In case you missed it, a revealing study was conducted on SanFlickr Creative Commons/miggslives
Francisco’s BART (Bay Area Rapid Transit) system that tested the cleanliness of the seats on a BART rail car.  There have been complaints in the past about a cleanliness problem.  Some passengers take measures of standing up on the train just to avoid coming into contact with the seat cushion material.

The Bay Citizen commissioned Darleen Franklin, a supervisor at San Francisco State University’s biology lab, to analyze the bacterial content of a random BART seat.

Fecal and skin-borne bacteria resistant to antibiotics were found in a seat on a train headed from Daly City to Dublin/Pleasanton. Further testing on the skin-borne bacteria showed characteristics of methicillin-resistant staphylococcus aureus, or MRSA, the drug-resistant bacterium that causes potentially lethal infections, although Franklin cautioned that the MRSA findings were preliminary.

High concentrations of at least nine bacteria strains and several types of mold were found on the seat. Even after Franklin cleaned the cushion with an alcohol wipe, potentially harmful bacteria were found growing in the fabric.

Source: The Bay Citizen (

It’s Not Your Customer’s Fault

Can you say “Yuck!”  Apparently replacement cars are on the horizon.  It sounds like BART is considering a plastic-type seat and sacrificing comfort.  Why does the customer always get the hit when it comes to riding public transportation?  It even went as far as asking riders to use hand sanitizers….making it their problem:

“… encouraged riders to wash their hands and use hand sanitizers available at BART stations.”

Hygiene has emerged as a key issue as BART officials determine what kind of seats to install for a new fleet of cars in 2017. In January, system employees were invited to test a variety of seat models at a Hayward warehouse. One employee, Melissa Jordan, filed a report on BART’s website about the trade-offs in selecting the new seats.

“Can I live with some type of seat that’s less cushiony — maybe padded vinyl instead of fabric — if it’s easier to keep clean?” Jordan wrote.

Source: The Bay Citizen (

Alternative Seating For Comfort and Clean

The reality is, there are alternatives to seat materials that allow for both comfort AND cleanliness.  Rogers develops materials and seat cushions that do exactly that.

One of the issues facing the current BART seats is the polyurethane foam material under the upholstery.  While it is true that the upholstery itself should be of a bacteria-resistant non-woven material, the foam beneath must also not be a breeding ground for bacteria.  One solution to preventing bacteria growth is to build  cushions from open cell silicone foams!  There is a standard known as ASTM G 21:  Resistance of Synthetic Polymers to Fungi.  The test measures the growth of specific bacteria specimens and organism mixtures.  For those familiar with such bacteria, the ones observed are ATCC 9642, 11797, 6205, 9645, and 15233, with technical names such as aspergillus niger, penicillium funiculosum, and others.  The test uses a rating system from:

  • 0-4 where 0 is no trace
  • 1 is trace (<10%)
  • 2 is light (10-30%)
  • 3 is medium (30-60%)
  • 4 is  heavy (>60%).

Silicone foams for seating cushions receive ratings of either 0 or 1.  The problem with polyurethane materials filled with flame retardant agents (required for subway system passenger seating cushions) is that the fillers compromise the foam causing it to crumble over time and have large porous voids, which becomes a cesspool for bacteria and all kinds of spills.

The new BART specification for future builds already specifies silicone foam for all seats – however, why should the ridership have to to wait for the funding for those new build cars – when the seats could be changed out TODAY with refurbishments and replacements that use the silicone foam.

Besides resistance to bacteria growth, the silicone material is also resistant to fire spread and adheres to the smoke, and toxicity requirements of for subway passenger seating.

Finally, there is comfort.  A silicone foam will not deteriorate or change in its comfort-performing capabilities for a minimum of ten years!

Now BART has an answer to its problem.

Related Links about Rogers Silicone:

Video on Rail Car Seating 101:
Silicone Articles:
Silicone Materials:

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In catching up on some internet reading, I came across this press release from Frost and Sullivan that talked about Megatrends and how those trends are driving growth in key markets, particularly Chemicals and Materials.  Frost and Sullivan defined Megatrends as “global, sustained and  macroeconomic forces of  development  that impact business, economy, society, cultures and  personal lives, thereby defining our future world and its increasing  pace of change.”

At Rogers, we are committed as a company to innovation around three key Megatrends that directly relate to how our materials help make a better world.  Our three Megatrends are:  Internet Growth, Clean Technology and Mass Transit.

What was interesting was seeing the overlap with what Frost is saying with the direction we are seeing in our business:

“Megatrends will have a profound impact on the future direction of the chemicals and materials industry,” notes Frost & Sullivan  Industry Principal Brian Balmer. “For instance, the growth of mega  cities will stimulate growth for many chemical products such as glazing  with added acoustic insulation, and materials such as plastics and adhesives that enable the production of more compact home appliances.”

“Over the longer term, continued urbanisation in developed countries will result in demand for more materials that contribute to making  ‘healthier’ buildings…  Similarly, social trends, in particular for more environmentally  sustainable solutions, will be the single biggest factor affecting  future chemicals demand,” states Balmer.

“Products designed for modern and future lifestyles (‘GenerationY’) use a wide range of innovative chemicals,” remarks Balmer. “These  include structural materials such as engineering plastics for more  compact and more feature-packed convergent devices such as smartphones,  composite materials for lighter, stronger sports equipment and  eco-friendly materials for bio-sourced, recyclable, re-usable or  bio-degradable packaging.”

Product areas that will emerge at the forefront in future due to the impact of Megatrends range from nanomaterials, smart materials and  sustainable/renewable materials to organic electronics, biotechnology and carbon fibre and engineered natural fibres. Their growing presence will, in turn, have ramifications for several  chemicals.

Looking at our Megatrends, here’s what we see:

1. Internet Growth

As the internet continues to expand, mobile data traffic is expected to double every year through 2014, while Internet traffic will expand 46% annually. Demand for speed and bandwidth of network systems, and sales of smart phones, tablets, and mobile computers are expected to increase at double-digit rates.

Rogers is responding with:

  • Printed circuit materials critical to high speed performance of fast-growing wired and wireless 3G and 4G infrastructures
  • High performance foams to seal and protect top brands of popular smart phones, tablets, and notebook computers

2.  Clean Technology

Demand for clean technologies will grow rapidly over the next five years and beyond, with deployment of renewable energy and highly efficient technologies to reduce carbon emissions for the transport sector and for energy efficiency in buildings, industry and agriculture.  This trend is driving the need for specialty materials to enable new hybrid/electric vehicle technologies, improve motor efficiencies, and increase wind and solar energy performance.   Includes technologies in renewable energy (wind power, solar power, biomass, hydropower, biofuels), information technology, green transportation, electric motors, green chemistry, lighting, and many other appliances that are now more energy efficient.

Rogers is responding with:

  • Power electronic solutions for wind and solar power conversion over long distances
  • CleanTech materials to seal and protect batteries in hybrid electric and electric vehicles

3.  Mass Transit Expansion

Increasing urbanization and steady growth in urban populations worldwide, combined with the drive for sustainability, is driving demand for Mass Transit solutions (rail, aircraft, bus, and others) worldwide. Railways in India and China are expanding at a rapid pace. New components are in constant demand, and complexities of Mass Transit require innovative, high-reliability products and materials to ensure passenger safety.

Rogers is responding with:

  • Power electronic components and thermal insulation for power conversion in rail propulsion systems
  • Robust seating, sealing, and vibration isolation cushioning that meet stringent requirements for long life and passenger safety

And while it’s good to be on the forefront of trends, Rogers continues to be committed to evolving our materials to better serve the needs of our customers.  We work hard to stay close to understanding the needs of the design engineers who reach out for help.  Let us know how we can better serve you.  We’re here to assist.

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This post written by David Sherman originally appeared on Rogers PORON Cushioning Blog.

You’ve probably heard quite a bit about concussions in the news lately.  In recognition of Brain Injury Awareness month, which takes place in March, the Brain Injury Association of America (BIAA) is launching a nation-wide campaign to ensure coaches of school athletic teams and extracurricular athletic activities are trained to recognize the signs and symptoms of concussions.

All of us at Rogers are excited to see that proper attention is finally being brought to the causes and effects of brain and impact injuries.  Extreme impact protection is the very reason we developed our PORON XRD technology, which is not only used in helmets, but also in compression garments, elbow and knee pads, and protective footwear.

As we travel around to trade shows all over the world, we are consistently asked how PORON XRD Material works.  How can such soft, flexible and breathable foam protect against something like a baseball flying at 100mh?  It all has to do with a short lesson in physics 101 and strain rate dependant materials.

Strain rate dependent materials are used in a variety of protective applications mentioned above.  They are useful in these applications because of their unique ability to adapt to the applied impact.  At low strain rates the material feels soft and contours to the body.  While at high strain rates the material instantaneously stiffens to absorb the impact and then returns to its original ‘resting’ state.

For those who want more technical information….

PORON XRD Material gets its softness when at rest or simply being worn, by being above the glass transition temperature (Tg) of the urethane molecules.  (Glass transition temperatures are similar to a melting point – for those who are not the foam geeks that we are.)

When stressed at a high rate or impacted quickly, the glass transition temperature of the material goes up to the point where the urethane momentarily “freezes.”  (Think of water freezing into ice.)  Many materials have glass transition temperatures, which is why strain rates are always specified in material testing.

When impacted, it is the firming of the material that allows PORON XRD Material to instantly form a comfortable, protective shell around the wearer.  Unlike many other materials which often maintain their “frozen” state, PORON XRD Protection immediately returns to its soft, flexible and contouring state.

For a more visual example, think of diving into water at a low height versus a higher height.  At low heights, jumping into water feels very soft and helps cushion the dive.  But at high heights (i.e. jumping from a bridge) the water feels like frozen ice.  This is due to the speed at which the person is entering the water.

Another example is to envision removing a Band-Aid™.   If you remove a Band-Aid ™ slowly, the

adhesive sticks to the surface, but if you remove it quickly, the adhesive freezes and sticks less.

PORON XRD Material was engineered to react very quickly in various impact situations.  For example, PORON XRD Technology is effective at absorbing not only smaller, repeated impacts (such as nudging players during a basketball game) but it is also effective at absorbing larger impacts (such as in a ballistic vest applications).  Rogers’ ability to manipulate the PORON XRD chemistry makes this unique material soft and flexible at rest or when it’s wrapped around your body, but instantly absorbs energy upon impact.

If you would like more information on all the various testing methods that we have conducted on PORON XRD Materials, we have plenty to share!  Just give us a comment below.

Please come back and visit us!  We will be posting some interesting news over the next several weeks in collaboration with our PORON XRD partners in recognition of Brain Injury Awareness Month.   As always, we would love to hear your questions and comments/views you may have on our products as well as how brain injuries/concussions are treated among team sports.

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In a recent article on, Boeing announced that it was shifting to plastic composites for its 787 Dreamliner floor beams.  It’s well-known that the airline has had trouble getting this aircraft to market starting with being three years late. But it hasn’t stopped them in finding new, innovative ways to reduce its carbon footprint and drive sustainability into their design decisions:

The Boeing 787 Dreamliner is a long-range airliner that seats 210 to 330 passengers. As a result of a fuselage and wings made primarily of carbon composites, the Dreamliner consumes 20 percent less fuel than the Boeing 767, which has similar seating capacity.

TAL Manufacturing Solutions of India reports that Boeing changed the design for floor beams in the Dreamliner 787 from titanium to a composite plastic structure….the floors will be made from materials that are similar to the materials used in the body of the Dreamliner… The beams will be used for flooring located between passenger and luggage compartments.

In talking with Ken Kozicki from our BISCO Silicones Division, he elaborated on the considerations that are made when choosing materials for aircraft flooring.  He also shared how silicone foam can act as a barrier in between the floor beams and help reduce the vibration and overall noise from engines.  And we all know any reduction in noise when flying is MOST appreciated!  Here’s what Ken said:

Dynamic flooring designs and structures have a few purposes – but can be concentrated into three general categories:

  • Minimize vibration and acoustic noise generation
  • Propagation or “modularize” the floor into segments that can be fabricated and layered prior to final assembly,
  • Shrink the thickness of the profile of the entire floor allowing for increased head room in a rail car or aircraft.

With each of these objectives, the selection of the viscoelastic materials used for the vibration isolation and damping pads is critical.  The performance of the floor is dependent on the material’s physical characteristics such as the stiffness to support maximum loads and the damping coefficient to balance the amount of vibration energy that is isolated versus dissipated.  In addition, especially in the aircraft and rail markets, the materials need to comply to the very stringent flame, smoke, and toxicity standards.

Lastly, something that is often times overlooked is the change in performance of the material over time.  In reference to foams, it is important to consider compression set and stress relaxation.

Compression set is the amount of reduction in thickness the foam will permanently experience over time.  Stress relaxation is how much “springback force” does the material lose over time.  If a solid material is chosen for the pads, other factors such as brittleness and performance capabilities over the required temperature range will be key.

BISCO silicones are a great choice to accommodate all of these conditions.  Noise is generated from two major sources:

1.  The first is the transfer of structure-borne vibration to a propagating sound wave.  Reducing vibration ultimately reduces noise.

2.  The second noise source is propagating sound waves from outside or beneath the flooring structure, such as jet engine noise transferring into the fuselage or rail wheels moving along the tracks.  Sound barrier materials can be laminated to the dynamic flooring structure to block the waves from propagating.  Again, choosing silicone sound barriers is an imperative, especially if a standard such as FAR 25.856 is required.

Can you hear me now?

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This post authored by John Coonrod originally appeared on the Rog-Blog hosted by Microwave Journal

Digital circuit design once had less demands. When clock speeds were 100 MHz or less, signal loss wasn’t an issue. Digital circuits, in fact, have long been designed to be more tolerant of signal level variations than analog circuits. But with digital circuits continuing to increase in speed, they are assuming more of the characteristics of analog microwave signals, and requiring more attention to design detail and even choice of PCB material as in the case of high-frequency analog circuits.

When 100 MHz was considered fast, the choice of a low-cost laminate like FR-4 was a sound decision. If anything, the performance provided by an epoxy-based circuit-board material like FR-4 was often better than necessary for most digital circuit designs. In early digital circuits operating at 100 MHz or less, it was important for a PCB material to provide a consistent relative dielectric constant across the material in order to maintain circuit traces with consistent impedance and maintain even timing of digital signals across the circuit. In an analog/microwave circuit, consistent impedance is also important, since impedance mismatches can cause unwanted signal reflections and shifts in signal phase and frequency.

But times have changed and now digital signals travel at microwave speeds. The same design guidelines and choices in PCB materials used for lower-speed digital circuits can’t be applied at higher operating speeds without penalties, such as timing problems, signal crosstalk, and even electromagnetic-interference (EMI) problems. High-speed signals more and more resemble the fast pulses of microwave radar systems, and designers of high-speed digital circuits must think more like microwave circuit engineers to create successful designs.

Digital circuit designers have come to learn what microwave circuit designers have known for years: the choice of PCB material can have a great impact on the performance of high-speed digital circuits as well as analog microwave circuits. Digital circuit designers once paid little attention to the loss of a PCB, since that material characteristic had little effect on digital functionality at lower speeds. But analog microwave systems, such as receivers, depend on signal strength, and any loss in a system or its components, including the PCB material, must be minimized. For that reason, microwave circuit designers have paid attention to a laminate’s dissipation factor, choosing materials with low values corresponding to low loss. As digital circuits move to multi-GHz speeds, loss can also be a concern, especially for its effect on digital signal integrity.

Losses in a high-speed or high-frequency PCB can stem from a number of sources, including dielectric losses (especially above about 3 GHz), conductor losses, ground-plane losses, and even losses attributed to the surface roughness of a PCB’s conductive metal used to form signal and power traces. The performance of a high-speed digital PCB can also be affected by crosstalk between signal traces on one layer of the PCB or between layers of a multilayer PCB, by noise from the power and ground planes due to inadequate decoupling, and by external radiated and conducted noise sources. High-speed digital circuit designers must also control levels of EMI to meet global regulatory requirements.

Microwave circuits may never match the complexity of high-speed digital circuits in terms of number of layers in a multilayer PCB assembly, but there are a number of parallels that can be drawn between the two circuit technologies. In fact, it is not unusual to find both types of circuit on one multilayer- circuit construction. Both benefit from PCB materials with typical low values of relative dielectric constant that are also consistent across a substrate and with frequency. Both circuit approaches can benefit from materials with low dissipation factor for low loss, which translates into good signal integrity in a high-speed digital circuit and low insertion loss in an analog microwave circuit.

Relative dielectric constant is only one of many different PCB material parameters, but it can be used as a starting point when considering laminate choices for a high-speed digital circuit design. Ideally, a PCB material for high-speed digital circuits would have isotropic dielectric constant characteristics—that is, with dielectric constant values that are about the same in the x, y, and z directions of the material. Another benefit would be to have the dielectric constant remain within a narrow range of values across a wide frequency range. Not only would this support broadband microwave use, but would ensure excellent signal integrity in high-speed digital circuits.

Unfortunately, most PCB materials are anisotropic in their relative dielectric constant values, with different values in each direction. And most exhibit dielectric constants that decrease with increasing frequency. For high-performance digital as well as microwave circuits, it can be helpful to select PCB materials that are as closely matched in relatively dielectric constant in all three axes, and with dielectric constant that is fairly consistent with frequency. For an increase in dielectric constant, the impedance of a circuit trace or transmission line will decrease and the speed of a wave through the trace or line will slow. In a digital circuit, a material with dielectric constant that significantly decreases with frequency can cause digital signal edges to reflect more at higher frequencies than at lower frequencies, causing timing problems. The problem can be minimized by selecting a PCB material with relative dielectric constant that is as flat as possible with frequency (low dispersion).  The chart in figure 1 displays dispersion when measured using a stripline transmission line.  Typically stripline transmission lines are considered a non-dispersive medium so what effect is shown with dielectric constant in relation to frequency is likely material dispersion.

One other material parameter that is worth noting in selecting substrates for high-speed digital circuits is the coefficient of thermal expansion (CTE) in the z-axis (through the thickness) of a laminate. This parameter is one indicator of the expected reliability of plated through holes (PTHs), which are plated vias used to make signal, power, and ground connections between the different layers in a multilayer PCB.

A low-dielectric-constant PCB material can support good performance in high-speed digital circuits, but it must also be a material that is compatible with the processing steps used to fabricate the multilayer circuits typical of digital designs. As an example, Theta™ circuit materials from Rogers Corporation are low-loss, low-dielectric-constant materials with excellent thermal and mechanical properties for high-layer-count circuit boards. They maintain dielectric constant within a fairly narrow window with frequency, with z-axis values of 3.90 at 1 GHz and 4.01 at 10 GHz. Theta materials also have a z-axis CTE (about 50 ppm/°C) that is approximately 30% lower than that of FR-4, and more closely matched to that of copper, for highly reliable PTHs in multilayer circuits. These materials are halogen free and compatible with lead-free soldering processes. They have the mechanical traits needed for multilayer digital designs, but also the excellent electrical characteristics suitable for both microwave and high-speed digital circuits or, in fact, both types of circuits within the same multilayer PCB.

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