity – helping to estimate the cause of

the alteration. So when a

rapid rise i

n alkalinity is

detected, this points towards the presence o

f a con-

taminant, c

onversely, a fall in the alkalinity level in-

dicates p

robable bacteria growth

– decreasing the

ectiveness of the additive,

•

Corrosion protection – its measurement is an im-

portant preventative operation when using water-

mixed cutting uids, in order to avoid unexpected

corrosion of ferrous workpieces – owing to insuf



cient, or ineective corrosion inhibitors in the

uid. With some products, even small variations in

concentration can adversely aect corrosion pro

tection

•

Product stability – any deviation in emulsion sta-

bility in use can be quickly determined using the

‘centrifuge testing method’. I

n this technique, the

centrifuged sample of emulsion is compared: under

specied conditions; with the current working

Standard, giving an indication of the cutting uid’s

anticipated stability,

25 ‘Titration’ , is a volumetric analytical determination in which

a reagent solution with a known content (i.e. a ‘standard solu-

tion’), is bled into the metalworking uid to be determined.

e rate of change in alkalinity allows inferences to be drawn

on the probable causes of this increased alkalinity.

26 ‘B

acteriological eects’ , if too high a degree of alkalinity pres-

ent in the aqueous-based cutting uid: which for example,

can be caused by adding excessive amounts of highly alkaline

bactericides, this being just one of the main causes of skin ir-

ritation, indicating the importance of regular checking of the

cutting uid’s alkalinity.

NB More will be said on this topic later in the chapter, in the

relevant section concerning setter/operator ‘health-issues’.

27 ‘C

orrosion protection’ , the degree of corrosion protection can

be simply measured to many national Standards, typical of

these are the German: DIN51360 and DIN51759 – known as

the ‘Steel strip method’.

NB ese corrosion development tests are most reliable, if

the local water and authentic chips taken are from the actual

machine tool used.

416 Chapter 8

•

Bacteria count – the most accurate, but an expen-

sive test method of determining the ‘bacteria lev-

ls’

present in a cutting uid is by actual count-

ing – for example, according to the German unit.

A much more simple technique of achieving good

estimates of bacteria levels is by utilising

‘dip-slides’.

Here, the slides are dipped into the cutting uid,

then the potential bacteria are incubated for a set

time period and, nally compared with sample pic

res – oering a good and reliable attribute quality

control test method.

8.9 Multi-Functional Fluids

Tramp-oils: hydraulic uid and slideway lubricants;

will inevitably become mixed into the cutting uids

during machining operations. Today, one technique

to minimise the deleterious eects of their unwanted

inclusion in the coolants, is via usage of the so-called:

‘multi-functional uids’. 

ese products will extend

coolant life, because they maintain their performance

even in the presence of tramp-oils.

e multi-functional uid concept means that to

prevent a reduction in overall coolant performance –

if tramp-oils leak into the machine’s sump,

all 

uids

utilised in support of the machining operation: hy-

28 ‘Bacteria levels’ , in a cutting uid like all living organisms,

need trace amounts of minerals in the ‘diet’ for optimal

growth. While sulphates promote the growth of sulphate-re-

ducing bacteria (i.e. more specically: desulphovibrio desul-

phurican). Such bacteria ‘split’ the oxygen o sulphate ions

and utilise it chemically, as their oxygen source. is process

‘liberates’ hydrogen sulphide, producing the smell which is

very similar to that of rotten eggs! Specically, in soluble-oil

coolants, the mineral content of hard water reduces the eec-

tive concentration of emulsiers in a working solution. us,

reduced emulsier concentration produces a coarse emulsion

having large oil droplets, in a similar fashion to simply mixing

oil with pure water. Bacteria are very much ‘size-specic’ , as a

result, they attack large oil droplets more readily in a coarse

emulsion, the opposite is true for smaller oil droplets in a tight

emulsion. So, the easier the attack, the more readily the bacte-

ria can extract nutrition and as a result, they grow. Moreover,

bacteria grow best at the interface of the water droplet and

the tramp-oil. Certain oils have elements that promote bacte-

rial attack, being exacerbated by organic materials, such as:

tobacco; fruit peelings; etc.; that nd their way into the ma-

chine’s sump.

draulic oils; slideway lubricants; greases; should con-

tain identical a

dditives to that of the coolant. By way

of a practical illustration of this concept, in an auto-

otive engine machining plant, all operations are per-

ormed by a multi-functional oil, having a viscosity of:

10 mm

–1

at 40°C. While all the hydraulic functions

of the transfer-line, use a higher viscosity multi-func-

ional oil, having the same additives. is identical ad-

itive usage, ensures that tramp-oils as the leak into

the metalworking uid, do not degenerate, nor desta-

ilise the product, thus ensuring a longer working life

at optimum performance.

8.10 Disposal of Cutting Fluids

Cutting uid disposal costs have been reported to be

as high as 22% of the total cutting uid-related cost.

With environmental laws in Europe and in particu-

ar Germany, these laws have driven up uid-disposal

costs to >$1 per litre. With any coolant today, once it

has reached the end of its productive and useful life,

whether it is a: soluble oil; preformed emulsion; solu

ion; pure oil; etc.; it cannot be simply and indiscrim-

nately poured down a drain, or disposed of at will.

Waste cutting uid normally contains toxic substances,

which were either present when it was new, or exist

via contamination during its use. Possible contami

ants include tramp-oils: lubrication and hydraulic

oils and greases from the machine tool and, occasion-

lly from nitrite adhering to the heat-treated hardened

workpieces that have been subjected to ‘hard-part ma-

chining’ – m

ore will be said on this machining strat-

egy in the following chapter. ese contaminants now

being present in the ‘old’ cutting uid, markedly-dif-

er from the original product. To emphasise the point

still further, if initially pure water – not a good choice

today! – was used as a cutting uid, it would absorb

so much contaminant that aer a signicant amount

of machining operations, it could not now simply

poured away.

So, any used cutting uid should be thought of as

toxic waste and must be disposed of in accordance

with the appropriate authority’s regulations. Normally

the local water authority governs such cutting uid

waste disposal by: reprocessing; incineration; or other

means; with its removal depending upon the cost and

the amount of toxic waste material present. Typical

toxic substances that should

not b

e present in cutting

Cutting Fluids 417

uid waste are: nitrate; chlorine compounds; poly-

chlorinated biphenyl (PCB); as reputable cutting uid

manufacturers try to avoid their use, although traces

have been found in certain formulations. In the past,

sodium nitrate was once popular as a corrosion inhibi

or, but nowadays, should not be utilised. While PCB

should not be present in any o

f today’s cutting uids,

but previously it was sometimes illegally-added to re-

rened used oils. While, chlorine compounds – used

as EP additives – are

no l

onger acceptable for cutting

uids, as are many previous used emulsion additives

In order to keep uid disposal costs as low

s possi-

le, it is advisable to collect and separately store dier-

nt types of ‘spent’ cutting uid, for future appropriate

disposal, or reprocessing. ere are various processes

for reprocessing, or disposal of used cutting uids

available, such as: chemical and thermal processes,

while

ultra-ltration i

s oen used today (i.e. see Fig.

210 for cutting uid ltration details). Whichever in-

ividual disposal, or reprocessing route that is chosen,

29 Water-based uid additives:

‘Sodium nitrate’*, was previously employed as a corrosion

inhibitor – due to its eectiveness and cheapness, but it

should not be used today, owing to the potential problems

with nitrosamine formation. Nitrosamine formation being

strongly carcinogenic (i.e. acting irrespective of the mode

of intake into the body) causing tumours, attacking primar-

ily the: liver; kidneys; or respiratory organs. Modern cutting

uids tend to use additives such as: amine borates; amine

carboxylates; carboxylic acids; amine phosphates; as well

as sulphonates, while other corrosion inhibitors have been

specically designed for non-ferrous metals, such as alloys

of; aluminiums, or brasses;

* Previously, sodium nitride can react with diethanolamine,

forming very weak carcinogen nitrosodiethanolamine.

‘Chloroparans’ , moving from ‘short-chain’ chlorparans

(i.e. C10-C13) – suspected in an advanced study in USA of

being a carcinogen, to that of ‘longer-chain’ chlorparans

(i.e. C14-C17), mainly used as an extreme pressure (EP) ad-

ditive;

‘Triazine biocides’*, reduction, or elimination of triazine

biocides, due to the possibility of skin sensitisation;

*New and safer biocides are now available to replace ‘Triazine-

types’ of biocides.

‘Endocrine hormone’ , elimination of the endocrine hor-

mone-disrupting chemicals.

NB Cutting uid manufacturers are attempting to replace oil-

based products with ‘greener- equivalents‘, such as: Vegetable

oil-based MWF’s., such as oils extracted from either: soybean;

rapeseed; canola; etc.

–

will depend on a variety of factors, including retrieval

costs and local regulations

8.11 Health and Safety

Factors – Concerning

Cutting Fluid Operation

and Usage

Introduction

e ‘traditional’ petroleum-based metal-working

uids (MWF’s), are complex formulated products that

include sophisticated mixtures of: oils; detergents;

lubricants; and other additives, that have the poten

ial to be toxic. Most uid manufacturers today, have

complex additive packages coupled to newly-revised

formulation strategies that are based upon renewable

resources to ensure that MWF’s have: longer sump-

life; are safer to both the setter/operator and the en

ironment; with the added benet of being

ess la-

our-intensive to use – than was previously the case.

Moreover, these more recent MWF products must re-

ist: tramp-oil contamination; biological and chemical

stresses: these latter factors could change their ‘chem-

stries’ to produce otherwise unhealthy environments

for the users and detract from their overall stability.

In the last few years in particular in many industri

lised countries, there has been increased pressure by

interested parties: unions; companies; legislation; to

look into the toxic eects cutting uids have on that of

worker’s health issues and more recently, their disposal

and its aect on the environment. Until relatively late,

30 An example of cutting uid disposal:In the UK: which is in

the top 5 users of water-based MWF’s in Western Europe; it

produces approximately 20,000 tonnes of product concentrate

per annum. erefore, at the most common working-con-

centration of 5% (i.e. 5 parts MWF to 95 parts water), this

would simply equate to 400,000 tonnes of waste cutting uid

per year – which must be adequately disposed of in an envi-

ronmentally-friendly manner! Although in reality, this actual

gure does not take account of uid: evaporation; nor drag-

out; during the overall machining processes. [Source: Kuwait

Petroleum International Lubricants]

418 Chapter 8

Figure 210. Air-borne contamination from cutting uids and a variety of sources, can normally be l-

tered-out – producing a safer user working environment. [Courtesy of Kitagawa Europe]

Cutting Fluids 419

the cause of worker’s decline in health was only indi-

rectly-related to the exposure to MWF’s. Now, with the

higher-than-expected reported incidence of: skin dis-

rders (i.e. see Fig. 211); respiratory illnesses; asthma;

bronchitis; stomach cancer; liver and kidney tumours

and disorders; etc.; together with any associated liti

ation, this has meant that such issues are taken very

seriously by all interested-parties. In fact, there is some

concern with the increasing usage of synthetic cutting

uids, in combination with the far higher cutting feeds

and speeds used today, which jointly increase the par

iculate count in the workshop atmosphere. Bacteria

tend to be more pronounced in newly-developed u-

ds, where it is exceedingly dicult to control growth

of both the microbes and bacteria, although it is pos-

ible to manage and control the coolant mist emanat-

ng from the machine tool

8.11.1 Cutting Fluid-Based

Health Issues

Skin Conditions

It is generally acknowledged that prolonged, or re-

peated contact with MWF’s can cause a variety of skin

complaints: dermatitis (not shown), folliculitis, skin

irritation; etc.; as illustrated in Fig. 211. us occupa

ional dermatoses is a general term used to describe

any skin abnormality, or aggravation induced by the

working environment. While dermatitis is a more spe

ic skin condition, causing at the early stages: skin



ammation/irritation; leading to eventual breakdown

and appearance of a skin cracking condition – when at

31 ‘Permissible exposure levels’ (PEL’s), in the USA and in par-

ticular the Occupational Safety and Health Administration

(OSHA) Standard, previously (i.e. prior to 1999) said that mist

control in the working environment had a maximum value of

0.5 mg m

–3

, however aer 1999, OSHA brought this PEL down

to a tenth of the previous gure, specically to: 0.05 mg m–3

over an 8-hour period – and it can be achieved at relatively

small additional plant cost. In November 2001 OSHA, released

a document that recommended in its ‘Best Practices Manual’

the ‘way-forward’ in achieving this PEL.

NB Today, many automotive companies in particular, operate

at PEL’s well below this value – but being much closer to the

lower threshold value, typically having a PEL of: ≤ 0.05 mg m

–3

over an 8-hour period.

an acute stage. More specically, occupational derma-

titis can be characterised still further, into:

•

Primary irritation – resulting from an immediate

skin contact with MWF’s, or shortly aerward,

•

Sensitisation – results from an allergic reaction

(i.e. an immune-system response) to a particular

uid/additive substance. Initial uid contact may

not in the rst instance cause skin irritation, but

could initiate an exposure sensitivity build-up over

time. us, once the skin has become sensitised

then even the slightest exposure to

his substance

results in a severe reaction, being not restricted to

the contact site on the body,

•

Photosensitisation – is virtually identical to that of

‘sensitisation’ , except that the presence of light is

necessary to activate the sensitiser.

Folliculitis (Fig. 211a) is a supercial irritation of the

hair follicles by oil, or foreign matter suspended in it,

plus secondary microbial sceptic infection. It normally

occurs on the backs of arms and forearms, when the

basic requirements of correct washing and skin hy

iene are neglected. Remedial medical treatment is

relatively straightforward, usually clearing up aer a

few days.

Eczematous-type rashes, are skin inammation

arising from continued contact with soluble oil emul

ions, specically on the hands and forearms. e con-

inual and daily combination of wetting and alkalinity,

allied to mineral oil contact exposure. Makes the skin

macerated and can develop small, eczematous erup

ions, or dry, red patches, which may itch, but tend to

be more unsightly, than serious, which with correct

medication, should clear up reasonably quickly. If, the

allergic reaction recurs, then this indicates continuing

sensitivity, meaning this particular worker may need

to be transferred to other duties – not involving con

act with aqueous-based cutting uids.

32 ‘Allergic reactions’ , most people can be allergic to virtually

anything, but only 1% of the population get allergic reactions

to MWF’s. Although many other factors can inuence the

acuteness of the allergic reaction, such as: racial characteristics

– light complexion (e.g. redheads and blondes – due to skin

pigmentation have higher sensitivity levels); age – younger

people tend to get dermatitis more readily than older workers;

workers general good health/diet – this can build-up a toler-

ance to allergic sensitivity; perspiration – can contribute to an

allergic reaction; plus many other contributory factors.

420 Chapter 8

Figure 211. Some typical, but extreme skin disorders – attributed to exposure to cutting uids. [Courtesy of Castrol Industrial].

Cutting Fluids 421

Many other skin conditions can occur and their

causes can emanate from a number of MWF sources

– going beyond the current scope and objectives of

this chapter. Although through the application of bar

ier and conditioning creams, together with clean and

suitable protective clothing, coupled to good washing

facilities, these factors will inevitably lessen the pos

ibility of allergic reactions and skin disorders.

Tumours and Cancerous Effects

However, less well known than the allergic and skin

condition previously mentioned, are the other more

serious debilitating health eects on the machine tool

personnel exposed to MWF’s. Industrial experience

suggests that continuous and long exposure to certain

mineral

ils can give rise to skin thickening, known as

keratosis, whereby ‘warty-elevations’ (i.e. see Fig. 211b)

can slowly develop over a period of some years. Hence,

these warts will either: remain as they are; disappear;

or in the worse case scenario, become malignant.

A considerable volume of research in both the

chemical and biological elds has been undertaken,

in particular, into the eects of mineral oils in cut

ing uids and their aect on worker’s health. Mineral

oils may contain carcinogens – chemical compounds

which are active in causing cancer, with currently, a

number of these compounds having been identied.

ey

ccur in the main, as polycyclic aromatic hydro-

carbons and, when present in modern rened mineral

oils exist in extremely small proportions – making their

‘positive’ chemical identication exceedingly dicult

to dene. Oil renement by acid treatment has now

been replaced by more modern rening techniques,

including solvent-rened treatment and hydrogenera

ion – greatly reducing the undesirable proportions

of aromatic compounds (i.e. these latter compounds

being potential carcinogens)

. Moreover, chemical

coolants were originally based on diethanolamine

and sodium nitrate, which for some time have been

suspected of forming ethanolnitrosamine – another

suspected carcinogen. In order to remove this pos

ible carcinogen, in

984, cutting uid manufacturers

removed the nitrates from their formulations. Finally,

33 ‘N-nitrosamines’ , and its chemical compounds are a signi-

cant danger to worker’s health and, the American Environ-

mental Protection Agency (EPA), stated in a report of their

ndings in 1974, that: ‘As a family of carcinogens, the nitrosa-

mines have no equal.’

if one considers permissible exposure levels (PEL’s)

from nitrosamine sources. en, it has been stated that

smoking t

wenty (untipped) cigarettes per day will de-

liver 0.8 micrograms o

f various nitrosamines which al-

most equates t

o eating a kilogram of fatty bacon per day

(i.e. 6 microgrames), thus, when undertaking these

seriously debilitating smoking/eating toxicity habits

over a signicant period of time, they would consider

bly increase the risk of cancer.

Cutting Fluid Mists

Mists resulting from machining operations and their

subsequent collection resulting from the application of

cutting uids, are usually given a low priority by most

manufacturers when compiling a list of potential capi

al items for the workshop. To press this point still fur-

her, many companies would much sooner purchase a

new machine tool, than install a special-purpose air

cleaner. In the automotive industries interest in the

level of air quality has some degree of importance,

while elsewhere in smaller production workshops it is

somewhat of a hit-or-miss aair. Given the potential

worker health risks involved today, with high-speed

machining (HSM) coupled to increased tooling cut

ing data and

igher-pressure coolant supplies (i.e.

see Fig. 195 – top), possibly the greatest threat posed

to a worker is from atomised mists (i.e. sub-

µm s

ize)

within the local atmosphere. Many companies that

incorporate mist collection ltering, will only remove

particles of >4

µm i

n size, leaving the critical sub-µm

particles still present in the atmosphere.

e earliest chemical interventions to reduce mist-

ng were high-molecular-weight polymer additives,

that act to stabilise MWF’s and thus suppress mist for-

ation. With conventional petroleum-based uids,

polyisobutylene has been the preferred anti-mist ad-

itive. While, for aqueous-based cutting uids, poly-

thylene oxide (PEO) has been utilised. Due to the

susceptibility of PEO’s to shear degradation, repeti-

ive additions of the PEO polymer are needed to main-

ain mist reduction. Today, a newer class of shear-

stable polymers has been developed to overcome the

shear degradation as indicated by PEO’s. ese latest

polymer products have been derived from complex:

2-acrylamido-2methlypropane sulphonic acid mono

ers, hence, providing longer-term performance in

continuously recirculating aqueous-based MWF sys-

ems.

So, very high concentration cutting uid mists will

over a short period of time cause: ‘smarting’ of the

eyes; irritation of exposed skin; result in slight irrita

422 Chapter 8