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Due to a fractured metatarsal resulting from my bike stepping on my foot I'm in the market for a new pair of boots that offer the very best protection money can buy. Before I get any further this is not another model A vs. B post. This topic is about thermo-plastic polyurethane(TPU). 

I've recently learned that TPU is formulated in two base types: polyester and polyether. This is important because each have some very distinct physical properties, each present distinct advantages and or disadvantages.  The problem is most manufacturers don't stipulate which they use and distribution reps are unlikely to know. I started researching this when I discovered a forum members post of his boots with "...less than 100 hours". Both boots were cracked clean through to the liner base in critical areas. The damage was so severe and extensive as to render them completely useless. This is cause for concern for obvious reasons but the forum member didn't or couldn't get any help or information when he contacted the manufacturer's rep about the problem. Manufacturers experiment, mix, match, and are subject to quality control issues that compound the problem. We've all experienced an outstanding product that lasted for years only to be utterly disappointed with the exact make and model years later. "They don't make 'me like they used to."

I believe polyether TPU has better rebound-like  and direct impact resistance than polyester TPU, polyester TPU is more abrasion resistant. Both retain pliability in extreme cold, one is more restart to heat, but of particular relevance here is that polyether TPU is reported to be significantly resistant to certain chemical solvents. If Or rather when gas sloshes on my boots I'm unlikely to rush them to the ER for detox before riding but if I knew they fall apart if I didn't wash it off with mild soap and water immediately...,

There are countless cleaning products we use everyday. We all have our favorites but the base ingredients in them may cause more harm them good. I'd like to ask that guy about what if any products he may have used but don't want to wade through thousands of boot reviews to find him. His boots may have even been damaged inadvertently by environmental contaminants where they were stored. I had a pair of new leather boots that were destroyed from automotive paint vapors in the garage they where they were stored.  If you know him or can add a link to the post that would be helpful. I only recall the extent of the damage and that they were orange and white boots. 

I won't mention the brand because it's just not helpful. Manufacturers want a good product and happy customers. There exists a temptation to cut costs for any business but rare occurrences are at the expense of safety, quality, and customer satisfaction. Berating any single make over another due to isolated problems doesn't help the industry. We all benefit from good equipment and advanced technology. Competition amongst the manufactures is healthy and important to deliver us the best goods.

Id love to hear from anyone who has some more insight to the problem. It may be relevant to point out some common complaints I've heard in review comparisons. E.g.  "They are really really squeaky. " followed by suggestions to treat them with one product or another to remedy the problem. Personally I could care less about how squeaky my boots are when I'm riding but if I'd use a cleaner if it was safe. Silicones are generally safe and even beneficial to protect rubber and plastic but some products such as silicone sprays use solvents or aerosols that damage some plastics. I discovered this when I used a silicone spray on a rubber piece set in plastic. Overspray completely discolored and damaged the plastic. Fine print on the can warned against using on plastic. Oops. Lesson re-learned... 

I'm still interested to know what type of TPU predominates. I'd be more likely to safeguard them against certain chemicals but in the meantime the obvious precautions prevail: read the directions from the manufacturer which is usually something like, "clean with mild soap and water only", "not safe for use on plastics", "test on small area before application", etc. 

The good news for me is that all the boots I'm considering are considerably stiff soled and a verbatim recommended therapy for my type of injury. I'll have ample time to break them in if need be. 

 

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lots of variables at play. I suppose one could try to gather all the relevant information, but I suspect batches from a given company vary as well. As plastics become more and more diversified in their makeup and manufacture it will become more difficult. As you say, companies are experimenting, and economies are changing quick.

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I posted in that other thread. I have the 15 year old Sidi Crossfire. 

As I said in that thread, I've kept them clean over the years with toilet bowl cleaner, usually days after a ride and possible gasoline exposure. 

Toilet bowl cleaner. Gas. 15 years. Boots look new still.

That's all I have to add to this subject.

Edited by Turn,TheScrew

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I contact the US importer and distributor for Sidi, Paco Goebel regarding this issue. He didn’t know what type of TPU they use but offered to inquire with Sidi direct. Although Paco replied quickly to my email but did warn it may take some time to here from Sidi regarding such specific information. 

My new Crossfire 3’s arrived today. Ordered them a Thursday and on my doorstep five days later, from Holland! They’re great but I digress. 

In the technical manual’s instruction regarding care and use: “...use some silicone spray.” This surprised me because o have a fair amount of experience with Silicone lube or more specifically the siloxanes used for general purpose lubricants. Siloxanes such as dimethyl siloxanes are relatively inert and safe for polymer and rubber compounds. However, not all silicone aerosols are alike and in fact many general purpose “silicone” spray products that are available to consumers are not safe for use in plastic, rubber, and other polymers. Some even state this albeit in very fine print that few ever read. Silicone aerosols are commonly a mix of petrochemicals and some propellants that have have a profound and immediate undesired effect sometimes evident by an immediate discoloration and/or complete material decomposition not unlike the aforementioned pair of boots that fell apart. 

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