Last updated: 3 January
2001
Musing
With Sin
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Introduction
I must say it is fun having a website. One feels one is in touch with all our valued clients. We have tried to communicate relevant business and technical data in the form of our Technical Bulletins, Short Notes, TDS & MSDS sheets, but there are other tit-bit information which we would also like to share. I have thought of a Newsletter but this implies regularity and I am not in that mood to be committed. Hence the title “Musing with Sin” which implies that as and when thoughts come to my mind we will post these. Readers are of course welcomed to comment or submit their thoughts if they think such information are of interest to others.
[Jan 00] [Feb 00] [Mar 00] [Apr 00] [May 00] [Jun 00]
[Jul 00] [Aug 00] [Sept 00] [Oct 00] [Nov 00] [Dec 00]
[Musing With Sin – Year 2001, Item 76 Onwards]
January 00
1. Mastication
3.
ETRA
February 00
5. High P0 NR with ethylene diamine treatment
7. SP 40/ 50 or SBR 1009 to maintain Mooney Viscosity during remills and to prevent blisters
8. Sulphur Vulcanisation – Invented first by Goodyear or Hancock – WRONG!
9. Titanium Dioxide – Anatase or Rutile Type for White Applications
10. Ultramarine Blue: Natural or Synthetic
11. The Art & Science of Beer Brewing
12. Little Known New NR Latex Application
March 00
13. Hexa: Activator and Origin of Life
14. Oligomersation
15. Karaoke Singers
16. Disposable Polymeric Bikinis
April 00
19. Rubber Paper: TESLIN Sheet
20. PNR
22. Stereo Rubbers
May 00
24. A Reflection
25. Standard Natural Rubber (SNR)
26. Made-In-Malaysia Processing Aids
27. Made-In-Malaysia Mica “Koticite-1”
28. NR’s Future
June 00
29. Rubber Grade Sulphur: Mesh 321 or Mesh 200
30. Spider Grade or MC-Sulphur
31. Insoluble Sulphur or m-Sulphur
32. Powder or Granular Grade Precipitated Silica
33. Homogeniser & Compatilisers
34. Light Switchable Pain-Free Plasters
35. Failed R&D Can Yield Commercialisable Products
37. Beer & Nicotine Are Good For You
38. Company Growth and Transformation
August 00
41. PMMI
42. Rubber Mirrors
43. Pultrusion
47. Light Curable Polymers From Palm Oil
September & October 00
51. Non-Tyre Rubber Products Manufacturing
52. Tyres Manufacture & Retreading
53. Precured Tread or Cold Cure Retreading
54. MSDS
57. Q3 Review
59. Cell Nucleation
November 00
61. Hottest Chilli
62. PEN
63. Famous Sayings
64. Anti-Staining Antiozonants
65. SMG
66. Effect of Curatives, Fillers & Process Oil on Hardness
67. Synthetic Rubber (NBR) Plant in Malaysia
68. LOI Index
69. EVA or EVM
December 00
71. Latex Timber Clones (LTC’s)
73. PCHE
75. HNR
1. Mastication
Thomas Hancock invented mastication of natural rubber in 1820. Ever wondered how the word was chosen? “Mastic” was the name of a Mediterranean tree which yielded the soft gummy resin “mastic” – known to Hancock. Hence his choice of the word mastication accurately detailed how raw natural rubber was converted to a soft gum like material using his “pickle” machine.
2. “NatureWorks”
Dow Chemical and Cargill just announced they would spend RM1.14billion to launch a new plant in Nebraska to produce a biodegradable plastic, based on natural plant produce such as corn. This will be a new polymer: Polylactide, which Cargill Dow Polymers has branded as NatureWorks.
This brings back memories of those days when we could put cheap tapioca flour into translucent rubber band compounds – but today it costs more than natural rubber.
We should wait to see what NatureWorks costs when it hits the market in 2001. Perhaps then we have an option to convert rubber estates to either palm oil or tapioca.
3. ETRA
Sin RubtechTM has been a member of the European Tyres Recycling Association, ETRA, almost during its inception some 7 years ago. Today ETRA has members from over 40 countries including Malaysia from which Sin RubtechTM is the sole entry. USA and Europe have recognised the problems of scrap tyre disposal and regulations, legislations, etc such as Landfill Directive, The Directive on End of Life Vehicles and the Basel Convention Accords are about to be passed or at various stages of being passed. The onus is on the industry to define priorities to set, implement and monitor standard for each aspect of the tyres recycling chain. Town councils would love to ban dumping of scrap tyres at their dumpsites but without alternative solutions how are the tyre dealers to dispose of their scrap tyres? Perhaps we can adopt what Ohio State did in 1996. In cooperation with Ohio Department of Natural Resources, the Ohio Environmental Protection Agency and the Ohio Department of Development, they developed a Monofil to house some 10 million tyres in an old strip mine. The objective was to stockpile these and later mine these when demand for tyre crumbs increase.
The situation in Malaysia is growing more serious as regards to scrap tyres disposal. Someone, some organisation, a forum whatever it may be has to be started if we are to start to address the problem. Sin RubtechTM is already doing its bit. Since 1995, we estimate that we have recycled some 600,000 of scrap tyres from the Seberang Perai area.
4. Zinc Oxide Transparent
I have always been asked what zinc oxide to use for transparent/ translucent compounds but nobody asks why one grade is more transparent than the other. There are 3 main grades of zinc oxide used in the rubber industry. If we qualify these with their refractive indices we have our answers: -
|
|
Active
Ingredient |
R.I. |
|
Zinc Oxide
Transparent |
Basic Zinc Carbonate |
1.618 |
|
Zinc Oxide Red Seal |
Zinc Oxide (French Process) |
2.02 |
|
Zinc Oxide Active |
Precipitated Zinc Oxide |
2.02 |
|
NR |
Polyisoprene |
1.52 |
|
BR |
Polybutadiene |
1.51 |
|
SBR |
Styrene butadiene rubber |
1.53 |
|
Water |
|
1.33 |
Zinc carbonate gives a more transparent compound because its RI is nearer to rubber and Zinc Oxide Transparent is effective at 1-2 PHR only. The Zinc Oxide Active being a finer precipitated grade can give a translucent compound despite its higher RI simply because it can be used at 1.0-2.5 PHR as against the 4-5 PHR normal Zinc Oxide.
January 2000
5. High P0 NR with ethylene diamine treatment
Every rubber chemist appreciates that NR storage hardens and hence the introduction of CV rubber in 1965 using mainly either the mono-functional hydroxylamine neutral sulphate or the semicarbazide to retard the cross-linking activities of the carbonyl groups present in varying degree on the NR main chains.
The recent news-breaking story of ethylene diamine contamination of aviation fuels Down Under brings back some memories. There is a group, albeit minority, who believes that high Po NR is good for better dispersion and vulcanisate properties under certain formulation/ processing conditions. This can be met by extended maturation of wet coagula/ sheets or the addition of bifunctional hydrazine or p-phenylenediamine. Ethylene diamine can also be used to raise Po without the hassle of extended maturation time. It also has an economical advantage in its lower molecular weight and its lower boiling point of 117.3OC means that residual ethylene diamine can be flashed off during normal TSR processing/ drying. Furthermore ethylene diamine is also a chelating agent which can boost PRI values.
6. SMR 10 : Bark Free
TSR 10 & 20 grades are made from field coagula such as cuplumps and tree laces but may also include some USS to adjust Po and/or PR1. Whilst dirt is not a problem in today’s SMR 10&20 production, this test parameter does not guarantee bark free SMR 10&20. Some Malaysian Producers go the extra mile to ensure only clean fresh cuplumps and no tree laces are used in their SMR 10. SinRubtechTM is in a position to advise clients where such SMR 10’s can be sourced from Malaysia.
7. SP 40/50 or SBR 1009 to maintain Mooney Viscosity during remills and to prevent blisters.
Superior Processing NR grades such as a SP 40 or 50 and SBR 1009 are both partially cross-linked rubbers. Whilst both are exceptionally good for dimensional stability of extrusion profiles, SP 40/50 are recommended to boost Mooney Viscosity of remills but not SBR 1009 which has a ML1+4@100OC of only 51+5. Easy processing refined grades SP-40R and SP-40RD with ML1+4@100OC about 75 can be available from SinRubtechTM.
8. Sulphur Vulcanisation – Invented first by Goodyear or Hancock.– Wrong!
We all know the story about the Spanish invaders of Central America in the 16th Century and their fascination by the solid rubber balls made by the natives which can then bounced higher than any European pig’s bladder football. Now scientists from the Center for Materials Research in Archaeology and Ethnology at MIT-USA have found that the natives have used latex from “Castilla Elastica” to provide the polyisoprene and this they mixed with jungle vine saps which contained sulphur containing organic groups which on heating (to dry the mixture) are capable of cross-linking the polyisoprenes.
The Natives have actually obtained a vulcanised rubber ball in the 16th Century, well preceding Goodyear or Hancock’s patents in the 1840’s (Ref. Science, 1999, 284, 1988)
9. Titanium Dioxide – Anatase or Rutile Type for White Applications.
In the old days we are expected to make a choice: bluish white Anatase TiO2 for the whitest white white applications with some sacrifice in “chalking behaviour” after weathering or a creamy white Rutile TiO2 for coloured and white applications with better light and weathering resistance.
Today Rutile grades with their crystalline lattices modified by example, alumina and/ or silica coating, can also give a bluish white like the Anatase type. Then the higher whitening power of Rutile \grades are preferred, as 80 parts by weight of Rutile grade can replace 100 parts by weight of Anatase grade.
The higher whitening power of the Rutile grade can be explained by its higher Refractive Index and this more than compensates for its higher density on a volume cost basis.
|
|
Refractive Index |
Specific Gravity |
|
Anatase TiO2 |
2.50 |
3.9 |
|
Rutile TiO2 |
2.75 |
4.05 |
So, for techno-economic reasons, choose a bluish white-coated Rutile grade.
SinRubtechTM is able to offer polymer bound predispersed TiO2 based on Tioxide (Malaysia) Sdn. Bhd. TR-92, a coated Rutile grade.
10. Ultramarine Blue: Natural or Synthetic
I have always advocated the use of the natural mineral Lapis lazuli for better heat stability and colour fastness over organic blue pigments. Not too many of us know that ultramarines can also be synthesised e.g. By calcining a mixture of kaolin, sodium carbonate, charcoal and sulphur in the absence of air. Synthetic ultramarines are available in blue, pink and even violet colours. Advantages of synthetic ultramarines are that they are 100% amorphous as compared to some possible crystalline pips in the natural ultramarines. If suppliers give the chemical formula you may distinguish the difference:
|
Lapis lazuli |
Natural Form |
|
(Na,Ca)8Al6Si6O24(S,SO4) |
|
|
Synthetic Form |
|
|
Na8[SiAlO4]6(S2,S3)2 |
11. The Art & Science of Beer Brewing!
Yes, there is really a book tracing the art and science of beer brewing over its 8000 years history. Beer is like a Big Mac, it has a consistently high standard worldwide (I will vouch for this) and when taken in moderation is an important natural food component of the adult diet. What is moderation? In the 16th Century, the German Temperance Order permitted no more than 7 glasses a day – almost the same limit imposed on me by my dear wife Cathryn now. For more read “Beer: Tap into the art and science of brewing by Charles Bamforth, London, Plenum 1998, pp245. Last year, the Engineering and Physical Sciences Research Council (EPSRC-UK) gave a UK$690,000 R&D grant to Brewing Research International of Nutfield, Surrey to study the physics and chemical engineering of brewing and fermentation
Happy guzzling. The perfect pint is yet to come.
12. Little Known New NR Latex Application
SinRubtechTM was recently approached to prepare a pastel pink latex compound to match a given sample. Besides pH, TSC etc, we needed only to do one more extra test i.e. a ml of this final latex compound spread over a piece of writing paper must be able to dry rapidly with the aid of a hair-dryer and the dried transparent film can be easily peeled off without undue distortion.
Guess its use yet? Now I must emphasise that I personally have only hearsay experience in this field of application. Apparently tabletop dancers in USA are now very rubber savvy and insist on rubber protection for 2 vital spots in their upper torsos instead of the traditional stick-on-tinsels.
And to my marketing buddies. Yes, the Asian markets have yet to be exploited, so I hear. And what about tailor-made instant prophylactics from this special latex compound…..
Such a proposal was actually made by a Malaysian some years back but then it is another story.
February 2000
13. Hexa: Activator and Origin of Life.
The pulverised or crystalline white solid hexamethylenetetramine commonly known as Hexa is used as a vulcanisation activator, an integral part of the HRH system for rubber to metal bonding and a hardener for phenolic/ epoxy resins. Now we are informed by Scott Sandford, astrophysicist and co-leader of the astrochemistry laboratory at NASA’s Ames Research Centre USA, that Hexa may be one of over 100 identified molecular species floating in space. He showed that Hexa can be hydrolysed in acid to yield amino acids and reasoned that it could be a starting material for the origin of life itself. Next time you use Hexa, handle it with loving care. The pulverised form is preferred, as it does not give dispersion problem. Better still use a polymer bound predispersed form.
14. Oligomerisation
We of the “Beatles” era are more at home with terms like “polymerisation” leading to low molecular weight polymers, liquid polymers, high molecular weight polymers etc. Recently, oligomers and oligomerisation are becoming more in fashion to describe specific tailor-made low molecular weight polymers such as 1,2 vinyl polybutadienes used as processing aids and as co-agents for peroxide curing, low molecular weight ethylene oligomers intermediates for surfactants/ detergents and other oligomers of thiophenes, tetrathiafulvalenes, pyrroles, anilines and metal complexes.
15. Karaoke Singers
I am one of those who can only croak. This brings me to the singing Midshipman fish story. Andrew Bass, yes, that is his name, neurologist at Cornell University has found that an enzyme, aromatase, which converts testosterone into oestrogen in male Midshipman fish might be responsible for either turning them into “singers” who can attract a mate through their singing or “sneaker” males who don’t sing but just hone their way in anyway. The testes of these “sneaker” males are found to occupy 15% of their body weight compared to 1% of the “singers” – extrapolating to a “sneaker” man means a pair of gonads would be about 10kgs. However results still cannot conclude that having bigger gonads always result in higher levels of aromatase or vice versa. So fellas – do you sing or croak!
16. Disposable Polymeric Bikinis
Modern society (the so-called Alvin Toffler Throw-Away Society) is accustomed to disposable devices. My two boys do not know what handkerchiefs are – they only use paper tissue. I myself even went as far as using disposable underwear – on those more than 1-week overseas trips. Malaysia is of course famous for our disposable rubber gloves. There is also fame in our world’s first disposable device for non-evasive male circumcision – “TARA KLAMP”. Now Italy has come out with fashion designer Igam Ussaro’s polymeric bikini called Legami (Bind Me) made of LDPE, available in 8 colours in addition to a transparent version, free size, requires only 3 knots to dress and each bikini packed in a 100x100mm sachet. For photo illustration see Macplas Int. Nov. 1999 page 27.
17. Managing Competitiveness.
We have had our fair share of management gurus extolling us to vie to be leading & cutting edge global manufacturing companies, invest more in R&D especially information technology etc. A lot of talk but few touch on how this is to be achieved. Directors and managers need to be more action orientated. Increasing R&D budget is an obvious recommendation as Malaysian companies are woefully behind the world leading edge companies. But this only will not bring results. Some useful guidelines are:
1. Directors/ managers must implement suitable policies relevant to science and technology on R&D, staff recruitment, training and organisation.
2. Directors/ managers must – have a clear understanding of the threats & opportunities provided by science and technology as this will encourage innovations and in turn assist them to win support and sustained R&D budgets for their overall strategies.
3. Directors/ managers need to appreciate the intangible technological assets of their people and expertise on which many companies depend and be clear how to nurture and exploit their strength.
In short, what we (in Malaysia) have been blessed before, natural resources and accumulated capitals are not enough to face the 21st Century. We need action oriented science and technology knowledgeable Directors to guide us to the global peaks.
18. Automotive Windows
Traditional methods for sealing fixed windows involve use of extruded profile rubber seals at the OEM assembly plant and placing these around the glass window with or without the aid of adhesives/ sealants. As OEM automotive assembly plants become more automatic and cost conscious, suppliers are now coming out with ready to use window modules, eliminating the many operation steps and the storage and use of bulk chemicals like adhesives/ sealants. Some of these new window modules manufacturing techniques include:-
1. Extruded rubber is wrapped around the glass window.
2. PU or PVC directly injection moulded onto glass window.
3. Rubber directly extruded onto glass window.
4. Extruded seals are bonded to the window.
5. Use of adhesives/ sealants, WITHOUT rubber seal, around the glass window.
Method 2 window modules are finding increasing popularity in USA, Europe & Japan. Method 5 is very cost effective but vehicle window frame dimensional tolerances must be very tight as there is no rubber seal to hide imperfections.
March 2000
19. Rubber Paper: TESLIN Sheet
PPG Industries will add a second plant in Barbeaton OH USA to produce TESLIN sheet. TESLIN sheet is a polymer-silica synthetic printing material that prints like paper, yet is durable and waterproof like plastic. Rubber monies may just be around the corner.
20. PNR
This is not peptised natural rubber but ASTM abbreviation for Polynorbornene, a very high molecular weight rubber obtained by the Diels-Alder addition of ethylene to cyclopentadiene and the subsequent ring-opening polymerisation of the norbornene. Since PNR retains one double-bond, it can be sulphur crosslinked with our polymer bound predispersed sulphur and accelerators. OEPNR can even give very low hardness vulcanisates e.g. Shore A = 15 and are recommended as better than EPDM in paper feeding rollers for high-tech copying machines.
21. Recycled Virgin Polymer
Buyers often enquire about percentage retention of virgin properties of reclaimed materials such as our REGENTM-GRS from examination glove rejects. As far as I know, there are only 2 polymeric product wastes that on recycling can yield 100% retention of virgin raw materials, those from PMMA & Nylon 6. In UK, ICI reclaims used Perspex bath tubs by simply heating them to regenerate the monomers. DSM and Allied Signal are to be congratulated for opening the plant Evergreen Nylon Recycling in Augusta, GA, to recycle the annual USA 450,000 MT of nylon carpet waste landfilled each year back into the raw material caprolactam.
22. Stereo Rubbers
They do not make music. Stereo rubbers are just like rubber stamps – ink-resistant soft moulded rubber sheets for the automatic long run printing of logos etc on shampoo bottles, carrier bags etc and even in the printing of paperback books. In short, they are rubber printing plates. Some starting NR formulations can be found in The Natural Rubber Formulary and Property index (1984). Naturally, our PBPC’s can be used to advantage in this product application.
23. Greensmith’s Machine.
This is the simple jig developed by the late Dr. H.W. Greensmith in the mid-1960’s to measure relaxed modulus at 100% strain and used as an indicator of the cure characteristics of SMR. Curemeters and Rheometers were then still relatively new and too expensive to consider for SMR laboratory use. I have had the pleasure and privilege to have worked under Bill Greensmith at the RRIM during that period and it is a pleasant surprise to find my ex-colleagues Dr. Aris and Dr. Abu making reference to the Greensmith’s machine in Chapter 4 of the newly published book entitled “Blends of Natural Rubber” (1998) Chapman & Hall. ISBN 0412819406. The Greensmith machine is also affectionately known as the “Bongo Tester” in Malaysia.
April 2000
24. A Reflection.
Since our launching this column 01/01/00, we are encouraged by the number of hits and some of our articles have been reproduced in our PRIM Newsletter. We realise that our company name is misleading. We used to be a consultancy company, but our present core business is in the manufacture of polymer bound predispersed rubber chemicals, trading of rubber machineries & test equipment, synthetic rubbers, peptised NR and regenerated glove rejects. We still offer some consultancy service but on a selective basis only.
Information in our web-site are targeted for our valued clients and to promote our products and services. Reference technical bulletins etc not posted in our web-site are normally available only to established clients. Hence visitors to our web-site can appreciate and we apologise for our silence or delay in response to certain inquiries which are outside our company interests. For the visitor who wanted rubber-lead sheetings for use in manufacture of aprons for gonads protection of X-ray technicians, we have yet to locate a supplier. There isn’t any in Malaysia that we know off.
25. Standard Natural Rubber (SNR)
What is in a name? We have taken for granted the Standard Malaysian Rubber Scheme launched in 1965. SMR carries with it a Quality status and commands a premium over other SNR grades. The writer is amazed recently at the number of SNR’s similar to SMR or conforming to ISO2000. Readers, like me, would like to be updated on global technically specified natural rubbers, this information kindly provided by my dear friend Mrs. Prem Bartlett of Guthrie Symington Ltd. UK.
|
Abbreviation |
Country |
|
STR |
Thailand |
|
SIR |
Indonesia |
|
SMR |
Malaysia |
|
SVR |
Vietnam |
|
CSK |
Cambodia |
|
SSR |
Singapore |
|
SLR |
Sri Lanka |
|
NSR |
Nigeria |
|
CNR |
Cameroon |
|
CSR |
Cote d’Ivoire |
|
PNG |
Papua New Guinea |
|
GH |
Ghana |
|
LIB |
Liberia |
|
GABON |
Gabon |
|
ZAIRE |
Zaire |
There are other block NR producing countries which do not export such as India & P.R. China, hence their SNR abbreviations are not known. In the above list, some African countries have yet to formalise their SNR Schemes and hence their incomplete abbreviations. There is a move to try to consolidate all African NR schemes as Standard African Rubber: SAR, but we have to wait to see it happen.
26. Made-in-Malaysia Processing Aids.
I am pleased to note in SDTC first issue of XLink Vol. 1 No.1, Jan-March 2000 under Industry News, the feature article of Performance Additive Sdn. Bhd., a joint USA/ Germany company established in late 1999. We released this information on 1st Jan 2000 in our revised Technical Bulletin #4.
For more of SDTC (Director of Research Dr. Abdul Kadir) check out their website http://www.simenet.com/sdtc.
27. Made-in-Malaysia Mica “Koticite-1”
There is now a local manufacturer of mica from deposits in Perak. The writer remembered those days when we tried to promote local clays and whitings. It takes time but Malaysians should be made aware. Basic analytical data are available, but rubber chemists now realise that besides these, structure and their actual behaviour in compounds such as interfacial strength/ weaknesses, processability, etc must be generated before acceptance. For example mica, talc and even some clays have – platelet structures but in Talc, the structures are such that there is less electrostatic attraction between the platelet surfaces thus they can slide readily over each other and this property is favoured in talcum powders.
All mica, talc and clay belong to the silicates family with hydroxyl groups, although in much lower quantity than in silicas. All mica, talc and even clay and whiting filled formulations can be enhanced by selected silanes as described in our Short Notes #5. The mercapto and thiocyanato classes are very economical to use for these fillers at 0.5 to 1.0 parts only per hundred parts filler. See our TDS on silanes.
28. NR’s Future
For some 3 decades, we have had seminars, publications, debates etc. discussing the future of NR, in particular, the “inequitable” price of NR. We really do not need economists to tell us why. Malaysia has had some 70 years of NR R&D behind us. We know and the world knows that there is not going to be a new monomer or a new SR that can replace NR and with diminishing oil/ gas supply, NR will be the world’s future elastomeric backbone with sustained R&D efforts. We know there is a future in NR. Governments know that planting Hevea is a way to create a lot of jobs and can support most times comfortably 2 downstream industries: rubber products manufacture and wood-based industries. The price of NR is “equitable” to Malaysia in the period up to the 1960’s but not today. But in countries like Vietnam, Cambodia etc, today’s price of NR is still equitable to them. This is the crux of the problem. In the past 3 decades, the increase in Hevea planting has exceeded demand. We do not have to have economists to tell us why the NR prices are so low; when public reports disclose that there are over 1m MT NR surplus alone in 1999 excluding surpluses of SR’s. It is no wonder that INRA failed as stockpiling measures alone cannot cope with such physical over supplies.
There are two rainbows in the horizon. Firstly, the timely commercialisation of RRIM LTC will in future give the industry the option to decide to tap, not to tap, double-tap such LTC plantations/ forest reserves and we do not need huge physical stockpiles of NR. Secondly, the recent OPEC actions show us that it is better to control production than to control physical stockpiles.
Maybe in the future, as in any business, we can sell NR at a cost++ rather to be a subject of uncontrolled supply-demand situations.
It is a fact that Malaysian rubber products manufacturers have benefited from NR low prices. However some large companies with both plantations and rubber manufacture have seen their estate sectors chopping down Hevea for palm oil plantations. For the future of the NR industry, it is timely to encourage upstream & downstream integration together with wood-based industries for sustained well-being of all sectors.
May
2000
29. RUBBER
GRADE SULPHUR. MESH 325 OR MESH 200
Learning is a lifelong experience. This is particularly true with the study of sulphur. Of late, I have been preoccupied with the dispersability of proprietary grades of soluble or rhombic sulphur and the slow change of proprietary grades particle size over the years just struck me. In the old days, rubber grade sulphur is invariably Mesh 325 or finer. In their pure form, they tend to lump up on storage and difficult to disperse. Over the years suppliers have realised that contrary to expectations that the finer the particle size the easier to disperse, they found that a slightly coarser grade Mesh 100-200 is better. Since rhombic sulphur is soluble in rubber at normal dosages, the slightly larger particle size is not a problem if it can be properly dispersed during mixing.
Today most soluble sulphur powder grades are treated with < 10% oil or mineral fillers to reduce its dust hazard, to prevent lumping during storage and to enhance its ease of mixing. If so treated, even Mesh 325 grade is fine.
For best dispersion, use polymer bound predispersed sulphur.
30. Spider Grade or MC-Sulphur.
With coarser grade sulphur and oil-treated grades, do we still need a magnesium carbonate coated rhombic sulphur? Perhaps the supplier of MC-Sulphur got it right years ago when they opted for Mesh 100-200 rhombic sulphur to start with. Anyway NBR compounders still swear by MC-Sulphur for ease of mixing.
31. Insoluble Sulphur or m-Sulphur
Chemists are still undecided to call this insoluble sulphur an allotrope, enantiotrope or a neotrope. We all accept that soluble sulphur has an Atomic Weight of 32.06 and its Molecular Weight is 256.48 since it exists as an eight-member ring S8 at < 199OC. With respect to insoluble sulphur (or polymeric sulphur since m-Sulphur is considered to be a mixture of high molecular rings or chains), I was taken aback to learn that nobody knows what the Molecular Weight of m-Sulphur is at any one point of time since m-Sulphur is at a metastable form at < 160OC and it tends to revert to the more stable rhombic sulphur at room temperature.
Being a polymeric form, insoluble sulphur turns plastic at 80-90OC and hence it becomes very difficult to disperse during mixing – stubbornly refusing to break into discrete particles, but rather tending to form strands/ agglomerates, longer in the direction of mill sheeting out. Even oil treated insoluble sulphur 80-90% active can give problems especially in transparent/ translucent vulcanisates.
It takes a lot of ingenuity to come out with a good polymer bound predispersed insoluble sulphur grade. We know, we have gone through the learning curve.
32. Powder or Granular Grade Precipitated Silica.
The rubber industry has lived with certain shortcomings of rubber chemicals and fillers for a long time. All of us realise that precipitated silica whether powder or granular grade is difficult to mix. It is refreshing to find leading supplier Degussa – Hüls candidly disclosing that old technology precipitated silica granulates have typically poorer “dispersion capabilities” of below 80% as compared to their new improved grade Ultrasil 7000GR which is rated 97% dispersible and can save up to 60% normal mixing time.
Sin RubtechTM is also active in this R&D area and has a new processing aid H-31 for faster incorporation of silicas.
33. Homogeniser & Compatilisers
The rubber industry is more accustomed to use the term homogenisers to improve the homogeneity of blends of rubbers and at the same time speed up fillers incorporation. The plastic industry prefers to use the term compatilisers to improve the compatibility of blends of plastics or plastic/ elastomer. In more than 25 years of R&D work on rubber blends, researchers have still to rely on mainly traditional materials like CR, MG-49, CPE, CSPE etc as compatilisers.
Only recently attempts are being made to tailor-made grafted copolymers and terpolymers with entities separately miscible with 2 or more phases with different degrees of polarity. We look forward to the commercial availability of such compatilisers.
Meanwhile there is a felt need to re-define the two terms Homogenisers/ Compatilisers to better reflect their new functions in present day polymer science.
June 2000
34. Light Switchable Pain-Free Plasters
Having talked about oligomers and compatilisers, polymer chemists should read the interesting article “A change of tack” Chemistry in Britain Nov. 1999. A group of polymer chemists headed by Iain Webster in Smith & Nephew Group Research Centre York UK embarked on a R&D project in 1995 to come out with an adhesive dressing which can be peeled off without causing pain or damage. After many trials, they found that the copolymerisation of itaconic anhydride containing acrylic polymer with 2-hydroxy ethylmethacrylate yielded a copolymer with a pendant methacrylate functional group which can be initiated by light at room temperature with for example Ciba Specialities Irgacure 784 , a highly reactive photoinitiator, to cross-link by a free-radical mechanism the copolymer. A cross-linked compound loses tack as expected. This work won the 1998 Royal Society of Chemistry’s Industry Affairs Division Team Award and the first light switchable adhesive product is expected to hit the market in 2002.
35. Failed R&D Can Yield Commercialisable Products
Not all R&D efforts produce expected results. Researchers should always keep an open mind on observations and R&D results. Two examples illustrate. Dr. Spencer Silver of 3M did not know what to do with a new glue which only clung to an object for a short period of time. His colleague Art Fry had problems of paper marking slips in his music book falling out during choir practise and he suggested Spencer’s glue be tried as temporary adhesive book markers. Today, 3M’s “Post-It” notes are among the top five selling office products.
Compounders of polymers in the past have tried to cheapen polymers with as much filler like CaCO3 as they can, for example, in LLDPE films. However at a certain excessive dosage, CaCO3 will create pippy holes in the stretched film. This defect was exploited by an Austrian film SML Extrusion Technology to manufacture a breathable diaper using a breathable SML LLDPE film..
36. Hotter Than Chillipadi
For curry lovers and my friend Kewalin in Bangkok who orders Chilli Padi as a side dish, the work of Burlington Scientific Co. USA will be of interest. They have discovered a new compound, denatonium nonyl venylamide which is hundreds of times spicier than Chilli Padi. They have successfully used it as a rodent repellent in polymeric insulated wire coverings. Seems such a waste. All of us can do with a spicy mouth watering dish once a while – get a real hot kick.
37. Beer & Nicotine Are Good For You
I do not encourage my 2 boys to follow the old man’s indulgences. However latest medical researches have been an embarrassment to my medical friends. Firstly, it appears that beer contains more Vitamin B6 than wine and spirits and this is supposed to be good for the ticker. Secondly, nicotine can offer some protection against neurodegenerative diseases like Parkinson’s, Alzheimer’s and Tourete’s Syndrome (TS) such as uncontrollable shouting of obscenities. Moderation in everything we do, eat, drink, smoke, etc seems to be the best advice yet. Now, I appreciate my Main Bar cronies’ advice: “Sin, calm down, have a beer or have a cigi.” No, I do not have TS.
38. Company Growth and Transformation
For any growing company, direction and its philosophical approach are important. The progress of Dow Automotive and its integration with Essex Speciality Products has enabled it to achieve Tier 1.5 supplier status – emerging as a “technology specialist”, whose business efforts are concentrated around three guiding principles: invention, innovation transformation and value capture, and how these efforts fit into current and future automotive industry. Invention is the basic R&D or idea- the first step in the value chain leading to innovation. Innovation is applying the idea to a commercial application. Value capture is the process by which innovation is transformed into a commercially marketable product.
These 3 guiding business principles go beyond merely meeting the immediate needs of customers and what makes a leading edge company. Sin Rubtech in a much similar way, is guided by the same 3 principles.
39. Molecular Modelling
Molecular modelling is about understanding chemical structure – function and structure– property relationships. It has been around since the 1960’s but with increasing availability of powerful PC softwares molecular modelling can speed up R&D work, enhance creativity of researchers, encourage teamwork and suggest new ways at finding solutions. Polymer scientists should not be left behind. It can be used in the search for new tailor-made polymers, copolymers, terpolymers etc or oligomers as primers, adhesives or compatilisers. An example would be in the R&D work on light switchable pain-free plasters (34). Molecular modelling is already extensively exploited in adhesives R&D. An example will illustrate how exciting in adhesives such work can be. In epoxy resins, choosing which hardness and catalyst to use, in one or two part systems, and controlling crosslink density to give the right properties are all important. Molecular modelling can be used to understand catalyst and hardness activity and to obtain parameters for models to predict crosslinking activities. One can firstly look at atomic effects to make sure reactive sites are available. Most modelling softwares e.g. CACHE allows you to sketch the model freehand, tidy up the structure and find molecular confirmation automatically. Visualising the 3D structure shows whether another molecule can reach the reactive site. If it can, reaction rate will be fast.
If the steric models are promising, one can even look at the electron distribution and its effect on reactivity. In epoxies, primary amines catalysts act as electrophiles attacking the electron-rich lone pairs of the epoxy ring oxygen atom while tertiary amines act as nucleophiles attacking the CH2 groups. Calculating electrophilic and nucleophilic susceptibility can be done by the PC and we can predict how the epoxy rings will be attacked and which new products will be formed. Even more useful is the prediction of the reaction path including transition states. All these can allow one to suggest formulations and reaction condition (time + temperature) end-users want, cutting down considerably laboratory experiments. I hope this has stimulated your interests.
July 2000
