Terrytraveller Posted October 23, 2006 Share Posted October 23, 2006 I am pleased to report that the fight between above contenders resulted in a clear win for the Polycarbonate lenses. Contrary to popular rumour, the adhesive used to stick the beam deflectors (or obscurers) to the plastic lenses, did not over three years of being permanently fixed - craze or damage the lense surface. However - although the deflectors were easy enough to peel off of the lense surface after 34 months, the remaining deposit of sticky goo was not. The only way to remove the deflector remnants left on the lense surface, was to use a hair dryer (on low) to warm the lense and scrape the goo off with a plastic credit card, finally using Isopropanal BP (available from chemists) to remove the softer gluey deposits and to polish the lense. I have used Isopropanal BP as a cleaner on Polycarbonates and variants of Polycarbonate for around 45 years as a service engineer, its the only chemical cleaner that I have found when used in moderation, will not soften or characteristically alter or migrate the chemical make up of plastics. One houshold product that can seriously damage plastic is the spray type furnisher polishes, it has caused very serious crazing on bathroom plastics including Polycarbonates when used frequently over a 10 - 12 month period of time. A good bathroom cleaner is the original Dettol product as it does/did contain a small amount of isopropal alcohol. Regards to all - Terry Link to comment Share on other sites More sharing options...
Brambles Posted October 25, 2006 Share Posted October 25, 2006 Hi, I agree the adhesive will not affect the polycarbonate, but not so sure about the heat build up. All I know is one summer driving around Europe with beam deflectors and my head light lenses crazed round the edge of the deflectors. It was a very hot summer and did sometimes drive into rain, so maybe the cooling effect of the rain on the hot lense caused the cracking. Whatever, they crazed. Jury still out maybe!! Jon. Link to comment Share on other sites More sharing options...
Terrytraveller Posted October 26, 2006 Author Share Posted October 26, 2006 Hi Jon, From previous experience, I would first look at any polishes youv'e used on the bodywork of the vehicle. often as not you use the same polish on the lenses and this may have a detrimental effect on them, you probably don't use vehicle polish on your plastic windows, the same rule should apply to the PC lenses. I had case where every friday aftenoon, the machine operators would clean and polish their machines with a spray polish (they smelt lovely!), the Polycarbonate covers were also cleaned to a sparkling finish, after 12 months they crazed and I had to replace all the Polycarbonate covers at some £7200 cost to the customer. Regarding the effect of heating and quenching on the PC lenses, its something to consider, but I think that those effects are taken into consideration during the general remit for any lenses. Regards Terry Link to comment Share on other sites More sharing options...
Brambles Posted October 26, 2006 Share Posted October 26, 2006 Hi Terry, The vehicle was in its first summer having been bought 3 weeks earlier before the crazing happened. I had never polished the lenses. Regarding heat and polycarbonate, it is a characteristic of polycarbonate the stresses occuring from different heat zones through the material will cause micro cracking. I worked for a company whose core competance for over 30 years was plastic moulding and manufacture of parts using various plastic materials and polymers. Trust me, uneven heat can cause micro crazing and blooming of polycarbonate, along with various solvents as you say. I just wish I had thought about it more before sticking on deflectors, but I did not think the heat build up would be too much of a problem, after all they are design by professionals and probems are well known in the headlamp industry. The problem with the ducato headlights is the beam pattern is very concentrated at some points on the headlamp and hence the heat. Under normal circumstances this is not a problem, but when driving in very hot sunshine, in a country which requires headlights to be switched on the temp will soar, hit some rain and treendous stress will occur, which obviously happened to mine. Is it worth taking the risk, well maybe, if only driving under most and non extreme conditions, but as risk of stone damage is also very high then why not just invest in headlamp protectors. Another fault I have is both headlamp adjustment motor units failing. This has been caused by failure of the variable resistor component for sensing position. The component used as far as I have traced, is substandard for the job, being rated at 0 to + 70 deg C and not automotive requirements of -40 to + 120 or even greater at extended specs of +140. According to the spec sheet from the component manufactire the component is excusively designed for use in toy game controllers!!!! So now knowing this, can I trust the headlamp manufactire has paid due diligence in specifying the material for the lenses. I have also heard from local fiat dealer manager that crazing does sometimes occur but fiat does not cover under warranty as it is accepted that it can happen and the headlights operation is not affected by it and is mainly cosmetic. So, to answer your comments on remit for lenses, it would seem they do take it into account, know it happens. Its all a trade of between other advantages of using plastic v glass. Better impact resistance, styling possibilities, cost of manufacture etc. Please don't take my scribblings as an attack on your comments, just putting my case forward in the debate ! Cheers, Jon. Link to comment Share on other sites More sharing options...
Terrytraveller Posted October 26, 2006 Author Share Posted October 26, 2006 Hi Jon, No umbridge taken on your comments - you say the crazing occurred around the edge of the deflectors, I had a close look at my lenses again and no such effect was found I am pleased to say. I wonder whether some sort of contamination was trapped around the deflector edge together with the adhesive and was working on the lense surface, around the deflector edge. I must admit I am very frugal with my headlamps and tend to turn them off whenever I think it is safe to do so, sending the power to the batteries for evening TV! Just recently France had an experiment going regarding day headlamps, that set me thinking of how I might switch the outer (dipped) headlamps in series, reducing the power consumption and heat onto the lenses. Have you any thoughts on this? Regards Terry Link to comment Share on other sites More sharing options...
Brambles Posted October 26, 2006 Share Posted October 26, 2006 Hi Terry, I can't see it being any solvent trapped - vehicle was supplied clean to me from dealer brand new, I drove down to dover, wiped lense with duster and put deflectors on. re your dipped lights idea, it used to be known as dim dip lights and they came on with sidelights, but you do not see many cars with it now. Not sure of regulations, as they changed and sidelights are not allowed for driving, if you need lights then you must put headlights on. As far as daytime normal driving I am not sure of regulations saying you cannot do it. How is it done? Basically when switching on side lights, relays operate to switch the two lights in series. Rather than sit down and work out how to do it from scratch, I will look up some cct diagrams for and old ford cortina - they used the system and get back to you if I find anything or manage to work it out. It should be really (pun intended) simple. Regards Jon. Link to comment Share on other sites More sharing options...
Chanel5 Posted October 27, 2006 Share Posted October 27, 2006 IsopropanOL is an alcohol and isoprpanAL is an aldehyde. T.T. you did mean the -ol, the -al is a foul smelling liquid which will choke and bring lots of tears to your eyes! We used alot of IPA (the -ol) in my industrial days and I used to teach it later in my working life. Link to comment Share on other sites More sharing options...
Brambles Posted October 27, 2006 Share Posted October 27, 2006 Oh gosh, forgotten to look at relay thing for lights - been rather busy. got email of new post and it reminded me. Jon. Link to comment Share on other sites More sharing options...
Terrytraveller Posted October 27, 2006 Author Share Posted October 27, 2006 Hi David, Seems I made a typo - yes you are right it is Isopropanol BP (propan-2-ol), thanks for correcting me, the one I use/used is marketed by Hillcross. Regards Terry Link to comment Share on other sites More sharing options...
Basil Posted October 27, 2006 Share Posted October 27, 2006 Not sure about the rights and wrongs on this regarding the adhesive with headlights (I have obviously read other peoples posts), but it is well known and documented that motorcycle crash helmets were weakened and crazed by people sticking adhesive backed stickers to them. Bas Link to comment Share on other sites More sharing options...
tonyishuk Posted October 27, 2006 Share Posted October 27, 2006 Are the lenses you writing about the headlight lenses or the headlght lens protector lens. ( Ones brought from maufacturers to act stone shields or where to put the black sticky tape so as to stop LHD dip on the continent) Do the additional protector lens make the matter better or worse ? Link to comment Share on other sites More sharing options...
Brambles Posted October 27, 2006 Share Posted October 27, 2006 Hi, the headlamp lense itself. Link to comment Share on other sites More sharing options...
Terrytraveller Posted October 28, 2006 Author Share Posted October 28, 2006 Hi Basil, I do wonder if the beam deflectors I used for those 34 months without removing, just to see if the lenses would craze, use especially formulated adhesive for use on PC lenses. The deflectors (obscures) I used were the silvered ones available from Halfords. I did phone the maker up regarding positioning of the deflectors as the post 2001 Peugeot lenses were not covered in the instruction sheet supplied with the deflectors at that time, although Fiat lenses where covered. Apparently - when a new vehicle comes onto the market, he hires or borrows one to design and test a newly designed defelector, using a normal beam alignment test rig (as seen in MOT stations), before going into production and writing advice about fitment. I wonder with all the comments about overheating the lenses, whether or not the lense protectors are a good idea, would they not prevent cooling of the lenses and possibly add to the problem of overheating? Regards Terry Link to comment Share on other sites More sharing options...
Brambles Posted October 28, 2006 Share Posted October 28, 2006 The problem with heat with polycarbonate is not the overall temperature but variations in temp through the material causing stress. If the lense has gradual temp gradients there will not be a problem, but a sudden gradient will induce high stress. Imagine the lense is all very hot, and deflector is attached. Spray of rain or road water will cool the uncovered part very quickly and the stress will be high. Bet the designer of deflectors you talked to has not taken that into account. Or maybe he accepts that there is aproblem but profits from deflectors allows for claims!!!!! The add on stone protectors will absorb some heat but will be less than on the headlight lense and as air can move behind the cover will be cooler, but yes the headlight lense will overall reach a higher temperature, but also bear in mind rain or road spray wil not land directly on theheadlight lense. Jon. Link to comment Share on other sites More sharing options...
Basil Posted October 28, 2006 Share Posted October 28, 2006 Hi Terry, I use protectors myself but then I have glass lenses anyway, however they are spaced off the lenses so I dont think that any overheating would occur as there will be airflow between. My only knowledge is with motorcycle crash helmets and that is only as a user. Being the owner of several different types of crash helmet, at least one completely polycarb so I am aware of the supposed effect on them. In fact reading the instruction/ guarantee sheet that came with that one, it expressly warns against the use of sticky backed plastic, solvents and paints of any kind on the product, no mention of only under heated conditions. I don't suggest for one minute that this principle could be transferred to headlights as I just don't know from a technical standpoint, as I have never stuck anything on a crash helmet for that matter I don't know if the warnings on them are valid either but safety stops me from wanting to find out!!. This does though tell me that certainly some form of Polycarb and adhesive/ solvents dont't go together so I would be reluctant to test it myself. :-S :-S Bas Link to comment Share on other sites More sharing options...
David Dwight Posted October 28, 2006 Share Posted October 28, 2006 Re Crash helmets, We were told way back in the early sixties not to stick things on to our Crach helmet, as this would weaken them. David Link to comment Share on other sites More sharing options...
Mel B Posted October 28, 2006 Share Posted October 28, 2006 Slight aside - anyone thinking of buying a second hand crash helmet - don't!!! You can't tell how they've been treated and if they've been dropped etc, not all damage is obvious - NEVER by a second hand one. Lesson endeth! :-> Link to comment Share on other sites More sharing options...
Chanel5 Posted December 10, 2006 Share Posted December 10, 2006 Just adding to the old 'adhesive residue on polycarbonate' thread. In the Daily Telegraph, Honest John section of December 9th 2006, someone has noted that they clean their polycarbonate lenses from sticky adhesive using WD40. They add that it doesn't mark or dissolve the plastic surface. David Link to comment Share on other sites More sharing options...
michele Posted December 10, 2006 Share Posted December 10, 2006 When in Hospital for the little ones operation .After the op she had sticky adhesive all over her body . i was given an oil based little squirty spray . fantastic stuff just a little squirt brings off all the glue if used on a person with no ill effects can't see that it would damage lights . have just been trying to find it all to give you the name but as usual when looking you never find. :-> May only be a hospital product though? Link to comment Share on other sites More sharing options...
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