Den kemiska pappersmassan tillverkas genom att man kemiskt, vid hög temperatur, bryter ner och löser ut vissa komponenter ur veden, speciellt lignin, och fibrerna frigörs härigenom från varandra med minimal mekanisk insats. Kemisk massa har låg ligninhalt och består till största delen av cellulosa och hemicellulosa. Utbytet för kemiska massor är oftast under 55%, under 50% för massor som bleks.[1]

Den mekaniska pappersmassan tillverkas genom mekanisk separering av fibrerna med hjälp av så kallade raffinörer (och fortfarande till viss del med hjälp av slipstenar för slipmassaframställning). En huvudprodukt bland de mekaniska massorna är termomekanisk massa (TMP, thermomechanical pulp) för tidningspappersframställning. Genom viss kemisk förbehandling av veden kan andra egenskaper erhållas än för rent mekaniska massor och man inkluderar kemimekaniska massor (CTMP, chemi-thermomechanical pulp) i gruppen mekaniska massor. Mekaniska massor innehåller i princip alla vedens beståndsdelar (med mindre kemisk modifiering) varför utbytet blir högt, oftast över 90%.

Pappersmassa är den huvudråvara som används vid pappersframställning. Pappersmassa framställs idag främst av trävirke, så kallad massaved. (Returpapper har kommit att spela en allt större roll som råvara för papperstillverkning, men man måste härvid skilja mellan pappersmassa (färskmassa) respektive returfiber. Färskmassa är en nödvändighet för ett antal pappersprodukter, men också nödvändigt för att förse marknaden med tillräckligt med fiber för returfiberåtervinningen.) För vissa specialpapper som till exempel sedelpapper och tepåsepapper används annan typ av växtråvara såsom bomulls- och linnefiber respektive abacafiber och processerna för hantering av dessa råvaror skiljer sig mycket från normal massatillverkning.

Papper och massawikipedia

The wheel bearings in your car work a lot in the same way. Sure, they’re not quite as fun to play with, but they serve a valuable function keeping your vehicle safe and on the road.

Like those at any of our Utah auto repair shops, seasoned mechanics know to look for several different indicators that wheel bearings are the issue. One tell-tale sign is a whirring or grinding noise coming from the wheel area. That grinding sound comes when the ball bearings move over tiny pits or divots in the bearing race. The baffling part of listening for this sound is that sometimes you can only hear it at certain speeds or in particular conditions. One thing to note, though, is if it sounds like a “click” instead of a “whirr,” it’s likely a problem with something other than the wheel bearing.

Wheel bearings connect your vehicle’s wheels to the axle and reduce friction when the wheel turns so that you can drive smoothly. Your vehicle’s entire weight rests on the wheel bearings, so it’s safe to say that they take a lot of abuse – especially if you are prone to hitting potholes and curbs.

Since wheel bearings are not something people talk about very much, it can be hard to diagnose them as the cause of your vehicle’s problems. Not only that, but given the location of the wheel bearings, sometimes the grinding noise can travel and sound like it’s coming out of the engine. Additionally, once your vehicle is up on a lift, the damaged part of the wheel bearing will often move to the top, so you don’t hear the noise unless you make it do several fast rotations.

Pappersmassa framställs industriellt i stor skala i massa- och pappersindustri. Pappersmassans egenskaper beror på tillverkningsmetod, men massan består alltid av separerade fibrer eller fiberdelar, som kan bilda ett nätverk med hjälp av vätebindningar mellan fibrerna i papperet. Man skiljer mellan mekaniska massor med högt utbyte, halvkemiska massor, kemiska massor (oblekta eller blekta) och dissolvingmassor med lägst utbyte.

Att göra papper från träfibrer utvecklades under mitten av 1800-talet för att möta den ökade efterfrågan på papper. Tidigare användes textillump och fiber från lin och en del andra långfibriga växter. Begränsad tillgång på dessa råvaror ledde till experiment med att utnyttja vedfibrer.

Wheel bearings come in two basic configurations: angular and conrad. The angular type has ball bearings nestled between an angular holding piece and another piece – all situated inside of a collar. As a general rule, angular wheel bearings can handle bigger thrusts or shocks than conrad-styles because the bearings function on an angle. The conrad type has an inner circle with ball bearings sitting in between an outer circle, so it handles situations better than those that only have vertical shocks. Both types are sealed to maintain lubrication and keep out dust and other debris.

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Do you remember a few years ago when “fidget spinners” were all the rage? Those neat little toys seemed to spin endlessly and effortlessly between your fingers, making them fun to move around and do tricks with. You may not realize it, but fidget spinners and the wheel bearings in your car have a lot in common.

Engine failure, especially out of the blue, can be scary. It can put a wrench in your plans if driving somewhere important and depending on the problem, can be expensive to fix. Thankfully, there are lots of warning signs that can signal you when your engine is about to fail.

Invest in high-quality aftermarket parts if you need to replace the wheel bearing. Poor quality wheel bearings are likely to break or negatively impact your wheels, brakes, or general drivability. Wheel bearings work well for an average of 100,000 miles.

Runt år 1840 utvecklade tysken Friedrich Gottlob Keller slipprocessen, där ved slipas mot stora slipstenar, varvid vedfibrerna mekaniskt frigörs från veden. Denna tillverkningsmetod resulterar i det som idag kallas för mekanisk pappersmassa.

År 1913 fanns i Sverige 168 fabriker för tillverkning av pappersmassa och 73 fabriker för tillverkning av papp och papper. Den kemiska massan var vid denna tid omkring dubbelt så dyr som den mekaniska massan.[2]

When your vehicle is functioning properly, it’s easy to forget how dangerous driving can be. However, it only takes a moment for an important component to malfunction. Suddenly your car has your full attention. One of the worst situations to find yourself in as a driver is to press the brake pedal only to realize that it is not working.

Additionally, your steering wheel may also vibrate, which is always unnerving. Damaged wheel bearings can also mess with your braking system, making it imperative that you take your vehicle into a mechanic when you first suspect a problem.

As mentioned above, the way sound travels can make it difficult to pinpoint which wheel has a damaged bearing, so many technicians will suggest replacing multiple wheel bearings at once. This may seem like an unnecessary expense, but it is a way to ensure that the technician is completely correcting the problem.

Another sign of a damaged wheel bearing is feeling like your wheels have a mind of their own. Your vehicle shouldn’t pull one way over another, and they shouldn’t feel wobbly at all, so if you feel like you’re fighting to keep your wheels on center, the wheel bearing could be the issue. This looseness can also cause uneven wear on your tires, which any of our Utah tire stores can help diagnose.

Have you noticed an increase in flat tires during the frigid winter months? There’s a reason for it. Keep reading for some simple explanations as to why tires seem to go flat when temperatures drop.

There are a lot of moving parts in between you at the wheel bearings, so it isn’t easy to replace yourself. Unless you have a lift and a lot of know-how, you’re probably best off taking it to a mechanic. If you suspect that wheel bearings may be a problem for you, bring your vehicle into our Bountiful tire shop or any of our shops along the Wasatch Front to have one of our skilled mechanics take a look.

The tiny little balls in between the center bearing and the outer bearing race reduce a lot of the friction that would normally be generated with that kind of motion, so the fidget spinner spins on and on and on…and on (much to every parent and elementary teacher’s chagrin).

If you begin to notice some electrical problems in your vehicle, such as the dome light failing to turn on when you open the doors or the radio shutting off, you may need to check the fuses.

It all boils down to basic physics. Balls generate less friction when they roll across a surface (as evidenced when you give a book and a ball a push on the same surface – the ball will definitely go farther because there is less friction). In a fidget spinner, you hold the center ball bearing between your fingers to keep it still, and then you spin the outer ring (called a bearing race) either by flicking your wrist or the little protruding knobs.

The outer tie rod ends are one of the more important parts of your vehicle’s steering system. While you may not choose to replace the outer tie rod ends yourself, it is good to be able to recognize what they are and see if they need replacing.

Your car is what gets you where you need to go on time and in one piece, so when it starts making strange noises or pulling from side to side, it can feel very unsafe. Your vehicle’s wheel bearings play a pretty significant role in how your car functions, so it’s worth knowing what they are and how they work.

Från 1850 utfördes experiment med att behandla vedflis eller sågspån med kemikalier under förhöjt tryck vid temperaturer mellan 140 och 170 °C bland annat av amerikanen Benjamin Chew Tilghman, svensken Carl Daniel Ekman och den tyske kemisten Alexander Mitscherlich gällande den sura sulfitprocessen, av amerikanerna Hugh Burgess och Charles Watt gällande den alkaliska s.k. sodaprocessen (egentligen med natriumhydroxid som aktiv kemikalie) och av tysken Carl F. Dahl gällande den alkaliska sulfatprocessen. Detta ledde till att olika kemiska processer kunde användas för att tillverka pappersmassa med låga ligninhalter, vilket gav starkare papper.